Small-scale CombustionBetty BuiME 258Fall 2012

Introduction• Lithium versus Hydrocarbons

Small-scale Combustions• Advantages• More efficient• Reduce waste and emissions (CO and NOx)

• Disadvantages• Manufacturing• Properties not linear

• Heat recirculation• Heat loss• Pollutant formation

Categories

Definition based on

Combustion regime

Length scale Examples Applications

Physical length Mesoscale 1 - 10 mm Rotary engine (UCB) MEMS power

Microscale 1 - 1000 µm Micro-reactor (UIUC) Thruster

Flame quenching diameter Mesoscale

~Quenching diameter (equilibrium) Swiss-roll combustor (USC) Power generation

Microscale

Quenching diameter ~ Mean-free path (non-equilibrium)

Fuel Cells Nano-particle reactors Energy conversion

Device scale MicroscaleSmaller than conventional engine size

Micro-thrusters (PSU)Micro-gas turbine (MIT)

Micro-satellites Micro-air planes

Timeline of Development• 1998: Waitz – 1st micro-combustor of 0.13cm3

• 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

Approaches • Excess Enthalpy • Regenerative preheating • Redistribute thermal energy• Minimizing heat losses

• Heat Exchanger• Counter-flow current

• Heat Transfer• Convection• Radiation

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

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

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

Questions?