A numerical study on the blow-off limit of premixed hydrogen/air flames in a cylindrical micro-combustor

Abstract

In the current work, a numerical study on combustion of premixed H2–air in a micro-cylindrical combustor was carried out and the critical velocity of inlet flow that causes the blow-off was obtained. Furthermore, the effects the equivalence ratio, wall thickness, geometry of combustor and thermal properties of walls on the critical blow-off velocity were studied. The numerical results showed that, increasing the equivalence ratio results in higher critical blow-off velocity. A micro combustor with thicker wall had better flame stability. As the combustor dimeter is decreased the blow-off occur in lower inlet flow velocity. Higher thermal conductivity of walls increases the critical blow-off velocity. In addition, with varying heat convection coefficient (h) and emissivity coefficient [Formula: see text] of the walls from 1 to 60 W/m2.K and 0.2 to 0.8 respectively, the critical blow-off velocity is reduced and shows the importance of wall thermal properties in the design and operation of micro-combustors.

Numerical investigation of the effect of the slit profile on the combustion characteristics of a micro-combustor with a centrally slotted bluff body

“…The advent of miniaturization coupled with the declining energy resources is increasing the need for efficient compact power generators. A wide range of portable power generation applications demand the combustion of high energy density fuels such as hydrogen and hydrocarbons in relatively narrow channels such as micro or meso scale channels, 1,2 swiss-roll combustors 3,4 etc. Micro-combustors are being used as a source of thermal energy in micro thrusters, micro turbines, micro thermo-electric systems, micro thermo-photovoltaics etc.…”