分段法拉第磁流体发电通道流动特性数值模拟

Numerical Simulation of Segmented Faraday MHD Power Generation Channel Flow Field Characteristics

关键词:  冲压发动机  磁流体  发电通道  流场特性  数值模拟

Key words:  Ramjet engine  MHD  Power generation channel  Flow field characteristics  Numerical simulation

摘要:

磁流体发电是解决以冲压发动机为动力的飞行器机载供电问题的有效途径。为了探究磁流体发电通道的内部流动情况和能量转化机理，针对分段法拉第型发电通道，结合实验设备设计参数，构建了低磁雷诺数条件下的磁流体五波模型，并运用二阶熵格式对其求解。通过分析四种不同情况，研究了分段法拉第型磁流体发电通道在不同实验条件下的流动特性。计算结果表明:磁作用数由0变为0.1时，通道出口处温度升高10.4％，出口速度降低27.7％，马赫数降低25％，磁作用数升高至1时，出口速度将降至临界声速，马赫数降为1，出口温度较基准态升高20.8％；通道能量转化率越高，通道内壁逆压梯度越大，流动在内壁上容易发生分离；负载系数为0.5时，通道出口速度相较于负载系数为0.8的情况，气流速度下降约11.7％，马赫数下降8％，通道将产生更多的焦耳热，能量转化率较高，但是电效率较低。通道在进行发电实验时，增大电磁作用强度，同时选择合适的外部负载，可以提高通道发电性能。

Abstract:

MHD power generation is an efficient way to solve the onboard power supplying problem of aircraft using ramjet engine. In order to study the inner flow field characteristics and energy conversion mechanism，focus on segmented Faraday MHD channel，integrate with experimental system`s design parameter，MHD five wave model in low magnetic Reynolds condition was established and second order entropy scheme was used to calculate it. By analyzing 4 different cases，the flow characteristics of segmented Faraday MHD channel under different experiment conditions were studied. The calculation results show that as the magnetic interaction parameter evolves from 0 to 0.1，MHD channel’s exit temperature rises by 10.4％ whereas the exit velocity decreases by 27.7％，Mach number decreases by 25％，when magnetic interaction parameter increases to 1，exit temperature increases by 20.8％. Energy conversion ratio becomes higher as well as the adverse pressure gradient on the inner wall of the channel，which will lead to a flow separation. When the load coefficient is 0.5，there is a bigger decrease in exit velocity，which reaches 11.7％ and Mach number decreases by 8％ comparing to that the load coefficient is 0.8. MHD channel will produce more joule heat，shows a higher energy conversion ratio but lower electrical efficiency. When MHD power generation experiment is implemented，increasing the magnetic interaction strength and choosing appropriate external load can improve the power generation performance of MHD channel.