Study On Combustion And Emission Characteristics Of Hydrogen Under Thermal EGR

Hydrogen is a kind of clean and renewable energy,but during the combustion of hydrogen in an internal combustion engine will produce large amounts of NOx emissions,how to reduce or even eliminate the NOx emission is a key issue in the current research of hydrogen internal combustion engine.The paper through simulation and experiment method studied hydroxyl distribution of combustion process of hydrogen in a constant volume combustion bomb,thus the combustion and emission characteristics of the hydrogen combustion are studied from the mechanism,provides theoretical guidance and support for reduce the NOx emission of hydrogen internal combustion engine.The premixed combustion process of hydrogen air mixture was simulated by using CHEMKIN software,the simulation calculation of hydrogen air premixed combustion was carried out,the combustion characteristics and the formation of the base are analyzed and the rule of formation of NO and the influence of cold and hot EGR on the combustion and emission of hydrogen were analyzed.The prediction and analysis of the formation law of the base and NO were carried out,it is proved that EGR has a significant effect on the inhibition of the burning rate,the reduction of the free radicals and the generation rate and concentration of NO.The simulation results provide theoretical guidance for the experiment.A planar laser induced fluorescence test platform is set up,the hydroxyl were tested by OH-PLIF method,the hydroxyl distribution images of different timing,different concentration,different temperature,different pressure,different cold EGR rate and thermal EGR rate were obtained.It is proved that increase concentration and temperature would promote the formation of hydroxyl groups,The effect of increasing pressure on the formation of hydroxyl group is more complicated,but it also has a tendency to promote.EGR,especially hot EGR,can significantly inhibit the formation of hydroxyl groups,the EGR can effectively inhibit combustion and reduce the emission of nitrogen oxides,the effect of thermal EGR is stronger.The experimental results are in agreement with the simulation results.The results of experiments and simulations show that the thermal EGR has a significant effect on the reduction of NOx emission and combustion.