Abstract: Taking the pressure relief process of pneumatic jetting valve as the research object,the two-dimension model of coupled system of pressure relief process and needle motion process were putted forward,the unsteady flow field was calculated by finite volume method and dynamic mesh with the turbulence k-ε model,then the pressure relief curve of back pressure zone and needle motion curve was achieved.The results show that the jetting performance is limited for great back pressure resistance in jetting.By reducing pressure relief airway length or increasing pressure relief airway diameter,the needle speed can be increased and the needle motion response time can be reduced.The calculation results are consistent with those of experiment,which illustrates a new way for calculation and analysis of pneumatic jet dispensing and provides reference for structure optimization of the valve.

Key words: jet dispensing, pressure relief process, needle motion, finite volume method