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hydrogen dissolved in hydrocarbons



 
 
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  #1  
Old December 9th 03, 05:05 AM
Roger Stokes
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Default hydrogen dissolved in hydrocarbons

I googled recently that hydrogen will dissolve in hydrocarbons such as
decane when under pressure (and I can't find it again now!). It was unclear
to what percentage.

I'm wondering if this has been looked at for pressurized tank use since
firstly, the hydrogen coming out of solution keeps the tank pressurized as
the propellant is used, so helium pressurization is not required, secondly
turbopumps are not required, and thirdly a decane/hydrogen mix would
presumably achieve a better ISP than RP1-type fuels on their own, with all
the advantages of a dense propellant.

  #2  
Old December 9th 03, 06:50 PM
Bjørn Ove Isaksen
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Default hydrogen dissolved in hydrocarbons

Roger Stokes wrote:

I googled recently that hydrogen will dissolve in hydrocarbons such as
decane when under pressure (and I can't find it again now!). It was
unclear to what percentage.


You should check the Petroleum literature. It happends in the reserviors.

Sincerely
Bjørn Ove
  #3  
Old December 9th 03, 06:50 PM
Bjørn Ove Isaksen
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Default hydrogen dissolved in hydrocarbons

Roger Stokes wrote:

I googled recently that hydrogen will dissolve in hydrocarbons such as
decane when under pressure (and I can't find it again now!). It was
unclear to what percentage.


You should check the Petroleum literature. It happends in the reserviors.

Sincerely
Bjørn Ove
  #4  
Old December 9th 03, 08:22 PM
Henry Spencer
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Default hydrogen dissolved in hydrocarbons

In article ,
Roger Stokes wrote:
I googled recently that hydrogen will dissolve in hydrocarbons such as
decane when under pressure (and I can't find it again now!). It was unclear
to what percentage.


Unless it's fairly high pressure, I don't think you get very much of it
dissolved, alas.

I'm wondering if this has been looked at for pressurized tank use since
firstly, the hydrogen coming out of solution keeps the tank pressurized as
the propellant is used, so helium pressurization is not required, secondly
turbopumps are not required, and thirdly a decane/hydrogen mix would
presumably achieve a better ISP than RP1-type fuels on their own, with all
the advantages of a dense propellant.


Unfortunately, these are a bit contradictory -- unless you can get a *lot*
of hydrogen dissolved, if it comes out to pressurize the tank, it doesn't
go down into the engine to be burned.

Self-pressurizing systems are appealing, but often making them work
exactly right is harder than it looks. And they have the standard problem
of any pressure-fed system: heavy tanks.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #5  
Old December 9th 03, 08:22 PM
Henry Spencer
external usenet poster
 
Posts: n/a
Default hydrogen dissolved in hydrocarbons

In article ,
Roger Stokes wrote:
I googled recently that hydrogen will dissolve in hydrocarbons such as
decane when under pressure (and I can't find it again now!). It was unclear
to what percentage.


Unless it's fairly high pressure, I don't think you get very much of it
dissolved, alas.

I'm wondering if this has been looked at for pressurized tank use since
firstly, the hydrogen coming out of solution keeps the tank pressurized as
the propellant is used, so helium pressurization is not required, secondly
turbopumps are not required, and thirdly a decane/hydrogen mix would
presumably achieve a better ISP than RP1-type fuels on their own, with all
the advantages of a dense propellant.


Unfortunately, these are a bit contradictory -- unless you can get a *lot*
of hydrogen dissolved, if it comes out to pressurize the tank, it doesn't
go down into the engine to be burned.

Self-pressurizing systems are appealing, but often making them work
exactly right is harder than it looks. And they have the standard problem
of any pressure-fed system: heavy tanks.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |
  #6  
Old December 9th 03, 11:02 PM
Iain McClatchie
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Default hydrogen dissolved in hydrocarbons

Roger I can't find it again now!

Basically the same forum, 11 years ago:

http://www-2.cs.cmu.edu/afs/cs.cmu.e.../mnr/st/std134

Paul Dietz:
Paul BTW, it looks like the mole fraction of hydrogen or helium that would
Paul dissolve in propane at 298 K and 7.5 MPa are about 6% and 3%,
Paul respectively.

Roger I'm wondering if this has been looked at for pressurized tank
Roger use

I love this idea. But I don't see quite how to make it work. For the
hydrogen or helium to come out of solution at any significant rate,
you'd need the tank pressure to be quite a bit lower than equilibrium.
Does this imply a big drop in pressure right at launch (extra tank
weight)? Or a big rise in temperature, right at launch?

And it seems that the fluid would cool a fair bit as the hydrogren
boiled. Also, as the tanks empty the fuel/hydrogen proportion would
change. All these things will make pressure regulation tough. And
hydrogen boiling out as the fuel travels from tank, through cooling
jacket, into the injectors sounds like it would make the engine
operation uneven.

There is also the issue of throwing extra helium into the combustion
chamber from the LOX tank, but I'm going to guess that it will have a
positive but negligable effect on ISP from lowering the average
molecular weight of the exhaust.

Now how do I find out helium solubility in LOX?

For small rockets, a simplified tank pressurization scheme would be
very nice.
  #7  
Old December 9th 03, 11:02 PM
Iain McClatchie
external usenet poster
 
Posts: n/a
Default hydrogen dissolved in hydrocarbons

Roger I can't find it again now!

Basically the same forum, 11 years ago:

http://www-2.cs.cmu.edu/afs/cs.cmu.e.../mnr/st/std134

Paul Dietz:
Paul BTW, it looks like the mole fraction of hydrogen or helium that would
Paul dissolve in propane at 298 K and 7.5 MPa are about 6% and 3%,
Paul respectively.

Roger I'm wondering if this has been looked at for pressurized tank
Roger use

I love this idea. But I don't see quite how to make it work. For the
hydrogen or helium to come out of solution at any significant rate,
you'd need the tank pressure to be quite a bit lower than equilibrium.
Does this imply a big drop in pressure right at launch (extra tank
weight)? Or a big rise in temperature, right at launch?

And it seems that the fluid would cool a fair bit as the hydrogren
boiled. Also, as the tanks empty the fuel/hydrogen proportion would
change. All these things will make pressure regulation tough. And
hydrogen boiling out as the fuel travels from tank, through cooling
jacket, into the injectors sounds like it would make the engine
operation uneven.

There is also the issue of throwing extra helium into the combustion
chamber from the LOX tank, but I'm going to guess that it will have a
positive but negligable effect on ISP from lowering the average
molecular weight of the exhaust.

Now how do I find out helium solubility in LOX?

For small rockets, a simplified tank pressurization scheme would be
very nice.
 




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