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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30
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3answers
93k views

What material is used to make the hot sections of jet engines?

What metal alloy is used for the hot section of a jet engine? Specifically the exhaust nozzle? I have found mention of a titanium alloy and nickel alloy but nothing with that much detail. What sort of ...
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Why in a CFM56-3 is vibration measured in displacement for N1 and in velocity for N2?

N1 is measured in mils (thousandth of an inch) and N2 is measured in IPS (inches per second). Why are different methods used?
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2answers
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What does a High Pressure Turbine Clearance Control do?

In CFM56, I read that it is supposed to increase HPT performance but I don't know how it does that.
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1answer
151 views

How do variable bleed valves prevent surge?

All I know is that the valves open at low speed or when decelerating, and close at high speed or when accelerating. How do they prevent the compressor from stall or surge?
3
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1answer
164 views

Are turbine blisks common in jet engines?

This comes from a slightly related question about blisks. A blisk is a single component shaped like a disc with blades on it. This can be for compressors or turbines. I want to ask about the turbine ...
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3answers
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What is the transient bleed valve in a gas turbine engine?

What is a transient bleed valve and what's its purpose ? Also, can you explain the purpose of bleed valves in general?
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1answer
414 views

Why is turbine inlet temperature called "TET"?

I assume that at some point giggling engineering students caused their instructor to change "turbine inlet temperature" from TIT to TET, but I wonder if anyone knows the real reason and ...
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2answers
1k views

Do jet fighters use Turbojet engines, and do cargo/passenger aircraft use Turbofan engines? [duplicate]

I have a feeling that Turbofan engines are used in jet fighters and Turbojet engines are used in cargo or passenger aircraft. Is my perception correct? Do jet fighters use Turbojet engines? Do cargo/...
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0answers
191 views

What is the highest operational ceiling for a nuclear scramjet?

A similar question is: What is the highest operational ceiling for an air-breathing jet engine? The answers point to scramjets. Cited reports focus on combustion kinetics. The Wikipedia Scramjet page: ...
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1answer
104 views

In a jet engine, what is the significance of the stagnation pressure/temperature?

I'm reading a paper on jet engines that repeatedly mentions the stagnation pressure and temperature. What does this mean? Is it the point where the jet engine stalls in performance/efficiency/thrust, ...
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5answers
675 views

What is the principle behind flight of airplanes? [duplicate]

What is the principle behind flight of airplanes? Need a simple answer for grade 7 student. Thank you
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3answers
161 views

How does bypass air work?

As far as I’m aware, high-bypass engines have far higher fuel efficiency than low-bypass engines, and as a result the effective specific impulse of the engine is increased. What I’m trying to figure ...
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1answer
200 views

Aircraft engine communication with satellite

Do pilots get an audible indication when the engines are communicating with the manufacturer whilst in flight. Do these "pings" or "hanshakes" begin on start up and are they always ...
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1answer
188 views

What is this sound for when starting the engine of an F-15?

If I remember correctly, to start up old fighters such as F-4s, you need an ASU but it looks new fighters do not need an ASU. Today, I was watching this video. It's a so cool video to know how new ...
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3answers
312 views

How are compressor disks connected to the shaft?

I am trying to learn how compressor disks and shaft are connected each other. I don't have any idea about the terminology so I couldn't find anything useful. Here is a section view of a sample and I ...
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1answer
179 views

Need help with calculation of engine airflow and jet velocity and efficiency

This is an image of a set of questions that are relevant to an Airbus A380 type of aircraft (4 engines): As the answers are incorrect, I'd like to understand how these need to be calculated. Q1) I ...
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6answers
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What is some of this extra "stuff" on jet engines?

At the risk of sounding too broad, I want to better understand the complications of jet engines. This time, I'm asking about extra "stuff", which unfortunately I have no better name for ...
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2answers
187 views

What were/are the military designations of the JT8D and PW4000?

Turbine engines on U.S. military aircraft, in addition to their manufacturer-given names, receive separate designations (consisting of J [for turbojets], F [for turbofans; formerly TF], or T [for ...
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1answer
3k views

What are those half-vanes in the engine inlet of a 707-328?

I just saw this: Source They look like IGVs but I'm not sure. What could those be? Do you know the engine?
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4answers
30k views

How does the mounting location of a jet engine affect aircraft performance?

Different jet airplanes mount the engines in different ways. For example: Under the wing To the fuselage How does the engine location affect aircraft performance? Is one better than the other?
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0answers
275 views

What is that to and fro moving thing?

This video by AgentJayZ is the maintenance and repair of AI-25 turbofan. What is that thing moving due to applying certain pressure to that pipe? Can anyone describe its purpose and how it works?
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1answer
10k views

How much air, by mass, enters an average CFM56 turbofan engine cruising per minute?

How many kg of air enters an average CFM56 turbofan engine cruising per minute? I have looked everywhere and cannot find it or figure out how to find it, if you could either tell me or give advice on ...
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0answers
130 views

Overheating (fire thrown out of the nozzle) [closed]

At first I copied https://www.jetcat.de/en/productdetails/produkte/jetcat/produkte/hobby/Engines/P160_rxi_b Where I manufactured and installed all the parts and they are very similar to the original ...
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0answers
38 views

How are Fan pressure of and Static pressure in the turbofan engine related?

If the fan air is ducted to the rear, the total fan pressure must be higher than the static gas pressure in the primary engine's exhaust, or air will not flow. By the same token, the static fan ...
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3answers
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Which commercial aircraft can perform a parallel engine start?

In various Youtube videos, e.g. this one, one can see that the Boeing 787 is capable of a parallel engine start (both engines are started at the same time). Are there any other commercial aircraft ...
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2answers
331 views

What is a good place to start learning about pulse jets?

I'm a student who is curious about designing his own pulse jet engine, I am wondering if there are any schematics designs, notes, and other related materials I could/should study to learn about these ...
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1answer
97 views

Why is it that low fuel gauge is one indication of a compressor stall?

I am reading from my gas turbine engine class notes that apparently, one indication of compressor stall (besides the banging sounds, torque gauge low, N1 low, ITT gauge up, etc) is the fuel levels ...
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0answers
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why are modern rotor airfoils placed and set up in a compressor at a higher angle of incidence?

why is it that in modern compressors in gas turbine engines like the J79 the rotor blades are set up at a higher angle of incidence (more aligned to the axial axis) compared to older engines. I also ...
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7answers
27k views

Are German, Japanese, and Chinese companies not able to build aircraft jet engines on their own?

As far as I know, only 4 countries can build aircraft jet engines on their own: USA {GE, P&W} Russia {Klimov, NPO Saturn} France {Safran} UK {Rolls-Royce} All other countries use jet engines ...
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1answer
3k views

Does a jet engine keep running when it can no longer be controlled from the cockpit?

On the Qantas Flight 32 incident, the Airbus A380's number two engine encountered an uncontained rotor failure and partially damaged the controls of number one engine as well. According to Wikipedia, ...
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1answer
156 views

Can liquid hydrogen be pumped directly into a jet engine without a heat exchanger? Is it burned as a gas or a liquid in the combustion chamber? [closed]

This NASA research paper on H2 engines includes a diagram of Wesley Kuhrt's 1956 design for a hydrogen-fuelled engine, which has no heat exchanger: (Image by United Technologies Corporation, via NASA....
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7answers
8k views

Why are contra-rotating jet engines so rare?

Why are contra-rotating jet engines so rare? Such a jet engine would have contra-rotating turbines, or contra-rotating compressors, or both. In fact I cannot think of even one aircraft that has this. ...
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1answer
161 views

Why is a combustor in a gas turbine engine asymmetric?

As the above question stated, the upper and lower section of the combustor isn't same. Is there any reason behind it? Due to which the cooling of the combustor is also different in the upper and lower ...
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1answer
5k views

Why Western fighters' afterburner glow is reddish orange while Eastern Bloc fighters' is blue?

Recalling what little physics I know, this could be explained by two factors: The blue color is given by the characteristic EM radiation of C-H bond breaking, C- and H- radicals forming and ...
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1answer
108 views
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1answer
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Would mid-air refueling for an air-to-space vehicle that flies like a plane be a viable advantage if the tech was available? [closed]

Let's take the style of an F-22 Raptor (awesome!), build the fuselage, wings, etc to handle runway takeoff horizontally and then vertically (if needed) up to orbital space flight to reach the ISS in ...
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1answer
4k 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 ...
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1answer
314 views

What are the "beta lines" of a gas turbine engine component?

For a compressor in particular, what do the beta lines represent? I know for a compressor map you have the lines of constant spool speed, and the contours of isentropic efficiency. I also understand ...
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2answers
233 views

Why doesn't a hot jet engine crack at 10,000 metres and -50 C air temperature?

I have seen videos of red hot jet engines being tested at sea level in a building. But even in a building the temperature difference between the engine and the room is large. Most materials would ...
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3answers
392 views

Is there any mechanism in engine mount to prevent shock loads on engine while landing?

How engine is mounted in wing is restricting motion in any direction but is it still resistant to shock loads, or is there any mechanism inside engine associated to bearings that will absorb shock ...
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3answers
84 views

What other materials apart from conventional nickel and steel superalloys can be used as a first stage turbine blade material?

Steel and nickel chromium alloys have been prominent and most used as turbine blade material although there are other materials such as tantalum carbides, tungsten and many more which I have no ...
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2answers
3k 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., ...
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0answers
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Why does the CFM LEAP have so many LPT stages? [duplicate]

With the core power being similar, intuitively, the higher the number of turbine stages, the more energy is absorbed, the higher the RPM. But the PW1000G vs CFM LEAP (both engines have similar thrust ...
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3answers
487 views

Is it feasible to replace a C152's engine with multiple small turbine engines?

If I wanted to remove the piston engine from a cheap plane like a Cessna 152 and add small turbine engines with an equivalent thrust but weighing less, where would be the best place structurally to ...
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4answers
4k views

Can I simply use multiple turbojet engines to fly supersonic?

the jet engine FJ33 produced by Williams International produces around 6 kN thrust (maximum, at sea level). Imagine: to fly supersonic, I need for my aircraft 9 kN of continious thrust. I am wondering ...
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2answers
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Does the APU consume a lot of fuel compared to a jet engine?

I would like to know whether the APU of modern commercial airliners consumes more or less fuel than a jet engine. Of course, this will vary between aircraft types, so what comparisons in fuel usage ...
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1answer
800 views

How are compressor blades connected to the shaft in turbojet engines?

The below figure is about rotor and stator blades of compressor . How these are connected to the compressor shaft in jet engines ?
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2answers
3k views

How much thrust is lost due to the bleed air system?

I've read that bleeding air for the pneumatic system from the engine core can produce important losses in thrust, and also rising the fuel consumption too. Today this problem is worse, with the more ...
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3answers
6k views

What is meant by a “cold soak" of an APU?

What is the exact meaning of "cold soak" of an Auxiliary Power Unit (APU)? Is it to do with long flights at high altitude and the fuel getting cold? Will it affect the ignition of the APU? Can anyone ...
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1answer
86 views

How to determine the number of compression stages given a compression ratio?

I have a personal project to design a gas turbine engine, the main problem that puzzles me is how do I determine the pressure rise in each stage of an axial compressor? Say, I'm planning on a 38:1 ...

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