Modelling of Combustion and Heat Transfer in ‘Swiss Roll’ Micro-Scale Combusters M. Chen and J. Buckmaster Combustion Theory and Modelling 2004 Presented By: Katy Meyer May 1, 2006

Introduction Potential replacement for batteries in micro-electro-mechanical systems Use micro-scale combustion as power source Benefits: Longer life, lighter weight, can be refueled Challenges: Heat loss, extinction Swiss Roll Counter-flow Combustors Re-circulate thermal energy, extending extinction limit

Figure 1. Schematic of Swiss Roll Combustor Numerical Modelling Swiss roll unwrapped into straight channel Considers convective heat transfer from re-circulated gases Radiation heat exchange modeled as two infinite parallel plates In conduction simulation, temperature gradient in the wall is neglected Energy equation in each wall First Order Runge-Kutta Steady State Figure 1. Schematic of Swiss Roll Combustor

Results Figure 2. Response of Wall Temperature and Reaction Rate along Centerline

Figure 3. Re = 100 (a) Modes of Heat Transfer (b) Gas Temperature Profiles in y-direction

Figure 5. Varied Reynolds Number and impact on (a) gas temperature, (b) wall temperature, and (c) reaction rate Figure 6. Varied Equivalence Ratio and impact on (a) gas temperature, (b) wall temperature, and (c) reaction rate

Figure 7. Emissivity vs. Extinction Limit for various Reynolds numbers Figure 8. Thermal Conductivity vs. Extinction Limit for various Reynolds numbers Figure 9. Reynolds Number vs. Extinction Limit for various channel heights

Conclusions Stable combustion in micro-scale combustors is possible due to recirculation provided by SRC’s Effectively high extinction limits achieved Numerical results for extinction limit at relatively low channel heights 3.5, 1.0, 0.5 mm Most significant parameters that affect extinction limit Reynolds number Equivalence ratio Thermal Conductivity/Wall Thickness Emissivity