Numerical investigation on the combustion characteristics of methane/air in a micro-combustor with a hollow hemispherical bluff body

•A micro-combustor with a hollow hemisphere bluff body is developed.•Blow-off limit of reactor is expanded 2.5 times by the hollow hemisphere bluff body.•Methane conversion rate of combustor sharply increases at the location of bluff body.•Methane conversion rate is mainly affected by equivalence ratio and inlet velocity.•Recirculation zone expands blow-off limit and increases methane conversion rate. The combustion characteristics of methane in a cube micro-combustor with a hollow hemispherical bluff body were numerically investigated. The blow-off limit, recirculation zone length and methane conversion rate were examined. The results illustrate that the blow-off limit of the micro-combustor with a hollow hemispherical bluff body is 2.5 times higher than that without bluff body, which are 24.5m/s and 9.5m/s at the same equivalence ratio (ϕ=1), respectively. With the use of hollow hemispherical bluff body, methane conversion sharply increases from 0.24% to 17.95% at 3mm along the inlet-flow direction, where is the location of bluff-body, which is not affected by equivalence ratio and inlet velocity. The recirculation zone size has determined influence on residence time of the mixture gas, which increases with the increase of inlet velocity. Methane conversion rate is determined by equivalence ratio and inlet velocity. Methane conversion rate firstly increases and then decreases when the equivalence ratio and inlet velocity increase, reaching the maximum value (97.84%) at ϕ=1 and 0.02m/s. Methane conversion rate sharply increases from 45% to 97.84% when the inlet velocity increases from 0.008m/s to 0.02m/s.