Biofuel effect on flame propagation and soot formation in a DISI engine

CAR2017 International Congress of Automotive and Transport Engineering - Mobility Engineering and Environment

工业技术;运输工程

Irimescu, A.^1 ; Merola, S.S.^1 ; Di Iorio, S.^1 ; Vaglieco, B.M.^1

Istituto Motori - CNR, via G. Marconi, Napoli

80125, Italy^1

关键词: Different distributions;    Direct injection spark ignition engines;    Flame development;    Higher compression ratios;    Latent heat of vaporization;    Morphological parameters;    Temporal and spatial evolutions;    Thermodynamic measurements;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/252/1/012092/pdf
DOI  :  10.1088/1757-899X/252/1/012092

学科分类：工业工程学

来源: IOP

【 摘 要 】

The use of biofuels, especially in transportation and industrial processes, is seen as one of the most effective solutions to promote the reduction of greenhouse gases and pollutant emissions, as well as to lighten the dependence from petro-fuel producers. Biofuels are defined as a wide range of energy sources derived from biomass. In this category, alcohols produced through fermentation, such as ethanol and butanol, are considered some of the most suitable alternatives for transportation purposes. The benefits of bio-ethanol addition to gasoline have always been recognized for practical reasons. Apart from the variety of sources which it can be produced from, ethanol can raise the octane rating, given its improved anti-knock characteristics, allowing the use of higher compression ratios and higher thermal efficiency. However, ethanol's high latent heat of vaporization can cause problems during cold-start due to poor evaporation. On the other hand, in hot climates ethanol fuelling can result in adverse effects such as vapour lock. Butanol can be considered as an emergent alternative fuel. Normal butanol has several well-known advantages when compared to ethanol, including increased energy content, greater miscibility with transportation fuels, and lower propensity for water absorption. Despite of these pros, the costs of n-butanol production are higher due to lower yields compared to ethanol. Moreover, vaporization remains a critical aspect of this biofuel. Understanding the effect of biofuels on in-cylinder combustion processes is a key-point for the optimization of fuel flexibility and achieving lower CO2 emissions. To this aim, a combined thermodynamic and optical investigation was performed on a direct injection spark ignition engine fuelled with ethanol, butanol and gasoline. Fuels were compared by fixing the injection and spark ignition strategies. Thermodynamic measurements were coupled with optical investigations based on cycle resolved flame visualization. Optimized procedures of image processing were applied to follow the evolution of the flame front in terms of morphological parameters and to evaluate the local distribution of diffusive flames induced by oxidation of fuel deposits during late combustion. These data were correlated with exhaust gas measurements. The experiments confirmed that the chemical-physical specifications of the tested fuels strongly influenced the temporal and spatial evolution of the flame front. Moreover, different distributions and intensities of diffusive flames were observed. These results demonstrated the effect of the fuel on the deposits amount and distribution in the combustion chamber, at fixed operative conditions.