A technical and economic evaluation of oxygen-enriched combustion in diesel engines using water-emulsified fuels

Abstract

The technical and economic feasibility of using oxygen-enriched air and low-grade fuels in diesel cogeneration systems is reported. The effects of oxygen enrichment, low-grade fuels, and water addition on the combustion process were studied using first principles of combustion theory; the effects of oxygen enrichment and water addition on diesel engine performance were analyzed with a computer model; air separation technologies were evaluated; the coupling of the oxygen plant to the diesel engine was studied; and the internal rate of return for several system options was determined. The greatest improvement in economic benefits is obtained primarily from fuel switching, and the optimal oxygen enrichment is the minimum that will enable medium- and high-speed diesel engines to use low-grade fuels. Two oxygen-enrichment technologies, selective membranes and pressure-swing adsorption, were identified as being both technically and economically feasible. Oxygen enrichment increases the power of the diesel engine by allowing an increased fueling rate, although increased pressures and temperatures may decrease engine life. Oxygen enrichment decreases CO, smoke, and particulate emissions from the engine but increases NO{sub x} emissions. However, the NO{sub x} emissions, pressures, and temperatures can be controlled by water addition and fuel-injection timing adjustments. 53 refs., 33 figs., 20 tabs.