Study On The Influence Of Elevator Piston Motion On The Smoke Movement In Vertical Shafts Of High-rise Buildings

High-rise buildings are characterized by multi-storey,huge volume and large number of evacuees inside.Once a fire occurs,traditional staircase evacuation would be inefficient due to the rapid smoke spread and the long evacuation path,and its evacuation time would be unable to meet the relative requirements so that high-rise building fire can easily cause serious physical injury and economic loss.To solve this problem,scholars around the world began to think about the availability of fire elevators under fire conditions.The safety of elevator evacuation is closely related to equipment condition and smoke movement.Since elevator movement can disturb smoke movement in the shaft,this paper mainly studies and analyzes the smoke movement law in the elevator shaft under different simulation conditions.In this paper,Gambit is used to establish the model,divide the grid and set the boundary types,FLUENT is used to simulate and Dynamic mesh technology is used to simulate the elevator car movement.By changing elevator movement directions,elevator movement speed,fire source power and the ratio of car to shaft,different simulation conditions are settled.After classifying and comparing,the effects of different factors on the movement of smoke are obtained.Under the natural smoke exhaust condition,when the fire source is on the first floor,the elevator car fixed,upward and downward conditions are simulated.It is found that the elevator movement has obvious influence on the smoke movement in the shaft,and the effects of elevator upward and downward movement are opposite.Elevator upward movement is not conducive to the suppression of smoke spread,while the downward movement is conducive to the suppression of smoke spread.Thus,the three car movement speeds of 2.5 m/s,3.0 m/s,and 3.5 m/s were selected in each direction of elevator movement to study the influence of elevator speed on smoke movement.It was found that at the same time point and among these three speeds,the upward speed of 2.5m/s and downward speed of 3.5m/s show the slowest smoke movement.Under the natural smoke exhaust condition,when the fire source is on the first floor and the elevator is ascending,the conditions of fire source power 1MW,5MW and 10 MW aresimulated.It is found that the fire source power can directly affect the propagation and spread speed of smoke in the building.With the increase of fire source power,the height that the certain concentration smoke can reach in the shaft increases significantly.When the elevator movement stops,in the condition of 1MW fire source power,the smoke concentration in the entire shaft do not reach the limit value.In the condition of 5MW fire source power,smoke exceeding the certain concentration moves to the height between 7th floor and 8th floor.In the condition of 10 MW fire source power,smoke exceeding the certain concentration moves to the height between 16 th floor and 17 th floor.Under the natural exhaust smoke condition,when the fire source is on the first floor and the elevator is ascending,the ratios of car to shaft of 36.2%,49.8% and 51.2% are simulated.It is found that the increase of the ratio can accelerate the smoke movement,lead to significant pressure and velocity changes and neutral surface position descending.Therefore,within these three conditions,the ratio of car to shaft of 46.2% is more conducive to suppress the smoke spread.The determination of this parameter will provide a theoretical reference for elevator selection in practice,so as to ensure the safety of evacuation when fire elevators are used in fire conditions.