Effect of non-ideal opening behavior of diaphragm on the operation of free piston shock tunnels
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摘要: 在自由活塞激波风洞中，主膜片非理想打开行为可能对活塞运动和激波形成产生不同程度的影响。基于膜片的剪切-应变模型和活塞动力学模型，得到了膜片打开-活塞运动的耦合方程组，完成了膜片动态打开过程对活塞运动和常压力驱动时间影响的刻画。研究显示：由于活塞前脸压力和活塞速度之间存在博弈，膜片打开行为的差异性对活塞末端速度影响不大，活塞在压缩管末端可以实现"软着陆"。此结论得到试验证实。试验结果还显示：主膜片非理想打开行为对激波形成的影响较大，但是随着激波的传播，这种影响逐渐减弱。Abstract: In free piston shock tunnels, the non-ideal opening behavior of the main diaphragm may have different effects on the free piston motion and the shock wave formation. Based on the diaphragm shear-strain model and piston dynamic model, the coupled equations involving piston motion and diaphragm rupture are obtained for the first time, and the effects of the diaphragm opening process on piston motion and driving time under constant pressure are described. Research shows that, due to the interaction between the piston front pressure and the piston speed, the speed of diaphragm rupture or rupture ahead of time has little effect on the free piston terminal speed, and the piston can achieve soft landing at the end of the compression tube. This conclusion is confirmed by test results. Moreover, the test results also show that the non-ideal opening behavior of the main diaphragm has a distinct influence on the formation of the shock wave, and it gradually weakens during the propagation of the shock wave.
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Key words:
- free piston shock tunnel /
- main diaphragm /
- non-ideal opening behavior /
- free piston motion /
- shock wave
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图 2 膜片动态打开/瞬态打开情况下的活塞速度和驱动气体压力(λ=40)
Figure 2. Piston speed and pressure in two cases (λ=40)
图 3 膜片不同打开速度(或时间)下的活塞速度和驱动气体压力(λ=40)
Figure 3. Piston speed and pressure under different rupture of diaphragm (λ=40)
图 4 膜片正常/提前打开情况下的活塞速度和驱动气体压力(压缩比40、30)
Figure 4. Piston speed and driver gas pressure with different compression ratios
图 5 FD-21风洞重活塞速度历程及膜片打开情况
Figure 5. Velocity history of piston and diaphragms in FD-21
表 1 风洞试验初始条件及相关参数
Table 1. Initial conditions and related parameters of wind tunnel tests
pA, 0
/MPapHA, 0
/kPamHe:mAr Mp
/kgλ Umax
/(m·s-1)pHA, r
/MPa0.83 19 0.05:0.95 205 29 240 5.2 
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