P&W PurePower Fan Drive Gear System Sets Endurance Testing Milestone

[Metallic]

Pratt & Whitney PurePower Fan Drive Gear System Sets Endurance Testing Milestone
UNITED STATES - 19 AUGUST 2009

Pratt & Whitney successfully completed accelerated endurance testing equivalent to more than 20,000 hours of service operation on the PurePower PW1000G fan drive gear system. Pratt & Whitney is a United Technologies Corp. (NYSE:UTX) company.

"Results from the latest round of on-going tests continue to demonstrate the design robustness for the PurePower fan drive gear system," said Bob Saia, vice president, Next Generation Product Family, Pratt & Whitney. The fan drive gear system and its patented Geared Turbofan(tm) technology target double-digit reductions in fuel burn, environmental emissions, engine noise and operating costs.

More than 1,000 hours of laboratory testing on the fan drive gear system have produced significant accomplishments such as simulating more than 40,000 take offs "at the equivalent loads at 30,000 pounds of thrust" loads, with 15,000 of those being maximum torque takeoffs at extreme oil temperatures. Post-test inspections have revealed the gears, journal bearings and components to be in excellent condition after this rigorous testing.

The recent endurance testing for the fan drive gear system further supports the findings from the PW1000G demonstrator engine, which confirmed the system's robust design and efficiency with lower than predicted heat rejection into the engine oil system. The PW1000G Demonstrator Engine garnered 406 hours of operation with 120 hours in flight.

"The PW1000G engine demonstration program showed the fan drive gear system was invisible to the airplane, with overall operation of the geared turbofan engine the same as today's conventional engines, only with lower fuel consumption and drastically lower noise," said Saia.


Source: Pratt & Whitney

 

[PAFAce]

Some of my colleagues have worked on this engine (or related R&D projects). Essentially, from what I understand, they link-up the low-pressure turbine with the fan (as usual), except that instead of being connected by a shaft, they're connected through a gear-system. That way, both can be allowed to rotate at different speeds. The fan works better at low speeds whereas the turbine works better at faster speeds. This way, both can be run closer to their optimal speeds using gears. This can allow up to 10% better fuel efficiency, theoretically.

The reason this news is so critical is because by adding a gear system, PW introduced more moving parts and more complex dynamics. As a general rule in engineering, this would directly result in lower reliability, maintainability and dependability (RMD). Hence, through this type of extensive endurance testing, they will be able to prove that the benefits of this technology can be harnessed without paying serious RMD costs.

Interesting stuff, once you get to know a little. I just hope I didn't get the explanation wrong, those PW guys will be laughing their a*ses off...

 

[gambit]

Some of my colleagues have worked on this engine (or related R&D projects). Essentially, from what I understand, they link-up the low-pressure turbine with the fan (as usual), except that instead of being connected by a shaft, they're connected through a gear-system. That way, both can be allowed to rotate at different speeds. The fan works better at low speeds whereas the turbine works better at faster speeds. This way, both can be run closer to their optimal speeds using gears. This can allow up to 10% better fuel efficiency, theoretically.

The reason this news is so critical is because by adding a gear system, PW introduced more moving parts and more complex dynamics. As a general rule in engineering, this would directly result in lower reliability, maintainability and dependability (RMD). Hence, through this type of extensive endurance testing, they will be able to prove that the benefits of this technology can be harnessed without paying serious RMD costs.

Interesting stuff, once you get to know a little. I just hope I didn't get the explanation wrong, those PW guys will be laughing their a*ses off...

You are on the correct path...Take a look at this...

49 - SOL:F-16 ACCESSORY DRIVE GEARBOX TEST STAND (GREECE) (06/03/98)

DESCRIPTION: The ADG Test Stand is utilized to check the F-16 ADG material and functional integrity as part of depot level overhaul acceptance test requirements after the ADG has been overhauled. This test stand consists of a base assembly, a control assembly, and various accessories. The base assembly provides rigid mounting support for the test article and test stand drive components including an absorption dynamometer, prime mover, speed increasing gearbox, inertial load flywheel, and necessary support bearings and disconnect couplings. The control console provides the operating controls, instrumentation, aircraft controller, and safety circuits necessary for controlling and monitoring the test article and test stand operating parameters. Electrical Harnessing connects the test stand control and monitoring devices to the test article sensor and solenoid valve electrical connector receptacles. A separate unit to the control console assembly is a host computer, and data-acquisition system with programmed software and a printer housed within its own cabinet enclosure. The accessories provide electrical and hydraulic load capability, lubrication and cooling of test article and test stand components. Lubricating oil and hydraulic oil systems can be replenished. In operation, the test stand simulates the F-16 aircraft engine start system function and operating conditions and is designed and built to test the F-16 ADG.

Notice the highlighted. Every engine has some derivatives of an accessory drive gearbox (ADG). The component is needed to run the various miscellaneous items like electrical generators or hydraulic pumps to keep an aircraft flying. Connecting this fan through an ADG does increase overall complexities, weight and maintenance requirements. The issue will be on if these increases are worth the investments.

 

[PAFAce]

You are on the correct path...Take a look at this...

49 - SOL:F-16 ACCESSORY DRIVE GEARBOX TEST STAND (GREECE) (06/03/98)

Notice the highlighted. Every engine has some derivatives of an accessory drive gearbox (ADG). The component is needed to run the various miscellaneous items like electrical generators or hydraulic pumps to keep an aircraft flying. Connecting this fan through an ADG does increase overall complexities, weight and maintenance requirements. The issue will be on if these increases are worth the investments.

Thanks for he information, gambit. Though, is it still referred to as an "Accessory Drive Gearbox" if it drives a fan in a turbofan engine, which is an integral part of the engine itself? The word "accessory" doesn't quite fit. Or maybe you were referring to something different. In this new tech by PW, the gearbox simply facilitates the running of the engine itself, not other systems.

 

[gambit]

Thanks for he information, gambit. Though, is it still referred to as an "Accessory Drive Gearbox" if it drives a fan in a turbofan engine, which is an integral part of the engine itself? The word "accessory" doesn't quite fit. Or maybe you were referring to something different. In this new tech by PW, the gearbox simply facilitates the running of the engine itself, not other systems.

The simplest turbofan is the single spool direct coupled engine where the fan assembly is 1-1 ratio direct coupled to the core, where combustion occurs. This design is pretty much a museum piece.

File:CF6-6 engine cutaway.jpg - Wikipedia, the free encyclopedia

What we have today are multiple stages where the fan assembly is coupled, not directly to the engine core, but to a reduction gear mechanism. The accessory drive gearbox is illustrated as well in the above image.

According to PW's sales brochures...

In the PurePower PW1000G engine, a state-of-the-art gear system allows the engine’s fan to operate at a slower, optimum speed while freeing the low-pressure compressor and turbine to operate at their optimized higher speed, increasing engine efficiency and delivering significantly lower fuel consumption, emissions and noise. This increased efficiency also translates to fewer engine stages and parts for lower weight and maintenance cost.

So what we have are less engine core stages that allowed the remainder to spin at the highest rotation while the fan assembly spin far lower. I doubt that PW would call this reduction gearing mechanism an 'accessory drive' but conceptually it is no different. Less complexity at the engine core but more at the fan assembly end in order to have a lower rotation speed. But if there is going to be a reduction gearing mechanism to drive the fan assembly, why not couple all the true accessories, such as electrical generators or hydraulic pumps to the same?

Personally, even though all my jet engine experience have been with jet fighters, low bypass turbofan types, I would rather work on the accessory drive system than to change an engine, whether it is called an 'accessory drive' or not.