Study On Dynamic Characteristic And Thermal Balance Of Hydraulic System For 50-type Loader

Hydraulic system is an important part of the loader. When we research the dynamic characteristics, energy-saving improvements and thermal balance of the hydraulic system, we should know the system flow and pressure and other characteristics of hydraulic fluid. Because the loader has varied duty and each duty include more action, the hydraulic system flow and pressure of each action are different. If we want to know the variation of internal system parameter, we should rely on previous trial method. But the trial must be based on physical prototype that have main structure parameter and processed a product. If we have known the performance of hydraulic system in product development phase, we will greatly shorten the development cycle and reduce costs.The vehicle emissions standards will increasingly strict in future, traditional contrution machinery is facing the serious challenges. Thermal balance problems show in the form of temperature. The researchers are trying to increase the cooling efficiency control the temperature in the reasonable scope. The researchers take some method to increase the cooling efficiency, such as increasing radiator area, improving fan speed or increasing the fan diameter, but the heat generating and dissipating principles of hydraulic system are often be overlooked, thus lead to the problem cannot be solved fundamentally. From the view of energy conservation, reduce the quantity of redundant and harmful heat, only in this way can solve the problem fundamentally. This means energy saving.In this paper we investigate the 50-type loader, based on a typical working condition, in order to reduce the hydraulic system power loss, improve the efficiency of the hydraulic system, control the hydraulic system oil temperature within the allowable scope of work。First an AMESim model and a RC network heat transfer simulation model of hydraulic system for a loader are presented, Through the experiments to verify the effectiveness of models, Study on dynamic characteristic and thermal balance of hydraulic system for Loader base on models, calculation and analysis the power loss of loader hydraulic system, while working in the I-shaped shovel test conditions; Study on the thermal balance of hydraulic system base on the different hydraulic steering system configurations and different operating conditions, and it gives the corresponding evaluation。Build the simulation model of loader operation mechanism hydraulic system based on AMESimThe simulation model of loader working device and its hydraulic system respectively was built with the Mechanical library and Hydraulic library of software AMESim. Hydraulic-mechanical coupling simulation analysis was researched according to the typical movements of loader operation mechanism. The experiment data shows that the simulation model can reflect the dynamic characteristics of hydraulic system. The multiple valve, priority valve and preferred unloading valve model was established. The simulation analysis of double pump confluence performance for the loaders I condition proof that the preferred unloading valve has certain energy-saving effect. The simulation analysis of loader typical I working condition was completed, the simulation results show the hydraulic system efficiency in loader shovels assignments is 35.7%.Establish the RC network heat transfer model of loader hydraulic systemThe RC network simulation model of describing the loader hydraulic system global, system modular heat balance was proposed first. The model used lumped parameter model and based the heat capacity lumped in domestic method, aiming at the problem of overheating in hydraulic system. The loader hydraulic system was divided into 18 flow node and five surface heat transfer node, the above nodes were defined as 23 first-order ordinary differential equations, and the nodes between node and environment were defined as the thermal resistance. The differential equations was solved used MATLAB, transient and steady state thermal simulation of hydraulic system was completed with this model. The analysis between heat balance simulation and experimental of shovels circulation and high-speed in I test condition proved this model can be applied to the loader hydraulic system thermal balanceanalysis. Simulation results show that the hydraulic system is a high-pressure overflow condition, hydraulic oil temperature lifts quickly about 9℃in the loaders I shovels cycle experimental condition from bucket uninstall to arm down about 1-2 seconds time. The modeling method of heat transfer model for loader hydraulic system can be applied to the loader engine cooling system, lubricating system and vehicle transmission system in thermal characteristic analysis work.Analyse the thermal balanceof different hydraulic system configuration and different operation modes used heat transfer model of loaderThe balanced temperature of hydraulic system in different configuration and different operation way for loader was calculated firstly. The thermal balance temperature of the typical I,V,L,T operation method was simulated with RC network model of loader hydraulic system. The calculation results show:the heat load of loader hydraulic system in I shovels condition used generally in domestic enterprises at present is not the maximum condition; Coaxial flow amplification steering hydraulic system achieved the highest thermal balancetemperature in T-shaped operation condition; Configuration flow amplification steering hydraulic system achieved the highest thermal balancetemperature in V-shaped operation condition; The flow amplification steering hydraulic system can save 58.8% energy in steering alone, save 15.3% energy in complex movement compared with enlarge coaxial flow to hydraulic system.Complete dynamic characteristic and heat balance experiment of loader hydraulic system in typical working conditionsThe multi-channel test and reservoir system and heat balance measuring system of loader hydraulic system was developed. The pressure, flow and temperature variations for hydraulic system and flow, temperature of thermal fluid and wind speed, air pressure and air temperature of cooling fluid for the hydraulic oil can be detected in real-time. The test used advanced multi-channel data collector in loader typical working conditions experiment.Puts forward the corresponding improvement plan for different configuration of the loader hydraulic systemThe improvement plans for overheating problem of the 50 loader hydraulic system was presented.1,Increase priority unloading valve to hydraulic system; 2,Change the layouts of hydraulic oil cooler tubing road; 3,Change the layout structure of loader steering hydraulic system return pipe road. The above improvement plans was simulated based on the thermal balance RC network simulation model of loader hydraulic system. The simulation and experiment results demonstrate the scheme is feasible and the thermal balance RC network simulation model of hydraulic system can be applied to the loader design.