【作者】 陈圣涛；

【导师】 胡大鹏；

【作者基本信息】 大连理工大学 ， 化工过程机械， 2008， 博士

【摘要】 气波制冷机作为一种有效利用气体压力能的设备而备受瞩目。静止式气波制冷机是利用带压气体本身的压力能,通过振荡器把带压气体转变成稳定的振荡射流交替射入接受管,利用激波和膨胀波的运动,实现冷热分离,从而达到降温制冷的目的。其突出的优点是无需额外的能量输入且机器没有运动部件。本文的研究对象是以音波振荡器和正反馈振荡器作为振荡源的双管式静止气波制冷机。本文的主要工作与结论包括以下几方面的内容:1.研究了超音速音波振荡器和正反馈振荡器中射流的流动过程和振荡机理。本文建立了音波振荡器和正反馈振荡器的二维模型,研究了超音速射流在振荡器中附壁、切换和振荡的过程。研究发现,射流在音波振荡器中近似以“方波”的形态持续振荡,而在正反馈振荡器中以“正弦波”的形态振荡。在射流附壁时,在分流劈之前的主射流区内部有膨胀波与压缩波交替反射传播。在振荡过程中,控制管中气体的压力和动量共同对射流的切换起作用。控制口的压差随着射流振荡的过程,呈现周期性的变化,压差作用于控制管内气体时间的长短决定了控制管内气体速度的大小。流体本身的特性,如粘性,也影响振荡的切换周期。本文分析了入口喷嘴、劈距、出口通道等不同的几何参数对振荡器内射流振荡和流动的影响。减小劈距可以减少因卷吸而倒流进入音波振荡器的气体的量,从而减少射流的能量损失,提高出口压力恢复;而减小出口通道的长度由于降低了射流的沿程损失,同样有助于提高出口压力恢复。位差、出口通道宽度、分流劈角度、分流劈形状等都对振荡器的振荡性能有不同的影响。2.研究了接受管中气体和波系的运动与传播过程。入射气体在接受管中只能运动相对较小的一段距离。气体接触面开始运动的速度较快,之后为减速过程直到最大距离处,持续一段时间后以较快的速度反向排出。研究了不同压比下波在接受管中的传播过程。激波经过后,气体的压力、密度和温度都会有明显的升高。波在长直接受管的封闭端有明显的反射现象。研究了不同结构和形状的激波吸收器。结果表明收缩—突扩结构的接受管可以较明显的消除反射波的影响。研究发现,接受管结构的改变,导致气体的压力特性和相位与普通长直管不同,可以利用收缩—突扩结构的接受管起到调相作用。正反馈振荡器作用的高频射流,振荡射流的平均压力呈现周期性变化。3.研究了气波制冷机的不同的操作参数和结构参数对制冷特性的影响。结果表明,提高气波制冷机的入口压力,可以增大出口气体的温降,入口温度的提高也会导致温降的增大。射流振荡频率与接受管长、入口压力等有匹配关系,最高温降对应于一个最佳射流频率。振荡器与接受管之间的排气间隙的大小影响气波制冷机的制冷特性,排气间隙的大小有一最佳值。高频情况下的正反馈振荡器作为振荡源,射流对接受管内气体的做功频率较高,相对于较低频率的音波振荡器,可以得到更高的温降。更多还原

【Abstract】 Energy source and environmental problem are becoming more and more important for the whole society, and the gas wave refrigerator has been the focus for the effective use of the pressure energy. The static gas wave refrigerator can separate the gas into hot and cold part by the motion of the shock wave and expanding wave in an oscillator using the pressure energy of the gas. So the refrigeration can be realized. The prominent advantage of this facility is that it doesn’t need extra energy supply and there is no moving part. In this paper, the two-tube static gas wave refrigerator generated by a sonic oscillator and a feedback oscillator is studied. Pressure gas is converted into oscillating gas and injected into the receiving tube by using a sonic oscillator and a feedback oscillator. The work and conclusion of this study are as follows:1. The supersonic oscillation process and principle in the sonic oscillator and feedback oscillator are studied. A two dimension computational model is applied to simulate the attatchment, switch, oscillation and pressure wave in the sonic oscillator and feedback oscillator. The jet flow oscillates as a "square wave" in a sonic oscillator and "sine wave" in a feedback oscillator. As the jet flow is attaching to the wall, there is expanding wave and compressing wave in the jet flow zone. During the oscillation, both the pressure wave and the gas momentum act on the switch of the jet flow. The pressure difference between the controlling ports is also periodic as the jet flow oscillates, and the time the pressure difference acts on the gas in the controlling pipe determines the velocity of the gas. At the same time, the viscosity of the gas affects the period of the oscillation.The oscillation and flow in the oscillator is analyzed under different parameters of nozzle, splinter distance, outlet tunnel and so on. If the splinter distance is reduced, the gas involved into the oscillator also decreases, and so the energy loss can be reduced, so the outlet pressure recovery increases. Minimizing the length of the outlet tunnel can also be helpful for increasing the pressure recovery. At the same time, potential difference, the width of the outlet tunnel, degree of the splinter, shape of the splinter and so on can also contribute to the pressure recovery, and general consideration should be taken in designing and applications.2. The gas and wave’s motion and propagation in the receiving tube are studied. Fresh gas in the receiving tube can only move for a short distance, and the contact face accelerates at first, then keeps for a while, and then exhausts rapidly. The wave moves in a certain speed and under different pressure ratio, the speed also varies. As the wave sweeps, the pressure, density and temperature of the gas rise rapidly. There is obvious reflection as the wave arrives at the close end of the straight long pipe. Different types of wave absorber are studied. The structure of shrink-expand in the close end can absorb the reflected wave. For the different oscillation of the jet flow and the different structure of the receiving tube, the pressure wave in the receiving tube is also different. So the phase can be adjusted by using the shrink-expand wave absorber. The average pressure of high frequency generated by a feedback oscillator is periodic.3. By the experimental study of the two-tube static gas wave refrigerator generated by a sonic oscillator and a feedback oscillator, influence of operating parameters and structure parameters is analyzed. Matching the other parameters, as the inlet pressure rises, the temperature drop also rises. The temperature drop also rises as the inlet temperature rises. Matching with the oscillation frequency, the length of the receiving tube, diameter of the nozzle and the pressure ratio, there is a best injecting frequency. The gap between the oscillator and the receiving tube also influents the refrigeration. There is also a best exhausting gap. If the gas is gernated by a high frequency oscillator- a feedback oscillator, as the frequency to drive the gas in the receiving tube is also high, so higher temperature drop can be realized as to the sonic oscillator.更多还原