Thèses : « Jet engines ; Jet propulsion »

1

Sivapragasam, M. « Numerical and experimental investigations on multiple air jets in counterflow for generating aircraft gas turbine engine inlet flow distortion patterns ». Thesis, Coventry University, 2014. http://curve.coventry.ac.uk/open/items/0ad1d0c2-6693-4c6e-9224-5a2237862074/1.

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The performance of an aircraft gas turbine engine is adversely affected by the non-uniform or distorted flow in the inlet duct. Inlet flow distortion lowers the surge margin of the engine‟s compression system with surge occurring at much lower pressure ratios at all engine speeds. The compressor and/or engine are subjected to ground tests in the presence of inlet distortion to evaluate its performance. The simplest method of simulating inlet distortion during these tests is by installing a distortion screen ahead of the engine on the test bed. The uniform inlet flow to the compressor becomes nonuniform with total pressure loss after passing through the distortion screen. Though the distortion screens offer a number of significant advantages, they have some disadvantages. The air jet distortion system can alleviate many of the operational disadvantages encountered with the conventional distortion screens. The system consists of a number of air jets arranged in a circumferential array in a plane and issuing opposite to the primary air flow entering the engine. The jets interact with the primary stream and cause a local total pressure loss due to momentum exchange. The individual mass flow rates from the jets can be varied to obtain a required total pressure pattern ahead of the compressor at the Aerodynamic Interface Plane (AIP). A systematic study of the flow field of confined, turbulent, incompressible, axisymmetric jet issuing into counterflow is covered in this research programme. The jet penetration length and the jet width are reduced compared to unconfined counterflow and a linear relationship between the velocity ratio and the jet length ceases to be valid. The flow field of a circular compressible turbulent jet and then a system of four jets arranged circumferentially and issuing into a confined counterflow was studied experimentally and numerically. For the four jet system the mass flow rates in the four jets were equal in the first part of the study and in the second part they were unequal. The loss in total pressure due to the jet(s) interacting with the counterflow was quantified by a total pressure loss parameter λp0. The total pressure loss increased with increasing mass flow ratio. The total pressure loss distribution was evaluated at several locations behind the jet injector(s). The total pressure non-uniformity quantified by Distortion Index (DI) was found to be highest at a location just downstream of the jet injector and at far downstream locations low values of DI were observed. From the understanding gained with a single jet and four jets in counterflow a methodology was developed to generate a given total pressure distortion pattern at the AIP. The methodology employs computations to obtain the total pressure distortion at the AIP with quasi-one-dimensional inviscid analysis used as a starting point to estimate the mass flow rate in the jets. The inviscid analysis also provides a direction to the iterative procedure to vary the mass flow rate in the jets at the end of each computational step. The methodology is demonstrated to generate a given total pressure distortion pattern using four jets and is further extended to a larger number of jets, twelve and later twenty jets. The total pressure distortion patterns typical of use in aircraft gas turbine engine testing are generated accurately with a smaller number of jets than reported in the literature.

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Erickson, Robert R. « A numerical investigation on the influence of engine shape and mixing processes on wave engine performance ». Available online, Georgia Institute of Technology, 2005, 2004. http://etd.gatech.edu/theses/available/etd-01032005-100101/unrestricted/erickson%5Frobert%5Fr%5F200505%5Fphd.pdf.

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Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2005.
Ben T. Zinn, Committee Chair ; Jeff Jagoda, Committee Member ; Suresh Menon, Committee Member ; Tim Lieuwen, Committee Member ; Rick Gaeta, Committee Member. Vita. Includes bibliographical references.

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3

Rodrigo, Clinton. « Basic Comparison of Three Aircraft Concepts : Classic Jet Propulsion, Turbo-Electric Propulsion and Turbo-Hydraulic Propulsion ». Master's thesis, Aircraft Design and Systems Group (AERO), Department of Automotive and Aeronautical Engineering, Hamburg University of Applied Sciences, 2019. http://d-nb.info/1204558019.

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Purpose - This thesis presents a comparison of aircraft design concepts to identify the superior propulsion system model among turbo-hydraulic, turbo-electric and classic jet propulsion with respect to Direct Operating Costs (DOC), environmental impact and fuel burn. --- Approach - A simple aircraft model was designed based on the Top-Level Aircraft Requirements of the Airbus A320 passenger aircraft, and novel engine concepts were integrated to establish new models. Numerous types of propulsion system configurations were created by varying the type of gas turbine engine and number of propulsors. --- Findings - After an elaborate comparison of the aforementioned concepts, the all turbo-hydraulic propulsion system is found to be superior to the all turbo-electric propulsion system. A new propulsion system concept was developed by combining the thrust of a turbofan engine and utilizing the power produced by the turbo-hydraulic propulsion system that is delivered via propellers. The new partial turbo-hydraulic propulsion concept in which 20% of the total cruise power is coming from the (hydraulic driven) propellers is even more efficient than an all turbo-hydraulic concept in terms of DOC, environmental impact and fuel burn. --- Research Limitations - The aircraft were modelled with a spreadsheet based on handbook methods and relevant statistics. The investigation was done only for one type of reference aircraft and one route. A detailed analysis with a greater number of reference aircraft and types of routes could lead to other results. --- Practical Implications - With the provided spreadsheet, the DOC and environmental impact can be approximated for any commercial reference aircraft combined with the aforementioned propulsion system concepts. --- Social Implications - Based on the results of this thesis, the public will be able to discuss the demerits of otherwise highly lauded electric propulsion concepts. --- Value - To evaluate the viability of the hydraulic propulsion systems for passenger aircraft using simple mass models and aircraft design concept.

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Chaudhry, Udey. « Tip leakage flow, heat transfer and blade lifting in a jet engine turbine ». Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/94499.

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An existing Navier-Stokes code (MEFP) was used to calculate developing flow and heat transfer in turbine tip gaps. Successful calculations of the heat transfer to a model turbine blade tip were obtained with a Prandtl mixing length turbulence model. The calculations revealed details of the flow development including recirculation and reattachment on the blade tip surface. The calculated heat transfer distributions were in good agreement with experimental data. A combined solution of the energy equation in the tip gap flow and in the rotor blade tip gave tip temperature distributions. An independent computational study, using the same numerics as MEFP but a separate new computer program, was also performed to investigate the numerical accuracy of heat transfer calculations for fully developed flow. A literature survey of gas turbine blade materials and factors influencing turbine tip blade life was performed. Approximate temperature ranges for the significant blade life reduction mechanisms, hot corrosion, oxidation, and melting were determined. calculations for typical jet engine conditions, In the present a maximum tip temperature of 1488 K was predicted which would lead to high oxidation rates for present day turbine blade alloys.
M.S.

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Krolak, Matthew Joseph. « Optimization of a magnetoplasmadynamic arc thruster ». Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-042607-155701/.

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Weyer, Robert Bernhard. « Investigation of the functioning of a liquefied-gas micro-satellite propulsion system ». Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/49765.

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Thesis (MScEng)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: The focus of this thesis is on the investigation of the functioning of a liquefied-gas thruster. Such a thruster could be used to provide secondary propulsion to a microsatellite in orbit. A general overview of the need for thrusters in micro-satellites is put forward in the introduction. Motivation for deciding to investigate a liquefied-gas system is presented. Recent developments in the field of micro-satellites are discussed as well as their relevance to the project undertaken. Fundamental background theory relevant to the engineering problems associated with the development and analysis of such a system is also presented. Computer programs were written to simulate such a liquefied-gas thruster system. The experimental work carried out to analyse the system from a practical view-point is documented. Attention is also given to the measurement and calibration techniques used to obtain experimental data. One-dimensional fully explicit transient mathematical models of the thruster system were developed to model the system using both compressed air and butane as propellants. These models were incorporated into computer programs used to simulate the transient behaviour of the system. Although it is intended to use butane as the propellant onboard a satellite, the reason for modelling and simulating a system using compressed air is because air is a convenient fluid to work with from both a theoretical and practical point of view. An experimental model of a thruster system was designed, built and tested using air and butane as propellants. Most of the model was built using perspex to allow for the observation of the two-phase behaviour of the propellant inside the system. Locally purchased components were used for the solenoid and fill valves. Readily available butane lighter fluid was used for butane testing. Self-made heating elements were used to provide heat input to the propellant. Testing was done at different back pressures ranging from 100 kPa down to 20 kPa in a vacuum chamber. Good comparison between theoretical and experimental results was obtained for air. Theoretical results for peak thrusts tended to over predict experimental results by approximately 15 % for a system exhausting to a pressure of 100 kPa. Peak thrusts as high as 0.2 N were obtained for vacuum tests conducted at an absolute pressure of 20 kPa. Peak thrusts of approximately 50 mN were achieved for experimental testing III atmospheric conditions using butane with a starting pressure of between 270 and 290 kPa. Typical average thrusts of between 20 mN and 30 mN were noted for butane testing with initial pressure of between 200 to 300 kPa. Peak thrusts of over 0.1 N were observed for vacuum testing at an absolute pressure of 20 kPa. An equation to correlate the experimentally determined average thrust as a function of pulse duration and starting pressure was developed. This correlated most of the experimental data to within ±25 %. Theoretical results for butane testing are able to predict peak thrusts within approximately 20 % for starting pressures in the range of 200 to 300 kPa. Since the project was an exploratory investigation into a liquefied-gas thruster, some additional aspects relating to such systems were also given attention. The effect of liquid propellant motion or sloshing was considered and recommendations regarding the design and placement of the propellant tanks were made. The use of heat pipes as an alternative to electrical heating elements was investigated and some elementary design aspects are presented graphically. The management of the liquid propellant using surface tension devices was examined qualitatively. Recommendations relating to future projects in the field of simple, low-cost propulsion systems for micro-satellites are put forward. More specifically these recommendations are with regard to: thermo-fluid modelling of the propellant, future experimental work to be done, techniques to measure small thrusts and vacuum chamber testing.
AFRIKAANSE OPSOMMING: Die tesis ondersoek die funksionering van 'n vervloeidegas stuwer. So 'n stuwer kan gebruik word om sekondêre aandrywing aan 'n mikro-satelliet in 'n wentelbaan te verskaf. 'n Algemene oorsig oor die behoeftes van stuwers vir mikro-satelliete word voortgesit in die inleiding. Redes vir die gebruik van 'n vervloeidegas stuwer word bespreek. Onlangse ontwikkelinge in die veld van mikro-satelliet aandrywing word bespreek asook die toepaslikheid daarvan. Fundamentele teoretiese agtergrond verbonde aan die ontwikkeling en analise van so 'n stuwer stelsel word ook gegee. Rekenaarprogramme is geskryf om die gedrag van so 'n stuwer stelsel te simuleer. Eksperimentele werk is gedoen om die stelsel vanuit 'n praktiese oogpunt te analiseer. Aandag word ook gegee aan die metings- en kalibrasietegnieke soos toegepas vir die eksperimentele werk. Eendimensionele volle eksplisiete wiskundige modelle is ontwikkelom die oorgangsgedrag van die stuwer-stelsel te simuleer met beide lug en butaan as dryfmiddel. Hierdie modelle is geïnkorporeer in die rekenaar programme om die stuwer stelsel te simuleer. Alhoewel dit beoog word om butaan as die dryfmiddel aan boord die satelliet te gebruik, is lug ook gebruik vir simulasie weens sy gerieflikheid as 'n vloeier uit beide 'n teoretiese en 'n praktiese oogpunt. 'n Eksperimentele model van die stuwer stelsel is ontwerp, gebou en getoets met beide lug en butaan as dryfmiddels. Die model is hoofsaaklik uit perspex gebou sodat die twee-fase gedrag van die butaan uitgebeeld kon word. Vrylik beskikbare butaan aansteker vloeistof IS gebruik VIr butaan toetsing. Selfvervaardigde verhittingselemente is gebruik om hitte aan die dryfmiddel te verskaf. Toetse is gedoen deur verskeie omgewingsdrukke varieërend van 100 kPa af tot 20 kPa in 'n vakuumtenk te gebruik. Goeie ooreenstemming tussen die teoretiese en eksperimentele resultate vir die toetsing van lug is verkry. Die teoretiese resultate neig om die piek stukrag 15 % hoër te voorspel as die eksperimentele resultate vir 'n stelsel wat tot 'n omgewingsdruk van 100 kPa by die uitlaat. Piek stukragte van meer as 0.2 N is gekry vir vakuum toetse wat gedoen is by 'n omgewingsdruk van 20 kPa. Tydens eksperimentele toetsing met butaan teen 'n aanvanklike druk tussen 270 en 290 kPa, in atmosferiese toestande, is piek stukragte van ongeveer 50 mN behaal. Tipiese gemiddelde stukragte van tussen 20 en 30 mN is waargeneem vir butaan toetsing teen 'n aanvanklike druk tussen 200 en 300 kPa. Piek stukragte van meer as 0.1 N is behaal vir vakuum toetse met 'n absolute druk van 20 kPa. 'n Vergelyking om die gemiddelde stukrag, wat eksperimenteel bepaal is, as 'n funksie van puls tydsduur en aanvanklike druk te korreleer, is ontwikkel. Die meeste eksperimentele data se afwyking van die korrelasie-vergelyking was minder as 25 %. Teoretiese resultate vir butaantoetse het piek stukragte binne 20 % van die eksperimenteel metings korrek voorspel vir aanvanklike drukke tussen 200 tot 300 kPa. Weens die feit dat die projek 'n oorhoofse ondersoek in In vervloeidegas stuwer behels, is aandag ook gegee aan addisionele aspekte wat verband hou met sulke stelsels. Die effek van die vloeistof-dryfmiddel se onstabiele beweging in sy tenke is in ag geneem en voorstelle vir die ontwerp en plasing van die dryfmiddel tenke is gemaak. Die gebruik van hitte pype as 'n alternatief vir elektriese verhittingselemente is ondersoek. Verskeie ontwerp aspekte word grafies voorgestel. Die bestuur van die vloeistof-dryfmiddel deur van oppervlak spannings apparaat gebruik te maak, is kwalitatief ondersoek. Voorstelle vir verdere navorsing in die veld van eenvoudige, lae-koste stuwer stelsels vir mikro-satelliete is gemaak. Meer spesifiek is hierdie voorstelle gerig op die termo-vloeidinamiese modellering van die dryfmiddel, verdere eksperimentele navorsing, tegnieke om klein stukragte te meet en vakuumtenk toetse.

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Jouot, Fabien. « Etude de la détonation dans un jet diphasique cryogénique GH2-LOx : contribution aux études sur les moteurs à onde de détonation ». Thesis, Orléans, 2009. http://www.theses.fr/2009ORLE2055/document.

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L’objectif de cette thèse est d’étudier l’initiation directe et la propagation d’une détonation dans un milieu cryogénique diphasique GH2-LOx dans le cadre général des moteurs à onde de détonation pour la propulsion spatiale. Un rappel des bases théoriques sur les processus d’atomisation d’un jet liquide, puis sur la détonation en phase gazeuse, et enfin sur la détonation dans un mélange diphasique, constituent le premier chapitre de la thèse. Le deuxième chapitre présente les dispositifs expérimentaux et les techniques utilisés pour mener à bien les expériences de caractérisation du jet diphasique et d’étude de la détonation. Le troisième chapitre est consacré à l’étude dans un tube en quartz de la granulométrie d’un jet diphasique GHe-LOx non réactif. Une cartographie est ainsi réalisée sur l’ensemble du tube, pour différents débits d’injection. Ces résultats sont corroborés par une étude théorique sur une goutte isolée et par une étude numérique sur le comportement du jet en champ proche de l’injecteur. Le quatrième chapitre présente les résultats de l’étude de la détonation dans un tube en acier d’un mélange réactif GH2-LOx. La détonation est étudiée en fonction de divers paramètres : énergie d’initiation stockée, emplacement du dispositif d’initiation par étincelle, richesse globale du mélange. La célérité et la pression de détonation, ainsi que la structure tridimensionnelle de la détonation, sont les principales informations recueillies pour l’étude du phénomène de détonation en mélange diphasique. Une étude théorique des caractéristiques de la détonation apporte des éclairages supplémentaires sur la détonation à très basse température (100 K)
Within the general framework of detonation engines for space propulsion purpose, this work aims to study direct initiation and propagation of detonation in a cryogenic twophase GH2-LO2 mixture. First chapter is constituted by theoretical basis and state of art on atomization processes in liquid jets, then on gas-phase detonation, and finally on two-phase detonation. Second chapter describes experimental set-up and associate techniques in order to carry out two-phase jet characterization and detonation study. Third chapter is dedicated to the study of droplet size distribution of non reactive two-phase GHe-LO2 jet in a quartz tube. Thus, a droplet size map is constituted through the whole tube, for different helium injection speeds. These results are compared with theoretical study dealing with vaporization and movement of a droplet and with numerical simulations on jet behavior close to the injector. Fourth chapter presents results of a detonation study of a reactive GH2-LO2 two-phase mixture in a semi-open tube. Detonation is studied as a function of following parameters: initiation energy, spark initiation device location along the tube, global equivalence ratio. Velocity, peak pressure and three-dimension structure detonation are the main data collected to study two-phase detonation phenomena. A theoretical study of detonation characteristics brings additional information on detonation at low temperature (100 K)

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Becker, William J. « Dynamic surface temperature measurement on the first stage turbine blades in a turbofan jet engine test rig ». Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43743.

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Turbine blade surface temperatures were studied during transient operation in a turbofan engine test rig. A single fiber radiation pyrometer was used to view the suction side of the blades from approximately 60 percent axial chord to the trailing edge at an average radial location of 70 percent blade height. A single ceramic-coated blade produced a once-per-revolution signal that allowed for the tracking of individual blades during the transients. The investigation concentrated on the light-off starting transient and the transients obtained during accelerating and decelerating between power settings. During starting and acceleration transients, the blade surface temperature gradient was observed to reverse. This phenomenon was most apparent during starting when the trailing edge was initially much hotter than the 60 percent chord location, resulting in large temperature gradients. In steady operation the trailing edge temperature was lower than the 60 percent chord location, and the gradients were less severe. During deceleration transients, the trailing edge cooled more rapidly than the 60 percent chord location. This resulted in larger temperature gradients than were seen in steady operation, but no profile inversion was observed. These temperature gradients and profile inversions represent a cycling of thermally-induced stresses which may contribute to low cycle fatigue damage. A simple one-dimensional heat transfer model is presented as a means of explaining the different heating rates observed during the transients.
Master of Science

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Benyo, Theresa L. « Analytical and Computational Investigations of a Magnetohydrodynamic (MHD) Energy-Bypass System for Supersonic Turbojet Engines to Enable Hypersonic Flight ». Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1369153719.

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Khanna, Yash. « Conceptual design and development of thermal management system for hybrid electric aircraft engine. : A study to develop a physical model and investigate the use of Mobil Jet Oil II as coolant for aircraft electrical propulsion under different scenarios and time horizons ». Thesis, Mälardalens högskola, Framtidens energi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-46612.

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The ever-increasing levels of greenhouse gas emissions has led to the scientific community starting to explore the viability of electrical aircraft system, with the most prominent research and product development for hybrid electric system, which forms the transition phase from combustion to fully electric aircrafts. The primary objective of this thesis is to find solutions towards thermal management of the electrical components of a hybrid electric aircraft propulsion system, which generate a significant amount of heat while operating at heavy load conditions required to propel an aircraft. In view of these objectives a micro channel cold plate liquid cooling system, has been dynamically modelled using a combination of lumped parameter and thermal resistance methods of heat transfer analysis. The study investigates the prospects of using Mobil Jet Oil II, typically used as an aircraft lubricant as a coolant for the thermal management system. The primary components of this model are lithium ion battery, DC-AC inverter, permanent magnet motor, cross flow finned micro channel heat exchanger, centrifugal pump and ducts. The electrical components have been dimensioned according to energy storage and load requirements considering their efficiencies and gravimetric power/energy. The system has been simulated and analyzed under different scenarios considering the coolant inlet temperature, air temperature across the heat exchanger and on two-time horizons. Analysis has been done to study the dynamic trends of the component temperature and the coolant at different stages of the system. The scope of the study includes an evaluation of the added weight of the thermal management system under different time horizons and their comparison with results from a reference study. From the simulation results it can be concluded that Mobil Jet Oil II is a promising option as a coolant and therefore its use as a common fluid for gas turbine lubrication and as coolant, will benefit the aircraft as now no extra coolant reservoir is required, allowing reduction in weight carried by the aircraft.

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Solovev, Alexander Alexandrovich. « Catalytic Tubular Micro-Jet Engines ». Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-92005.

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This dissertation offers demonstrations of autonomous catalytic microtubes (microjet engines) with tunable diameters ranging from micro- to nanoscale and lengths from 50 μm to 1 mm. These results open the door to effective microengines and represent the entry in the Guinness Book of World Records for “the smallest man-made jet engine.” Several attractive methodologies of machine-based functions at the micro- and nanoscale are shown. For instance, catalytic Ti/Cr/Pt microjets, which are integrated on a planar substrate, can operate as “on chip” chemical micropumps by decomposition of hydrogen peroxide fuel into oxygen bubbles and water. When released from a substrate, microjets self-propel autonomously in solution. The incorporation of ferromagnetic layer (Fe) into the rolled-up geometry enables their remote control using external magnetic field. Such microjets were used to load, transport, deliver and assemble multiple cargo particles, including biological cells in bulk solutions and microfluidic channels. Furthermore, it is demonstrated that for microjets that are fixed to or self-propelled above a platinum patterned surface, the microengine power/speed can be controlled using a white lightsource. A change in intensity of the white light leads to a controllable switching “off” and “on” of the microengine power on demand. Light degrades a local concentration of the hydrogen peroxide fuel and surface tension and subsequently suppresses the generation of oxygen microbubbles. In the next step, the diameter of the microjets was rigorously reduced to 250 nm by using hybrid heteroepitaxial/catalytic InGaAs/GaAs/Cr/Pt nanotubes. Due to asymmetry of the rolled-up layers, these nanojets move in corkscrew-like motions and act as “self-propelled nanotools,” which were used in the next step to transport yeast cells and drill into fixed cancer Hela cells. Although it is well-known that hydrogen peroxide cannot be used to sustain viable cellular function, it is however conceivable that alternative fuels, such as glucose, might enable operation of such nanotools under biologically compatible conditions. As a first step to achieve this goal, demonstrations were made using metal-enzyme biocatalytic Ti/Au/SAM/Catalase microengines. Synthetic components with competing interactions are well-suited to study the emergence of their collective behavior, such as swarms of large numbers of individuals. Microengines’ self-organization in bistable swarms is shown at the air-liquid interface of the mixture of propylene carbonate and hydrogen peroxide. Microengines act as “water striders.” Buoyed by oxygen bubbles, they self-propel via the microbubble recoiling mechanism and, depending on the bubbles’ sizes, self-organize into swarms due to the meniscus climbing effect. These reversible swarms depend on the microengine power, which competes against attracting surface tension force. The demonstrated microjet engines show great promise for emerging applications, including biomedical, on-chip, environmental, and robotic micromachines. Furthermore, a key method discovered, entitled “rolled-up nanotechnology on polymers,” allowed for the fabrication of highly parallel arrays of microtubes with multiple functionalities and aimed for different purposes.

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Greaves, Matthew. « Acoustic liners of jet engines ». Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/33817.

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Acoustic liners employing the Helmholtz resonator concept are commonly used in the intake duct of modern jet engines to reduce radiated noise. In response to reports of core failures, the possibility of acoustic loading as the source of these liner failures is investigated. Experimental data are used as input to a model for non-rigid cavity walls and the induced stresses analysed. An alternative, more robust, liner design utilizing viscous damping is proposed, and an analytical model developed and numerically validated against published data. A study of the key parameters leads to an improved configuration, the attenuating properties of which are compared to a typical liner.

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Williams, John Charles. « Water ingestion in jet engines ». Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/265455.

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Civil aircraft engines are required to operate reliably in a variety of inclement weather situations. Ingestion of airborne water has been found to cause problems for certain engine types, particularly during aircraft descent at low engine power settings. The effects of water ingestion under these engine operating conditions are not well understood. It is believed that the engine pe1formance is largely dete1mined by the behaviour of liquid water in the core compression system. A programme of experimental and theoretical research has therefore been undertaken to investigate the effects of water ingestion on an axial flow compressor operating at low speed, in isolation from other engine components. Experimental studies have been conducted using a low-speed, four-stage axial flow laboratory compressor, modified to facilitate injection of water through spray nozzles fitted at the inlet. In the process, new methods were developed for the reliable measurement of static pressure in a wet environment. Compressor pe1formance changes were quantified by measming the overall total-to-static pressure-rise characteristic and the torque requirement. Initiation of water ingestion was shown to move the compressor operating point on the characteristic to a new position at reduced pressure rise and reduced air mass flowrate, and to increase significantly the torque requirement. In some cases, it was shown that initiation of water ingestion would lead to rotating stall. Experiments were conducted to investigate the effects of water-to-air mass flowrate ratio, droplet size and spray coverage. The spray coverage is the fraction of the compressor inlet area over which the water is distributed. This was determined principally by the divergence (or spray) angle of the water emerging from each nozzle. The results suggest that droplet size is relatively unimportant in determining the performance with water ingestion. The spray coverage is, however, important, with small spray coverage resulting in little or no loss of compressor surge margin and large spray coverage resulting in significant loss. The pe1formance of the first compressor stage is c1itical in explaining these differences in behaviour. Theoretical studies were conducted with the aim of predicting the spatial disttibution of liquid water inside a compressor. New models were developed for key aspects of liquid water behaviour and incorporated into a computer program. Droplet velocity (or momentum) is often found to play an important role in determining the water behaviour. Theories are suggested to explain the experimentally observed effects of water ingestion, drawing on insight gained from both the expe1imental and theoretical results. Compressor modifications that may reduce the adverse effects of water ingestion are then suggested. These comprise, firstly, the removal of water from the casing immediately upstream of the compressor and, secondly, the application of a "non-stick" coating to the blades of the first rotor blade row.

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Negrel, Christian Claude. « Missed opportunities : NACA and jet propulsion ». Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/52093.

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This study examines NACA's organization in the light of Alfred D. Chandler's Strategy and Structure. It analyzes the agency's administration. NACA's strategy of maximizing existing technology and its committee's structure were the key elements in its failure to develop jet propulsion in the early 1940s. We will focus first on NACA and its organization. The second chapter will describe jet propulsion, particularly the acquisition of a Whittle engine from England and General Arnold 's role in keeping NACA out of the development of the Whittle engine in the United States. The third chapter will concentrate on the reasons that combined and led to the difficulties of NACA in the mid-forties and the 1950s. That chapter will look at the rise of the aviation industry, the criticism it expressed against NACA, and finally NACA's strategy as one of the causes of failure.
Master of Arts

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Plewacki, Nicholas. « Modeling High Temperature Deposition in Gas Turbines ». The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587714424017527.

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Tipnis, T. J. « Effects of upstream nozzle geometry on rectangular free jets ». Thesis, Depatment of Engineering Systems and Mangement, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4557.

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This study is aimed at understanding the effects of changing the upstream nozzle geometry on the development of rectangular free jets. An existing converging rectangular nozzle with an exit aspect ratio of 4 and a circular inlet (AR4 nozzle) has been used as the basic configuration for this work. The study is primarily based on the results of numerical simulations wherein the internal geometry variation is accomplished by changing the inlet aspect ratio (AR,) and the length of the converging section, expressed as a ratio with respect to the length of the nozzle (called 'converging section ratio*, CSR); all the other parameters are kept constant. The results from LDA experiments done on the AR4 nozzle are presented and used as validation data for the CPD simulations. Analyses of the numerical results help in understanding the variation of the jet spreading for different combinations of AR, and CSR. Two parameters are identified for describing the jet development: the cross-over point (XC), defined as the location downstream of the exit where the jet half-velocity-widths (B) along the major and minor axes are equal, and the difference in the half-velocity-widths at 30 nozzle equivalent diameters (Dm) from the exit (AB30), to ascertain the occurrence of axis-switching. For a given AR,, XC varies linearly with CSR; the variation of XC is non-linear with AR, for a constant CSR. The A1330 variation is non-linear with both AR, and CSR; the other variable being kept constant. The data obtained from the simulations are further used to propose two parametric models which can be used to predict the occurrence of axis-switching, within the scope of this work. The parametric models are validated and future work is proposed.

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Smith, Matthew James. « The Analysis and Prediction of Jet Flow and Jet Noise about Airframe Surfaces ». Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23897.

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Aircraft noise mitigation has been an ongoing challenge for the aeronautics research community. In response to this challenge, aircraft concepts have been developed in which the propulsion system is integrated with the airframe to shield the noise from the observer. These concepts exhibit situations where the jet exhaust interacts with an airframe surface. Jet flows interacting with nearby surfaces exhibit a complex behavior in which acoustic and aerodynamic characteristics are altered. The physical understanding and accurate modeling of these characteristics are essential to designing future low-noise aircraft. In this thesis, an alternative approach is created for predicting jet mixing noise that utilizes an acoustic analogy and the solution of the steady Reynolds-Averaged Navier-Stokes (RANS) equations using a two equation turbulence model. A tailored Green's function is used in conjunction with the acoustic analogy to account for the propagation effects of mixing noise due to a nearby airframe surface. The tailored Green's function is found numerically using a newly developed ray tracing method. The variation of the aerodynamics, acoustic source, and far- field acoustic intensity are examined as a large flat plate is moved relative to the nozzle exit. Steady RANS solutions are used to study the aerodynamic changes in the field-variables and turbulence statistics. To quantify the propulsion airframe aeroacoustic (PAA) installation effects on the aerodynamic source, a non-dimensional number is formed that can be used as a basic guide to determine if the aerodynamic source is affected by the airframe and if additional noise produced by the airframe surface is present. The aerodynamic and noise prediction models are validated by comparing results with Particle Image Velocimetry (PIV) and far-field acoustic data respectively. The developed jet noise scattering methodology is then used to demonstrate the shielding effects of the Hybrid Wing Body (HWB) aircraft. The validation assessment shows that the acoustic analogy and tailored Green's function provided by the ray tracing method are capable of capturing jet shielding characteristics for multiple configurations and jet exit conditions.
Master of Science

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Kallingalthodi, Hari. « Cavitation Detection In a Water Jet Propulsion Unit ». Thesis, University of Canterbury. Electrical and Computer Engineering, 2009. http://hdl.handle.net/10092/4438.

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Various sensing and digital signal processing approaches to detect cavitation in a water jet propulsion unit were examined based on results in the literature. Several commercially viable sensors were evaluated based upon their ability to detect the cavitation phenomenon, cost, and robustness. An algorithm has been implemented and tested against data recorded from the candidate sensors. The combination of vibration and pressure sensors and the algorithm appear promising and a path for further development and testing is available to Hamilton Jet.

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DeMont, Malcolm Edwin. « Mechanics of jet propulsion in a hydromedusean jellyfish ». Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27065.

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A non-destructive test was developed to measure the static mechanical properties of the locomotor structure (bell) in the hydromedusean jellyfish, Polyorchis penicillatus. A nonlinear stress-strain relationship was found, and the mean static structural stiffness of the bell was 150 N m⁻² . Observations that showed the natural changes in the geometry of the bell during deformation were used to estimate the static modulus of elasticity of the mesogleal material, and gave a modulus of 400 N m⁻². Dynamic measurements on isolated samples of mesoglea gave a mean storage modulus of 1000 N m⁻². The resilence of the material was about 58%. These data were integrated to infer that the dynamic structural stiffness of the bell is at least 400 N m⁻². Attempts to quantatitively measure the dvnamic structural stiffness imply that the dynamic structural stiffness must lie between 400 N m⁻² and 1000 N m⁻² All, or most, of the potential energy stored in the mesoglea during contractions of the bell is apparently stored as strain energy in the radial mesogleal fibers. The mechanical energy generated by the contraction of the subumbrellar swimming muscles to power the jet cycle was measured. This energy was experimentally partitioned into three components during the contraction. The algebraic sum of these components was taken to be the mechanical energy crenerated by the muscles during the iet cycle, and was between -5 -4 8.9 x 10⁻⁵ and 1.4 x 10⁻⁴. Energy from one of these components is stored as strain energy in the mesoglea and powers the refilling phase. The mesoglea can clearly act as an effective elastic structure to completely antagonize the contraction of the swimming muscles, and may be designed to function at some optimum. The mechanical significance of elastic energy storage systems in jet-propelled animals is discussed, and this significance is clearly displayed in Polvorchis. The unusual long duration action potential of the swimming muscles may have some mechanical significance with regard to the elastic energy storage system. It is suggested that the action potential of vertebrate cardiac muscle may have the same mechanical function. The locomotor bell of the hydromedusean jellyfish was modelled as a harmonically forced damped oscillator. The robustness of the model was tested and verified by comparing estimates of the work done during the contraction phase predicted by the model to analogous values measured in completely independent experiments. Data suggest that the animals swim at a frequency that is at or near the resonant frequency of the locomotor apparatus. The implications of this phenomenon to the mechanics and physiology of the system are discussed. If the swimming muscles force the bell at its resonant frequency, as opposed to a single contraction at the same rate of deformation, the amplitude of the oscillation will be increased by about 40%, and the energetic requirement for the cycle will be reduced by about 24% to 37% of the total cost of the cycle. The advantages of forcing the structure at its resonant frequency seem quite remarkable. Two aspects of the physiology of the swimming muscles are probably functionally related to this phenomenon and are discussed.
Science, Faculty of
Zoology, Department of
Graduate

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20

Porcheron, Emmanuel. « Atomisation d'un jet liquide par un jet de gaz inerte appliquée à la propulsion cryotechnique ». Poitiers, 1998. http://www.theses.fr/1998POIT2300.

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Cette etude participe a l'identification des processus mis en jeu lors de l'atomisation d'un jet liquide (eau et oxygene liquide) par un jet de gaz coaxial (air, helium, azote et argon), simulant la configuration d'injection rencontree sur un moteur cryotechnique tel que le vulcain de la fusee ariane v. La visualisation du jet par plan laser pulse ou par camera rapide, permet de donner une description des mecanismes conduisants a la rupture du jet liquide. La sonde a fibre optique, qui donne acces au taux de presence du liquide dans la zone dense du jet diphasique, permet de delimiter : - le cone potentiel liquide, dont la longueur est essentiellement controlee par le rapport des densites de flux de quantite de mouvement du gaz et du liquide, ceci en accord avec le modele propose. - le dard liquide, ou longueur de rupture du jet, integre dans son expression, le nombre de weber du liquide comme facteur supplementaire. Par ailleurs, le couplage de la formation des gouttes de la pulverisation avec sa croissance spatiale, est mis en evidence a partir de mesures effectuees par anemometrie par phase doppler. L'influence du rapport des sections de passage du gaz et du liquide de l'injecteur ainsi que celle de son confinement, ont ete mises en evidence sur l'atomisation du jet liquide. Pour la geometrie particuliere d'un injecteur a grande couronne de gaz, l'atomisation primaire est intensifiee pour les faibles vitesses de gaz, alors que pour les fortes vitesses de gaz, le liquide pulverise ainsi que le brouillard forme, reste concentre dans la region centrale du jet. Le confinement ne modifie pas la dynamique de rupture du jet liquide mais il entretient une recirculation de gouttelettes dans le champ proche de l'injecteur et reduit globalement, l'efficacite de l'atomisation secondaire ce qui se traduit par une augmentation de la granulometrie moyenne de la pulverisation. La caracterisation de l'atomisation d'un jet d'oxygene liquide, conduite sur le banc d'injection mascotte de l'onera, a permis de mettre en evidence et d'interpreter le role amplificateur de la masse volumique du gaz sur la rupture du jet. Une correlation de la longueur du dard liquide prenant en compte les proprietes physico-chimiques ainsi que les masses volumiques des differents fluides utilises, (eau et oxygene liquide) (helium, azote, air et argon), a ete proposee.

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Bjarnholt, Peter. « Electric Propulsion in Passenger Jet Airplanes : Requirements to realize all-electric propulsion ». Thesis, KTH, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209852.

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Passenger jet airplane propulsion systems are today dominated by turbo-jet engines that burn fossil fuels. The unsustainability of this is a concern both from an economic and environmental point of view. This research identifies the limiting factors in achieving to build a compelling battery-electric passenger jet airplane, and predict the range that can be achieved today and in the foreseeable future. literature study was performed to find the necessary performance data for all technical components. To analyze the performance of an electric propulsion system, the Boeing 787-8 was chosen as a reference and comparison. Piano-X, a program used for simulating the performance of different aircrafts under different conditions was then used to get data for fuel consumption and performance data for the airplane. The gravimetric energy density of the batteries was found to be the greatest limiting factor. Electric motors and power electronics were found to have about the same performance as a modern turbo-fan engine in terms of gravimetric power density. The results also showed that with today’s batteries, that present an energy density of 250 Wh/kg, the range is limited to about 600 km, assuming a 40% cell-mass-fraction and 25% improvement in flight efficiency. In conclusion, the challenge in creating a compelling all-electric passenger jet airplane is a big one, but not impossible. Assuming battery technology continues to improve at current rate, and design optimizations are done to the airplanes, a range over 1400 km seems to be possible within the next decade.
Passagerarflygplans framdrivningssystem är idag dominerat av turbo-jetmotorer som använder sig av fossila bränslen. Denna icke hållbara lösning är ett bekymmer både ur en ekonomisk och en miljömässig synvinkel. Denna forskningsstudie identifiera de begränsande faktorerna för att uppnå tillverkning och användningen av elektriska passagerarflygplan med hjälp av batteri, och förutsäga omfånget som går att uppnås i dag och inom överskådlig framtid. En litteraturstudie genomfördes för att hitta nödvändiga prestanda-data för alla tekniska komponenter. För att analysera resultatet av ett elektriskt framdrivningssystem, var Boeing 787-8 valts som en referens och en jämförelse. Piano-X är ett program som används för att simulera prestanda hos olika flygplan under olika förhållanden. Detta program användes för att få uppgifter om bränsleförbrukning och för att få fram prestanda-data för flygplanet. Den gravimetriska energi-densiteten hos batterierna upptäcktes att vara den störst begränsande faktorn. Elektriska motorer och kraftelektronik befanns sig ha ungefär samma prestanda som en modern turbo-fläktmotor, i befattning av gravimetrisk effekttäthet. Resultaten visade att med dagens batterier, som har en energitäthet av 250 Wh/kg, är räckvidden begränsad till ca 600 km, med antagande av en 40 % cellmassfraktion och 25 % förminskning av total energiåtgång under flygning. Sammanfattningsvis är utmaningen i att skapa en övertygande hel-elektrisk passagerarflygplan stor, men inte omöjligt. Förutsatt att batteriteknologin fortsätter att förbättras i nuvarande takt, och designoptimeringar görs för flygplanen, är en räckvidd över 1400 km möjligt inom de närmaste tio åren.

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Bilgin, Murat. « Stationary and rotating hot jet ignition and flame propagation in a premixed cell / ». Thesis, Connect to this title online ; UW restricted, 1998. http://hdl.handle.net/1773/9986.

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Pietroniro, Asuka Gabriele. « Modelling coaxial jets relevant to turbofan jet engines ». Thesis, KTH, Mekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-200909.

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Simulations of subsonic turbulent coaxial hot jets were conducted on two types ofunstructured grids within the framework of STAR-CCM+. The study case is based on atypical airliner turbofan engine model with a core nozzle and a fan nozzle, having a bypassratio of five. The two meshes used are a polyhedral one, suitable for complex surfaces, and atrimmed one mainly made of hexahedral cells. The sensitivity of the study case to variousinputs is attested using second and third order upwind schemes, modelling turbulence with aSST k-omega model. The project proves to be a valid feasibility study for a steady-statesolution on which an aeroacoustic analysis could be based in future works.

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Pietroniro, Asuka Gabrielle. « Modelling coaxial jets relevat to turbofan jet engines ». Thesis, KTH, Mekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-204020.

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Simulations of subsonic turbulent coaxial hot jets were conducted on two types ofunstructured grids within the framework of STAR-CCM+. The study case is based on atypical airliner turbofan engine model with a core nozzle and a fan nozzle, having a bypassratio of five. The two meshes used are a polyhedral one, suitable for complex surfaces, and atrimmed one mainly made of hexahedral cells. The sensitivity of the study case to variousinputs is attested using second and third order upwind schemes, modelling turbulence with aSST k-omega model. The project proves to be a valid feasibility study for a steady-statesolution on which an aeroacoustic analysis could be based in future works.
Simuleringar av subsoniska turbulenta koaxiala varma flöden genomfördes på två typer avostrukturerade nät inom ramen för STAR-CCM+. Studiefallet är baserat på en modell av enturbofläktmotor för ett typiskt trafikflygplan, med en inre samt yttre dysa och med ett bypassförhållandeav fem. De två beräkningsnät som används är ett polyedriskt nät, lämplig förkomplexa ytor, och ett trimmat nät huvudsakligen uppbyggt av sexsidiga celler. Känslighetenav studiefallet beroende på olika indata intygas med hjälp av andra och tredje ordningens”upwind-schemes”, där turbulensen modelleras med en SST k-omega modell. Projektet visarsig vara en giltig förstudie för en steadystate-lösning på vilken en aeroakustisk analys skullekunna baseras i framtida arbeten.

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Polsenberg, Thomas AnnMarie Burdick Joel Wakeman Dabiri John Oluseun. « Exploration into the feasibility of underwater synthetic jet propulsion / ». Diss., Pasadena, Calif. : Caltech, 2007. http://resolver.caltech.edu/CaltechETD:etd-09252006-134742.

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26

Söderberg, Jansson Marcus. « Analysis of the intake grill for marine jet propulsion ». Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-263877.

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Marine waterjet propulsion is a technology that has been developed and refined since the early 1950’ and is proven highly useful for high speed applications with vessels in varying sizes. The intake grill is a component that is mounted in line with the hull to prevent debris from traveling through the waterjet. The intake grill is affected by viscous forces, contact forces and harmonic excitation forces all while affecting the efficiency of the waterjet. In this report a selection of methods is evaluated and verified with the goal of simplifying the design process of the intake grill. A selection of cross-sections is generated and evaluated to draw general conclusions about the efficiency and stability of the intake grill. A selection of computational fluid dynamics and modal analysis methods are utilized. It is concluded that the intake grill is affected by many parameters and can be evaluated by modal FEM analysis and 2D CFD analysis.
Marina vattenjetmotorer har utvecklats och förfinats sedan tidigt 50-tal och har bevisats mycket användbara för applikationer i hög hastighet med båtar i varierande storlekar. Intagsgaller är en komponent som monteras i linje med skrovet på båtar för att förhindra oönskade föremål att färdas genom intaget på vattenjetmotorn. Intagsgallret är påverkat av viskösa krafter, direkta krafter och harmonisk excitation samtidigt som komponenten påverkar vattenjetmotorns effektivitet. I denna rapport så evalueras ett urval av metoder med målet att simplifiera utvecklingsprocessen av intagsgaller. Ett urval av tvärsnittsgeometrier är genererade och evaluerade för att dra generella slutsatser om effektiviteten och stabiliteten av intagsgallret. Ett par olika sorters flödessimuleringar och finita element metoder används. Slutsatsen är att intagsgallret påverkas av ett flertal parametrar och kan utvärderas med modal finita element metoder samt tvådimensionella flödessimuleringar.

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27

Hamori, Ferenc. « Exploring the limits of hydrogen assisted jet ignition / ». Connect to thesis, 2006. http://eprints.unimelb.edu.au/archive/00001606.

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28

Caudill, Michael R. « Methods for performance goal setting of fielded jet engines ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA301274.

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29

Bensel, Artur. « Characteristics of the Specific Fuel Consumption for Jet Engines ». Aircraft Design and Systems Group (AERO), Department of Automotive and Aeronautical Engineering, Hamburg University of Applied Sciences, 2018. http://d-nb.info/1175791237.

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Purpose of this project is a) the evaluation of the Thrust Specific Fuel Consumption (TSFC) of jet engines in cruise as a function of flight altitude, speed and thrust and b) the determination of the optimum cruise speed for maximum range of jet airplanes based on TSFC characteristics from a). Related to a) a literature review shows different models for the influence of altitude and speed on TSFC. A simple model describing the influence of thrust on TSFC seems not to exist in the literature. Here, openly available data was collected and evaluated. TSFC versus thrust is described by the so-called bucket curve with lowest TSFC at the bucket point at a certain thrust setting. A new simple equation was devised approximating the influence of thrust on TSFC. It was found that the influence of thrust as well as of altitude on TSFC is small and can be neglected in cruise conditions in many cases. However, TSFC is roughly a linear function of speed. This follows already from first principles. Related to b) it was found that the academically taught optimum flight speed (1.316 times minimum drag speed) for maximum range of jet airplanes is inaccurate, because the derivation is based on the unrealistic assumption of TSFC being constant with speed. Taking account of the influence of speed on TSFC and on drag, the optimum flight speed is only about 1.05 to 1.11 the minimum drag speed depending on aircraft weight. The amount of actual engine data was extremely limited in this project and the results will, therefore, only be as accurate as the input data. Results may only have a limited universal validity, because only four jet engine types were analyzed. One of the project's original value is the new simple polynomial function to estimate variations in TSFC from variations in thrust while maintaining constant speed and altitude.

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Gnanakumaran, Gnanach Selvan. « Condensation in jet engine intakes and fans ». Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609623.

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31

Whitehead, James Anthony. « Aerodynamics and propulsion of synthetic jet based micro air vehicles ». Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409883.

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32

Brookes, S. J. « Soot Production and Thermal Radiation from Turbulent Jet Diffusion Flames ». Thesis, Cranfield University, 1996. http://hdl.handle.net/1826/3558.

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The aim of this study is to advance the present capability for modelling soot production and thermal radiation from turbulent jet diffusion flames. Turbulent methane / air jet diffusion flames at atmospheric and elevated pressure are studied experimentally to provide data for subsequent model development and validation. Methane is only lightly sooting at atmospheric pressure whereas at elevated pressure the soot yield increases greatly. This allows the creation of an optically thick, highly radiating flame within a laboratory scale rig. Essential flame properties needed for model validation are measured at 1 and 3 atm. These are mean mixture fraction, mean temperature, mean soot volume fraction, and mean and instantaneous spectrally resolved radiation intensity. These two flames are modelled using the parabolic CFD code GENMIX. The combustion / turbulence interaction is modelled using the conserved scalar / laminar flamelet approach. The chemistry of methane combustion is modelled using a detailed chemistry laminar flame code. The combustion model accommodates the non-adiabatic nature of the flames through the use of multiple flamelets for each scalar. The flamelets are differentiated by the amount of radiative heat loss that is included. Flamelet selection is carried out through the solution of a balance equation for enthalpy, which includes a source term for the radiative heat loss. A new soot model has been developed and calibrated by application to a laminar flame calculation. Within the turbulent flame calculations the soot production is fully coupled to the radiative loss. This is achieved through the use of multiple flamelets for the soot source terms and the inclusion of the radiative loss from the soot (as well as the gases) in the enthalpy source. Spectral radiative emission from the flames has been modelled using the RADCAL code. Mean flame properties from the GENMIX calculations are used as an input to RADCAL.

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Sementi, Joshua Paul. « A study of jet exhaust-wing interaction / ». Thesis, Connect to this title online ; UW restricted, 2005. http://hdl.handle.net/1773/10002.

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34

Malsbury, John A. « Methods for determining goals and expectations for fielded jet engines ». Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA306250.

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35

Robledo, Raymond F. 1968. « Pulmonary response to inhaled jet-propulsion fuel 8 aerosol in mice ». Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288888.

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Studies were initiated to characterize the acute and sub-chronic pulmonary responses to inhaled Jet-Propulsion Fuel 8 (JP-8) aerosol. At 24 to 30 hours following JP-8 exposure, physiological, biochemical, cellular, and morphological techniques were used to assay for lung injury. In addition, C57BL/6 and B6.A.D.(Ahyd mice were utilized in the acute study to determine if responsiveness to aryl hydrocarbon hydroxylase (AHH) induction modulates toxicity. JP-8 contains aromatic compounds that are known substrates for AHH. Acute lung injury was evident by increased respiratory permeability that was accompanied by alveolar macrophage infiltration and activation, following exposure to occupational permissible levels of JP-8. Morphological alterations were characterized by terminal bronchiolar lesions of vacuolization and necrosis. AHH responsiveness did not appear to influence the severity of JP-8 induced lung injury. Lung injury following sub-chronic inhalation was found to be progressive in nature. Repeated exposure induced alveolar hemorrhage and alveolar macrophage cytotoxicity. Morphological changes progressed to include epithelial denudation of bronchiolar airways and vacuolization of alveolar type II epithelial cells and adjacent endothelia. The pulmonary clearance of JP-8 following inhalation exposures was determined indirectly by analysis for tetradecane content within lung homogenates from exposed mice. Clearance of JP-8 following acute exposure was determined to have a half-life of 43 minutes and increased by 14 minutes following a toxic sub-chronic exposure. The relatively rapid pulmonary clearance of JP-8 following either acute or sub-chronic exposure implies that JP-8 induced lung injury was independent of pulmonary retention. Studies were also performed to determine if non-cytotoxic concentrations of JP-8 or tetradecane could decrease bronchial epithelial barrier function. Studies showed that one hour of exposure to JP-8 or tetradecane could significantly enhance paracellular permeability to mannitol in the BEAS-2B human bronchial epithelial cell line, at two hours after exposure. Bronchial epithelial permeability appeared to be more sensitive to tetradecane than JP-8. Subsequent recovery studies determined that JP-8 and tetradecane-induced decreases in barrier function reach a maximum at 12 hours and barrier function returns to control by 48 hours post-exposure. These results indicate that JP-8 induced lung injury may be initiated by changes in airway barrier function.

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Neil, Thomas Robert. « Muscle mechanics and hydrodynamics of jet propulsion swimming in marine invertebrates ». Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15435/.

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Locomotion amongst animals is widespread and diverse. Movement is of fundamental biological importance to animals, enabling them to forage, migrate, pursue prey and mate. Animals have evolved a great range of locomotor mechanisms that span huge size ranges and diversity across the animal kingdom, yet several common principles underlie most of these mechanisms, the understanding of which can help explain why certain biological locomotor systems have evolved for particular environments. Constraints on an animal’s morphological traits are bought about by body size, meaning that several aspects of locomotor performance are found to vary with body mass. Burst performance plays a crucial role in many animals lives, with the ability to accelerate and manoeuvre quickly often being essential for survival. The power available from the muscles during this type of locomotion is generally thought to decrease with increasing body size, with cycle frequency predicted to limit maximal muscle mass-specific performance. Muscle mass-specific power was measured in vivo in scallops covering a 96-fold range in body mass. Power was measured using sonomicrometry crystals to measure muscle length changes during swimming whilst pressure was simultaneously monitored within the mantle cavity. The scaling of the contractile characteristics of the adductor muscles of scallops was investigated to determine what affect the intrinsic properties of the muscle have on the scaling of muscle power output. Muscle fibre bundles were dissected and attached to a force transducer to measure force and muscle length change. Muscles were electrically stimulated via platinum plate electrodes. The scaling of twitch kinetics and the force velocity relationship were characterised in vitro. Jet propulsion via pulsed jets have been shown to be able to produce more thrust per unit of ejected fluid then an equivalent steady jet. The benefit is bought about through the production of isolated vortex rings, which entrain additional ambient fluid into the wake. There are numerous biological swimmers that use jet propulsion as their primary form of locomotion, however, their ability to be able to use vortex rings to enhance their propulsive performance has only been investigated in a few systems. Jet wake structure and swimming performance were quantified in three animals that swim by jet propulsion; scallops, Nautilus and jellyfish. The properties of the wakes were characterised using particle image velocimetry to measure the wake structure of the jets that were produced. Muscle mass-specific power output was found to decrease with increasing size in scallops. Frequency decreased with increasing size, muscle stress was found to be approximately constant whilst muscle strain decreased with increasing size in king scallops. The scaling exponents for muscle power were greater than those of the scaling of cycle frequency, suggesting that cycle frequency is not the sole determinant of the scaling of muscle power output. Muscle power output measured in vitro was also found to decrease with increasing body mass, but scaled with an exponent greater than that measured in vivo. The Vmax of the muscles decreased with increasing size, but did not scale in the same way as cycle frequency, suggesting that the intrinsic contractile properties of the muscle were not the sole determinant of cycle frequency in scallops. King scallops and Nautilus were found to produce two distinct jet modes, one in which isolated vortex rings were produced (Jet mode 1) and one which consisted of a leading vortex ring followed by a trailing jet of fluid (Jet mode 2). No differences were found in jet mode and the thrust produced from the jet, although enhanced thrust was found in king scallops producing jets at formation numbers of ~4. The wake structure of Rhizostomeae jellyfish revealed that they propel themselves via and interaction of two vortex rings that are produced as they swim. They were also found to manipulate the formation of a vortex ring that is formed as they swim, manoeuvring it to within their sub-umbrella cavity, providing them with an additional boost during swimming.

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Marc, Mickael. « Modélisation numérique d'un système de propulsion à jet de véhicules nautiques ». Mémoire, Université de Sherbrooke, 2009. http://hdl.handle.net/11143/5498.

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Aujourd'hui divers systèmes de propulsion marins existent dont les systèmes de propulsion à jet. De nombreuses études ont été réalisées au cours des vingt dernières années et plus particulièrement par le biais de la simulation numérique ( Computational Fluid Dynamics , ( CFD )). Un modèle numérique simulant l'écoulement au travers un système de propulsion avec une pompe en rotation est développé dans ce projet. Il est également validé avec des résultats expérimentaux obtenus par d'autres chercheurs. Pour se [i.e. ce] faire, différentes étapes sont réalisées. En premier lieu, des paramètres tels que le maillage, le modèle de turbulence ou la modélisation de la rotation du rotor sont validés numériquement sur deux géométries. Le premier cas, bien documenté, correspond à un écoulement au travers une conduite en forme de"S" de section divergente et validé expérimentalement. Le second cas est une pompe où le rotor est en mouvement dans l'écoulement. Un modèle à multiple systèmes de référence ( Multiple Reference Frame,MFR ) est utilisé pour simuler la rotation de la pompe. Les paramètres numériques sont alors fixés pour la suite de l'étude. Ensuite un inodéle numérique d'un système de propulsion à jet d'une motomarine est développé dans un volume de contrôle réduit. Il prend en compte l'ensemble de la géométrie de la propulsion : la pompe en rotation, le venturi et une partie de la coque réelle du véhicule. Les conditions aux frontières sous la coque sont imposées grâce aux données d'une simulation complète du véhicule entier. Ce modèle est validé expérimentalement à deux vitesses (25 mph et 69 mph). Le comportement de l'écoulement est ensuite analysé. Finalement diverses variations géométriques sont effectuées telles que la supression [i.e. suppression] d'appendices dans la conduite ou le déplacement latéral de la lèvre de l'entrée d'eau à divers IVR, Inlet Velocity Ratio (rapport entre la vitesse du véhicule et celle de la pompe). Une augmentation des performances du système est observée à un certain IVR pour une supression [i.e. suppression] d'appendice donnée. La présence d'une plaque permettant le redressement de l'écoulement au niveau de la grille est néfaste à la poussée de même que la présence de l'arbre ou d'ailettes situées à l'entrée de la pompe. Le déplacement de la lèvre a pour objectif de déterminer la position optimale qui permet d'obtenir la meilleure augmentation de performance pour un IVR .

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Richardson, Ian J. « Stress and failure analysis of curvic couplings ». Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323612.

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Hall, Cesare Alan. « Fan-nacelle interactions in natural wind ». Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/251859.

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40

Benegas, Jayme Diego. « Evaluation of the Hybrid-Electric Aircraft Project Airbus E-Fan X ». Master's thesis, Aircraft Design and Systems Group (AERO), Department of Automotive and Aeronautical Engineering, Hamburg University of Applied Sciences, 2019. http://d-nb.info/1204685894.

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Purpose - This master thesis evaluates the hybrid-electric aircraft project E-Fan X with respect to its economical and environmental performance in comparison to its reference aircraft, the BAe 146-100. The E-Fan X is replacing one of the four jet engines of the reference aircraft by an electric motor and a fan. A turboshaft engine in the cargo compartment drives a generator to power the electric motor. --- Methodology - The evaluation of this project is based on standard aircraft design equations. Economics are based on Direct Operating Costs (DOC), which are calculated with the method of the Association of European Airlines (AEA) from 1989, inflated to 2019 values. Environmental impact is assessed based on local air quality (NOx, Ozone and Particulate Matter), climate impact (CO2, NOx, Aircraft-Induced Cloudiness known as AIC) and noise pollution estimated with fundamental acoustic equations. --- Findings - The battery on board the E-Fan X it is not necessary. In order to improve the proposed design, the battery was eliminated. Nevertheless, due to additional parts required in the new configuration, the aircraft is 902 kg heavier. The turboshaft engine saves only 59 kg of fuel. The additional mass has to be compensated by a payload reduced by 9 passengers. The DOC per seat-mile are up by more than 10% and equivalent CO2 per seat-mile are more than 16% up in the new aircraft. --- Research limitations - Results are limited in accuracy by the underlying standard aircraft design calculations. The results are also limited in accuracy by the lack of knowledge of some data of the project. --- Practical implications - The report contributes arguments to the discussion about electric flight. --- Social implications - Results show that unconditional praise given to the environmental characteristics of this industry project are not justified.

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Nilamdeen, Mohamed Shezad. « An uncoupled multiphase approach towards modeling ice crystals in jet engines ». Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92185.

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42

Zhu, Zihang. « Study of volcanic ash impact onto turbine blades in jet engines ». Thesis, University of Surrey, 2019. http://epubs.surrey.ac.uk/850038/.

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Gas turbines are of great importance in industry. In the turbine section within a jet engine, thermal barrier coatings (TBCs) are utilized to protect the metal turbine blades, thus improve the efficiency of engine. However, this coating is extremely vulnerable to attack by injected particulates. This ingested particulate is often referred to as "CMAS" (Calcia-Magnesia-Alumina-Silica). Among all the CMAS materials, Volcanic Ash (VA) is the most common type which aeroengines may encounter during the flight. This type of CMAS material would melt in the combustion section by ultra high temperature and then impact the turbine blades with relatively high speed. Some of the particles would then stick on and bond with the TBC, thus cause degradation of the protecting coating. In this way, the jet engine would be permanently damaged. In the recent years, experiments have been done by different researchers to elaborate the effect of CMAS materials on TBCs. However, there is still a lack of knowledge in the bonding mechanism and physical adhesion between the CMAS particles (especially VA particles) and the substrate. A study of VA particle impingement is required in order to understand particle impingement, phase transition and heat transfer, bonding mechanism and splat morphology in detail. In this research, experiments were carried at Cambridge University, by Prof. Trevor William Clyne, Dr. James Dean and Dr. Catalina Taltavull to reproduce the VA-substrate impingement in jet engine. A Vacuum Plasma Spray (VPS) system was utilized to create a high-temperature, high-velocity flow field. Different types of Volcanic Ashes (VAs) were introduced into the experimental set-up. Sticking rate, Scanning Electron microscope (SEM) micrographs of deposition morphology were examined and collected. Chapter 3 elaborates the details of this experiment set-up and data collected from the experiment. This experiment set-up is utilized by the author for building numerical models and the result of this experiment is used to validate the numerical models. Three numerical models were built to perform a systematic study. Firstly, in Chapter 4, a Computational Fluid Dynamic (CFD) model was created to simulate the steady-state of the VPS flow field. The Discrete Particle Method (DPM) model was then utilized to simulate the injection of volcanic ash particles. After calculating the BI number, non-isothermal effects within the ceramic particles were simulated by introducing the heat transfer function by a user-defined function (UDF). This model gives the temperature gradient within and velocity of the in-flight VA particles at any time during the spray. It is shown that small particles (diameter < $10\ \mu m$) would easily be melted and reach the iso-thermal state. However, these particles would be largely influenced by the flow field thus bypass the turbine blades. The large particles (diameter > $50\ \mu m$) would easily impact the turbine blades, but would remain unmelted due to the large grain size. It is concluded that VA particles with diameter of $15\ \mu m$ to $40\ \mu m$ are the most "dangerous" particles, because these particles have both relatively high possibility to be melted, and high possibility to impact thus adhere on the substrate. Second of all in Chapter 5, systematic study of Yttria-stabilized Zirconia (YSZ) particle impingement and deposition on stainless steel in thermal spray process has been performed. A Coupled Eulerian and Lagrangian model was developed. This model contributes to simulate the process of semi-molten particle impact. By utilizing this model, both the large deformation of liquid part and the plastic deformation of the solid part could be extracted. One fully molten and two semi-molten(solid core with liquid shell and solid shell with liquid core) cases were studied. The results of the numerical model matches well with the experiment and analytical data. Interest parameters such as velocity, temperature, fraction of liquid part were varied. The contact area, splat morphology and local contact temperature were collected and studied. It is shown that, the larger the liquid fraction is, the larger the contact area would be. Moreover, effect of roughness of substrate is also studied. It is suggested that substrate roughness whose average asperity size is higher than the 1/10 of particle size is beneficial for adhesion. Third of all in Chapter 6, in order to simulate the impact for high-viscosity glass-state ceramic particles, Smoothed Particle Hydrodynamic (SPH) model was built. For high/ultra viscosity cases, traditional CFD method and Finite Element Method (FEM) would be extremely slow. SPH model transfers the Eulerian equations into Lagrangian equations. By utilizing this method, computational resources could be saved, and high viscosity impact could be simulated. The SPH algorithm was coded and equations for heat transfer was introduced to simulate the solidification of liquid. Systematic study were performed by utilizing this model. Viscosity, contact angle, velocity of particles were varied. Contact area, splat morphology and solidification at the contact area were examined. It is shown that, large contact angle would result in large contact area. However, particles impingement with low viscosity and high contact angle could result in the break up of the particles. The similar phenomena could be seen in experiment - small particles have lower viscosity and are approaching the substrate with a large contact angle. Therefore, the deposition of these types of particles show an obvious evidence of break up and oblique impact.

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Deshpande, Kshitij S. « FUEL FLOW CONTROL ISSUE IN JET ENGINES : AN EVOLVABLE HARDWARE APPROACH ». Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1197669660.

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Gete, Zenebe. « et-enhanced turbulent combustion ». Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29969.

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A study of the squish-jet design concept in spark ignition engines, with central ignition, was conducted in a constant volume chamber. The effects of jet size, jet number and jet orientation in generating turbulence and jet enhanced turbulent combustion were investigated. Three sets of configurations with three port sizes were used in this study. The research was carried out in three stages: 1.Qualitative information was obtained from flow visualization experiments via schlieren photography at 1000 frames per second. The flow medium was air. A sequence of frames at specific time intervals were selected to study the results from the respective configurations and jet sizes. The swirling nature of the flow is vivid in the offset arrangement. 2.Pre-ignition pressure and combustion pressure traces were measured with a piezoelectric pressure transducer from which characterising parameters such as maximum pressure, ignition advance and mass burn rate were analysed. Mass fraction curves were calculated using the simple model of fractional pressure rise. A maximum pressure increase of 66% over the reference quiescent combustion case, and combustion duration reduction of 77% were obtained for the offset arrangement with 2 mm diameter port. Comparisons of the times required for 10%, 50% and 90% mass burned are identified and confirmed that it took the 2 mm jet the shortest time to burn 90% of the mixture in the chamber. 3.Two-component velocity measurements were made using an LDV system. Measurements were taken in the central vertical plane of the chamber at specified locations. The data collected were window ensemble- averaged for the mean and fluctuating velocities over a number of cycles. Data intermittency and low data rate precluded, however, cycle-by-cycle analysis. Mean tangential velocities were calculated for each case and the data were used to construct a movie of the tangential velocity as a function of time, suitable for quantitative flow visualization. The vortical nature of the flow was recorded, the distribution being neither solid body rotation nor free vortex, but some complex fluid motion. The jet scale and orientation influence the in generation of turbulence flow field in the chamber, affecting the rate of combustion and the ensuing maximum pressure rise. The offset jet arrangement gives the best results, whereas radially opposed jets have a reduced effect. Increasing the number of jets in opposed arrangement does not enhance turbulent flow. Turbulent flow in the spark region during the onset of ignition was found to be important.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate

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Toulson, Elisa. « Applying alternative fuels in place of hydrogen to the jet ignition process / ». Connect to thesis, 2008. http://repository.unimelb.edu.au/10187/3532.

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Walker, Jessica Nicole. « Numerical Studies of Jet-Wing Distributed Propulsion and a Simplified Noise Metric Method ». Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/34752.

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In recent years, the aircraft industry has begun to focus its research capabilities on reducing emissions and noise produced by aircraft. Modern aircraft use two to four engines arranged on the wing or behind to produce thrust that is concentrated directly behind the engine. Kuchemann suggested a way to improve the propulsive efficiency by changing the normal configuration of engine and aircraft. This concept is the jet-wing distributed propulsion idea, which redistributes the thrust across the span of the wings. Distributed propulsion is accomplished by using many smaller engines spread across the wings or several large engines to duct the exhaust flow in a jet-wing. The jet-wing concept can be used to reduce noise and also as a replacement for flaps and slats by deflecting the jet. Since the distributed propulsion concept is also a method to reduce noise, it's important to have a simplified method of calculating the trailing edge noise of a wing.

One of the purposes of this paper was to study the effect of adding jet-wing distributed propulsion to a thick "inboard" airfoil. The two-dimensional jet-wing model was analyzed by parametric computational fluid dynamic (CFD) studies using the Reynolds-averaged, finite-volume, Navier-Stokes code GASP. The model was set up to be self-propelled by applying velocity and density boundary conditions to the blunt edge of the airfoil. A thick "inboard" airfoil from a realistic transonic wing was needed for the study and so the span station of the EET Wing was chosen. This airfoil was thick with a thickness to chord ratio of 16%. In adding distributed propulsion to this thick airfoil, it was found that there was an increase in the propulsive efficiency as compared to typical modern high-bypass-ratio turbofan engines with no negative aerodynamic consequences.

The other purpose of this study was to create and assess a simplified method to calculate the trailing edge noise metric value produced by an airfoil. Existing methods use RANS CFD, which is computationally expensive and so it seemed important to find a less expensive method. A method was formed using the Virginia Tech Boundary Layer Java Codes which calculated the characteristic turbulent velocity and characteristic turbulent length scale. A supercritical airfoil, SC(2)-0714, was used to assess the simplified method as compared to the more computationally expensive GASP runs. The results showed that this method has trends that follow those of the GASP results with the method compare well up to modest lift coefficients.
Master of Science

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Leonessa, Alexander. « Hierarchical robust nonlinear switching control design for propulsion systems ». Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/11997.

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Lambie, David. « Inlet distortion and turbofan engines ». Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305300.

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Ko, Yan-Yee Andy. « The Multidisciplinary Design Optimization of a Distributed Propulsion Blended-Wing-Body Aircraft ». Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/27257.

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The purpose of this study is to examine the multidisciplinary design optimization (MDO) of a distributed propulsion blended-wing-body (BWB) aircraft. The BWB is a hybrid shape resembling a flying wing, placing the payload in the inboard sections of the wing. The distributed propulsion concept involves replacing a small number of large engines with many smaller engines. The distributed propulsion concept considered here ducts part of the engine exhaust to exit out along the trailing edge of the wing. The distributed propulsion concept affects almost every aspect of the BWB design. Methods to model these effects and integrate them into an MDO framework were developed. The most important effect modeled is the impact on the propulsive efficiency. There has been conjecture that there will be an increase in propulsive efficiency when there is blowing out of the trailing edge of a wing. A mathematical formulation was derived to explain this. The formulation showed that the jet â fills inâ the wake behind the body, improving the overall aerodynamic/propulsion system, resulting in an increased propulsive efficiency. The distributed propulsion concept also replaces the conventional elevons with a vectored thrust system for longitudinal control. An extension of Spenceâ s Jet Flap theory was developed to estimate the effects of this vectored thrust system on the aircraft longitudinal control. It was found to provide a reasonable estimate of the control capability of the aircraft. An MDO framework was developed, integrating all the distributed propulsion effects modeled. Using a gradient based optimization algorithm, the distributed propulsion BWB aircraft was optimized and compared with a similarly optimized conventional BWB design. Both designs are for an 800 passenger, 0.85 cruise Mach number and 7000 nmi mission. The MDO results found that the distributed propulsion BWB aircraft has a 4% takeoff gross weight and a 2% fuel weight. Both designs have similar planform shapes, although the planform area of the distributed propulsion BWB design is 10% smaller. Through parametric studies, it was also found that the aircraft was most sensitive to the amount of savings in propulsive efficiency and the weight of the ducts used to divert the engine exhaust.
Ph. D.

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Dippold, Vance Fredrick III. « Numerical Assessment of the Performance of Jet-Wing Distributed Propulsion on Blended-Wing-Body Aircraft ». Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/34878.

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Conventional airliners use two to four engines in a Cayley-type arrangement to provide thrust, and the thrust from these engines is typically concentrated right behind the engine. Distributed propulsion is the idea of redistributing the thrust across most, or all, of the wingspan of an aircraft. This can be accomplished by using several large engines and using a duct to spread out the exhaust flow to form a jet-wing or by using many small engines spaced along the span of the wing. Jet-wing distributed propulsion was originally suggested by Kuchemann as a way to improve propulsive efficiency. In addition, one can envision a jet-wing with deflected jets replacing flaps and slats and the associated noise.

The purpose of this study was to assess the performance benefits of jet-wing distributed propulsion. The Reynolds-averaged, finite-volume, Navier-Stokes code GASP was used to perform parametric computational fluid dynamics (CFD) analyses on two-dimensional jet-wing models. The jet-wing was modeled by applying velocity and density boundary conditions on the trailing edges of blunt trailing edge airfoils such that the vehicle was self-propelled. As this work was part of a Blended-Wing-Body (BWB) distributed propulsion multidisciplinary optimization (MDO) study, two airfoils of different thickness were modeled at BWB cruise conditions. One airfoil, representative of an outboard BWB wing section, was 11% thick. The other airfoil, representative of an inboard BWB wing section, was 18% thick. Furthermore, in an attempt to increase the propulsive efficiency, the trailing edge thickness of the 11% thick airfoil was doubled in size. The studies show that jet-wing distributed propulsion can be used to obtain propulsive efficiencies on the order of turbofan engine aircraft. If the trailing edge thickness is expanded, then jet-wing distributed propulsion can give improved propulsive efficiency. However, expanding the trailing edge must be done with care, as there is a drag penalty. Jet-wing studies were also performed at lower Reynolds numbers, typical of UAV-sized aircraft, and they showed reduced propulsive efficiency performance. At the lower Reynolds number, it was found that the lift, drag, and pitching moment coefficients varied nearly linearly for small jet-flap deflection angles.

Master of Science

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