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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.

A detailed examination is made of the effects of internally generated “radicals” on the chemical-kinetics mechanism for CNG (compressed natural gas) combustion in a direct-injection (DI) diesel engine operating under ultra-lean fuel conditions at normal diesel compression ratios. The primary generating site for these “radical” chemical species is a set of mini-chambers located within the cylinder head. Explored in this study is the potential for controlling the autoignition timing of the engine by altering the rates of this radical generation process via the temperature management of these chambers. The study suggests that the temperature management of these secondary chambers may help enable the control of the ignition timings in response to engine load changes.

The aim of this work is to establish a means for operating a four-stroke direct injection (DI) homogeneous-combustion radical-ignition (HCRI) engine robustly on hydrogen with low NOx emissions. To this end the use of fuel-insertion control for the fuel entering the radical generating mini-chambers is studied in some detail. The study points to the possibility that, if the compression ratios (CR's) are kept within the normal (conventional) range for diesel operations and heat losses are reduced, over its entire operating regime the hydrogen IC engine may be made to run with only one ignition mode: namely RI (radical ignition). Details of the altered chemistry of radical ignition and OH driven radical generation are studied numerically using a newer chemical-kinetics mechanism within two separate but connected open systems representing the distinctive main-chamber and mini-chamber processes.

This qualitative numerical study examines the effects of internally generated “radicals” on the chemical-kinetics mechanism responsible for the combustion of CNG (compressed natural gas) in a direct-injection naturally aspirated diesel engine at reduced diesel compression ratios. The initial generating site for these “radical” chemical species is a set of micro-chambers well placed within the pistons. Explored in this study are not only the effects of these radical species on main chamber combustion process but also the simultaneous effects of the main chamber combustion process on the OH radical driven partial oxidation process taking place in the micro-chamber. Discovered in this study is the fact that when these radical species are passed to the main chamber, they also facilitate “radical” generation on a slightly smaller scale in the main chamber also.

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.

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.