Donald C. Siegla

Diesel particulates--what they are and why

The diesel passenger car offers a substantial advantage in fuel economy over its gasoline-powered counterpart, but the long-range future of the diesel in this application is threatened by future federal standards on exhaust particular emissions. These particulates are primarily combustion-generated carbonaceous soot in combination with a solvent-extractable hydrocarbon fraction. Particulate production involves an incompletely understood series of phenomena that includes nucleation, surface growth, agglomeration, dehydrogenation, oxidation, and adsorption and condensation of gaseous hydrocarbons. The contemporary state of understanding of these events is reviewed as they apply to the passenger-car diesel engine.

Heterogeneous Catalysis in the Diesel Combustion Chamber

Abstract Results have been reported recently suggesting that the use of a platinum-coated combustion chamber would significantly reduce gaseous and particulate emissions in a diesel engine. To examine these claims, a single-cylinder version of a conventional automotive diesel engine was tested with and without a platinum coating. For all conditions tested, application of the coating resulted in no significant changes in NOx, CO, HC or particulate emissions.

The Variable Stroke Engine - Problems and Promises

The concept of the variable stroke engine (VSE) is explained and problems related to its use are discussed. Single-cylinder combustion data are combined with published multi-cylinder VSE friction data to formulate an engine model. This engine model is coupled with a vehicle model to project 55/45 fuel economy (based on Environmental Protection Agency urban/highway schedule calculations) and NOx (nitrogen oxides) gm/mi which are compared with similar projections for a throttled engine. At an NOx level of 0.93 gm/km (1.5 gm/mi), VSE fuel economy improvements ranged from 2% to 20%, depending upon the frictional losses and the vehicle power-to-weight ratios used in the models (the higher the ratio, the greater the improvement). The calculations suggest that with the VSE, the lower the NOx level, the less the fuel economy improvement. Variable displacement engines using cylinder deactivation have been projected to offer fuel economy improvement competitive with that of the VSE.

Diesel for Passenger-Car Application Exploratory Study of the Low-Heat-Rejection Diesel for Passenger-Car Application

Eliminating the conventional liquid cooling system of a diesel engine to conserve energy normally rejected to that heat sink offers promise as a means for improving fuel economy. Such low-heat-rejection (LHR) diesels have generally been advanced for heavy-duty vehicles. In this study, application of the concept is analyzed for a light-duty indirect-injection diesel of the type used in passenger cars. The naturally aspirated LHR diesel is found to offer no fuel economy advantage, principally because of the deteriorated volumetric efficiency arising from hot cylinder walls. It is found that most of the energy conserved by deleting the cooling system is diverted to the exhaust gas. Methods examined for recovering the lost volumetric efficiency and/or harnessing the increased energy content of the exhaust include supercharging, adding a bottoming cycle, and combining the diesel with turbomachinery. The latter option is judged superior for the passenger-car application.

Dynamometer-Based Evaluation of Low Oxides of Nitrogen, Advanced Concept Diesel Engine for a Passenger Car

An Advanced Concept Diesel (ACD) engine, previously evaluated under a U.S. Energy Research and Development Administration contract, was dynamometer tested to provide data for the computer simulation of a diesel passenger car. The car was calculated to have the potential for meeting a 0.25 g/km (0.4 g/mi) NO standard (without cold start) if high EGR rates were introduced. The 0.25 g/km (0.41 g/mi) hydrocarbon standard would not be met by the unmodified vehicle, although use of an advanced transmission was projected to decrease hydrocarbons just to that level. Before the ACD engine is considered further, adequate durability should be demonstrated with high EGR rates, and lower hydrocarbon emissions are needed.