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Numerical examination is made of the use of methane in a direct-injection (DI) radial-ignition (RI) diesel rotary-combustion engine (RCE) while operating under ultra-lean fuel conditions at low compression ratios (CR's). The simulated engine is operated with the help of five percent hydrogen as a pilot. Homogeneous combustion under such conditions is made possible by radical species produced in periphery-mounted secondary chambers. The bulk of the mass of the radical species generated by these chambers is used in the subsequent cycle to initiate and control main chamber autoignition. One goal is to see whether DI-RI alone can substantially extend the lean-burn region of this engine to enable low-heat rejection high-power density operations with low NOx emissions. A detailed examination is made of the effects of internally generated “radicals” on methane combustion chemistry in the RCE.

This work represents an extension of the homogeneous combustion radical ignition (HCRI) process to a two-stroke direct injection (DI) diesel engine operated at normal diesel compression ratios (CR's). As in four-stroke DI-HCRI diesel engine variants, this engine has periphery mounted secondary radical generation chambers (mini-chambers ) that enable control of the radical generation process. One goal of this study is to see whether the use of HCRI alone can extend the lean burn region of the two-stroke DI engine to enable low NOx operations with hydrogen at such CR's. To this end, a detailed examination is made of the effects of internally generated “radicals” on the chemical-kinetics of the two-stroke radical ignition (RI) diesel cycle. The starting point for this simulation is a modified variant of the well corroborated formulation used in the earlier hydrogen four-stroke studies.

This study explores the potential for ethanol use in the DI-HCRI (direct-injection homogeneous-combustion radical-ignition) diesel engine with its periphery-mounted secondary radical-generation chambers (mini-chambers). The aim of this simulation study is to determine whether HCRI alone can extend the lean burn region of this four-stroke ethanol engine to include low NOx operations at normal diesel compression ratios. The simulation employs a highly modified variant of an earlier single-phase full-kinetics formulation and a new chemical-kinetics mechanism with 57 species and 371 reactions. The fuel is injected in the liquid phase within both of the separate-but-connected open systems representing the main and mini chambers. Thus a droplet spray model is included in this full chemical-kinetics formulation to account for the vaporization and mixing of the liquid fuel in both chambers.

This paper examines the use of radial ignition (RI) at much lower than normal diesel compression ratios (CR's) in a novel direct-injection (DI) diesel rotary-combustion engine (RCE). Unique to this engine are periphery mounted secondary radical generation chambers (mini-chambers) capable of controlling the rates of radical generation. For this preliminary study the engine is operated on hydrogen under conditions conducive to homogeneous combustion RI (HCRI). One goal at the lower CR's normally needed in rotary-engine operations (<10:1) is to see whether HCRI alone can substantially extend the lean burn region of this rotary diesel engine with hydrogen as fuel. The ultimate aim is to enable high-power density operations with both low NOx emissions and low heat rejection. With these ends in mind a detailed examination is made (via simulation) of the effects of internally generated “radicals” on the combustion chemical-kinetics of this engine.