斯特林制冷机排出器气动力特性研究

A study on gas dynamic characteristic of displacer in Stirling cryocooler

基于排出器动力特性的矢量分析,针对1台2 W@80 K双驱动分置式斯特林制冷机,开展实验,研究压力波动、运动阻尼和固有频率随制冷温度的变化,分析了其对制冷机性能的影响。结果表明:制冷温度降低时。压差和压力-位移相位角均呈减小趋势,膨胀腔功减小;排出器运动阻尼随制冷温度的降低而增大,导致蓄冷器压降增大,冷腔内平均压力降低,气动力减小,气动力与排出器位移夹角减小,排出器行程减小,膨胀腔理论制冷量减小;低温下膨胀机内气体弹性刚度增大,其固有频率增大,向运行频率接近,伴随电机驱动力下降;压缩活塞通过其运动产生的气流压力波对排出器的运动产生影响,排出器则通过其运动产生气流的质量分配和动量分配影响气体弹簧刚度和气流阻尼来反作用于压缩活塞。

Based on the vector analysis of dynamic characteristic of displacer in a split-type Stirling cryocooler, experimental study was performed on a cooler of 2 W@ 80 K, to uncover the relationship among pressure fluctuation, damp, natural frequency, cold-tip temperature and the cooling performance. It indicates that： 1 ） Pressure amplitude and phase shift between pressure and displacer motion decrease when the cooling temperature falls. 2） Dynamic damp of the displacer increases at lower cooling temperature, which results in the increase of pressure drop of the displacer, and the decrease of average pressure of the cold cubage, gas dynamic pressure, phase shift between pressure and pressure and displacer motion, displacement of the displacer, and the PV power. 3） Natural frequency of the regenerator increases because of the augmentation of gas spring constant at lower cooling temperature. The natural frequency is more close to the operating frequency, so the drive current of motor is falling down. 4） Piston of compressor affects displacer of regenerator by the pressure fluctuation engendered by its motion, and displacer reacts by changing mass and momentum distribution in order to adjust the gas spring constant and the damp coefficient.