Characteristics of flow field in Laval micronozzles with 34 μm throat-width were studied numerically by using continuum and direct simulation Monte Carlo(DSMC) method.Three types of micronozzles with different throat shapes were designed

such as:sharp-corner

smooth-corner and flat-corner.Based on the geometric structure design

effects of throat shape and expansion ratio on flow field and propulsion performance were analyzed

respectively.It is discovered from the results that

the comprehensive propulsion performance of the micronozzle with smooth-corner throat is the best

while the micronozzle with flat-corner throat has much better specific impulse efficiency.When the expansion ratio becomes larger

both thrust and specific impulse will increase.