MHD传感器敏感结构地面温度特性数值分析

Numerical Analysis of Temperature Sensitivity for Sensitive Mechanism in MHD Sensor on Ground

针对高精度MHD传感器温度稳定度的要求,采用稳态、频域有限元方法建立了导电流体、永磁回路、一级放大的物理模型,并且分析了地面测试温度对敏感结构输出特性的影响。当温度为-20~80℃或温差为2~10℃时,重力方向与角速率幅值对导电流体输出电压的影响较大,并且相对于室温输出电压的最大变化约占该电压值的50%。随着角速率幅值的减小,温度对导电流体输出电压的影响变得显著。这是由于自然对流抑制了磁性对流,从而影响导电流体内部的电势分布。外加磁场与一级放大对敏感结构输出特性的影响都较小,并且相对于相应室温数值的最大变化都小于该室温数值的1%。分析结果显示,影响MHD传感器敏感结构温度稳定度的主要因素在于液态金属磁流体动力学的温度效应。

For a more clear understanding of temperature drift in a high⁃precision MHD sensor,physical models of the sensitive mechanism,including conductive fluid,permanent magnetic loop and first⁃stage amplifier,are established.The influences of ambient temperatures on the output voltages of MHD sensor on ground are analysed by the stationary and frequent finite⁃element techniques.The directions of gravities and the magnitudes of angular rates bear on the effect of temperatures on the output voltages when the temperatures are-20~80℃,which are similar as the situations when temperature differences are 2~10℃.The maximal difference to the voltage at room temperature occupies about 50%of the value.The temperatures affect the output voltages more intensely whereas the magnitudes of angular rates fall.Natural convections suppress the magneto⁃convective flows and shift the distributions of electric potentials in the liquid metal,which may be the source of those phenomena.The applied magnetic field and the first⁃stage amplifier affect less on the output signal of sensitive mechanism,and the maximal differences to the values at room temperature occupy less than 1%of the values.It is concluded that the temperature sensitivity of liquid metal magnetohydrodynamics is a crucial factor relating to the stability of the sensitive mechanism in a MHD sensor on ground.