American twins,Brit triple spool engines?

[gas path]

@unmanned transport
Exactly which RB211-524 are you refering to?
The -524 does not have a 'thrust link arrangement' as it's not required. The Trent however does have a thrust link as does the 90, that links the aft engine mount to the fancase (NOT the forward mount.).
The rigidity of the base 211 comes from the fact that the engine is complete with all the thrust reverser and cold stream duct. (A tube within a tube if you like, very rigid in its own right!).
The reason that the Trents and the 90 have the thrust links is as you pointed out to increase the rigidity of the engine because the thrust reverser halves are now an airframe part and remain with. The 'tubes' BTW are not aluminium but high grade steel...they need to be as there is a lot of torsional loads on them.

[Turbine D]

gas path

You are correct, it prevent "back bone bending" of the engine that was learned early on to be a serious problem if not addressed.

In the very early days, P&W found out the fan case turned oval on the JT9-3D at high thrust and they had to use a tubular stiffening arrangement to prevent this from happening.

Just a little history from a old guy...

[unmanned transport]

gas path, sorry, I meant the next gen of RRs above the -524.

The thrust link on the CF6s that I was involved with when I was as an inspector was not steel. It's fwd mount area config was a curved and sandwitched plate arrangement that bolted to the fwd LPC flange under the fwd mount and tied in with this floating mount. When you really think about this drag link, it does not prevent all of the bowing of the core casing during what I like to call 'pod nod' during real hard turbulence. What would be a better design for these engines would be longtidunal plate mounted say at the twelve oclock position on the engine 4-6" deep running along the casing and tied into each engine flange.
If they could eliminate minute bowing of the case the mfgs could tighten up blade tip clearances for even more efficency.

That's very true Clive, all this ICAO data excludes the cruise portion.

Turin, so true the GE and PW engines were a nightmare to inspect around the core section and were difficult for the engineers. the only major negative regarding peripheral components mounted on the fancase of the RR would be increased diameter of the cowled up fan case resulting in more flate plate area.

Was the FCOC relocated on the Trent from the fan case to the core for more heat?

Is the ICAO data that I've noted extracted from the manufactures' test cell engine runs? I don't know.

Meanwhile many happy memories I've had of being on 'the hangar floor' playing with these masterpieces of machinery. One must move onwards and upwards for a good future.

Blue skies folks, now off to fly my Cessna....what a great life.

[unmanned transport]

PIP..ing the GEnx.

Boeing and GE look to firm third GEnx improvement package

PIP1 - a revised LPT......wonder which disk.
Man that is a fairly major Product Improvement Program.

Any info on the T1000 is scarce.
Wonder how it is going for pippin.

Fuel burn comparisons between these two big donks will be interesting.

[barit1]

Going back to McDonnell Douglas days - they liked the gearbox under the fan case for maintenance reasons. The CF6-6 and -50 were configured this way, and IIRC the JT9D-59 on DC-10-40s (JAL & NWA) were also.

But Boeing was more performance oriented, and bolting the gearbox up close to the core made the fan cowl a bit slimmer. Thus the CF6-80A and 80C2 have a core-mounted AGB -- as have all P&W Boeing engines.

[unmanned transport]

Since the ICAO data for the previously mentioned engines indicates that the RR hogs more fuel in take-off, climb, descent and idle, she sure ain't going to burn less in cruise than the competition.

[lomapaseo]

Since the ICAO data for the previously mentioned engines indicates that the RR hogs more fuel in take-off, climb, descent and idle, she sure ain't going to burn less in cruise than the competition

How is that so?

[Turbine D]

OK, here is some engine comparison data for all to mull over:
Three spool vs two spool

B-777

Trent882
Engine weight (dry): 12,009 lbs.
Overall length: 172 inches
Fan diameter: 110 inches
Thrust at TO: 80,711 lbs.
Thrust during Cruise: 15,917 lbs.
SFC (cruise): 15.66 mg/N-s

GE90
Engine weight (dry): 18,200 lbs.
Overall length: 187 inches
Fan diameter: 123 inches
Thrust at TO: 85,716 lbs.
Thrust during Cruise: 15,432 lbs.
SFC (cruise): 8.30 mg/N-s

Two spool vs Two spool

Airbus A-320 (assumed)
V2500-A1
Engine weight (bare):
Overall length: 126 inches
Fan diameter: 63 inches
Thrust at TO: 24,526 lbs.
Thrust during Cruise: 4762 lbs.
SFC (cruise): 16.29 mg/N-s

Airbus A-340 (assumed)
CFM56-5C2
Engine weight (bare)
Overall length: 103 inches
Fan diameter: 72 inches
Thrust at TO: 30,600 lbs.
Thrust during Cruise: 6786 lbs.
SFC (cruise): 16.06 mg/N-s

Sorry, couldn't find an apples to apples comparison for the CFM vs V2500 but think they are very close to one another on the Airbus A-320.

This data come from a study done at Stanford University looking at fuel consumption on various engines.

Don't shoot the messenger.

Turbine D

[CliveL]

This data come from a study done at Stanford University looking at fuel consumption on various engines.

Don't shoot the messenger.

Not trying to shoot the messenger Turbine D, but there is a typo in there - surely somebody at Stanford put in the takeoff sfc for the GE engine by mistake? Otherwise it is twice as efficient as any other turbofan flying.

[CliveL]

Since the ICAO data for the previously mentioned engines indicates that the RR hogs more fuel in take-off, climb, descent and idle, she sure ain't going to burn less in cruise than the competition.

I hinted at it in a previous post, but I guess I'll have to spell it out - untreated SLS testbed values of sfc. are NOT a valid comparison of installed cruise sfc unless the bypass ratios of the two engines are identical.

Basic engine thermodynamics says that the ratio of SLS to cruise sfc depends on the Bypass Ratio and the cruise Mach Number. The higher the BPR the worse is the ratio (i.e. the worse the cruise sfc for a given SLS sfc.) Comparing engines simply on SLS sfc therefore introduces a systematic bias in favour of the high bypass engine.

In addition, the high BPR engine will have more wetted area (drag) so the installed sfc will be relatively higher and the powerplant will be heavier.

I take the point that one has to be careful about comparing apples with apples, and the engine weights given in the FAA certification fact sheets (which one might have thought free of bias even though one of their functions is to further US civil aviation ) do not seem to be consistent definitions from one manufacturer to another. In addition, there is usually a factor of 1.6 or more between the bare dry weight of the engine and the installed powerplant weight, and this factor will obviously depend on what is included in the datum engine weight. For this reason I would prefer to use differences between installed engines derived from the aircraft manufacturers MWE values. For the A330, taking the RR version as datum, the GE aircraft weighed just over 600 lb more and the PW version a whopping 1800 lb more.

To the best of my knowledge, the GE engines have higher BPR than the Trent equivalents, which is probably why the net gain on the A330 was only 1% over the Trent and PW4000 versions rather than the value suggested by ICAO emissions data which is based on SLS measurements.

Don't get me wrong; I hold no brief for one engine manufacturer against another, but I hate to see dodgy comparisons

[unmanned transport]

lomapaseo, it's just common logic.

Thanks for the data Turbine D.

Source for data?

No doubt about it, the 90 is a steam engine having chomped down too many hamburgers. I wish they would hurry up and refine it some more and incorporate some GEnx technology into it such as a composite fan case, strain gauge some of the metal in the casing to see if it could go thinner walled. Possibly the disks could go thinner walled as well.

The fan dia on the 90 at 13 more inches will be more drag.

That SFC cruise burn for the Trent at 495lbs more cruise thrust is almost double that of the 90 !

[unmanned transport]

Good points Clive.....we need the BPR numbers.

[Turbine D]

I am having trouble finding the original site tied to Stanford, but here is the the same report that I did find on the internet.

It looks like the cruise thrust is calculated.

B.Tech Seminar

Turbine D

[KBPsen]

Originally Posted by Turbine D

It looks like the cruise thrust is calculated.

It clearly says SLS SFC in the first table for the GE90, while it says SFC (cruise) for the Trent.

Anybody really should be thinking "that can't be right" when presented with numbers that differs by a factor of 2.

The cruise figure for the GE90 is 15.60 mg/N-s versus 15.66 mg/N-s for the Trent.

[CliveL]

Interesting report Turbine D.

I see it does confirm that the 8.3 sfc is indeed SLS, and the (calculated) cruise sfc is 15.6.

I can get the Trent BPRs from the RR website, but I am having difficulty with comparable GE values. Does anyone have any ideas?

CSL

[Turbine D]

CliveL

I put this info out since there was a lot of discussion on SFC. But I am not sure that SFC is really a good measure for comparison purposes. Perhaps the real measure is something like total fuel burn (takes into consideration the total aircraft) or block fuel as was mentioned earlier in this thread.

Turbine D

[unmanned transport]

Thanks for the link Turbine D.

[CliveL]

Turbine D

" I am not sure that SFC is really a good measure for comparison purposes. Perhaps the real measure is something like total fuel burn (takes into consideration the total aircraft) or block fuel as was mentioned earlier in this thread."

I'd go along with that all the way

CSL

[unmanned transport]

Clive, I think it is for a bare engine not attached to the airframe.

When attached to the airframe, pylon/strut sidethrust, downthrust/upthrust angles will be the same for a GE/RR/Pratt. Wetted area will be different for each engine which will make a difference. There are a few more variables.

[CliveL]

Clive, I think it is for a bare engine not attached to the airframe.

Yeah, but when you read the small print it ain't so obvious what you have:

GE engines "includes basic engine, basic engine accessories and optional equipment as listed in manufacturer's engine specifications including condition monitoring instrumentation sensors"

PW engines "includes all essential accessories but excludes starter, exhaust nozzles and power source for ignition system" [but the PW4164 weight includes the starter apparently]

RR Trent 768 gives Basic Engine and Dry Powerplant weights

That's why I think you need to try to find something that includes the all-in values.

Following up on Turbine D's remarks on total fuel burn and your earlier reference to the A330 performance data extracted from the AI Airfield Planning document, Boeing publish similar planning guides for all their aircraft (AI seem very coy about it for some reason - I did find a URL but you need to be registered in their Airbus World). Some of the Boeing planning includes P/L / range diagrams for several engines. Taking the zero P/L / Max.Tankage range is going to be as near as one can get to a "pure" comparison between engines as the fuel on board will be identical and the TOW will be OWE plus fuel so that powerplant weight effects are also included.

This gives:

B757-300:- PW 2040 4250 n.mls: RB211-535E4 4150 n.mls

B767 300ER:- CF6-80C2B7F1 7100 n.mls: PW4062 6950 n.mls

That is all the comparative data I have been able to locate so far