Combustion Modes Induced by Oil-Droplet Gas-Phase Pre-ignition in the Chamber under Different Environmental Conditions

Abstract

The combustion of combustible gaseous mixture with/without oil droplet is studied based on a rapid compression machine under conditions comparable with the state at the end of compression in SI-engine cylinder. The ignition and burning processes of gaseous mixtures with oil droplet and the pressure traces for same initial state cases with and without oil droplets are obtained experimentally. The combustion of the gaseous mixture without oil droplet is in an integrated homogeneous auto-ignition mode at lower effective pressures or temperature, while it is in an integrated sequential auto-ignition and detonation mode at higher effective pressures and temperature, which is controlled by the ignition delay of gaseous mixtures. For gaseous mixture with oil droplet, the gas-phase pre-ignition can be induced, while the combustion modes are affected significantly by negative temperature coefficient character of the ignition delay. The combustion of gaseous mixture is in the end-gas homogeneous auto-ignition mode with no knock when its effective temperature is in the pre-region of NTC influence region, while it is in the end-gas sequential auto-ignition and detonation mode with knock or super knock when its effective temperature is in the NTC region. The peak pressure is close to that of constant-volume combustion for the integrated (end-gas) homogeneous auto-ignition mode. The peak pressure is close to that of detonation for the integrated (end-gas) sequential auto-ignition and detonation mode under lower effective pressure conditions. However, it is much larger than that of detonation for the end-gas sequential auto-ignition and detonation mode under higher effective pressure conditions.

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