Research On Emission Control And Online Monitoring Of In-Use Diesel Engines

The invention and wide application of diesel engines have made important contributions to the civilization and economic development of human beings,while the environmental pollution brought should not be ignored.Brown gas composed of H₂ and O₂has excellent cleaning effect,not only can effectively improve the combustion and particulate emissions of diesel engines at the same time,but also is an ideal added fuel to suppress the soot emissions of diesel engines in use.In order to clarify the proper blending amount and specific effects of brown gas used in diesel engine emission control,a simulation study was carried out in this paper,and the chemical reaction kinetics mechanism of diesel blended brown gas was developed.Based on which a numerical simulation was applied to quantitatively analyze the effect of brown gas addition on diesel combustion and emissions under different operating conditions,which could provide a theoretical basis and quantitative reference for the determination of brown gas production in the exploitation of brown gas generators for diesel engines in use.In addition,this paper aimed at the difficulty to curb the excessive NOx emissions of national IV and above diesel vehicles in use caused by human factors such as no addition of vehicle urea or the neglect of post-processing system failures only through annual inspections and road inspection.An online monitoring system for NOx emissions based on OBD has been initially constructed.After networking with environmental protection departments,which can provide powerful help for further implementation of emission regulations and protection of the atmospheric environment.The specific research contents and main conclusions of this paper are as follows:1.The decoupling method was used to construct the oxidation mechanism of diesel with brown gas.The detailed mechanism of NUI hydrogen oxidation was selected for the part of brown gas,while diesel was characterized by n-heptane,and its reaction mechanism adopted ERC n-heptane skeleton.Finally,the chemical kinetic mechanism of diesel blended brown gas containing 32 components and 88 reaction steps was obtained and the accuracy of the mechanism was verified.2.Based on the above mechanism,a three-dimensional working process model of the diesel engine was established and the effect of the amount of brown gas adjunction on the diesel engine under two different operating conditions was studied.Results show that the brown gas at 2 L/min has the best comprehensive optimization effect on engine emissions under rated conditions.At this time,CO and soot emissions reached the lowest level,which decreased by 8.0%and 8.1%compared to the original emission data;after adding 5 L/min of Brown gas,the overall emissions of the engine have the most obvious improvements at the maximum torque conditions,THC,CO,and soot emissions decreased respectively by21.9%,20.5%,and 17.1%.According to the calculation results of the numerical simulation and the limitation of electrical power consumed by the brown gas generator,the addition of brown gas for in-use diesel engine emission control should be 2 L/min.3.An on-line monitoring system for NOx emissions of diesel engines in use based on OBD has been developed.This system uses data as the center to build a three-tier structure that includes data collection,transmission,and platform output.Relevant vehicles with excessive NOx emissions caused by abnormal SCR operation will be prompted and recorded,accordingly,the online monitoring of NOx emissions for in-use diesel engines has been achieved.