高超声速磁流体流动控制数值模拟研究

Numerical Investigation of Magnetohydrodynamics Flow Control

飞行器以高超声速状态飞行时,高马赫数来流经过激波后,温度陡升,气体分子的内能模态在高温下会受到激发,发生离解、电离、中性交换等反应,形成具有一定导电率的弱电离等离子体。合理地布置磁场与电场,激波层内的导电流体与外加电磁场相互作用产生感应电流,进一步产生洛伦兹力与焦耳热,可以实现对于飞行器气动力热的影响,达到流动控制的目的。本文针对磁流体热防护、磁流体能量提取两种流动控制手段进行了数值模拟研究。首先研究了来流马赫数、飞行高度对于磁流体热防护效果的影响规律,得到了如下规律:磁流体热防护技术可以使飞行器驻点热流降低20%,在一定飞行高度下,来流马赫数需要使来流总温接近10000K才能使磁流体热防护效果明显;磁流体热防护效果随飞行高度增加而增强。随后针对磁流体能量提取装置进行了概念设计与参数影响研究,并且得到如下结论:在典型再入飞行状态(高度46km、速度7000m/s)下,本文给出的磁流体能量提取装置可以在外加强度为0.2T的磁场强度下,提供兆瓦级的电功率输出,并且装置提取的电能与能量提取装置的工作效率均随负载电压的增加呈现先增加后减小的趋势,表明对于给定的来流条件,存在最佳的负载电压,使得磁流体能量提取装置的功率与效率达到最大。本文研究结果可以为磁流体热防护技术与能量提取技术在高超声速飞行中的设计提供指导。

When the aircraft flies at hypersonic speed,the high Mach number incoming flow passes through the shock wave and the temperature rises sharply.The internal energy mode of gas molecules is excited at high temperatures,leading to reactions such as dissociation,ionization,and neutral exchange,forming weakly ionized plasma with a certain conductivity.Reasonably arranging the magnetic field and electric field,the conductive fluid in the shock layer interacts with the external electromagnetic field to generate induced current,further generating Lorentz force and Joule heat,achieving the impact on the aerodynamic heat of the aircraft and achieving the purpose of flow control.This paper conducts numerical simulation research on two flow control methods:MHD heat flux mitigation and MHD energy extraction.Firstly,this paper investigates the influence of incoming Mach number,flight altitude,and magnetic field intensity on MHD heat flux mitigation.And the following conclusion has been obtained:at a certain flight altitude,the Mach number of the incoming flow needs to make the total temperature of the incoming flow close to 1000oK in order to make the MHD heat flux mitigation effect significant.Subsequently,this paper conducted conceptual design and parameter impact research on the MHD energy extraction device.And the following conclusion is obtained:under typical re-entry flight conditions(altitude of 46km,speed of 7000m/s),the MHD energy extraction device proposed in this paper can provide megawatt level electrical power output under an external magnetic field intensity of o.2T.The electrical energy extracted by the device and the working efficiency of the energy extraction device show a trend of increasing first and then decreasing with the increase of load voltage,indicating that for the given inflow conditions,there is an optimal load voltage that maximizes the power and efficiency of the magnetic fluid energy extraction device.The results in this paper can provide guidance for the design of magnetohydrodynamic thermal protection technology andenergy extraction technology in hypersonic flight.