How much does a new engine for a 787 cost?
MolaKule Q&A on Aircraft Structures VII Engines
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MolaKule
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All that are the offerings.
MolaKule
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Good grief man just scroll down to:
https://thepointsguy.com/airline/powering-the-dreamliner-how-the-787s-genx-engines-work/
"Creating Thrust
The GEnx is a massive bit of kit. The front rotating fan measures 9.2 ft across. The whole engine weighs 13,200 lb and can produce 76,100 pounds of thrust (a pound of thrust is equal to a force able to accelerate one pound of material 32 feet per second per second.)Let's break that down: 32 feet per second is the same as the force of gravity — 9.8m/s². Therefore, if an engine could produce 2.2 pounds of thrust, it could accelerate a one-kilogram block at 9.8m/s². At the maximum thrust which the GEnx can generate, it can accelerate a 76,100-pound block at the same rate. Pretty powerful indeed.
And how much does all this cost? Just a casual $28 million.
This all sounds really impressive, but how exactly is this massive force created? It comes down to four distinct parts that can be described with four verbs: suck, squeeze, bang and blow.'
I guess those are the cheap ones? I saw some jet engine prices into the 50 and up to 100 million range, when I hunted for such many months ago, never saved the links so? I know some of the small jet engine, parts are very costly. In the late 90's worked on parts that 5 may have fit in a lunch box that cost from 10k to 20 some K for the smitch larger ones. Same type of parts now are likely double that.
MolaKule
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@Cujet "A gas turbine engine runs or self sustains, when we combust fuel, because? It is a very, very simple question, with an incredibly simple answer. But I've seen many engineers misunderstand the basics."
Yes! Now the question I posed is an interesting one, because we need not combust fuel to self sustain the turbomachinery and have a 'running engine'. For example we could inject pressurized air into the combustion chamber to mimic the expansion of combustion. With no added heat what so ever...
...Anybody else want to try and answer my question? I promise the answer is in the picture I posted. Hint, look at the height of the compressor tips vs. the turbine tips. And then think of pressure."
Awaiting your explanation.
Yes! Now the question I posed is an interesting one, because we need not combust fuel to self sustain the turbomachinery and have a 'running engine'. For example we could inject pressurized air into the combustion chamber to mimic the expansion of combustion. With no added heat what so ever...
...Anybody else want to try and answer my question? I promise the answer is in the picture I posted. Hint, look at the height of the compressor tips vs. the turbine tips. And then think of pressure."
Awaiting your explanation.
Because the energy absorbed by the turbine wheel equals or exceeds the energy needed to drive the compressor.
There you go!
In the picture I posted, the turbine blades are larger in area than those of the compressor. Since they both see similar pressures (for this discussion), the turbine produces more torque.
Put another way, as soon as some form of expansion occurs (combustion in the case of a typical gas turbine) the compressor loads the shaft, as does the turbine. One of them must win.
My picture provides a visual example. In the case of more complex engines, the same situation exists, complicated by differences in diameter, blade height, stages and so on.
MolaKule
Staff member
In turbine engine design, there is no such thing as a self-sustaining engine.
Engine components can only function (rotate) when the energy from combustion exceeds three things: 1. inertial mass of rotating components, 2. bearing friction, 3. moving air masses through the engine.
As to your picture from post #36, this is a centrifugal compressor/turbine combo. The vast majority of turbofan engines use axial flow design and components as explained in post #28.
As far as I can observe from post #36, the turbine impeller blades have slighty longer chords than the compressor blades in order to capture as much combustion energy as possible.
MolaKule
Staff member
For engine placement on a low-wing aircraft, what is another consideration with respect to main landing gear position?
MolaKule
Staff member
Jet Engine Problems with P&W 1000 series:
"Pratt & Whitney has recalled a significant number of its PW1000G geared turbofan (GTF) engines due to a manufacturing defect affecting certain high-pressure turbine and compressor components. This has led to the grounding of numerous aircraft, including models from the Airbus A320neo family, A220, and Embraer E-Jet E2, that are powered by these engines..."
https://simpleflying.com/most-affected-us-airlines-pw-grounding/
"Pratt & Whitney has recalled a significant number of its PW1000G geared turbofan (GTF) engines due to a manufacturing defect affecting certain high-pressure turbine and compressor components. This has led to the grounding of numerous aircraft, including models from the Airbus A320neo family, A220, and Embraer E-Jet E2, that are powered by these engines..."
https://simpleflying.com/most-affected-us-airlines-pw-grounding/
MolaKule
Staff member
You don't want an engine placement such that hot engine air heats up the tires, the hydraulic fluid, or the landing gear mechanisms.
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And FOD.
MolaKule
Staff member
Which is why you want to place the main landing gear inboard and behind the wings.
MolaKule
Staff member
New Question: What are the advantages and disadvantages of "chevrons" at the rear of the engine nacelles?
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My understanding is that the chevrons are for noise abatement. How this works, I can’t explain.
The engine core (but not the aft fan cowl, as in that GENX) on the CF34, as used on the Embraer E-Jet, has this design.
But I would guess that they reduce thrust, compared with a non-chevron design.
MolaKule
Staff member
Yes, Noise reduction is the primary reason for chevrons. They do have a small drag penalty of about 0.5%.
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That's something the designers of the original 737 probably wish they gave more consideration. The P&W JT8D engine had a tiny cross section when compared to today's massive high-bypass turbofans, something they were likely unable to predict in all fairness. The rather short landing gear created a challenge to the future engineers who had to shoehorn engines of an ever-increasing diameter into the fixed amount of space between the wing and the ground. "Simply" lengthening the landing gear would have required a major and expensive redesign, and maintaining the original designation was important to prevent any potential FAA recertification requirements or addition pilot training, all of which added costs and made the aircraft less marketable.
This eventually bit them in the butt with the MAX. In order to fit the CFM LEAP engines, with their 69.4" fans, under the wing they had to push them way forward and up. This altered the flight characteristics enough to require special software to maintain stable flight (the infamous MCAS), and we all know what happened after that. I guess some people just have to learn the hard way.
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