Structural design of a silicon six-wafer micro-combustor under the effect of hydrogen/air ratio

This paper studied the structural design issues associated with a silicon six-wafer micro-combustor under the effect of hydrogen/air ratio. The objective of this study is to establish a methodology for designing highly stressed micro-fabricated structures. Due to the facts that there are differences in sizes between a micro-combustor and a conventional combustor, the fracture strength of silicon in room temperature is extremely sensitive to its surface processing methods. It is worth noting that the silicon has relatively poor high temperature strength and creep resistance when the temperature is above the brittle to ductile transition temperature (BDTT), e.g. 900K [1]. Some experimental and numerical simulation results [1,2] have shown that the flame front in the micro-combustor propagates in the upstream of the mixture flow, burns in the recirculation jacket, where the flame temperature could reach 1700-1800K, and then travels to the outer wall 1000 - 1200K when the equivalence ratio of hydrogen/air is increased to a certain value. This will shorten the fatigue life of the micro-combustor. In order to explore the structural design of the microcombustor under the effect of different mixture equivalence ratio, combustion characteristics of the combustor were first analyzed using 2D computational Fluid Dynamics (CFD) simulation when the mixture flow rate was constant, and then the 3D Finite Element Method based on Finite Element Software COSMOS\works was employed for thermomechanical analysis. The results show that the critical failure occurs around the burning area in the recirculation jacket, which is in agreement with the experimental results in the published literature. The results of this study can be used for the design and improvement of the micro-combustors.