中文摘要：

采用缝隙测压方法，测量了内径从0．245mm到0．850mm的三种不同面积比的微通道内氮气和氦气突扩时的局部阻力损失。结果表明，两种气体的局部阻力系数不同。在层流阶段，微通道内的两种气体突扩阻力系数都要高于常规管的值，氦气的突扩阻力系数还高于氮气的阻力系数。而在湍流阶段，由于气体的可压缩性，突扩阻力系数随雷诺数的增大而增大。而且通道面积比越小，突扩阻力系数增加的幅度越大。

英文摘要：

Local resistances of nitrogen and helium across sudden expansion in small channels with diameters from 0.245 mm to 0.850 mm were experimentally investigated by using a pressure measurement method of the tiny gaps on the channels. The results showed that the local resistance coefficient was different for two kinds of gases. In laminar flow, the expansion coefficient for nitrogen and helium in mierochannels is higher than that in conventional tubes, expansion coefficient of helium is higher than the nitrogen. In turbulent flow, the expansion resistance coefficient increases while Reynolds number increasing due to gas compressibility. In addition, the amplification of expansion coefficient is increasing with area ratio decrease.