Surrogate modelling of the high-static-pressure fan for high-speed trains and its dynamic airtightness analysis using CFD

Abstract

Pressure protection devices are installed in ventilation systems to coordinate the air quality and pressure fluctuations inside high-speed trains, wherein the active pressure protection device (APPD) that adopts high-static pressure fans (HSPFs) is superior in maintaining favourable air quality. However, it is complicated to model an actual channel of an HSPF, and its airtightness performance, which could cause ear discomfort for occupants, has been unclear until now. In this study, a surrogate model based on a porous medium is presented to simulate HSPF operations. This model is validated by reference values and field experiments, which can accurately represent its inhibition effect on pressure transmission inside and outside the vehicle. Based on the proposed model, the exterior pressure fluctuation parameters, mode of fan operation and fan performance curve were selected to analyse the dynamic sealing capability of the HSPF. The results showed that the mode of HSPF_on can effectively restrain the pressure transmission compared to the normal fan and the mode of HSPF_off, whose dynamic airtightness index (τdyn) is scarcely affected by the external pressure fluctuation, with a value between 20 s and 23 s. In addition, improving the fan performance can enhance the dynamic airtightness of the HSPF, and τdyn increases by approximately 3.5 s with the static pressure value rising by 1000 Pa. Moreover, a new method for investigating the dynamic airtightness of HSPFs is provided in this study, and this method can be used to guide the airtightness design of APPDs relying on HSPFs.