Relation between Form of Cylinder-Pressure Diagram and Noise in Diesel Engines

Abstract

This paper is a sequel to an earlier paper and carries this aspect of the investigation on from that stage. The frequency analysis of cylinder pressure has been shown to be a satisfactory criterion of the ‘noisiness’ of a cylinder-pressure diagram. In this paper the effect of the properties of the measuring equipment, such as band width, is considered so that the results may be interpreted quantitatively in terms of the pressure rises and hence the amount of combustion involved. The effect of operating variables on the frequency analysis is investigated. In some cases stroke-to-stroke variations are of importance and frequency analysis and emitted noise are compared in relation to background noise. Over a limited range, the effect of type of combustion chamber has been explored and some observations with petrol as the fuel are included.

Combustion noise radiation during the acceleration of a turbocharged diesel engine operating with biodiesel or n-butanol diesel fuel blends

“…10-30 Hz); the mean rate of pressure rise is generally reflected in the 1-4 kHz region, whereas the high frequencies (above 5 kHz) are usually indicative of the pressure rise change rates at the actual start of combustion. 1 Confirming the results of previous research, 45,46 as the premixed combustion was extended for the diesel-n-butanol blend compared with neat diesel oil, the high-frequency components of the cylinder pressure level were also enhanced, ultimately resulting in higher amounts of radiated noise. It was the limitations of the acquisition card sampling frequency that prohibited the depiction of sound level values for even higher frequencies in Figure 6; the latter are, in any case, of minor importance for the amount of emitted in-cylinder diesel engine combustion noise.…”

Computational assessment of combustion noise of automotive compression-ignited engines

“…These oscillations produce a broad peak on the cylinder-pressure spectrum and thus enhance the emitted noise in that frequency range." Therefore, Priede [38,44] showed for the first time that chamber resonances, also named as reverberation by other authors, in ICEs exist and they have an impact on engine acoustics [33].…”

“…The issue of combustion noise in relation to the in-cylinder pressure trace of CI engines has been studied experimentally over the last sixty years, but it is not until the work of Priede and Grove [44,45] in the decade of 1960 that clear differences are drawn between the raw pressure measured in the chamber along the different engine cycles, that includes the effect of the mechanical compression and the mean combustion pressure rise, and the resonant oscillations inside the combustion chamber specifically caused by the combustion. It is worth considering the following quote from Priede [44]:…”

“…The pressure instabilities caused by combustion are propagated as pressure waves, whose different interactions and reflections at the chamber walls force the gas to oscillate according to particular patterns [50]. This phenomenon, that may be observed by the presence of high frequency oscillations along the in-cylinder pressure evolution or by the characteristic broad peak in the spectrum also cited by Priede [44], is traditionally referred to as combustion chamber resonance, reverberation or even knocking.…”

“…Instead of performing complex and expensive engine modifications, most of the experimental studies are focused on analysing the pressure signal registered by a unique transducer. Indeed, practically all the classical papers cited above [38,[44][45][46] are based on this approach. The available data, although incomplete, offers enough information to link some parameters related to the engine operation with their respective acoustic response.…”