Stoichiometric fuel ratio =λ
01-07-2011, 09:18 PM, (This post was last modified: 01-07-2011, 09:45 PM by Met.Eng..)
#1
Stoichiometric fuel ratio =λ
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.
Reply
01-14-2011, 08:44 PM,
#2
RE: Stoichiometric fuel ratio = λ
Hi Metallurgy_eng

Quote: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%.

Quote: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.

Quote: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 Smile
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