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Heavy-Duty Integrated Power System, 03-9896

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Principal Investigators
Rudolf H. Stanglmaier
Thomas W. Ryan III
Allen W. Gray III

Inclusive Dates: 03/23/95 - 04/01/99

Background - Homogeneous charge compression ignition (HCCI) is a distinct combustion mode in which a premixed charge of air, fuel, and combustion products is compressed until it autoignites. Lean air/fuel ratios or high amounts of recycled combustion products are used to limit the heat-release rate and to promote low reaction temperatures. The combustion reaction is thought to initiate at multiple locations simultaneously, transpire very quickly, and be devoid of localized high-temperature regions or flame-fronts. HCCI combustion results in low levels of NOx production as compared with homogenous charge spark ignition or diesel combustion. In addition, HCCI combustion offers the potential for low particulate emissions and high fuel efficiencies in engine applications. However, several restrictions must still be overcome to make HCCI technically feasible for over-the-road applications, including controlling the combustion phasing over a range of engine speeds and loads and improving the power density of HCCI engines.

Approach - The objective of this project is to generate a fundamental understanding of HCCI combustion and to apply this knowledge to the development of practical HCCI engines. A single-cylinder, variable compression ratio engine has been used extensively to investigate the operating range of HCCI combustion and to explore the effects of compression ratio, intake temperature, and fuel composition. The lessons learned from this work are being applied to the design of a six-cylinder HCCI engine that will be used to evaluate the potential benefits of this technology and to demonstrate the feasibility of multicylinder HCCI engines. SwRI is converting a commercial 8.1-liter natural gas engine to HCCI operation, and its performance will be assessed.

Accomplishments - Over the past three years, this project has sought to acquire a fundamental understanding of HCCI combustion. Results obtained from the single-cylinder experiments have shown that fuel properties have a great effect on HCCI combustion and that choice of the correct fuel plays a crucial role in reducing the required intake air temperature and increasing power density. The most promising fuel tested to date is Fischer-Tropsch (F-T) naphtha. This fuel results in low levels of NOx and particulate emissions, provides double the power output as diesel fuel (on HCCI operation), and operates at ambient intake temperatures. Another important accomplishment of this project has been the development of a cylinder-pressure-based control system to maximize power output without exceeding design operating pressures of the engine. This control strategy, as well as port fuel injection of F-T naphtha, will be incorporated to the multicylinder HCCI engine under development.

Engines, Fuels, Lubricants, and Vehicle Systems Program
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