Numerical Simulation Of The Gas Solidtwo-phase Flow Of Powder Fire Engine

Fire is one of the main disasters which threatens the public safety and endangers people’s life and property. With the development of economy, the progress of science and technology and the large scale urbanization, the activities of industrial production and daily life have been the main causes of fire. There are lots of reasons that lead to the increasing of incidence, the depth of harmfulness and the raising degrees of the secondary disasters of the fire. Such as, The development of resources, heavy traffic, the application of the new material and new equipment, the mechanization and electrification, the concentration of the population, buildings, wealth and production and so on. Which are the same reasons that result in B, C and D class fire takes larger and larger proportion of the total occurrence of fire. However, the fire engines in our country are mainly made up by the pumping engines which can not extinguish the B, C and D class fire. So, powder fire engines will take more and more important place in the future. This paper is mainly about the numerical simulation of the powder fire engine based on CFD, short for Computational Fluid Dynamics, and getting the main parameters of the powder fire engine.In this paper, the basic theory of computational fluid dynamics is introduced, the calculation accuracy and the computer memory requirements of different turbulence models are compared, two different two-phase flow description method, Euler-Euler method and Euler-Lagrange method,are analyzed, the different forces between the particles and fluid are displayed. Considering the calculation accuracy and feasibility of numerical simulation model, realizable k-ε turbulence model is chosen as the turbulence model, Euler model is chosen as the the calculation model of two-phase flow, the drag force, collision force and friction force are chosen as the force between the particles and the fluid, ignoring other insignificant forces in this paper.The powder tank, the nitrogen cylinders and the spray region model are simplified without affecting the key features of the model. 3D mesh of dry powder tank is drawn by the ANSYS mesh software and the boundary conditions of mesh are also set in the ANSYS mesh. In order to reduce the amount of mesh,so as to reduce the time of computation, the 2D meshes of the powder tank, the nitrogen cylinders and the spray region are drawn by the ICEM CFD. The meshes of the geometric structure with large gradient flow parameters are refined, which effectively improves the calculation accuracy under the premise not to make too much calculation. The pneumatic pressure reducing valve is modeled by the PCD(Pneumatic Component Design) of the AMESim software. Time-dependent variation and distribution of the pressure and flow rate are calculated through the simulation of the pneumatic valve.The discharge process of the nitrogen cylinders, the discharge and filling process of the powder tank and the injection process in the spray region are simulated by FLUENT, the widely used commercial CFD software. Then, the results of the FLUENT are calculated by MATLAB to get the main parameters of powder fire engine, the inflation time, the effective injection time, the effective range, the remnant powder rate and effective mass flow rate of injection. The correctness of the numerical simulation is verified by the comparison of powder injection experimental data and numerical simulation data. Then, the powder fire engine parameters are checked whether to meet the requirements of the GB7956-1998 "performance requirements and test methods for fire fire engine". At last,the optimization methods are proposed if the parameters do not meet the requirements.