| As the power source of the working face hydraulic support,the emulsion pump station has a very important position in the whole comprehensive mining work.Its performance directly affects the efficiency of the comprehensive mining.Because the large mining height hydraulic support requires high setting force and high working resistance,and it also needs to meet the requirements of rapid frame removal and safe support,the pressure and flow requirements of the hydraulic system of the comprehensive mining face become higher.With the development of the emulsion pump to ultra-high pressure and large flow,the movement frequency of the valve is fast and it is subject to frequent conversions of high and low pressure.Due to the greater inertia of the valve movement,the hysteresis of its response has become more serious,which leads to the pressure pulse is very large when the valve is opening.The generation of negative pulse causes the emulsion to boil and create bubbles.When they move to the high-pressure zone,they will burst and produce micro-jets acting on the inner wall of the metal,which will induce noise and cause fatigue damage to the parts.This paper took the BRW1200/40 as the research object,and analyzed the hysteresis and cavitation phenomenon of the valve by establishing the mathematical model and doing simulation analysis in order to improve it.The main research contents are as follows:1)The movement law of the five-plunger emulsion pump was analyzed in detail,the mathematical model of the kinematics of the emulsion pump was established on the basis of considering hysteresis and cavitation,and a detailed single-plunger cavity flow model and pressure model is established.2)Based on the values provided by the partner,a simulation model of the emulsion pump was established by AMESim.The movement characteristics of the plunger and the valve were analyzed,and the pressure and flow rate changes were obtained.The result shows that the pressure pulse is large when the valve is opening,and there are flow pulse and backflow phenomena.The volumetric efficiency of the pump is only 77.26% which the flow loss was serious.3)The influence of the spring values,spool quality,plunger diameter,crank speed and dead volume on the lag time of the valve was studied by AMESim,and the relevant values were improved to obtain an optimized scheme.Compared with the original scheme,the lag time of the valve in the optimized scheme is reduced by about 40%,meanwhile,the volumetric efficiency is increased from 77.26% to 93.6%,and the pressure pulse is also significantly improved when the valve is opening.4)The dynamic simulations of the flow field of the suction valve of the two schemes were carried out by using the dynamic mesh technology.The result shows that the negative pressure was generated in the plunger cavity when the spool is opening in the two schemes,but the optimized scheme have shorter negative pressure duration than the original scheme.When the valve reaches the maximum opening,the flow area between the inner wall of the plunger cavity and the valve is too small,which cause the emulsion to flow poorly and form the vortex at the valve seat hole.Meanwhile,a negative pressure is formed at the center of the vortex,and then the pressure rises and the negative pressure disappears with the movement of the plunger. |
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