Laminar burning speeds of ethanol/air/diluent mixtures

Laminar burning speed of ethanol/air/diluent mixtures have been measured over a wide range of temperature, pressure, fuel air equivalence ratio and diluent. Experimental facilities include a cylindrical vessel with two large end windows and a spherical vessel with capability to withstand pressures up to 425atm. Both of these vessels are heated for having initial temperatures of unburned gas up to 500K. A shadowgraph system with a CMOS camera capable of taking pictures up to 40,000frames/s is used to observe structure of propagating flames. Pressure rise due to combustion in both vessels is used to calculate laminar burning speed of the mixture. A thermodynamic model is used to calculate burning speed from combustion pressure. Laminar burning speeds of ethanol/air premixed mixtures have been measured at high temperatures and pressures. A mixture of 86% nitrogen and 14% carbon dioxide, which simulate heat capacity of residual gases in internal combustion engines, is used to determine the effect of diluent on burning speed. A correlation for laminar burning speed as a function of temperature, pressure, equivalence ratio and extra diluent gas (EDG) has been developed. The range of temperature and pressure are 300–650K and 1–5atm, fuel air equivalence ratio 0.8–1.1 and extra diluent gases of 5% and 10%. The measured values compare very well with available data and extend the range many folds.