Analysis of Finite Amplitude Wave Motion in Acoustic Compressor using a Duct with Varying Cross-Section.

首先，描述了数值分析的结果。对于正弦振动活塞驱动的声压机，采用时间二阶精度、空间四阶精度的显式Mac-Cormack方法进行数值分析，并在截面积缩比为1~100范围内进行了详细分析。特别是，在分析中新设置了基于气门工况的边界条件，考虑了声压机在排气和进气过程中的实际运行。在壁面摩擦项中，不仅考虑了基于瞬时流速的定常项，而且考虑了非定常摩擦项。从分析结果看，澄清了以下事实。虽然管子封闭端的压缩比随着截面缩短率的增加而增加，但在截面缩减率…下当活塞比大于16时，出现了传播激波，并抑制了压缩比随活塞振幅的增加而增加的速度。在较宽的活塞振幅范围内，随着截面缩比的增大和压缩比的增大，均可获得无激振共振。但在50以上时，截面缩短率的影响不明显。在数值分析中引入了基于阀门实际运动的边界条件，出现了波动失稳现象。结果表明，边界条件有待进一步改进。其次，给出了实验验证结果。在本实验中，使用了截面积指数减小的轴对称声管(截面积缩小率为100)和等截面积的声管。在谐振点附近用电磁加速器驱动的活塞激励管内的气柱。并对其波动进行了测量。通过提高整个系统的刚性，尝试提高测量精度。此外，通过引入高精度的位移计，提高了活塞位移测量的精度。结果表明，等截面管内压力脉动的幅值和闭口处的波形与计算结果非常吻合。然而，对于截面压下率较大的情况，实验结果与计算结果并不吻合，这说明在截面压下率较大的情况下，数值分析还有待改进。较少

First, the results of numerical analysis are described. On finite amplitude wave motion of the air column in a closed tube with cross sectional area contraction for the acoustic compressor which is driven by a piston oscillating sinusoidally, the numerical analysis based on explicit Mac-Cormack method with second order accuracy in time and fourth order accuracy in space was applied, and the detailed analysis within cross section reduction ratio 1 - 100 was carried out. Especially, boundary condition based on valve operating condition considering the acoustic compressor real operation in exhaust and intake processes was newly set in this analysis. And also in the wall friction term, not only steady term based on the instantaneous flow velocity but unsteady friction term was considered. From the analytical result, following fact clarified. Though the compression ratio at the closed end of the tube increases with the increase in the cross section reduction ratio, under cross section reduc … More tion ratio of 16, the propagating shock wave is appeared, and it suppresses the increasing rate in compression ratio with increase of the piston amplitude. The shockless resonance is obtained in the wide range of the piston amplitude, when the cross section reduction ratio increases, and the compression ratio also increases. But the effect of the cross section reduction ratio is not remarkable over 50. In the numerical analysis introduced boundary condition based on actual motion of valves, the instability of wave phenomenon appeared. It shows that improvement of further boundary condition is required.Next, the experimental verification result is described. In this experiment, an axisymmetric acoustic tube (cross section reduction ratio 100) in which cross section is exponentially reduced and a tube in which cross section is constant cross section were used. The air column in these tubes was excited using the piston driven by the electromagnetic accelerator in die resonance point vicinity. And the wave motions were measured. By raising the rigidity of the whole system, the improvement in the measurement accuracy was attempted it. In addition, the accuracy of the piston displacement measurement was improved by the introduction of high-precise displacement gage. The results obtained show that the pressure fluctuation in the tube with constant cross section was closely coincident with calculated result in the amplitude and in the wave form at the closed end of the tube. However, the experimental results for the tube with cross section reduction was not coincident with the calculated results, and it shows that the improvement of numerical analysis in the case with large reduction ratio of cross section is required. Less