Title: Study of combustion noise mechanism under accelerating operation of a naturally aspirated diesel engine

Authors: Gequn Shu, Haiqiao Wei

Addresses: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China. ' State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China

Abstract: This paper studies combustion noise mechanism during transient operation of naturally aspirated-DI-Diesel engines by developing testing techniques and methods. By testing and analysing four load conditions, the mechanism that governs the differences between transient and steady-state combustion noise is studied. The analysis demonstrates that during transients, the combustion chamber wall temperature, fuel injection pressure, maximum needle lift and unseal standing time of needle lift are higher than those under steady-state conditions for the same speed and load; a fact causing differences in ignition delay, start point of combustion and fuel injection quantity during transient conditions with a low acceleration rate. It is shown that the differences between the combustion chamber wall temperature, fuel injection pressure and ignition delay, as well as high-frequency oscillation of combustion pressure develop during transients in a different pattern compared to the respective steady-state conditions, thus resulting in different combustion noise emissions.

Keywords: diesel engines; transient conditions; combustion noise; vehicle design; acceleration; ignition delay; fuel injection; combustion chamber wall temperature.

DOI: 10.1504/IJVD.2007.013669

International Journal of Vehicle Design, 2007 Vol.45 No.1/2, pp.33 - 46

Published online: 11 May 2007 *

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