表面磁流体气动激励控制楔面激波规律数值研究

Numerical Research for Regularity of Wedge Shock Wave with Surface MHD Aerodynamic Actuation

关键词:  磁流体  激波  流动控制  表面放电  磁场

Key words:  Magnetohydrodynamic(MHD)  Shockwave  Flow control  Surface discharge  Magnetic field

摘要:

针对表面磁流体(MHD)气动激励对高超声速进气道在非设计状态下激波控制问题，从唯象学的角度出发，基于低磁雷诺数假设，将电磁作用简化为Navier-Stokes方程组中的源项处理，同时考虑到低气压、低磁场环境下电子回旋效应引起的Hall效应，并联立Ohm定律，建立磁流体动力学模型，通过与实验纹影对比验证了模型的合理性，并利用该模型研究了表面MHD加/减速激励作用位置与宽度、磁场强度、电导率和能量转化率等参数对楔面激波的影响规律。结果表明:表面MHD气动激励包括焦耳热与洛伦兹力作用，当放电功率密度为3.8×109kW/m3，磁场强度为0.34T时，MHD加/减速激励分别使激波位置前移6mm与10mm；而磁场强度较低时，由于焦耳热的主导作用，将会出现激波前后压力比增大，激波强度增加等负面效应；根据激励参数的影响规律，激励器电极应靠近尖端布置，增大磁场强度，并改善等离子体源以提高气体电导率，同时适当增大激励区域宽度。

Abstract:

The paper is devoted to the scientific problem of control of hypersonic inlet shockwave at off-design state based on surface MHD aerodynamic actuation. The MHD kinetics model is established by a combination of Navier-Stokes equations and Ohm’s law，and the electromagnetism interaction is simplified as the source terms of Navier-Stokes based on phenomenology and assumption of low magnetic Reynolds number，meanwhile，the Hall effect is taken into consideration which results from electron cyclotron effect in low pressure and magnetic field intensity. The reasonability of the model is verified in contrast with experiment shockwave schlieren image，and the regularity of location and width of actuation region，magnetic field intensity，conductivity，energy conversion efficiency of MHD effect on the wedge shockwave is investigated by the model. The results show that the surface MHD aerodynamic actuation includes Joule heat and Lorentz force effects，when discharge power density is 3.8×109kW/m3 and magnetic field intensity is 0.34T，the MHD acceleration/deceleration actuation can make the shockwave 6mm and 10mm ahead respectively. When magnetic field intensity is low，the front-back ratio of pressure and magnetic field intensity increased as the result of leading role of the Joule heat. According to the regularity of actuation parameters，the actuator should be arranged closed to tip of the wedge，magnetic field intensity should be enhanced，conductivity should be increased by improving the plasma source technology，and width of actuation region should be increased appropriately.