High-pressure laminar burning velocity measurements of ethanol- a Co-Optima fuel candidate 2020-01-0332
Co-Optimization of Fuels and Engines initiative (Co-Optima) of the U.S Department of Energy initiated investigations on several candidates of biofuels and blends for internal combustion engines. Several biofuels were selected by screening criteria, which were boiling point, toxicity, research octane number, octane sensitivity, laminar flame speed, and economical distribution system, etc. In this study, we focused our investigation on ethanol – a key fuel candidate. Measurements of properties such as ignition delay time and laminar burning velocity (LBV) are necessary for these fuels in order to understand their performance and applicability in engines. One key combustion metric is the fuel’s LBV in air over a range of equivalence ratios. LBV is dependent on reactive mixture composition, temperature, and pressure, but it is independent of hydrodynamic conditions, such as stretch rate, turbulent intensity, and Reynolds number. LBV is useful as it: (i) gives a measure of combustion efficiency and heat release rate; (ii) enables validation of chemical kinetic mechanisms; (iii) and gives engine design engineers a metric for the expected time required to burn the fuel charge within a cylinder. Furthermore, in order to quantify more complicated, and practical, burning regimes such as turbulent combustion much of the underlying theory requires knowledge of LBV. While there exist many studies for ethanol under atmospheric conditions, there are only few studies on combustion characteristics at high pressures in the literature. Here we present measurements of laminar burning velocities of ethanol up to an initial pressure of 10 atm and initial temperature of 428 K. Equivalence ratio was varied in a wide range to examine the effects on laminar burning velocity. The results presented are also compared with the performance of detailed kinetic models as part of their validation process. The kinetic model is used to explore the source of the differences in the observed laminar burning velocities of the fuels.
Gihun Kim, Anthony Terracciano, Subith Vasu, Bader Almansour
University of Central Florida, Public Authority for Applied Education & Training