Effect Of The Area Of The Main Valve Core On The Maximum Pressure Of High Pressure Pulse Water Hammer Device

When high pressure pulse water hammer device is mainly used for coal seam water injection, alternating stress produced by water hammer shock can expand and connect porosity of coal seam, so the higher peak of fluctuation pressure is benefit to the coal seam water injection. It is necessary to increase the peak of pressure.Firstly, This paper analyzes excitation mechanism of pressure shock wave and the propagation process of pressure wave. Then, the mathematical model of high pressure water hammer is built. And, force conditions and movement of plunger component in the process of impact force is analyzed. By analyzing the flow of fluid in low pressure cavity after the main valve core is opened, movement differential equation of high pressure pulse water hammer is finally established. And general solution was obtained. By setting parameter the numerical calculation is carried on. It’s concluded that peak pressure increases with the increasing area of the main valve core and the area of annular channel which is formed by the valve core coat and the main spring seat ring and gradually stabilize. This is due to the increasing area of annular channel and the area of main valve core enlarge the area of drain channel of water flowing from low pressure cavity and reduce the area of throttling, just the extensive position is different. The influence to peak pressure is consistent, which can be analyzed qualitatively.Then, this paper carries on experimental research and the test bench is Built. In order to save time and simplify the experiment, this test does not directly choose to change the area of main valve core, but by adding gasket with different area on the valve core coat to change annular passage area. Under the condition of different pressure of supply water, four groups of experiment was done respectively and collects pressure of high pressure cylinder export, pressure of the line transient end and displacement data. The area of gasket is translated into the area of annular passage, and parameters of numerical calculation is set according to the experimental parameters for numerical computation. Through the comparison and analysis found that calculating data agrees well with that of testing, and the basic error is within the acceptable range, which verified the correctness of the theoretical calculation. And it is analyzed that peak pressure increases with the increasing area of the main valve core and gradually stabilize under different supply pressure. And it will be stabilize gradually. The conclusion is consistent with the theoretical analysis, At the same time, it is concluded of law of reflection of pressure on blind end. That is the nature of reflection wave and incident wave is the same, and pressure value of reflection point is a linear superposition of incident wave and reflected wave.Finally, according to the influence law of the area of main valve core into peak voltage of high pressure pulse water hammer, two measures are put forward.(1)we can save the main spring seat. If do that, water in low pressure cavity flows out from the main valve and outlet hole of the valve core coat, then it is directly discharged into the atmosphere. It may reduce the back pressure and increase the area of blow-off channel.(2)Six solenoid valve can be uniformly distributed along the circumference of low pressure cylinder circumference. When the energy are accumulated, solenoid valve are closed. Until reaching a certain trigger position, solenoid valve will be open. At this time, low pressure cylinder starts to discharge pressure. And piston begins to hit the water in the high pressure cylinder. The speed of leakage flow is also greatly accelerated. The output pressure will be increased.