ɸ‑sensitivity - A step forward in future fuels evaluation : ɸ‑sensitivity - A step forward in future fuels evaluation

Abstract: Popular summary:Internal combustion engine is a developed and established technology whichcontributes largely to the transportation of goods and people. In one hand, theburning of fossil fuels is the main reason for the combustion engines to beconsidered unsustainable while on the other hand, the combustion behaviour ofrenewable fuels is not fully understood yet. This lack of knowledge is morepronounced when it comes to the combustion behaviour of renewable fuels inadvanced combustion engine concepts.In this PhD study a new empirical methods of fuel testing have been developed to quantify the equivalence ratio‑sensitivity of different liquid fuels. Equivalence ratio (ɸ) is the ratio of the actual fuel/air ratio to the stoichiometric fuel/air ratio.ɸ‑sensitivity is a decisive fuel property when it comes to the modern lowtemperature combustion technologies. The developed method in this study,characterize the ɸ‑sensitivity property of liquid fuels. ɸ‑sensitivity is fundamentally the sensitivity of auto‑ignition temperature or ignition delay to the variation of fuel equivalence ratio in the combustion. This property is important to understand since it separates different fuels impact on efficiency and emissions for modern engines where current fuel characterization methods (octane rating and cetane number) are indifferent. Therefore, ɸ‑sensitivity is needed to be understood for the development of renewable fuels in both conventional and advanced combustion engines. In this study a special test engine which is designed to be used for gasoline octane rating is the experimental apparatus. The Cooperative Fuel Research (CFR) engine is how this engine is called. In this engine, the height of cylinder head is adjustable to provide different Compression Ratio (CR). The variable CR of this engine makes it versatile for testing different fuels having different physical and chemicalproperties.Since the aim of this study was to develop an empirical ɸ‑sensitivity test method,different surrogate gasoline has been designed to cover a wide range of Research Octane Number (RON) values (≈105‑63). Surrogate fuels are single‑component fuels, binary blends, and multi‑component blends that are prepared in a way that emulates the desirable physical or chemical property of a more complex hydrocarbon like gasoline. In this study four components are used to prepare desirable surrogate fuels. These components are toluene, ethanol, iso‑octane, and n‑heptane. After method development step, four different alcohols were evaluated using the method. Due to the property similarity of iso‑butanol and n‑butanol to conventional gasoline, these two alcohols have been evaluated. Furthermore, blends of iso-butanol with RON (87) surrogate gasoline were evaluated. The result of this study shows that the developed test method (Lund ɸ‑sensitivity number) is an appropriate platform to evaluate and tailor fuels with a preferable ɸ‑sensitivity at a desirable octane number. Liquid fuels from renewable to conventional, to blends of renewable and conventional can be evaluated using Lund ɸ‑sensitivity method.Using this method provides required knowledge for application of different renewable fuels in internal combustion engines.