基于离散元的粉末燃料输送弯管两相流特性研究

Tow-Phase Flow in Bending Pipe of a Powder Fuel Conveying System Based on Discrete Element Method

关键词:  粉末输送  弯管  气固两相流  颗粒碰撞  铝粉  压力损失

Key words:  Powder conveying  Bending pipe  Gas-solid two-phase flow  Particle collision  Aluminum powder  Pressure loss

摘要:

弯管是粉末燃料冲压发动机燃料输送系统的重要组成部分，为了研究弯管内气固两相流的流场结构、颗粒碰撞以及压力损失的变化规律，基于连续相-离散元（CFD-DEM）耦合模型，考虑颗粒的碰撞受力和弹塑性形变，对铝粉在弯管内的流动状况进行数值仿真。研究结果表明：CFD-DEM算法相对于传统的双流体模型和轨道法，能更为准确地描述颗粒流的碰撞信息和两相流的流动状况。弯管内的总压损失随流化气流量的增加，呈先减小再增大的趋势，在本文研究的条件下，优选的流化气流量为6~7g/s（流化气速度为3.0~3.5m/s）；在低流速下，颗粒间的碰撞次数远大于颗粒-壁面间的碰撞，随着流速的增高，颗粒与外侧壁面间的碰撞次数迅速增高，并导致颗粒-壁面间的碰撞次数超过颗粒间的碰撞。弯管的弯径越大，弯管内的总压损失越大，但颗粒-颗粒、颗粒-壁面的碰撞次数均下降。

Abstract:

The bending pipe is an important part of the fuel delivery system of powder fuel ramjet. In order to study the flow field structure， collision effect and the variation rules of total pressure loss for gas-solid two-phase flow in bending pipe， with the collision force and elastoplastic deformation of particles were considered， the numerical simulation was carried out to investigate the flow status of aluminum powder in bending pipe by the CFD-DEM coupling method. The results show that， compared with the traditional two-fluid model and orbit method， the CFD-DEM algorithm can more accurately describe the collision information of particle flow and the change of two-phase flow field. With the increase of fluidizing gas flow rate， the trend of total pressure loss in the bending pipe decreases first and then increases. Under the conditions studied in this paper， the best mass flow rate of fluidizing gas is 6~7g/s（fluidizing gas velocity is 3.0~3.5m/s）. Under the low flow rate， the particle-particle collisions are much larger than particles-wall. With the increases of fluidizing gas velocity， particle-outer wall collisions increase rapidly， which causes that the particle-wall collisions exceed particle-particle collisions. It also shows that the larger the bending radius is， the greater the total pressure loss in the bending pipe is， but the collision numbers of particle-particle and particle-wall are reduced.