Performance Analysis And Optimizing Of A Marine Diesel Engine Air Passage Based On CFD

Z6170 diesel engine is a marine diesel engine developed by ZCE Power Co.?Ltd.in the nineties of the last century,occupying a large share in the market.Market research found that the diesel fuel economy become worse.Analysis of the reasons found that,due to the early cylinder head cast wood mold after long-term use of large deformation,resulting in late wood mold-based production of metal mold and design vary greatly,the intake and exhaust circulation efficiency is not ideal.Based on the above situation,in order to improve the overall performance of diesel engine,it is very necessary to evaluate and optimize the current intake and exhaust air passage of diesel engine.In this paper,the CFD calculation and testing methods are used to complete the performance analysis and optimization of Z6170 diesel engine intake and exhaust air passage.The main contents are as follows:The air steady flow test bench is used to measure the flow coefficient of the inlet and outlet air passage of the Z6170 diesel engine and the swirl ratio of the inlet air passage.The 3D model of inlet and exhaust air passage is drawn by Creo software.And then the AVL-Fire is used to do CFD calculation.The CFD calculation results and measured results are compared to verify the accuracy of the model.And the CFD calculation results are also used to determine the optimal direction of airway.Firstly,the airway model was optimized by using the 3D drawing software Creo,and then the AVL-Fire software was used to simulate and analyze the airway model's flow performance.The calculated results were compared with the original airway performance parameters.If the flow coefficient is improved,and then CNC machining methods is used to obtain the actual airway mold.Finally the blowing test is used to further verify the structural optimization of the airway flow performance improvement.If the result after one round of optimization does not meet the expected requirements,proceed to the next round of optimization as described above.After three rounds of optimization,the average inlet flow coefficient finally reached 0.3368,an increase of 14.21%,the average eddy current ratio reached 2.505,an increase of 11.28%.After two rounds of optimization,the resulting exhaust flow coefficient increased to 0.3910,an increase of 16.86%.The improved design of the cylinder head was made on the basis of the optimized inlet and exhaust air passage,and the comparison test was carried out on the diesel engine test bench to verify the airway optimization effect on the diesel fuel economy.The bench tests show that the fuel economy of the Z6170 diesel engine has been significantly improved when the air passage is optimized and the propulsion characteristics and low speed and high torque characteristics of the Z6170 diesel engine are improved.The fuel consumption rate is reduced by 8.5 g/(kW·h).