Numerical Simulation Of Mixing Ventilation In A Commercial Airliner Cabin

Nowadays, more and more people are travelling by airliners than ever before,and the travelling public is becoming more sensitive to the cabin environment. Underthe extreme conditions, the environmental control system in aircraft cabin is used toprovide a healthy and comfortable cabin environment for the passengers and crew.The air distribution system is important as a component of environmental controlsystem. Currently, researches on air distributions are advanced in foreign countrieswhile study on cabin environment is in the initial stage in China. Combined with thedevelopment of China’s large aircraft project, this paper will carry on mixing airdistribution systems in airplanes, including the current air distributions such as twoinlets mixing air distribution system which supply air from inlets near luggage, thethree inlets mixing air distribution system which supply air from inlets near luggageand inlets on the ceiling, and the new four inlets mixing air distribution systemproposed which supply air from inlets near luggage and inlets on the tops of walls.Computational fluid dynamics (CFD) was used as a research method. This studyfirst validated the unsteady RNG k-ε model with the experimental data of airflowfrom the real airplane MD82. Then, the two inlets, three inlets and four inlets mixingair distribution systems were designed for a simulated commercial cabin. Thevalidated CFD program combined with orthogonal test was used to optimize airsupply parameters for the three mixing air distribution systems. According to theASHRAE Standard, the best air supply parameters were established. To compare thethree mixing air distribution systems, on one hand, the study investigated theirperformances on air heating before flying in winter. On the other hand, thermalcomfort of passengers with different air distribution was analyzed when the airplanewas at cruise. The vertical temperature, heating time were used to evaluate theperformances on heating condition. The air velocity, temperature, Predicted MeanVote (PMV) and Draft Rate (DR) were used to judge the thermal comfort at cruise.The results showed that the unsteady RNG k-ε model can be used to predict theairflow in aircraft cabin for its accuracy and rationality. Orthogonal test methodgreatly reduced the quantity of tests, such as the four inlets air distribution, workload can be reduced by92.6%. Therefore, orthogonal test method combined with CFDwould be favorable for the air distribution optimization in aircraft cabin, and it couldbe used in our optimized design. The three inlets mixing air distribution system costshortest time to heat air in the cabin and the vertical temperature was lowest as wellon heating condition, the four inlets system had a middle performance while the twoinlets system was the worst. Meanwhile, when the airplane was at cruise, the fourinlets system created the most comfortable thermal environment with PMV mostlyclose to0and the lowest DR, the second was two inlets air distribution while the threeinlets system was the last. Consequently, the four inlets system was the best and wasrecommended to be used in commercial airplanes.