In compression ignition (CI) engines, nitrogen oxides (NOx) formation is a temperature dependent function and occurs when the temperature in the combustion chamber exceeds 2000 K. Therefore in order to reduce the NOx emissions from exhaust of the engine, it is compulsory to keep peak cylinder temperature under control. NOx can be reduce by late injection of fuel in the combustion chamber. This is an effective technique but increase the fuel
consumption rate. So the most promising way to reduce the NOx emission by using EGR technique. In this research work, the effects of different EGR ratios on the performance and emission characteristics of a diesel engine are investigated. The tests were carried out on a four cylinder variable speed CI engine at different load conditions like: partial load, half load and full load. The three EGR rates (5%, 10% and 15%) were utilized with an intention to reduce the high NOx emissions that were occur at high engine loads. The use of EGR in diesel engine resulted in maximum reduction in NOx emissions up to 10% at partial load, up to 5% at half load and up to 8% at full load without any significant penalty in particulate matter emissions. Smoke opacity increased up to 15 % EGR rate. There was also an increase in hydrocarbon (HC) and carbon monoxide (CO) emissions when compared to pure diesel.
EGR, NOx, Pollution, CI Engine