Investigating the Effects of Alternative Fuels with Different Aromatic Species on Compression Ignition Engine Emissions and Performance

Harmful emissions are the major challenge for combustion systems and continuously increasing with the use of fossil-based feedstock around the globe. Compression ignition engine (CI) is one of the main emitters of harmful pollutants. As compared to spark ignition (SI) engine, CI engine produces high particulate matter (PM) and nitrogen oxides (NOx) emissions. The need for the improvement of engine performance; fuel consumption and thermal efficiency is another challenge. Investigating the effect of fuel components is one of the approaches that can be used to reduce exhaust emissions and improve performance. knowledge gaps need to be completed in how different aromatic species of the same type impact the engine performance and emissions. The contributions of the present study are in the detailed investigations reporting and analyzing the role of different alkylbenzenes and polycyclic aromatics in surrogate fuels on emissions and engine performance. This knowledge would help the future fuel industry to produce future fuels with appropriate alkylbenzenes and polycyclic aromatics for lower emissions and improved performance. In addition, the study provides more details about the influence of different aromatic concentrations in the fuel on emissions and performance. To attain the aims of the current study, different alkylbenzenes and polycyclic aromatics were blended with surrogate fuel at three different contents. The blended fuels were tested experimentally using a direct injection (DI) CI engine at two different load conditions. Appropriate sampling line, particulate and gaseous species measurement instrumentation were integrated with the engine rig in order to take measurements accurately. Impact of different properties of aromatic species on PM, NOx UHC’s, CO and engine performance has also been investigated and forms a part of contribution to knowledge. The overall results show that increasing aromatic content in fuel contributes to high levels of exhaust emissions and impacts engine performance. Comparison among alkylbenzenes surrogate blends presents that blends containing ethylbenzene produce low exhaust emissions and better performance because of its properties; high calorific value, cetane number, low density and hydrogen-to-carbon (H/C) ratio. While, indane surrogate blends have better results as compared to other polycyclic aromatics. Finally, optimum surrogate blend is formed with appropriate aromatics (ethylbenzene and indane). Operating the engine with optimum blend results in significant reduction of PM, smoke, unburned hydrocarbons (UHC) as compared to commercial diesel fuel. However, increase of brake thermal efficiency (BTE), reduction of NOx and brake specific fuel consumption (BSFC) are insignificant. NOx and PM correlations are developed as a function of significant impacted fuel properties. The prediction models developed are highly agreeing with experimental results. Overall, this work would provide basis for selection of aromatic species in future fuels, as not all aromatic species lead to higher PM, NOx or give the optimal engine performance.