Experimental study on airflow in underground space of Metro system with a constant tracer gas injection technique.

A concept of mixing ratio of piston air is developed to evaluate the portion of the injecting air from tunnel mixed with the air in platform space of metro system. And a 3- dimensional turbulent model is used to simulate the airflow in metro platform resulted by the ventilation system and moving trains. Field measurement has been conducted to verify the 3-dimensional model. This experiment is performed during the normal operation time of a metro station with constant tracer-gas injection method. The results agree well with the numerical solution. The reason of the differences between experiment and simulation is discussed. It is concluded that the model is accurate enough for HV AC system design of metro line.