2.1 Experimental setup and method
The geometric diagram of the planar mesoscale combustor is schematically shown in Fig. 1. The total length (L0) is 70 mm and the wall thickness (W3) of the combustor is 2 mm. The width (W0) and height (W1) of the combustor chamber are 20 mm and 4 mm, respectively. The cross section of the bluff-body is an equilateral triangle with a side length (W2) of 2 mm. The bluff-body is symmetrically located with respect to the upper and lower walls of the combustor, and the distance from its vertical surface to the combustor inlet (L1) is 10 mm. Both of the combustor walls and the bluff-body are made of quartz glass which can endure a very high temperature.
The experimental system is schematically shown in Fig. 2. Methane and air of high pressure were stored in two gas tanks. Their pressures were reduced to atmospheric pressure by using pressure-reducing valves, whilst the inlet velocity, Vin, and the equivalence ratio, f, were controlled by electric-mass-flow meters with an accuracy of 1% over the full range. The fuel and air streams were fully mixed before entering into the combustor. An electric spark igniter was applied to ignite the fresh mixture. …show more content…
For example, periodic transitions between inclined flame and tulip-like flame (bended in the middle) takes place at f= 0.8, Vin= 0.7 m/s, as shown in Fig. 6a. Meanwhile, dynamics of the inclined flame are captured at f= 0.7, Vin= 0.5 m/s, as depicted in Fig. 6b. The common feature of these two flame dynamics is that their frequency is very low and they can be clearly observed with the naked eyes. The difference between these two cases is that the flame does not bend in the middle for f= 0.7. These two dynamic processes demonstrate that the flame front is prone to be blown away from the bluff-body when the equivalence ratio is