Influence of fuel injection parameters on combustion-induced noise in a small diesel engine

In this paper, the effects of fuel injection parameters on combustion-induced noise in a small single-cylinder direct-injection diesel engine used in a generator set are described. A range of fuel injection parameters, including injection timing and injection quantity, was explored to understand their influence on combustion-induced noise by studying their effect on in-cylinder pressure development. Fourier analysis was performed to understand the effects of changing combustion characteristics on in-cylinder pressure levels in different frequency ranges. In addition, time-frequency analysis was used to understand the changes in the combustion chamber resonance effects under different injection settings. Finally, overall engine noise levels were measured to confirm the changes as predicted by the in-cylinder pressure analysis. Results suggest that retarding main injection has the largest impact on reducing noise. When using split injection, earlier preinjection and larger preinjection quantities tend to result in lower noise.