SUPPRESSION OF SHOCK/COMPRESSION WAVES IN SUPERSONIC CONFINED FLOW

本研究的目的是抑制激波和压缩波在受限超音速流动中。为了抑制这些波，提出了在超声速流动中施加电磁力的方法。在前人对激波的研究中，主要研究了激波的空间结构和时间特性。然而，他们并没有被镇压。本文提出了在超声速流动中施加洛伦兹力可以抑制激波的新概念，并利用MHD通道进行了实验研究。为了获得足够的电流导电性，用掺有铯的氩气作为工作气体。通过施加磁场对流动施加洛伦兹力，并通过电极之间的负载电阻控制超音速流动中的电流。首次发现激波的位置可以由较大的洛伦兹力控制，在最佳的洛伦兹力下，激波在MHD通道内消失。此外，发现激波的强度和位置随滞止气体压力的变化而变化。当实现电流的均匀分布时，冲击波的强度降低。在本研究中，也通过改变位于MHD通道上游区域的喷嘴的洛伦兹力来控制MHD通道内的激波。研究发现，随着喷嘴内洛伦兹力的增大，MHD通道内激波向上游移动，激波强度减小。同时研究了洛伦兹力作用下的压力损失。结果表明，压力损失主要是由等离子体产生引起的，由于洛伦兹力显著降低了流动的入射马赫数，激波造成的损失很小。这些实验结果表明，利用洛伦兹力抑制超声速流动中的激波是可行的，从工程角度来看是一种很有吸引力的方法。同时，通过本文的研究，获得了磁流体力学的新知识。少

An objective of the present research is to suppress shock waves and compression waves in a confined supersonic flow. In order to suppress these waves, an apply of electro-magnetic forces on the supersonic flow was proposed. In previous studies on shock waves done by many researchers, spatial structures and time behavior of shock waves were investigated. However, the suppression of them was not made. The present authors have proposed a new concept that shock waves may be suppressed by applying Lorentz forces on the supersonic flow, and experimental studies to confirm this concept were made using MHD channel. In order to obtain a sufficient electrical conductivity of the flow, argon seeded with cesium was used as a working gas. Lorentz forces were applied on the flow by applying a magnetic field, and electrical currents in the supersonic flow were controlled by load resistance between electrodes. It was found for the first time that the position of shock waves can be controlled by the ma … More gnitude of Lorentzforces and at the optimum Lorentz forces, the shock waves disappear within the MHD channel. Furthermore, the strength and the position of the shock waves were found to change with stagnation gas pressures. When the uniform distribution of the current was realized, the strength of the shock waves was decreased. In the present research, the controll of the shock wave in the MHD channel was also made by changing Lorentz forces in the nozzle which was located at the region upstream of the MHD channel. It was found that with an increase of the Lorentz forces in the nozzle, the shock waves in the MHD channel moved upstream and the strength of the shock waves was reduced. The pressure losses due to the apply of the Lorentz forces were also investigated. The results have shown that the pressure losses are induced mainly by a production of plasma and the loss due to the shock waves is small because an incident Mach number of the flow is reduced remarkably by Lorentz forces. These experimental results have suggested that the suppression of the shock waves in the supersonic flow by Lorentz force is possible and it is very attractive method from the engineering points of view. At the same time, the new knowledge of the magneto-hydrodynamics was obtained by the present research. Less