The thesis proposes an overall performance estimation procedure for a new turbo-rotary compound engine (TURC) and an associated novel thermodynamic cycle. In this engine, two or multiple spools are lined up in series within the engine. In the front spool, positive displacement rotary vane type turbines drive axial compressor the performance of which were estimated using stage stacking calculations. In the back spool, axial turbine stages drive positive displacement rotary vane type compressors, the performance of axial turbine was predicted by series matching of turbine stages. Two air streams feed separately the customary turbo components and the rotary vane components, respectively. Accordingly, the primary high mass flow through the axial compressors and turbines undergoes Bryton cycle, where as the secondary, low mass flow through the positive displacement rotary components is mainly undergoes Akmandor cycle, which is a novel thermodynamic cycle. The energy consumed internally by the engine is minimized because less input shaft power is needed for the rotary vane compressors and higher inlet temperatures and less cooling can be tolerated by the intermittent combustion rotary vane turbines. The result is a radical improvement in both efficiency and net power output. But this result can be estimated, since the novel engine is the combination of a high efficiency internal combustion engine and high performance gas turbine engine. Aerothermodynamics and spool matching calculations comparing a T56-A14 core with a TURC of similar size and compression ratio show that the new engine provides superior performance characteristics by increasing the net output work by 100% and decreasing the specific fuel consumption by 20%.

As improving the performance of turbofan designs becomes increasingly difficult, manufacturers are looking to new technologies for the next generation of jet engines. An 'open rotor' replaces the fan of the turbofan with a set of external rotors. This has the potential to offer a significant improvement in propulsive efficiency, but the design for low noise is a key challenge. Hence, high fidelity noise prediction methods are needed to accurately predict and compare the noise of different designs. This thesis focuses on one set of methods based on the Ffowcs Williams-Hawkings (\fwh) equation. This equation is considered to be the most realistic description of aeroacoustic noise generation, as it is a direct rearrangement of the Navier-Stokes equations. The \fwh\ equation is difficult to solve for realistic test cases such as an open rotor, and is susceptible to several types of error. This thesis categorises these errors as ``input'', ``neglection'' and ``discretisation'' errors. Discretisation errors arise from the need to integrate a discretised source field for the total noise, neglection errors result from needing to ignore part of the source field for practical reasons, and input errors relate to any errors caused by inaccurate input to the solver. The fundamental motivation of this thesis is to advance the understanding of neglection and discretisation errors and how they can be mitigated, in order to develop best practice solvers and methodologies for application to open rotors. Dimensional analysis is combined with analytical flow solutions to develop a process for isolating and quantifying discretisation errors. This process is used to study a wide range of solver methodologies and select a best practice solver methodology for open rotor noise prediction. This first-of-a-kind study produces a solver methodology that reduces discretisation errors by an order of magnitude compared to an industry standard solver. Previous research into neglection errors has shown that avoiding density perturbations in acoustic source terms can be beneficial. This thesis uses a generic aeroacoustic analogy to provide a new, physically intuitive method of incorporating a surface discontinuity that enables density perturbations to be avoided in a far more elegant manner than previous research. The above method improvements are investigated using a modern open rotor rig test case. The results demonstrate that discretisation and neglection errors can be severe in realistic cases and the potential of the method improvements to significantly mitigate them.

Les travaux de cette thèse, réalisés au sein de l’équipe CLEF/DMFN de l’ONERA (Office National d’ Etudes et de Recherches Aérospatiales) en partenariat avec le laboratoire DynFluid et le CIRT (Consortium Industrie-Recherche en Turbomachines) s’inscrivent dans une demarche d’amélioration des outils de simulations pour les turbomachines. Compte tenu de ce contexte, l’objectif de cette étude est de développer de nouvelles méthodes pour le traitement des raccords non coincidents dans les turbomachines qui soit à la fois d’ordre elevé et conservatifs. Les développements proposés sont validés et composés de configurations de difficulté croissante. / A high-order and conservative method is developed for the numerical treatment of interface conditions in patched grids, based on the use of a ctitious grid methodology. The proposed approach is compared with a non-conservative interpolation of the state variables from the neighbouring domain for selected internal fow problems.

The noise (unwanted sound) from fans of all sizes, operating in close proximity to people, can be a design constraint due to annoyance or, in the worse cases, health damage. Of the total noise, aeroacoustic noise - produced by unsteadiness in the air - often represents a significant source and is intrinsically linked to the aerodynamic features of the flow field. In this work, the aeroacoustics of low-speed fans are investigated using a compact mixed-flow fan as a test case. The low-speed regime is less developed compared to large-scale, high-speed machines and is increasingly relevant to applications such as micro air vehicles, small wind turbines, and other environmental comfort technologies found in buildings or vehicles. The test case fan Reynolds number is of the order of 104 which is a couple of orders lower than those generally found in gas turbines. Its main sources are therefore best identified experimentally in the absence of proven alternative methods. In order to do this, a way of quantifying fan noise is developed in tandem with control of the aerodynamic operating point. Following a study of sources of the significant broadband and tonal noise, a low-order noise prediction scheme is developed and applied to predict tonal noise with reference to Reynolds number effects. The new, duct-based rig and method has several advantages over the existing sound power measurement rig built to the ISO 5136 standard at Dyson. The approach, which makes no assumptions about the relative power of different modes, has resulted in a rig that is much shorter. Unlike the ISO rig, it is capable of accurate narrow-band tone measurements with sources which excite strong non-plane-wave duct modes (as the modal structure of the sound is determined) for the frequencies of interest. Tests have been carried out at different operating points with a range of geometry modifications produced with 3D printing techniques. In terms of tonal sources which particularly impact sound quality, the mixed-flow impeller alone produces tones due to very high sensitivity to inflow distortion of the mean flow (giving unsteady blade loading). This means that the product inlet must be designed very carefully to optimally condition the flow. Periodicity in the impeller outlet flow produces rotor-stator interaction tones even with a number of guide vanes chosen to satisfy the Tyler-Sofrin theory cut-off criteria. This is thought to be due to abrupt radius change after the guide vanes in the rig (while the theory assumes constant radius). In the product, abrupt radius change also occurs. The sensitivity of the broadband level to inflow turbulence was confirmed to be low in the rig, although the in-product inflow appears much less ideal. The main broadband noise source in rig tests is suggested to be impeller self-noise as only small reductions in rotor-stator interaction noise are achieved with far fewer vanes. The low-order modelling scheme to understand the fundamental unsteady loading noise mechanism compares well to experiments for sample rotor-stator interaction tones. The velocity fluctuations which induce this noise, measured experimentally with a 2D hotwire, are shown to increase in intensity as Reynolds number is reduced towards 104. This is due to a higher importance of viscosity which can give boundary layers that are thicker and liable to laminar separation. Surface treatments such as boundary layer trips could be used to prevent such separation and potentially reduce noise. Based on the thesis findings, further tests, simulations and possible design modifications are suggested to understand and reduce the important noise sources.

<p>To increase overall aircraft engine efficiency, the diameter of the high-pressure turbine is reduced, leading to low aspect ratio airfoils. Secondary flow dominates in these low aspect ratio turbines, and the small airfoil geometry inhibits flush-mounted, full-spatial dynamic pressure measurements with pressure transducers. Airfoil surface pressure measurements are vital to understanding the inherently unsteady flow phenomena in turbines. Additionally, aerodynamic performance data derived from high-resolution surface pressure measurements provide invaluable data for validating computational fluid dynamics codes used for prediction. Non-intrusive measurement techniques such as fast-responding Pressure Sensitive Paint (PSP) offer a potential solution of a full-field optical measurement of surface pressure fluctuation, with each camera pixel representing a sensor. The porous binder improves the dynamic response of PSP, making it suitable for unsteady flow environments such as turbomachinery applications. In this view, the overall objective of the current doctoral research is to develop a lifetime PSP method using laser-based excitation for surface pressure measurement on a new class of high-pressure turbines. </p> <p>The overall research goal was subdivided into three main strategies. (1) A pulse lifetime calibration procedure of a porous polymer/ceramic binder PSP was developed in a pressure-controlled chamber to assess the correlation between pressure and time-resolved luminescent lifetime, pressure sensitivity, and signal-to-noise ratio. (2) The lifetime technique was implemented for surface pressure measurements in a linear test section to measure high spatial pressure gradients and resolve unsteady flow features. A data reduction routine and an optimal binning bundle of pixels were proposed for calibration analysis to reduce the overall pressure uncertainty. Uncertainty quantification and sensitivity analysis were also completed to determine the parameters with a substantial effect on the pressure uncertainty. (3) The pulse lifetime method was demonstrated on a high-pressure turbine vane suction surface at engine representative conditions. The surface pressure data were corroborated with static pressure tappings and computational simulations. This research effort provided new insights into time-resolved luminescent lifetime PSP techniques. Steady and unsteady flow features from surface pressure measurements were identified using a precise calibration method. The lifetime pulse method was effective in a high-pressure turbine flow field, paving the way for back-to-back PSP experiments with different turbine geometries. </p>

<p>This thesis addresses the development and implementation of an experimental methodology for turbine rotors which enables experiments to be performed in the stationary frame. This method enables measurements with increased spatial resolution and reduced probe blockage effects while also reducing the cost and complexity of the experimental apparatus. Adding this experimental method to the turbine designer’s toolbox will enable more rapid design evaluation and iteration, resulting in faster and less expensive development cycles for new turbine designs. To demonstrate the viability of this new methodology it has been used to evaluate a family of high-lift, high-diffusion turbine geometries in a rainbow ring in the Big Rig for Aerothermal Stationary Turbine Analysis (BRASTA) facility at Purdue University.</p>

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In aeromechanical design one of the major rules is to operate under High Cyclic Fatigue (HCF) margins and away from flutter. The level of dynamic excitations and risk of HCF can be estimated by performing forced response analyses from blade row interaction forces or Low Engine Order (LEO) excitation mechanisms. On the other hand, flutter stability prediction can be assessed by calculation of aerodynamic damping forces due to blade motion. In order to include these analyses as regular practices in an industrial aeromechanical design process, interaction between the fields of fluid and structural dynamics must be established in a rather simple yet accurate manner. Effects such as aerodynamic and structural mistuning should also be taken into account where parametric and probabilistic studies take an important role. The present work presents the development and validation of a numerical tool for aeromechanical design. The tool aims to integrate in a standard and simple manner regular aeromechanical analysis such as forced response analysis and aerodynamic damping analysis of bladed disks. Mistuning influence on forced response and aerodynamic damping is assessed by implementing existing model order reduction techniques in order to decrease the computational effort and assess results in an industrially applicable time frame.  The synthesis program solves the interaction of structure and fluid from existing Finite Element Modeling (FEM) and Computational Fluid Dynamics (CFD) solvers inputs by including a mapping program which establishes the fluid and structure mesh compatibility. Blade row interaction harmonic forces and/or blade motion aerodynamic damping forces are inputs from unsteady fluid dynamic solvers whereas the geometry, mass and stiffness matrices of a blade alone or bladed disk sector are inputs from finite element solvers. Structural and aerodynamic damping is also considered. Structural mistuning is assessed by importing different sectors and any combinations of the full disk model can be achieved by using Reduced Order Model (ROM) techniques. Aerodynamic mistuning data can also be imported and its effects on the forced response and stability assessed. The tool is developed in such a way to allow iterative analysis in a simple manner, being possible to realize aerodynamically and structurally coupled analyses of industrial bladed disks. A new method for performing aerodynamic coupled forced response and stability analyses considering the interaction of different mode families has also been implemented. The method is based on the determination of the aerodynamic matrices by means of least square approximations and is here referred as the Multimode Least Square (MLS) method. The present work includes the program description and its applicability is assessed on a high pressure ratio transonic compressor blade and on a simple blisk. / QC 20110324 / Turbopower / AROMA