Study On Operation Mode Of Train Air Conditioning System In Qinghai-Tibet Railway (Golmud-Lhasa Section)

Qinghai-Tibet Railway is the railway with the highest altitude and the longest route in the world.Due to its harsh climate along the way,it has brought many difficulties to the operation of the Qinghai-Tibet Railway.The thermal environment of the railway has a great impact on not only the passengers'physical and mental health but also the comfort of the passengers,and the thermal environment is closely related to the airflow organization inside the train.Therefore,how to design the air conditioning system of the Qinghai-Tibet railway train reasonably has paramount meanings to ensure the train's normal operating and the passengers'safety.The main works of this paper are as follows:?1?In this paper,the 25T type Z6811 train is taken as the research object.Under the influence of solar radiation,the calculation method of Z transfer function is adopted.According to the weather conditions outside the train and the influence of solar radiation on heat transfer,the train's envelope structure thermal boundary conditions of the train passing through different stations are obtained in the Gera section?Golmud-Lhasa?in summer.?2?Based on the RNG k-?model,the flow field,temperature field,CO₂ and O₂concentration field distribution of the train during the summer operation of the Gera section are studied.The results show that the position of the air supply and return,as well as the luggage rack and the table and chair,the airflow inside the train is formed different sizes'vortex in the vicinity of the luggage rack,the aisle area and the upper and lower seats,which causes the airflow speed at that location to change faster.At the same time,due to the heat dissipation and respiration of the passengers,the temperature near the seating area is higher than other areas,and the temperature gradient is large.The presence of the luggage rack also reduces the heat dissipation efficiency in the interior of the train.Because of obstacles in the aisle,the airflow speed is higher,the temperature is lower than the windows on both sides on the same level,and the air conditioning effect is better.The respiration of the passengers leads to a high CO₂ concentration near the respiratory zone and a low O₂ content.The CO₂ and O₂concentrations in the train are within the range required by the standard,so passengers have a lower probability of altitude sickness.?3?According to the simulation results and the range of specified by PMV,the air supply temperature and speed are dynamically adjusted for different stations.Through the comparison of energy saving efficiency,the optimal working conditions of the train running are proposed.The research results show that the adjusted air supply temperatures not only satisfy the indoor air quality and comfort requirements,but also reduce the amount of air heating.The energy saving effect is significant.Then,the air supply speed is adjusted.The reduction of air supply speed within the controllable range makes it possible to ensure that there is no blowing feeling in the train,can remove the residual heat effectively,satisfy the comfort of passengers and meet the requirements of CO₂ and O₂ concentration.At the same time,the energy saving rate is improved,thereby reducing air conditioning operating energy consumption?some sections can even reach 100%?,and achieving the goal of uniformity of comfort and energy saving.?4?The dynamic adjustment process of the train air conditioning automatic control system was explained.After the weather parameters of the train and the changes of the thermal environment inside the train are fed back to the air conditioning control system,the air supply parameters are adjusted to meet the air conditioning requirements.Considering the special oxygen supply link in the operation of the Qinghai-Tibet Railway,the automatic control method suitable for the CO₂ and O₂ concentration of the Qinghai-Tibet line train was proposed,which improved the original air conditioning operation mode of the train.