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

2. 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

3. 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

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

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

6. 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

7. 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

8. 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