Research On Hydraulic Driving Technology Of Double-cycle Cooling System Of Wheel Loader

Loader is a kind of high-efficiency engineering machinery,widely used in mining,highway,port,coal and other engineering and urban construction sites.It plays an important role in reducing labor intensity and speeding up project construction.Therefore,in recent years,the loader has made great progress in performance and variety.The loader has a harsh working environment and complex working conditions,so it has very strict requirements on the performance and reliability of the cooling system.In the traditional cooling system of the loader,the fan is directly driven by the engine,and the fan and the engine maintain a fixed speed ratio change,which may cause the system to be too cold or too heat.With the continuous improvement of heat dissipation requirements of the loader and the national energy saving and emission reduction requirements,it is becoming increasingly important to develop a cooling system with high efficiency and low energy consumption.Based on the cooling system of a domestic 50-type wheel loader,a new type of double-cycle cooling system is designed in this paper.The hydraulic driving characteristics of the cooling system are studied through simulation analysis,the reliability of the simulation analysis is verified by the vehicle loader test.This paper mainly completes the following research work for the loader double-cycle cooling system:(1)Based on-NTU,the heat dissipation characteristics and pressure loss of the radiator are calculated.and those analysis shows :When the outside temperature is constant,increasing the cooling air flow can effectively enhance the heat dissipation effect,but the pressure loss on the air side of the radiator will become larger,and the fan shaft power requirement will be greater.Based on the cooling fan test data and related calculation formulas,the calculation formula of the fan speed and its various performance parameters are obtained,and the relationship between the cooling fan speed and the ambient temperature is derived.(2)The hydraulic driving of the double-cycle cooling system is studied.The working principle of the cooling system is introduced in detail,based on the originalcooling system,the parameters of the hydraulic components of the hydraulic drive of the double-cycle cooling system are recalculated and the model is selected.the cooling fan,hydraulic pump,hydraulic motor and electromagnetic proportional relief valve of the double-cycle cooling system are selected,the matching of the cooling module and the cooling fan was completed.The double-cycle cooling system is simulated with maximum heat load of the wheel loader and the extreme temperature conditions of-30 ℃ and 40 ℃.The hydraulic drive characteristics and energy-saving characteristics of the cooling system are analyzed.The results show the double-cycle cooling system can meet the heat dissipation requirements in extreme environments.In low temperature environments,the energy consumption of hydraulic drives is less than that of mechanical drives.When the environment is higher than a certain value,the energy consumption of the hydraulic drive is greater than that of the mechanical drive.Compared with the conventional hydraulic drive,the double-cycle hydraulic drive has increased energy consumption due to excessive leakage.(3)The hydraulic driving characteristics of the double-cycle cooling system is analyzed from different angles.When the engine speed is different,the hydraulic drive characteristics of the double-cycle cooling system is analyzed;When the inlet temperature of the hydraulic pump is different,the effect of different coolant temperatures on the hydraulic drive characteristics of the double-cycle cooling system is analyzed;When the coolant is used as the driving medium of the hydraulic system,the hydraulic driving characteristics of the double-cycle cooling system are analyzed from the perspective of volume efficiency and displacement of the hydraulic pump:First,discuss the effect of different volumetric efficiency of hydraulic pump on hydraulic drive under certain pump and motor displacement,then analyze the effect of different pump displacement on hydraulic drive under certain volumetric efficiency of hydraulic pump.(4)The field test process of the double-cycle cooling system of the wheel loader is introduced.It mainly introduces the test equipment and the location of each measuring point,and sorts out the test data to get the relevant parameter curve graph of the loader thermal balance,and the heat dissipation performance of the double-cycle cooling system is analyzed.