Cooling System’s Thermal Equilibrium Matching Underhood Structure Optimization Of Plateau Backhoe Loader

The cooling performance of engineering machinery is regarded as an important factor that has a strong influence on its power, economy and reliability. Foreign enterprises and research institutions have already begun studies on the underhood thermal management, and have made a number of new achievements. The research on the underhood thermal management of engineering machinery and competitiveness of products in domestic lag behind that of those industrial nation. In order to ensure the adequate cooling performance in harsh plateau environment as well as their working performance and service life, thermal equilibrium technologies of backhoe loader were discussed in this paper.Firstly, a cooling performance test of the backhoe loader cooling system was made. A set of experimental data was built through vehicle test which help analyze the thermal performance and verify the validity of the test. Through the experiment, the capacity of the cooling system is woefully inadequate, the heat balance buffer margin is insufficient which cannot suitable for plateau environment. The experiment dates provide an effective basis for the development and implementation of thermal equilibrium.Secondly, a method is proposed to obtain the Flowmaster V7software parameters based on real vehicle numerical analysis and developed a simulation engine thermal management model. Simulation was established to analyses the influence to engine cooling system. The matching optimization scheme was established. The results show that the cooling system cannot meet the demand in the altitude of4000m. Based on the orthogonal experiment, Inlet air temperature was the maximum factor to thermal equilibrium which should be improved by optimizing the structure of engine compartment and thermal equilibrium.Thirdly, focusing on the limitation of physical structure in1-D simulation and the shortage of convergence difficulty in3-D simulation, a method of multi-dimension coupled simulation and optimization was proposed.1-D fluid software and CFD software were coupled in this method to integrate the cooling system local complex fluid analysis and system calculation. By using1-D fluid software Flowmaster V7and CFD software ANSYS CFX, a cooling system structure model and finite element analysis model of underhood which model was built through iterative correction coupling simulation. Multiple underhood structure optimization schemes were proposed based on the influence of the cooling air temperature, cooling air mass flow rate and the underhood temperature in different structure. The solutions were evaluated by calculating the effect on the cooling system thermal equilibrium.Finally, aiming at improving the cooling performance, the exhaust ejector systems was used in the structure design. In order to obtain optimum performance parameters of the exhaust ejector system, the multi-objective optimization design method based on ejector coefficient and exhaust pressure difference was proposed. By using the platform of ANSYS Workbench, the design points were determined by the central composite design. According to CFX fluid dynamic software to numerical simulation in different design points, the response surface model was built in the response relationship of the input and output. The Pareto optimal solutions were produced by multi-objective genetic algorithm. Through the optimization, the results show the ejector coefficient and exhaust pressure difference were obviously improved. The multi objective provides a reference for the rapid design of enterprise optimization design method.