Study On The Environment And Operation Mode Of Primary Air System And Oxygen Supply System For Qinghai-Tibet Railway Passenger Train In Winter

The natural environment along the Qinghai-Tibet railway has characteristics of low pressure,low temperature and oxygen deficit,which puts forward higher requirements for the air conditioning system of the Qinghai-Tibet railway passenger train running in winter.When the passenger train runs at high altitude,in order to meet the demand of oxygen level and the control of pollutant concentration,it is very necessary to install an oxygen generating system and provide enough fresh in the train.And the relationship between the fresh air and the oxygen supply is mutually restricted,so the air conditioning system of the Qinghai-Tibet railway passenger train should take combined regulation of the oxygen supply and the fresh air.The current operation mode of the air conditioning system synchronized with the fresh air and the oxygen supply is applied,in which the fresh air and the oxygen supply are regulated by feedback.However,there are problems such as time lag,fluctuation and instability in this operation mode,which would result in the reduction of the oxygen utilization and the waste of energy.Study mainly focus on the air quality inside and different operation modes with the methods of investigation,numerical simulation and theoretical calculation in order to lay equal stress on energy saving and comfort.Firstly,the influence of different concentrations of carbon dioxide and oxygen on human body was analyzed.Combined with the existing standards,the allowable value concentrations of carbon dioxide and oxygen inside were given by using partial pressure as control index.And then,the air quality and passenger comfort in the carriage were investigated in winter,and the survey results showed that the air quality and passenger comfort of the investigated train carriage are poor,which indicates that the current operation mode of fresh air system and oxygen supply system can not meet the thermal environment conditions,sanitation standards and the requirements of oxygen partial pressure.Secondly,the numerical model of thermal environment and air quality in the hard seat carriage of 25 T Qinghai-Tibet railway passenger train was established by using FLUENT software and RNG k-? turbulence model.Through the unsteady simulation calculation,the distribution of velocity field,temperature field,concentration fields of carbon dioxide and oxygen and the time needed to achieve steady state of each parameter were obtained.Finally,by comparing and analyzing the calculation results of energy consumption and air quality inside under combined operation mode of continuous,intermittent and frequency conversion,the suggestion was given that the frequency operation mode of different oxygen supply sections based on altitude.This operation mode can not only avoid frequent start and stop actions of unit,but also effectively improve the utilization rate of oxygen supplement and reduce the system energy consumption on the premise of meeting the requirements of concentrations of carbon dioxide and oxygen in the carriage,which is of great practical significance for improving the efficiency of ventilation and oxygen supply of the Qinghai-Tibet railway passenger train.