A team at the Clean Combustion Research Center (CCRC), King Abdullah University of Science and Technology (KAUST), Saudi Arabia, is proposing the use of terpineol as an octane booster for gasoline in a spark ignited (SI) engine. Terpineol is a bio-derived oxygenated fuel obtained from pine tree resin, and has the advantage of higher calorific value than ethanol, enabling improved fuel economy.
Terpineol is produced by the addition of phosphoric acid with pinene, which is extracted from the resins of pine tree. It is an unsaturated cyclic alcohol; previous work on the combustion chemistry of alcohols suggested that terpineol will have a high antiknock potential.
In the age of engine downsizing and supercharging, high octane fuels are increasingly needed for spark ignited (SI) engines. High octane fuels enable higher engine thermal efficiency due to their ability to withstand more compression in the end-gas, thereby avoiding knock when spark timing is advanced. As such, these fuels are more suitable for operation in a SI engine at higher compression ratio (CR) and super charged conditions. Researchers are continuously looking for novel octane boosters, among which ethanol has emerged as a potential octane booster for gasoline fuels.—Vallinayagam et al.
The KAUST team blended terpineol with a non-oxygenated gasoline (FACE F, Fuels for Advanced Combustion Engines) in various proportions for testing in a single-cylinder gasoline direct injection (GDI) engine. They also studied fuel ignition properties in an ignition quality tester (IQT).
The IQT results demonstrated a long ignition delay of 24.7 ms for terpineol and an estimated research octane number (RON) of 104—higher than commercial European (Euro V) gasoline.
The operation of a gasoline direct injection (GDI) SI engine fueled with terpineol-blended gasoline enabled spark timing advancement and improved engine combustion. The knock intensity of FACE F + 30% terpineol was lower than FACE F gasoline at both maximum brake torque (MBT) and knock limited spark advance (KLSA) operating points.
Increasing proportions of terpineol in the blend caused peak heat release rate, in-cylinder pressure, CA50, and combustion duration to be closer to those of Euro V gasoline. Furthermore, FACE F + 30% terpineol displayed improved combustion characteristics when compared to Euro V gasoline.
R. Vallinayagam, S. Vedharaj, Nimal Naser, William L. Roberts, Robert W. Dibble, S. Mani Sarathy (2016) “Terpineol as a novel octane booster for extending the knock limit of gasoline,” Fuel, Volume 187, Pages 9-15 doi: 10.1016/j.fuel.2016.09.034