Combustion chamber resonances in direct injection automotive diesel engines: A numerical approach

Abstract

The resonant oscillation of burned gases in the combustion chamber of direct injection (DI) diesel engines appears to be the main excitation source of the engine block during combustion. This has led to the application of different techniques in order to study its generation mechanisms and to determine its relationship with combustion parameters such as bowl geometry, type of injector, injection parameters, etc. In this paper, a numerical methodology for the analysis of combustion chamber resonances is proposed. The numerical approach is validated by comparison with results from modal theory in a simple case. Then, this technique has been applied to the analysis of three different bowls, indicating their potential for the control of combustion chamber resonances.

Cycle by Cycle Trapped Mass Estimation for Diagnosis and Control

“…Although far from the TDC the cylindrical solution is valid, near the TDC this solution is not precise in common reciprocating engines as consequence of the singular bowl geometries [23]. Figure 2 compares the cylindrical resonance frequencies stated at (1) with the experimental frequencies obtained at a cylinder with bowl: although there is a frequency variation due to temperature, the resonance frequencies change even more.…”

Impact of Fischer–Tropsch and biodiesel fuels on trade-offs between pollutant emissions and combustion noise in diesel engines

“…The combustion signal is influenced by the rate of heat release, which is governed by the injection strategy and engine operating conditions. The resonance signal is associated with the gas oscillation produced by the abrupt pressure rise occurring in the combustion chamber [26]. This decomposition technique was previously applied to the analysis of cause-effect relations between the source (caused by combustion) and both the objective and subjective aspects of noise [23,24].…”

“…The second indicator, I 2 , quantifies the contribution of the resonance in the combustion chamber through the energy of the high frequency content of the in-cylinder pressure trace [26,31]. It is expressed by:…”

“…The external sound field of diesel engines comprises the contribution of both combustion and mechanical noise. In these engines, the self-ignition of premixed fuel causes a rapid pressure rise, producing the well known "knock", which excites the gas in the combustion chamber and consequently induces its oscillation [25,26]. The source of the combustion noise is related to pressure and mechanical forces, which are characterized by in-cylinder pressure, the system response is associated with the vibration of the block wall, and the radiated noise is the final effect of such a vibration [27,28].…”

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

“…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.…”