1. Small-scale Combustion Betty Bui ME 258 Fall 2012

2. Introduction Lithium versus Hydrocarbons

3. Small-scale Combustions Advantages More efficient Reduce waste and emissions (CO and NOx) Disadvantages Manufacturing Properties not linear Heat recirculation Heat loss Pollutant formation

4. Categories Definition based on Combustion regime Length scaleExamplesApplications Physical lengthMesoscale1 - 10 mmRotary engine (UCB)MEMS power Microscale1 - 1000 µmMicro-reactor (UIUC)Thruster Flame quenching diameterMesoscale ~Quenching diameter (equilibrium)Swiss-roll combustor (USC)Power generation Microscale Quenching diameter ~ Mean-free path (non- equilibrium) Fuel Cells Nano-particle reactorsEnergy conversion Device scaleMicroscale Smaller than conventional engine size Micro-thrusters (PSU) Micro-gas turbine (MIT) Micro-satellites Micro-air planes

5. Timeline of Development 1998: Waitz – 1 st micro-combustor of 0.13cm 3 2002: Weinberg – Swiss Roll Combustor 2002: Sirignano – Liquid fuel flow directly on walls 2003: Liedtke and Schultz – Liquid film in annulus around tube 2004: Kaiser and Kyritsis – Meso-scale catalytic combustor via electrostatic spray 2004: Wang – Swirl-stabilization combustion 2005: Anh - Gas-phase and catalytic combustion in Swiss-Roll 2005: Spadaccinni – Hybrid micro-combustor 2005: Yuasa – Flat-flame micro-combustor 2006: Marbach and Agrawal –Porous inert material

6. Approaches Excess Enthalpy Regenerative preheating Redistribute thermal energy Minimizing heat losses Heat Exchanger Counter-flow current Heat Transfer Convection Radiation

7. Swiss Roll Combustor (SRC) Combustion Chamber Pair of long channels

8. Porous Inert Media (PIM) Two concentric cylinders Preheated reactants in annulus prior to PIM

9. Conclusion Swiss-roll combustor and Porous Inert Media Excess Enthalpy Regenerative Reheating Heat transfer modes Leaner combustion Reduced emissions

10. Questions?