Experimental study of the effect of gasoline components on fuel economy, combustion and emissions in GDI engine

An experiment was carried out in a gasoline direct injection (GDI) spark ignition engine to research the effect of gasoline components on fuel economy, combustion and emissions. According to the main components of gasoline, isooctane was selected as the base fuel. Short-chain, medium-chain and long-chain alkanes, ethers and aromatics were respectively blended with isooctane for comparison tests. Results show that aromatics benefit fuel economy under all operating conditions. T20 (20% toluene blended with isooctane) shows a comparatively lower break-specific fuel consumption (BSFC) for its lower cyclical variation while its maximum fuel saving ratio (FSR) could reach 5.42%. At light and medium loads of low speeds, short-chain alkanes shows great potential in the improvement of fuel economy. P20 (20% n-pentane blended with isooctane) whose maximum FSR could reach 4.64% presents better performance of fuel consumption under these operating conditions. By contrast, M20 (20% methyl tertiary butyl ether blended with isooctane) presents the higher BSFC for its higher cyclical variation and lower heat value, with the mean FSR being −2.75%. Medium-chain alkanes, long-chain alkanes and oxygenated fuels are conducive to the optimization of combustion process of the engine because they are able to advance combustion phase due to the shorter ignition delay. In conclusion, medium-chain and long-chain alkanes could reduce CO and THC emissions, to some extent. Compared with pure isooctane and T20, lower CO, NOx and THC emissions are observed for M20 and P20.