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This numerical study examines the chemical-kinetics mechanism responsible for EGR NOx reduction in standard engines. Also, it investigates the feasibility of using EGR alone in hydrogen-air and methanol-air combustion to help generate and retain the same radicals previously found to be responsible for the inducement of the autoignition (in such mixtures) in IC engines with the SONEX Combustion System (SCS) piston micro-chamber. The analysis is based on a detailed chemical kinetics mechanism (for each fuel) that includes NOx production. The mechanism for H-air-NOx combustion makes use of 19 species and 58 reactions while the methanol-air-NOx mechanism is based on the use of 49 species and 227 reactions. It was earlier postulated that the combination of thermal control and charge dilution provided by the EGR produces an alteration in the combustion mechanisms (for both the hydrogen and methanol cases) that lowers peak cycle temperatures-thus greatly reducing the production of NOx.

This study examines the novel use of a strong presence of radical ignition (RI) species to augment flame front propagation in a two-stroke spark ignition (SI) engine. Periphery mounted secondary chambers enable the generation of these RI species in one cycle for use in the next cycle. These chambers are outfitted to enable fuel-insertion and rapid heat addition. The new technology examined in the study employs the chemistry of homogeneous combustion radical ignition (HCRI) for the RI species enhancement of pre-mixed charge (PC) SI. The aim is to see if this chemistry can increase the lean burn threshold of this 2-stroke engine with natural gas (NG). The analysis uses experimental data together with a full chemical-kinetics simulation formulation that also accounts for thermo-chemical and hydro-dynamic exchanges that are both between the chambers and with the environment. The mechanism for the chemical kinetics consists of 97 chemical reactions involving 33 species.

A novel NOx reduction approach for 4-stroke direct-injection spark-ignition natural gas engines is examined. Secondary chambers are fitted into the cylinder peripheries as radical ignition (RI) species generation sites and equipped to enable fuel-insertion control and rapid heat addition. These chambers can thus regulate the production and transfer (into the main chamber) of RI species to augment combustion for reduced NOx and increased combustion stability. The analysis uses experimental data and full chemical-kinetics. The formulation governing equations are solved within multiple zones in both the secondary and main chambers, as the gas mixtures interact thermo-chemically and hydro-dynamically among themselves, with the internal cylinder boundaries and with the manifold (exchanging energy, momentum, mass and chemical species). Results suggest the potential of this technology for simultaneous NOx and CO reduction.

A preliminary study is made of the effectiveness of internally generated “Radical Ignition (RI) species” for NOx reduction in a NG (natural gas) Spark-Ignition (SI) 4-stroke test engine operating under lean fuel conditions at a typical SI compression ratio. The study includes both experimental and simulation analysis components. Investigated in this study is the potential for augmenting SI using a controlled presence of these RI species. The aim of their use is to lower the heat required for flame propagation under leaner than otherwise attainable fuel conditions. This lowers the NOx production. The primary generating site for these species is a set of passive mini-chambers located within the cylinder head. A modified single cylinder SI engine is used for the experimental studies.