Research On Pressure Feedback Flow Distribution System And Oil Return Characteristics Of Hydraulic Pile Hammer

Due to the advantages of low pollution, low noise and high efficiency, hydraulic pile hammer was widely used, and it becomes the future important development direction for the pile driving machinery. Take nitrogen pressure as feedback signal, flow distribute main control valve as control equipment, and rely on nitrogen expansion and gravity power to get impact kinetic energy, the pressure feedback flow distribution system of nitrogen-expansion hydraulic pile hammer has the features that its energy density is large and it can regulate impact energy and frequency on time steplessly. The paper relying on science and technology projects in Hunan province studies the overall scheme, critical components and characteristics of oil return system of pressure feedback flow distribution system of hydraulic pile hammer.Firstly, the product development status and theoretical study dynamics of hydraulic pile hammer at home and abroad is introduced. The characteristics of different flow distribution system are comparised, the overall scheme of pressure feedback flow distribution system is put forward, and its working principal is analyzed. The research directions for improving the characteristics of oil return system is put forward on the ground of analyzing the root of the oil back pressure. Mathematical optimization method is used to get key parameters of the impact oil cylinder.Secondly, structure and working principal of the flow distribution main control valve, the core component of the flow distribution system, are analyzed, the classical design formulas of valve component are introduced. The computational fluid dynamics model of flow distribution main control valve is build, and the best compromise result between least reversing resistance and minimum power loss is attained. The force of the valve is analyzed, the static and dynamic characteristics of the valve are studied, and the key parameters are attained.Thirdly, the characteristics of oil return system of flow distribution system are studied. The calculation method of the inflation pressure and initial volume of the oil return accumulator is deduced to enhance its filtering ability. The optimization method of hydraulic manifold block is introduced, damping coefficient and flow property of typical channel are analyzed. The oil return pipe models are introduced, and its performance is studied, the optimized results are attained ultimately.Then, the overall model of the pressure feedback flow distribution system is set up on the basis of sub-models of various components and key parameters are set. The influences to the performance of pile hammer on the change of the parameters of the flow distribution main control valve and the working parameters of flow distribution system, to the oil return pressure of different inflation pressure of the oil return accumulator, and the parameter selection principals are established.Finally, the correctness of theoretical analysis and simulation studies is verified by experimental results. And it provides guidance for the engineering application of the hydraulic pile hammer.