Direct prediction of laminar burning velocity using an adapted annular stepwise diverging tube

In a combustion study, laminar burning velocities of premixed flames are essential data. A number of experimental results for various fuels have been reported. Although there are many reliable experimental methods that provide precise burning velocities, these methods are not suitable for in situ monitoring in the field. In response to this limitation, a method using an annular diverging tube (ADT) was introduced in the previous study, and its feasibility was verified. In this study, an advanced technique using an annular stepwise diverging tube (ASDT) was introduced to enhance flow uniformity and to formulate flatter flames in the majority of experimental conditions. The configuration of the burner was gradually improved based on their flame propagation characteristics. An adapted burner configuration was developed and used to predict the laminar burning velocities of methane, propane, and DME. Two types of measuring methods were compared: a transient method, which was similar to the previous study, and a static method, which was used for a direct prediction of burning velocity. The static method predicts similar burning velocities when compared to the transient method. The results of both methods were sufficiently similar to the other's previous results. Quenching distances could also be directly predicted using this adapted ASDT system. Therefore, the static method may be the easiest and fastest method to predict burning velocity, and quenching distance at the instant. This method can be applied to the energy field and aid in the understanding of flame characteristics in narrow combustion spaces.