Non-homogeneous autoignition experimental study for a C3H8/H2 equimolar mixture*

Non-homogeneous autoignition phenomena is a characteristic condition at low temperatures. Flame fronts take place and grow up in the unburned mixture before that volumetric autoignition occurs. An experimental study using a C3H8/H2 equimolar mixture at stoichiometric conditions was carried out to analyze the non-homogeneous ignition in a low-intermediate temperature range (722-865 K) and a fixed pressure (29.3 ± 0.8 bar). The ignition delay time (τ) was measured using the pressure trace in a Rapid Compression Machine. Schlieren images inside the combustion chamber were recorded to perform a qualitative autoignition analysis. Numerical results for τ were obtained using CANTERA. Flame fronts were observed at low temperatures, producing significant disagreement among experimental and numerical results due to high non-homogeneity autoignition. The Sankaran criteria adequately predict the occurrence of non-homogeneous autoignition for the C3H8/H2 mixture. An ignition delay comparison with pure C3H8 suggests that the propane kinetics is still dominant for a 50% H2 fuel addition.