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Numerical modelling of percussion water jets driven by multiple collisions

A numerical model is proposed in this research to analyse the behaviour of the pulse jet driven by percussion hammer. The mass of the hammer is usually larger than that of the piston and the resistance of compressed water can low down the piston, thus multiple collisions occur each time when the hammer strikes the piston. The proposed model has the merit to consider various striking possibilities to simulate the process of pulse water jet generated by multiple hammer collisions. In addition, a hammer-driven percussion pulse jet is developed and the corresponding experiments are carried out for verifying the reliability of the numerical model. Comparison results show that the predicted pressure and velocity values match well with the experimental data. The simulation of the generation of pulsed jet reveals the collisions and motions of the hammer and the piston and provides understanding of the mechanism of the pulse jet generation. The design of the hammer-driven pulse water jet device can be optimised through modelling different combinations of the parameters of the chamber, hammer, piston and nozzle for a specific purpose of rock fragmentation.