气波振荡管波系运动与能量传递效率影响机制研究

Study on wave dynamics and energy transfer mechanism in gas wave oscillation tube

建立了双开口气波制冷机振荡管三维大涡模拟模型,获得了气波振荡管内波系运动特征。针对高压入射喷嘴与气波振荡管在高速旋转交汇过程引发能量损失的问题,探讨了气波制冷机操作参数和结构参数对能量传递效率的影响机制。数值计算结果表明,在两者切入-覆盖-切出的交汇过程中,伴随着强烈的涡旋和湍流动能耗散。定义瞬时湍流动能损失比R定量评定能量损失程度。研究发现,涡旋中心处R值较大,且随绝压压比增大先增大后减小,当绝压压比为3.61时达到最大值9.0%。R值随转速提高而减小,当转速由1100 r/min提高至2000 r/min时,涡旋中心处R值由10.7%减小至6.0%。远轴壁面和近轴壁面涡旋中心处R值都随着管道宽度增加而减小,近轴壁面涡旋中心处的R值大于远轴壁面涡旋中心处,且两侧差值最大达3.2%。减小入射绝压压比、提高转速和增加气波振荡管宽度有助于减小R值,从而提高气波制冷机能量传递效率,对大流量气波制冷机设计具有指导意义。

With the characteristics of higher refrigeration efficiency,smaller equipment size and applicability in extreme operation condition,gas wave refrigeration technology has been widely used in petrochemical,national defense and other fields.Gas wave refrigerator is based on gas wave motion,which has been studied to some extent.Large eddy simulation is employed to obtain the instantaneous spatial form and numerical distribution of shock wave,expansion wave,and other non-stationary motion in oscillation tube.A three-dimensional large eddy simulation model for the oscillation tube of a double open gas wave refrigerator is established.The characteristics of the dynamic shock wave,expansion wave in the oscillation tube are obtained.For violent oscillation,energy loss is caused during the contact of each nozzle and the oscillation tube especially at the high pressure inlet.The influence mechanism for the energy loss of the operation and structural parameters on the energy transfer efficiency is discussed.The numerical results show that there are strong eddies which lead to turbulent kinetic energy dissipation during the contact process.The energy loss is quantitatively evaluated by the instantaneous turbulent kinetic energy loss ratio.The major instantaneous turbulent kinetic energy loss ratio exists at the vortex core,and increases first and then decreases with the increasing of the absolute pressure ratio and reaches the maximum value of 9.0%,when absolute pressure ratio is 3.61.The instantaneous turbulent kinetic energy loss ratio decreases from 10.7%to 6.0%at the vortex center with the increase of rotational speed from 1100 r/min to 2000 r/min.The instantaneous turbulent kinetic energy loss ratio at the vortex center of the far and the near wall both decrease with the increase of the tube width.The instantaneous turbulent kinetic energy loss ratio at the vortex center of the near wall is larger than that of the far wall,and the difference between the two walls reaches a maximum of 3.2%.The energy transfer efficiency of the gas wave refrigerator could be improved by decreasing absolute pressure ratio,increasing rotational speed and the width of oscillation tube,which also has guiding significance for industrial large flow gas wave refrigerator design.