Combustion noise quality improvement in a common rail Diesel Engine at Low idle for Agriculture Tractor

Vehicle level NVH performance plays major role in customer comfort criteria. Tractor low idle rpm Sound Quality can be one of the parameter which influences customer purchasing decision based on comfort criteria. Modern diesel engines with stringent emission norms together with fuel economy requirements pose challenges to noise control. Common rail engine technology has advantage of precise fuel delivery and combustion control which needs optimization to achieve the conflicting requirements of noise, emission and fuel efficiency. Engine noise at low idle condition is dominated by combustion noise which depends on rate of pressure rise inside the cylinder during combustion. The important parameters which influence cylinder pressure rise are fuel injection timing, pilot injection quantity and its separation, rail pressure and EGR valve position. The study is carried out to understand which combustion parameter is most influencing to achieve better sound quality of engine. Taguchi design of experiments (DOE) technique is used for optimizing different common rail parameters like rail pressure, pilot injection quantity and separation and injection timing etc . The effect of each parameter is discussed in detail in terms of emission and Sound Quality. The technique has helped to optimize each common rail combustion parameter to achieve reduction of 6dB (A) noise levels at low idle rpm along with minimal deterioration in emission parameters.