Study On Thermal Balance Of Hydraulic System Of Large Hydraulic Excavator

Hydraulic excavators are the most widely used construction machinery equipment in mining engineering construction,mainly used for high-intensity operations such as all kinds of earth excavation.As the main transmission and control system of hydraulic excavators,hydraulic system has energy loss.Most of the lost energy is absorbed by hydraulic oil and hydraulic components in the form of heat energy,which causes the temperature of hydraulic oil and hydraulic components to rise and accelerate.The performance of hydraulic oil deteriorates,which leads to an increase in system leakage,which in turn reduces work efficiency.Due to the poor working environment of the excavator and the continuity of work,the thermal balance of the hydraulic system has become an important factor restricting the working efficiency of the hydraulic excavator,and the reasonable matching of the cooling capacity of the hydraulic system is particularly important.The traditional design method is to perform thermal balance test and verification after the selected cooling system is installed,which often leads to more rework,which seriously affects the development efficiency and development cycle of the cooling system.In response to the above problems,this article is funded by the NSFC-Shanxi Coal-based Low-Carbon Joint Fund Project(U1510206),through the method of multidisciplinary cosimulation modeling of machine,liquid and heat,to study the thermal balance characteristics of the hydraulic system of hydraulic excavators to reduce the test cost,shorten the cooling system development cycle.On this basis,the heat balance characteristics of the hydraulic system of the hydraulic excavator are deeply studied.The specific work is as follows.First,based on the basic theory of thermodynamics,a mathematical model of the thermal characteristics of hydraulic components is established based on the principles of conservation of mass and energy.The control body method is used to derive the temperature change equation of the oil in the main hydraulic components.The heating and heat dissipation characteristics of hydraulic components are theoretically analyzed.The thermal balance of the hydraulic system is estimated.Secondly,analyze the working principle and control strategy of the hydraulic excavator prototype.Based on the physical structure and parameters,the hydraulic excavator mechanical structure model,hydraulic system model and heat exchange model are established.Then,the mechanical,hydraulic and heat transfer models are coupled in the Simulation X simulation platform.Establish a multidisciplinary simulation model of machine,liquid and heat.Then compare with the prototype test results to verify the correctness of the simulation model.Using the established multi-disciplinary simulation model,it focuses on analyzing the thermal balance characteristics of the hydraulic system under typical working cycle conditions.Through simulation,the heat production and heat dissipation characteristics of each hydraulic component in the working cycle,the change law of heat production at each working stage,and the temperature change of the main hydraulic components are obtained.Among the components,the valve group components account for up to 65% of the heat generation,and the radiator’s heat output accounts for about 80%.The higher the ambient temperature,the higher the heat balance temperature of the excavator.Through the analysis of the above modeling and simulation results,the simulation model can provide guidance for the cooling power matching of the hydraulic system of the hydraulic excavator.Thereby improving the development efficiency of the cooling system and shortening the development cycle.