Analysis Of Cooling Water Flow Characteristics Of Non - Road High Pressure Common Rail Diesel Engine

The engine heat load is generally expressed by the stress and strain or loss of the relative parameters such as the higher temperature of metal, the temperature gradient of the metal, etc. However the purpose of cooling is to maintain the engine parts of the metal temperature and the temperature gradient at a suitable level. But, high thermal load will lead to higher strength of the engine parts. There will be a lot of durability problems, such as cracks in the cylinder head and exhaust pipe, as well as damage to the turbine rotor. Therefore, the high requirement for engine cooling system is put forward. In addition, with the emergence of the crisis of energy and environment, in order to meet stringent emissions regulations and improve of the engine economy, also higher requirement for engine cooling system is put forward. So, the management of thermal load has become a major challenge in the design of modern turbocharged engine. For this, this paper researched a non-road high pressure common rail diesel engine cooling system, combined with the engine thermal balance test, using the one-dimensional and three-dimensional co-simulation method to simulate engine cooling system.(1) The boundary conditions of the calculation model are obtained by using the heat balance bench test of the engine, and the correctness of the one dimensional simulation model is verified. Through the thermal balance test for engine under the rated condition and the maximum torque condition, the engine inlet and outlet water temperature and the flow of the coolant were measured, and the heat of the coolant is calculated, the rationality of the matching of cooling system is evaluated, and the design basis is provided for the matching of whole cooling system.(2) Combined with the actual working state of engine, one-dimensional model of the engine cooling system is established by using one-dimensional GT-COOL software. The temperature field and the flow field of engine cooling system are studied under the rated point and the maximum torque point, and compared with the experiment. And the influence of pump flow rate, fan parameters and the positive area of the radiator on the temperature and the temperature difference between the inlet and outlet of the engine are analyzed.(3) Through the one dimensional simulation, the boundary conditions are obtained. The cooling water jacket of engine temperature field, flow field and pressure field are analyzed by using 3D software AVL fire, and the improvement scheme are put forward on the basis of CFD of the engine cooling water jacket. From the results of CFD analysis, the engine water jacket basically met the cooling requirements, the cooling water jacket existed no uniformity flow, smaller flow velocity is appeared, even swirl on the exhaust side of the cylinder, the upper part of the body water jacket is formed low stagnation zone, the regional water jacket cooling water jacket of fourth cylinder engine cylinder is appeared weak flow velocity. From the analysis of the nose area of cylinder head, except the first cylinder of the nose area meet the cooling requirements, the other cylinder nose area have not reached cooling requirements, and even low.(4) Based on orthogonal design method, the cooling water jacket is optimized. The orthogonal calculation scheme of cooling water jacket is built by using orthogonal design method. Then the optimum design of cooling water jacket structure is gotten finally. The results show that the optimal scheme can improve the cooling effect for the whole engine. Among them, the average velocity and the heat transfer coefficient of the water jacket than the original scheme were increased by 13.1%,5.4%. The average velocity and the heat transfer coefficient of the engine block water jacket were improved, numerical values are 17.3%,15%. The average velocity and heat transfer coefficient of engine head water jacket is increased, numerical values are 9.5%,12.6%. The average velocity of the nose region than the original scheme is increased by 18%. The average velocity of the cylinder liner is increased by 16.1%, compared with the original scheme.