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The company Safran Aero Boosters for which this master thesis was conducted is the world leader in conception of low-pressure compressors, also called boosters, for commercial turbofan engines. In a search of continued improvement, the engineers of the company are regularly confronted to the aerodynamic design of blades, a time consuming iterative procedure between the aerodynamics and mechanical teams. Within the conception process, the design space exploration consists in carrying out small modifications to a reference blade and then reassess its performances with long running CFD computations until finding the optimal one. In order to spare computational cost and time, metamodels could be used instead. Constructed on a limited database obtained with CFD computations, the metamodels give predictions on blade performances in an instant and can be intensively employed with optimisation algorithms. 

The main objective of this master thesis is to gain experience in the optimal construction of metamodels. In this context, highly predictive metamodels have been constructed on a large database and the relationships between the design variables modifications and blade performances analysed. In an attempt to reduce the computational cost associated to the creation of metamodels, a comparison of their predictability was made when they are constructed on alternative databases of reduced size. This study concluded that a database of 20 elements obtained with the Latin Hypercube sampling method appeared to be the most adequate choice in this application. 

After that, an enlargement of the design space was considered as modifications on the initial blade induced changes in other design variables. This enlarged design space was once again explored with the metamodels constructed this time with a reduced size database, result of the previous comparison, and with CFD computations on a smaller domain. In fact, with the reduced domain, the blades too different from the initial one encountered issues in convergence of their CFD computations. Nevertheless, the surrogate models were sufficiently predictive for this work and optimised blades were determined. Among those ones, the blade for which was predicted an improvement of both efficiency and operability satisfied all expectations. To finish this thesis, an analysis of the flow around these optimised blades was conducted in order to better understand the reasons behind the performances improvement with the blade geometry modifications.

Metamodeling --- Optimisation --- Aerodynamics --- Booster --- Ingénierie, informatique & technologie > Ingénierie aérospatiale

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Malaria --- International Agencies --- Paludisme --- prevention & control --- Booster Program for Malaria Control in Africa. --- World Bank.

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In aeronautics, the mass reduction objective and the performance improvements lead to optimize increasingly the engine components. These optimizations constitute a challenge for the design methodologies and the mechanical dimensioning criteria for the engine manufacturers. In the case of compressors in turbomachine, the thicknesses of the booster outer shrouds as well as the flanges are designed under event of Fan Blade Out (or FBO for short). The FBO load case is designing for booster casing thicknesses, therefore the ability to predict and simulate the casing under a FBO event is critical to improve the booster weight. Thanks to the improvement and the development of numerical methods in rapid dynamics within Safran Aero Boosters, the understanding of mechanical phenomena is upgraded and increases the loading reliability applied on the booster casing.
This work focus on the different methods to compute the casing mechanical behavior and to identify the most relevant one in order to design the casing in future developments. The assessment of existing design methods within SAB allows the identification of a so-called current method, that couples LS-DYNA (to define the load) and Samcef MECANO (to validate the strength) simulations and a so-called proposed method, that uses a LS-DYNA implementation alone to assess the FBO loads and strength of the booster casing.
This work aims at validating the proposed method. To that end, a nonlinear static Samcef MECANO model is implemented to perform FBO calculation and assess the booster casing strength. The good reliability between the simulation results obtained by the SAB teams in charge of the LS-DYNA model and the FBO certification test results was highlighted. The comparison between LS-DYNA and Samcef MECANO results emphasizes more constraining mechanical quantities undergone by the casing under FBO loading and demonstrates a greater interest in using the proposed method to design the booster casing.

Fan blade out --- Booster --- Casing design --- nonlinear simulation --- Ingénierie, informatique & technologie > Ingénierie aérospatiale

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The recent implementation of wear models in the nonlinear solver LS-Dyna allows its use in the numerical simulation of Rotor-Stator Interaction for the very first time. The new capabilities of the solver are studied and are compared to the ones of nonlinear solver Metafor, already capable of simulating Rotor-Stator Interaction. Specifically, the feasibility of such simulations is studied, the best suited contact algorithms are selected, and the performance is assessed. To that end, two LS-Dyna models are developed: a basic ONERA test bench whose purpose is to select the most adequate contact models, and a compressor blade rub test whose purpose is to ensure the correct application of wear on the finite elements model. The choice of contact model is constrained by the limited support of wear in the solver. Penalty methods for contact were considered, double-pass algorithms were rejected due to high variation of contact loads, leaving single-pass algorithms. The penalty computation was selected to ensure the least dependence on the mesh. Soft constraint formulation is not fully independent of the mesh, but offers nodal mass normalization. The specificity of wear computation in LS-Dyna is its application in post-processing only, preventing wear affecting the compressor blade dynamics. The simulation of Rotor-Stator Interaction in LS-Dyna thus necessitates extensive use of computation stops and restarts. A fully functional method to compute Rotor-Stator Interaction was successfully developed for LS-Dyna, with performance similar to Metafor.

metafor --- ls-dyna --- dyna --- interaction --- rotor --- stator --- compressor --- wear --- contact --- divergence --- vibration --- safran --- aero --- boosters --- booster --- engine --- low --- pressure --- onera --- model --- finite --- elements --- nonlinear --- explicit --- implicit --- time --- integration --- solver --- gap --- close --- open --- abradable --- material --- Ingénierie, informatique & technologie > Ingénierie aérospatiale

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Refrigeration, air conditioning, and heat pumps (RACHP) have an important impact on the final energy uses of many sectors of modern society, such as residential, commercial, industrial, transport, and automotive. Moreover, RACHP also have an important environmental impact due to the working fluids that deplete the stratospheric ozone layer, which are being phased out according to the Montreal Protocol (1989). Last, but not least, high global working potential (GWP), working fluids (directly), and energy consumption (indirectly) are responsible for a non-negligible quota of greenhouse gas (GHG) emissions in the atmosphere, thus impacting climate change.

demand side management (DSM) --- energy efficiency --- energy storage --- demand response (DR) --- flexibility --- R744 transcritical booster --- subcritical booster --- cascade --- parallel compression --- ejector --- commercial/retail refrigeration --- HVAC --- pressure based control --- damper control --- static pressure reset --- CO2 reset --- demand-based control --- energy saving --- human well-being --- IAQ --- Atomic Air --- air conditioning --- chiller --- CO2 --- commercial refrigeration --- heat pump --- heat recovery --- industrial refrigeration --- R744 --- transcritical vapor-compression system --- two-phase ejector --- domestic refrigerator --- consumer habits --- energy consumption --- good practices --- surveys --- ground source heat pump --- tropical climate --- horizontal heat exchanger --- district cooling --- liquid to compressed natural gas --- thermal energy storage --- LNG --- ground source heat pumps --- low GWP refrigerants --- energy analysis --- R410A --- R32 --- R454B