In petroleum industry, the stability of multiphase pumping is highly disturbed by the gas' presence with high content and variable working conditions. This paper is focused on studying the whole working cycle of the novel three-cylinder double-acting reciprocating multiphase pump. Based on the theoretical analysis, the method of computational fluid dynamics (CFD) is adopted to simulate the oil–gas flow in reciprocating multiphase pump. The numerical methodology, involving multiphase model, dynamic grid technique and user defined functions (UDF), is used to deal with in the calculation. The transient flow characteristics in pump cavity are obtained, and the flow ripples of reciprocating multiphase pump are analyzed. Furthermore, the effects of different operating parameters, such as suction and discharge pressures, inlet gas volume fraction (GVFi) on the capacity, and stability of pump, are studied. The results could help to develop and optimize the high-efficiency multiphase pump system.

Based on the governing equations of the unsteady flow of the power law fluid in the eccentric annuli with the inner cylinder reciprocating axially in bipolar coordinate system, the calculation formulae of normal force distribution on the wall of the inner cylinder of the power law fluid flowing in the eccentric annuli with the inner cylinder reciprocating axially in the bipolar coordinate system were established,and the relevant numerical calculation method was given.Taking the aqueous solution of partially hydrolyzed polyacrylamides (HPAM) for examples,the normal force distribution were calculated by using the calculation formulae and numerical calculation method mentioned above, the curves of the normal force distribution on the wall of the inner cylinder of HPAM aqueous solution were plotted and the effects on the normal force distribution of the flow behavior index of the power law fluid, the stroke and the stroke frequency of the inner cylinder were analyzed.

Relations between different parts are analyzed based on the structure of load-sensing swash plate piston pump. The models of piston pump and the servomechanism are set up by AMESim and connected with load-sensing steering system. The pressure and flow rate response under different rotation speed without priority valve is researched. The result shows such piston pump model can always response quickly and provide reasonable pressure and flow rate that fit the steering demands.

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