Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
norcal
Topic Author
Posts: 1507
Joined: Sun Mar 20, 2005 1:44 am

What Is A Dual Annular Combustor?

Mon Apr 04, 2005 11:59 am

I have read that the CFM 56-7 has a dual annular combustor, and that this was the first engine to introduce this. How does this work and what are the benefits?
 
jdwfloyd
Posts: 803
Joined: Sun Feb 06, 2005 10:29 am

RE: What Is A Dual Annular Combustor?

Mon Apr 04, 2005 12:01 pm

May want to take it to the Techy page, would have more help from those guys.
 
AA737-823
Posts: 5495
Joined: Wed Mar 01, 2000 11:10 am

RE: What Is A Dual Annular Combustor?

Mon Apr 04, 2005 12:22 pm

Well, I'll do my best.
I can tell you what an ANNULAR combustor is.
First, a can combustor. It's round. It's small. Jet fuel is sprayed in. Fire is started. BANG. These are typically arranged in a circle, about six of them in a jet engine. The exhaust coming out of them powers the turbine, which in turn runs the compressor section at the front of the engine.
Now, an ANNULAR combustor is a little different. Instead of six equally spaced cans, an ANNULAR combustor basically forms a ring... a circle around the shaft of the engine. It's one LARGER combustion chamber. It's lighter. Cheaper. Lasts longer. But is harder to work on.

Now, a DOUBLE ANNULAR must be (get the impression I am guessing here???) some sort of twin-annular arrangement. Not quite sure how that would work. I suspect it's a variation in the shape of the combustion chamber itself.

Hope this gives you a least a foundation of understanding. Otherwise, GOOGLE IT!
 
norcal
Topic Author
Posts: 1507
Joined: Sun Mar 20, 2005 1:44 am

RE: What Is A Dual Annular Combustor?

Mon Apr 04, 2005 12:26 pm

Yeah I sent it over to the techy page, hopefully someone over there will know. I know about Annular, can, and annular/can burners, I just have never heard of a dual annular before
 
iwok
Posts: 979
Joined: Wed Jan 26, 2005 2:35 pm

RE: What Is A Dual Annular Combustor?

Mon Apr 04, 2005 2:43 pm

Might have something to do with pre-combustion and combustion stoichiometries. I'll look for this on the techy forum.

-iwok
 
FredT
Posts: 2166
Joined: Thu Feb 07, 2002 9:51 pm

RE: What Is A Dual Annular Combustor?

Sun Apr 10, 2005 3:48 am

It is simply two annular combustors placed concentrically. The grand idea was, IIRC, that at low power settings you can have the fire lit in just one of them, thereby improving efficiency at all power settings by being able to optimize the design of the combustion chambers better.

I think it was a failure as well. Again IIRC, SAS were pretty alone in ordering their aircraft (B736?) with this option and it created problems for them down the line.

Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
 
MD11Engineer
Posts: 13899
Joined: Sun Oct 26, 2003 5:25 am

RE: What Is A Dual Annular Combustor?

Sun Apr 10, 2005 9:13 am

The big advantages of a dual annular combustors are:
a) reduction of fuel consumption
b) reduction of NOx emissions.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
Yikes!
Posts: 356
Joined: Sat Oct 13, 2001 4:51 pm

RE: What Is A Dual Annular Combustor?

Sun Apr 10, 2005 3:57 pm

I thought this was the techie forum??? What am I missing?

Great link, BTW.
 
backfire
Posts: 3467
Joined: Fri Oct 06, 2006 8:01 am

RE: What Is A Dual Annular Combustor?

Tue Apr 12, 2005 6:50 am

'Annular' means 'ring-shaped'.

Dual-annular combustors, as the name indicates, contain two combustor rings. CFM developed the DAC engine to reduce gaseous NOx emissions mainly by switching off some of the combustors in the inner ring of two when they are not required.

DACs address the differing engine fuel combustion requirements of the various phases of flight, in order to cut emissions. Such an engine can employ all its combustor domes, or only some of them, depending on whether full or idle power is required.

Both the CFM56-5 and CFM56-7 had DAC versions, although the -7 suffered early problems with vibration affecting launch customer SAS.

Rolls-Royce subsequently looked into simplifying the DAC engine by using a single-annular combustor but designing a staged fuel-injection system. Rolls claimed that the NOx emission reductions achievable with this design would improve on those available through DAC technology.
 
gigneil
Posts: 14133
Joined: Fri Nov 08, 2002 10:25 am

RE: What Is A Dual Annular Combustor?

Tue Apr 12, 2005 11:04 am

Quoting AA737-823 (Reply 2):
Now, a DOUBLE ANNULAR must be (get the impression I am guessing here???) some sort of twin-annular arrangement. Not quite sure how that would work. I suspect it's a variation in the shape of the combustion chamber itself.

Twin and double are somewhat different.

The GEnx will have a twin-annular pre-swirled combustor, but GE still refers to it as an advanced single annular designed.

N
 
troubleshooter
Posts: 420
Joined: Mon Feb 07, 2005 5:22 am

RE: What Is A Dual Annular Combustor?

Wed Apr 13, 2005 12:11 pm

Here you can see a typical cross sectional view of a dual annular combustor:
http://roger.ecn.purdue.edu/~propulsi/propulsion/images/jets/basics/combust.jpg

Where is the other thread gone? I think we had discussed this question a few days ago...
This job sucks!!! I love this job!!!
 
amtrosie
Posts: 273
Joined: Thu Jan 06, 2005 6:44 am

RE: What Is A Dual Annular Combustor?

Wed Apr 13, 2005 11:17 pm

Troubleshooter, Can you repost the links. They didn't come up.
 
F-WWAI
Posts: 129
Joined: Thu Dec 30, 1999 7:41 am

RE: What Is A Dual Annular Combustor?

Tue Apr 26, 2005 7:04 am

 
aeroguy
Posts: 66
Joined: Wed Aug 15, 2001 1:33 am

RE: What Is A Dual Annular Combustor?

Thu Apr 28, 2005 7:10 am

Perhaps the end of this thread might be helpful as well: 777 GE-90 "dome" Combustion (by QANTAS747-438 Mar 22 2004 in Tech Ops)

Who is online

Users browsing this forum: No registered users and 18 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos