Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Fuel Injection Pressure In Gas Turbine Engines  
User currently offlineA342 From Germany, joined Jul 2005, 4681 posts, RR: 3
Posted (4 years 8 months 2 weeks 4 days 20 hours ago) and read 8100 times:

Somehow this issue got me thinking: What are typical pressures for jet fuel injected into the combustion chamber of jet or turoprop engines?

I'm asking because I'd like to know how the injection pressure compares to that of modern diesel engines, which is up to 2000bar / 29,000psi.


It would be great if somebody could help.


A342


Exceptions confirm the rule.
18 replies: All unread, jump to last
 
User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 1, posted (4 years 8 months 2 weeks 4 days 20 hours ago) and read 8100 times:



Quoting A342 (Thread starter):
What are typical pressures for jet fuel injected into the combustion chamber of jet or turoprop engines?

According to my Rolls Royce book, the typical pressure inside a combustion chamber is around 100 to 200 psi. So theoretically you only need to overcome that pressure to be able to inject the fuel.

BUT the book also mentions that, specially in older types of injectors, pressures of up to 6000psi would be required for proper atomization of the fuel.


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 2, posted (4 years 8 months 2 weeks 4 days 14 hours ago) and read 8053 times:



Quoting A342 (Thread starter):
What are typical pressures for jet fuel injected into the combustion chamber of jet or turoprop engines?

1000-1500 psi is in my head as the typical output from the high-pressure fuel pump, but I don't have any documentation handy to back that up. As FLY2HMO noted, it's got to be meaningfully higher than the combustor pressure.

Quoting A342 (Thread starter):
I'm asking because I'd like to know how the injection pressure compares to that of modern diesel engines, which is up to 2000bar / 29,000psi.

I don't think there's any reason to run that high on a jet engine...they don't have nearly the same atomization issues that a Diesel does.

Tom.


User currently offlineJetMech From Australia, joined Mar 2006, 2687 posts, RR: 53
Reply 3, posted (4 years 8 months 2 weeks 4 days 13 hours ago) and read 8043 times:



Quoting Tdscanuck (Reply 2):
I don't think there's any reason to run that high on a jet engine...they don't have nearly the same atomization issues that a Diesel does.

I suppose another reason diesel engine have such a high injection pressure is due to the finite amount of time available in which to inject the fuel. Obviously, such a requirement does not occur with a jet engine.

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 4, posted (4 years 8 months 2 weeks 4 days 3 hours ago) and read 7965 times:



Quoting JetMech (Reply 3):
Obviously, such a requirement does not occur with a jet engine.

Not to mention Diesels produce much much more compression.


User currently offlineA342 From Germany, joined Jul 2005, 4681 posts, RR: 3
Reply 5, posted (4 years 8 months 2 weeks 4 days 3 hours ago) and read 7955 times:

Thanks for your feedback!

Quoting Tdscanuck (Reply 2):
I don't think there's any reason to run that high on a jet engine...they don't have nearly the same atomization issues that a Diesel does.

Well, diesels also started out at much lower pressures, the figures I mentioned are for engines less than ~10 years old.

What really helped diesels in terms of fuel consumption was direct injection, not so much extremely high pressures. But the main advantage is emissions. High pressures DRASTICALLY reduced the amount of PM emissions, and they also enabled CO emissions to drop a bit.
So gas turbine engines have a lot to gain in terms of emissions, especially since catalytic converters and PM filters are obviously not an option in airborne applications.

Quoting JetMech (Reply 3):
I suppose another reason diesel engine have such a high injection pressure is due to the finite amount of time available in which to inject the fuel. Obviously, such a requirement does not occur with a jet engine.

True, there is no such strict requirement. However, having the fuel ignite more quickly can't hurt, since it allows you to better control the place where the fuel is burned (in a gas turbine, the hot air flow carries the fuel molecules towards the exhaust during combustion). I admit I have no clue as to how important the added precision would be in terms of combustor design, but I don't think it is insignificant either.

I might add that I do indeed realize how difficult it would be to design, certify, produce and operate a 29,000psi injection pump that delivers the necessary fuel quantities for a large turbofan.


A342



Exceptions confirm the rule.
User currently offlineDBCC From Switzerland, joined Nov 2007, 65 posts, RR: 0
Reply 6, posted (4 years 8 months 2 weeks 4 days 2 hours ago) and read 7933 times:



Quoting A342 (Thread starter):
I'm asking because I'd like to know how the injection pressure compares to that of modern diesel engines, which is up to 2000bar / 29,000psi.

Sorry, 2'000 bar or 29'000 psi is not used in fuel injection.

Most high pressure hydraulic equipment has a limit of 640 bar (64'000 kpa / 9'282 psi). 6mm x 2 mm wall seamless hydraulic line tubing is rated at 640 bar working pressure with a factor of safety of 2.0.

For fuel injectors, comprise of single-seam welded tubing, mostly with a maximum working pressure of 100 bar.

Have a good search on the net, and you will find most fuel injection systems run at 25-40 PSI (1.7 to 2.7 bar)

At 600 bar, the stream coming out the end of a pipe can cut 50mm (2") solid steel with no problem. Imagine what 2'000 bar could do, if anyone could make equipment that could run at that pressure.


User currently offlineSpeedracer1407 From United States of America, joined Dec 2004, 333 posts, RR: 0
Reply 7, posted (4 years 8 months 2 weeks 4 days 1 hour ago) and read 7924 times:



Quoting DBCC (Reply 6):
Sorry, 2'000 bar or 29'000 psi is not used in fuel injection.

Most high pressure hydraulic equipment has a limit of 640 bar (64'000 kpa / 9'282 psi). 6mm x 2 mm wall seamless hydraulic line tubing is rated at 640 bar working pressure with a factor of safety of 2.0.

For fuel injectors, comprise of single-seam welded tubing, mostly with a maximum working pressure of 100 bar.

Have a good search on the net, and you will find most fuel injection systems run at 25-40 PSI (1.7 to 2.7 bar)

At 600 bar, the stream coming out the end of a pipe can cut 50mm (2") solid steel with no problem. Imagine what 2'000 bar could do, if anyone could make equipment that could run at that pressure.

I think that if you "have a good search on the net," you'll find that common rail fuel injection systems used in modern turbodiesel engines (as A342 states) do in fact operate in excess of 1500 bar, up to 2000, and have for years.

VW group diesels are in the 1600-1800 bar range. A very simple searched pulled up this Wikipedia list of VW engines. Yeah, it's Wiki, but it may give you an idea.

http://en.wikipedia.org/wiki/List_of_Volkswagen_Group_diesel_engines



Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
User currently offlineBri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4
Reply 8, posted (4 years 8 months 2 weeks 4 days ago) and read 7913 times:

Here's a data sheet for one such injector:

http://delphi.com/manufacturers/cv/p...1-diesel-electronic-unit-injector/

These systems use a much lower pressure fuel delivery system to each injector, and typically use a camshaft-driven plunger to pressurize a tiny amount of fuel to the atomization pressure (2,000bar or thereabouts). This is vastly different from the huge flow rates required in a hydraulic system, or those used in a turbofan engine for that matter.



Position and hold
User currently offlineA342 From Germany, joined Jul 2005, 4681 posts, RR: 3
Reply 9, posted (4 years 8 months 2 weeks 4 days ago) and read 7908 times:



Quoting Bri2k1 (Reply 8):
These systems use a much lower pressure fuel delivery system to each injector, and typically use a camshaft-driven plunger to pressurize a tiny amount of fuel to the atomization pressure

In the case of a unit injector, that's right. However, common rail systems do indeed use one central pump to deliver highly pressurized fuel to the injector.
Still, as you mention, flow rates are very low in comparison to the fuel requirements of large turbofans.



Exceptions confirm the rule.
User currently offlineJetMech From Australia, joined Mar 2006, 2687 posts, RR: 53
Reply 10, posted (4 years 8 months 2 weeks 3 days 18 hours ago) and read 7853 times:

Quoting FLY2HMO (Reply 4):
Not to mention Diesels produce much much more compression

I wonder what the ratio would be? Reciprocating engines base their compression process on a mechanically dependant compression ratio, whereas gas turbines base their compression process on a pressure ratio. I would be curious to see what the resulting pressure ratio was at the end of the compression stroke of a diesel engine   .

GE claims on overall pressure ratio of 42:1 for the GE90-115B at max power. According to Wikipedia, this is "equivalent" to a compression ratio of just over 15:1, which is apparently a typical compression ratio for a direct injection diesel.

http://en.wikipedia.org/wiki/Compression_ratio
http://www.geae.com/engines/commercial/ge90/ge90-115b.html

Quoting A342 (Reply 5):
However, having the fuel ignite more quickly can't hurt,

With a diesel, you want the fuel to ignite as soon as possible to reduce the severity of diesel knock. However, I think this is also dependent on the temperature at the end of the compression stroke as well as the fuel injection pressure.

Quoting DBCC (Reply 6):
At 600 bar, the stream coming out the end of a pipe can cut 50mm (2") solid steel with no problem. Imagine what 2'000 bar could do, if anyone could make equipment that could run at that pressure.

No doubt. With diesel injectors however, I suspect that one wants to quickly "spread" the fuel out to promote atomisation, as opposed to maintaining a focussed stream.

Regards, JetMech

[Edited 2009-12-08 18:01:13]


JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineNjxc500 From United States of America, joined Dec 2007, 240 posts, RR: 0
Reply 11, posted (4 years 8 months 2 weeks 3 days 16 hours ago) and read 7829 times:

Here's a MFR link that states 29,000 psi

Quoting DBCC (Reply 6):
Sorry, 2'000 bar or 29'000 psi is not used in fuel injection.

http://www.everytime.cummins.com/eve...pplications/mining/qsk23_mine.page


User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 12, posted (4 years 8 months 2 weeks 3 days 14 hours ago) and read 7807 times:



Quoting A342 (Reply 5):
High pressures DRASTICALLY reduced the amount of PM emissions, and they also enabled CO emissions to drop a bit.
So gas turbine engines have a lot to gain in terms of emissions, especially since catalytic converters and PM filters are obviously not an option in airborne applications.

High pressure drops particulates and CO in Diesel's because it atomizes the fuel more, ensuring faster and more complete combustion before the mixture gets frozen by the temperature drop during the expansion stroke. Gas turbines don't have that problem...they hold full pressure all the way through the combustor.

Quoting A342 (Reply 5):
I might add that I do indeed realize how difficult it would be to design, certify, produce and operate a 29,000psi injection pump that delivers the necessary fuel quantities for a large turbofan.

It wouldn't be easy, but it's not impossible either. The pump from a big water-jet cutter could probably do the job. In my former profession, we had pumps capable of 22,000 psi at several *barrels* per minute (equivalent to well over 1 million pounds per hour, more than any jet engine ever conceived). These things are, obviously, really big and heavy but it's old technology.

Quoting JetMech (Reply 10):
I would be curious to see what the resulting pressure ratio was at the end of the compression stroke of a diesel engine

If you approximate it as adiabatic compression with an ideal gas, the pressure ratio is about the compression ratio to the power of 1.4.

Tom.


User currently offlineLTC8K6 From United States of America, joined Jun 2009, 1209 posts, RR: 0
Reply 13, posted (4 years 8 months 2 weeks 3 days 14 hours ago) and read 7807 times:

Modern Gasoline Direct Injection engines such as Ford's EcoBoost run over 2,000psi fuel pressures.

User currently offlineJarheadK5 From United States of America, joined Nov 2005, 216 posts, RR: 1
Reply 14, posted (4 years 8 months 2 weeks 3 days 13 hours ago) and read 7796 times:



Quoting A342 (Thread starter):
What are typical pressures for jet fuel injected into the combustion chamber of jet or turoprop engines?

The GE T64 turboshaft on the H-53 helicopter runs fuel pressures in excess of 400psi.



Cleared to Contact
User currently offlineJetMech From Australia, joined Mar 2006, 2687 posts, RR: 53
Reply 15, posted (4 years 8 months 2 weeks 2 days 18 hours ago) and read 7716 times:

Quoting Tdscanuck (Reply 12):
If you approximate it as adiabatic compression with an ideal gas, the pressure ratio is about the compression ratio to the power of 1.4.

That's right on the money! 15^1.4 = 44. If we take away a small percentage to account for losses we get 42 .

Regards, JetMech

[Edited 2009-12-09 18:02:05]


JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineMarkC From United States of America, joined Apr 2006, 259 posts, RR: 0
Reply 16, posted (4 years 8 months 2 weeks 2 days 7 hours ago) and read 7676 times:

It is about 600 psi. PW modern engines.

Mark


User currently offlineA342 From Germany, joined Jul 2005, 4681 posts, RR: 3
Reply 17, posted (4 years 8 months 2 weeks 1 day 22 hours ago) and read 7640 times:



Quoting FLY2HMO (Reply 1):
BUT the book also mentions that, specially in older types of injectors, pressures of up to 6000psi would be required for proper atomization of the fuel.



Quoting Tdscanuck (Reply 2):
1000-1500 psi is in my head as the typical output from the high-pressure fuel pump



Quoting JarheadK5 (Reply 14):
The GE T64 turboshaft on the H-53 helicopter runs fuel pressures in excess of 400psi.



Quoting MarkC (Reply 16):
It is about 600 psi. PW modern engines.

Interesting, it seems the numbers vary widely.

Quoting Tdscanuck (Reply 12):
High pressure drops particulates and CO in Diesel's because it atomizes the fuel more, ensuring faster and more complete combustion before the mixture gets frozen by the temperature drop during the expansion stroke. Gas turbines don't have that problem...they hold full pressure all the way through the combustor.

Then the obvious question is: What enabled the reduction of PM and CO emissions in modern jet engines? You rarely see much visible smoke coming out of modern engines, like it was common with turbojets and early turbofans.

Quoting Tdscanuck (Reply 12):
These things are, obviously, really big and heavy

Yep, that would be the main problem.


A342



Exceptions confirm the rule.
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 18, posted (4 years 8 months 2 weeks 1 day 13 hours ago) and read 7607 times:



Quoting A342 (Reply 17):
What enabled the reduction of PM and CO emissions in modern jet engines?

As far as I know, better combustor designs and higher temperatures.

Tom.


Top Of Page
Forum Index

Reply To This Topic Fuel Injection Pressure In Gas Turbine Engines
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Turbine Engines: Status Of Material Science posted Thu Nov 19 2009 00:42:26 by Faro
Differences In RR 757 Engines posted Sun Aug 10 2008 07:52:54 by OB1504
Turbine Engines Running After Crash posted Fri Mar 9 2007 04:52:12 by HangarRat
Turbine Engines Are Ruining Aviation posted Fri Dec 8 2006 15:14:02 by 2H4
Fuel Efficiency Of In-flight Refuelling Pax A/c posted Thu Jul 6 2006 08:08:11 by Art
How Do Fuel Gauges Work In An Aircraft? posted Mon Jan 23 2006 17:00:17 by AirPacific747
Why Not The Fuel Dump Option In The B6 A320? posted Thu Sep 22 2005 17:37:21 by Bongo
Air Pressure In Cabin posted Sat Apr 2 2005 15:39:38 by SK A340
Unducted Turbine Engines posted Sun Mar 6 2005 19:24:04 by Jdwfloyd
Gas Turbine Engine Noise posted Fri Apr 9 2004 00:48:15 by NORTHSEATIGER
Fuel Injection In Jet Engines posted Mon Aug 1 2011 07:21:01 by Aleks166
R-Jet Gas Turbine With Orbiting Combustion Nozzle posted Tue Oct 19 2010 10:22:44 by LU9092
Gas Turbine Textbook posted Mon Oct 11 2010 09:52:27 by b737200
Some Gas Turbine Questions posted Fri Sep 10 2010 02:58:30 by faro
Turbine Engines: Status Of Material Science posted Thu Nov 19 2009 00:42:26 by Faro
Differences In RR 757 Engines posted Sun Aug 10 2008 07:52:54 by OB1504
Turbine Engines Running After Crash posted Fri Mar 9 2007 04:52:12 by HangarRat
Turbine Engines Are Ruining Aviation posted Fri Dec 8 2006 15:14:02 by 2H4
Fuel Efficiency Of In-flight Refuelling Pax A/c posted Thu Jul 6 2006 08:08:11 by Art

Sponsor Message:
Printer friendly format