The Numerical Simulating Of The Supersonic Gas-particle Two Phase Flow In De-Laval-Nozzle

Aiming at the shortcoming of traditional coating material depositing technology,the Cold Gas Dynamic Spraying (CGDS) technology is used to improve the efficiency of particles depositing and performance of coating。This paper is mainly to find out the relationship between the parameters of inlet gas and gas velocity at outlet through numerical simulating of the supersonic gas-particle two phase flow in De-Laval-Nozzle and analysis of the thermal process of in the nozzle.As a kind of surface treatment technology coming forth in 1980s, CGDS shows its particular advantage of comparatively lower temperature,higher efficiency of particles depositing,higher speed,higher strengh of coating and lower cost in many aspects。Thus the CGDS has the better serviceability in many fields.In manufacturing industry, CGDS is fit to all kinds of surface treatment,such as corrosion resistant coatings, wear-resistant coating ,high hardness and density coating, high thermal conductivities coating, Corrosion coatings , depositing electrical conductivities coating on the face of metal or nonmetal material,etc,and even Intermetallic coatings and repair. Besides, CGDS also has the better application prospect in the Fuel Cell power system. At present, Fuel Cell technology has been paid much more attention, and it was also urgently required commercially, whereas, because of the difficulty of miniaturization and decreasing cost, it's technology has been hardly popularized. Due to the difficult of reformer miniaturization by using traditional reforming technology,combining the advantage of plate-type reformer,microchannel plate-type reformer which has higher efficiency in heat and mass transport is brought forward.The key to carrying out this project is how to form the catalyst coating on the surface of microchannel。Hence, the CGDS that hardly change the performance of catalyst for the relative low temperature is applied. Furthermore, As fuel cell bipolar plate concerned, it's profitable using CGDS rather than using traditional technology in weight, intensity and cost.The key of CGDS is an appropriate laval nozzle in that the gas is accelerated to be supersonic and drive the catalyst particles to deposit on the surface of substrate. The different parameter of inlet gas affected outlet velocity differently. The inlet velocity (<50m/s) can hardly improve the outlet velocity, whereas the inlet pressure can influence the outlet velocity to some extent, and the inlet temperature is the most important factor affecting the outlet velocity.A RNG k-εmodel was used in the numerical simulation in order to understand thecharacter of the flows in laval nozzle. A structured non-uniform grid system has been used to discretize the computation domain. The second-order upwinding scheme was selected for the discretization of the convection term in the governing equations, and the SIMPLE method is used to solve the continuous phase flow field.This paper compared velocity and temperature of gas or different particles, then analyzed the distributing of pressure, temperature and velocity as well as the generation of cone-shape weak shocks, which results in the velocity fluctuating.At last, this paper brought forward the design of experiment equipments and system.