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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Design of a particle separator for a helicopter engine inlet


Year: 2005

Supervisor(s): Chris Lawn

The aim of this thesis is to present the design of an axisymmetric inlet particle separator for use on military combat helicopters operating in desert environments, with a separation efficiency superior to current designs. Two samples of desert sand were analyzed to determine the shape and size distribution of their particle constituents. The design process required the use of an advanced code that is capable of producing valid solutions for the complex flow through this axisymmetric separator. Thus, before starting this design process, a reputable code had to be tested by analyzing a flow of comparable complexity such as the flow through a sudden expansion.

Therefore, isothermal unswirled and swirled flows through an axisymmetric sudden expansion were simulated numerically using both k-e and RSM turbulence models. The sudden expansion ratio was 4. Profiles of the radical distributions of the normalized mean axial velocity were compared with the corresponding experimental data from the open literature at several axial locations. These profiles compared favourably.

Once validation was accomplished, the code then was used to analyse the flow through this separator and hence start the design process. Before starting this process, a theoretical review of the forces affecting the particle trajectories through the separator had to be carried out in order to determine the appropriate drag model. Several designs were attempted by contouring the inner and outer walls and adjusting the size of the inlet and outlet of the separator approximately to accommodate the specified mass flow rate of this design.

Once a valid design had been obtained, the next step was to build a glass scaled-model of that design and test it. Several sizes of sand particles were injected into the glass model to determine its separation efficiency. The movements of some of these particles through the separator were captured using a high-speed camera with an image intensifier. The flow through the glass model was simulated and the comparison of experimental and simulation results for this scaled model gave a clear indication of the reliability of the code and the choice of drag model to simulate the flow and predict particle trajectories within the separator.