Dynamics of (CDynamics of (C66HH1212OO66))nn

Propulsion During Alkane Propulsion During Alkane Combustion in an Adiabatic Combustion in an Adiabatic

ReactorReactor

What makes the spud fly?What makes the spud fly?

Who Are These People?Who Are These People?

Those who take all precautions to Those who take all precautions to minimize bodily risk?minimize bodily risk? NoNo

Voted “Most Likely to be Maimed” by Voted “Most Likely to be Maimed” by their classmates?their classmates? MaybeMaybe

Organ Donors?Organ Donors? SomedaySomeday

Combustion KineticsCombustion Kinetics(The Chemistry of Boom)(The Chemistry of Boom)

Simple Combustion of Methane Simple Combustion of Methane (Natural Gas)(Natural Gas)

CHCH44 + 2O + 2O22 CO CO22 + 2H + 2H22O + EnergyO + Energy

Can be Autocatalytic Under Proper Can be Autocatalytic Under Proper CircumstancesCircumstances

Combustion KineticsCombustion Kinetics

Reactions Can be Autocatalytic if:Reactions Can be Autocatalytic if: Heat of Reaction is High EnoughHeat of Reaction is High Enough Rate of Reaction is Fast Enough to Heat Rate of Reaction is Fast Enough to Heat

Up Surrounding GasUp Surrounding Gas Heat of Reaction is Determined by Heat of Reaction is Determined by

ChemistryChemistry Rate of Reaction Can be ControlledRate of Reaction Can be Controlled

Simple Combustion of MethaneSimple Combustion of Methane

CHCH44 + 2O + 2O22 CO CO22 + 2H + 2H22O + EnergyO + Energy

If CHIf CH44 << 2O << 2O22, Reaction is Slow, Reaction is Slow Autocatalysis UnlikelyAutocatalysis Unlikely

If CHIf CH44 >> 2O >> 2O22, Reaction is also Slow, Reaction is also Slow Autocatalysis UnlikelyAutocatalysis Unlikely

Need Proper Proportion of Fuel and Need Proper Proportion of Fuel and OxygenOxygen

Combustion TermsCombustion Terms

Lower Explosion LimitLower Explosion Limit Volume Percent of Fuel in Air Where Volume Percent of Fuel in Air Where

Autocatalysis Begins (Minimum Lean)Autocatalysis Begins (Minimum Lean) Upper Explosion LimitUpper Explosion Limit

Volume Percent of Fuel in Air Where Volume Percent of Fuel in Air Where Autocatalysis Ends (Maximum Rich)Autocatalysis Ends (Maximum Rich)

Stoichiometric ProportionStoichiometric Proportion Volume Percent of Fuel in Air Where Volume Percent of Fuel in Air Where

Oxygen and Fuel are in Exact Oxygen and Fuel are in Exact Combustion ProportionCombustion Proportion

0

1

2

3

4

5

0 5 10 15 20

Volume % Fuel

En

erg

y R

elea

se,

kJ/L

Methane

Propane

General Fuel EnergyGeneral Fuel Energy

Methane CHMethane CH44 – – 890 KJ/mole 890 KJ/mole Propane CPropane C33HH88 – – 2220 KJ/mole2220 KJ/mole Acetylene CAcetylene C22HH22 – – 1299 KJ/mole1299 KJ/mole

Calculating the Energy ReleaseCalculating the Energy Release

Calculate the Volume of Gas in Calculate the Volume of Gas in Chamber:Chamber: V = pi (DV = pi (D22/4) L/4) L

Inject a Volume VInject a Volume Vff of Fuel in Chamber of Fuel in Chamber Volume of Air in Chamber:Volume of Air in Chamber:

VVairair = V – V = V – Vff

Calculate Moles of Air and Fuel:Calculate Moles of Air and Fuel: NNff = P V = P Vff/(RT) Ideal Gas Law/(RT) Ideal Gas Law

Calculate Energy ReleaseCalculate Energy Release

Calculate Moles of Oxygen in ChamberCalculate Moles of Oxygen in Chamber NNoxygenoxygen = 0.21 N = 0.21 Nairair

Determine if Oxygen or Fuel is Limiting Determine if Oxygen or Fuel is Limiting Reagent:Reagent: CC33HH88 + 5 O + 5 O22 3CO 3CO22 + 4H + 4H22OO

Calculate Maximum Amount of Fuel Calculate Maximum Amount of Fuel ReactedReacted

Calculate Energy ReleasedCalculate Energy Released

Rules of ExperimentRules of Experiment

Safety, Safety, SafetySafety, Safety, Safety Vary Volume of Fuel and Measure Vary Volume of Fuel and Measure

Distance Potato TraveledDistance Potato Traveled Determine Kinetic Energy of Potato Determine Kinetic Energy of Potato

Leaving the Barrel of CannonLeaving the Barrel of Cannon Compare with Combustion EnergyCompare with Combustion Energy