Optimization of cabin return air ratio based on air quality and compensation loss

In order to obtain better air quality and improve the energy saving level of cabin air conditioning, computational fluid dynamics (CFD) method was used to establish a simulation model of the economy class of Boeing 737 passenger aircraft, and particle image velocimetry (PIV) technology was used to verify the accuracy of the simulation model. Based on this model, the effects of different return air ratios on the CO₂ concentration field in cabin air conditioning were studied, and the ventilation efficiency index of the passenger breathing area was used to evaluate the effects of different return air ratios on cabin air quality. The fuel compensation loss under various return air proportion conditions with the same air supply volume was also calculated using the total takeoff mass method, and a functional relationship between the fuel compensation loss, the ventilation efficiency of the passenger breathing area, and the return air proportion was fitted. The efficiency coefficient approach was used to design the evaluation function, and the ideal return air proportion for the cabin air conditioning system was 64.864%. This method can provide a basis for the proportional control of return air in cabin air conditioning.