【作者】 侯宇；

【导师】 陈清华；

【作者基本信息】 重庆大学 ， 动力机械及工程， 2003， 硕士

【摘要】 本课题针对传统涂层材料沉积技术的缺点，提出利用冷气体动力喷涂技术来提高涂层沉积效率和涂层性能。本文的主要内容是对拉伐尔喷管内超音速气固两相流动过程进行数值模拟，并对喷管内的热力过程进行分析，以找出各种参数对喷管出口气流速度的影响。冷喷涂技术作为一项80年代才出现的材料表面处理技术，在很多方面显示了其它涂层沉积技术所不具备的优势，其主要优点是工作温度相对较低，粉末沉积效率高、速度快，涂层强度高，喷涂成本低。这样，冷喷涂技术就在很多领域有了良好的适用性。在制造加工业中，冷喷涂技术适合进行各种表面处理，如：防腐涂层、耐磨涂层、高强度和高硬度表面、导磁表面、导热表面等，还可以在金属或非金属表面喷涂电导涂层、绝缘涂层，甚至可以进行金属间喷涂与修复。此外，在燃料电池动力系统中，冷喷涂技术也有良好应用前景。目前，燃料电池技术日益受到关注，对其商业化的要求也越来越急迫，但由于成本和小型化方面的技术限制,制约了燃料电池推广进程。在燃料重整器中，由于以传统的重整方法对重整器进行小型化有很大困难，结合板型重整器的优点，我们提出在热、质传输上有更高效率的微通道板型重整器，而实现此方案的关键就是怎样形成微通道表面的催化涂层。我们将冷喷涂技术引入方案中就是利用冷喷涂在相对低温下，对材料性能影响小的特点来制备高效催化涂层。此外，对于燃料电池双极板而言，使用传统材料，在重量、强度、成本各方面都有很大局限，而利用冷喷涂技术可以兼顾这三个方面的要求。冷喷涂技术的关键是通过合适的拉伐尔喷管加速气流到超音速，以带动喷涂材料粉末速度的提高，使其有效沉积在载体表面。对于不同的气体进口参数，对出口气流速度的影响是不同的。进口速度的变化对出口速度的影响比较小，尤其是进口速度低于50m/s时，其变化基本上不会使出口速度有大的改变；进口压力的变化会对出口速度产生一定的影响，但是由于让进口气流压力有很大的提高不太现实，提高出口速度的方式是以提高进口气体温度为主，适当提高进口压力。为了对喷管内气体流动过程有更深入的了解，我们应用重整化群（RNG）k-ε模型对流动过程进行数值模拟，针对喷管流道形状的变化，采用不均匀网格划分计算区域，并用二阶上风差分格式离散通用微分方程的对流相；最后采用SIMPLE算法来求解气体的运动。在得出的结果中，比较了不同气体和粒子速度的变化；并对压力、温度、速度的分布做了分析。在直管段和渐扩段的连接处，由于流动有一个小的角度偏转，会产生锥形弱激波，使气流的速度产生波动，压力、温度也会随之产生波动，在<WP=4>直管段后部，激波逐渐消失，流动恢复平稳。本文的最后还进行了下一步实验工作的系统和装置的设计。更多还原

【Abstract】 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 the<WP=6>character 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.更多还原