Abstract: In this paper, the behavior characteristics of jet fire in double slope building ceilings were studied through experiments and numerical simulations, and the effects of ceiling angle on the temperature distribution below the ceiling and plume flow entrainment behavior were analyzed by experiments and numerical simulation. The results show that the jet temperature gradually decreases from the impact point to the periphery under the horizontal ceiling condition. With the decrease of the ceiling angle, the variation trend of the jet temperature is as follows: with the increase of the distance from the impact point, both in the ridge and slope direction, the jet plume temperature presents the characteristics of first increasing and then decreasing, that is, the phenomenon of local low temperature area in the area of the plume impact point of the double-slope ceiling. Especially when the power of the fire source is large and the angle of the ceiling is small, the phenomenon of the low temperature zone is more obvious. In addition, the double-slope ceiling structure will restrict the flow of the plume along the slope direction, and the smaller the angle, the stronger the inhibition effect of the plume in the slope direction, resulting in more plume spread along the ridge direction. Numerical simulation is used to quantify the limiting effect of double-slope ceiling on air entrainment. It is found that the air entrainment per unit length under the ceiling decreases with the decrease of angle. The research in this paper is of guiding significance for the fire protection design of double-slope ceiling.

Key words: double-slope ceiling, ceiling plume jet, numerical simulation, low temperature area, plume flow entrainment