Study On The Characteristic And The Internal Flow In Super-high Pressure System Of The Water Jet Cutting Machine

As a new processing technology, the super-high pressure waterjet cutting is developing quickly and accepted by more and more enterprises, because its characteristic of high energy, cooling cutting, point cutting and no pollution. Along with the water pressure increasing, the fluctuation of pressure in the super-high pressure system become a main influencing factors which block its application. The reasons and the influencing factors of the fluctuation of pressure are being analyzed based on the former reseaches. The innovative achievements and important conclusions obtained as follows:1. Reveal that intensifier’s discontinuity supply water is the direct reason of the fluctuation of pressure by analysing the operation principle of the intensifier. The value depends on compressing water time and the reversing valve’s response time. The whole water jet cutting system is simulated by the dynamic simulation tool SIMULINK software package of MATLAB and the influencing factors of the fluctuation of pressure are obtained:the fluctuation of pressure relate with working pressu(?)、the ratio of water pressure and oil pressure、attenuator、the time of commutated in single-intensifier system, but in many-intensifiers system the influencing factors of the fluctuation of pressure relate with working pressure、the ratio of water pressure and oil pressure、attenuator、the time of commutated、the delay time and the number of intensifier.2. Analysing the bubble’s expanding、compressing and breaking process in HP cylinder based on the basic theory of the bubble dynamic.The differential equations are obtained and the conclusion is gained that the gas in intensifier will increasing the temperature of HP cylinder.3. Differential equations with different time were founded based on the second law of Newton and the compressible equation of water. The numerical solutions were gained from MATLAB software. The analysis reveals that the intensifier have different moving characteristics in three different displacement time. First, the velocity is continual increasing with the acceleration is reducing; then the velocity is reducing with the acceleration is increasing;finally the velocity is reducing with the acceleration reducing. In the entire displacement, the maximum velocity is higher than the average velocity. The experiment proves it’s reasonable.4. The interior flow passage in intensifier are drawed by UG NX4.0. The process of expanding water、compressing water and different mediator’s compressing are simulated by the dynamic mesh technology of computation fluid dynamic software FLUENT.It reveals that the hydraulic pressure is regularity in the process of compressing water but in the process of expanding water is not that and if the intensifier contains gas,the time used to compress water will increase, the pressure fluctuation will increase and the performance of this equipment will go bad.5. Found the experimental platform of gas-liquid two phase flow in intensifier. The fluctuation of pressure under different gas content are obtained and the conclusions are that:if the gas content is more higher, the stroke time is more shorter and the compress time is more longer, the fluctuation of pressure and the temperature of HP cylinder are more higher. It is according with the front analysis.