Abstract: In this study, a large-scale pumped-storage power plant underground powerhouse was used as the research object. A full-scale fire test under natural ventilation conditions was carried out, and the overall temperature distribution was measured through distributed temperature measuring cables. According to the measured data, the law of flue gas temperature change over time, the highest temperature distribution in the upper and lower spaces, and the flue gas stratification are obtained. The test results show that the temperature rise of the upper smoke layer relative to the environment in the fire section is 1.7, 2.3 and 3.8 ℃ respectively under 4, 6 and 10 fuel pans to simulate fire conditions. The temperature 3.5 m above the ground in the lower space of the plant is 7.6, 10.8 and 13.0 ℃ respectively. Due to the continuous heat loss to the surrounding environment, the highest temperature in the smoke layer attenuates along with the longitudinal spread of the smoke, and the attenuation trend is slowed down or reversed in front of the end wall due to the enhanced accumulation of smoke and heat. The smoke stratification in large underground powerhouses is obvious, and the interface between the flue gas layer and the fresh air drops between 20~30 m.

Key words: full scale, fire test, smoke spread, large pumped storage power station