Hi all,

I am working with a group on "Flare-Radiation Study Project" for an existing platform. And I am given an excel-spreadsheet created by someone else to calculate the 3D points radiation data for the current flaring data. First thing I am asked to validate the spreadsheet for Project use which I almost have finished doing except the Flame length calculations.
it uses following three terms & res. formula which I couldn't find in API/GPSA, etc.
I would greatly appreciate any guidance/help to validate the source/s of those formulas/equations.

API FLAME LENGTH: 0.00604*(heat release)^0.4776

SONIC FLAME LENGTH: 0.004503 * (heat release)^0.459882

EFFECTIVE FLAME LENGTH: (1- Tip MACH Number) *API Flame Length + (Tip MACH Number * Sonic Flame Length)


I refered API 521 (2007), it uses a plot betn flame length & heat release (fig.7 & 8) & its based on some plant-scale experimental work on flames; is there any empirical equation for it?

Does anyone have any information for me?

Thanks & Regards,

Milton Beychok fitted the datapoints from API STD 521 in his book "fundamentals of stack gas dispersion". The result for flame height is shown on the Book cover :

hfv = 0.0042*Q^0.478

Q is heat released (lower heating value) in BTU/hr
hfv is flame height in feet

Since he assumed a 45 degrees angle, the flame length is:

flame length = 0.0059*Q^0.478

(note that 0.0059=0.0042*sqrt(2))

which is very similar to your first equation. Probably someone else curve fitted this equation on the datapoints read from the API 521 graph (figure 8 on page 82).

I don't know what you mean with sonic flame length or effective flame length.

Have you tried Thermal Analyser software? It is widely used in Calculations for Flare Systems.

Thanks gvdlans,

Pretty Knowlegable and to the point person:

Thank you so much gvdlans!

thats really helpful.
I am trying define the term "SONIC FLAME LENGTH" used in the calculations which is not present in API but not getting a clue.
Please let me know if you can guide on it too.
Once again thanks a ton!

50 GJ/Hour Flare

Dear All. I am trying to design a 50 GJ/Hr(1100 Kg/Hr Dry Methane) in a 2 Meter2 Cross Section and 10 meters height with a residence time of around 1.5 seconds.

I did the draught flow rate(assuming inside temperature is maintained at 550 Degree"C") and outside temperature is 20 degree "C".(using the standard draught calculation formula::0.65*Area*Sqrt(2gH(Ti-Te/Ti)). which gives a draught speed of 13.5m3/sec.

However this puts me at wrong feet:: If sweept speed is 13.5m3/sec than the residence time will be down to 1 second or near by(keeping the height of stack 10 meters in mind).

Any "smart person", to help on this. Is 10 Meters Height and 1.3 Meters Diameter Stack is Fine.

Hi Deppali

Sonic flows correspond to lowest stack diameter in flow rate range.

Hope this leads you in right direction[/size]

Thanks Shanesheoran!