What Is the Air Solubility Coefficient of Kerosene-Based Aircraft Fuel?

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Discussion Overview

The discussion focuses on determining the air solubility coefficient of kerosene-based aircraft fuel, exploring methods for calculation and relevant coefficients. The scope includes theoretical approaches and practical considerations related to vapor pressure and solubility in aviation fuels.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about finding the air solubility coefficient and mentions a rule of thumb relating air pressure to dissolved air percentage.
  • Another participant suggests calculating the partial pressure of the liquid at a given temperature, using the ideal gas law and considering non-ideal behavior.
  • A participant expresses uncertainty about finding the partial pressure and questions the relationship between true vapor pressure and Reid vapor pressure.
  • There is mention of a thesis that discusses methods for calculating pressures of complex mixtures, noting that kerosene has a boiling range that complicates single substance data.
  • One participant recommends looking into the Ostwald Coefficient as a relevant measure for air solubility.
  • Links to resources showing the Ostwald coefficient for aviation kerosene are provided, along with a reference to a study on the effects of fuel in airplane fuel tanks.

Areas of Agreement / Disagreement

Participants express varying levels of uncertainty regarding the methods for calculating the air solubility coefficient and the relevance of different vapor pressures. There is no consensus on a definitive method or value.

Contextual Notes

Participants note the complexity of kerosene's boiling range and the potential limitations of using single substance data for calculations. The discussion highlights the need for measurements to estimate average molecular weights of vapor mixtures.

robsmith82
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Hello,

How would I go about finding the air solubility coefficient of a kerosene based aircraft fuel? I know that as a rule of thumb, air pressure is close to percent dissolved air, eg. at atmosphere, 15 psi gives around 15% dissolved air, but how would I calculate the coefficient accurately?
 
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I would find the partial pressure of the liquid of interest at the temperature you are given. That may not be straightforward. From that partial pressure you can calculate the number of moles of liquid at that temperature using some form of the ideal gas law (IGL). There are several approximations or enhancements to the IGL that address non-ideal behavior. Multiply the moles by the average formula weight of the liquid to obtain the mass of vapor (assume kerosene?). The gas constant will indicate the units of volume which that mass occupies.
 
Thanks for the reply.

Not sure how I can find the partial pressure. I can find the true vapour pressure from the reid vapour pressure if it is possible to do from this?
 
robsmith82 said:
Not sure how I can find the partial pressure. I can find the true vapour pressure from the reid vapour pressure if it is possible to do from this?

It may be but I'm not sure how that might be done. Here is a thesis on the subject. I can't vouch for its accuracy.

http://www.ddbst.de/new/InfoMat/Yash_Nannoolal_Phd_Thesis_2007.pdf

Since your liquid (kerosene or JP8) has a boiling range from 150C to 290C, data for a single substance may not be helpful. The thesis and references therein present methods to calculate pressures of more complex mixtures like this. After you calculate the partial pressure you still need to estimate the average molecular weight of the vapor mixture. I have no idea how to do that without some type of measurement.
 
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You need to look into the Ostwald Coefficient.
 
robsmith82
How would I go about finding the air solubility coefficient of a kerosene based aircraft fuel?
You need to look into the Ostwald Coefficient.

Here you are.

The links below show the Ostwald coefficient for aviation kerosine in terms of volume of gas per volume of fuel (independent of pressure):

http://gp5.home.infionline.net/ost1.gif
http://gp5.home.infionline.net/ost2.gif

The data comes from:

"The Effect of Fuel on an Inert Ullage in a Commercial Transport Airplane Fuel Tank"
by William M. Cavage, July 2005,
DOT/FAA/AR-05/25 Office of Aviation Research Washington, D.C. 20591,
APPENDIX A—GRAPH OF OSTWALD COEFFICIENT FOR OXYGEN AND NITROGEN, page A-2.

Hope this helps.
 
Last edited by a moderator:

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