Browse Publications Technical Papers 2009-01-0324
2009-04-20

Impact of Fuel Properties on the Performances and Knock Behaviour of a Downsized Turbocharged DI SI Engine - Focus on Octane Numbers and Latent Heat of Vaporization 2009-01-0324

Facing the CO2 emission reduction challenge, the combination of downsizing and turbocharging appears as one of the most promising solution for the development of high efficiency gasoline engines. In this context, as knock resistance is a major issue, limiting the performances of turbocharged downsized gasoline engines, fuel properties are more than ever key parameters to achieve high performances and low fuel consumption's levels.
This paper presents a combustion study carried out into the GSM consortium of fuel quality effects on the performances of a downsized turbocharged Direct Injection SI engine. The formulation of two adapted fuel matrix has allowed to separate and evaluate the impacts of three major fuel properties: Research Octane Number (RON), Motor Octane Number (MON) and Latent Heat of Vaporization (LHV).
Engine tests were performed on a single cylinder engine at steady state operating condition. The engine corresponds to a downsized GDI SI engine with a displacement of 300cm3 and allows IMEP up to 30bar according to the engine speed. For each tested fuel, knock limitations have been evaluated at various engine speed.
Through the development of adapted methodologies for extended results analysis, contributions of RON, MON and LHV to knock resistance were isolated, evaluated and compared. This study confirms and weights the striking role of high RON values and the positive influence of the “cooling effect” linked to high LHV values. However, no clear impact of the MON was noticed.
Considering the double knock resistance action of ethanol, attention was particularly paid to ethanol blend fuels. In the case of a 20%v ethanol blend, the “cooling effect” brings from 30 to 60%, depending on engine speed, of the total knock resistance increase, compared to gasoline base fuel.

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