Development of Ultra-Micro Combustor Using Cylindrical Flames

Abstract

The purpose of this study is to develop an ultra-micro combustor that uses two types of coaxial cylindrical flames, rich premixed flame and diffusion flame. The combustor consists of inner and outer porous tubes, and rich propane-air mixture and air issued, respectively, through the inner tube outwardly and through the outer tube inwardly, forming a cylindrical stagnation plane sandwiched by the inner rich premixed flame and the outer diffusion flame. Petal type flame was also observed in the downstream of the cylindrical flames. Keeping the equivalence ratio φ i and flow rate q i of the rich mixture constant, air flow rate q a was varied. The O 2 and CO concentrations and temperature of the burnt gas were measured, and heat loss rate η hl and combustion intensity L were evaluated. The obtained results are described as follows. (1)The relation curve of η hl with the overall equivalence ratio φ all , which is evaluated from the total flow rate of the fuel and the air, has a minimum value.(2)The relation curve of the minimum value of η hl with L has a minimum value. (3) The CO concentration of the burnt gas increases as q a is increased because of local extinction of the petal type flame. (4)When q a is increased further, petal type flame is also extinguished. After that, the O 2 concentration increases and the CO concentration decreases.

Combustion characteristics of an annular type meso-scale combustor

“…However, the curves of φi = 3.0 and 4.0 are at a minimum at φall = 0.7 and 0.8, respectively. Such results relate closely to the extent of local quenching, and are also observed in our previous studies (Suenaga et al, 2010b(Suenaga et al, , 2011b. In the same φall, ηhl decreases with an increase in φi.…”

“…Application of this flame strengthening effect to the combustion in a very small domain is effective in downsizing the combustors. Therefore, we developed an annular type combustor that can form the cylindrical flame, and conducted research experiments (Suenaga et al, 2010b(Suenaga et al, , 2011b. Our combustor consists of inner and outer porous tubes.…”

A numerical study of propane-air combustion in meso-scale tube combustors with concentric rings

“…An experimental study has shown that flame stabilization in a confined space or a narrow channel is achievable (Miesse, et al, 2004). However, the difficulty of sustaining a stable flame for a micro combustor due to its high surface to volume ratio is a major issue in micro combustion (Suenaga, et al, 2011;Maruta, 2011). This high ratio causes a large portion of heat loss from the flame to the wall, which leads to thermal quenching (Kaisare, et al, 2012).…”