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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.

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.

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 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.

This four-stroke engine study examines how micro-chamber generated “radicals” can facilitate the robust control of autoignition in direct-injection (D.I.) diesel engines. These internally produced radicals enable combustion under much lower than normal diesel compression ratios (CR's) and temperatures and make the chemical-kinetics control of autoignition timing a reality. In an attempt to better understand the mechanisms enabling radical based chemical control, the altered chemistry of radical ignition is studied numerically for the case of H2 combustion. Numerical simulation is based on a detailed mechanism involving as many as 19 species and 58 reactions. This H2 chemical-kinetics mechanism is simultaneously solved within two separate but connected open systems representing the distinctive main-chamber and micro-chamber processes (Figure 1).

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 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.

Using methanol as a fuel, this study examines the chemical-kinetics mechanism responsible for the enhancement of combustion in I.C. engines due to intermediate and radical chemical species produced in micro-chambers of Sonex Combustion System (SCS) pistons. This homogeneous combustion enhancement was first shown experimentally (in 1991) to be capable of enabling an IC engine to operate stably and smoke free on methanol over an entire engine map while using a compression ratio of only 17:1 and without a spark or other assists. The distinction is made between thermally induced variants of homogeneous combustion: HCCI and ATAC; and intermediate species/radical induced homogeneous combustion: LAG and SCRl (Stratified Charge Radical Ignition).