Effects of injection parameters and EGR on combustion and emission characteristics of rapeseed oil and its blends in diesel engines

An attempt has been made to study and compare the combustion and emission characteristics of the rapeseed oil (RSO) and blends of 50%, 30%, 20% and 10% of RSO in diesel for different fuel injection pressures, fuel injection timing and for different percentages of EGR. The injection pressure was varied from 800 bar to 1200 bar, EGR percentage from 0% to 20% and the injection timing from 9 degrees bTDC to TDC. These measurements were carried out in an automotive multi-cylinder diesel engine. The influence of these parameters on the exhaust emissions such as carbon monoxide (CO), total hydrocarbons (THCs), nitric oxides (NOx), smoke number (SN) and fuel consumption were also investigated. The in-cylinder pressure data was analysed to extract the apparent heat release rate, the ignition delay, combustion duration and the amount of heat released during the premixed and diffusion combustion phases of RSO and its blends. All these results were compared against diesel fuel under the reference engine operating conditions of 2.7 bar BMEP at 1500 rpm, 800 bar of the injection pressure, 0% of the EGR and 9 degrees bTDC of the injection timing. At reference engine operating conditions, the RSO and its blends resulted in a significant reduction of NOx emissions at the expense of CO, THC, SN, BSFC compared to diesel. The increase in the injection pressure lowered the soot emission but the NOx emissions for RSO and its blends resulted in higher values than diesel. The EGR and the injection timing had the potential of reducing the NOx emissions at the expense of CO, THC and SN. (C) 2012 Elsevier Ltd. All rights reserved.