Research On Combustion And Emissions Formation Of Hydrogen Enriched Natural Gas HCCI Engine

After the sixties of the last century, the world experienced three times'serious oil crisis.The global environmental resulted from the crisis severely affected the development of countries around the world. Energy, especially for the serious shortage of the oil resources and the deteriorating global environment have been regarded as the two difficulties around the world. To slove the problems, people pay more and more attention to the research on combustion innovative engine and alternative fuels. Hydrogen enriched natural gas is not only an alternative fuel meeting the demand of automobile developing "saving energy and reducing emission", but also act as feasible way to transform vehicle fule from conventional fuel to hydrogen gas. Good combustion and emission characteristics of HCNG engine are the focus of this thesis.Firstly this thesis summarizes the research trends, existent problems of Hydrogen enriched natural gas engines. According to the Gas Research Instiutte 3.0 natural gas detailed chemical kinetic mechanism of methane proposed by the University of California, this paper analyzes the natural gas detailed chemical kinetic mechanism by CHEMKIN. Based on the detailed chemical kinetics mechanism and existing simplified model, a new methane simplified chemical reaction mechanism is presented by sensitivity analysis and rate of production analysis. And then the comparative studies were given between the simplified model and the detailed model.The simulation results show that the simplified model can be used in place of the detailed model. It also can predict the variational courses of unregulated emissions such as formaldehyde, CO, NO and HC emission. The new simplified chemical kinetic model save more time for calculating, which provides a feasible way for the simulation of the chemical kinetics model coupled with the CFD multidimensional model.The paper plus hydrogen combustion mechanism based on the new methane simplified mechanism, then this thesis builds HCNG combustion reaction model. The model is extracted from the above two mechanisms that the chemical reaction rate constant isn't made changes.In theoretical part of the paper, the equations are carried out for computing H2/CNG ratio in mass, stoichiometric ratio, heat value of fuel-air mixture on various H2 fractions in volume and the content of each component of HCNG mixture. This paper builds a combustion chamber three-dimensional model made by ZS195 diesel engine.With the CNG and HCNG reduced model coupling with the CFD software FLUENT, then it calculates the combustion and emission characteristics of natural gas and Hydrogen enriched natural gas HCCI engine. Compared with CNG, it can be seen that as the hydrogen fractions increased, the temperature peak grow up, the combustion stabilize, the duration decrease, and emission temperature drop down, as the cylinder pressure peak grow up correspondingly. With increasing the hydrogen blend ratio, the NOx(mainly NO) and CO emissions increase, and HC(Methane),CH2O emission decreases respectively.