Reduction of Diesel Engine Combustion Noise through Various Injection Strategies

The contribution of engine borne noise is the major source of vehicle noise in diesel powered vehicles. The engine noise can be minimized by modification of engine components design and also with different acoustic abatement techniques. The research activities were carried out on 4-cylinder CRDe engine for SUV application. All the emission and performance parameters along with combustion noise was captured continuously for all the part load points from 1000 RPM to 2750 RPM with respect to the different road conditions and driving cycle. This paper targets on reducing the combustion noise at the noise prone zones only on the basis of the injection strategies ensuring no ill effect on the emissions and fuel economy. The first step was the reduction of rail pressure which helped noise levels to be reduced by almost 6 dB at noise zones. Main injection timing retardation was tried at all possible zones which influenced in considerable noise reduction at various zones. The BSFC deterioration was not observed and were found better at few zones. The NOx emissions improved, and PM emissions deteriorated after the above said changes were done. Further reduction of noise levels was tried employing the double pilot injection strategy at lower torque zones from 1000 to 2500 RPM. Pilot separation approach was then followed in order to improve PM and maintain better levels of noise. The overall tasks enabled on reducing noise till 15 dB from the reference condition.