Cavity resonances in engine combustion chambers and some applications

Abstract

Cavity resonances in engine cylinders are caused by combustion events such as the rapid rate of pressure rise that occurs during compression ignition in diesels or from knock in gasoline engines. These resonances generally occur at frequencies greater than 4 to 5 kHz where the engine structure is not an efficient acoustical radiator. However, when they occur at lower frequencies such as in engines with a large bore or in indirect injection diesels, they can be important in the noise generation process. They are also important for knock detection in gasoline engines. Current knock detection systems are tuned to the frequency band of the lowest cavity resonance in the combustion chamber. It is shown in the paper that higher order resonances can also be detected by a knock vibration sensor on the surface of the engine. Another use for the cavity resonances is to determine the bulk temperature of the gas in the combustion chamber as a function of crank angle. This technique is demonstrated in the paper for a heavy-duty two-stroke diesel. Also, the results of several fundamental investigations of cavity resonances in engine combustion chambers are reported briefly. Good agreement is obtained between theoretical prediction of the resonant frequencies and experimental observation. The splitting of degenerate modes into two components is discussed.

Cycle by Cycle Trapped Mass Estimation for Diagnosis and Control

“…Only R. Hickling et al, in the early 80's, tried to use the resonance phenomenon in order to estimate in-cylinder variables, particularly the bulk temperature [16,17]. Herein, unlike the works developed by R. Hickling et al, the authors have made use of time-frequency signal processing [18] for an accurate estimation of the resonance frequency.…”

Bayesian models for the determination of resonant frequencies in a DI diesel engine

“…Temperature of the gas in the combustion chamber, as a function of time, gives an indicator of what is occurring during combustion and the thermodynamic processes in the cylinder of the engine [3]. Equation 7 can be used to calculate the bulk temperature of the gas in the combustion chamber as a function of time, or crank-angle, using the resonance information found from model 5.…”

“…Calculating the resonant frequency accurately in an engine combustion chamber enables the characterisation of resonant frequencies that are associated with the speed of sound, and hence temperature [3,4,5,6,7]. Therefore, accurate isolation of resonant frequencies and their decay, as a function of time, or crank-angle, will allow the bulk temperature of the gas in the combustion chamber to be determined at any point within the region of interest.…”

FEM Approximation of Internal Combustion Chambers for Knock Investigations

“…With decreasing combustion chamber volume this approximation is too simple. Hickling et al [2] reported on the additional influence of the cylinder head that causes a mode splitting, i.e. a resonance may appear twice, rotated by a certain angle and with different frequency.…”

“…Although the appearance of knocking combustions and their problems concerning pollutant production, engine efficiency, and engine damages have been investigated for decades [1,2], there are still many aspects that are not completely understood and more knowledge would be helpful. This holds for the primary effect, the chemical processes of the combustion, as well as for the secondary effect, the excitation of the pressure resonances of the combustion chamber, as well as for the tertiary effect, the transfer of the resonances through the engine housing as structure-borne sound.…”