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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Why no CFM-56 for the E3?
Why did the USAF not upgrade the E3 from TF33 engines to the CFM-56 like they did the KC135? From the Wikipedia page on the E3, the latter variants sold overseas had the CFM-56 from the factory and ...
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Why aren't ducted rotors used in gas turbines?
I am wondering why (for what I know) no gas turbine employs ducted enclosures for blade arrays on rotor stages.
I tried to search the internet for resources but I couldn't find anything related (so I'...
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Why do only turboprops have ground/flight idle selections?
Why is it that only turboprops have a pilot controlled flight/ground idle and not jets?
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How do engine doors work?
"Doors" here refers to something in or around the engine that can close or open, stopping or allowing the flow of air (or some other gas).
I've heard of such things in a few engines. GE9X ...
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Why do the engine of MiG-31 spit out flame when going for afterburner?
I was seeing this image. Always we can see an abnormal flame spit out of the engine when the pilot goes for afterburner. Why?
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Decreasing Area of Axial Compressor
in axial compressor, why the area is decreasing until it reaches the combustor?
and if the answer because of the pressure is inversely proportional to the volume. that's happened when the temperature ...
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Could a jet engine theoretically ingest not only oxidizer but fuel (on planets like jupiter)
Jet engines work by ingesting oxygen from the air and combusting it with an onboard fuel source like kerosene. But, on planets like Jupiter, with an abundance of hydrogen, would it be possible to ...
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How does momentum thrust mechanically act on combustion chambers and nozzles in a jet propulsion?
I'm asking this question since I can't intuitively understand how the acceleration of mass flow and therefore the increase of its momentum can actually mechanically act on the combustion chamber ...
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The phase having the hightest TIT for a flight mission
I have a query concerning the turbine inlet temperature (TIT) in the context of various flight mission phases. Specifically, I'm trying to ascertain at which phase the gas turbine reaches the highest ...
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Does the obstruction in a propeller duct increase exhaust pressure or decrease pressure/increase speed?
I came up with this question when looking through the answer for this question, which states that a convergent duct(obstruction) compresses the exhaust so that its pressure matches the ambient ...
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Why does thrust differ in different reference frames?
If a jet engine flies with 4 m/s in the air and we want to calculate thrust for two different reference frames, can we prove that the calculated thrust for both reference frames are equal to each ...
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What causes subtle cyclical changes in engine volume at cruise?
A few years back, while trying to snooze on a Jet2 flight up at cruising altitude, my semi-attention wandered to the droning of the engine. I realised there was a very subtle effect of its intensity ...
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Why do we take into consideration holes for pressure thrust in jet engine calculations?
In many sources related to jet engine thrust calculations such as https://www.jet-x.org/a8.html ,
pressure thrust of a module such as combustion chamber, nozzle or compressor, is calculated by front ...
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How can flow in the compressor of a jet engine go back to the inlet?
In aerodynamic lessons and books about jet engines, it is always said that there is a risk that air flow in the combustion chamber or compressor can go back to reverse direction, towards the inlet if ...
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Is diying a strong jet engine possible wih basic tools
Is it possible to manufacture a jet engine that provides 500 newtons of thrust with relatively primitive tools like a lathe or so , if someone did something similar can you provide me with the ...
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Why do we consider that air comes into jet engine?
While calculating air pressure and temperature during cruise of jet engines, we consider that air comes into the jet engine inlet with our flight velocity.
But why? In fact, air stops stagnant in ...
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What's the reason behind the 787 and 777's "thicker" engine nacelle?
If you look at images of the 777 and 787 engines (both RR & GE), such as these pics
https://upload.wikimedia.org/wikipedia/commons/thumb/e/e4/B787-2139.jpg/220px-B787-2139.jpg
https://www....
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How can over-expanded flow go out of nozzle when it has less pressure than ambient pressure?
We know that over expansion in flow means that nozzle exit pressure of flow is lower than ambient pressure at specific altitude. It gets narrower while exiting nozzle causing loss in efficiency.
My ...
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What increases the rotational velocity of air in an axial flow compressor?
In an axial flow compressor as used in modern jet engines, the goal of a compressor rotor is to increase the angular momentum of the air by imparting an increase in swirl velocity. (Note: the goal of ...
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CFM56-3 power transmission
Is lubrication system of the AGB just limited to the supporting bearings or otherwise it also include lubrication of gears?
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Do compressors and turbines in jet engines end with rotor or stator?
I am trying to understand compressor and turbine design principle based on stators and rotors.
I know that turbines and compressors both have a rotating and fixed section that constitute a stage.
For ...
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Is there any existing engine which can be converted to turbofan from turboshaft in mid flight?
I read about convertible engines. I want to know if there is any engine existing to meet up hover and cruise together.
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Do we use static pressure in thermodynamic cycles like brayton instead of total pressure?
I observed that pressure plotted in the graph above increases from 0 to 1.
0 is inlet entrance and 0' (not shown in the graph) somewhere between 0 and 1 is compressor entrance.
Now, we know that at ...
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What size jet engines would it take to make a Cessna 140 hover?
I'm building a STOL bush plane using 4 jet engines located at 4 different points on the aircraft. I would like to know what size jet engines it would take to hover something like a Cessna 140.
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Why are inlet and outlet (exhaust) pressure considered to be the same in a turbojet engine?
Why do we take outlet/exhaust pressure (station 6) as the same as in inlet (station 1) ?
In T-S diagram, we see that outlet temperature is much higher than inlet temperature since flow in outlet has ...
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Why does Engine Pressure Ratio (EPR) rise as thrust levers are pushed forward?
I'm looking for an answer that at least addresses the fundamental thermodynamics of a jet engine.
Jet engines use a Brayton cycle to get useful work out of a heat source. An ideal Brayton cycle engine ...
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Why does ITT drop drastically after startup?
Is this because of the increase of air that goes through the turbine that cools the parts?
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What is the purpose of variable stator vanes in the power turbine part of a free shaft gas turbine?
both M1 Abrams tank and T-80 tanks have free shaft gas turbine engines and both of their engines have variable stator vanes in their power turbine part. It says in the picture below that these ...
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Why the green inside newer turbofan engine nacelles?
What is the purpose of the recent phenomenon of green being seen inside newer turbofan engine nacelles, just to the front of the fan blades?
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The F104 tail pipe is not parallel to the runaway when the aircraft taxi.What is the reason?
The tail section is upward for clearance or to vector up the engine exhaust that will help to rise the nose when the aircraft take-off?
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Why does a V2500 engine sometimes report a negative oil consumption?
In engine IAE V2500 some times when I print out some reports I see a negative value beside oil consumption. Can any one explain?
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Can commercial aircraft harvest CO2 usefully and economically inflight?
The principles involved in the. railcar-based method of Direct Air Capture (DAC) as explained in the July 20, 2022 Vol 6,Issue 7 of the. scientific. magazine Joule and now being developed. by Texas ...
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Are there any aircraft that can engage thrust reversers above idle power setting?
Based on my experience with jet transport aircraft, thrust reverser levers can only be engaged after reducing the throttle to idle. Do any jet-powered aircraft exist that can engage the levers at ...
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Examples of jet turbine values for combustions, fuel flow, Q of fuel, temp of exhaust, etc. for classroom use
I am trying to build jet turbine examples for a class and I want to use actual values for the mass flow of fuel and air, combustion temps, exhaust temps, exhaust composition (CO, CO2,H20,o2, NOx) ext…
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What is the optimal jet engine size for maximum range? [closed]
I under stand the flying wing has been calculated to have an optimal length. Is their an optimal blade length within a turbine engine for planes as well?
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Why do air planes not have a "grating" in the front of the jet engines for safety? [duplicate]
This is what a typical jet engine looks like:
Considering the horrible dangers with birds getting in there and crashing planes, why doesn't it look like this?
Why don't they have a "grating&...
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Why do jet engines have a maximum speed?
What's the scientific background behind a jet engine's top speed? Jet engines increase efficiency at higher airflow rates, so why does the efficiency stop increasing at some point?
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Are boundary layer diverters for jet intakes only required for supersonic speeds?
For subsonic aircraft (Mach 0.7), Is boundary layer diverter a necessary requirement for jet intakes? A lot of legacy aircraft were flying without them.
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RR Ultrafan: Why the dramatic change of fan blade design?
The Rolls Royce Ultrafan prototype has been in development for a few years and has usually been seen in the media with very distinctive curved leading edge design as such:
However, this week (...
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Why do turbine rotors have an outer shroud but compressors don't?
I know it's purpose is to prevent interstage leakage of pressurised gases, but then shouldn't the compressor stages have it as well? Why is it exclusive to the turbine stages?
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Why are turbine blades made thicker with great curvature and more streamline than compressor blades?
I can`t think it is about material limitations or aerodynamics
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Can Rotating detonation engine be combined with turbofan engine and if so how would it look like and it is economically viable?
All the material I could find is about Turbofan PDE Hybrid and Gas Turbine with Rotating Detonation Chamber.
Also how much percent of the estimated fuel will RDE Turbofan hybrid save compared to ...
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What is the difference between auto-start and manual start in an A320?
What is the difference between auto-start option and manual start in the Airbus A320?
Can you please explain
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What does the Permanent Magnet Alternator do exactly and how works?
From T6b Naval manual:
A dedicated permanent magnet alternator (PMA), mounted on the reduction gearbox, powers the PMU. The PMA supplies 32 VAC, which the PMU converts to DC. The PMU automatically ...
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What is the difference between annular flow and axial flow engines? [duplicate]
What is the difference between annular and axial flow in a jet engine? Are there other type of flow types?
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Why is the inlet cone on some subsonic engines conical (sharp)?
An inlet cone, as far as I know, is a component on an engine to guide the intake air smoothly into the compressor stage of a jet turbofan engine, it performs as a fairing(aerodynamic covering)of the ...
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Why afterburner fuel nozzles aren't creating a lot of drag during normal operation?
I cannot understand how afterburner fuel nozzles are not crating a lot of backpressure and allow engine to work when afterburner is not in use? They close almost 50% of the exhaust area. Is there any ...
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Why are spins not allowed below 10k ft msl in the T6b?
Reading through the manual I see that spins are not allowed below 10000 msl in this turboprop aircraft, the t6b, the reason that is written in the manual is as follows, quote:
"Spins below 10k ...
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What originally spins the intake fan when the engine is started?
I've been thinking about doing a presentation about how jet engines work. I've watched some videos and everything seems understandable to me, but I have one question. What originally starts spinning ...
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Hypothetical Ramjet-Scramjet-Rocket Combination?
Theoretically, could a ramjet-scramjet-rocket combination exist that operations like a rocket for taking off(below operations speeds from the ramjet or scramjet) or in space, and then switch to ramjet/...
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