Effect of Compression Ratio and Injection Pressure on Emissions and Fuel Consumption of a Small Displacement Common Rail Diesel Engine

Abstract

<div class="htmlview paragraph">The effect of variations of compression ratio (CR) and injection pressure (IP) on the emissions and performance of a small displacement common rail off-road diesel engine was evaluated.</div> <div class="htmlview paragraph">The operating point corresponding to the 5th mode of the ISO 8178 - C1 test cycle (intermediate speed / full load) was considered, since it represents one of the most critical operating conditions as far as exhaust emissions are concerned.</div> <div class="htmlview paragraph">The main effect of a reduction of the compression ratio, for a fixed injection timing, was found to be, as expected, an increase in NOx emissions along with a decrease of PM emissions, with a substantial redefinition of the PM-NOx trade-off curve; the choice of a proper value for the start of injection can therefore lead to a better compromise among pollutant emissions, although remarkable variations in BSFC and combustion noise must be taken into account.</div> <div class="htmlview paragraph">Further improvements of the trade-off between PM and NOx emissions as well as of the combustion noise could also be achieved by means of a proper choice of the injection pressure.</div>