Combustion Ionization for Resonance Detection and Mitigation Using Pilot Injection in a Diesel Engine 2014-01-1360

Advanced injection systems play a major role in reducing engine out emission in modern diesel engines. One interesting technology is the common rail injection system which is becoming more vital in controlling emission due to its flexibility in injection pressure, timing and number of injection events. Many studies have showed the advantages of using such injection parameters to meet the strict emission and improve engine performance. A glow plug/ ion current sensor was used to measure ionization produced during the combustion process. The ion current signal contains many valuable information including combustion phasing, duration and combustion resonance. In prior publications, it was demonstrated the capability of the ion current to control the combustion phasing and the ability to detect combustion resonance. Therefore, the experimental testing was conducted under controlled combustion phasing using the feedback from the ion current sensor. Since the combustion noise is mainly produced by combustion resonance, the ion current sensor was used to detect combustion resonance in this work.

This paper presents a detailed study to characterize the effect of pilot injection quantity and timing on combustion noise at different engine operating conditions, where a development of a control strategy is proposed to mitigate combustion resonance via controlling pilot injection. Also, improvement in engine performance, fuel consumption and emission is concurrently targeted. The experimental investigation is conducted on a 4.5L four cylinder, turbo-charged, diesel engine equipped with common rail injection system. The results of this study provide a better understanding for the effect of pilot injection parameters that influence combustion noise, engine performance, fuel consumption and engine-out emission.