Research On Traceability And Suppression Of Fluid Vibration In Hydraulic System Of Hydraulic Fracturing Truck

Fracturing truck is an important construction machinery in the petroleum industry.Traditional mechanical fracturing trucks are restricted by the manufacturing level of highpower engines and gearboxes,and their main components rely on imports.Hydraulic fracturing trucks have the advantages of being able to use several small-power engines for distributed drive,and can also adjust the fracturing flow without gear selection,which is approved by domestic market.However,a hydraulic fracturing vehicle has the problem of fluid vibration of hydraulic system.The pressure in high-pressure steel pipe fluctuates greatly,which will lead to fatigue damage of pipelines in the long run,thus causing safety accidents.Therefore,the problem of fluid vibration of hydraulic fracturing truck needs to be solved urgently.Based on the research on fluid vibration of hydraulic system and the method of fluid vibration reduction,this paper takes a hydraulic fracturing truck of a company as the research object to study the fluid vibration of hydraulic system of fracturing truck.According to the characteristics of under-damping of pump-controlled hydraulic system of multi-pump combined drive multi-motor of hydraulic fracturing truck,the transfer function of high pressure fluid vibration caused by periodic change of external load torque or periodic change of pump control system is derived and the resonance frequency at system level is calculated.According to the long high-pressure pipeline in hydraulic system,the pipe resonance is studied,the pressure transfer function in high-pressure steel pipe is calculated,and the resonance frequency of the pipe pressure wave is calculated.Calculate the excitation frequency one by one for the sources that may cause the fluid vibration of the hydraulic system,including the engine,pump,motor,fracturing pump,etc.Based on the analysis of resonance characteristics at system level and pipeline level,it is considered that the torque excitation generated by fracturing pump under flow conditions of 600 L/min is similar to the natural frequency of hydraulic system about 6 Hz,resulting in resonance of hydraulic system.Based on the experimental judgment,there is no obvious pipe resonance or selfexcited oscillation of the pump control system.It is considered that it is more suitable to use the accumulator to change the natural frequency of hydraulic system for fluid vibration reduction of fracturing truck by increasing the damping ratio of system through dynamic pressure feedback and changing the natural frequency of hydraulic system to avoid resonance.The natural frequency of the system can be moved from 6 Hz to 4 Hz,which can reduce the vibration of high pressure fluid by more than 60% under flow conditions of600 L/min.