低温风洞极低露点快速测量装置研制

露点是低温风洞运行的关键参数,为解决低温风洞极低露点(–100℃)测量中存在的响应速度低、量程小和精度不高的问题,在–80℃露点测量装置研究基础上,通过优化专用斯特林制冷系统性能,大幅缩短降温时间;采用具有内狭缝换热器的一体化镜面,提高镜面结露的均匀性,使得反射光强度阶跃特征点更清晰;测量光路上加装球面镜头,提高–100℃露点温区结露时光电信号的强度,保证测量的可靠性;采用基于周期法露点测量方法,避免镜面结露的平衡振荡过程,缩短露点检测周期,提高露点测试响应时间。测试结果表明,在–100℃露点温区时,实现±1℃的露点测量精度,从–90℃到–100℃露点温区的露点测试响应时间仅为12 min,可以满足低温风洞极低露点测试的需求。

Research on fast measuring dew point meter for low temperature wind tunnel

Dew point temperature is a key parameter for low temperature wind tunnel operation.At present,the dew point temperature(–100℃)measurement has the problems of slow test response time,small range and low accuracy.To meet the specific needs of low temperature wind tunnels,based on the research of–80℃dew point measurement device,the measurement device studied in this paper can greatly reduce the cooling time by optimizing the performance of dedicated Stirling cooler.The integrated structural mirror surface with internal slit heat exchanger improves the uniformity of the condensation on mirror surface,making the characteristic points of reflected light intensity step clearer,which is conducive to the accurate identification of low dew point.A spherical lens is installed on the measuring optical path to increase the intensity of photoelectric signal when–100℃dew point is measured to ensure the reliability of the measurement.The periodic method is used to avoid the balanced oscillation process of condensation on the mirror and shorten the measuring time,and greatly improve the response time.The test results show that the accuracy of±1℃is achieved in the–100℃dew point,and the test response time from–90℃dew point to–100℃dew point is only 12 minutes.The low dew point test device can meet the fast measurement requirements of low temperature wind tunnels.