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The main objective of this work is to investigate, by means of numerical simulations, the performance of the engine nacelle ventilation cooling system of a helicopter under hover and forward flight conditions, and to propose a simplified method of evaluating the performance based on rotor downwash flow by taking the synthetical effect of engine nacelle, exhaust ejector and external flow of a helicopter into account. For the engine nacelle of a helicopter, an integrated model of the nacelle and exhaust ejector was set up including the domain of external flow. The unstructured grid and finite volume method were applied for domains and control equations discreteness, and the standard k-ε model was applied for solving turbulent control equations. Using the business CFD software, the flow field and the temperature field in the nacelle were calculated for single inlet scheme and double inlets scheme, total up to 9 schemes. The performance of the exhaust ejector was computed.

Five design schemes of helicopter nacelle ventilation cooling system were proposed to provide efficiently cooling for the nacelle. In order to evaluate the cooling effect of these design schemes, the characteristic of airflow and heat transfer in the nacelle was numerically calculated by a general CFD software. Unstructured mesh and finite volume method (FVM) were applied for calculation regions and governing equations discreteness, and standard k - ε model was adopted to solve turbulent governing equation. For five schemes of nacelle cooling system, the influence of cooling air inlet size, position, mass flow rate and ambient temperature under hover condition on the flow and temperature field distributions was discussed. Also transient calculations were carried out when the engine was shut down. The results provided a theoretical basis for design and optimization of nacelle ventilation cooling system.