| Currently, the main method of the domestic tractor cooling system designed by experience is difficult to meet the increasingly complex requirements of modern bulldozers product design. Computational fluid dynamics (CFD) method can better analyze the inside changes of underhood temperature, flow rate, pressure and other physical quantities of the bulldozer. Based on the CFD method, this paper studies the bulldozer’s underhood thermal management, the establishment of a numerical model of the underhood and analyzes the CFD boundary conditions identification, solving strategy, the flow field and temperature field simulation and analysis, and makes the conclusion of that the surface temperature of the engine components is a litter higher and the fan is partial close to radiator. This findings can be used to guide the structural design and improved engineering practices as well as completed the experimental verification.Research work mainly includes the following aspects:A three-dimensional geometric model of bulldozer’s main components of the cooling system was established, the geometric model simplification of the engine block, air filter, after treatment and other components are completed; the precise geometry models of the fan, radiator and other key components the affect the thermal performance. Model import and meshing software using HyperMesh, which the fan and radiator is divided into small dimension meticulous grid with the grid in the form of unstructured tetrahedral grid cells.FLUENT is selected as a computational model solver, the boundary conditions are is corrected by prototype testing data using the κ-ε model when it is set. SIMPLE algorithm is used to solving the discrete fluid partial differential equations of flow and heat transfer underhood and complete numerical calculation. The simulation results are showed by speed and temperature gradient vector cloud graph.By combined analyze the calculation results and the product design parameter, and taking into account the implementation of improved engineering requirements, two key factors affecting the thermal performance are proposed:(1) high-temperature engine compartment unreasonable distribution areas, which leads to air temperature rise at the radiator inlet; (2) the distance between the fan and the radiator is too small, which resulting in fan turbulence and decrease the wind speed and cooling efficiency.After CFD simulation analysis for the problem, the rectifications to the engine compartment are:(1) the distance between the fan and the radiator is too small, which result in the disorder of the fan flow and decrease the wind speed and cooling efficiency; (2) there exist unreasonable high temperature distribution area in the underhood, this high temperature surface lead the air temperature raise of the radiator’s inlet.For the problem of CFD simulation analysis, the unerhood is certificated (1) replace the fan hydraulic motor with shorter axial dimension, increase the distance between the fan and the radiator to reduce fan turbulence and increase wind speed pass the radiator; (2) The heat insulation treatment of the exhaust pipe and the turbocharger is processed by aluminum foil insulation board to reduce the high-temperature thermal radiation inside the underhood and decrease the airflow temperature of the radiator inlet. And then, test and verify the vehicle after improvement, the LAT is 46.2℃, which is not only meet the design requirements of the cooling system, but also demonstrate the effectiveness of the paper method.This article adopts the CFD method to analyze and design improvement, which is a beneficial attempt. The result verified the effect of this method in optimization of the bulldozer thermal management system, which has certain engineering reference value in the future product research and develop. |
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