A Numerical Investigation For The Flow Field Of The DC Fire Monitor Nozzle With Different Contraction Curves

This article investigated for the flow field of the DC(direct-current)fire monitor nozzle with different contraction curves.The steady flow of the nozzle was conducive to prolong the jet range for fire monitor,and its jet performance was affected by the contraction curve.The method of this article was numerical simulation,combined with Fluent software,and the basic conditions were inlet pressure of 1 MPa,flow rate of 50 L / s,contraction ratio of 2.1: 1 and shrinkage angle of 13?20?30 and 40 degrees.The investigation showed that the two contraction curves of the nozzle model formed different velocity gradients and pressure gradients.If it was circular curve,there was a large pressure gradient and velocity gradient at the nozzle near the outlet,resulting in a large suction angle,which was detrimental to extended jet range.In contrast,if it was double cubic curve,there was a small pressure gradient and velocity gradient at the nozzle near the outlet,with a small take-up angle,effectively maintaining the jet range.The investigation also found that the nozzle with double cubic curve could form a negative pressure in the area adjacent to the outlet.The negative pressure increased with the increase of the contraction angle,which was conducive to improving the nozzle flow coefficient,however,it didn't increase monotonically with the increased of negative pressure,but there was an extreme value,when the contraction angle increased to 36 degrees,the flow coefficient reached the extreme value of 0.966,and then decreased gradually as the contraction angle increased.