Thermal Analysis Of APU Compartment Of Passenger Plane Based On CFD

All components in APU compartment of passenger plane produce heat and disperse heat by convection and radiation, so the design of the cooling system is particularly important. The changing of the shapes and sizes of cooling system can improve on cooling efficiency in a certain extent, in condition of APU is not modified the internal structure and removed the installation site. The APU exhaust system is the greatest impact on the distribution of heat flow in APU compartment, and spurt out high-temperature gas about 1000K from the turbine. At first, the paper emphasized on the local model of APU compartment, APU exhaust cooling system, put forward a variety of improvement scheme, and contrasted the calculating data. The best election of cooling efficiency in cooling system schemes was merged into the whole calculation model.For the study of influence of cooling air injection holes and injection slot of the auxiliary power unit (APU) exhaust system and shape of the plane tail fairing on cooling effectiveness, 13 numerical computation models with different injection hole location and slot size and different plane tail fairing shapes, in which realizable k-εturbulent model and DO thermal radiation model were incorporated with, were set up by using commercial CFD software Fluent for calculating flow and heat transfer in the APU exhaust system, and the flow field, temperature field and heat flow distribution were acquired The calculation results show that the size of cooling air injection slot, parameters includes location, shape, and area of injection hole, and back commutated cover take important roles in cooling system. The whole model use parameters of local model #2 and #5 which were the best cooling efficiency model. In order to study heat transfer process in APU compartment of passenger plane and to perform structure thermal analysis, temperature field of APU compartment is calculated using numerical method. The computation model of flow and heat transfer process in APU compartment was set up by commercial CFD software Fluent, Realizable k-εturbulent model and S2S thermal radiation model were used, and the flow field, temperature and heat flow information were acquired. Radiation heat transfer is the major heat transfer process in APU compartment; APU fireproofing cover and heat insulation hood of exhaust pipe function as radiation heat shielding screens; and APU cooling air in the APU fireproofing cover plays an important part in decreasing the temperature of the fireproofing cover; the injection cooling air in the exhaust pipe reduced the wall temperature effectively.