Auto-ignition Characteristics of Gasoline and Diesel Fuel Blends: A High-Pressure Ignition Delay and Kinetic Modelling Study

The ignition delay times (IDTs) of two different certified gasoline and diesel fuel blends are reported. These measurements were performed in a shock tube and in a rapid compression machine over a wide range of experimental conditions(φ= 0.5-2.0, T=700-1400 K and p=10-20 bar) relevant to internal combustion engine operation. In addition, the measured IDTs were compared with two relevant gasoline fuels: Coryton gasoline and Haltermann gasoline systematically under the same experimental conditions. Two different gasoline surrogates a primary reference fuel (PRF) and toluene PRF (TPRF) were formulated, and two different gasoline surrogate models were employed to simulate the experiments. Typical pressure and equivalence ratio effects were obtained, and the reactivity of the four different fuels diverge in the negative temperature coefficient (NTC) regime (700-900 K). Particularly at 750 K, the discrepancy is about a factor of 1.5-2.0. For the high Research Octane Number (RON) and high-octane sensitivity fuel, the simulation results obtained using the TPRF surrogate was found to be unreasonably slow compared to experimental results, due to the large quantity of toluene (77.6% by volume) present. Further investigation including reactants'concentration profile, flux and sensitivity analyses were simultaneously carried out, from which, toluene chemistry and its interaction with alkane (n-heptane and iso-octane) chemistry were explained in detail.