Numerical Simulation And Test Verification Of The Whole Process Of SCR System For Marine Low Speed Diesel Engine

In order to reduce the NO_X emission of atmospheric pollutants in ship exhaust and meet the NO_X emission requirements of the third stage of IMO,the application of SCR technology to reduce NO_X emissions from marine diesel engines has become one of the important means of ship pollution prevention.Foreign research on marine SCR systems has been for decades,and the technology has matured.Domestic research on marine SCR technology,especially simulation research,has just started.In this paper,the 6S35ME marine low-speed two-stroke diesel engine SCR system is taken as the research object,and the whole process operation state of the SCR system under E3 cycle condition is numerically simulated.The accuracy of the simulation results is verified by the bench test data.Optimize the simulation results and provide a design idea for the new model SCR mixing pipeline.The main research contents of this paper are:(1)Because the time scale of urea pyrolysis hydrolysis process and SCR reaction in SCR system is different,a numerical simulation method of three-dimensional one-dimensional coupling simulation is proposed in the simulation.This method can not only ensure the continuity of simulation results,but also enable SCR.The simulation of the mixing line and the reactor in the system is relatively independent.For example,when optimizing the mixing line,it is not necessary to reset the components of the reactor,and vice versa,reducing the number of repeated calculations in the numerical simulation process and shortening.The cycle of SCR system design and development.(2)In the test verification stage of 6S35ME marine low-speed two-stroke diesel engine SCR system,the test methods of spray test,catalyst sample test and bench test under E3 cycle condition were established.The test data and simulation results were compared.The reliability of the 3D and1D SCR simulation model was verified from the component to the whole,and the simulation error of the key parameters of the SCR system was within 5%.(3)Surface chemical reaction model optimization stage of the SCR system catalyst,the establishment of a system of one-dimensional model parameter optimization,of Explorer software algorithm,based on a sample test results of catalyst chemical reaction kinetics parameters optimized through Design,to optimize the value Instead of the empirical values integrated in the software,the one-dimensional SCR numerical simulation is closer to the actual reaction process;for the problem of uneven distribution of ammonia concentration before the cross section of the reactor,the SCR system optimization analysis method is summarized,and three possible SCR system reactions are summarized.The reason why the ammonia uniformity is too low before the device.The ammonia pipeline uniformity level of the SCR system reactor was used as the evaluation standard to comprehensively optimize the structure of the mixed pipeline.After optimization,the uniformity index was upgraded to 0.89.The analytical methods and optimization results in the optimization can provide theoretical guidance for the design and development of new SCR models.