小型逆布雷顿低温空气制冷机的初步实验研究

Preliminary Experimental Research on a Cryogenic Reverse Brayton Air Refrigerator

近年来,采用逆布雷顿循环的低温制冷机以其效率高、可靠性好、降温速度快、制冷范围广等特性得到广泛关注。本文搭建了一套逆布雷顿低温空气制冷机综合性能实验台,该实验台分为气源部分、制冷部分和性能测试部分。在实验台上可以进行系统降温、透平膨胀机热力及机械性能、回热器传热传质及食品冻结特性等的综合研究。这些研究可为氢、氦等逆布雷顿低温制冷机的研究提供借鉴。对透平膨胀机在常温下的热力性能进行了初步的实验研究,在膨胀比为2.15的情况下膨胀机出口温度2 min内下降33℃以上。其中,自主研发设计的透平膨胀机主轴轴径为10.00 mm,采用波箔箔片轴承支承、最高转速达到278 kr/min,等熵效率达65.5%。实验结果表明,该逆布雷顿低温空气制冷机具有优良的热力性能和降温特性,为后续的相关研究奠定了基础。

In recent years,the low temperature refrigerator with reverse Brayton cycle has been widely concerned for its high efficiency,high reliability,fast refrigeration speed and wide range of refrigerating temperature.In this paper,a test rig of cryogenic reverse Brayton air refrigerator is newly built,in which performances of the refrigerator together with the components could be tested.The test rig is divided into the air supply part,refrigeration part and measurement part.The system cooling performance,thermal and mechanical characteristics of turboexpander,heat and mass transfer characteristics of regenerator,and food freezing characteristics can all be studied on the test rig.It can be used as a reference for research on cryogenic reverse Brayton refrigerators with working fluids of hydrogen and helium.Preliminary experimental study was carried out on the thermal performance of turboexpander at room temperature.The outlet temperature of the expander could drop more than 33℃within 2 minutes under the expansion ratio of 2.15.The main diameter of rotor for the turboexpander was 10.00 mm,which was developed and designed independently.The turboexpander was supported by bump foil gas bearing,the maximum rotating speed was 278 kr/min and the isentropic efficiency reached 65.5%.The experimental results showed that the cryogenic reverse Brayton air refrigerator has excellent thermal performance and cooling characteristics,which laid a foundation for the following research.