气动热环境下高速飞行器光学头罩特性分析

Characteristics analysis of high-speed aerocraft optical dome in aerodynamic heating environment

建立高速飞行器红外光学头罩在气动热环境下有限元分析模型,分析头罩在气动热环境下的物理特性和光学特性,对头罩在气动热环境下的温度场、应力场、应变场和位移场进行数值计算。计算结果表明头罩在气动热环境下温度场分布不均匀,因此头罩会产生热应力而发生形变。利用有限元分析结果,根据热光效应和弹光效应理论,对气动热环境下红外光学头罩的折射率场进行数值计算。以头罩外表面中心点折射率为例,在头罩工作时间内,通过计算得到头罩15 s后由热光效应造成的折射率改变为0.011,而由弹光效应造成的x方向折射率改变为0.000 107,即弹光效应造成的折射率改变量约为热光效应造成折射率改变量的0.97%,由此可知,在气动热环境下热光效应对头罩折射率的影响比较大,而弹光效应对头罩折射率的影响比较小。

A finite element model of the high-speed aerocraft infrared optical dome in the aerodynamic heating environment was established to analyze the dome＇s physical and optical properties. The temperature filed, stress field, strain field and displacement field of the dome in the aerodynamic heating environment were computed numerically. The calculated results show that the temperature distribution of the dome in aerodynamic heating environment is nonuniform and thus the dome is deformable due to its thermal stress. Based on the theories of thermo-optical effect and elastic-optical effect, the refractive index field of the dome was numerically computed with the result of the finite element analysis. Taking the refractive index of the central point in the dome＇s outer surface as an example, the refractive index variation caused by thermo-optical effect is 0. 011 while the x-direction refractive index variation caused by elastic-optical effect is 0. 000 107. That is, the refractive index variation caused by elasticoptical effect is only 0.97% in the amount of the refractive index variation caused the thermooptical effect during the dome＇s working time. Therefore, thermo-optical effect has greater influence on the refractive index variation of the dome than elastic-optical effect.