| The loader,as one of the most commonly used construction machinery,plays an important role in the construction of the project.With the continuous progress of technology and the need of project,and at the same time affected by the national energy saving,emission reduction and increasingly stringent emission standards,the loader cooling system is facing many problems,such as high energy consumption and insufficient cooling capacity.How to design the radiator structure with small resistance characteristics and high heat transfer capacity,and how to design a cooling system with high cooling performance has become the focus of researchers.In this paper,a new type of double-circulation cooling system for loaders is taken as the research object.The original cooling system of a 50-type loader is used as the comparative analysis object.According to enhanced heat transfer theory,the heat dissipation characteristics of the two cooling systems are studied and analyzed on the base of numerical simulation.Combined with the vehicle cooling system test of the loader,the feasibility and accuracy of the numerical analysis method are verified.This article focuses on the following research work for the loader cooling system:(1)In this paper,two kinds of cooling systems are compared and analyzed.All the radiator in the cooling system adopt a plate-fin structure.According to the theory of heat transfer,the heat transfer mechanism of the fins in the plate-fin radiator is described.Take the example of the serrated fin and Wavy fin in the charge air coolers of two cooling system engines.The simulation analysis of two kinds of charge air cooler fins is carried out,the temperature field,pressure field and velocity field inside the cold side fin unit body of the two charge air coolers are discussed and discussed in detail.According to the simulation results of the fins on the hot and cold sides,the curve of the fin pressure drop with the flow velocity was fitted,in this way,porous media parameters of porous media model are obtained.The main structural parameters of the serrated and corrugated fins are studied.The changes in the heat transfer and resistance characteristics of the serrated fin and wavy fin are analyzed under different structural parameters.(2)The porous medium model is applied to simulate the model of the charge air coolers in the two cooling systems,and analyze the internal flow field distribution state of them.The formula for the total pressure loss of the pressurized air is derived to analyze the pressure change of pressurized air,analyze the pressure drop of the charge air in the two charge air coolers at different engine speeds,and the pressure drop of charge air at various parts of flow channel under the maximum speed of the engine is given.Through calculation,at the maximum engine speed,the pressure loss of the pressurized air of the water-cooled charge air cooler is 4.78 kPa lower than that of the air-cooled charge air cooler.Through the analysis of the flow state of the pressurized air in the circuit,the calculation formula for the time required for the charge air to flow in the cooling circuit is derived and the process hysteresis effect of pressurized air in the loop is compared and analyzed.The optimal design of the water-cooled charge air cooler is carried out,and the flow patterns of the cold side flow path and the core structure of the water-cooled charge air cooler are optimized.After optimization,the pressure loss on the cold side of the water-cooled charge air cooler decreased by 33.01%,and the pressure loss on the hot side decreased by 55.71%.(3)According to the structure of the loader vehicle,the power cabin model of the original vehicle cooling system and the double-cycle cooling system was established.The characteristics of the temperature field,pressure field and velocity field of the two cooling systems in the power cabin are compared and studied.Through analysis,it is found that the temperature and pressure distribution on the windward surface of the double-circulation cooling system is more uniform,the heat dissipation capacity is stronger,the resistance coefficient is smaller,and the air flow rate in the power cabin is greater.In order to further improve the cooling effect of the cooling system,the compartment partition of the double-cycle cooling system is analyzed and the design of the air intake hole of the power cabin is based on the distribution of the velocity field in the openable area of the power cabin.The results show that after the partition treatment,the total cooling capacity of the double-cycle cooling system has increased by 11.12%.(4)The field test and test equipment for two cooling systems of loaders are introduced,and the test data of each radiator when heat balance is given.By analyzing the performance of the cooling system,it is found that the double-cycle cooling system has more heat dissipation than the original cooling system.Under the same cooling conditions,the double-cycle cooling system requires less power consumption.Compared with the original cooling system,the double-cycle cooling system efficiency is increased by 16.16%. |
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