Laminar burning velocity measurements in constant volume vessels – Reconciliation of flame front imaging and pressure rise methods

Abstract

Laminar burning velocity measurements have been made in a constant volume vessel using both flame front imaging and the pressure rise methods. Results from the two different methods are shown to be the same, so long as appropriate techniques are used for analysing the data. Comparisons are presented for the laminar burning velocity of mixtures with air of methane, ethanol and biogas (60% methane, 40% carbon dioxide) for a wide range of flammable mixtures at pressures of 2 and 4bar and temperatures of 380 and 450K.Methods for measuring the laminar burning velocity are still the subject of controversy, with different researchers favouring different approaches. Open flame techniques are very popular and the so-called heat flux method is now well established. The alternative technique of using a constant volume combustion vessel is also in common use, and has two distinct methods of use: either the imaging of flame front propagation at conditions of constant pressure, or the measurement of the pressure rise combined with a constant volume combustion model. The pressure rise method requires a more complex analysis, but has the advantage that a single experiment generates data across a range of linked temperatures and pressures, and the pressure and temperature rise also mean that data can be obtained for engine-like conditions.