激光能量沉积降低钝头体驻点压力机制分析

Investigation of Stagnation Pressure Reduction of Blunt Body by Laser Energy Deposition

关键词:  激光能量沉积  流动控制  纹影  高超声速  透镜效应 

Key words:  Laser energy deposition  Flow control  Schlieren  Hypersonic  Lens effect

摘要:

针对高超声速飞行器表面驻点压力较高的问题,在马赫数5的来流条件下,分别采用单脉冲和高重频激光能量注入的方式控制弓形激波。将数值模拟结果与高时空分辨率纹影照片以及驻点压力测量结果相对比,分析了单脉冲激光能量与高超声速流场弓形激波的相互作用过程,结果表明透镜效应是激光能量沉积降低钝头体驻点压力的原因。单脉冲激光能量产生的低压区不能维持,降低驻点压力效率低,因此高重频是更有效的激光能量注入方式。优化了频率为80kHz、功率为自由流焓流6.6%的激光能量沉积位置,计算结果表明当沉积位置与钝头体表面的距离等于钝头体直径的1.5倍时,驻点压力降低了40%。在优化位置提高沉积能量大小至36.9%,可将驻点压力和热流分别降低83.3%和56.9%。 

Abstract:

To reduce the peak pressure of blunt body in hypersonic flow field, single and high rated laser energy were deposited respectively to control the bow shock in Mach 5flow. The simulated results are compared with high resolved schlieren images and pressure measurements to analyze the interaction of single pulsed laser energy and shock wave. The results indicate that the lens effect is the cause of stagnation pressure reduction of blunt body by laser energy deposition. The duration of low pressure region caused by single pulsed laser energy is too short, causing the low efficiency of the stagnation pressure reduction. High rated laser energy deposition is a more effective method. Deposition position is optimized at the laser frequency of 80kHz with the power of 6.6% of the enthalpy flux. The calculation results show that when the distance of deposition point and blunt body equals to 1.5times of the blunt body diameter, pressure of the stagnation point is reduced by 40%. By increasing laser energy magnitude to 36.9%,stagnation pressure and heat flux can be reduced by 83.3% and 56.9%, respectively. 