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A simple thermodynamically based engine design tool is developed to allow engine designers to start with the engine peak pressure limit, desired IMEP, and constraints on rate of pressure rise and thus generate an idealized Wire-Frame cylinder pressure cycle. After conversion into crank-angle based pressures, the apparent heat release rate (AHRR) is generated. The resulting AHRR1 represents an idealized heat release rate which is required to achieve the engine performance goals. This target AHRR is thus known prior to engine testing and serves as a guide to HCCI combustion test engineers. Using the Wire-Frame cycle tool, the ideal heat release rate for HCCI combustion is identified. For low IMEP, this is a single mode HRR centered at TDC. However, for medium and high loads, the combustion must be modified. Based upon the indications of the Wire-Frame HRR design tool, a few methods are identified and explored which allow higher IMEP from HCCI type combustion.

During the design stage, certification testing, or in field problem solving, t is of value for engine designers and engineers to have an understanding of how robust the engine design is to variation in the manufacturing process, in-use wear, controller and the testing processes. In this paper, a sensitivity analysis is performed on a parametric GTpower diesel engine model and using Robust Design methods NOx defects are reduced. Sensitivity analysis is conducted using a Plackett-Burman DOE. The DOE is performed on a 6 cylinder, direct-injection, turbocharged diesel engine model in GTpower, while Minitab is used for the experimental design and the factorial sensitivity analysis. It was found that the NOx population distribution was unacceptably high, yielding a 7.4% defect rate relative to an upper control limit of 5 (g/kw-hr).

In previous work the KIVA-II code has been modified to model modem DI diesel engines and their emissions of particulate soot and oxides of nitrogen (NOx). This work presents results from a program to further validate the NOx emissions models against engine experiments with a well characterized modern engine. To facilitate a simplified comparison with experiments, a single cylinder research version of the Caterpillar 3406 heavy duty DI diesel engine was retrofitted to run as a naturally-aspirated, propane-fueled, spark-ignited engine. The retrofit includes installing a low compression ratio piston with bowl, adding a gas mixer, replacing the fuel injector assembly with a spark plug assembly and adding spark and fuel stoichiometry control hardware. Cylinder pressure and engine-out NOx emissions were measured for a range of speeds, exhaust gas residual (EGR) fractions, and spark timing settings.

A simple thermodynamically based engine design tool is developed to allow engine designers to start with the engine peak pressure limit, desired IMEP, and restraints on rate of pressure rise and thus generate an idealized Wire-Frame cylinder pressure cycle. After conversion into crank-angle based pressures, the apparent heat release rate (AHRR) is generated. The resulting AHRR1 represents an idealized heat release rate which is required to achieve the engine performance goals. This target AHRR is thus known prior to engine testing and serves as a guide to HCCI combustion test engineers. Using the Wire-Frame cycle tool, the ideal heat release rate for HCCI combustion is identified. For low IMEP, this is a single mode HRR centered at TDC. However, for medium and high loads, a second mode of combustion is required to achieve maximum efficiency and retain the benefits of HCCI combustion. The second combustion mode ramps up to maintain the cylinder pressure at the desired firing pressure.