Dissertations / Theses: 'Aerospace engineers'

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Conlon, Craig Fertig. "A study of ergonomic risk factors and interventions among aerospace engineers." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1568065861&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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Sales, Hazel Eneida. "Engineering texts : a study of a community of aerospace engineers, their writing practices, and technical proposals." Thesis, University of Birmingham, 2002. http://etheses.bham.ac.uk//id/eprint/241/.

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This is a report of a six-year study of working and writing practices in an engineering environment. It is an investigation into a distinctive discourse community of design engineers conducted from an ethnographic perspective. It surveys the engineers’ attitudes towards writing and texts, and describes their distinctive writing practices, including collaborative writing. It shows them to have been acculturated into work attitudes, procedures, and a writing style which are at odds with actual demands made of them in the workplace. The engineering-lore about engineers being generally incompetent or indifferent writers is explored and, for the most part, debunked. The texts that design engineers write are identified, and it is shown that product design, the type of work activity that most engages and concerns the engineers, provides a common thread throughout all the documents considered. Particular attention is paid to proposals and executive summaries, since they give rise to specifications and requirements, all of which give most cause for concern to the engineers and the company. It is shown that proposals are ultimately persuasive in intent, in which engineers must convince the Customer of the superiority of their ‘solution’ over the proposal submissions from other companies. Pragmatism and problem-solving underpin the approach taken to proposal documents, the description and analysis of which is intended to be useful to the engineer writers themselves, and intended to reflect their collaborative writing practices. An analytical approach has been devised, based on information content, which is of potential use for diagnostic or evaluative purposes. Findings arising out the analysis suggest that the proposals and executive summaries written by design engineers comprise a selection of Information Components (ICs) drawn from a finite set of thirty-nine ICs. They indicate the existence of four major foci for proposal texts: three information-based, and one metadiscoursal. The results also seem to indicate that proposal writers may be focusing too much on product design in proposals to the detriment of other key information, which also contributes to the overall ‘solution’.

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Bethune, Mary. "Save That Thought| A Case Study of How Knowledge Is Transferred between Baby Boomers and Generation-X Aerospace Engineers." Thesis, City University of Seattle, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10828846.

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The current American workforce is at a crossroads due to the number of Baby Boomers either retiring or on the cusp of retirement. For many organizations, this cohort possesses knowledge and experiences that can be lost if this knowledge is not transferred before their departure from the organization. This ability to share knowledge is increasingly recognized both as a valuable asset for organizations and as a modern-day challenge for leaders. The purpose of this research was to explore the process of organizational knowledge sharing resulting from the Baby Boomers’ retirement. Using case study methodology and a single-stage sampling procedure, twelve participants were recruited to participate, and research questions were designed, to address how two generations of aerospace engineers describe their experiences with knowledge transfer and the strategies used to support such a transfer. Sources of information for this study were face-to-face, semi-structured interviews, organizational documents, and artifacts. Data were analyzed, generating codes and conceptual categories that eventually led to the emergence of the three themes of organizational knowledge transfer, promote knowledge sharing, and tacit and explicit knowledge. An analysis of these three themes resulted in three specific recommendations for action which were: (a) turning tacit knowledge into explicit knowledge, (b) creating knowledge sharing activities, and (c) developing purposeful leadership. Future researchers could explore management views of knowledge sharing and the impact on the organization.

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Ekman, Marcus. "Design Study of a Wing Rudder : Exploring the Possibility to Implement Additive Manufacturing." Thesis, Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-64522.

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Subtractive manufacturing are the most common methods in the aerospace industry to manufacture components. In these parts the buy to fly ratio is low and it needs accurate strengths analyses to static and dynamic loads especially were the different parts relate to each other with fasteners in the assembly work. Additive manufacturing has now been developed to be of such quality that the aerospace industry see the potential to use the technology in their production of parts. It has been possible to make them lighter, stronger and reduce the total amount of parts in an assembly. This mean probably some changes to the stakeholders in the process of their product development. Engineers who are working on the products will need to face the design aspects and restrictions with AM to choose the right component/sub-assemblies to convert to AM parts. This thesis will address the possibility to redesign a wing rudder and to get some knowledge about the engineer’s point of view of AM and how it may affect them. Today there are several aerospace industries adopting AM and get airworthy components to less critical parts as brackets but also parts in the engines as the fuel nozzle in an Airbus (Trimble, 2016). For larger parts, there have also been studies to use AM for example internal galley partition but the result is it will take too long time to print by todays machines. There are several different methods for AM and Powder Bed System is popular in the aerospace industry according to its geometrical correctness to the CAD model (Dordlofva, Lindwall, & Törlind, 2016). Commercial aircrafts industry starts to get harder regulations for their emissions to get lighter planes and less air resistance. AM open up the possibilities to meet these requirements by producing parts which was impossible to produce before. The design process for AM design today are not fully known yet, which leave a lot to imagination. There are general design rules on how to design for AM build but it does not necessary mean the part will be correctly built. There are several cost driven aspects with AM, the most expensive part is the print time but there are different aspects to. For example, CNC machining may be needed after the AM build and add cost for subtractive manufacturing. Interviews with engineer’s groups have been made to conduct their thoughts and knowledge of AM and how it may affect their work. Some uncertainties were mentioned and it was most focused on the process and the reliability of the finished part. The engineers think the design process will be almost the same and only change boundary conditions. To get ideas, a workshop was made with some design guidelines for development of different designs on the wing rudder and to bring positive and negative aspects to the design. An overall cost calculation was made for a few parts and the result shows that it is hard to compete with the design of the wing rudder today. The most important aspects for a success of AM is the print speed, qualified manufacturing processes and CAD software support for the engineers.
Flygindustrin använder sig främst av subtraktiv bearbetning i sin framställning av de olika komponenterna till ett flygplan. Det blir då ofta en väldigt låg grad av materialutnyttjande, endast några procent återstår av det inköpta utgångsmaterialet. Till det tillkommer monteringsarbete och noggranna hållfasthetsanalyser, både statisk och utmatningshållfasthet av sammanbyggda skarvar där fästelement är en del. Den additiva tillverkningen har nu utvecklats och visat sig inneha kvalitéer för att klara kraven som ställs i flygindustrin. Det kan göra detaljerna lättare, starkare och minska antalet komponenter i monteringsarbetet. Det kan innebära en hel del förändringar för olika intressenter som får börja tänka annorlunda. Ingenjörer som arbetar med produktframtagning kommer att ställas inför utmaningen att applicera denna teknik på lämpliga delar/delkonstruktioner. Detta examensarbetet undersöker möjligheten att designa ett vingroder till ett flygplan och bilda en uppfattning om ingenjörernas förtroende för additiv tillverkning samt hur det kommer påverka dem. Det finns idag flera flygindustrier som har påbörjat att ta fram flygvärdiga komponenter, framförallt mindre kritiska fästelement men även en del artiklar i motorer så som bränslemunstycke hos Airbus (Trimble, 2016). De har analyserat möjligheten att använda additiv tillverkning på större artiklar såsom inre kabinstruktur men har kommit fram till att det tar för lång tid att tillverka med dagens maskiner. Det finns flertalet olika additiva tillverkningsmetoder men den som står ut är pulverbäddskrivaren då den har en bättre geometrisk korrekthet gentemot CAD modellen (Dordlofva, Lindwall, & Törlind, 2016). Nya reglementen för utsläpp i den komersiella flygindustrin pressar företagen att bygga bättre flygplan som är lättare och därmed får mindre luftmotstånd. Designprocessen för additiv tillverkning är inte given då det inte finns några givna processer som täcker hela processen. Det finns generella design-riktlinjer i vad de olika maskinerna klarar av att bygga, men samtidigt är det ingen garanti att genom att följa dessa riktlinjer skapa en fungerande design. Det finns flera olika kostnadsdrivande aspekter med additiv tillverkning. Det som mest driver kostnaden idag är den låga skrivarhastigheten. Andra kosnadsdrivare är om det tillkommer efterarbete för att uppfylla toleranser eller få en korrekt / plan sammanfogningsyta. Arbetet har utförts med intervjuer av ingenjörsgrupper för att skapa en uppfatting om deras syn på additiv tillverkning och hur det skulle ändra deras arbete. En viss osäkerhet förekom men det berodde framförallt på osäkerheten för säkring av processen, dvs tillverkningsprocessen och att kunna vara säker på att detaljen håller måttet. De ansåg att designprocessen inte skulle förändras så mycket, utan bara att randvillkoren skulle ändras. Utifrån workshops och designriktlinjer har koncept tagits fram och utvärderats med för och nackdelar. En översiktlig kostnadskalkyl har gjorts som visar på att det blir svårt att designa roder som en större enhet för additiv tillvekning som är ekonomiskt jämförbart med dagens tillverkingsmetoder. De viktigaste framgångsfaktorerna för additiv tillverkning är ökad skrivarhastighet, kvalificering av tillverkningsprocesserna och CAD stöd för ingenjörerna.

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Collins, Michelle Louise. "Surface treatment for new engineered aerospace systems." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/surface-treatment-for-new-engineered-aerospace-systems(79c66e05-aaea-4dc3-bb8f-4d281ea1ea78).html.

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During this EngD project, two pigmented, anti-corrosion polymer/sol-gel hybrid coatings were developed with the aim of producing an eco-friendly alternative to conventional, toxic hexavalent chromate conversion and anodized anti-corrosion alloy treatments for the aircraft manufacturer; Airbus S.A.S. The polymer/sol-gel hybrid coatings were then tested and validated as anti-corrosion coatings on the AA2024-T3 aluminium aerospace alloy and in certain cases, their performance was compared against that of the hexavalent chromate benchmark (Alocrom 1200). The mechanisms of corrosion inhibition exhibited by the coatings were also studied in depth. The polymer/sol-gel hybrid coatings that were developed in this project are silane based and the first, designated as B2, has polyester-methacrylic functionality and the second, designated as CA/MM, has polyester-amide functionality. Certain inhibitor compounds which were incorporated in the polymer/sol-gel hybrid coatings were chosen by the split-cell technique. The microstructure and elemental compositions of the polymer/sol-gel hybrid coatings and of the AA2024-T3 aluminium alloy were determined by Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopic (SEM-EDS) analysis of the specimens. The anti-corrosion performance and the corrosion protection mechanisms of the polymer/sol-gel hybrid coatings were determined by salt-water and electrochemical testing of the coated alloy specimens. The thermal resistance of the polymer/sol-gel hybrid coatings was ascertained by thermogravimetric analysis (TGA) of the coatings. The polymer/sol-gel hybrid coatings were also analysed by Fourier Transform Infrared (FTIR), Micro-Raman and X-ray Photoelectron (XPS) spectroscopic techniques to determine whether the desired polymer and silane coating networks formed during coating processing. Anti-corrosion performance test results revealed that both polymer/sol-gel hybrid coatings are self-healing due to their ability to implement a precipitation mechanism of corrosion inhibition. Analysis of the polymer/sol-gel hybrid coatings by X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) after salt-water exposure suggested that the B2 coating precipitated the compound tungsten pyrophosphate, W(P2O7), within defects and that the CA/MM coating precipitated the compound iron carbide, Fe2C, within defects. However, anti-corrosion test results also shown that the anti-corrosion performance of the polymer/sol-gel hybrid coatings does not satisfy aerospace industry requirements. Therefore, it can be concluded that although the achievements of this project have not enabled Airbus to eliminate toxic chromium (VI) species from their operations, further optimisation of the polymer/sol-gel hybrid coatings developed during this project could potentially lead to a solution being found.

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Ling, Jack C. L. "Compressors for miniature unmanned aerospace propulsion systems." Phd thesis, School of Aerospace, Mechanical and Mechatronic Engineering, 2009. http://hdl.handle.net/2123/6430.

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Korak, Ghosh. "Model predictive control for civil aerospace gas turbine engines." Thesis, University of Sheffield, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595827.

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Kiker, Adam Paul. "Experimental Investigations of Mini-Pulsejet Engines." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-08112005-134914/.

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An experimental 8 cm pulsejet was developed using scaling laws from research on both 50 and 15 cm pulsejets. The 8 cm jet operates in three different inlet configurations?conventional, perpendicular, and rearward. The rearward configuration features inlets facing in the opposite direction of the flight path and develops the maximum net thrust. Using a high frequency pressure transducer, the operational frequency of the pulsejet was obtained by monitoring the combustion chamber pressure. It was found that in the rearward configuration, the operational frequency of the jet decreases with increasing inlet length. In addition, the combustion chamber peak pressure rise per cycle increases significantly if the exhaust diameter is reduced. Using information from the 8 cm pulsejet, a 4.5 cm pulsejet was developed and is operational.

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OVERMAN, NICHOLAS. "FLAMELESS COMBUSTION APPLICATION FOR GAS TURBINE ENGINES IN THE AEROSPACE INDUSTRY." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1163776616.

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Schoen, Michael Alexander. "Experimental Investigations in 15 Centimeter Class Pulsejet Engines." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-08082005-095911/.

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Testing is performed on the 15 centimeter class pulsejet engine in order to develop, study, and explore the operational characteristics. Valved and valveless operation, hydrogen and propane fuels, various fuel injection methods, and a range of geometric configurations are investigated for operational feasibility. The scaling capabilities of a valveless 15 centimeter class pulsejet of conventional design are studied by methodically varying inlet length, exit length, exit geometry, and inlet area to combustor area ratio (Ai/Ac). Engine performance is defined by measuring chamber pressure, internal gas temperatures, time-resolved thrust, operational frequency, and fuel flow rate. The scaling capability is characterized by the success of self-sustained combustion for each corresponding geometric configuration. Tail pipe length is found to be a function of valveless inlet length and may be further minimized by the addition of a diverging exit nozzle. Chemical kinetic times and Ai/Ac prove to be the two prominent controlling parameters in determining scaling behavior.

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Wilson, Andrew David. "Wear and fatigue studies of surface engineered ferrous and non-ferrous aerospace alloys." Thesis, University of Hull, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264952.

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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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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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Reichel, Jonathan R. "Parametric study of liquid fuel jet in crossflow at conditions typical of aerospace applications." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22590.

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Rubio, Mario A. "Microexplosions and Ignition Dynamics in Engineered Aluminum/Polymer Fuel Particles." Thesis, Purdue University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10268368.

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Aluminum particles are widely used as a metal fuel in solid propellants. However, poor combustion efficiencies and two-phase flow losses result due in part to particle agglomeration. Recently, engineered composite particles of aluminum (Al) with inclusions of polytetrafluoroethylene (PTFE) or low-density polyethylene (LDPE) have been shown to improve ignition and yield smaller agglomerates in solid propellants. Reductions in agglomeration were attributed to internal pressurization and fragmentation (microexplosions) of the composite particles at the propellant surface.

Here, we explore the mechanisms responsible for microexplosions in order to better understand the combustion characteristics of composite fuel particles. Single composite particles of Al/PTFE and Al/LDPE with diameters between 100–1200 μm are ignited on a substrate to mimic a burning propellant surface in a controlled environment using a CO₂ laser in the irradiance range of 78–7700 W/cm². The effects of particle size, milling time, and inclusion content on the resulting ignition delay, product particle size distributions, and microexplosion tendencies are reported. For example, particles with higher PTFE content (30 wt.%) had laser flux ignition thresholds as low as 77 W/cm², exhibiting more burning particle dispersion due to microexplosions compared to the other materials considered. Composite Al/LDPE particles exhibit relatively high ignition thresholds compared to Al/PTFE particles, and microexplosions were observed only with laser fluxes above 5500 W/cm² due to low LDPE reactivity with Al resulting in negligible particle self-heating. However, results show that microexplosions can occur for Al containing both low and high reactivity inclusions (LDPE and PTFE, respectively) and that polymer inclusions can be used to tailor the ignition threshold. This class of modified metal particles shows significant promise for application in many different energetic materials that use metal fuel.

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Cosher, Christopher R. "Detailed Analysis of Previous Data Relevant to Foreign Particle Ingestion by GasTurbine Engines and Application to Modern Engines." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461152408.

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Roberts, James W. "Further calculations of the performance of turbofan engines incorporating a wave rotor." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA240867.

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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, September 1990.
Thesis Advisor(s): Shreeve, Raymond P. Second Reader: Hobson, Garth V. "September 1990." Description based on title screen as viewed on December 18, 2009. DTIC Descriptor(s): Rotors, Turbofan Engines, Waves, Gases, Pressure, Ratios, Computer Programs, Cycles. DTIC Identifier(s): Wave Rotors, Rotors, Waves, Theses. Author(s) subject terms: Turbofan Engines, Turbofan engines with a Wave Rotor. Includes bibliographical references (p. 95-96). Also available in print.

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Staniszewski, Marcin. "Simulation of tri-axially braided composites half-cylinder behavior during balistic [sic] impact." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1177978645.

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Thesis (M.S.)--University of Akron, Dept. of Civil Engineering, 2007.
"May, 2007." Title from electronic thesis title page (viewed 4/28/2009) Advisor, Wieslaw K. Binienda; Committee members, Craig C. Menzemer, Ala Abbas; Department Chair, Wieslaw K. Binienda; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

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Miquel, Valentin. "Propellant Feeding System of a Liquid Rocket With Multiple Engines." Thesis, KTH, Rymdteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276460.

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Multiengine first stages are the new trend in recent rockets. Reusability and an oxygen/methane based engine complete this picture. ArianeGroup wants to develop its own rocket following these principles. This thesis presents the study of the feeding system for a seven Prometheus engine rocket. Several ways of connecting propellant tanks to engines were proposed and analyzed. Two configurations were selected and studied with more detail. One consists of a main feeding line which is then split in seven secondary lines. The other one adds one rank of pipes to reduce the number of feeding valves. Their performances were assessed according to classic space industry drivers. Furthermore, the impact of the two solutions on the efficiency of the tank was evaluated. CAD drawings and simulation models were made and could be a base for future work if one of the systems is chosen. The study shows that a falcon 9 like feeding system is performant in terms of mass and pressure losses but another cost-effective configuration is possible and gives good results.
Första stegen med flera motorer är den nya trenden i de senaste raketerna. Återanvändbart och en syre och metan-baserad motor kompletterar denna bild. ArianeGroup vill utveckla sin egen raket enligt dessa principer. Denna avhandling presenterar studien av drivmedelsrör för en sju Prometheus-motorraket. Flera sätt att ansluta drivmedelstankar till motorer föreslogs och analyserades. Två konfigurationer valdes ut och studerades mer detaljerat. En består av en huvudlinje som sedan delas upp i sju sekundära linjer som på SpaceX Falcon 9. Den andra lösningen lägger till en rang av rör för att minska antalet ventiler. Deras prestanda utvärderades först enligt klassiska kriterier för rymdindustrin. Dessutom utvärderades de två lösningarnas påverkan på tankens effektivitet. CAD-ritningar och simuleringsmodeller gjordes och kan vara en bas för framtida arbeten om ett av systemen väljs. Studien visar att ett Falcon 9-liknande konfiguration har bättre prestanda när det gäller massa och tryckförluster men en annan kostnadseffektiv konfiguration är möjlig och ger goda resultat.

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Ragozin, Konstantin. "Thrust Performance and Heat Load Modelling of Pulse Detonation Engines." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-82438.

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Pulse Detonation Engines (PDEs) are propulsion systems that use repeated detonations to generate thrust. Currently in early stages of development, PDEs have been theorised to have advantages over current deflagration based engines. Air-breathing PDEs could attain higher specific impulse values and operate at higher Mach numbers than today's air-breathing engines, while Pulse Detonation Rocket Engines (PDREs) could become a lighter, cheaper, and more reliable alternative to traditional rocket engines. There are still however, many technological hurdles to overcome before PDEs can be developed into practical propulsion systems, one major barrier being management of their immense heat loads. This thesis outlines the development of a numerical model for determining thrust performance and heat load characteristics of PDEs. The model is based on a set of analytical equations which characterise the gas dynamics inside the engine throughout it's cyclic process. Being numerically light -when compared to CFD analysis- the model allows for fast turnaround of results and the ability to sweep through parameters to determine optimum operating conditions to maximise engine performance and reduce heat load. In this study, the working principles of the model are described and it's outputs are validated against data from published experimental and numerical studies. The model is then used to conduct a comprehensive parametric study on the effects of various reactant combinations, operating conditions, and engine geometries on engine thrust, specific impulse and heat load. Lastly, a brief study is conducted on the feasibility of regenerative cooling for PDEs, using model outputs to determine if a heat balance can be achieved and the performance losses and complications that would result.

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ALLGOOD, DANIEL CLAY. "AN EXPERIMENTAL AND COMPUTATIONAL STUDY OF PULSE DETONATION ENGINES." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1095259010.

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Pakmehr, Mehrdad. "Towards verifiable adaptive control of gas turbine engines." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49025.

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This dissertation investigates the problem of developing verifiable stable control architectures for gas turbine engines. First, a nonlinear physics-based dynamic model of a twin spool turboshaft engine which drives a variable pitch propeller is developed. In this model, the dynamics of the engine are defined to be the two spool speeds, and the two control inputs to the system are fuel flow rate and prop pitch angle. Experimental results are used to verify the dynamic model of JetCat SPT5 turboshaft engine. Based on the experimental data, performance maps of the engine components including propeller, high pressure compressor, high pressure, and low pressure turbines are constructed. The engine numerical model is implemented using Matlab. Second, a stable gain scheduled controller is described and developed for a gas turbine engine that drives a variable pitch propeller. A stability proof is developed for a gain scheduled closed-loop system using global linearization and linear matrix inequality (LMI) techniques. Using convex optimization tools, a single quadratic Lyapunov function is computed for multiple linearizations near equilibrium and non-equilibrium points of the nonlinear closed-loop system. This approach guarantees stability of the closed-loop gas turbine engine system. To verify the stability of the closed-loop system on-line, an optimization problem is proposed which is solvable using convex optimization tools. Through simulations, we show the developed gain scheduled controller is capable to regulate a turboshaft engine for large thrust commands in a stable fashion with proper tracking performance. Third, a gain scheduled model reference adaptive control (GS-MRAC) concept for multi-input multi-output (MIMO) nonlinear plants with constraints on the control inputs is developed and described. Specifically, adaptive state feedback for the output tracking control problem of MIMO nonlinear systems is studied. Gain scheduled reference model system is used for generating desired state trajectories, and the stability of this reference model is also analyzed using convex optimization tools. This approach guarantees stability of the closed-loop gain scheduled gas turbine engine system, which is used as a gain scheduled reference model. An adaptive state feedback control scheme is developed and its stability is proven, in addition to transient and steady-state performance guarantees. The resulting closed-loop system is shown to have ultimately bounded solutions with a priori adjustable bounded tracking error. The results are then extended to GS-MRAC with constraints on the magnitudes of multiple control inputs. Sufficient conditions for uniform boundedness of the closed-loop system is derived. A semi-global stability result is proven with respect to the level of saturation for open-loop unstable plants, while the stability result is shown to be global for open-loop stable plants. Simulations are performed for three different models of the turboshaft engine, including the nominal engine model and two models where the engine is degraded. Through simulations, we show the developed GS-MRAC architecture can be used for the tracking problem of degraded turboshaft engine for large thrust commands with guaranteed stability. Finally, a decentralized linear parameter dependent representation of the engine model is developed, suitable for decentralized control of the engine with core and fan/prop subsystems. Control theoretic concepts for decentralized gain scheduled model reference adaptive control (D-GS-MRAC) systems is developed. For each subsystem, a linear parameter dependent model is available and a common Lyapunov matrix can be computed using convex optimization tools. With this control architecture, the two subsystems of the engine (i.e., engine core and engine prop/fan) can be controlled with independent controllers for large throttle commands in a decentralized manner. Based on this D-GS-MRAC architecture, a "plug and play" (PnP) technology concept for gas turbine engine control systems is investigated, which allows us to match different engine cores with different engine fans/propellers. With this plug and play engine control architecture, engine cores and fans/props could be used with their on-board subordinate controllers ready for integration into a functional propulsion system. Simulation results for three different models of the engine, including the nominal engine model, the model with a new prop, and the model with a new engine core, illustrate the possibility of PnP technology development for gas turbine engine control systems.

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Girardello, Carlo. "Optical Analysis of Plasma : Flame Emission in Cryogenic Rocket Engines." Thesis, Luleå tekniska universitet, Rymdteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76097.

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This thesis contains the results of optical flame emission measurements of the Vulcain 2.1engine and the plasma emission spectroscopy of the Lumen Project engine. The plume spectroscopyis analyzed, ordered and studied in detail to offer the best possible molecular composition.The main focus relied on the hydroxide radical, blue radiation and other moleculesanalysis of the intensities encountered during the tests. The plasma emission spectroscopy isfocused on the determination of the plasma temperature value in LIBS measurements. Thehydrogen plasma temperature determination of the local thermodynamic equilibrium, followedby the carbon and sequentially oxygen plasma is obtained. The quality of the LTE isto be determined to judge the truthworthness of the determined temperatures. Both the testsare analyzed thanks to the use of spectrographs, cameras and dedicated software for opticalapplications. The results related to the Vulcain 2.1 LOX/LH2 engine showed the evolutionof the plume in different ROF or pressure variations. Furthermore, the results of the LumenProject LOX/methane engine led to the determination of the plasma temperatures and a firstestimation of the LTE quality.
Die vorliegende Arbeit präsentiert die Ergebnisse der Abgasstrahlspektroskopie des H2/LOXVulcain 2.1 Triebwerks und der Zündplasma Spektroskopie des CH4/LOX Triebwerks desLUMEN Projektes. Die Abgasstrahlspektroskopie wurde analysiert und im Detail untersuchtum die am besten passende molekulare Zusammensetzung herauszuarbeiten. DasHauptaugenmerk liegt dabei auf dem Hydroxyl- Radikal, der Blauen Strahlung und molekularerIntensitätsanalyse. Bei der Zündplasmaanalyse liegt der Fokus auf der Bestimmungdes LTE Zustands (Lokales thermodynamisches Gleichgewicht) in LIBS. Die Temperaturdes Wasserstoff-, Kohlenstoff und Sauerstoffplasmas wird herangezogen, um die Qualitätdes LTE Zustands zu beurteilen. Für die Testdurchführung wurden Spektrographen, Kamerasund bestimmte Auswertungstools für optische Anwendungen benutzt. Das Verhaltendes Vulcain 2.1 Abgasstrahls abhängig von verschiedenen ROF und Druckstufen ist in denErgebnissen beschrieben. Für das LUMEN Triebwerk konnten erste Zündplasmatemperaturenbestimmt werden und geben einen Rückschluss auf die Qualität des LTE.

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Benyo, Theresa Louise. "Analytical and computational investigations of a magnetohydrodynamics (MHD) energy-bypass system for supersonic gas turbine engines to enable hypersonic flight." Thesis, Kent State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3618922.

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Historically, the National Aeronautics and Space Administration (NASA) has used rocket-powered vehicles as launch vehicles for access to space. A familiar example is the Space Shuttle launch system. These vehicles carry both fuel and oxidizer onboard. If an external oxidizer (such as the Earth's atmosphere) is utilized, the need to carry an onboard oxidizer is eliminated, and future launch vehicles could carry a larger payload into orbit at a fraction of the total fuel expenditure. For this reason, NASA is currently researching the use of air-breathing engines to power the first stage of two-stage-to-orbit hypersonic launch systems. Removing the need to carry an onboard oxidizer leads also to reductions in total vehicle weight at liftoff. This in turn reduces the total mass of propellant required, and thus decreases the cost of carrying a specific payload into orbit or beyond. However, achieving hypersonic flight with air-breathing jet engines has several technical challenges. These challenges, such as the mode transition from supersonic to hypersonic engine operation, are under study in NASA's Fundamental Aeronautics Program.

One propulsion concept that is being explored is a magnetohydrodynamic (MHD) energy- bypass generator coupled with an off-the-shelf turbojet/turbofan. It is anticipated that this engine will be capable of operation from takeoff to Mach 7 in a single flowpath without mode transition. The MHD energy bypass consists of an MHD generator placed directly upstream of the engine, and converts a portion of the enthalpy of the inlet flow through the engine into electrical current. This reduction in flow enthalpy corresponds to a reduced Mach number at the turbojet inlet so that the engine stays within its design constraints. Furthermore, the generated electrical current may then be used to power aircraft systems or an MHD accelerator positioned downstream of the turbojet. The MHD accelerator operates in reverse of the MHD generator, re-accelerating the exhaust flow from the engine by converting electrical current back into flow enthalpy to increase thrust. Though there has been considerable research into the use of MHD generators to produce electricity for industrial power plants, interest in the technology for flight-weight aerospace applications has developed only recently.

In this research, electromagnetic fields coupled with weakly ionzed gases to slow hypersonic airflow were investigated within the confines of an MHD energy-bypass system with the goal of showing that it is possible for an air-breathing engine to transition from takeoff to Mach 7 without carrying a rocket propulsion system along with it. The MHD energy-bypass system was modeled for use on a supersonic turbojet engine. The model included all components envisioned for an MHD energy-bypass system; two preionizers, an MHD generator, and an MHD accelerator. A thermodynamic cycle analysis of the hypothesized MHD energy-bypass system on an existing supersonic turbojet engine was completed. In addition, a detailed thermodynamic, plasmadynamic, and electromagnetic analysis was combined to offer a single, comprehensive model to describe more fully the proper plasma flows and magnetic fields required for successful operation of the MHD energy bypass system.

The unique contribution of this research involved modeling the current density, temperature, velocity, pressure, electric field, Hall parameter, and electrical power throughout an annular MHD generator and an annular MHD accelerator taking into account an external magnetic field within a moving flow field, collisions of electrons with neutral particles in an ionized flow field, and collisions of ions with neutral particles in an ionized flow field (ion slip). In previous research, the ion slip term has not been considered.

The MHD energy-bypass system model showed that it is possible to expand the operating range of a supersonic jet engine from a maximum of Mach 3.5 to a maximum of Mach 7. The inclusion of ion slip within the analysis further showed that it is possible to 'drive' this system with maximum magnetic fields of 3 T and with maximum conductivity levels of 11 mhos/m. These operating parameters better the previous findings of 5 T and 10 mhos/m, and reveal that taking into account collisions between ions and neutral particles within a weakly ionized flow provides a more realistic model with added benefits of lower magnetic fields and conductivity levels especially at the higher Mach numbers. (Abstract shortened by UMI.)

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DRENSKY, GEORGE K. "EXPERIMENTAL INVESTIGATION OF COMPOSITE MATERIAL EROSION CHARACTERISTICS UNDER CONDITIONS ENCOUNTERED IN TURBOFAN ENGINES." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1178118863.

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Ramunno, Michael Angelo. "Control Optimization of Turboshaft Engines for a Turbo-electric Distributed Propulsion Aircraft." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587657623577243.

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Avram, Remus C. "A UNIFIED NONLINEAR ADAPTIVE APPROACH FOR THE FAULT DIAGNOSIS OF AIRCRAFT ENGINES." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1332784433.

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28

Gillaugh, Daniel L. "As-Manufactured Modeling of a Mistuned Turbine Engine Compressor Evaluated Against Experimental Approaches." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1557245676336916.

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Cornwell, Michael. "Causes of Combustion Instabilities with Passive and Active Methods of Control for practical application to Gas Turbine Engines." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307323433.

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30

Lim, Christopher Say Liang. "Analysis and management of temperature fields in F1 cars." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:0de2a35c-a781-4211-9399-c72ab3d8ad18.

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This thesis investigates the broad subject of thermal management problems currently encountered in Formula One race car design. A computationally economical tool, based on linear superposition, for predicting the temperature field arising from a set of thermal and inlet velocity boundary conditions was developed. Using a set of base analyses, the research showed that it is possible to superpose and scale these results in order to predict the temperature field for differing sets of boundary conditions. This method was shown to have a significant speed advantage over typical computational simulations. An experimental facility was designed and built to provide validation for aspects of the linear superposition approach. A method of measuring the cylinder wall heat flux has been developed using thin film gauge technology. The resulting sensor was designed to fit the mounting of existing instrumentation in order to avoid requiring large scale modifications to existing test facilities. The design makes use of modern rapid prototyping techniques in order to meet this mounting requirement and to provide a novel solution to routing the signal from the thin film gauge. In addition, the research investigated a method for predicting the cylinder wall temperature in real-time. The cylinder wall is subject to heat fluxes from in-cylinder gases during the engine cycle on the inner face and the effect of the coolant jacket on the outer face. Two separate methods were used to process these thermal boundary conditions respectively, before being superposed in order to form the whole solution. The computation time of the method is characterised in order to demonstrate its feasibility for real-time operation.

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31

Paolucci, Lorenzo. "High efficiency low temperature combustion in compression ignition engines for automotive and aeronautical applications." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.

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Internal combustion engines are increasingly subject to ever more stringent and severe Euro-legislations about pollutants emissions in terms of nitrogen oxide, carbon monoxide, unburned hydrocarbons and soot. In last years, thanks to advanced after treatment systems and technological innovations, emission have been improved but, due to even higher costs and complexity of such systems and in a view of further emissions restrictions, advanced combustion methods leading to cleaner and improved efficiency combustion are under investigation. A possible path to follow in order to met requirements on lower emissions, is relative to so called low temperature combustion: a group of innovative combustion methods which by exploiting lean and premixed combustion decreases significantly flame temperature which is mainly responsible for nitrogen oxide production. This work of thesis focus on preliminary study, development and experimental testing of a low temperature combustion strategy, namely "gasoline direct compression ignition" also known as "GDCI".

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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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33

de, Oliveira Mónica Sandra Abrantes. "The use of air assisted atomised water spray systems for controlled cooling of high temperature forgings." Thesis, University of South Wales, 1999. https://pure.southwales.ac.uk/en/studentthesis/the-use-of-air-assisted-atomised-water-spray-systems-for-controlled-cooling-of-high-temperature-forgings(46c7cbe3-4bc5-443a-b9ea-de43af504fcc).html.

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This thesis describes the work undertaken by the author in collaboration with Wyman-Gordon Forgings, USA, to assist in the development of a cooling system,based on air assisted atomised water sprays primarily for the quenching of aerospace components from high temperatures. The mechanical properties of forgings used in aircraft engines depend on the rate of cooling from the heat treatment solution temperature. It is well known that water quenching produces high cooling rate. Although, the severity of the quench can sometimes produce unacceptable distortion and high residual stresses in the component. For this reason water quenching is only used when a high cooling rate is definitely needed and it is often replaced by a less severe oil quench. However, over the last 10 years the trend to reduce manufacturing costs has led to the forging of parts that are closer to the net shape. In these cases even oil quenching can lead to residual stresses being developed that result in difficulties during the final machining of the engine component. Forced air cooling has been adopted in problem cases where the part is thin enough to attain the desired cooling rate. In many instances, however, the component is of intermediate size or varying in cross section and fan cooling cannot provide the cooling rate which is needed to obtain the desired mechanical properties, whilst oil quenching produces an unacceptable level of residual stresses. The use of air assisted atomised water sprays can provide heat transfer coefficients whose values lie between those for air cooling and oil quenching. Another advantage is that control of the air pressure enables the spray nozzle to operate with a much wider range of water flow rates so that the cooling rate can be readily controlled over the range. This study describes the investigation of the heat transfer characteristics of air assisted atomised water sprays to quench aeroengine components from temperatures of approximately 850°C. New data were obtained at high temperatures for air assisted atomised water sprays operating over a wide range of water mass fluxes, (8.01>w 0 >0kg/m2 .s). In practice the geometry of a component can be complex in shape. Therefore an investigation was also carried out into the application of spray cooling on recessed surfaces. It was found that the surface recess contributes significantly to the reduction in the rate of heat transfer at low and high water mass fluxes, but had little effect at intermediate flow rates. Pulsed sprays were investigated and proposed as a means of controlling heat transfer coefficients for both plane and recessed surfaces. The use of a pulsed spray makes it possible to control the amount of water impacting on a surface per second. It was found that "water off periods of 5 and 10 seconds resulted in a reduction in heat transfer coefficients at low temperatures and also reduced considerably the differences in cooling previously observed between plane and recessed surfaces. A finite element code was used to predict the residual stresses produced in a forged component for a range of spray parameters, and spray arrangements. The data were compared with cooling rates and stress patterns produced by both air and oil quenching. It was found that spray cooling resulted in cooling rates which met the mechanical property specification and provided residual stresses lower than those obtained during oil quenching. Furthermore, simulations of residual stress formation using two different spray arrangements in a typical forging indicated that spray non uniformities can substantially disturb the resultant residual stress patterns which could result in less predictable distortions during final machining. The study of spray cooling presented here suggests that the use of air assisted atomised water sprays has considerable potential and could provide the required cooling rate for individual forgings.

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Zinnecker, Alicia M. "Modeling for Control Design of an Axisymmetric Scramjet Engine Isolator." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354215841.

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35

Léonard, Pauline. "Sustainability assessment of composites in aero-engine components." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75369.

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Environmental issues such as climate change are leading to important sustainability challenges in the aerospace industry. Composites are light materials that are extensively used to replace metals and reduce the aircraft weight, the goal being to decrease the fuel consumption in flight and limit the emission of greenhouse gases. However, these high performance materials are associated with a complex supply chain including energy-consuming processes. Most of the decommissioned composite products are currently landfilled and nothing proves that the weight reduction allowed by these materials compensates those negative aspects. The purpose of this master thesis is to determine if the introduction of composites in aero-engines can be sustainable and how it can be achieved. To do so, three polymer-matrix composite components from GKN Aerospace have been studied and compared with their metallic baseline from environmental, social and economic perspectives. Several options for materials selection, manufacturing processes and recycling possibilities have been investigated in the same way. The assessment on GKN Aerospace’s components showed that the weight savings provided by composites have a strong and positive influence on their sustainability. Component B shows the best results: with 16% of weight savings with composites versus the titanium baseline, it appears clearly that the composite version is the most sustainable one. Component A2 composite version also provides interesting weight savings (14%) but has an aluminum baseline, which makes the composite component more sustainable in some aspects but not all of them, especially economically speaking. Finally, for component A1, the composite version, which does not provide weight savings, is more economically feasible, but quite tight with the titanium baseline on environmental and social aspects. Therefore, it appears that composite components are more likely to be sustainable if they provide significant weight reduction and if the baseline is titanium. A few strategies would merit attention to make future composite components more sustainable. On the one hand, using thermoplastic composites have potential to reduce the environmental, social and economic impact. In fact, these materials can be fully recycled and reused, present less risks to handle and can be produced for a lower cost. Nevertheless, the knowledge on these materials is more limited than on thermoset composite and the implementation of such a solution will take time. On the second hand, introducing composite recycling processes in the products lifecycle can increase a lot the sustainability of composite components. The manufacturing scrap and the decommissioned products can both be recycled in order to reduce the environmental impact and generate benefits by re-using or selling the recycled material.

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Perovšek, Jaka. "Ray Tracing and Spectral Modelling of Excited Hydroxyl Radiation from Cryogenic Flames in Rocket Combustion Chambers." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-71277.

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A visualisation procedure was developed which predicts excited hydroxyl (OH*) radiation from the Computational Fluid Dynamics (CFD) solutions of cryogenic hydrogen-oxygen rocket flames. The model of backward ray tracing through inhomogeneous media with a continuously changing refractive index was implemented. It obtains the optical paths of light rays that originate in the rocket chamber, pass through the window and enter a simulated camera. Through the use of spectral modelling, the emission and absorption spectra eλ and κλ are simulated on the ray path from information about temperature, pressure and concentration of constituent species at relevant points. By solving a radiative transfer equation with the integration of emission and absorption spectra along the ray line-by-line, a spectral radiance is calculated, multiplied with the spectral filter transmittance and then integrated into total radiance. The values of total radiances at the window edge are visualised as a simulated 2D image. Such images are comparable with the OH* measurement images. The modelling of refraction effects results in up to 20 % of total radiance range absolute difference compared to line-of-sight integration. The implementation of accurate self-absorption corrects significant over-prediction, which occurs if the flame is assumed to be optically thin. Modelling of refraction results in images with recognisable areas where the effect of a liquid oxygen (LOx) jet core can be observed, as the light is significantly refracted. The algorithm is parallelised and thus ready for use on big computational clusters. It uses partial pre-computation of spectra to reduce computational effort.

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Loughnane, Gregory Thomas. "A Framework for Uncertainty Quantification in Microstructural Characterization with Application to Additive Manufacturing of Ti-6Al-4V." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1441064431.

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38

Kratz, Jonathan L. "Robust Control of Uncertain Input-Delayed Sample Data Systems through Optimization of a Robustness Bound." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429149093.

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39

Ahlefelder, Sebastian. "Kraftstoffverbrauch durch Entnahme von Zapfluft und Wellenleistung von Strahltriebwerken." Aircraft Design and Systems Group (AERO), Department of Automotive and Aeronautical Engineering, Hamburg University of Applied Sciences, 2006. http://d-nb.info/1179514394.

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Zapfluft und Wellenleistung wird den Triebwerken entnommen, um die Energie für beispielsweise die Kraftstoffpumpen, das Inflight Entertainment oder die Flügelvorderkantenenteisung zu erzeugen. Diese Energiegenerierung, hat einen Anstieg des Kraftstoffverbrauches zur Folge. Es hat sich herausgestellt, dass die Stelle der Zapfluftentnahme einen starken Einfluss auf den Gradienten des Brennstoffverbrauches hat. Das Projekt beschäftigt sich mit zwei- und dreiwelligen Turbofantriebwerken und untersucht an ihnen, die Effekte der Leistungsnahmen. Als Simulationssoftware wurde GasTurb 8.0 eingesetzt und auf die integrierten Triebwerkskonfigurationen zurückgegriffen. Ziel der Arbeit ist die Ermittlung einer mathematischen Beziehung zur Berechnung des zusätzlichen Kraftstoffmassenstromes infolge einer Zapfluft- oder Wellenleistungsentnahme. So stellt sich die Frage, welche Triebwerksparameter dafür berücksichtigt werden müssen. Eine Wellenleistungsentnahme verursacht beispielsweise einen linearen Anstieg des spezifischen Kraftstoffverbrauches. Ist diese Zunahme, identisch mit der einer Zapfluftentnahme? Am Ende der Kapitel werden die Ergebnisse mit Literaturwerten verglichen und versucht Tendenzen zu erkennen bzw. bestehende zu erhärten.

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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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(6636134), Kimberly Anne Quilang Rink. "Lessons Learned in the Space Sector: An Interactive Tool to Disseminate Lessons Learned to Systems Engineers." Thesis, 2019.

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Organizations, like individuals, are expected to learn from their mistakes. Companies that successfully rely on past knowledge to inform programmatic decisions use knowledge management tools to capture and disseminate this information, often in the form of lessons learned databases. However, past mistakes continue to happen in the aerospace industry, including NASA. Although NASA has taken measures to stress the importance of lessons learned in organizational culture, relatively little work has been done to develop the user interface of their lessons learned database. Encouraging engineers to review lessons only goes so far when the interface itself is outdated and difficult to use. We propose that an interactive network tool is an effective way to disseminate lessons learned to novice systems engineers.

In this thesis, I begin by developing a model to represent spacecraft anomaly narratives and applying this model to the Jet Propulsion Laboratory’s publicly available lessons learned database. I then create an interactive network tool and populate it with the set of modeled lessons. Then, I design an experiment to determine how novice engineers use two different knowledge management tools—the interactive network and the NASA database. I use transcripts of users’ thought processes, verbalized to me during the experiment, to create a mental model of how users with access to knowledge management tools respond to engineering scenarios. From the mental model, I identify the functional strengths and weakness of both the interactive network and the NASA database. Finally, I discuss the results of the experiment and recommend future improvements to the interactive network tool.

We found that the interactive network was a better resource for users to make connections between topics, and that the NASA database was a better resource for users to search for specific information. Using the interactive network over the NASA database correlated with an increase in performance for the majority of the experiment, but data we collected do not provide enough evidence for us to conclude that the interactive network is a better dissemination tool than the NASA database in all scenarios. We found that receiving lessons learned from either of the tools takes time because each tool’s functionality elicits new tasks from the user. Finally, we found that the top performers in the experiment used each of the tool’s strongest features.

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(5929472), Diane C. Aloisio. "Lessons from Systems Engineering Failures: Determining Why Systems Fail, the State of Systems Engineering Education, and Building an Evidence-Based Network to Help Systems Engineers Identify and Fix Problems on Complex Projects." Thesis, 2019.

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As the complexity of systems increases, so does what can go wrong with them. For example, the United States Air Force selected McDonnell Douglas’ design for the F-15 Eagle fighter aircraft in 1967 and the aircraft’s first test flight was in 1972, 5 years later. In contrast, the US military selected Lockheed Martin as one of two companies to develop the F-35 Lightning II in 1997 and its first flight was in 2006, 9 years later, and the first production aircraft had its first flight in 2011, 14 years after the selection. This complex program’s problems have been well-documented by the U.S. Government Accountability Office (GAO) and have contributed to the project’s long lead time and skyrocketing budget. GAO reports on other military projects reveal that problems the F-35 project has experienced are shared among all of these projects. In this dissertation I posit that similar problems plague all complex systems engineering projects and that a combination of these problems may lead to negative consequences, such as budget and schedule exceedances, quality concerns, not achieving mission objectives, as well as accidents resulting in loss of human life.

Accidents, or unexpected events resulting in loss, have been well-studied over time and we currently have sophisticated theories that help explain how they occur. The leading theory is that most accidents are a result of an accumulation of “mundane” errors at an organization, and that these errors are similar across industries. However, these mundane errors, such as failing to follow procedures and poorly training personnel, occur in all companies, such as companies that design and manufacture military aircraft. My theory is that these mundane errors accumulate in all organizations and result in many different kinds of systems engineering failures, including failures traditionally referred to as “accidents” that result in loss of life, as well as other types of failures which I refer to as “project failures”.

What can be learned from these systems engineering failures? In this dissertation, I begin by mining publicly-available reports to determine whether seemingly dissimilar failures, accidents and project failures, share common causes. I then explain the similarities and dissimilarities between these causes and provide examples from the failures I studied. To help provide systems engineers with actionable advice on these common causes, I describe how I linked the causes to recommendations from accident reports in a cause-recommendation network. I then discuss the results of interviews I held with systems engineers to determine whether the problems I identified in past failures occur in similar ways to the problems they have encountered on their projects. I also discuss the criticisms these systems engineers have about systems engineering education based on the tasks their newly-hired systems engineers struggle with. I explain how I used what I learned about problems in systems engineering that lead to failures to develop survey questions designed to gauge whether systems engineering education at Purdue prepares students to identify and fix these problems. Then, to help systems engineers learn from the data I collected and solve the problems they encounter on their projects, I describe how I built an interactive, web-based tool that presents expert advice on systems engineering failures. I finally explain the results from feedback I received from experts and novices in systems engineering to determine whether this tool could be useful for engineers in this context.

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43

Howard, Chris Allen. "From engineer to engineer manager a qualitative study of experiences, challenges, and individual transitions for engineering managers in aerospace companies /." 2003. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-308/index.html.

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44

Fischbach, Sean Robert. "Streaming Effects in Liquid Injection Rocket Engines with Transverse Mode Oscillations." 2007. http://trace.tennessee.edu/utk_graddiss/168.

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This research is an analytical investigation of wave interactions in a simulated liquid rocket engine with uniform injection imposed at the faceplate. Of significant interest are the secondary nonlinear flows, particularly acoustic streaming, induced by transverse wave impingement over the engine injector surface. The corresponding cylindrical chamber has a small length-to-diameter ratio with respect to solid and hybrid rockets. Given their low chamber aspect ratios, liquid thrust engines are known to experience severe tangential and radial oscillation modes more often than longitudinal ones. Experimental evidence demonstrates the production of large peak-to-trough amplitude flow oscillations along with the development of a strong central vortex structure in many unstable liquid engines. These phenomena are accompanied by elevated heat transfer to the injector faceplates, strong roll torques and chamber over pressurization. In order to model this behavior, tangential and radial waves are superimposed onto a basic mean-flow model that consists of a steady, uniform axial velocity throughout the chamber. Considerable effort is given to correctly satisfy the no-slip condition at the chamber’s injector face. The viscous boundary layer used to satisfy the no-slip condition is the location at which acoustic streaming develops. Sidewall boundary layers that develop at the lateral wall are not considered, being inconsequential to the flow in the vicinity of the headwall. Using perturbation tools, both potential and viscous flow equations are linearized in the pressure wave amplitude and solved to the second order. The effects of the headwall Mach number are leveraged as well. While the potential flow analysis does not predict any acoustic streaming effects, the viscous solution carried out to the second-order approximation gives rise to steady secondary flow patterns near the headwall. These axisymmetric, steady contributions to the tangential and radial traveling waves are induced by the convective flow motion through interactions with inertial and viscous forces. Suppressing either the convective terms or viscosity at the headwall can lead to spurious solutions that are free from streaming. In the present research, streaming is initiated at the headwall, within the boundary layer, and extends throughout the chamber. The study suggests that nonlinear streaming effects of tangential and radial waves inside a cylinder with headwall injection act to alter the outer solution. As a result of streaming, the radial wave velocities are intensified in one half of the domain and reduced in the opposite half at any instant of time. Similarly, the tangential wave velocities are either enhanced or weakened in two opposing sectors that are at a 90 degree angle to the radial velocity counterparts. The second-order viscous solution that is obtained clearly displays both an oscillating and a steady flow component. It is found that the steady contribution due to streaming can potentially promote the development of large amplitude steepened wave forms. The delineation of this mechanism is crucial for the advancement of analytical tools employed in the prediction of combustion instability. In the present study, streaming is examined in the context of traveling transverse waves. Extending the analysis to standing wave motion is carried out and reported in a straightforward fashion.

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Davis, Robert Benjamin. "Techniques to Assess Acoustic-Structure Interaction in Liquid Rocket Engines." Diss., 2008. http://hdl.handle.net/10161/601.

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Acoustoelasticity is the study of the dynamic interaction between elastic structures and acoustic enclosures. In this dissertation, acoustoelasticity is considered in the context of liquid rocket engine design. The techniques presented here can be used to determine which forcing frequencies are important in acoustoelastic systems. With a knowledge of these frequencies, an analyst can either find ways to attenuate the excitation at these frequencies or alter the system in such a way that the prescribed excitations do result in a resonant condition. The end result is a structural component that is less susceptible to failure. The research scope is divided into three parts. In the first part, the dynamics of cylindrical shells submerged in liquid hydrogen (LH₂) and liquid oxygen (LOX) are considered. The shells are bounded by rigid outer cylinders. This configuration gives rise to two fluid-filled cavities: an inner cylindrical cavity and an outer annular cavity. Such geometries are common in rocket engine design. The natural frequencies and modes of the fluid-structure system are computed by combining the rigid wall acoustic cavity modes and the in vacuo structural modes into a system of coupled ordinary differential equations. Eigenvalue veering is observed near the intersections of the curves representing natural frequencies of the rigid wall acoustic and the in vacuo structural modes. In the case of a shell submerged in LH₂, system frequencies near these intersections are as much as 30% lower than the corresponding in vacuo structural frequencies. Due to its high density, the frequency reductions in the presence of LOX are even more dramatic. The forced responses of a shell submerged in LH₂ and LOX while subject to a harmonic point excitation are also presented. The responses in the presence of fluid are found to be quite distinct from those of the structure in vacuo. In the second part, coupled mode theory is used to explore the fundamental features of acoustoelastic systems. The result is the development of relatively simple techniques that allow analysts to make informed decisions concerning the importance of acoustic-structure coupling without resorting to more time consuming and complex methods. In this part, a new nondimensional parameter is derived to quantify the fundamental strength of a particular acoustic-structure interaction irrespective of material and fluid properties or cavity size. It is be shown that, in some cases, reasonable approximations of the coupled acoustic-structure frequencies can be calculated without explicit knowledge of the uncoupled component mode shapes. Monte Carlo simulations are performed to determine the parameter values over which the approximate coupled frequency expressions are accurate. General observations concerning the forced response of acoustoelastic systems are then made by investigating the response of a simplified two mode system. The third part of this research discusses the implementation of a component mode synthesis (CMS) technique for use with geometrically complex acoustoelastic systems. The feasibility of conceptually similar techniques was first demonstrated over 30 years ago. Since that time there have been remarkable advancements in computational methods. It is therefore reasonable to question the extent to which CMS remains a computationally advantageous approach for acoustoelastic systems of practical interest. This work demonstrates that relative to the most recent release of the popular finite element software package, ANSYS, CMS techniques have a significant computational advantage when the forced response of an acoustoelastic system is of interest. However, recent improvements to the unsymmetric eigensolver available in ANSYS have rendered CMS a less efficient option when calculating system frequencies and modes. The CMS technique is then used to generate new results related to geometrically complex acoustoelastic systems.
Dissertation

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46

Maity, Arnab. "Optimal Guidance Of Aerospace Vehicles Using Generalized MPSP With Advanced Control Of Supersonic Air-Breathing Engines." Thesis, 2012. https://etd.iisc.ac.in/handle/2005/2550.

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A new suboptimal guidance law design approach for aerospace vehicles is proposed in this thesis, followed by an advanced control design for supersonic air-breathing engines. The guidance law is designed using the newly developed Generalized Model Predictive Static Programming (G-MPSP), which is based on the continuous time nonlinear optimal control framework. The key feature of this technique is one-time backward propagation of a small-dimensional weighting matrix dynamics, which is used to update the entire control history. This key feature, as well as the fact that it leads to a static optimization problem, lead to its computational efficiency. It has also been shown that the existing model predictive static programming (MPSP), which is based on the discrete time framework, is a special case of G-MPSP. The G-MPSP technique is further extended to incorporate ‘input inequality constraints’ in a limited sense using the penalty function philosophy. Next, this technique has been developed also further in a ‘flexible final time’ framework to converge rapidly to meet very stringent final conditions with limited number of iterations. Using the G-MPSP technique in a flexible final time and input inequality constrained formulation, a suboptimal guidance law for a solid motor propelled carrier launch vehicle is successfully designed for a hypersonic mission. This guidance law assures very stringent final conditions at the injection point at the end of the guidance phase for successful beginning of the hypersonic vehicle operation. It also ensures that the angle of attack and structural load bounds are not violated throughout the trajectory. A second-order autopilot has been incorporated in the simulation studies to mimic the effect of the inner-loops on the guidance performance. Simulation studies with perturbations in the thrust-time behaviour, drag coefficient and mass demonstrate that the proposed guidance can meet the stringent requirements of the hypersonic mission. The G-MPSP technique in a fixed final time and input inequality constrained formulation has also been used for optimal guidance of an aerospace vehicle propelled by supersonic air-breathing engine, where the resulting thrust can be manipulated by managing the fuel flow and nozzle area (which is not possible in solid motors). However, operation of supersonic air-breathing engines is quite complex as the thrust produced by the engine is a result of very complex nonlinear combustion dynamics inside the engine. Hence, to generate the desired thrust, accounting for a fairly detailed engine model, a dynamic inversion based nonlinear state feedback control design has been carried out. The objective of this controller is to ensure that the engine dynamically produces the thrust that tracks the commanded value of thrust generated from the guidance loop as closely as possible by regulating the fuel flow rate. Simultaneously, by manipulating throat area of the nozzle, it also manages the shock wave location in the intake for maximum pressure recovery with sufficient margin for robustness. To filter out the sensor and process noises and to estimate the states for making the control design operate based on output feedback, an extended Kalman filter (EKF) based state estimation design has also been carried out and the controller has been made to operate based on estimated states. Moreover, independent control designs have also been carried out for the actuators so that their response can be faster. In addition, this control design becomes more challenging to satisfy the imposed practical constraints like fuel-air ratio and peak combustion temperature limits. Simulation results clearly indicate that the proposed design is quite successful in assuring the desired performance of the air-breathing engine throughout the flight trajectory, i.e., both during the climb and cruise phases, while assuring adequate pressure margin for shock wave management.

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47

Maity, Arnab. "Optimal Guidance Of Aerospace Vehicles Using Generalized MPSP With Advanced Control Of Supersonic Air-Breathing Engines." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2550.

Full text

Abstract:

A new suboptimal guidance law design approach for aerospace vehicles is proposed in this thesis, followed by an advanced control design for supersonic air-breathing engines. The guidance law is designed using the newly developed Generalized Model Predictive Static Programming (G-MPSP), which is based on the continuous time nonlinear optimal control framework. The key feature of this technique is one-time backward propagation of a small-dimensional weighting matrix dynamics, which is used to update the entire control history. This key feature, as well as the fact that it leads to a static optimization problem, lead to its computational efficiency. It has also been shown that the existing model predictive static programming (MPSP), which is based on the discrete time framework, is a special case of G-MPSP. The G-MPSP technique is further extended to incorporate ‘input inequality constraints’ in a limited sense using the penalty function philosophy. Next, this technique has been developed also further in a ‘flexible final time’ framework to converge rapidly to meet very stringent final conditions with limited number of iterations. Using the G-MPSP technique in a flexible final time and input inequality constrained formulation, a suboptimal guidance law for a solid motor propelled carrier launch vehicle is successfully designed for a hypersonic mission. This guidance law assures very stringent final conditions at the injection point at the end of the guidance phase for successful beginning of the hypersonic vehicle operation. It also ensures that the angle of attack and structural load bounds are not violated throughout the trajectory. A second-order autopilot has been incorporated in the simulation studies to mimic the effect of the inner-loops on the guidance performance. Simulation studies with perturbations in the thrust-time behaviour, drag coefficient and mass demonstrate that the proposed guidance can meet the stringent requirements of the hypersonic mission. The G-MPSP technique in a fixed final time and input inequality constrained formulation has also been used for optimal guidance of an aerospace vehicle propelled by supersonic air-breathing engine, where the resulting thrust can be manipulated by managing the fuel flow and nozzle area (which is not possible in solid motors). However, operation of supersonic air-breathing engines is quite complex as the thrust produced by the engine is a result of very complex nonlinear combustion dynamics inside the engine. Hence, to generate the desired thrust, accounting for a fairly detailed engine model, a dynamic inversion based nonlinear state feedback control design has been carried out. The objective of this controller is to ensure that the engine dynamically produces the thrust that tracks the commanded value of thrust generated from the guidance loop as closely as possible by regulating the fuel flow rate. Simultaneously, by manipulating throat area of the nozzle, it also manages the shock wave location in the intake for maximum pressure recovery with sufficient margin for robustness. To filter out the sensor and process noises and to estimate the states for making the control design operate based on output feedback, an extended Kalman filter (EKF) based state estimation design has also been carried out and the controller has been made to operate based on estimated states. Moreover, independent control designs have also been carried out for the actuators so that their response can be faster. In addition, this control design becomes more challenging to satisfy the imposed practical constraints like fuel-air ratio and peak combustion temperature limits. Simulation results clearly indicate that the proposed design is quite successful in assuring the desired performance of the air-breathing engine throughout the flight trajectory, i.e., both during the climb and cruise phases, while assuring adequate pressure margin for shock wave management.

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48

(11014821), Ian V. Walters. "Operability and Performance of Rotating Detonation Engines." Thesis, 2021.

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Rotating Detonation Engines (RDEs) provide a promising avenue for reducing greenhouse gas emissions from combustion-based propulsion and power systems by improving their thermodynamic efficiency through the application of pressure-gain combustion. However, the thermodynamic and systems-level advantages remain unrealized due to the challenge of harnessing the tightly coupled physics and nonlinear detonation dynamics inherent to RDEs, particularly for the less-detonable reactants characteristic of applications. Therefore, a RDE was developed to operate with natural gas and air as the primary reactants at elevated chamber pressures and air preheat temperatures, providing a platform to study RDEs with the less-detonable reactants and flow conditions representative of land-based power generation gas turbine engines. The RDE was tested with two injector configurations in a broad, parametric survey of flow conditions to determine the effect of operating parameters on the propagation of detonation waves in the combustor and delivered performance. Measurements of chamber wave dynamics were performed using high-frequency pressure transducers and high-speed imaging of broadband combustion chemiluminescence, while thrust measurements were used to characterize the work output potential.

The detonation dynamics were first studied to characterize RDE operability for the target application. Wave propagation speeds of up to 70% of the mixture Chapman-Jouguet detonation velocity and chamber pressure fluctuations greater than 4 times the mean chamber pressure were observed. Supplementing the air with additional oxygen, varying the equivalence ratio, and enriching the fuel with hydrogen revealed that combustor operability is sensitive to the chemical kinetics of the reactant mixture. While most test conditions exhibited counter-rotating detonation waves within the chamber, one injector design was able to support single wave propagation. A thermodynamic performance model was developed to aid analysis of RDE performance by making comparisons of net pressure gain for identical flow conditions. While the injector that supported a single wave operating mode better followed the trends predicted by the model, neither injector achieved the desire stagnation pressure gain relative to the reactant manifold pressure. Application of the model to a generic RDE revealed the necessity of normalizing any RDE performance parameter by the driving system potential and identified the area ratio between the exhaust and injection throats as the primary parameter affecting delivered pressure gain. A pair of test conditions with distinct wave dynamics were selected from the parametric survey to qualitatively and quantitatively analyze the exhaust flow using high-speed particle image velocimetry. A single detonation wave with an intermittent counter-rotating wave was characterized in the first test case, while a steady counter-rotating mode was studied in the second. The velocity measurements were phase averaged with respect to the instantaneous wave location to reveal contrasting flowfields for the two cases. The total pressure and temperature of flow exiting the combustor were computed using the phase-resolved velocity measurements along with the measured reactant flowrate and thrust to close the global balance of mass and momentum, providing an improved method of quantifying RDE performance. Finally, a reduced order model for studying RDE operability and mode selection was developed. The circumferential detonation wave dynamics are simulated and permitted to naturally evolve into the quasi-steady state operating modes observed in RDEs. Preliminary verification studies are presented and areas for further development are identified to enable the model to reach a broader level of applicability.

The experimental component of this work has advanced understanding of RDE operation with less-detonable reactants and developed improved methods for quantifying RDE performance. The accompanying modeling has elucidated the design parameters and flow conditions that influence RDE performance and provided a framework to investigate the factors that govern RDE mode selection and operability.

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49

(6927776), Alexis Joy Harroun. "Investigation of Nozzle Performance for Rotating Detonation Rocket Engines." Thesis, 2019.

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Progress in conventional rocket engine technologies, based on constant pressure combustion, has plateaued in the past few decades. Rotating detonation engines (RDEs) are of particular interest to the rocket propulsion community as pressure gain combustion may provide improvements to specific impulse relevant to booster applications. Despite recent significant investment in RDE technologies, little research has been conducted to date into the effect of nozzle design on rocket application RDEs. Proper nozzle design is critical to capturing the thrust potential of the transient pressure ratios produced by the thrust chamber. A computational fluid dynamics study was conducted based on hotfire conditions tested in the Purdue V1.3 RDE campaign. Three geometries were investigated: nozzleless/blunt body, internal-external expansion (IE-) aerospike, and flared aerospike. The computational study found the RDE's dynamic exhaust plume enhances the ejection physics beyond that of a typical high pressure device. For the nozzleless geometry, the base pressure was drawn down below constant pressure estimates, increasing the base drag on the engine. For the aerospike geometries, the occurrance of flow separation on the plug was delayed, which has ramifications on nozzle design for operation at a range of pressure altitudes. The flared aerospike design, which has the ability to achieve much higher area ratios, was shown to have potential performance benefits over the limited IE-aerospike geometry. A new test campaign with the Purdue RDE V1.4 was designed with instrumentation to capture static pressures on the nozzleless and aerospike surfaces. These results were used to validate the results from the computational study. The computational and experimental studies were used to identify new flow physics associated with a rocket RDE important to future nozzle design work. Future computational work is necessary to explore the effect of different parameters on the nozzle performance. More testing, including with an altitude simulation chamber, would help quantify the possible benefit of new aerospike nozzle designs, including the flared aerospike geometry.

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50

VanderVeer, Joseph R. "A study of in-cylinder combustion processes by using high speed multi-spectral infrared imaging and a robust statistical analysis method." 2008. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17232.

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