CFD Analysis Of Cooling Fluid Flow Of Cooling Water Jacket In A Diesel Engine

Modern diesel engines use more efficient and clean combustion technology in response to the energy-saving and environment-protection requirements. Engine power is higher than ever, and the requirement of engine cooling system is higher consequently. In engine cooling system, the water jacket bears the important function of heat transfer. Three dimensional numerical simulation method has the advantages of low cost and short development period when used to study water jacket. CFD method is an important method in studying the performance of diesel engine water jacket and it can meet the challenge of short development circle caused by intense market competition. Nowadays, CFD method has become the basic research tool to study the performance of water cooling jacket in diesel engine industry. The following are the main work of this paper:(1) Before a CFD analysis was conducted, the parameters of some key points in water jacket are obtained by experiment method, such as flow, water pressure and water temperature. According to the test data and 3D numerical model, the study found that the flow of each cylinder is not uniform. The flow in the six right cylinders is higher than that in the six left cylinders. The flow in the cylinder head is relatively lower, flow dead zone exists in this area. The flow in the engine body is slow and there are some bad flow areas in the middle of the engine body. The original water jacket needs improvement.(2) According to the CFD analysis results, the original scheme was improved by increasing the water pump flow and optimizing the inlet structure of the water jacket inlet(the position of the inlet is upward and the direction of flow is tangent to the cylinder liner). The flow uniformity of each cylinder was improved after optimization. The maximum flow deviation was dropped to 15.95%. The coolant flow rate below the exhaust tube of the cylinder head water jacket was obviously increased to 2m·s-1. The coolant flow rate between the inlet and outlet valve seat was increased to 0.6m·s-1. The coolant flow rate in the bridge area, which is between the exhaust valve seat and spray nozzle, was increased to 1.2m·s-1, the flow rate in the middle area was increased to 2m·s-1. The flow rate in the upper areas of the engine body was over 0.5m·s-1, the flow rate was 1 m·s-1 in some areas.The areas at the bottom of the engine body, in which the flow rate reached 1 m·s-1, were increased. Near the inlet, the flow rate was reached to 0.8 m·s-1. The heat transfer coefficient of most areas in the middle of the engine body was over 3000W·(m2K)-1,especially in the upper area of the engine body, the heat transfer coefficient was raised from 1900~2000W·(m2K)-1to 3000W·(m2K)-1, and the areas, in which the flow rate was poor, were reduced.