Theoretical Analysis And Experiment For Four-port Hydraulic Transformer With Equal Flow At Inlet And Outlet

With the rapid development of the economy,energy supply is becoming increasingly tense,and energy conservation and environmental protection issues have attracted more and more attention.In the field of hydraulic transmission,improving the efficiency of hydraulic system and reducing the energy consumption has been the focus of research.As the existing integrated hydraulic transformer realizes the function of pressure transformation,the inlet and outlet flow also change,it is mainly used in constant pressure rail,and it is difficult to use it in existing valve control systems.In response to the above problems,the four-port hydraulic transformer with equal flow at inlet and outlet,which can be directly connected to the original hydraulic system,is proposed,it can recover differential pressure energy,braking energy and gravitational potential energy without changing the original hydraulic system.It provides an effective way to improve the efficiency of existing hydraulic systems,so it is of great significance to carry out research on four-port hydraulic transformers.Firstly,the structure composition,working principle and function of the four-port hydraulic transformer are introduced.The combination of port A and B is equivalent to a hydraulic motor,and the combination of port O and T is equivalent to a hydraulic pump,and the pressure ratio can be changed by adjusting the control angle of the valve plate.Based on the remaining compression force and torque method,the force and torque between the cylinder block and the valve plate are analyzed and calculated,and the structural parameters of the valve plate are determined.According to the function of four-port hydraulic transformer,the prototype is designed and prototyped.Secondly,the mathematical model of its transformation ratio,torque and efficiency was established,and the main factors affecting its transformation ratio and efficiency were obtained through analysis.When the control angle of the valve plate is constant,the transformation ratio will decrease as the cylinder speed increases or the recycling pressure difference decreases.The torque of each port is discontinuous,and the torque of each port beats twice in one rotation of the cylinder,and it varies with the control angle of valve plate,which is one of the main reasons for the unstable operation of hydraulic transformer.The total efficiency increases first and decreases afterwards with the increment of the cylinder speed,and increases with the control angle of valve plate,while decreases with the recycling pressure difference.Then,based on the AMESim software,the four-port hydraulic transformer simulation model is established.Combined with the actual operation rules of the four-port hydraulic transformer,the correctness of four-port hydraulic transformer model is verified.The flow characteristics of the four-port hydraulic transformer are simulated and studied.The results show that the characteristics of equal flow at the inlet and outlet of the four-port hydraulic transformer are not only independent of the control angle of the valve plate,but also independent of the load change outside the actuator.Finally,the four-port hydraulic transformer test-rig is designed and built in laboratory,which include hydraulic,electrical control and measurement and control systems.Based on the test-rig,the flow rate,pressure ratio and efficiency are studied,and the correctness of the theoretical and simulation results are verified,The research results not only lay a foundation for the further perfection of the theory of four-port hydraulic transformer,but also have important reference and guiding significance for its application.