A Novel Approach for Accurate Determination of Laminar Burning Velocity Using the Constant Volume Method in a Cylindrical Vessel with Full Optical Access

Abstract

ABSTRACT The constant volume method (CVM) is a potential method for determining laminar burning velocity (LBV) at high pressures and temperatures. However, CVM using spherical vessels gives no optical access to the flame; in cylindrical vessels, with full optical access, the flame does not remain spherical. In either case, one has to rely on semi-analytical models, which have limitations in accuracy, to obtain burned gas volume (BGV) needed for LBV calculation. This study presents a novel approach for accurate determination of BGV and flame surface area (FSA) of non-spherical flames in cylindrical vessels from the measured end-view flame radius. Through CFD simulation, normalized relationships are developed to relate the measured flame end-view radius to the actual FSA and BGV. It is shown that these relationships are purely geometry-dependent and are independent of vessel size and combustion reactions in the vessel. This facilitates accurate determination of LBV using CVM in an optically accessible cylindrical vessel, eliminating the requirement to estimate burned gas mass fraction using burned gas mass fraction models. Experiments using CVM were performed for a stoichiometric methane-air mixture at 1.0 bar and 300 and 350 K. This new approach is demonstrated by using it to determine the LBV of stoichiometric methane-air mixture accurately. The present methodology is expected to provide a way to calculate accurate LBV without the need for additional thermodynamic models for burned gas mass fraction.