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Questions tagged [jet-engine]

Engines which propel aircraft via "jet propulsion", i.e. by expelling high-velocity gasses (usually primarily air) through propelling nozzles.

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1answer
251 views

What material is used to make engine covers for passenger airliners?

What material is used to make the engine shrouds for passenger airliners?
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1answer
197 views

Would it be feasible to use graphene in the gearbox of a large turbofan engine?

What is the possibility or are the drawbacks of substituting graphene for metal in a gearbox of a geared turbofan the size of a Trent 900, given its strength properties(graphene), harder than a ...
6
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1answer
807 views

Why does it take so much fuel to start a jet engine?

I just watched an Abrams tank documentary and it said something like it takes "1 liter of fuel for every mile but 39 liters for a startup." Is it true of turbine engines in general that they need a ...
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2answers
408 views

What are the pros and cons of adding a gearbox to larger jet engines?

What are the merits and demerits of adding a gearbox to larger jet engines like the Trent 900. If its about torque, why not use a magnetic gearbox? What are the demerits of using magnetic gearboxes ...
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1answer
154 views

Could adding a gearbox to the Trent 900 improve the efficiency of the A380?

Could adding a gearbox to the Trent 900 improve the efficiency of the A380 so that it performs better than a smaller jet, i.e with economies of scale? Is the absence of a gearbox in the Trent 900 the ...
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3answers
292 views

Does a trent 900 engine have the ability to spin extra or more fans?

Given that the most modern geared turbo fans gear down spinning the fan, which essentially translates to requiring less torque or horse power to spin the fans. If the gearing down is in the magnitute ...
8
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3answers
495 views

How can engine positioning affect flutter tendency?

I understand that moving the engines towards the wingtips would increase flutter tendency, but are there any other positioning options which could affect flutter? How about moving the engine ...
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2answers
2k views

What engine are these fan blades from?

I bought these from a metal scrapper and paid about $30.00 total figuring they're worth more than that in cool factor. Problem is they aren't nearly as cool if I can't figure out what engine (and ...
5
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1answer
3k views

What throttle setting does an airliner use while cruising?

As a passenger, I have always felt like the engine are not kept at take-off thrust/full throttle a few (tens of) seconds after take-off, and so for obvious reasons as fuel efficiency, engine wear ...
4
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1answer
201 views

Is it possible for an airliner to cruise at engine full thrust?

What would happen if the pilot of a modern airliner like the boeing 747-800 or Airbus A380 left the throttle at full thrust at cruise altitude for an extended period of time e.g 4 hours if the ...
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1answer
179 views

What is the diameter of a Trent 900 engine?

What is the diameter of a Trent 900 engine, i.e the diameter of the fans, from one fan tip to the one that is directly opposite it? What is the radius of the fan or the the length of each fan blade?
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1answer
443 views

How much water is carried for jet engine water injection?

An answer on a related question stated that water injection was used on some of the early jet planes, for example Boeing 707 and Boeing 747-100/200. I presume the water is stored in some tank. How ...
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3answers
965 views

What is the purpose of blades on a compressor?

What is the point of having blades on a compressor. I heard on NASA that it alters the flow but how would this help. As the flow of a fluid increases, the pressure decreases, and vice versa. The ...
8
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1answer
573 views

How dangerous would it be to start a jet engine with coins inside?

With the multiple stories in the news of people throwing coins into a jet engine for good luck, I couldn't help but wonder how dangerous it would be if the act went unnoticed and the crew started up ...
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0answers
124 views

Why are there curved blades on jet engines? [duplicate]

On the fan and comssorssor and turbine for that matter there are blades and they are also curved. Im already confused beucase the fan has blades but wouldn't it blow out air not suck in air? Why are ...
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2answers
641 views

What materials are suitable for making a mini gas turbine engine?

What materials are suitable for a mini/model gas turbine engine, specifically the fan, compressor, combustion chamber and turbine?
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1answer
654 views

What is a TAPS combustor and how does it differ from any other annular combustor? [duplicate]

I found out that the GEnx engine uses a TAPS (Twin Annular Premixing Swirler) combustor. Is it a single or dual annular combustor ?
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2answers
383 views

Can a turbofan maintain torque when spinning fast?

I assume turbofan fan rpm could be increased only when: Using most modern jet engines (Airbus A380 and the Boeing B747-800) Using a magnetic gearbox which can handle more torque dor the same weight ...
4
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1answer
343 views

Why use jet engines instead of propellers when designing new airplanes?

I'm looking at the 100 people project and I am looking at clean airplanes. Why did we stop using a clean source of lift, the propeller?
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1answer
1k views

What is the highest operational ceiling for an air-breathing jet engine?

An air-breathing jet engine can only operate at relatively low altitude, where the atmosphere is dense enough. However, some jet-powered aircraft can operate at an altitude higher than 20 Km (e.g., ...
6
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2answers
1k views

What is the origin of the term “military power”?

An engine producing 'dry' thrust is said to be at 'military power', a useful distinction from reheat / afterburner. It's always seemed an odd phrase to me. There's nothing particularly military about ...
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3answers
1k views

What is Engine Pressure Ratio?

I kind of know what it is but I don't fully understand it. Wikipedia says, the engine pressure ratio (EPR) is the total pressure ratio across a jet engine, measured as the ratio of the total ...
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3answers
860 views

Is it practical to integrate turbofan or ramjet engines into an airliner wing?

The de Havilland Comet had turbojet engines integrated into its wings, such that its nacelles were mostly flush with the wings like so: (wikimedia.org) I recognize that turbofan engines are ...
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1answer
2k views

How does the FADEC prevent compressor stall during rapidly increasing thrust demand?

My understanding is that if the demanded thrust is increased rapidly on a jet engine (for example going from nearly idle to TOGA during a go-around), the engine will likely experience a compressor ...
12
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1answer
281 views

Did some early jet engines catch on fire at higher power settings?

Recently I've being playing some IL-2 1946, and in this flight simulator jet engines had a strange problem where if I suddenly throttle up more than 60% the engines would catch on fire. Is this a real ...
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2answers
1k views

Why are the B-52 thrust levers advanced inside-out?

As I understand, the standard procedure for advancing the throttle (for take-off) is as follows: Advance throttle to desired engine input & output (N1 & N2) Release brakes Gradually increase ...
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2answers
226 views

Can heat from the engine inlet be used to produce thrust?

As the engine inlet temperature increases, Is more heat energy provided by air? if yes then can we utilize that heat energy to produce more thrust?
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1answer
70 views

What is the link OR difference between change in momentum & pressure difference?

I ask in regards to the the thrust formula, which includes change in momentum, as well as difference in pressure between inlet & outlet of the engine to calculate generated thrust; this implies ...
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1answer
598 views

Does an increase in inlet temperature affect fuel flow and power output?

The fuel flow rate decreases as the inlet temperature of the air entering the engine increases. Will the engine produce same amount of power as when the fuel flow was higher?
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1answer
687 views

Why does lower atmospheric pressure produce higher EPR (thrust)?

Recently, I read manual about engine, PW JT8D-217A/C, and there is a chart making me so confused. Manual show the reference table tells you what number, EPR, is normal in specific temperature and ...
3
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1answer
451 views

Is hypersonic flight possible with a Busemann's Biplane?

The modifications to the Busemann's Biplane design reported in this article have proven that it is possible to design a modified Busemann's Biplane wing design that actually produces lift at ...
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5answers
2k views

Is water a possible fuel for jet engines?

Jet engines can run on almost any fuel, and the operating temperatures of modern jet engines' hottest sections are anywhere between 3000 and 3150 degrees F (1648 and 1732 degrees Celsius). Does that ...
0
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1answer
318 views

Bypass ducts and spinning blades [duplicate]

I want to start out by saying these questions will make me look a fool but i simply haven't found answers for them anywhere so i'm hoping you could help me! What is the purpose of bypass ducts? If ...
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8answers
4k views

What would be the drawbacks of using a rotating engine as thrust reverser on airliners?

What are the drawbacks for having engines mounted on an aircraft such that their direction can be hydraulically controlled for best performance and efficiency? The idea would be to turn the engine 180 ...
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3answers
776 views

How much weight does a thrust reverser add?

How much weight does a thrust reverser add to an engine? Let's take the CFM Leap 1B as an example, which powers the new version of the Boeing 737. This engine can produce up to 130 kN of thrust for ...
17
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2answers
7k views

Where is the generator in a large turbofan of a commercial airliner?

So, where do you put the electrical generator? If it's gonna be coaxial, the only place is the rear (it will be burnt) or the front (it will get in the way of intake). If it's gonna be coupled to a ...
4
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2answers
689 views

Are there turbofan/turbojet analogues to a centrifugal-compressing jet engine?

Axial-compressor jet engines fall into two categories (and only two as far as I'm aware): turbofan and turbojet. I'm wondering if centrifugal-compressor jets also have such a distinction or something ...
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2answers
476 views

Will manually removing nicks from compressor blades significantly affect the operation of the compressor?

I've recently found a channel on Youtube where a jet engine technician goes into great detail about the work he does on maintaining and repairing jet engines In this particular video (and also an ...
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2answers
585 views

What is the operating temperature of a turbo bypass engine, and how is it kept at that temperature?

What is the operating temperature of a turbo bypass engine? If advancements were made to materials through material science for the internal components would increasing the operating temperature ...
5
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1answer
963 views

What fraction of air intake becomes bleed air in airliner engines?

Gas turbines typically bleed air from the late compressor stages. Some of this air bypasses the combustion chamber and is expanded through the turbine to prevent the blades from becoming too hot. I ...
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1answer
800 views

What is the longevity and replacement schedule for turbine engine blades?

I'm trying to understand how frequently hot section turbine engine blades are changed out. Is this a calculation based on flight hours, material, engine size or maybe something else? Apologies if ...
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3answers
1k views

Can a jet engine benefit from nitrous oxide boost?

I just read this wiki article again about the GM-1 boost system. This was used in Nazi planes during WW2. It injected Nitrous Oxide (N2O) into the supercharger of the piston engine. The idea was to ...
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1answer
192 views

Viability of Magnetically started engines [closed]

I am working on a school project of mine which involved testing the viability of a magnetically started jet engine. By magnetically started, I mean that there are magnets which accelerate the main ...
5
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1answer
450 views

How do the engines of a multi-engine airplane shut down after fuel starvation?

If a multi-engine aircraft runs out of fuel, can the engines flame out at different times due to fuel inequality between the tanks, or do they both die at the same time because fuel is constantly ...
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2answers
4k views

How common is engine failure?

What are the failure rates for piston, turbine, and jet engines? (If more subdivisions of "engine" are necessary to make the data useful, please point them out).
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2answers
5k views

Why do jet engine fan blades have a twisted shape?

is this a good answer. the blades rotate, the tip moves faster than the hub. So to make the blades efficient, the blades are usually twisted. The angle of attack of the blades at the tip is lower than ...
6
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1answer
249 views

Since when are ground-based starting devices no longer in common use? Are there any jetliners flying that would still require them?

Nothing is written in Wikipedia on how the engines of the De Havilland Comet or other similar airliners were started. However, it seems that aircraft of this generation could not start the engines ...
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3answers
1k views

Which engine(s) do airliners taxi with? [duplicate]

I have read that pilots only taxi on 1 engine to save fuel. Which engine does a twin engine jet such as a 737, 777, a320 or similar use to taxi? Left or right, or does it vary by pilot or some other ...
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3answers
3k views

Why weren't the Airbus A330 engines designed with a system to stop their fans?

Why wasn't the Airbus A330 designed to stop its fans (with some kind of 'handbrake')? To clarify, I am specifically talking about the aircraft that flew Air Asia flight D7237. During the flight the ...
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2answers
349 views

Could an airliner get better fuel efficiency at higher altitude? [duplicate]

By higher I mean like 60k feet instead of 30k. Seems like the rate limiting step is engine performance at 60k feet. Are people working engines that can operate at higher altitudes? How close are we ...