| Elaborately designed mathematical model of liquid jethammer and simulation software upon the model are importantto the optimization of its performance. In the model developedby other researchers the fluidic amplifier— the core componentof the hammer was ignored, which resulted in great differencebetween the simulated P— T curves and the observed. The oldmodel predicts that the increase of mass of the piston-blockunit will result in the increase of impact energy and blowfrequency, while the results of repeated experiments show thatimpact energy increases and blow frequency decreases.Besides, the impact of the energy-saving mechanism isn'tconsidered in the old model. In this work new mathematical models were elaboratelybuilt and discussed in detail. These models include the modelwithout energy-saving mechanism and models withenergy-saving mechanism. Based upon the new models, anew simulation software was developed. With the help of thesoftware the impacts of 15 parameters on the performance ofliquid jet hammer were numerically analyzed. The new model of the liquid jet hammer withoutenergy-saving mechanism was similar to that of an impulsewater turbine. In the new model, the fluidic amplifier isconsidered, and the pressures of liquid in the fore and rearworking chamber were expressed clearly in mathematicalforms. The figures of P— T curves predicted by the model arebasically similar to the observed. The magnitudes of pressurepulses produced at the end of each stroke can be predictedrelatively precisely according to the new model and simulationsoftware. The predicted impacts of parameters upon theperformance of the liquid jet hammer are consistent with the 4results of previous repeated experiments. But there existerrors caused by some random factors such as additionalfriction forces between the piston-block unit and the outer tube.Such factors are not taken into account because of theircomplexity but their impacts are usually great. On the basis of the model of liquid jet hammer withoutenergy-saving mechanism, models of liquid jet hammer withenergy-saving mechanism were set up. According to themodels, the performance of liquid jet hammer withenergy-saving mechanism, the pressures of the liquid in thefore and rear chamber and the volumes and pressures of theaccumulators can be predicted. The results of numerical analysis show that: (1) theimpacts of accumulators connected to the fore and rearchamber on impact energy and blow frequency are very little.(2) the impacts of energy-saving mechanism of spring on theperformance of liquid jet hammer are also little. (3) the impactsof energy-saving mechanism of buffering accumulator fixed atthe rear end of the inner cylinder are great. According to the results of numerical analysis, theperformance of liquid jet hammer is not sensible to change ofinitial volume and charge pressure of the buffering accumulator,but the impact velocity of the piston-block unit and blowfrequency will increase by 46% ～ 62% and 10% ～ 15%respectively when buffering accumulator is connected. Changeof the diameter of the buffering section of the piston couldcause great changes of impact velocity and blow frequency.Under a definite condition, when the diameter of the bufferingsection of the piston varies from Φ 42mm to Φ 10mm, theimpact velocity will increase from 4.23m/s to 8.22m/s.Compared with the liquid jet hammer without energy-savingmechanism, impact velocities and impact energy increase by77% ～ 244% and 213% ～ 1083% respectively, and blowfrequency increase by 28.4% ～ 46.6%. Under definiteconditions change of the buffering stroke (defined as thedistance between the rear end and the inlet of the buffering 5cavity in the inner cylinder when the piston-block unit at thelowest positio...
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