Multi-dimensional Simulation And Experimental Study Of HCCI Combustion And Emissions In A DME Engine

With the energy crisis and environmental pollution of the world being more intensive, many countries pay more attention to the research of substitute fuels and combustion style of engine. Dimethyl Ether (DME) Homogeneous Charge Compression Ignition (HCCI) engine is widely researched because of its good ignition characteristic and very low emissions of NOx and soot. But there are some problems to be solved, such as reduced operating range, high HC and CO emissions and some unregulated emissions like formaldehyde.This paper researched the combustion and emissions forming progress of DME HCCI engine by numerical simulation and experimental methods. First, we built a reduced chemical kinetic model of DME which includes 31 species and 46 reactions, and built an engine's two-dimensional model. We completed numerical simulations of the combustion and emission characteristics of DME HCCI engine using CFD software Fluent coupled with reduced chemical kinetic model. By analysis of calculated results, the model is valid in calculating HCCI engine operations in a wide range of initial conditions, can predict species concentration profiles such as formaldehyde and formic acid, and also the NO emission. We analyzed the influence of some factors to the engine performance, such as intake temperature, intake pressure, equivalence ratio, compression ratio, speed and inert gas, predicted the in-cylinder concentration histories of the reactants, products and intermediate radicals.After lots of experiments, we optimized the operating conditions of gas chromatography, provided a method to measure the concentrations of unregulated emissions including formaldehyde and formic ether.