Research On Key Techniques Of Independent Temperature Control Cooling System For Construction Vehicle

The construction vehicle thermal management technology that as one of the key technologies of vehicle development in the 21 st century plays an important role in improving the performance, energy conservation and emissions reduction. Engineering machinery as a road vehicle has more stringent performance requirements for thermal management system due to special working environment and working conditions. Because of the implementation of stage Ⅲ emission regulation for construction machinery at present, the heat load of the cooling module increases accordingly. The research on thermal management system put forward more severe challenges.So a detailed in-depth study of the thermal management system has important application value and theoretical significance.At present, the study of the domestic loader manufacturer for the thermal management system for lags far behind Europe and the United States and there is a big gap with foreign products in such aspects as working stability and energy conservation. Based on the project in the National Science & Technology Pillar Program during the Twelfth Five-year Plan Period, "Intelligent Construction Machinery Design for Energy Conservation and Safety", aiming to improve performance of the vehicle cooling system, guarantee the stability of work and improve fuel economy, and achieve the goal of energy conservation and emissions reduction,the thorough research on radiator, engine cabin thermal environment, thermal characteristics of the hydraulic system and independent cooling tank structure and independent cooling system of stage Ⅲ loader by using three-dimensional CFD simulation and one dimensional thermodynamic performance simulation system.The main contents of the thesis on the study of loader cooling system are as follows:(1)Describes the heat transfer mechanism of plate-fin radiator based on heat transfer and fluid mechanics principle. Multi-objective optimizations were carried out based on genetic algorithm on liquid-cooled oil cooler and intercooler. Choose the optimal results according to the cooling requirement. Fluid-solid coupled heat transfer simulation was carried out using the CFD numerical method. The bench test for the intercooler was also performed. The influence of coolant parameters on radiator performance was analyzed. The basic research about the enhanced heat transfer performance was conducted based on the field synergy principle. The strengthening heat transfer characteristics of triangle spoiler for the corrugated fin were simulated. And the heat transfer effects of spoiler under different structural parameters were evaluated.Research results show that the disturbed flow wing is helpful to improve the heat dissipation performance.(2) Heat transfer mechanism was expounded for a wheel loader. Thermal environment was simulated with three-dimensional CFD simulation in a virtual wind tunnel. The influence of the high temperature heat source on thermal environment and the cooling fan inlet temperature was predicted. Flow field and temperature field were obtained when the fan was both forward and reverse rotation. The mathematical model as the performance for cooling air distribution uniformity of the radiator was deduced and provide a theoretical basis for the optimization of the fan blade and design of the radiator. The heat exchange performance of the radiator was analyzed with coupling simulation under different ambient temperature. The study result provides guidance for the engineering cabin structure improvement and cooling system optimization.(3) Based on work device hydraulic system, work device dynamics simulation model and thydraulic system simulation model were established and Co-Simulation was carried out. The produce heat and heat dissipation mechanism of hydraulic system were expounded. Simulation result was compared with the experimental data to verify the correctness of the model. The dynamic characteristics and thermal properties of the hydraulic system were analyzed. The influence of the environment temperature heat balance of the hydraulic system was simulated. The opening pressure of hydraulic loop back pressure valve was optimized.(4)Describes the composition and working principle of a new independent cooling system. Cooling fan, hydraulic motor, hydraulic pump and electro-hydraulic proportional relief valve parameters were matched and selected. The mathematical model of proportional valve was deduced. One-dimensional simulation model of the independent cooling system was built. The fuzzy logic control strategy was made. Dynamic characteristics and heat exchange performance under different ambient temperature of the independent cooling system were analyzed. Energy saving characteristics of the new cooling system were evaluated. The simulation results show that the new independent temperature control has better heat dissipation performance and energy saving features.(5)In order to reduce the air temperature of the cooling module and increase the amount of intake air of fan,three-dimensional CFD analysis was used to analyz the different structure of the independent including cooling fan front and rear,blowing and suction type. The influence of distance between the fan and radiator on the air flow was analyzed. The air flow rate and heat power of the different structure were compared and the best structure scheme was choosed. The results provide reference for the structure optimization of thermal management system.(6)The prototype machine for loader working conditions and driving conditions were tested. The thermal balance test results under different working conditions were obtained.It is found that heat dissipation of the existing cooling system is lower and thermal equilibrium temperature are higher. The bench test results of the new cooling system show that the vehicle thermal equilibrium has been significantly improved. By comparing one-dimensional simulation model is verified the accuracy and the feasibility of the optimized scheme.