中文摘要：

在水射流系统中，喷嘴是关键部件，起负载作用（对泵加载，建立系统压力）及能量转换作用（将水的压力能转化为动能）。在不同条件下，喷嘴能量转换效率不同，从而影响水射流系统效率。按能量损失成因不同，将喷嘴能量损失分为特征能量损失和气蚀能量损失。根据喷嘴流量特性，研究能量损失的影响因素及其与流量系数的关系。对圆柱、圆锥及余弦三种喷嘴的流量特性进行试验研究，研究能量损失与进出口条件及喷嘴特征参数间的关系，对比分析三种喷嘴的特征及气蚀能量损失的大小。得出进出口条件对气蚀能量损失有较大的影响，而对特征能量损失几乎无影响；喷嘴特征参数对两种能量损失的都有很大影响，且喷嘴内壁轮廓越接近流线型，喷嘴能量损失越小。本研究为优化喷嘴设计及提高水射流系统效率提供基础。

英文摘要：

The nozzle, which is the load to the pump and converts pressure energy into kinetic energy, is one of very important parts of water jet system. Under different conditions, the nozzle energy conversion efficiency is different, resulting in the effect of system efficiency. Due to the cause of formation, the energy loss of a nozzle is classified as feature energy loss and cavitation energy ones. Based on the flow characteristics, the influence factors and the relation with flow coefficient are investigated. Experiments are carried out to study the flow characteristics of cylinder nozzles, cone nozzles and cosine nozzles and, the effects of the inlet/outlet conditions and the nozzle features are addressed. Comparison analyses have been made on the feature and cavitation energy loss of the three nozzles. The results show that the inlet conditions greatly influence the cavitation energy loss and have little effects on feature ones, and that the nozzle features significantly affected both kinds of energy losses and they tend to be smaller when the inner surface is closer to streamline. The related conclusions provide a basis for the nozzle optimal design and the improvement of the efficiency of water jet system.