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将喷管内有摩擦的稳定流动转化为等效多变过程进行研究,揭示了摩擦影响工质状态变化的规律.研究发现喷管的喉部不是临界截面,而是壅塞截面且马赫数Mc＜1,摩擦愈大壅塞马赫数愈小.摩擦阻力导致临界截面向下游移动,摩擦愈大,离喉部愈远.根据背压判断采用渐缩喷管还是缩放喷管的关键参数是壅塞压力比,非临界压力比.壅塞压力比既与工质的物性有关,也与摩擦耗散有关.导出壅塞马赫数、壅塞温度比和壅塞压力比的计算公式,有效解决喷管喉部相关参数计算的关键问题.“,”To study the frictional steady flow in nozzle,this kind of flow is transformed to equivalently reversible polytropic process.By this means,the studying result reveals that how friction influences states of working medium.According to our study,the throttle section in nozzle is choke section but critical section and Mach number in choke section is less than 1.The greater the friction is,the smaller the Mach number of choke section is.It is friction that makes Mach number in choke section be less than one and critical section move to the downstream.The greater the friction is,the greater the distance between choke section and critical section is.Choosing convergent nozzle or Laval nozzle depends on choke pressure ratio but critical pressure ratio.Choke pressure ratio is related to characteristics of working medium and frictional dissipation.Calculating formulas about choke Mach number,choke temperature ratio and choke pressure ratio are derived and a vital problem of calculating related parameters of the minimum section in nozzle resolved effectively.