Improvement in the annular stepwise diverging tube for laminar burning velocity and quenching distance

Abstract

Laminar burning velocity and quenching distance of a premixed flame are essential data. Many experimental methods for measurement of them have been introduced and a huge number of data has been reported. However, most of the previous studies were not suitable for an in situ monitoring in the field. Be aimed at this aspect, a method using an annular stepwise diverging tube (ASDT) was introduced in the previous study, and its feasibility was verified. In this study, an improvement in the ASDT was achieved in two aspects. First, each step unit of the ASDT was fabricated separately. Thus, the resolution of each unit could be improved, and various compositions of step units could be possible. Second, a thin metal ring was used to formulate a thin cavity at every step. Thus, the heat transfer to the upstream could be reduced, and the experimental period could be extended. The effect of different step arrangement was compared. Using one of the assembled ASDT, laminar burning velocities and quenching distances of methane were predicted. Conclusively, the performance of the assembled ASDT was very good. The experimental resolution could be easily controlled by just assembling suitable step units. Therefore, this method is the fastest and easiest method to predict laminar burning velocity and quenching distance especially at the field. This method is also useful for understanding of flame characteristics in narrow combustion spaces.