AN INVESTIGATION INTO THE STRUCTURAL RESPONSE OF A SMALL DIESEL ENGINE

Abstract

An investigation has been carried out for the determination of the structural response of a small (3.7 KW) single cylinder, water cooled, four stroke D.I. diesel engine for both piston and cylinder head excitations. In diesel engines, the combustion excitation is an important contributor to the overall noise. The combustion excitation follows two important structural paths to reach the outer surface and radiate as noise. These are (i) the combustion excitation acting on the piston transmits along the slider crankchain via the main bearings to the outer load bearing structure and eventually reaches the outer surface and (ii) the combustion excitation acting on the cylinder head transmits along the cylinder head bolts to the outer load bearing structure from where it reaches the outer surface. It has been found that the first path is more significant for surface vibration generation than the second one. This is due to a lower impedance of the first path than the second. It was found that there are larger number of significant resonances over 600 Hz and a few near 125 Hz