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 425 atm. Both of these vessels are heated for having initial temperatures of unburned gas up to 500 K. A shadow-graph system with a CMOS camera capable of taking pictures up to 40,000 frames/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 300-650 K and 1-5 atm, 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. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.