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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.

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.

Engine manufacturers and product designers are currently under significant pressure to reduce fuel consumption, emissions, and noise from two-stroke engines. Improved engine breathing goes a long way toward overcoming these challenges by providing better charge delivery, complete exhaust gas scavenging, and minimal fuel short-circuiting. Reed valve motion and the resulting gas flow are highly coupled phenomena. Understanding and controlling these dynamics and their interactions is critical to effective intake breathing. A comprehensive effort to model reed valves at a level sufficient for engine design using engine simulations is still incomplete. This work is focused on the assessment, development and validation of a reed valve model suitable for engine simulations. In this work, a representative two-stroke engine reed valve is modeled in a detailed fluid/structures, multi-physics CFD code which fully resolves both the flow-field and the details of the deflecting reed plate.

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).

Two-Color imaging optics were developed and used to observe soot emission processes in a modern heavy-duty diesel engine. The engine was equipped with a common rail, electronically-controlled, high-pressure fuel injection system that is capable of up to four injection pulses per engine cycle. The engine was instrumented with an endoscope system for optical access for the combustion visualization. Multidimensional combustion and soot modeling results were used for comparisons to enhance the understanding and interpretation of the experimental data. Good agreement between computed and measured cylinder pressures, heat release and soot and NOx emissions was achieved. In addition, good qualitative agreement was found between in-cylinder soot concentration (KL) and temperature fields obtained from the endoscope images and those obtained from the multidimensional modeling.

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.

Engine experiments have shown that with high-pressure multiple injections (two or more injection pulses per power cycle), the soot-NOx trade-off curves of a diesel engine can be shifted closer to the origin than those with the conventional single-pulse injections, reducing both soot and NOx emissions significantly. In order to understand the mechanism of emissions reduction, multidimensional computations were carried out for a heavy-duty diesel engine with multiple injections. Different injection schemes were considered, and the predicted cylinder pressure, heat release rate and soot and NOx emissions were compared with measured data. Excellent agreements between predictions and measurements were achieved after improvements in the models were made. The improvements include using a RNG k-ε turbulence model, adopting a new wall heat transfer model and introducing the nozzle discharge coefficient to account for the contraction of fuel jet at the nozzle exit.