| During the long-term operation of subway,a large amount of waste heat will be discharged into the subway tunnel,and the air temperature inside the tunnel will continue to rise and the thermal environment will gradually deteriorate,which will affect the normal operation of trains.Therefore,for new subways and subways with short operation time,it is of great significance to make a good prediction of air temperature rise in subway tunnels and develop a reasonable subway tunnel ventilation mode to ensure the safe operation of trains.This paper takes a metro tunnel at a station of Lanzhou Metro Line 1 as the research object and uses theoretical calculation combined with numerical simulation to study the change characteristics of air temperature in Lanzhou metro tunnel under the joint action of soil heat storage and ventilation mode,analyze the factors affecting the change of air temperature in the metro tunnel,and develop a reasonable ventilation operation plan in the tunnel.This paper adopts theoretical calculation combined with numerical simulation calculation method to carry out the research,using theoretical calculation and analysis to determine the heat production and characteristics in the metro tunnel,and at the same time,establish the temperature prediction equation under the heat storage and ventilation mode of the metro tunnel,and make the prediction of air temperature in the early,near and long term of Lanzhou metro tunnel operation;taking a typical station of Guangzhou metro line 2 as the research object,the numerical simulation calculation method was carried out to A typical station of Guangzhou Metro Line 2 was used as the research object to verify the numerical simulation calculation method;a series of simulation calculations were conducted using a station of Lanzhou Metro Line 1 as the research object,and outdoor temperature,travel speed,travel log and ventilation conditions in the tunnel were selected as the main influencing factors;the analysis of the calculation results proposed the ventilation mode for the initial,near-term and long-term periods of Lanzhou Metro tunnel,and the following conclusions were drawn:(1)The heat generation in the subway tunnel consists of heat generation in the train and heat generation in the tunnel.In summer,the heat generation in the tunnel is dominated by the heat generated by the condenser,and in winter,the heat dissipated by the human body is dominated if the air-conditioning equipment is not turned on in the tunnel,and because of the high outdoor temperature in summer,the study on the air temperature rise in the underpass tunnel in this study is dominated by the summer conditions.The analysis of the heat generation data in the tunnel in summer shows that the main heat generation is concentrated in the time when the trains stop at the station,which ranges from 500 m to 640 m of the effective platform,and the proportion of its heat generation reaches 52.19%.(2)It is predicted that the air temperature in the tunnel of Lanzhou Metro will rise to18.14℃ at the early stage of operation,with an annual average temperature rise of1.05℃/year;the air temperature in the tunnel will rise to 19.87℃ in the near future of operation,with an annual average temperature rise of 0.49℃/year;the air temperature in the tunnel will rise to 20.29℃ in the long term of operation,with an annual average temperature rise of 0.21℃/year.The rate of air temperature increase in the tunnel is the fastest in the early period of Lanzhou Metro operation,and the rate of air temperature increase in the tunnel is stable in the long term of Metro operation.(3)Considering the condition of setting single piston air shaft,this study lists the outdoor temperature,train speed,train pairs and tunnel ventilation conditions as the main influencing factors causing the air temperature rise in the tunnel,and the simulation results show that the air temperature in the tunnel is positively related to these four factors,i.e.,with the increase of outdoor temperature,train speed,and train pairs,the air temperature in the tunnel increases,and the range of air temperature in the tunnel is 520m～732m;because the condenser is set on top of the train,the effect of hot air discharge at the top of the rail is better than the effect of hot air discharge at the bottom of the rail.(4)The analysis of the series simulation results shows that the residual heat of the air in the subway tunnel migrates with the train operation,from the place of maximum heat production(500m～640m)to the rear of the station tunnel,and finally concentrates at the piston air shaft,and the migration distance is about 40 m.(5)According to the simulation calculation results,the number of natural ventilation changes in the subway tunnel meets the subway design specification requirement of 3 times/h.Therefore,the tunnel ventilation mode of Lanzhou subway can be used for ventilation and cooling in the early,near and long term of operation,i.e.making full use of the train piston wind for ventilation and air exchange to achieve energy-saving operation under the premise of ensuring the safety and reliability of subway trains.(6)Lanzhou subway operation in the long term,in addition to the full use of train piston wind ventilation cooling,in order to prevent problems before they occur,but also in the morning and evening peak period auxiliary rail top and rail bottom exhaust hot air system in a timely manner to the train heat production in situ emissions. |
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