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1
Joo, Won-Gu. "Intake/engine flowfield coupling in turbofan engines." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319865.
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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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Santos, Gustavo Di Fiore dos. "A methodology for noise prediction of turbofan engines." Instituto Tecnológico de Aeronáutica, 2006. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=291.
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A computional model is developed for prediction of noise emission from na existing or new turbofan engine. This model allows the simulation of noise generation from high bypass ratio turbofan engines, appropriate for use with computational programs for gas turbine performance developed at ITA. Analytical and empirical methods are used for spectrum shape, spectrum level, overall noise and free-field directivity noise. The most significant noise sources in turbofan engines are modeled: fan, compressor, combustion chamber, turbine, jet (separate streams or mixed jet), with corrections for forward speed, atmospheric attenuation, ground reflection, and nacelle acoustic treatment (perforate liners). The procedures for component noise prediction are combined to yield total turbofan engine noise emission, as a funtion of engine operation condition and of observer (distance and directivity angle).
4
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.
6
Kapekov, Ali. "Development of an innovative cooling concept for turbofan engines." Thesis, KTH, Energiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-246103.
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This paper is submitted in support of a candidature for the Double Degree in Vehicle Engineering with a specialization in Aerospace between KTH Royal Institute of Technology, Sweden, and Ecole Centrale Lyon, France. The present report emphasizes a research project for current or next generation turbofan engines used in civil aviation, and especially its equipment integration from a thermal management point of view. The cooling and ventilation of such equipment in the core compartment is especially harsh. Its optimization had been considered through a complete analysis described in an exhaustive paper which is only available internally at Airbus or for thesis examiners because of confidentiality issues. Considering only Two-Phase flow heat transfer, the heat pipes are deeply explained in order to familiarize the reader. An achievable heat pipe is modelled help to a 1D simulation software called LMS Imagine.Lab AMESim (Siemens PLM). The modelling is illustrated and correlated with experimental values for commercial heat pipes. Finally two other two-phase flow heat transfer systems are duly noted, with a short description of the theory that led to model adaptation and GUIs development using Matlab.Det här examensarbetet har genomförts för att uppfylla krav för dubbelexamen inom fordonsteknik med specialisering flyg och rymdteknik på KTH i Sverige och Ecole Centrale Lyon i Frankrike. Rapporten fokuserar på ett forskningsprojekt som behandlar teknologi för hantering av värmeöverföring i nuvarande eller framtida flygmotorer som används inom civil luftfart. Kylningen och ventilationen av flygmotorer och dess integration betraktas som särskilt krävande och komplext. Inom projektet har en optimering med tillhörande analyser har genomförts och resultat av dessa beskrivs i en uttömmande rapport tillgänglig för internt bruk på Airbus. Endast en kortfattad sammanställning presenteras i denna rapport som är tillgänglig för allmänhet. För att läsaren ska bekantas djupare med två-fas värmeöverföring, värmerörsteknologi (”heat pipes”) förklaras utförligt i rapporten. Ett passande värmerör design har tagits fram och modellerats med hjälp av 1D simuleringsverktyg LMS Imagine Lab AMESim från Siemens PLM. Den modellerade värmerör har illustrerats och korrelerats med experimentella värden för kända kommersiella värmerör. Slutligen, ytterligare två två-fas värmeöverföringssystem analyseras och noteras med en kort beskrivning av teorin som ledde till modellanpassning och GUI-utveckling i Matlab programmet.
7
Kwan, Pok Wang. "Flow management in heat exchanger installations for intercooled turbofan engines." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711622.
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Almeida, Odenir de. "Aeroacoustics of dual-stream jets with application to turbofan engines." Instituto Tecnológico de Aeronáutica, 2009. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=805.
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A Computational Aeroacoustics (CAA) and a novel semi-empirical model is developed for predicting the noise generated by the jet flow through dual stream (coaxial) nozzles, as found in modern turbofan engines. The acoustic source model was developed in a 2D and 3D framework, based on the Lilley's Equations, following the traditional MGBK method from NASA Langley Research Center. The semi-empirical model was based on the Four-Source model from the Institute of Sound and Vibration (ISVR). This suite of methodologies provided a mean of investigating the mechanisms of noise generation and propagation of subsonic coaxial jet flows, as well as the noise prediction at different operating conditions. The work done contributed to the development and improvement of a numerical tool for jet noise prediction of dual-stream exhaust systems, commonly employed in turbofan engines. Such research also subsidies the improvement of semi-empirical methods used in the Center of Reference in Gas Turbine (ITA) for the noise prediction of turbofans in all operating conditions.
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Adetifa, Oluwaseun Emmanuel. "Prediction of supersonic fan noise generated by turbofan aircraft engines." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/388030/.
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Prediction of Supersonic Fan Noise Generated by Turbofan Aircraft Engines was focussed on improving the capability of predicting supersonic fan noise from modern high-bypass-ratio turbofan aero-engines. The shift from single core jet engines to highbypass-ratio turbofan engines brought about a reduction in the overall aircraft engine noise principally by reducing the jet-broadband noise. However, this new design meant the size of the fan of a high-bypass-ratio turbofan engine, over subsequent years, has increased in diameter. This increase allowed for the speed of the tips of the fan blades to reach and exceed the speed of sound. At high power engine operation conditions, especially at take-off conditions, the noise levels observed from such engines is very high. A major component of this noise is the supersonic fan noise which is also referred to as buzz-saw noise. Shocks are produced at the fan blade tips at this high power engine operation condition. These shocks propagate upstream, against the inflow, following a helical path dictated by the rotation of the fan. The pressure field produced at the tip of the fan is represented as a series of shock waves and expansion waves. As this pressure field advances, it interacts with the incoming flow and acoustic treatment in the intake duct. The shocks in the pressure field are all unique and are of different amplitudes. This is because the fan blades, although manufactured to tight tolerances, are not perfectly alike. Also, the arrangement of these fan blades on the fan hub will also lead to unavoidable differences among the fan blades. These minute differences are reflected in the amplitudes of the shocks, making each shock slightly different from the others. Shocks in the pressure field propagate with respect to the magnitude of their pressure amplitude. Therefore, the shocks travel at different speeds. In the course of propagation, faster shocks catch up with slower ones, and they merge into a single shock, even as the shocks’ amplitudes are attenuated. The difference in speeds and the interactions among the shocks ensure a transfer of energy among the harmonics of the pressure field. This process is nonlinear; the work in this thesis is focussed on modelling the nonlinear propagation of the shocks pressure pattern. These interactions greatly enhance the lower frequency harmonics of the pressure field shifting the dominance from the blade passage frequency and its harmonics. Further upstream, the dominance of the low frequency harmonics is unmistakable. Subsequently the pressure field is radiated from the aircraft intake duct. The resultant radiated pressure field is that which is perceived by an observer in the far-field. The models presented in this thesis capture the main features of this nonlinear propagation and radiation of the pressure field generated at the fan blade tips, and generates predictions for supersonic fan noise levels in the intake duct and in the far-field. A time domain model named SPRID (Sawtooth Propagation in Rigid Intake Ducts) developed is presented. This model predicts the supersonic fan noise levels in ducts without any acoustic treatment, and has been validated against a benchmark frequency domain nonlinear propagation model (FDNS), and also measured data from a modelscale fan rig test provided by Rolls-Royce PLC. The need to incorporate the effect of acoustic liners in the modelling led to the development of a new model which employs the combined time-frequency domain approach. In this model, the nonlinear propagation of the pressure field is simulated in the time domain, while the acoustic liner effects are implemented in the frequency domain. This model also has been validated with measured data. The combined time-frequency domain prediction method was improved to incorporate more complex features of supersonic fan noise propagation. Features such as the change in duct radius along the duct axis and the consequent change in mean flow speeds, and boundary layer effects on the liner absorption have been included in a more advanced model. The advanced nonlinear model is a more representative model of real aircraft intake duct. Also, a theoretical radiation model (GX-Munt) was utilized to predict supersonic fan noise in the far-field. In this thesis, a whole study of supersonic fan noise, starting from source generation at the fan plane up to the radiation to the farfield is presented. The thesis includes an extensive literature review, research on the generation of a source sawtooth for propagation utilizing measured data, and development of equations for nonlinear propagation in axisymmetric intake ducts. Results of the parametric studies using the advanced nonlinear propagation model reliably show all the effects of nonlinear distortion of the shock waves, variation in intake geometry, flow speeds, and variations in the acoustic liner absorption as a consequence of changes in boundary-layer thickness. Comparisons made against measured data, from modelscale fan rig tests conducted by Rolls-Royce PLC, show good and reasonable agreement. The advanced nonlinear propagation model achieves improved prediction capability for supersonic fan noise.
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Spillere, André Mateus Netto. "Towards optimal design of acoustic liners in turbofan aero-engines." reponame:Repositório Institucional da UFSC, 2017. https://repositorio.ufsc.br/xmlui/handle/123456789/182589.
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2017.Made available in DSpace on 2018-01-09T03:20:40Z (GMT). No. of bitstreams: 1 348526.pdf: 3551847 bytes, checksum: e230fe18007e16805c64bbe54b532888 (MD5) Previous issue date: 2017
Motores turbofan são largamente utilizados em aeronaves comerciais e são uma das principais fontes de ruído. O ruído desse motores pode ser dividido em diferentes componentes, sendo que o ruído proveniente do fan é de grande importância no processo de certificação da aeronave. Este é geralmente dominado pela presença de tons e suas harmônicas, tornando desejável utilizar um tratamento acústico com grande atenuação em uma faixa estreita de frequência. Isto é obtido por meio de liners acústicos, que podem ser interpretados como um arranjo de ressonadores de Helmholtz. Tradicionalmente, os liners são caracterizados por meio de sua impedância acústica. Esta abordagem possui várias vantagens: (i) a impedância acústica pode ser estimada por modelos semi-empíricos de baixo custo; (ii) várias técnicas experimentais são reportadas na literatura para extrair a impedância do liner, como os métodos inversos, diretos e técnicas in situ; (iii) o conceito de impedância ótima para dutos pode ser desenvolvida, e portanto o liner pode ser projetado para alcançar a impedância ótima; (iv) a previsão de atenuação sonora em dutos é baseada na impedância acústica do liner. Estes quatro itens são abordados neste trabalho. Primeiramente, modelos semi-empíricos preditivos de liner são analisados e comparados com resultados experimentais. Os modelos são baseados na soma de diversos efeitos e dão uma ideia de quais afetam a impedância acústica do liner. Na sequência, técnicas experimentais são investigadas. O método clássico de acoplamento modal é modificado para incluir um modelo de impedância, resultando em curvas contínuas. Além disso, efeitos de condição de contorno na edução de impedância são considerados, e alternativas à condição de contorno de Ingard-Myers são implementadas. A diferença entre resultados na impedância quando a fonte sonora está a montante ou a jusante da amostra também é discutida. Em seguida, o conceito de impedância ótima para dutos circulares na ausência e presença de escoamento uniforme é apresentado, assim como aplicações para geometria de motores aeronáuticos turbofan. Finalmente, a previsão de atenuação sonora baseada em escoamento uniforme e cisalhante é comparada.
Abstract : Turbofan aero-engines are largely employed in commercial aircraft and are one of the main sources of noise. Engine noise can be divided into several components, and fan noise plays a major role in the aircraft certification process. It is generally dominated by the presence of a tone and its harmonics, making desirable to use an acoustic treatment with large attenuation at a narrow bandwidth. This is accomplished by means of acoustic liners, which can be seen as an array of Helmholtz resonators. Usually, the liner is characterized by its acoustic impedance. This approach has several advantages: (i) the acoustic impedance can be predicted by low-cost semi-empirical models; (ii) many experimental techniques are reported in the literature to extract the liner impedance, such as inverse methods, straightforward methods and in situ techniques; (iii) the concept of optimal impedance for ducts can be developed, and therefore the liner can be designed to achieve the optimal impedance; (iv) the sound attenuation prediction in ducts is based on the liner acoustic impedance. These four items are covered in this work. Firstly, liner prediction semi-empirical models are analysed and compared to experimental results. The models are based on the sum of several effects and give an insight into what alters the liner acoustic impedance. On the following, the experimental techniques are investigated. The classical mode matching method is modified to include an impedance model, resulting in smooth impedance curves. Also, the effect of boundary conditions in the educed impedance is considered, and alternatives to the Ingard-Myers boundary condition are implemented. The difference between upstream and downstream acoustic source positions in the educed impedance is also discussed. Next, the concept of optimal impedance for circular ducts in the absence and presence of mean flow is presented, as well some applications to turbofan aero-engine geometries. Finally, sound attenuation predictions based on uniform and shear flow are compared.
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Pan, Hongyu. "Impact characteristics of simulated hailstones during ingestion by turbofan aero-engines." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/27188.
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Recent in-flight instances of aircraft engine power loss involving hail ingestion have forced the manufacturers to demonstrate successful engine operation whilst ingesting hail. The main objective of this research project has been to obtain an understanding of the basic characteristics of hailstone impacts. A hail gun was designed to fire simulated hailstones at speeds up to 175 m/s. Three measurement techniques were used to determine the impact characteristics of the hailstones, i.e: patternator, high speed cine-photography, and still photography with short duration flashes. Using these techniques, the basic impact characteristics in terms of post-impact particle size, velocity and mass distribution were obtained for a variety of target configurations. The influence of seemingly important parameters on the impact characteristics were investigated, including approach angle and velocity, target curvature, and target rotation. Studies were further made into multiple impacts, and the effect of target curvature and rotation on the impact characteristics. Based on the experimental results, a set of empirical rules and a mathematical model describing hailstone break-up were defined.
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Lolis, Periklis. "Development of a Preliminary Weight Estimation Method for Advanced Turbofan Engines." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9244.
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The present work focuses on preliminary weight estimation methods that enable
the feasibility studies of novel aero engines. The key contributions can be found
in the analysis of the existing preliminary weight estimation methods, the de-
velopment of a new preliminary weight estimation method and the study on the
feasibility of a Geared Turbofan (GTF) engine.
In more detail, the existing preliminary weight estimation methods are exam-
ined in the rst part of the thesis, aiming to de ne their suitability for current
turbofan engines, but also for future engine arrangements. For this purpose, they
are examined not only quantitatively, to verify their accuracy, but also qualita-
tively to gure out if they are able to re
ect the key thermodynamic and design
parameter variations on weight. Apart from NASA WATE no method achieves
either the required accuracy, or simulates the weight trends.
Realising the need for a more accurate, robust,
exible and extensible method,
a new "component based" method that performs basic component design to es-
timate engine weight, is devised. Its accuracy is veri ed by comparing the whole
engine weight prediction and estimated component design against the publicly
available data of two major turbofan engines and the weight predictions of exist-
ing weight estimation methods.
ATLAS, the tool based on the above method was used to estimate weight over
a range of Bypass Ratio (BPR) and Turbine Entry Temperature (TET) values for
a Direct Drive Turbofan (DDTF) and a GTF two spool arrangement, reaching
the following conclusions:
The adjustments of Low Pressure Turbine (LPT) number of stages or geom-
etry are not su cient, if high stage isentropic e ciency values are targeted
at high BPR values
For the examined engine model, with the given weight estimation method-
ology, the weight reduction, when a gearbox is introduced at a DDTF,
depends on the reduction of LPT stages, with the other components having
negligible impact. However, it should be noted that a constant fan diameter
was assumed for both con gurations. A fan loss model and more detailed
weight estimation of frames, shafts and control and accessories is required
to verify this conclusion.
The comparison of a DDTF and a GTF engine is representative only if the
cycles corresponding to the installed performance optima are considered.Engines with the same thermodynamic cycle could only be compared when
the optima cannot be reached, due to geometry restrictions.
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Whellens, Matthew W. "Multidisciplinary optimisation of aero-engines using genetic algorithms and preliminary design tools." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/10510.
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This study investigates a novel methodology for the preliminary design of aeroengines.
This involves the modelling of the disciplines that affect the engine's requirements
and constraints, their implementation in software format and their coupling into a single
unit. Subsequently, this unit is interfaced with an optimiser software. The resulting
multidisciplinary optimisation (MDO) tool allows the automation of the traditional,
human-based preliminary design process.
The investigation of the above-mentioned novel methodology is carried out
through the development of a "pilot" MDO tool and its subsequent utilisation in three case
studies, characterised by different optimisation scenarios. The selection of each case study
is motivated by current research questions, such as aviation's contribution to climate
change or the attractiveness of specific novel propulsion concepts.
The outcome of the pilot MDO study is considered successful and has been well
received by several academic and industrial aero-engine organisations. The choice of the
disciplines and of their modelling fidelity allowed a realistic representation of the main
disciplinary interactions and tradeoffs that characterise the important phase of preliminary
design. The computational effort involved in the solution of the optimisation studies was
found to be acceptable, and no major reprogramming was required when different
optimisation scenarios were considered. The case studies were investigated with an ease
and comprehensiveness that would not have been achievable through a human-based
parametric analysis.
The positive experience with the pilot MDO tool suggests that an automated
methodology for the preliminary design of aero-engines is feasible, applicable and valuable.
Its adoption can provide substantial advantages over the traditional human-based
approach, such as a reduction in human effort, costs and risk. From this perspective, the
pilot study constitutes a first step towards the development of a full-scale MDO tooL
usable by aero-engine manufacturers. In the near future, issues like climate change could
drive significant modifications in airframe and engine design. A preliminary design MDO
tool is therefore timely, and has the potential of making a significant contribution.
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Ford, Sean T. "Aerothermodynamic cycle design and optimization method for aircraft engines." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53006.
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This thesis addresses the need for an optimization method which can simultaneously optimize and balance an aerothermodynamic cycle. The method developed is be able to control cycle design variables at all operating conditions to meet the performance requirements while controlling any additional variables which may be used to optimize the cycle and maintaining all operating limits and engine constraints. The additional variables represent degrees of freedom above what is needed for conservation of mass and energy in the engine system. The motivation for such a method is derived from variable cycle engines, however it is general enough to use with most engine architectures. The method is similar to many optimization algorithms but differs in its implementation to an aircraft engine by combining the cycle balance and optimization using a Newton-Raphson cycle solver to efficiently find cycle designs for a wide range of engine architectures with extra degrees of freedom not needed to balance the cycle. Combination of the optimization with the cycle solver greatly speeds up the design and optimization process. A detailed process description for implementation of the method is provided as well as a proof of concept using several analytical test functions. Finally, the method is demonstrated on a separate flow turbofan model. Limitations and applications of the method are further explored including application to a multi-design point methodology.
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Zamboni, Giulio. "Fan root aerodynamics." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611841.
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Andersen, Ted Thanning. "A study of thermographic phosphor thermometry in an operating turbofan engine." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-02132009-171409/.
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Piercy, Neil Philip. "A redundancy approach to sensor failure detection : with application to turbofan engines." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305488.
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Maldonado, Ana Luisa Pereira. "On the prediction of the effect of interstage liners in turbofan engines." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/413581/.
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The current trends for next generation turbofan engines are towards shorter nacelles and increased distances between the fan and the outlet guide vanes. This leads to an overall reduction in lined surface areas as well as an increase in the relative importance of the interstage liner, which is the liner placed between the rotor blades and the stator vanes. The interstage is different in that the liner is subject to a mean flow with a strong swirl component and shear. This project will contribute to understanding and predicting the effect of the swirl on liner attenuation and consists of 4 steps: To model an eigenvalue problem that includes sheared and swirling mean flows and acoustic absorption, to develop a code based on this eigenvalue problem and to validate it, to compare results from this code with experimental results and to carry out a parametric study to evaluate how the swirling flow afects liner attenuation and optimum impedance. Two models were developed. The first one considers a ducted sheared mean flow and is based on the Pridmore-Brown equation and the second one takes into consideration a mean flow with swirl and shear and is based on the Linearized Euler Equations. For both cases an eigenvalue problem was obtained by applying the normal mode analysis to the governing equations together with the impedance boundary condition. Both models were discretized using a Finite Difference Method. The codes were exhaustively validated against predicted values obtained by other methods for uniform, sheared and swirling mean flows and hard-walled and lined ducts. The swirling mean flow, when present, is a combination of rigid body and vortex swirl. A cross-validation between the Finite difference code based on the Linearized Euler Equation and the JM66 code from Rolls-Royce was carried out for a more realistic case. Axial wavenumbers and pressure and velocity eigenvectors obtained with the JM66 code were compared with the current predictions. A comparison has been conducted of predictions from the current Finite Difference code with measured data at a single frequency for a range of spinning mode numbers. Qualitative agreement is obtained for the measured Power Transmission loss (TL) but the low Mach numbers and modest TL levels meant that the effect of swirl was small nad it was difficult to validate the accuracy at the Finite Difference code specifically for the swirl case. Finally, a parametric study was undertaken for hard-walled and lined ducts for realistic interstage conditions to evaluate the effect sound propagation in swirling flows. This confirmed that the effect of swirl is higher for radial modes near cut-off and tends to vanish for higher radial mode orders. The swirl strongly changes the modal content. When swirl is included, the modal distribution for positive and negative azimuthal mode orders is no longer symmetrical. The higher the swirling flow magnitude, the more the modal content is shifted to negative circumferential mode orders. Co-rotating modes become more cut-on and contra-rotating modes become more cut-off. When acoustic absorptive liners are considered, the swirl changes the liner optimum resistance and reactance and affects the optimum insertion loss. The optimum resistance becomes considerably higher and the change in optimal liner reactance is not as pronounced. The swirling flow also reduces attenuation; the insertion loss is lower when swirl is considered. As a conclusion, swirling flow should be considered when designing liners.
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Risi, John D. "Analytical investigation of active control of radiated inlet noise from turbofan engines." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-08222009-040623/.
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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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Boumedmed, Abdelkader. "The use of variable engine geometry to improve the transient performance of a two-spool turbofan engine." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263451.
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Giannakakis, Panagiotis. "Design space exploration and performance modelling of advanced turbofan and open-rotor engines." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/7957.
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This work focuses on the current civil engine design practice of increasing overall pressure
ratio, turbine entry temperature and bypass ratio, and on the technologies required in
order to sustain it. In this context, this thesis contributes towards clarifying the following
gray aspects of future civil engine development:
the connection between an aircraft application, the engine thermodynamic cycle and
the advanced technologies of variable area fan nozzle and fan drive gearbox.
the connection between the engine thermodynamic cycle and the fuel consumption
penalties of extracting bleed or power in order to satisfy the aircraft needs.
the scaling of propeller maps in order to enable extensive open-rotor studies similar
to the ones carried out for turbofan engines.
The rst two objectives are tackled by implementing a preliminary design framework,
which comprises models that calculate the engine uninstalled performance, dimensions,
weight, drag and installed performance. The framework produces designs that are in
good agreement with current and near future civil engines. The need for a variable area
fan nozzle is related to the fan surge margin at take-o , while the transition to a geared
architecture is identi ed by tracking the variation of the low pressure turbine number of
stages. The results show that the above enabling technologies will be prioritised for long
range engines, due to their higher overall pressure ratio, higher bypass ratio and lower
speci c thrust. The analysis also shows that future lower speci c thrust engines will su er
from higher secondary power extraction penalties.
A propeller modelling and optimisation method is created in order to accomplish the
open-rotor aspect of this work. The propeller model follows the lifting-line approach and
is found to perform well against experimental data available for the SR3 prop-fan. The
model is used in order to predict the performance of propellers with the same distribution
of airfoils and sweep, but with di erent design point power coe cient and advance ratio.
The results demonstrate that all the investigated propellers can be modelled by a common
map, which separately determines the ideal and viscous losses.
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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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Hutcheson, Florence Vanel. "Advanced modeling of active control of fan noise for ultra high bypass turbofan engines." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/29466.
Full textAbstract:
An advanced model of active control of fan noise for ultra high bypass turbofan
engines has been developed. This model is based on a boundary integral equation method
and simulates the propagation, radiation and control of the noise generated by an engine
fan surrounded by a duct of finite length and cylindrical shape, placed in a uniform flow.
Control sources, modeled by point monopoles placed along the wall of the engine inlet or
outlet duct, inject anti-noise into the duct to destructively interfere with the sound field
generated by the fan. The duct inner wall can be lined or rigid. Unlike current methods,
reflection from the duct openings is taken into account, as well as the presence of the
evanescent modes. Forward, as well as backward (i.e., from the rear of the engine),
external radiation is computed.
The development of analytical expressions for the sound field resulting from both the
fan loading noise and the control sources is presented. Two fan models are described. The
first model uses spinning line sources with radially distributed strength to model the
loading force that the fan blades exert on the medium. The second model uses radial
arrays of spinning point dipoles to simulate the generation of fan modes of specific modal
amplitudes. It is shown that these fan models can provide a reasonable approximation of
actual engine fan noise in the instance when the modal amplitude of the propagating
modes or the loading force distribution on the fan blades, is known.
Sample cases of active noise control are performed to demonstrate the feasibility of
the model. The results from these tests indicate that this model 1) is conducive to more
realistic studies of active control of fan noise on ultra high bypass turbofan engines
because it accounts for the presence of evanescent modes and for interference between
inlet and outlet radiation, which were shown to have some impact on the performance of
the active control system; 2) is very useful because it allows monitoring of any region of
the acoustic field; 3) is computationally fast, and therefore suitable to conduct parametric
studies.
Finally, the potential that active noise control techniques have for reducing fan noise
on an ultra high bypass turbofan engine is investigated. Feedforward control algorithms
are simulated. Pure active control techniques, as well as hybrid (active/passive) control
techniques, are studied. It is demonstrated that active noise control has the potential to
reduce substantially, and over a relatively large far field sector, the fan noise radiated by
an ultra high bypass turbofan engine. It is also shown that a hybrid control system can
achieve significantly better levels of noise reduction than a pure passive or pure active
control system, and that its optimum solution is more robust than the one achieved with a
pure active control system.
The model has shown to realistically predict engine acoustic behavior and is thus
likely to be a very useful tool for designing active noise control systems for ultra high
bypass turbofan engines.Ph. D.
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James, Denman H. (Denman Halsted). "Influence of system architecture changes on organizational work flow and application to Geared turbofan engines." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/83791.
Full textAbstract:
Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-73).
The design and development of a gas turbine engine for aircraft applications is a highly integrated process, and requires the integration of efforts of large numbers of individuals from many design specialties. If the design process is well defined and the product architecture is stable, the outcome of the process will become highly predictable and repeatable. In the case that there are significant architecture changes due to technology insertion, customer requirements or overall changes in component configuration for performance, this large and integrated design process may become more challenging. Communication of design intent, requirements and predicted performance for all of the components, systems and subsystems must be made without error to all involved in the development of the product. Pratt & Whitney is a large gas turbine engine design company, and has been in the engine business since it's inception in 1925. In 2008, P&W designed, built and flew a large "Geared Turbofan" engine which was a demonstrator for a new product architecture being developed, the first of the new product family being the PWl 524G. This new engine architecture is different from the more traditional turbofan engine architecture in the use of a reduction gear set between the fan and the turbine shaft which drives it. Earlier work in examination of gas turbine engine product-design process interactions has been performed with a traditional high bypass ratio gas turbine engine architecture using the PW4098. Using two test cases, the PW4098 and PW1524G, this work seeks to map the architecture of a gas turbine aero engine in the Design Structure Matrix format, with all major connectivity shown, and then to apply organizational information in the form of Domain Matrix Maps to the physical architectural connectivity to determine which portions of the architecture result in additional or functional group interactions. The determination of the architecture driven changes in the number of functional group interactions is made first, and then isolation of "novel" functional group interactions is made with the original architecture serving as the baseline for organizational interaction. Analysis of these results is then performed to examine the potential organizational impact of moving from traditional turbofan architecture to a geared turbofan architecture. The potential impact to the organization in assessed and recommendations are made to minimize the potential impact of the change. The analysis presented shows that the change in engine architecture represents a move to a more distributed and less modular architecture. The DSM shows a 20% increase in density of connectivity between components. From an organizational impact perspective, there is a 30% change overall in the total number of functional group interactions in the integration of the engine. The impact of these changes on particular design functional groups is discussed, and the data suggests that the more distributed architecture of the PW1524G likely will require more system integration effort than the traditional turbofan architecture of the PW4098.
by Denman H. James.
S.M.in Engineering and Management
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Hallez, Raphael F. "Investigation of the Herschel-Quincke Tube Concept as a Noise Control Device for Turbofan Engines." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31081.
Full textAbstract:
An innovative implementation of the Herschel-Quincke tubes concept for the reduction of noise from turbofan engines is proposed here. The approach consists of installing circumferential arrays of Herschel-Quincke (HQ) tubes or waveguides in the inlet of the turbofan engine. An analytical technique was developed to predict the effects of HQ tubes applied to circular inlets. The modeling technique involves modeling the tubes-inlet interfaces as finite piston sources that couple the acoustic field inside the inlet with the acoustic field within the HQ tubes. An optimization technique based on genetic algorithms was also developed to be able to design and optimize the system parameters. The accuracy of the model was validated with experimental data obtained from two types of turbofan engines. Analytical predictions are shown to correlate well with experimental data. The analytical model is then used to provide insight into the noise control mechanisms involved in the system. It is shown that the energy in an incident mode is in part reflected back to the fan and that some energy is also scattered into other higher-order modes. Thus, the suppression of a particular mode is due to the combination of the scattered contributions from the various incident modes. The effects of the system parameters were analyzed and parametric studies were conducted. Different configurations for the arrays of HQ tubes such as helical patterns or tubes at an angle with respect to the inlet axis were also investigated. The results show the great potential of the HQ tubes system to reduce noise from turbofan engines.Master of Science
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Barnobi, Christopher Louis. "Improvement In Acoustic Liner Attenuation In Turbofan Engines By Means Of Plasma Synthetic Jet Actuator." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/34022.
Full textAbstract:
Despite many advances in aviation noise control over the past 50 years, the industry is continually striving to reduce noise emissions. Turbofan engine acoustic liners are efficient attenuators of engine noise. Plasma actuators have been used as flow control devices in other settings and will now be studied as an enhancement for acoustic liners. A plasma actuator can excite oscillatory flow or a single direction (bias flow). Both flow types are studied as possible means to excite turbofan liners in order to improve the acoustic performance.
Experiments revealed the oscillatory flow as the dominant factor in controlling resonator performance. The phase control of the actuator signal is an important parameter when dealing with the oscillatory flow. The actuator is first applied to a single resonator and then a set of six resonators. The experiments show that with the correct phase, the actuators improved the performance of a single resonator by 3 dB to 5 dB. The results for the array of actuators/resonators mirror the results of a single device.
Beyond the improvements in performance, a number of other factors affect the usefulness of the plasma actuator technology in a turbofan environment. The ability of the actuator to produce plasma is susceptible to small imperfections in the device, and this property will likely be amplified in a perforated sheet with embedded actuators. Additional weight and energy consumed by the actuators is another factor to consider. Finally, plasma actuator operation produces ozone, so environmental effects deserve consideration as well.Master of Science
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Sloan, B. "The effect of nozzle exit geometry on the aerodynamic performance of bypass flow of turbofan engines." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517527.
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Jenkins, G. "Models for the prediction of rear-arc and forward-arc fan broadband noise in turbofan engines." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/361712/.
Full textAbstract:
This thesis investigates three elements necessary for the prediction of the broadband noise from a turbofan engine due to the interaction between the turbulent rotor wakes with the Outlet Guide Vanes (OGVs). These are (i) the sound radiation from a cascade of closely spaced blades interacting with rotor wake turbulence, (ii) an analysis of the behaviour of hotwire velocity data from a Large Scale Fan Rig (LSFR), (iii) the development of a scheme for the prediction of the blockage due to the transmission of multi mode sound across the rotor necessary for the prediction of noise in the forward-arc. (i) Cascade noise model A noise model is presented for the prediction of rotor wake turbulence with a cascade of OGVs. Similar to other approaches of this kind, computation time becomes excessive at high frequencies as the number of modes required increases. This thesis shows that at sufficiently high frequencies, when at least two modes are cut-on between adjacent blades, the acoustic blade coupling is weak and the cascade sound radiation closely approximates to that of an isolated aerofoil whose radiation can be computed efficiently using single airfoil theory, thereby greatly reducing computation time. (ii) Characteristics of rotor wake turbulence One factor currently limiting accurate fan broadband noise predictions is an understanding of rotor wake turbulence at the OGV leading edge. This thesis analyses in detail recent hotwire velocity data measured in the interstage of an LSFR. The focus here is on assessing the extent of self-preservation in the rotor wake, whereby the mean and turbulent wake characteristics can be deduced at any position downstream of the rotor and at any operating condition from a limited number of measurements. Unlike as previously assumed, this analysis demonstrates insufficient self-preserving behaviour to justify further pursuit of this approach. Rotor wake turbulence must therefore be measured or predicted at each operating condition separately. An analysis procedure is developed by which the characteristics of individual wakes, necessary for broadband noise predictions, may be inferred from rotor wake velocity measurements in situations in which there is significant overlap between adjacent wakes. (iii) Multi mode rotor blockage Noise generated by the OGV propagates to the forward arc by passing upstream through the spinning rotor. This thesis presents a model for the sound power transmission loss associated with crossing the rotor that includes modal frequency scattering effects. It is shown that the results obtained using exact cascade scattering closely agree at low and high frequencies with the results from a relatively simple prediction scheme that assumes that only plane waves propagate through the cascade, thereby ignoring modal scattering effects. The advantage of making this approximation is that the computation is considerably more efficient than a full cascade calculation. At low frequencies, where only plane waves propagate in the gap, exact agreement is obtained between the exact and plane wave models. Close agreement is also observed in the high frequency limit where a large number of cascade modes are cut-on, most of which are well cut-on and hence whose behaviour tends that of the plane wave mode. The three components of the prediction procedure outlined above are combined to perform a prediction of the rear-arc and forward-arc broadband noise from an LSFR. Comparison of the measured and predicted noise spectra are in reasonable agreement with variations with working line and fan speed being reasonably well captured.
30
de, la Riva Diego Horacio. "Modeling of Herschel/Quincke-Liner Systems for the Control of Aft Fan Radiation in Turbofan Engines." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28080.
Full textAbstract:
Commercial aviation transportation has experienced an overwhelming growth over the years. However, this expansion has encountered an important barrier: noise. Several studies have shown that residents in these areas experience problems such as stress and sleep disturbance. These problems have translated into demands for a better quality of life from airport residents which in turn have translated into more stringent aircraft noise regulations. As a result, large amounts of resources have been diverted towards the improvement of existing noise attenuation technologies and the development of more effective ones. In terms of turbofan generated noise, the most widely used technology is that of absorbent materials or liners. In recent investigations Alonso et al. have combined Herschel/Quincke (HQ) tubes with liners. This combination has the potential of effectively controlling pure tones and broadband noise in inlet sections of modern turbofan engines. Since a comprehensive approach for engine noise reduction will involve both inlet and aft HQ-Liner systems, additional research efforts were needed to evaluate their performance at reducing aft fan radiation
In the present work, a combination of traditional liners and Herschel/Quincke waveguide resonators for aft fan radiation control is proposed. A theoretical model is developed in order to predict noise reduction due to such systems. The newly developed tool was then utilized to design an HQ-liner that was installed and tested in the aft section of the NASA Active Noise Control Fan (ANCF) rig. This experimental data was utilized to prove the potential of these systems and to validate the mathematical model. Analytical predictions correlate well with experiments.
The NASA ANCF rig is not representative of a real turbofan engine. In order to assess the behavior of HQ-Liners in a more realistic environment a new system was specifically designed for a generic turbofan engine and its performance analyzed.
The sound field inside HQ tubes has been described assuming plane waves only. This assumption limits the model to frequencies below the tube first resonance. In order to overcome this limitation a new model accounting for higher order modes inside the tubes has been developed.Ph. D.
31
Callender, Willaim B. "An investigation of innovative technologies for reduction of jet noise in medium and high bypass turbofan engines." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1085666850.
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CALLENDER, WILLIAM BRYAN. "AN INVESTIGATION OF INNOVATIVE TECHNOLOGIES FOR REDUCTION OF JET NOISE IN MEDIUM AND HIGH BYPASS RATIO TURBOFAN ENGINES." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1085666850.
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Bowersox, Rodney Dale Welch. "Meanflow and turbulence measurements in the wake of a supersonic through-flow cascade." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040531/.
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Envia, Edmane. "Influence of vane sweep on rotor-stator interaction noise." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184609.
Full textAbstract:
In this dissertation the influence of vane sweep on rotor-stator interaction noise is investigated. In an analytical approach, the interaction of a convected gust, representing the rotor viscous wake, with a cascade of finite span swept airfoils, representing the stator, is analyzed. The analysis is based on the solution of the exact linearized equations of motion. High-frequency convected gusts for which noise generation is concentrated near the leading edge of the airfoils are considered. In a preliminary study, the problem of an isolated finite span swept airfoil interacting with a convected gust is analyzed. Using Fourier transform methods and the Wiener-Hopf technique, an approximate solution for this problem is developed. Closed form expressions for the acoustic farfield are obtained and used in a parametric study to assess the effect of airfoil sweep on noise generation. Results indicate that sweep can substantially reduce the farfield noise levels for a single airfoil. Utilizing the single airfoil model, an approximate solution to the problem of noise radiation from a cascade of finite span swept airfoils interacting with a convected gust is derived. Only upstream radiated noise is considered. Neglecting the weak coupling between the adjacent leading edges at high frequencies, the cascade solution is constructed as a superposition of acoustic farfields emanating from an infinite number of isolated airfoils. A parametric study of noise generated by gust-cascade interaction is then carried out to assess the effectiveness of vane sweep in reducing rotor-stator interaction noise. The results of the parametric study show that, over a fairly wide range of conditions, sweep is beneficial in reducing noise levels. One conclusion of particular importance is that rotor wake twist or circumferential lean substantially influences the effectiveness of vane sweep. The orientation of the vane sweep must be chosen to enhance the natural phase lag caused by wake lean, in which case rather small sweep angles substantially reduce the noise levels.
35
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.
Full textAbstract:
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.
36
Detwiler, Kevin P. "Reduced fan noise radiation from a supersonic inlet." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09192009-040457/.
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Mertens, Tanguy. "A new mapped infinite partition of unity method for convected acoustical radiation in infinite domains." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210365.
Full textAbstract:
Résumé:Cette dissertation s’intéresse aux méthodes numériques dans le domaine de l’acoustique. Les propriétés acoustiques d’un produit sont devenues une part intégrante de la conception. En effet, de nos jours le bruit est perçu comme une nuisance par le consommateur et constitue un critère de vente. Il y a de plus des normes à respecter. Les méthodes numériques permettent de prédire la propagation sonore et constitue dès lors un outil de conception incontournable pour réduire le temps et les coûts de développement d’un produit.
Cette dissertation considère la propagation d’ondes acoustiques dans le domaine fréquentiel en tenant compte de la présence d’un écoulement. Nous pouvons citer comme application industrielle, le rayonnement d’une nacelle de réacteur d’avion. Le but de la thèse est de proposer une nouvelle méthode et démontrer ses performances par rapport aux méthodes actuellement utilisées (i.e. la méthode des éléments finis).
L’originalité du travail consiste à étendre la méthode de partition de l’unité polynomiale dans le cadre de la propagation acoustique convectée, pour des domaines extérieurs. La simulation acoustique dans des domaines de dimensions infinies est réalisée dans ce travail à l’aide d’un couplage entre éléments finis et éléments infinis.
La dissertation présente la formulation de la méthode pour des applications axisymétriques et tridimensionnelles et vérifie la méthode en comparant les résultats numériques obtenus avec des solutions analytiques pour des applications académiques (i.e. propagation dans un conduit, rayonnement d’un multipole, bruit émis par la vibration d’un piston rigide, etc.). Les performances de la méthode sont ensuite analysées. Des courbes de convergences illustrent à une fréquence donnée, la précision de la méthode en fonction du nombre d’inconnues. Tandis que des courbes de performances présentent le temps de calcul nécessaire pour obtenir une solution d’une précision donnée en fonction de la fréquence d’excitation. Ces études de performances montrent l’intérêt de la méthode présentée.
Le rayonnement d’un réacteur d’avion a été abordé dans le but de vérifier la méthode sur une application de type industriel. Les résultats illustrent la propagation pour une nacelle axisymétrique en tenant compte de l’écoulement et la présence de matériau absorbant dans la nacelle et compare les résultats obtenus avec la méthode proposée et ceux obtenus avec la méthode des éléments finis.
Les performances de la méthode de la partition de l’unité dans le cadre de la propagation convectée en domaines infinis sont présentées pour des applications académiques et de type industriel. Le travail effectué illustre l’intérêt d’utiliser des fonctions polynomiales d’ordre élevé ainsi que les avantages à enrichir l’approximation localement afin d’améliorer la solution sans devoir créer un maillage plus fin.
Summary:
Environmental considerations are important in the design of many engineering systems and components. In particular, the environmental impact of noise is important over a very broad range of engineering applications and is increasingly perceived and regulated as an issue of occupational safety or health, or more simply as a public nuisance. The acoustic quality is then considered as a criterion in the product design process. Numerical prediction techniques allow to simulate vibro-acoustic responses. The use of such techniques reduces the development time and cost.
This dissertation focuses on acoustic convected radiation in outer domains such as it is the case for turbofan radiation. In the current thesis the mapped infinite partition of unity method is implemented within a coupled finite and infinite element model. This method allows to enrich the approximation with polynomial functions.
We present axisymmetric and three-dimensional formulations, verify and analyse the performance of the method. The verification compares computed results with the proposed method and analytical solutions for academic applications (i.e. duct propagation, multipole radiation, noise radiated by a vibrating rigid piston, etc.) .Performance analyses are performed with convergence curves plotting, for a given frequency, the accuracy of the computed solution with respect to the number of degrees of freedom or with performance curves, plotting the CPU time required to solve the application within a given accuracy, with respect to the excitation frequency. These performance analyses illustrate the interest of the mapped infinite partition of unity method.
We compute the radiation of an axisymmetric turbofan (convected radiation and acoustic treatments). The aim is to verify the method on an industrial application. We illustrate the radiation and compare the mapped infinite partition of unity results with finite element computations.
The dissertation presents the mapped partition of unity method as a computationally efficient method and illustrates its performances for academic as well as industrial applications. We suggest to use the method with high order polynomials and take the advantage of the method which allows to locally enrich the approximation. This last point improves the accuracy of the solution and prevent from creating a finer mesh.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Andreadis, Eleftherios. "Upgrade Evaluation of a Military Turbofan Engine." Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4937.
Full textAbstract:
As the gas turbine technology advances, new features are incorporated to field engines. The new technologies can be implemented during upgrade programs, which improve the characteristics of the engines. It is observed that the current trend is the development of upgrade programs that increase the life of the engines and reduce the Life Cycle Cost, rather than programs that increase the performance of the engines. The main objective of the present thesis is to review the advantages and disadvantages of a real upgrade engine with increased life and of a hypothetical upgrade engine, whose increased life was converted into increased performance, using the same new technology.
This thesis investigates a real life upgrade program, the Engine Enhancement Package (EEP), which was developed for the F100-PW-229 military turbofan engine and increases the life of the engine from 4300 cycles to 6000 cycles. This study highlights how the same new technology can be utilized to increase the performance of the engine instead of its life. The performance increase is achieved with the throttle push method, having as main results to increase the thrust by 1.14% and to decrease the life of the upgraded engine from 6000 cycles to 4300 cycles. This result was derived using the Larson Miller Parameter, which is used for the calculation of the creep life. This project provides a detailed assessment of the performance and the lifing of the engine before and after the upgrade in both cases (increased life and increased performance).
The findings of this study provide to the military engine user useful information that can be used to determine one’s decision about accepting or not of an extended program like the upgrade presented in this thesis, given its particularly high cost. The main conclusion of this thesis is that the savings from the life increase are more valuable than the increased capabilities from the performance improvement. A similar study for a civil engine can draw significant results. In this case, the increased performance can be presented in terms of increased profit from the better fuel consumption, the increased range and the increased payload.
39
Rosette, Keith Andrew. "Investigation of a compact acoustic source array for the active control of aircraft engine fan noise." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12302008-063020/.
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Hague, Douglas C. (Douglas Charles) 1967. "Description of a turbofan engine product development process." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/29164.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, System Design & Management Program, 2001.Includes bibliographical references (p. 123-125).
This research explores what requirements are necessary for the development of a turbofan engine and how they evolve through the product development cycle. This work utilizes a parameter-based design structure matrix (DSM) to define the interfaces and interdependencies present in a large commercial aircraft propulsion system. The DSM was developed from the system level to the module level allowing one to examine the assumptions made throughout the entire life cycle of the product. The work utilizes the system-level DSM to show the similarities between the turbofan engine product development process (PDP) and the software spiral product development process. This work examines the parameter-based DSM in each of the design phases and attempts to understand the assumptions made in each phase and how the assumptions change as the product proceeds through the development cycle. By examination of the DSM, it was found that program goals and requirements lead to an initial set of design parameters. These design parameters are then iterated until a satisfactory product defamation is developed. Each stage concludes with the integration and testing of that stages work. In all stages risk management occurs and with the necessary revision of the program plan for subsequent stages (not in the system-level DSM). The work shows that the PDP for a turbofan engine can be viewed as a spiral process. The thesis then suggests that, in general, the current industry practices for the development of complex physical systems have similarity to the spiral framework for development of software.
by Douglas C. Hague.
S.M.
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Lindkvist, Oskar. "Model Adaptation of a Mixed Flow Turbofan Engine." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80667.
Full textAbstract:
Gas turbine performance models are usually created in an object oriented manner, where different standard components are connected to form the complete model. The characteristics of these components are often represented by component maps and empirical correlations. However, engine specific component characteristics are seldom available to anyone outside of the manufacturers. It is therefore very common for researchers to use publicly accessible or generic component maps instead. But in order to reduce prediction errors the maps have to be modified to fit any specific engine. This thesis work investigates the process of adapting a parametric turbofan engine model to a limited amount of test-data using the propulsion program EVA. Steady state test-data was generated using an initial reference model with SLS operating conditions. Another engine model with different fan, compressor and turbine maps was then used in the adaptation. An initial on-design model was adapted to the highest power test-data point. This model is based on aerothermodynamic equations and is used as a reference to scale the generic component maps to. A sensitivity analysis was done at this point in order to find dependencies between unknown component parameters and test data. These were then included in the cycle solver which employs a version of the Newton-Raphson method. After the fan and compressor maps had been scaled to the design point they were adapted to test-data by adjusting the mass flow parameters in a direct search optimizer. Finally, speed lines in the fan and compressor maps were relabeled to reduce rotor speed errors. The adapted performance model was then validated against the reference model at a few flying conditions. The performance model results demonstrate that it is possible to greatly reduce prediction errors by only adjusting the corrected mass flow in fan and compressor maps. Additionally, rotor speed errors could successfully be corrected as a final step in the adaptation by relabeling speed lines in the component maps. When validated, the adapted model had a maximum parameter error of 1.5%.
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Férand, Mélissa. "Far-field combustion noise modeling of turbofan engine." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0007.
Full textAbstract:
Depuis l'introduction du moteur à réaction pour la propulsion des avions dans les années 1950, l'acoustique est devenue d'un grand intérêt pour l'industrie du moteur. Alors que les turboréacteurs initiaux étaient dominés par le bruit de jet, l'introduction du moteur à turbofan dans les années 1960 a permis d'atténuer le bruit de jet, mais a introduit le bruit de soufflante. Dans les années 1970, grâce à de nouvelles conceptions avancées pour la réduction du bruit, une réduction majeure du bruit des avions s'en est suivie et la contribution du bruit de combustion a été remise en question. En effet, une réglementation plus restrictive du bruit pourrait exiger que le bruit de fan et de jet soient réduits au point où une réduction du bruit de combustion devienne également nécessaire. En outre, la conception des chambres de combustion est pilotée uniquement par la restriction des polluants chimiques produits par la combustion, l'efficacité et la consommation. L'impact de ces nouveaux concepts sur le bruit de combustion n'est actuellement pas une contrainte prise en compte lors de la conception. Avant d'envisager de réduire le bruit de combustion, il faut d'abord en comprendre les différents mécanismes. Cependant, proposer une méthode de prédiction pour le bruit de combustion n'est pas une tâche facile en raison des multiples interactions physiques impliquées lors des processus de combustion. De nombreuses expériences existent pour évaluer le bruit de combustion causé par les flammes ou des chambres de combustion simplifiées. Cependant, seuls quelques-uns considèrent le chemin de propagation complet du bruit de combustion provenant d'un moteur, car il est difficile d'isoler cette source acoustique du bruit des autres modules du moteur. Les méthodes empiriques basées sur des extrapolations et des simplifications sont souvent utilisées pour prédire le bruit de combustion des moteurs aéronautiques. De nombreuses analogies acoustiques ont également été dérivées à partir de Lighthill. Les travaux de cette thèse proposent d'étudier le bruit de combustion provenant d'un moteur d'avion à l'aide d'une chaine de calcul traitant différents modules de la génération du bruit de combustion à sa propagation en champ lointain. Ils mettent en évidence l'importance du bruit de combustion pour différents points de fonctionnement. Les mécanismes générateurs du bruit seront identifiés dans la chambre de combustion. Le rôle de la turbine en tant qu'atténuateur le bruit et générateur de bruit indirect sera évalué ainsi que la propagation en champ lointain en considérant des milieux inhomogènes. Enfin, uns stratégie alternative sera également proposée afin de considérer l'interaction entre le bruit de combustion et le bruit de jet. Pour se faire des LES de jet forcé par le bruit de combustion seront réalisées. Une nouvelle approche sera proposée à partir de ces résultats qui semblent montrer que le bruit de combustion a un impact sur la turbulence du jetSince the introduction of jet engine for aircraft propulsion in the 1950's, acoustics has become of great interest to the engine industry. While the initial turbojets were jet noise dominated, the introduction of turbofan engine in the 1960's gave relief in jet noise, but introduced fan noise. In the 1970's, with advanced noise reduction design features which provided a major reduction in aircraft noise, combustion noise became an interrogation. Indeed, more restrictive noise regulations could require that noise from the fan and jet be reduced to the point where combustion noise reduction may be required. Moreover, burner designs is controlled solely by the restriction of chemical pollutants produced by combustion, efficiency and consumption. The impact of these new concepts on combustion noise is not a strong constraint for design. Before considering to reduce combustion noise, it is necessary to first understand the different mechanisms. However, proposing a prediction method for combustion noise is not an easy task due to the multiple physical interactions involved during the combustion processes. Many experiments exist to evaluate the combustion noise from flames or combustion test rig. However, only a few include the complete propagation path of combustion noise within an engine device as it is difficult to isolate this acoustic source from the noise of the other engine modules. Empirical methods based on extrapolations and simplifications are often used for the prediction of combustion noise within modern aero-engines. Numerous acoustic analogies have also been derived from Lighthill. The work of this thesis proposes to study the combustion noise coming from an aircraft engine using a computational chain treating different modules from the generation of combustion noise to its propagation in far field. The importance of combustion noise for different operating points is highlighted. The noise-generating mechanisms will be identified in the combustion chamber. The role of the turbine as a noise attenuator and indirect noise generator will be evaluated as well as the far-field propagation considering inhomogeneous fields. Finally, an alternative strategy will also be proposed in order to consider the interaction between combustion noise and jet noise. To do so, LES of jet flow forced with combustion noise will be performed. A new approach will be proposed based on these results which seem to show that the combustion noise has an impact on the turbulence of the jet
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York, Martin A. S. M. Massachusetts Institute of Technology. "Turbofan engine sizing and tradeoff analysis via signomial programming/." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112383.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 79-80).
This thesis presents a full 1D core+fan flowpath turbofan optimization model, based on first principles, and meant to be used during aircraft conceptual design optimization. The model is formulated as a signomial program, which is a type of optimization problem that can be solved locally using sequential convex optimization. Signomial programs can be solved reliably and eciently, and are straightforward to integrate with other optimization models in an all-at-once manner. To demonstrate this, the turbofan model is integrated with a simple commercial aircraft sizing model. The turbofan model is validated against the Transport Aircraft System OPTimization turbofan model as well as two Georgia Tech Numerical Propulsion System Simulation turbofan models. Four integrated engine/aircraft parametric studies are performed, including a 2,460 variable multi-mission optimization that solves in 28 seconds.
by Martin A. York.
S.M.
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Eastbourn, Scott Michael. "Modeling and Simulation of a Dynamic Turbofan Engine Using MATLAB/Simulink." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1340582603.
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Ta, Vincent Hii Jiu. "Effective computation of acoustic propagation in turbofan aero-engine ducts." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427458.
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Dwyer, William J. (William Joseph). "Adaptive model-based control applied to a turbofan aircraft engine." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14056.
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Guimaraes, Bucalo Tamara. "Fluid Dynamics of Inlet Swirl Distortions for Turbofan Engine Research." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82921.
Full textAbstract:
Significant effort in the current technological development of aircraft is aimed at improving engine efficiency, while reducing fuel burn, emissions, and noise levels. One way to achieve these is to better integrate airframe and propulsion system. Tighter integration, however, may also cause adverse effects to the flow entering the engines, such as total pressure, total temperature, and swirl distortions. Swirl distortions are angular non-uniformities in the flow that may alter the functioning of specific components of the turbomachinery systems. To investigate the physics involved in the ingestion of swirl, pre-determined swirl distortion profiles were generated through the StreamVane method in a low-speed wind tunnel and in a full-scale turbofan research engine. Stereoscopic particle image velocimetry (PIV) was used to collect three-component velocity fields at discrete planes downstream of the generation of the distortions with two main objectives in mind: identifying the physics behind the axial development of the distorted flow; and describing the generation of the distortion by the StreamVane and its impact to the flow as a distortion generating device.
Analyses of the mean velocity, velocity gradients, and Reynolds stress tensor components in these flows provided significant insight into the driving physics. Comparisons between small-scale and full-scale results showed that swirl distortions are Mach number independent in the subsonic regime. Reynolds number independence was also verified for the studied cases. The mean secondary flow and flow angle profiles demonstrated that the axial development of swirl distortions is highly driven by two-dimensional vortex dynamics, when the flow is isolated from fan effects. As the engine fan is approached, the vortices are axially stretched and stabilized by the acceleration of the flow. The flow is highly turbulent immediately downstream of the StreamVane due to the presence of the device, but that vane-induced turbulence mixes with axial distance, so that the device effects are attenuated for distances greater than a diameter downstream, which is further confirmed by the turbulent length scales of the flow. These results provide valuable insight into the generation and development of swirl distortion for ground-testing environments, and establishes PIV as a robust tool for engine inlet investigations.Ph. D.
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Lucas, James Redmond. "Effect of BLI-Type Inlet Distortion on Turbofan Engine Performance." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23272.
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Boundary Layer Ingestion (BLI) is currently being researched as a potential method to improve efficiency and decrease emissions for the next generation of commercial aircraft. While re-energizing the boundary layer formed over the fuselage of an aircraft has many system level benefits, ingesting the low velocity boundary layer flow through a serpentine inlet into a turbofan engine adversely affects the performance of the engine. The available literature has only yielded studies of the effects of this specific type of inlet distortion on engine performance in the form of numerical simulations. This work seeks to provide an experimental analysis of the effects of BLI-type distortion on a turbofan engine\'s performance. A modified JT15D-1 turbofan engine was investigated in this study. Inlet flow distortion was created by a layered wire mesh distortion screen designed to create a total pressure distortion profile at the aerodynamic interface plane (AIP) similar to NASA\'s Inlet A boundary layer ingesting inlet flow profile. Results of this investigation showed a 15.5% decrease in stream thrust and a 14% increase in TSFC in the presence of BLI-type distortion. Flow measurements at the AIP and the bypass nozzle exit plane provided information about the losses throughout the fan flow path. The presence of the distortion screen resulted in a 24% increase in mass-averaged entropy production along the entire fan flow path compared to the non-distorted test. A mass-averaged fan flow path efficiency was also calculated assuming an isentropic process as ideal. The non-distorted fan flow path efficiency was computed to be 60%, while the distorted fan flow path efficiency was computed to be 50.5%, a reduction in efficiency of 9.5%. The entropy generation between ambient conditions and the AIP was compared to the entropy production along the entire fan flow path. It was found that the majority of entropy generation occurred between the AIP and bypass nozzle exit. Based on flow measurements at the bypass nozzle exit plane, it was concluded that inlet flow distortion should be located away from the tip region of the fan in order to minimize losses in a very lossy region. It was also determined that the fan and bypass duct process the different regions of the total pressure distortion in different ways. In some regions the entropy production decreased for the distorted test compared to the clean test, while in other regions the entropy production increased for the distorted test compared to the clean test. Finally, it was found that small improvements in total pressure and total temperature variation at the bypass nozzle exit plane will greatly improve the fan flow path efficiency and entropy generation, thereby decreasing performance losses.
Master of Science
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Achunche, Iansteel Mukum. "Acoustic optimisation and prediction of sound propagation in turbofan engine ducts." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/162395/.
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The research presented in this thesis explores the prediction of noise propagation and radiation in turbofan engine intakes and bypass ducts, and the optimisation of noise attenuation by using acoustic liners. A commercial FE/IE code ACTRAN/TM is used within two shell programs; B-induct for bypass ducts and ANPRORAD for intake ducts. An automated liner impedance capability has been demonstrated by exploiting an optimisation suite, SOFT. Automated liner impedance optimisations to maximise the liner insertion loss have been performed for a uniform bypass duct with a multimodal noise source, by using B-induct within SOFT. Results show that, multi-segment liners are effective at low frequencies when few acoustic duct modes are present and less so at high frequencies when many modes are present. Other results show that, at high frequencies, having different liner impedances on the inner and outer walls could be more effective than axially segment liners. An automated liner impedance optimisation has also been performed for a realistic bypass duct, and an A-weighting has been considered. Far field noise levels predicted by using ANPRORAD analysis have been validated against measured data from rig and engine tests. The predicted results are in good agreement with the measured data when the noise source is calibrated using in-duct measured values. This demonstrates that ANPRORAD is a viable methodology for intake noise predictions in industry. ANPRORAD has also been applied to investigate the effect of the intake geometry on low-frequency acoustic reflections in the intake, and integrated within SOFT to perform automated liner impedance optimisations to minimise acoustic reflections to the fan.
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Brooks, Christopher James. "Prediction and control of sound propagation in turbofan engine bypass ducts." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/52085/.
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This thesis contains original research into the propagation of sound in acoustically lined ducts with flow. The motivation for this work is the requirement to predict the sound attenuation of acoustic liners in the bypass duct of modern turbofan aeroengines. The liners provide the most effective means with which to suppress the rear fan noise. It is therefore important to make the best possible use of the available lined area by optimising the liner configuration. A set of analytic and numerical methods for predicting the liner attenuation performance have been developed, which are suitable for use in intensive liner optimisation studies, or as preliminary design tools. Eigenvalue solvers have been developed to find modal solutions in rectangular ducts with uniform flow and annular ducts with sheared flow. The solvers are validated by replicating results from the scientific literature and the Finite Element method. The effect of mean core flow radial profile and boundary layers on the mode eigenfunctions and axial decay rates are considered. It is shown that solutions for thin boundary layer flows converge to those based on the commonly used slip flow boundary condition. It is demonstrated that realistic flow profiles should be used to assess acoustic mode propagation in bypass ducts. The flow profile can have strong effects upon low order modes and surface waves, and in fact at high frequencies, the profile can affect all the modes. Mode-matching schemes are developed to assess the power attenuation performance and modal scattering of finite length liners. The results of the schemes are used to show that refraction of sound by boundary layers increases attenuation at high frequency. Power attenuation is higher where the mean core flow gradient refracts sound towards the liner. It is found that asymmetric liners can provide improved attenuation, depending on the direction of the mean flow shear gradient. The optimisation of axially-segmented liners for single and multi-mode sources is demonstrated. It is found that potentially large improvements in the attenuation of tonal noise is possible, whilst benefits for broadband noise are more difficult to achieve.