The topic of this paper is the computational modeling of the gas injection process in a large-bore natural gas fueled engine. At high injection pressures, the overall gas injection and mixing process includes compressible flow features such as rarefaction waves and shock formation. The injection geometries examined in the paper include both a two-dimensional slot and an axisymmetric nozzle. The computations examine the effect of the supply pressure/cylinder stagnation pressure ratio, with ratios ranging from 3 to 80, on the velocity and pressure profiles in the near field region. Computational fluid dynamics modeling was compared with results obtained from a two-dimensional analytical method of characteristics solution and experimental results. The comparison process evaluated factors such as pressure and Mach number profiles, jet boundary shape, and shock location.

Traditionally, thermodynamics and heat transfer have been taught at the undergraduate level as separate disciplines, and results in one area have usually not penetrated into the other area. The internal combustion engine is a complex engineering system with rich thermal science applications, both in thermodynamics and in heat transfer. We have developed web-based software applications written in Java which apply the disciplines of thermodynamics and heat transfer to internal combustion engines. The materials are being used in a introductory sophomore thermal science course which integrates thermodynamics and heat transfer, a junior level heat transfer course, and a senior level internal combustion engines elective class.

This study was designed to evaluate the effectiveness of aftermarket fuel delivery systems for vehicles fueled by compressed natural gas (CNG) and liquefied petroleum gas (LPG). Most of the CNG and LPG vehicles studied were converted to the alternative fuel after purchase. There are wide variations in the quality of the conversion hardware and the installation. This leads to questions about the overall quality of the converted vehicles, in terms of emissions, safety, and performance. There is a considerable body of emissions data for converted light-duty vehicles, and a smaller amount for medium- and heavy-duty vehicles. However, very few of these data involve real world conditions, and there is growing concern about in-use emissions. This report also attempts to assess factors that could allow in-use emissions to vary from the best-case'' results normally reported. The study also addresses issues of fuel supply, fuel composition, performance, safety, and warranty waivers. The report is based on an extensive literature and product survey and on the author's experience with fuel delivery systems for light-duty vehicles.