| Hydraulic technology is widely used in industry because of its high power density and high working parameters.The electro-hydraulic system is a hot point of research for hydraulic energy saving technology.Compared with traditional valve control system,it has such advantages as high efficiency,small volume,less components,etc.The axial piston pump is generally used in the electro-hydraulic system.The pump is regarded as the "heart" of the system,which determines the performance of the system.However,due to the structural reason of itself,the axial piston pump's performance is very difficult to be improved.Based on the National Natural Science Foundation of China project "Fundamental research on two-dimensional piston pump and electro-hydraulic technology”,a electric two-dimensional piston fuel pump is proposed to break structural limitations of tranditional piston pumps.This paper illustrates its advantages by comparing with the traditional axial piston pump,and studies its flow characteristics via theories and experiments.In order to study the flow characteristics of electric two-dimensional piston fuel pump,the structure and working principle are described detailedly and the mathematical model of leakage is established,furthermore,variation of flow rate is analyzed by analysis and numerical calculation.Moreover,the protyped pump is manufactured and tested.By contrast to the theoretical analysis,flow characteristics are studied deeply.Finally,as the key component of electro-hydraulic system,motor influences the flow characteristics of the pump seriously.This article proposes a new motor structure and relvant parametric design and experiment study are fulfilled.The main contents and achievements of this paper are as follows:(1)Compared with the axial piston pump,the electric two-dimensional piston fuel pump has the characteristics of high volume efficiency and power density.According to the motion law of the piston,based on the flow state of laminar,the leakage model of a single piston is proposed,and the mathematical model is improved by adding turbulence segment.Then the change rules of three kinds of leakage are analyzed and compared.Furthermore,the radial force in the piston is balanced,and thinner clearance is needed to keep a balance of heat,the clearance can be researched 3-4 ?m,the leakage flow is decreased.Also the variation of leakage flow trend to steady.In order to decrease the leakage flow in the critical position,different opening methods are analyzed.The results show that the distribution mode of negative opening can effectively reduce the leakage.(2)Using the lumped parameter method,the pressure characteristic equation in the piston chamber is established.Variation of pressure and flow rate is analyzed.The results show that the phenomenon of backflow occurs in the outlet port.And the periodic change of the discharge flow is caused by the differential pressure between the piston chamber and discharge port.In addition,the change of pressure and flow rate after adding dead angle and damping groove in the distribution window is analyzed.It shows that throttling with damping groove after switching between high and low pressure can restrain the phenomenon of oil backfilling,and different angles and widths of damping groove correspond to different working conditions.(3)Internal flow field model of two-dimensional piston pump is established by CFD adding compressibility and inertia of oil to consider the influence factors of flow fluctuation.The results of flow fluctuation under different rotational speeds and load pressures are studied.The flow without flow backfilling is compared.It indicates that the trough value of flow fluctuation is related to backfilling flow,and the peak value is related to pressure shock.(4)A three-phase high-speed reluctance motor used in two-dimensional piston pump is proposed.The oil is connected with the piston to cool the motor and improve the working time of the motor.The proposed motor is studied theoretically and experimentally.A helical rotor structure is proposed,which integrates the axially separated rotors.It is helpful to reduce the drag moment caused by oil entering the rotor.(5)A test bed is built to measure the flow characteristics of electric 2D tandem pump,the results show that the proposed pump has a high volumetric efficiency of 96%,low flow ripple of 6.3%.Moreover,electric 2D pump system is built to test.Also good performance is acquired.In summary,this paper makes theoretical and eperimental rsearch on two-dimensional piston pump,establishes the mathematical model of leakage,and analyses the variation law of leakage.The lumped parameter method and CFD model are used to further analyze the flow characteristics.Combining theory with experiment,the generation mechanism of flow fluctuation and corresponding optimization measures are obtained.In addition,a new type of three-phase high-speed reluctance motor is proposed,and its structural parametric design and experimental research are carried out. |
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