Bryan Becker
Topic Author
Posts: 327
Joined: Fri Mar 02, 2001 12:38 pm

Explaine These Engines?

Sun May 13, 2001 6:20 am

I was lookin gat some wierd engines on the net and some of them i don't understand how they work?I'm sure hope these links work!!!!!!

engine#1-I don't see where the exhaust comes uot of this engine,well I do I think but i want to see if i'm right,and what do they use this engine for.An if the exhaust is coming out of where i think then I don't think this engine is using thrust as the power factor?

engine#2-What do they use this engine for?,man that is a wierd design they have for it,I wonder what the big turbine on the outside is used to turn,can you explaine it?I would love to see this engine running Smile.

engine#3-I see how this one works but could you tell me what the heck those things on the out side are for?

-BB Big thumbs up
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Explaine These Engines?

Sun May 13, 2001 6:53 am

Hi BB.

First picture -
Never seen this layout before (but I'm only a pilot.....) but you can see the gas path leads back to the combustion chambers then does a 180 degree turn before passing through the turbines. The exhaust then exits through the fin-shaped ducts around the outside of the engine; you can see they have small vanes inside to change the direction of flow another 180 degrees.

This would be called a Reverse Flow engine, and the turbines are driving a fan at the front, which will be a major contributor to total thrust. The exhaust "stacks" around the mid-section are also contributing to the thrust, which is coming out of several outlets instead of one big one at the back. I would guess this is a medium bypass ratio turbofan.

The advantage of this may be to allow installation in the nose of an aircraft, rather than in a wing-mounted pod, with the "stacks" protruding around the nose section.

Note the P&W PT6 turboprop, in which the gas path does two 180 degree turns and two 90 degree turns on its way through, exiting via two large exhaust stacks near the front of the engine.

I'd love to know which types this powers.

Second pic-
The Convair 990 had engines of this layout, maybe this is one (you don't give details of the engine designations). In a more conventional turbofan, the last stage turbine drives, via a shaft to the front of the engine, the fan. In this, to avoid using the shaft (weight, lubrication, vibration, complexity considerations), the fan is simply attached directly to the last turbine stage, in a seperate concentric duct. I would guess the efficiency would suffer due to the difficulty of sealing/seperating the hot stream through the turbine from the cold duct. I would think some hot air would leak out into the cold duct due to its higher pressure.

Third one-
This is an un-ducted fan. The hot section turbines drive two rings of contra-rotating blades on the outside of the engine. They were test flown on a 727-100 and an MD-83, which displayed at the Farnborough Air Show, and the type powers the Antonov 70 transport.

This type is quite efficient, makes less noise, but there is no protection in case of blade seperation, and the industry thought it too revolutionary.

So there are some basic descriptions, but I'm no engine expert. Hopefully we'll be enlightened by someone who is!

Regards - Musang
Posts: 1153
Joined: Sun Jun 25, 2000 11:19 am

RE: Explaine These Engines?

Sun May 13, 2001 7:01 am

Engine # 1 is an Allied Signal/Garrett ATF3

The Dassault Falcon 200 sports these engines

Engine #2 is an Unducted fan engine,the idea was to create a fuel effincet engine (that was very noisy) by mounting external fan blades (propellers of sorts) to the turbine section of an engine. Both GE and Allison/Pratt designed an engine, and both the MD-80 and 727 flew wtih them on test beds. MDC was actually going to use this engine on the MD-90 serious aircraft. Increasing noise regualtions, a drop in fuel perices, and according to a professor at Embry Riddle, one of the engines was FODed up by an enginner leaving a flashlight in the cowling during a test-cell run, resulted in them CanX'ing the program. Appartnly on the FOD incident, the loss cost millons and the young engineer his job.

Engine #3 Was the old Rolls-Royce Contra fan, similar in design to #2, the fan section was mounted in the turbine section but it was ducted, unlike, the UDF engine in #2 Apparenlty Rolls thought it would power A380 size a/c.

Posts: 1153
Joined: Sun Jun 25, 2000 11:19 am

RE: Explaine These Engines?

Sun May 13, 2001 7:03 am

looks like i got the numbering mixed up #3 is the UDF and #2 is the contra fan

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