Pratt & Whitney Geared Turbofan PurePowerŽ GTF Engine
#31
06-11-2012 | 02:47 AM
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From: Big Sky Country, Montana
I found a document from Stanford about the GE-90 (powers the 777) that says,
In mid-November 94, GE conducted the fan bladeout test with the FAA present. The release blade was detonated at a fan speed of 2,485 rpm, 10 rpm over the target, with the engine generating more than 105,000 lb. (466.8 kN) of sea level static (SLS) corrected thrust. The engine mount system performed as designed and the test demonstrated fan blade containment.
The ruggedness of the composite fan blade was successfully demonstrated, and the observed trailing blade damage matched pre-test analysis, verifying the inherent benefits of the composite blade design.
In mid-November 94, GE conducted the fan bladeout test with the FAA present. The release blade was detonated at a fan speed of 2,485 rpm, 10 rpm over the target, with the engine generating more than 105,000 lb. (466.8 kN) of sea level static (SLS) corrected thrust. The engine mount system performed as designed and the test demonstrated fan blade containment.
The ruggedness of the composite fan blade was successfully demonstrated, and the observed trailing blade damage matched pre-test analysis, verifying the inherent benefits of the composite blade design.
Looking at this, I assume that GE figured the thing would blow up at 2475 RPM and it went a whole 10 RPM faster. I bet they were proud of that! <G>
So, I would think that an engine of that size would be governed to run around 2k RPM. That's a whole lot slower than I would have imagined. I'd also guess smaller engines would run somewhat faster, but still nowhere near the 6 or 7k RPM I was guessing at.
#32
06-11-2012 | 07:04 AM
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From: Atlanta, GA
"So, I would think that an engine of that size would be governed to run around 2k RPM. That's a whole lot slower than I would have imagined. I'd also guess smaller engines would run somewhat faster, but still nowhere near the 6 or 7k RPM I was guessing at."
+1 That's a whole lotta mass turning at that speed!
+1 That's a whole lotta mass turning at that speed!
#33
06-11-2012 | 09:27 AM
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From: Bakersfield, CA, USA
No doubt the tips of the fans are moving very fast at that rpm. OTOH, they don't have to change direction like a piston does.
#34
06-11-2012 | 10:30 AM
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From: Cabot, AR
I don't read it that way at all. The blade was DETONATED on purpose. The test was designed to happen at a specific rpm. The actual rpm of the motor was only 10 rpm off of what they iintended. My guess is the 2475 rpm target was probably a typical operarting rpm, and not 'red line'.
No doubt the tips of the fans are moving very fast at that rpm. OTOH, they don't have to change direction like a piston does.
No doubt the tips of the fans are moving very fast at that rpm. OTOH, they don't have to change direction like a piston does.
#35
06-11-2012 | 03:08 PM
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From: Big Sky Country, Montana
I don't read it that way at all. The blade was DETONATED on purpose. The test was designed to happen at a specific rpm. The actual rpm of the motor was only 10 rpm off of what they iintended. My guess is the 2475 rpm target was probably a typical operarting rpm, and not 'red line'.
No doubt the tips of the fans are moving very fast at that rpm. OTOH, they don't have to change direction like a piston does.
#36
06-11-2012 | 04:31 PM
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From: Bakersfield, CA, USA
I'm not good at math anymore, but with the rpm and the diameter that Wookie posted, it would appear the tips of the blade are rotating at supersonic speeds.
Seeing that it was pushing well past its rated power for that blade test, the big motor probably was pretty close to max rpm, and well above its normal operating rpm.
Hey, I know nothing about jet engines, but a motor with 10' diameter blades pushing over 100,000 lbs of thrust is simply awesome.
Oh, and Raptor's Lycoming is very nice, too.
Seeing that it was pushing well past its rated power for that blade test, the big motor probably was pretty close to max rpm, and well above its normal operating rpm.
Hey, I know nothing about jet engines, but a motor with 10' diameter blades pushing over 100,000 lbs of thrust is simply awesome.
Oh, and Raptor's Lycoming is very nice, too.
#37
06-11-2012 | 09:16 PM
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From: Dover AFB DE / Harrisburg PA
I can lose a motor or two and not have a problem 
They are governed quite a bit, but by many more perimeters. The Engine Pressure Ratio being the most important along with EGTs.
Runnin' on the max thrust has a 5min countdown timer to keep 'er from meltin' down to a spinnin' core of a blob.
Adrianspeeder
Runnin' on the max thrust has a 5min countdown timer to keep 'er from meltin' down to a spinnin' core of a blob.
Adrianspeeder