横截面形状对超声速磁流体发生器性能的影响

通过三维数值模拟研究了不同横截面形状的磁流体(MHD)发生器的热、电磁流动特性,发生器入口采用超声速来流条件,旨在应用于磁流体旁路超燃冲压发动机推进系统。数值模拟采用低磁雷诺数下磁流体五方程模型,通过熵条件格式和超松弛迭代(SOR)法联合算法分别求解Navier-Stokes方程组和电势方程。研究表明在电极壁面上电场、电流以及洛伦兹力等电磁场参数呈周期性变化,由于电极端点效应,电磁场参数在电极端点出现周期性的极值,而在管道中心电极端点效应对电流影响并不大,沿着流向电流保持连续变化。对不同管道横截面形状的发生器的数值模拟表明:由于涡电流和二次流效应的影响,形状参数较小的发生器焦耳热较为严重,二次流较弱;而形状参数较大的发生器焦耳热较小,二次流增强。因此,当形状参数α=0.8时可获得较好的焓提取率和电效率。

Influence of cross-sectional shape on the performance of supersonic magnetohydrodynamic generator

Three-dimensional numerical simulations were performed to study the thermal and electromagnetic fluid characteristics of supersonic magnetohydrodynamic (MHD) generator under the influence of inlet cross-sectional shape, which tends to be applied to improv the performance of propulsion system of scramjet. A joint numerical procedure, composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations and an successioe over relaxation (SOR) method for solving the elliptic equation governing the electrical potential, was used in this paper. Numerical results indicate that the electromagnetic parameters, such as electric field, electric current density and Lorentz force etc., vary periodically along the electrode wall. The extreme values of the electromagnetic parameters are located at the edges of the electrodes. Due to the influence of width between the electrode pair, the subsequent current eddies and secondary flow on the cross-section substantially affect the performance of MHD generator. In case of small cross-sectional shape parameter, severe Joule heating and weak secondary flow are induced in the MHD generator, and vice versa in case of high shape parameter. Consequently, when the cross-sectional shape parameter α is 0.8, the enthalpy extraction ratio and electric efficiency of MHD generator are considerable.