Engines of Innovation

[spazsinbad]

Engines of Innovation [VERY LONG ARTICLE BEST READ at SOURCE]
Aug 2017 Jim Mathews

"Real propulsion breakthroughs may be ready to leave the lab and enter the fleet.
Truly game-changing breakthroughs in US fighter engines are nearly in hand. After more than a decade of labor by Air Force Research Laboratory and engine-makers Pratt & Whitney and General Electric Aviation, increases in speed and range, reduced dependency on tankers, and a menu of new tactics are just some of the advantages coming in the next few years.

By 2021, engineers are expected to have built and tested flightworthy engines that could, for example, give new fighters 30 percent more range than they have today, produce enough spare power to fire directed energy weapons, or run cool enough to improve stealth. Besides those advantages, new engines could provide great benefit to the F-35 strike fighter, allowing it to sustain high-speed flight at treetop altitudes, something it can’t do today. [NOT ABOVE 700 KIAS?]The work is advanced enough that, given a green light, a new development program with a short execution time line could be launched and start producing new power plants by the early 2020s....

“We’ve gained tremendous insight from our experience designing engines for the F-22 and the F-35, which are truly a generation ahead,” said Pratt & Whitney’s James Kenyon, senior director of advanced programs and technology, in a 2016 news release. Subsequent development—funded by the Air Force, Navy, and in-house—have yielded “tremendous progress” since 2012 and “we’re eager to move into the next phase of adaptive engine development,” he said.

That next phase is the Adaptive Engine Transition Program, or AETP, a five-year project that began last summer with $1 billion contracts each to Pratt & Whitney and General Electric Aviation. It will refine and mature technologies developed in the Adaptive Engine Technology Development program, launched in 2012 and concluding this year.

The term “adaptive” refers to an engine that can change its internal geometry to be efficient in a variety of missions and flight conditions....

...Then came ADVENT, shorthand for the Air Force’s ADaptive Versatile ENgine Technology. Started in 2007, it coalesced ideas on adaptive designs and variable cycles that engineers had been talking about for years.
In ADVENT, the Air Force funded GE Aviation and Rolls-Royce North America—the two engine-makers not then involved in the F135 engine program for the F-35 strike fighter—to work on very high-pressure ratio engine cores and adaptive, multistage fans and low-pressure sections.

Higher pressure ratio compressors can drive more core engine airflow, producing higher thrust. With computer controls, fan pressure ratios could be adjusted as needed. That meant obtaining the fuel-sipping benefits of big commercial airliner-style turbofans while being able to reconfigure an engine on the fly to create higher fan-pressure ratios needed for fighter-like maneuvers.

ADVENT and the Adaptive Engine Technology Development (AETD) program have produced impressive gains. Engine-makers have run core engines at high temperatures never before seen in turbomachinery. Meanwhile, efficiencies have been measured at record levels....

...Most importantly, the technology programs have proved the feasibility of a true “three-stream” jet engine, where the core engine airstream and fan-bypass stream is joined by a third bypass stream that flows around the outside area of the engine case. According to F135 maker Pratt & Whitney, this third stream of airflow can be put to work, improving propulsion efficiency and lowering fuel burn, or delivering additional airflow through the core for higher thrust and cooling air.

Dan McCormick, general manager of advanced combat engine programs at GE Aviation in Evendale, Ohio, explains the challenge: “How do we create thrust in a much more fuel-efficient manner in a combat environment?” Adaptive technology, variable-cycle, and high-temperature materials hold the keys to the answer, he said....

...Another advantage is in cooling. In an F135-sized engine, that third airstream could be a significant source of cooling, drawing off heat generated by sophisticated fighter aircraft equipment.

“We’ve created great, insulated fuselages made of composites and packed them with electronics that are good at making heat,” McCormick noted. “That third stream of air provides a significant opportunity” with thermal management. “It really is a game-changer; it’s not just an incremental improvement,” he asserted.

Better thermal management should make it possible for the F-35 to spend a lot of time flying at near supersonic speeds at altitudes as low as 500 feet—a feat the F-35 today is restricted from sustaining because of thermal management concerns.

In a different non-F135 engine configuration, the third stream could also do double duty. Besides helping to cool all the heat-generating onboard electronics, it could potentially create a source for as much as a megawatt of onboard power for next generation weapons and systems, such as electric lasers and high-powered microwaves....

...In the follow-on, five-year AETP, both engine-makers will design, develop, build, and test full-scale adaptive engines in the 45,000-pound thrust class. Pratt sees it as the logical extension and maturation of the next generation F135 engine it has been producing for the F-35 fighter...."

Source: http://www.airforcemag.com/MagazineArch ... ation.aspx

[spazsinbad]

P&W completes testing on F135 engine with adaptive fan
18 Sep 2017 Stephen Trimble

"Tests this year on an F135 core engine paired with an experimental fan module featuring adaptive bypass airflow to improve fuel efficient and cooling capacity “met or exceeded expectations”, says engine manufacturer Pratt & Whitney.

The testing on a full-scale powerplant for the Lockheed Martin F-35 wraps up P&W’s role under a four-year adaptive engine technology development (AETD) programme sponsored by the Air Force Research Laboratory (AFRL).

The testing was intended to understand the maturity of so-called “three-stream” adaptive turbofan technology as AFRL launches a $1 billion programme to develop a full-scale, 45,000lb-thrust-class prototype engine under the Adaptive Engine Transition Programme (AETP) that could be used to re-engine the F-35 and power a future combat aircraft....

...The AFRL is using a competitive development approach for adaptive engine technology, supporting P&W and GE Aviation through the full-scale prototype stage in AETP.

With a goal to improve specific fuel consumption by 25% compared to a 2000-baseline combat aircraft engine US Air Force and Navy have been pursuing adaptive engine technology since 2006.

The adaptive engine is designed to improve efficiency by inserting a valve in the fan module that in cruise mode opens to permit a third stream of airflow – in addition to core flow and bypass flow. The third stream increases the volume of bypass flow to make the engine more efficient in producing thrust. It also creates a new heat-sink within the engine, which allows the designers to improve fuel efficiency by increasing temperatures inside the core."

Source: https://www.flightglobal.com/news/artic ... -f-441230/

[white_lightning35]

Would I be correct in stating that the engine upgrade would have the biggest impact on the B in particular? I understand that exhaust temperatures are an area of concern for stovl operations, so wouldn't it be a big deal to lower exhaust temps and reduce the damage done to landing pads and such? Another thing that I am curious about: the thrust increase. I would think that this greatly improves the B's ability to VTO, since it can currently only carry a limited fuel load when doing so. It makes since that it might not be utilized frequently since it would put extra strain on the engine.

That said, the range and thrust increase should definitely come as a welcome boost to the A and C variants, which already have impressive capabilities in those areas.

[sprstdlyscottsmn]

the thrust increase. I would think that this greatly improves the B's ability to VTO,

Extra thrust will only help the B in vertical flight if there is a balanced increase in tailpipe thrust, roll post thrust, and lift fan thrust. Tailpipe thrust alone would be useless for vertical operations.

[spazsinbad]

Would I be correct in stating that the engine upgrade would have the biggest impact on the B in particular? I understand that exhaust temperatures are an area of concern for stovl operations, so wouldn't it be a big deal to lower exhaust temps and reduce the damage done to landing pads and such? Another thing that I am curious about: the thrust increase. I would think that this greatly improves the B's ability to VTO, since it can currently only carry a limited fuel load when doing so. It makes since that it might not be utilized frequently since it would put extra strain on the engine.

That said, the range and thrust increase should definitely come as a welcome boost to the A and C variants, which already have impressive capabilities in those areas.

AFAIK you have a misunderstanding according to this penultimate sentence quote: the F-35B is not going to VL in 'cruise mode' it will land at something like 95 to 100% thrust with a margin for controllability of the engine/liftfan/roll posts.

"...The adaptive engine is designed to improve efficiency by inserting a valve in the fan module that in cruise mode opens to permit a third stream of airflow – in addition to core flow and bypass flow...."

Any permanent VL concrete pads are designed to last 30 years with perhaps the occasional grinding of the top surface as required (a design requirement). Flat Decks have been modified/will be modified to deal with the F-35B VLs in quick succession on the same spot - otherwise the VLs can be rotated around to ease the wear and tear on unmodified decks.

Yes if the increased thrust is realized in STOVL mode - which is not cruise mode - so there is that. Other posts about other thrust increases potentially for the F-35B highlight the modifications which probably will have to be made to the STOVL engine system to benefit from any thrust increase over and above whatever is available now. Your comment about 'limited fuel load' during an F-35B is curious - please explain. Perhaps you meant 'bringback weapon load' which is OK for the required KPP whereas the Brits want to have more bringback via the SRVL which may be available on their CVFs perhaps.

The 'no cost' F135 PW engine upgrade GO 1.0 package outlined here will perhaps be suitable for the F-35B but not sure:

PW Forges Ahead With F-35 Engine Upgrade 05 Jun 2017
viewtopic.php?f=56&t=53164 OR http://aviationweek.com/defense/pratt-f ... s-next-gen

This video 1st linked by 'popcorn' in the above F-35 thread link says there will be a 5% VL STOVL lift thrust improvement BUT with a LiftFan modification as well as the 'no brainer' power module (for all F-35s) F135 engine upgrade:

[ADDITION] To add to 'sprstdlyscottsmn' comment - the roll posts will have to be able to handle any temperature increase.

[white_lightning35]

What I meant by limited fuel load is that I thought that, speaking only of vertical takeoffs, the B could only carry a rather small amount of fuel. I thought that the thrust increase would lead to an increase in fuel load for VT, if the need for it ever arises.

[bigjku]

What I meant by limited fuel load is that I thought that, speaking only of vertical takeoffs, the B could only carry a rather small amount of fuel. I thought that the thrust increase would lead to an increase in fuel load for VT, if the need for it ever arises.

The F-35B isn't really designed to do any vertical takeoffs. It's not part of the plan at all.

[spazsinbad]

IF you read about the usability of an F-35B Vertical Take Off it is clear it is meant for an emergency flight to a better STOVL take off area once sufficient fuel &/or weapons are loaded. 5% extra minimal fuel is not going to make much.

I see 'bigjku' has posted before me. The F-35B has demonstrated vertical take offs - there is a video but see my comment.

First F-35B Vertical Takeoff Test
Published on May 20, 2013 LockheedMartinVideos

"An F-35B test aircraft completes its first-ever vertical takeoff (VTO) at NAS Patuxent River, Md., on May 10, 2013. While not a capability used in combat, VTOs are required for repositioning of the STOVL in environments where a jet could not perform a short takeoff. In these cases, the jet, with a limited amount of fuel, would execute a VTO to travel a short distance."

[sprstdlyscottsmn]

This video 1st linked by 'popcorn' in the above F-35 thread link says there will be a 5% VL STOVL lift thrust improvement BUT with a LiftFan modification as well as the 'no brainer' power module (for all F-35s) F135 engine upgrade:

In terms of total lift thrust 5% is huge. That would be a 2,000lb increase. That is an increased margin for weather effects or an increase in bring back. I think it had been discussed previously that total vertical thrust subtracting empty weight yielded only 8,208lb. Obviously the bringback must be lower than this is you need a margin of power remaining to climb/arrest descent. Adding an extra 2,000 pounds to this is, again, HUGE.

[spazsinbad]

IF the F-35B modifications for the extra thrust can be made (one would think economically & testwiserly in air) then having the extra VL capability weightwiserly (I'm in an inventivewordally this morning - I'll get over it) for the Brits may make SRVL very otherworldly in an esoteric sense. Perhaps SRVLs will be a lot safer at an even LOWER KIAS etc.?

HUGE btw sounds to me as though you have been brainwashed by TRUMP! My reference was to the VTO capacity. Extra thrust at no extra expense so to speak is always good I agree. I'm hoping it all works out STOVLwise especially for the UK.

[sprstdlyscottsmn]

IF the F-35B modifications for the extra thrust can be made (one would think economically & testwiserly in air) then having the extra VL capability weightwiserly (I'm in an inventivewordally this morning - I'll get over it) for the Brits may make SRVL very otherworldly in an esoteric sense. Perhaps SRVLs will be a lot safer at an even LOWER KIAS etc.?

HUGE btw sounds to me as though you have been brainwashed by TRUMP! My reference was to the VTO capacity. Extra thrust at no extra expense so to speak is always good I agree. I'm hoping it all works out STOVLwise especially for the UK.

This is going to be Huge thrust, the best thrust, believe me! No other engine makes this kind of thrust! I checked twitter last night to be sure.

No, just that we are looking as a ~25% increase in the excess vertical thrust related to empty weight.

[spazsinbad]

Statistics huh. I guess it doesn't matter if it is installed increase or not because it is a percentage. Let us see it in action.

[neptune]

....hmmm! How might this affect the balance between the fan and the VL thrust (controls??) and also, the power rating for the fan drive components; gearbox, shaft, couplings, etc??

[sunstersun]

i don't think the f-35 B will ever take off vertically with a combat load/fuel. it's a really heavy bird.

[spazsinbad]

....hmmm! How might this affect the balance between the fan and the VL thrust (controls??) and also, the power rating for the fan drive components; gearbox, shaft, couplings, etc??

As previous posts/articles about this issue have made clear - things need to be worked out and tested/CLAWS modified.