Simulation optimization and test of fire extinguisher funnel based on CFD-DEM coupling method

The mechanic performance of ejecting pneumatic fire extinguisher is determined by the following parameters: air speed at funnel exit, outfire range and ejecting stability; and the second and third parameters depend on the fire extinguishing agent pellet's velocity on funnel exit and the amount of fire extinguishing agent pellets detained in the funnel when extinguisher is working. In this research, the CFD-DEM coupling model was adopted to simulate the working process of ejecting pneumatic fire extinguisher, and the type of 6MF-30 pneumatic extinguisher was used to test the reliability of the coupling model. The funnel throat angle X1, the adding position of fire extinguishing agent X2, and the funnel length X3 were selected as the influencing factors, and total 23 experiments were conducted by the simulation model under the quadratic orthogonal rotation design. The virtual tunnel was designed according to the tunnel equipped to 6MF-30 pneumatic extinguisher. The virtual fire extinguishing agent pellets were found on the EDEM interface, coupled to the original CFD by Lagrangian model. The pretest results showed that this model had strong convergence which was proved by its stable airflow performance when running at the time of 0.2-0.25 s, and stable pellet number when running at 0.34 s. The air velocity at exit calculated by the CFD-DEM coupling model was similar to the theoretical value. It could be found that the number of aggregating virtual pellets detained in the region between the air tunnel and the fire extinguishing agent's channel was consistent with the result of research by other scholars. The simulating experiment data were exported for analyzing. The average velocity in axial direction on each point at funnel exit was read by Fluent, and after subtracting the average value 197.550, the deviation data of the 23 experiments were got and selected as the outlet wind velocity (index Y1). The max virtual pellet velocities in axial direction monitored by EDEM within 0-0.4 s of all experiments were selected as the spouting velocity (index Y2). The vertical coordinates of every virtual pellet at 0.37, 0.38, 0.39, 0.4 s in all experiments were read by EDEM, and 'countif' function was used to calculate the number of virtual pellet located in the tunnel (as assessment index Y3) when working. After the significant test and the variance analysis, the regression equation building was done by using SAS9.1. The result showed that the fire extinguishing agent pellet's velocity on funnel exit and the amount of fire extinguishing agent pellets detained in the funnel were significantly correlated to the three factors (P ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.