Spray Analysis of C ₈ H ₁₈ O Fuel Blends Using High-Speed Schlieren Imaging and Mie Scattering

Targeted fuel blending is a known method to improve the performance of an automotive engine. Two candidates for a biofuel blend are the linear C₈H₁₈O isomers 1-octanol and di-n-butyl ether (DNBE). Both fuels feature an increased amount of oxygen that reduces soot emissions. However, physical properties of both fuels differ significantly and thus, a different type of spray mixing and combustion is expected: The low reactivity of 1-octanol causes a long ignition delay enabling a better mixture homogenization, but also causes HC and CO emissions. DNBE in contrary is highly volatile, has a short ignition time and thus can act as an ignition booster for 1-octanol without losing positive effects concerning emissions. In this work a spray study is performed for blends of 1-octanol and DNBE. Measurements are conducted under diesel-like engine conditions with an 8-hole piezo injector. High-speed Schlieren and Mie scattering techniques are used for spray visualizations. The recorded images allow an extraction of the macroscopic spray dimensions, i.e. penetration and cone angles of both, liquid and vapor phase. The results show a significant influence of the blend composition on the liquid spray phase, whereas the outer boundaries of the vapor phase remain unchanged.