Numerical Study On Flame Stabilization In A Planar Micro Combustor With A Bluff Body

Combustion–based micro power generation devices and systems are considered to be potential alternatives due to the much higher energy densities of hydrocarbon fuels as compared with the batteries. Flame stabilization is one of the key issues for combustion-based micro power generation devices. In the present work, based on a comprehensive analysis of the advantages and disadvantages of current flame stabilization techniques for micro combustion, we proposed the application of a bluff-body stabilizer which is being widely used in conventional scale combustions.Systematic numerical simulations were performed by using the commercial CFD software package, Fluent 6.3.26. Detailed chemistry of H2/O2 premixture are considered in the computations. Comparisons were made between the combustion characteristics of the planar micro-combustors w/o a bluff body. Special attentions were paid to the blow-off limit, combustion efficiency, temperature distribution, and flame structure. The major results are given below:(1) For the case without a bluff body, the blowoff limit decreases linearly with the decrement of the mixture equivalence ratio; while for the case with a bluff body of suitable dimension, the blowoff limit was extended by 2-3 times. Furthermore, the blowoff limit of the planar micro combustor with a bluff body maintains almost constant in a wide equivalence ratio range. However, when the equivalence ratio is less than 0.5, the blowoff limit decreases sharply.(2) Under the near-blowoff suituations, flame in the planar micro combustor without a bluff body exhibits asmetric structure, while flame still remains symmetric under near-limit conditions in the case with a bluff body.(3) In both types of combustors, the combustion efficiency increases first, and then dereases with the increment of the inlet mixture velocity or the equivalence ratio. But the combustion efficienty is higher for the case with a bluff body under suituations of relatively high inlet velicities.(4) The addition of the bluff body leads to more uniform and symmetric wall temperature distribution, which reaches a highest level in the case of a stoichiometric mixture.(5) The dimension of the bluff body has a great effect on flame stability, combustion efficiency and the uniformity of the wall temperature distribustion. A relatively larger blockage ratio results in a better flame stabilization. When the blockage ratio is less than 0.3, the bluff body loses its ability of flame stabilization.In the final section of this thesis, we designed the experimental system and discussed the experimental scheme, which laid a foundation for our future study.