An Investigation On Aircraft Thermal Management System And Thermal Comfort In Cockpit

The study on aircraft thermal management system and thermal comfort in cockpit will be helpful for solving the heat sink shortfall problem,improving the thermal comfort for the pilot and increasing the performace of the system.In this paper,numerical investigations of the aircraft thermal management system and thermal comfort in cockpit have been carried out.The aerodynamic heat and thermal comfort have been studied.The new heat sink technology has been analyzied.And the multi-objective optimization of the thermal management system with thermal comfort and fuel compensation has been done.The results and conclusions are described briefly as follows:(1)The aerodynamic heating has been investigated based on RANS and SAS numerical method.Results show that the temperature of aerodynamic heating is uneven on the forebody,and the temperature near the cockpit canopy is high.This is caused by the compression and expansion phenomenon of airflow bypassing the cockpit.On the wing,the temperature is relatively consider as uniform distribution.The temperature near trailing edge of the wing is rise because of the compression wave and vortex shedding.(2)The thermal comfort of aircraft has been investigated based on theoretical method and numerical analysis.The evaluation index of thermal comfort(PMV_F)with solar radiation,sky radiation and et al is builded for predicting the thermal comfort of pilot in a fighter.Results show that the altitude is higher and the Mach number is smaller,the thermal comfort is better.And when the Mach number reachs 2.0,the PMV_F on the head and shoulder cannot meet the thermal comfort requirement.(3)To solve the problem of heat sink shortfall in liquid cooling system,especialy on return voyage,some new ways of obtaining the air heat sink have been investigated.Results show that on the subsonic flight,the ram air flow rate can be increased as much as 58.5%.The technology of ejecting can enhance the momentum-transport in ram air intake,and increase the air flow rate.On the supersonic flight,the ejector will debase the momentum-transport,and reduce the air flow rate.The research also show that the Nusselt number of the main cold liquid side in the annular radiator changes little.But the Nusselt number of the second liquid side is changed a lot by different second cold flow channel shape.Different channels cause different vortex motion,and lead to the difference in heat exchange.By the study on the optimization,it shows that the arch shape is better than the rectangle shape,and the heat transfer rate can be improved 39%.(4)The aircraft thermal management system and its multi-objective optimization(MOP)based on thermal comfort have been investigated.Results show that the long time flight(more than 45 minutes)will make the temperature of fuel in tank exceeding the standard(over 40 degrees),and the ram air can cold it down to the safe range.The MOP results show that the syetem can reach the best performance when the engine bleed air flow rate is 0.22kg/s,the ram air flow rate is 0.20kg/s,the efficiency of the primary heat exchanger is 0.85 and the efficiency of the second heat exchanger is 0.9.Among them the efficiency of secondary heat exchanger has the greatest influence on the performance of the system.At the same time,the fault diagnosis and fault analysis of the air condition system have been investigated.It is found that the fault detection rate can be increased from 91.4% to 100%,the fault isolation rate can be rosed from 32.9% to 83.9% by increasing the measuring point in turbine components.