Influence of blending n-butanol with iso-octane and n-heptane on ignition delay times in a fuel ignition tester

Experimental results on the ignition delay trends of n-heptane, iso-octane, n-butanol, and the binary blends of n-butanol/n-heptane and n-butanol/iso-octane are presented. Fuel sprays were injected into a quiescent, pressurized, and preheated air in a constant volume combustion chamber using the Waukesha Fuel Ignition Tester. The averaged initial oxidizer pressure and temperature were 24 bar and 812 K, respectively. The fuel injection duration was held constant at 5.0 milliseconds. The results are used to obtain the dependence of Derived Cetane Number on the volumetric fuel blending ratios. Global equivalence ratios were derived from exhaust gas composition measurements. In addition, the experimental ignition delay results are compared to homogeneous zero-dimensional simulations based on the corresponding global equivalence ratios. Chemical kinetic models validated for autoignition of the aforementioned neat fuels and their blends are used in the simulations. The comparison provides insights into the influence of spray vaporization and fuel-air mixing on ignition delay times in spray combustion.