Stoichiometric fuel ratio =λ

[Met.Eng.]

Hi members,

I have a specific question about stoichiometric fuel ratio "λ" for HVOF system.

The stoichiometry of the combustion is indicated with a standardised oxygen-fuel-proportion λ = 1. For ex. the process parameters 800 slpm oxygen and 20 l/h kero-sene . As you know propane, etylene.. ect has different flows and parameters.

For exaple Kerosene:
C12H23 + 17.75 O2 12 CO2 + 11.5 H2O
λ = 1 O2=800 slpm Karosene=20

For ex. Woka 3102 powder's, Metco gives some reccomended spray parameters about kerosene. They said the stoichiometric fuel ratio must be λ=1,15. And they give karosene slpm and O2 slpm."Oxy 900 slpm Kerosene 23 slpm". This ratio is 900 slpm Oxygen and 23 slpm kerosene as a result of the multiplication. (approximately; 800x1,15 and 20x1,15).

1.Can we use this ratio for other oxy-fuel processes? For example propane, etylene or other gases

2.What is the reason this ratio to be greater than 1? (λ=1,15)

3.Did they determining this rate according to the "Prandtl-Meyer expansion " theory.

[Gordon]

Hi Metallurgy_eng

1.Can we use this ratio for other oxy-fuel processes? For example propane, etylene or other gases

Not really, as different fuels can have different oxygen requirements to achieve a "normal or neutral flame" and maximum flame temperature. Lets take acetylene - neutral flame requires about 45% oxygen, max flame temp about 58% (100% oxygen for complete stoichiometric combustion). Compare to propane - neutral flame about 75%, max flame temp about 85%.

2.What is the reason this ratio to be greater than 1? (λ=1,15)

The "normal or neutral flame" and maximum flame temperature occur on the fuel rich side of stoichiometric mix. Acetylene being the more extreme.

3.Did they determining this rate according to the "Prandtl-Meyer expansion " theory.

I think this is more from experiment than theoretical. Theoretical may well be used in initial equipment design, nozzle shape etc though