Combustion Fundamentals

Goals!

• Fuel < 50%!

• Emissions < 90%!

• Cost effective!

$100

+ Electricity

+ Fuel choice

= Solution

Complexity/Cost

Complexity/Cost

New understandings &

tools

Design across Scale (m)

0.001 0.01 0.1 1 10 100 1000

Design across Scale (m)

0.001 0.01 0.1 1 10 100 1000

char combustion C + 1/2 O2 ---> CO

gas phase combustion gas + air ---> CO2 + H2O + N2

pyrolysis decomposition of tar

tar ---> gas + char

gas phase combustion gas + air ---> CO2 + H2O + N2

• Formation of undesirable emissions

• Quenching at the wall

• Radiation vs convection heat transfer

gas phase combustion gas + air ---> CO2 + H2O + N2

• Good computational tools are available

• Need experimental validation

• Need reduction to practice

pyrolysis decomposition of tar

tar ---> gas + char

• Rate limiting step

• Source of tars

• fuel and user dependent

Wet Wood

Drying Zone

Pyrolysis Layer

Char Layer

2-3 mm

2-cm particle @ 1500 K

pyrolysis decomposition of tar

tar ---> gas + char

• Combined computational and experimental approach is needed

• Current results can be readily reduced to practice

Examples of designs worth looking at

•  Refractory flameholders for the cooking flame

•  Ceramic fiber burners

•  Turbulence control plates

•  Backward step to trigger high intensity mixing zones