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A free-piston driver that employs entropy-raising shock processes with diaphragm rupture has been constructed, which promises
significant theoretical advantages over isentropic compression. Results from a range of conditions with helium and argon driver
gases are reported. Significant performance gains were achieved in some test cases. Heat losses are shown to have a strong
effect on driver processes. Measurements compare well with predictions from a quasi-one-dimensional numerical code.
Received 7 September 1996 / Accepted 5 October 1996 相似文献
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A free-piston shock tunnel (FPST) is one of the most useful ground testing facilities for hypervelocity flow research of re-entry vehicles and scramjet engines. For an efficient operation with tuned piston motion, the design of facility and the comprehension of the physical phenomena in a FPST, a numerical simulation which can properly predicts the flow with actual losses is required. But there are few successful numerical methods which can simulate its overall performance. In the present study, numerical method was developed by using the KRC shock capturing scheme and by modeling the flow losses in suitable forms for a quasi-1D numerical computation. The present numerical results were compared with the data obtained in two different facilities, T4 and T5. The applicability of the present numerical method as a design tool is discussed briefly.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society. 相似文献
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Preliminary results in the Marseille free-piston shock-tunnel facility are presented. The compression of the driver gas by the piston is studied experimentally for two different geometries of the end of the compression tube. Peak pressures obtained with the end of the compression tube closed, and with bursting of the diaphragm separating the high pressure from the low pressure chamber, are compared with calculated values in the cases of N2 and He as driver gases. A phenomenon of accoustic resonance has been uncovered, generating strong pressure oscillations which, if not properly dealt with, could impair the quality of the useful flow in such a facility.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society. 相似文献
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自由活塞斯特林制冷机间隙密封技术研究 总被引:2,自引:0,他引:2
间隙密封作为自由活塞斯特林制冷机中的一项关键技术,可以在完成密封作用的同时消除接触磨损和因此而产生的污染,同时由于间隙内气体的泄漏,引起了冷量损失,使制冷量减少。文中建立了层流工况下间隙密封的数学模型,推导了密封间隙的泄漏率。针对自由活塞斯特林制冷机的结构,对三处不同位置的间隙密封分别进行分析,提出了不同位置的间隙密封设计要求。对于直线压缩机的间隙密封,压缩机间隙密封的泄漏会带来压力波损失并同时影响压缩机固有频率;为消除压缩活塞的偏置,要求周期泄漏量为零,对于膨胀机的间隙密封,除了泄漏损失还包括了穿梭损失和摩擦损失等。最后,考虑实际加工和装配工艺的局限性,对间隙密封的偏心影响进行了分析,并对自由活塞斯特林制冷机间隙密封的安装技术和检测手段提出了简单的建议。 相似文献
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A two-stage free-piston driver 总被引:2,自引:0,他引:2
The overall cost of free-piston driven facilities can be substantially reduced if the contraction between the compression
and shock tubes is replaced with a constant area section. However, with such an implementation, a new driver concept is required
in order to achieve a realistic facility length. This paper describes a new free-piston driver type for expansion tubes which
satisfies the above criteria. The technique is known as the two-stage free-piston driver where the driver gas is compressed
in two distinct stages with a unique compound piston design. A new facility has been constructed (X-2) which is described
in some detail. A quasi-one-dimensional numerical model of the compression process is also developed which agrees well with
driver tube experimental results. This new driver is coupled to an expansion tube arrangement where super-orbital test flows
are generated. The results show that a two-stage free-piston driver is capable of driving hypervelocity expansion tubes and
therefore new facilities of increased size but reduced cost are now possible.
Received 18 May 1998 / Accepted 18 October 1998 相似文献
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