# What's in jet fuel?

**URL:** <https://boards.straightdope.com/t/whats-in-jet-fuel/656310>\
**Category:** Factual Questions\
**Created:** [April 21, 2013, 2:35pm UTC](https://boards.straightdope.com/t/whats-in-jet-fuel/656310 "2013-04-21T14:35:45Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\
**Post date:** [February 27, 2015, 4:02pm UTC](https://boards.straightdope.com/t/whats-in-jet-fuel/656310/21 "2015-02-27T16:02:16Z")

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> [@Habeed](#):
>
> Natural gas is, uh, already gaseous. Surely you don’t need to do anything but pipe it into the chamber at the same place where the fine mist of jet fuel is made by the spray nozzles. You’d probably remove the spray nozzles and replace them with some kind of orifice with a known diameter, then just adjust the flow rate of gas until the engine runs smoothly.

Essentially true, but you miss a lot of points

1\> Density of liquids is typically in the range of ~600 times the density of liquids - so the fuel supply system to the nozzle have to be appropriately sized if you are trying to provide the same fuel heat content.

2\> The Hydrogen to Carbon ratio of natural gas is higher than liquid fuels (substantially higher) - so the air requirement for the same heat released is changed. You now have to fix the air flow (since the air compressor is run by the same gas turbine you now need to adjust that)

Frame gas turbines which are designed for stationary use - have the real estate (space) for going to even low BTU gas. Aero-derivatives ( air plane engines converted for power production or drivers) have limited real estate available and fuel flexibility issues.

3\> Depending on the air emissions permit - NOx needs to be looked into. If the turbine has Ammonia based SCR - you are probably okay. If not, you have to consider DLN (Dry low nox burners) - which essentially let the combustion processes happen in stages - limiting the amount of oxygen in each stage.

4\> The Nozzle design will also need to look for how far the flame sits from the surface of the nozzle for lifing of the nozzle - steam injection or water injection is not uncommon.

This thread has a lot of good information and a lot of jumbled / misinformation. If I find some time, I will try to clear things up.

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**Author:** ![Habeed](https://avatars.discourse-cdn.com/v4/letter/h/a587f6/32.png) [@Habeed](https://boards.straightdope.com/u/Habeed)\
**Post date:** [February 27, 2015, 11:08pm UTC](https://boards.straightdope.com/t/whats-in-jet-fuel/656310/22 "2015-02-27T23:08:27Z")

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> [@am77494](#):
>
> 2\> The Hydrogen to Carbon ratio of natural gas is higher than liquid fuels (substantially higher) - so the air requirement for the same heat released is changed. You now have to fix the air flow (since the air compressor is run by the same gas turbine you now need to adjust that)

Yikes. Turbine power affects air flow which affects turbine power. Obviously, a stable solution exists, where you have a given amount of turbine blades to develop just enough power to supply the air to fully burn all the fuel.

But that solution would be fuel dependent. If you grabbed an engine tuned for one solution and tried to use it for a different fuel needing a different ratio…

Can this problem even be fixed without essentially replacing either the air compressor or the turbine?

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