Abstract:

The moving shock in gas wave tube of gas wave refrigerator was reflected back from closed end boundary of the tube. If the reflected shock wave was back to open mouth of the gas wave tube it will heat the expanded refrigeration gas at the open end, and reduce refrigeration efficiency severely. Analysis shown that pre-existing efficient tail end absorbing cavity type gas wave tube was not enough for attenuating and damping reflected shock, therefore a novel middle damping cavity type gas wave tube was put forward. By the contrastive analysis of motion wave train in both tubes,the comprehensive mechanism of the middle damping cavity were uncovered, those include damping reflected shock, turning back reflected shock to backend section of the tube, and converting part of the incoming shock wave to expansion wave which may counteract the reflected shock wave of escape from damping cavity. Computational fluid dynamics numerical simulation shows that the new type of gas wave tube could improve the refrigeration efficiency by 7%-11% relatively if the gas injection frequency higher than the second high efficient frequency, and trough efficiency about 18% relatively, so the refrigeration efficiency curve tends to smooth. The two cavities type gas wave tube combined by middle damping cavity and existing tail end absorbing cavity could improve the refrigeration efficiency corresponding to the low and medium frequency gas injection by 6%-8% relatively. The efficiency curve was more smooth. Refrigeration efficiency of three type gas wave tubes were measured and compared by the single gas wave tube model experiment. The performance of high efficiency and smooth efficiency curve of new type gas wave tube were proved. The amplitude contrast and trends of refrigeration efficiency of three type gas wave tubes and gas injection frequency corresponding to peak and trough points of efficiency, were in conformity with the simulation results.

Key words: refrigeration, gas wave tube, reflected shock wave, optimal design, numerical simulation, absorbing cavity and damping wave cavity

摘要：

气波制冷机气波管内的运动激波，在管内封闭末端将反射回行。若反射激波回到气波管开口端，会加热已膨胀制冷的开口端气体，严重降低制冷效率。考察分析已有高效的末端吸收腔式气波管，其衰减和阻止反射激波的效果还不理想，因此提出了一种中部阻波腔式气波管结构。通过对管内运动波系的对比分析，揭示了该中部阻波腔的综合作用机理：不只是对反射激波进行阻减，还能将其重新折回气波管后段，且将部分入射激波反射成膨胀波，与逃出阻波腔的反射激波相抵消，共同遏制反射激波回到气波管开口。CFD数值模拟表明，与已有广泛应用的末端吸收腔式气波管相比，新型气波管可使高于第二高效注气频率对应的制冷效率相对提升7%～11%，波谷提升约18%，使制冷效率曲线趋于平坦；而将中部阻波腔与已有的末端吸收腔共用，组成双腔式气波管，还能使低、中频注气时的制冷效率相对提高6%～8%，效率曲线更平。又以单管模型机实验测量对比三种型式气波管的制冷效率，证明了新型气波管的高效和效率曲线的平坦性能；实验三种气波管制冷效率幅度的差别和趋势，以及效率峰值、谷点所对应的注气频率，都与模拟结果相符。

关键词: 制冷, 气波管, 反射激波, 优化设计, 数值模拟, 吸收腔和阻波腔