针对水下岩石破碎过程中存在环境阻力大.破岩效率低等问题.提出一种水下气体辅助水射流的跨介质射流破岩新方法.在分析水下气体辅助水射流基本特性的基础上.搭建了可模拟气体辅助水射流破岩试验系统.探究了工作参数和喷嘴结构参数对水下气体辅助水射流破岩性能的影响.结果表明:岩石破碎是由水相水锤压力与气相空泡溃灭微射流共同作用的结果.在研究范围内.气流压力小于0.4 MPa时.气相空泡溃灭微射流引发的岩石破碎对气流压力的变化更敏感.而大于0.4 MPa时.水相水锤压力造成的岩石破碎对气流压力的变化更敏感.外喷嘴收缩段结构的变化对空泡发育的影响与其对射流冲击动压的影响相比较小.增大外喷嘴出口直径.射流的集束性出现先增加而后减小的趋势,随着外喷嘴直线段长度的增加.水下气体辅助水射流中空泡发育程度逐渐增强.但由气.液动量交换和摩擦阻力引起的能量损耗随之增加.与普通淹没射流相比.气体辅助可使得水射流破岩体积最大提高约1.5倍.比能耗则降低40%.随着气流压力的升高.岩石破碎体积先增大后减小.最佳取值为0.4 MPa,延长冲蚀时间.岩石破碎体积随之增加且有逐渐减缓的趋势.冲蚀时间设为30 s可兼顾水下气体辅助水射流的破岩性能与经济性.外喷嘴最佳结构参数组合为:指数型收缩段.出口直径3.5 mm和直线段长10 mm.

Aiming at the problems of high environmental resistance and low efficiency in the process of underwater rock breaking.a new method of rock breaking by cross medium jet.which called gas-assisted water jet.is proposed. The basic characteristics of underwater gas-assisted water jet are analyzed.and the effects of working parameters and nozzle structure parameters on rock breaking performance and flow pattern of underwater gas-assisted water jet are explored based on relevant test bench. The results show that the rock fragmentation is caused by the combined action of water hammer pressure in water phase and micro jet in gas phase. When the airflow pressure is less than 0.4 MPa.the rock fragmentation caused by the cavitation collapse microjet is more sensitive to the change of airflow pressure. However.when the airflow pressure is greater than 0.4 MPa.the rock fragmentation caused by the jet impact dynamic pressure is more sensitive to the change of the airflow pressure. The change in the structure of the constricted section of the outer nozzle has less influence on the development of cavitation than it has on the jet impact dynamic pressure. Increasing the exit diameter of the outer nozzle.the clustering of the jet first increases and then decreases. As the length of the straight section of the outer nozzle increases.the degree of cavitation in the underwater gas-assisted water jet gradually increases.but at the same time.the energy loss caused by the gas and liquid momentum exchange and frictional resistance increases. Compared with the common submerged jet.the maximum rock breaking volume increased by 150% and the specific energy consumption decreased by 40%. With the increase of airflow pressure.the volume of rock fragmentation first increases and then decreases.and at the same time.the specific energy consumption first decreases and then increases. The best value is 0.4 MPa. Extend the erosion time.the rock fragmentation volume will increase and gradually slow down. The erosion time is set to 30 s.which can take into account the rock breaking performance and economy of the underwater gas-assisted water jet. The optimum structure parameters of the outer nozzle are:exponential contraction section.3.5 mm outlet diameter and 10 mm straight section length.

1 喷嘴结构设计

2 水下气体辅助水射流破岩性能试验

   2.1 水下气体辅助水射流破岩试验系统

   2.2 岩样力学性能

   2.3 试验方案

3 试验结果及分析

   3.1 气流压力

   3.2 冲蚀时间

   3.3 外喷嘴收缩段结构

   3.4 外喷嘴直径

   3.5 外喷嘴直线段长度

4 结论