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This research describes the potential to adopt detailed chemical kinetics for practical and potential future fuels using tri-component surrogate mixtures capable of simulating fuel octane “sensitivity” . Since the combustion characteristics of modern fuels are routinely measured using the RON and MON of the fuel, a methodology to generate detailed chemical kinetic mechanisms for these fuels based on these data is presented. Firstly, a novel correlation between various tri-component blends (comprised of i-octane, n-heptane and toluene) and fuel RON and MON was obtained by carrying out standard octane tests. Secondly, a chemical kinetic mechanism for tri-component fuels was validated using a Stochastic Reactor Model (SRM) suite, an in-cylinder engine combustion simulator, and a series of engine experiments conducted in HCCI operating mode.

The auto-ignition or anti-knock quality of a practical fuel is defined by the Octane Index, OI = (1-K)RON + KMON where RON and MON are the Research and Motor Octane numbers and K is a constant depending only on the pressure and temperature variation in the engine. K decreases as the compression temperature in the unburnt gas at a given pressure in the engine decreases and can be negative if this temperature is lower than in the RON test. As spark ignition (SI) engine designers seek higher efficiency knock becomes more likely. Moreover such initiatives - direct injection, higher compression ratios, downsizing and turbocharging - will reduce the unburnt gas temperature for a given pressure and push the value of K downwards. In Europe there is evidence of a monotonic decrease in the average K value from 1987 to 1992. In 37 different Japanese and European cars (34 models) equipped with knock sensors that have been tested K has been found to be negative in most cases.