Small-scale Combustion Betty Bui ME 258 Fall 2012.
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Transcript of Small-scale Combustion Betty Bui ME 258 Fall 2012.
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?