中文摘要：

随着气体在音速喷嘴中膨胀降温，低温气体与管壁的热交换会产生一系列复杂的影响，称之为“热效应”。用于微小流量测量的小喉径音速喷嘴由于喉部直径很小且精度要求高，热效应的影响更为严重。利用热边界层理论分析不同入口压力、不同位置、不同喉径和不同保冷条件下的管壁温度变化规律，根据试验结果，从理论上分析管壁动态温度分布与热边界层的相互作用关系，利用 CFD 软件仿真，分析管壁温度变化引起的边界层厚度变化对音速喷嘴流动特性的影响规律，并通过数据拟合得到了雷诺数和管壁温降对流出系数偏差的影响的计算公式。结果表明，以仿真数据为例，当管壁温降15 K时，由热边界层变薄引起流出系数增大可达0.195%，其影响不容忽视。

英文摘要：

The gas temperature will drop greatly when flowing through the nozzle. The heat exchange between the cold gas and the wall will produce a series of complex effects which are called “thermal effect”. The small-diameter nozzles used in the field of small flow measurement will be influenced by the thermal effect seriously. The laws of temperature variation of sonic nozzles are analyzed by the thermal boundary layer theory with different inlet pressure, locations and throat diameters. According to the experimental data, the dynamic interaction between the wall temperature distribution and the thermal boundary layer thickness is analyzed theoretically. The changes of boundary layer thickness are studied in detail by the CFD method and a formula of discharge coefficient deviation is fitted. It is indicated that the discharge coefficient increases by 0.195% with the wall temperature decreasing by 15 K caused by the thinning of the boundary layer which is necessary to pay more attention.