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The effect of fuel injection pressure on the brake specific fuel consumption (BSFC) and brake specific particulate matter (BSPM) emissions at NOx parity (constant NOx emissions level) was investigated under different conditions of engine speed and load using a 2.5L DDC/VM-Motori common-rail, turbocharged, direct injection (DI), light-duty diesel engine. NOx parity at varying conditions of speed, load, and fuel injection pressure was achieved by changing the injection strategy and timing. The results of these analyses confirmed the well-established trends that soot emissions reduce with an increase in rail pressure at the expense of increasing NOx emissions. With an increase in engine speed (at constant load and NOx parity), it was observed that BSFC, CO, CO₂, and hydrocarbon emissions decreased, while BSPM decreased initially and increased later on. Increasing the fuel injection pressure resulted in an increase in BSFC, CO, CO₂, and hydrocarbon emissions.

The latest US emission regulations require dramatic reductions in Nitrogen Oxide (NOx) emissions from vehicular diesel engines. Selective Catalytic Reduction (SCR) is the current technology that achieves NOx reductions of up to 90%. It is typically mounted downstream of the existing after-treatment system, i.e., after the Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF). Accurate prediction of input NO₂:NO ratio is useful for control of SCR urea injection to reduce NOx output and NH₃ slippage downstream of the SCR catalyst. Most oxidation of NO to NO₂ occurs in the DOC since its main function is to oxidize emission constituents. The DOC thus determines the NO₂:NO ratio as feedgas to the SCR catalyst. The prediction of NO₂:NO ratio varies as the catalyst in the DOC ages or deteriorates due to poisoning. Thus, the DOC prediction model has to take into account the correlation of DOC conversion effectiveness and the aging of the catalyst.

The oxides of nitrogen (NOx) produced during combustion in an automobile engine play a major role in atmospheric chemistry and therefore need to be reduced by modifying vehicle engine designs and fuels of tomorrow. In a combustion chamber of a spark ignited engine, NOx is formed as atmospheric nitrogen competes with fuel molecules to couple with oxygen in the extremely hot burned gases behind the proceeding flame front (Zeldovich type) and as reactions occur directly in the combustion flame zone (“prompt” type). Since little nitrogen is present in the fuel, the fuel contribution to the overall NOx emissions is minor. Certain combustion chamber deposits have been shown to increase NOx emissions by thermally insulating the combustion chamber and taking up chamber volume, thus slightly increasing the compression ratio of the engine and raising the combustion gas temperature.

The effect of knock intensity on exhaust emissions was examined in a single cylinder spark ignition engine. The exhaust components surveyed were carbon monoxide, carbon dioxide, oxides of nitrogen (as NO), and total unburned hydrocarbons. Knock was induced solely by changing the spark timing. To describe knock intensity quantitatively, the magnitudes of the rate of pressure irregularities occurring during the combustion process were utilized. The use of the rate of pressure change to define a quantitative knock intensity scale is supported by an apparent generalization of the stoichiometric air-fuel ratio data. Graphs are presented that indicate the dependency of power output as well as exhaust emissions on knock intensity for various air-fuel ratios.

An experimental program was conducted to determine the effect of burning used lubricating oil mixed with fuel oil in a single cylinder Diesel engine. With increasing fuel costs, the prospect of using alternative fuels increases dramatically. Large quantities of used lubricating oil are currently available and could be used in fuel blends for Diesel engines. The used lubricating oil-fuel oil ratios used in this study were 2.5%, 5%, 10%, and 15% used lubricating oil by volume. The effect of burning these blends on unburned hydrocarbons, carbon monoxide and oxides of nitrogen is reported along with a comparison to baseline values for pure Diesel fuel. Tests were run at 1800, 2400 and 3000 rpm at 1/4, 1/2, 3/4 and full rack positions for each fuel blend. The general condition of wear in the engine along with deposit formation and analysis is reported. The effect of the used lubricating oil on thermal efficiency and BSFC is shown for the blends studied.

This paper illustrates a method to determine the experimental uncertainties in the measurement of tailpipe emissions of carbon dioxide, carbon monoxide, nitrogen oxides, hydrocarbons, and particulates of medium-, and heavy-duty vehicles when tested on a heavy-duty chassis dynamometer and full-scale dilution tunnel. Tests are performed for different chassis dynamometer driving cycles intended to simulate a wide range of operating conditions. Vehicle exhaust is diluted in the dilution tunnel by mixing with conditioned air. Samples are drawn through probes for raw exhaust, diluted exhaust and particulates and measured using laboratory grade emission analyzers and a microbalance. At the end of a driving cycle, results are reported for the above emissions in grams/mile for raw continuous, dilute continuous, dilute bag, and particulate measurements.