Analysis of High-frequency Combustion Noise Generation Mechanism in Pre-chamber Jet Combustion Gasoline Engine (Second Report)

- Evaluation Method for In-Cylinder Pressure Oscillations in Combustion Chamber Resonance Frequency Band -

Abstract

In this paper, an evaluation method for in-cylinder pressure oscillation is developed to quantitatively determine the magnitude of combustion noise in the 7-10 kHz band characteristic of pre-chamber jet combustion engines. In this method, in-cylinder pressure is measured for 400 cycles of crank angle history, and peak-to-peak amplitudes of pressure oscillations in the combustion chamber resonance band are obtained for cycleby- cycle using a bandpass filter. The peak-to-peak amplitudes are then averaged to obtain an evaluation indicator for in-cylinder pressure oscillation that enables an indirect evaluation of high-frequency combustion noise without measuring engine radiation noise. The results showed that the evaluation indicator in pre-chamber jet combustion is 16 times higher than that of conventional spark-ignited combustion, which can be evaluated at a single fixed in-cylinder pressure sensor.