[Stoves] venturi system -ratios of air and gas?

[Philip Lloyd]

Pure propane is 81.8% C, 11.2% H by mass - no O. Most commercial propane has
a bit of ethane and a bit of butane in it, but not enough to alter this
ratio drastically.

Philip 

-----Original Message-----
From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Crispin Pemberton-Pigott
Sent: 08 January 2016 05:26
To: 'Discussion of biomass cooking stoves'
Subject: Re: [Stoves] venturi system -ratios of air and gas?

Dear Investigators

What is the analysis of the propane that you consider 'typical'?

If you can suggest a C, H, O % by mass, I can tell you the volume based on
whatever excess air requirement you think is necessary. 

It is likely that a propane flame is not premixed. A natural gas flame
probably is. Being pre-mixed doesn't mean it is 100% supplied, only that it
is an aid-enriched gas mix that is depending on available air near the flame
to complete combustion.

I have some LPG formulations kicking around from India, South African and
Nigeria. More important for the calculation below, what do you think the
mass factions are?

Regards
Crispin

-----Original Message-----
From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Frans Peeters
Sent: Friday, January 08, 2016 08:14
To: 'Discussion of biomass cooking stoves' <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] venturi system -ratios of air and gas?

Andrew ,

    You have better air 22% ? then we have ....20% means 10 vol air for 1
mol propan .

-----Oorspronkelijk bericht-----
Van: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] Namens
ajheggie at gmail.com
Verzonden: vrijdag 8 januari 2016 11:39
Aan: Discussion of biomass cooking stoves
Onderwerp: Re: [Stoves] venturi system -ratios of air and gas?

[Default] On Fri, 8 Jan 2016 00:31:19 +0100,"Boll, Martin Dr."
<boll.bn at t-online.de> wrote:

> A happy New Year to all stovers!
>
>In a venturi system like of a propane gas-burner the driving gas has
pressure about 30 to 50 millibar.
>- What ratio have the volumes of gas and air, to make our admired blue
flame, as it does in gas-flames?

As you thought it is a bit more complicated, the stoichiometric (chemically
exact amounts to react for complete combustion) mass ratio of methane (same
principle for propane but numbers are simpler) and oxygen is about 4:1 but
as you have to allow for the other constituents of air, principally
nitorgen, this means you actually have to supply about 17 kg of air for
every 1 kg of gas.


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