Experimental Study On The Micro Flame Characteristics Of Hydrocarbon Fuels In A Plate Slit

With the development of MEMS technology, and the rapid development of commercial portable devices and micro air vehicles, people put forward higher requirements on the high energy density of portable micro energy systems. Different from the conventional scale burner, the characteristic size of the micro combustor is in the millimeter scale, and the surface-to-volume ratio of the micro combustor is increasing rapidly. It causes some difficulties for the micro scale combustion, such as short reaction time, large wall heat loss, and the influence of chemical extinction, which will cause the instability and even extinction of micro scale flame.In this paper, the experimental study on the micro flame characteristics of different hydrocarbon fuels in a plate slit was investigated, the mechanism of flame instability and extinction in micro channel is explored, and the combustion phenomenon and theory of micro scale flame are further improved.A uniform plate slit flame burner was used to measure the quenching distance of different fuels. The flame quenching distance of the methane/air premixed flame is greater than that of n-butane/air premixed flame, propane/air premixed flame quenching distance is less than that of n-butane/air premixed flame, ethane/air premixed flame quenching distance is the smallest. The factors that affecting the flame quenching distance were analyzed. The higher the wall temperature, the smaller the heat loss of the flame which result the decrease of the quenching distance. The higher the equivalence ratio, the more intense the combustion reaction, and the smaller the quenching distance. With the increase of premixed gas velocity, the quenching distance of the flame is first decreased and then stabilized.A high speed camera was used to observe the dynamic of the flame. As the distance between the plates decreases, the flame has experienced three main stages. In the first stage, the flame is in a steady state, with the decrease of the distance between the plates, the position of the flame is gradually increased. In the second stage, the flame is in the regular oscillating stage, and the oscillating frequency of the flame is independent of the distance between the plates. The third stage, the flame is extinguished. When the distance between the plates is less than the quenching distance of the flame, the flame can not be maintained in the oscillating state and extinguished. The oscillating frequency of different fuels is compared. The oscillating frequency of different fuel/air premixed flame is in the order from large to small, ethane and propane, n-butane, methane. The range of different fuel/air premixed flame in oscillating state is in the order from large to small, n-butane, Propane and ethane, methane.planar laser induced fluorescence(PLIF) was used to study the distribution of OH in the flame of different fuels with in different distance between the plates. As the distance between the plate decreases, the maximum OH concentration decreases, and the maximum OH concentration increases with the increase of wall temperature. In addition, the influence of the distance between the plates on the flame position is also studied. With the decrease of the distance between the plates, the flame position remains stable. When the point is reached, the flame moves downstream fast. The higher the wall temperature, the closer the flame position to the nozzle.The research of this paper enriches the micro scale combustion theory, and provides the data support for the micro scale combustor design, which lays the foundation for the effective improvement of the operation stability of micro energy power system.