Numerical Analysis of Smoke Temperature Characteristics below the Fire Ceiling in Main Transformer Room of Urban Rail Transit Substation

Abstract

Objective With the increasing power supply load required by metro, the operation of oil-immersed equipment such as wet-type transformers under overload conditions is extremely prone to fire, posing a threat to the safety of ceiling structure. To avoid or reduce the possibility of transformer fires, it is necessary to investigate the smoke movement patterns and the variation characteristics of ceiling temperature in main transformer room during fire. Method Taking the 110 kV Qichuan Substation of Jinan Rail Transit Line 3 as example, through theoretical analysis and numerical simulation, considering the comprehensive effects of ventilation conditions, fire heat release rate, and fire source height, the temperature characteristics of smoke below the ceiling in main transformer room during fire are investigated. Result & Conclusion When mechanical ventilation is activated, the organization of indoor airflow will affect the distribution of smoke temperature below the ceiling. Wind replenishment causes the fire plume to deflect, leading to the maximum temperature rise point shifting towards exhaust vents, with the maximum temperature rise slightly lower than when mechanical ventilation is closed. The dimensionless maximum ceiling temperature rise can be divided into two regions: when the flame does not impinge on the ceiling, it exhibits a linear relationship between the dimensionless maximum temperature rise and the ratio of Q2/5 and (hef-h0) (where Q is the fire heat release rate, hef is the distance from fire source surface to the ceiling, h0 is the virtual point source height); when the fire flame impinges on the ceiling, the dimensionless maximum temperature rise is a constant, and a prediction model for the dimensionless maximum temperature rise of the ceiling is proposed. Based on simulation data, prediction models for temperature decrease of ceiling jets driven by weak and strong fire plumes are proposed.

Keywords

• urban rail transit
• substation
• ceiling smoke temperature