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Due to the cost and mobility advantages of diesel-powered mine vehicles over electric vehicles, it is anticipated that the diesel engine will become more widely used in underground mines in this country. Concern has arisen, however, over the impact of diesel exhaust emissions on the air quality in the underground mine environment. A literature search has been conducted to identify known effects of fuel properties on the reduction of diesel exhaust emissions. Reductions can be obtained by optimizing fuel properties and by considering alternative fuels to standard diesel fuel. However, the data base is relatively small and the results highly dependent on engine type and operating conditions. Engine studies on a typical mine diesel are necessary to draw quantitative conclusions regarding the reduction of emissions, especially particulates and NO2 which have not been generally addressed in previous studies.

Diesel exhaust emission levels have been measured during discrete transients in speed and load, and with changes made to the engine and fuel. Particulate, oxides of nitrogen, unburned hydrocarbon, and carbon monoxide measurements were made for two fuels, DF2 and 5 percent water-in-fuel microemulsion, for both a standard Caterpillar 3304 and a modified 3304 engine. Engine modifications included increasing compression ratio and retarding injection timing. This paper examines the effects of the water addition and engine modification on the steady-state and transient emission levels. In general, the addition of water decreased the particulate and oxides of nitrogen emission levels for the standard engine, but increased the levels of hydrocarbons and carbon monoxide. For the modified engine, the water addition resulted in a slight decrease in oxides of nitrogen and particulate matter at high speed and load conditions.

A technique is verified for mapping the exhaust emission levels of a diesel engine during transient operation. Particulate matter, oxides of nitrogen, hydrocarbons, and carbon monoxide emissions were sampled for discrete segments of various transient cycles. Each cycle consisted of four distinct segments. The discrete segments are described by average engine conditions, rate of change variables, and segment length. Regression analysis was used to develop equations relating the emission levels during each segment to the engine parameters. The regression equations were then used to obtain estimates of composite emission levels of several complex transient cycles that were subsequently tested. These cycles included the EPA heavy-duty transient cycle and two simulated heavy-duty cycles developed for underground mine vehicles. Comparison of the predicted and measured cycle emissions are made for the EPA heavy duty cycle and the simulated mine cycles.