Methanol Hypergolic Combustion Kinetics (without N2) and Frozen Equilibrium in Radical-Ignition Reduced Compression Ratio D.I. Engines Using Piston Micro-Chambers

This study numerically examines the effects of select “radical species” on the hypergolic combustion of methanol fuel in a direct-injection (DI) naturally aspirated diesel engine at reduced compression ratios. These select radicals are generated via a set of micro-chambers (Figure 1) strategically placed within the piston at a location adjacent to the combustion bowl. Investigated are the effects of these radical species on the chemical-kinetics of main chamber autoignition. Also studied is the subsequent interactive radical generation processes and radical frozen equilibrium in both the micro and main chambers. In this new four-stroke numerical simulation, two open systems continuously interact, passing energy and chemical species between one another (through connecting vents) and with the manifold (via valves), while attempting to equalize pressure differences. The fuel is injected in such a way that the methanol enters the cylinder in a super-critical gas state and remains gaseous. The numerical simulation uses a detailed 84-reaction combustion mechanism involving 26 species. A comparison of this hypergolic radical ignition cycle simulation result is made with results obtained from two earlier radical ignition (RI) DI diesel engine experimental studies with liquid methanol fuel. The present work serves to provide veracity to the earlier RI experimental results and represents a significant incremental step toward the refinement and validation of a gaseous fuel RI simulation model. It also serves as another milestone in the development of an operational methanol DI diesel engine.