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looking for Spindt AFR calculation

looking for Spindt AFR calculation

looking for Spindt AFR calculation

(OP)
Can anyone provide the equation for calculating air fuel ratio based on exhaust gas emissions (CO, CO2, HC, and O2)?
Thanks much.

RE: looking for Spindt AFR calculation

You need to write the chemically balanced equation making an assumption for the fuel composition (usually octane for gasoline).  This will be an approximation, of course.

Mike

RE: looking for Spindt AFR calculation

gsz
 I tackled this some months ago, there's a little bit on it in Heywood, I'll see if I can dig something up tommorow- if I don't get back to you, it's because I'm either too busy, or can't find the equations *L*

RE: looking for Spindt AFR calculation

(OP)
Thanks. Found it in my archives. (SAE paper 650507). In VB in looks like this:

Function spindtAFR(O2percent, COpercent, CO2percent, HCppmC, HCratio)

O2 = O2percent
CO2 = CO2percent
CO = COpercent
HC = HCppmC

q = O2 / CO2
r = CO / CO2
Fb = (CO2 + CO) / (CO2 + CO + (0.0001 * HC))
Fc = 12.01 / (12.01 + 1.008 * HCratio)
spindtAFR = Fb * ((11.492 * Fc * ((1 + 0.5 * r + q) / _
            (1 + r))) + ((120 * (1 - Fc)) / (3.5 + r)))

End Function

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