Research On Performance And Application Of High-power Hydrodynamic Torque Converter With Square Cavity

With the rapid development of China's economy and the sharp shortage of oil,natural gas and other energy,the large-scale exploitation of shale gas is imperative.The fracturing truck is an important fracturing equipment for producing shale gas,whose application and development concern are widely concerned.Hydrodynamic power transmission system is commonly used in power transmission of current fracturing truck,and hydrodynamic torque converter is an important component of the hydrodynamic transmission system.The performance of hydrodynamic torque converter and the matching between engine and hydrodynamic torque converter are the key factors to affect the performance of fracturing truck.At present,the hydrodynamic torque converter which is used in the fracturing truck is mostly the centripetal turbine torque converter.The centripetal turbine torque converter has a great change in the torque coefficient of impeller and a large positive permeability,which makes the speed and torque of engine change largely with the load pressure changes,when the fracturing truck operates in the torque condition.And it results that the fracturing truck can't work stably in the high efficiency area.However,the square cavity hydrodynamic torque converter can make full use of the engine's power and improve the work efficiency of the whole machine,because the torque coefficient of impeller of square cavity hydrodynamic torque converter changes lightly.Based on that,this paper takes a certain type of fracturing truck as the application object,designs a high-power square cavity hydrodynamic torque converter,and studies its performance and application to the fracturing truck.The main research contents and conclusions are as follows.(1)The original parameters of reference prototype were calculated using CFD method under the conditions of setting pressure boundary and neglecting pressureboundary.The calculation result was compared with the experimental data to obtain that setting pressure boundary was the accurate method to predict the performance of square cavity hydrodynamic torque converter.Similar-design method was adopted to design the circulating circle of high-power square cavity hydrodynamic torque converter,whose effective diameter was 705 mm.The blades of pump,turbine and stator of the torque converter were designed by conformal mapping method.Based on setting pressure boundary method,the numerical simulation of the newly designed high-power square cavity hydrodynamic torque converter was carried out.The velocity and pressure distribution of the internal flow field were analyzed,and the performance of high-power square cavity hydrodynamic torque converter was predicted.(2)The mathematical models of engine and high-power square cavity hydrodynamic torque converter were established respectively.The static matching calculation between the engine and high-power square cavity hydrodynamic torque converter was carried out,and the common working input characteristics,working output characteristics and the range of the rotational speed of the common working point were obtained and analyzed.At the same time,the output characteristics of the transmission under common working condition are calculated,which established the foundation for the joint output characteristic calculation of the power transmission system.(3)The structure parameters and characteristics of the fracturing pump were analyzed.Based on the common work output characteristics between the engine and high-power square cavity hydrodynamic torque converter,the joint output flow and pressure of the fracturing truck which used the high-power square cavity hydrodynamic torque converter were calculated by combining with the parameters of transmission and fracturing pump.The joint output characteristic curve of the transmission system was plotted and analyzed,and it was concluded that the combined output flow and pressure met the requirements of the fracturing construction technology.Then,based on the measured data which was obtained when a certain type of fracturing truck fractured in a well,a dynamic matching simulationmodel of the transmission system was stablished by MATLAB/Simulink.By comparing the joint output flow of fracturing power transmission system and driving power of fracturing pump that before and after using the high-power square cavity hydrodynamic torque converter,it was concluded that the dynamic performance of fracturing truck was improved after using the high-power square cavity hydrodynamic torque converter.Through the analysis of the dynamic matching engine's fuel consumption ratio and amount of fuel consumption,it was concluded that the fracturing truck which used high-power square cavity hydrodynamic torque converter had better economic efficiency.In addition,the efficiency of torque converter was analyzed,and it was proved that the matching between the designed high-power square cavity hydrodynamic torque converter,the engine and the fracturing pump was suitable.