| Rotating-sleeve distributing-flow system overcomes many shortcomings of traditional valve distribution system,such as loose structure,lagging motion,large loss of local throttling pressure and so on.The reciprocating motion of piston drives the rotating-sleeve to continuously unidirectionally rotate and accomplishes distribution function through the distribution port.However,there is a large negative pressure in the distribution system during the oil absorption stage,which will cause cavitation inevitably and affect the performance of distribution system seriously.In view of the above problems,the cavitation characteristics of rotating-sleeve distributing-flow system are analyzed through analogue simulation and experimental study,which provides theoretical basis for structural improvement and optimization design.According to the hydraulic test environment,the structure of rotating-sleeve distributing-flow system has been designed improved,including pump body shape,cam groove profile equation,vibration reduction groove angle and so on,and the relevant size parameters are determined.At the same time,the cavitation analysis model of whole flow distribution system is established with the created of computational geometry model in fluid domain and introduced of cavitation theory.The cavitation characteristics in the flow field were simulated using hydraulic oil as the fluid medium under the standard conditions(rotating speed is 500r/min,load pressure is 10MPa)and the relationship between flow field pressure and cavitation gas was analyzed in depth.Cavitation gas appears in the initial stage of oil absorption and mainly distributed in the distribution port and pump chamber.The maximum average gas volume fraction of pump chamber is 42.6% and the cavitation duration occupies 20% of a single working cycle.Cavitation effect of the pump chamber is higher than that of the distribution port on the whole,and the volume efficiency of distribution system is less than theoretical value because of the existence of cavitation.Analyzed the kinematics of four different cam groove of arcsine,linear,tangent and spline profiles.The linear cam groove has the best performance overall,which is beneficial to stable operation when the sleeve rotates.The angular acceleration of arcsine cam groove has no obvious step,and the force condition is the best.Compared with cavitation characteristics of four grooves by simulation in different rotational speeds,the linear cam groove has the lowest cavitation effect and the maximum volume efficiency is 92.13%.Also the linear cam groove has great advantages in different inlet pressure and the volume efficiency is always above 92% with a smaller fluctuation by the change of working environment.Comparing and analyzing the cavitation characteristics of two kinds of vibration reduction grooves with the same volume,the cavitation effect of U-groove is slightly lower than that of triangular groove under standard conditions.The cavitation effect of U-groove is lower than that of triangular groove under different rotational speeds,and the higher rotational speed,the more obvious advantage is.Increasing the inlet pressure can restrain the generation of cavitation gas,and the triangular grooves have more advantages when inlet pressure is higher.Design the support bench of rotating-sleeve distributing-flow system according to the environment of hydraulic test and make the test prototype to establish visual system.The cavitation gas in the distribution system is observed by a high-speed camera,and the volume efficiency of the distribution system is monitored by a test bench under different working conditions.The overall change trend is consistent with the simulation results. |
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