| The environmental control system of the airlcraft(ECS)plays an important role in providing passengers with a safe,healthy and comfortable cabin environment.The fresh air is 50% of total supply air and there are no high efficiency particulate air(HEPA)filters used for it.The fresh air from the outside from the engine system(engine)or the auxiliary power system(APU)goes into the aircraft environmental control system without high efficiency filtered,particles deposit in the air conditioning package will affect the heat transfer.In this case,the air pollution and the aircraft in the ground of the residence time of the aircraft environmental control system has a great impact on the ECS.Chinese air pollution and the need to wait too long in the ground,resulting in a large number of particles will enter the air conditioning package,and deposit in the heat exchanger and turbine,due to the complexity of the internal structure of such components,there might be a large particle deposition,greatly reducing the heat exchanger and air circulation heat transfer efficiency.At present,there are some studies on particle deposition in the ECS,but the conclusion is still very one-sided and not convincing.The subject of this paper is to explore the complex components of ECS: the particle deposition measurement of the heat exchanger and turbine.The experimental method selection is according to the literature review and experimental equipment in our group.The isokinetic sampling method with the filters weighing method is used for experimental study.To make measurement condition the same as the actual flight conditions,and the selections of experimental measurement of objects and the heat exchanger and turbine of aircraft are basically the same.The aerosol generator generated particles of different particle sizes in each experiment.At least three repetitive experiments to ensure the accuracy of the results,and finally obtain the particle deposition measurement result in the heat exchanger and turbine.We use some theoretical knowledge and some other experimental results to analyze the reliability of the results.At last,the accuracy of the ECS numerical model is further improved by the measurement result.At the same time,some suggestions and judgments about the frequency and maintenance of aircraft heat exchanger and turbine replacement are provided to the future researchers.The conclusions of this paper are as follows: This investigation built a test rig to measure particle deposition in complex components of ECS,such as heat exchanger and turbine.The particles tested were with different size ranging from 1 μm to 8 μm.The results showed that particle deposition rate was higher with the particle size increased for both the heat exchanger and turbine.Due to the complex geometry of the heat exchanger,the highest deposition rate was 10% for 1 μm particles and 95% for 8 μm particles.When the turbine rotated at a high speed,the particle deposition rate was higher than that in the heat exchanger because of the centrifugal force.The experimental data of the heat exchanger and turbine was useful for improving the estimate of the particle deposition in each component of the ECS.The relative error was reduced by at least 50%. |
