Questions tagged [jet-engine]

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

Filter by
Sorted by
Tagged with
10 votes
6 answers
3k views

Function of the compressor in a gas turbine engine

I am trying to understand the importance of having compressed air in the combustion chamber of a gas turbine engine. As far as I understand it, the reasons are twofold. Firstly, the compressor is ...
bchen's user avatar
  • 103
3 votes
0 answers
105 views

What legacy turbojet would have detailed documentation and drawings available for free or cheap?

I am fascinated by the technology of jet engines. As a hobby, I might like to create a detailed animated 3D model of one (and publish it with a Creative Commons license). Obviously I am not going to ...
tml's user avatar
  • 746
0 votes
1 answer
75 views

Why are these characteristics of the FT-180 highlighted?

I have been checking the FT-180 engine used to establish speed record for remotely controlled aircraft (i.e. model airplanes). There are some specific features highlighted on the manufacturer site. I'...
totalMongot's user avatar
9 votes
4 answers
6k views

Why are there (almost) no civilian single engine jet aircraft?

I have been looking at various engine configuration in jet powered aircraft. Most have 2 jet engines mounted either side of the fuselage, there are trijet models (e.g. B-727, MD-11) there are also 4-...
Aleks G's user avatar
  • 455
2 votes
0 answers
156 views

What’s the difference between a compressor stall and a surge from the cockpit?

I understand the difference between a compressor stall and surge. Stall: One or two blade stages exceed the critical AoA, the airflow is turbulent, and the smooth airflow through the compressor is ...
Breaach's user avatar
  • 151
1 vote
1 answer
127 views

why you have to open 6 bypass valves in the J 58 engine?

I've noticed that the bypass valves in J-58 are opened after M=1.6. I don't understand why and what are the differences between the J-58 and a normal turbojet that reeaches more than M=1.6.
marco iob's user avatar
1 vote
1 answer
196 views

What are the air source settings for on the F-16?

As part of the start up sequence for the F-16, the "air source knob is set to NORM", according to this source: https://theaviationgeekclub.com/heres-why-starting-the-engine-on-an-f-16-viper-...
AlphaCentauri's user avatar
12 votes
3 answers
2k views

Does the other engine have to go through extra checks when one engine fails

Many times I read articles on sites like aviaton herald about engine shutdown in fight because of some problem. It's given the problematic engine will be repaired. Question is about other working ...
user871199's user avatar
  • 1,817
1 vote
3 answers
227 views

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 ...
RetiredATC's user avatar
  • 1,725
0 votes
2 answers
219 views

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'...
temporary_pigeon's user avatar
9 votes
1 answer
1k views

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?
Boeing787's user avatar
  • 6,322
2 votes
1 answer
188 views

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 ...
DrZ214's user avatar
  • 17.6k
2 votes
1 answer
217 views

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?
Roh's user avatar
  • 3,317
0 votes
1 answer
120 views

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 ...
Nagy Ashraf's user avatar
9 votes
2 answers
5k views

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 ...
Daniel Shepherd's user avatar
5 votes
3 answers
781 views

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 ...
MK.s's user avatar
  • 65
2 votes
1 answer
143 views

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 ...
mumu's user avatar
  • 21
1 vote
2 answers
126 views

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 ...
Frank's user avatar
  • 415
-1 votes
2 answers
144 views

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 ...
Jawel7's user avatar
  • 244
3 votes
1 answer
168 views

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 ...
Cantoris's user avatar
0 votes
1 answer
103 views

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 ...
Jawel7's user avatar
  • 244
3 votes
3 answers
806 views

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 ...
Jawel7's user avatar
  • 244
-4 votes
2 answers
123 views

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 ...
Ahmed Radwan's user avatar
-1 votes
4 answers
3k views

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 ...
Jawel7's user avatar
  • 244
2 votes
0 answers
166 views

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....
Piranha Lama's user avatar
1 vote
0 answers
78 views

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 ...
Jawel7's user avatar
  • 244
0 votes
1 answer
108 views

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 ...
interested22's user avatar
2 votes
0 answers
278 views

CFM56-3 power transmission

Is lubrication system of the AGB just limited to the supporting bearings or otherwise it also include lubrication of gears?
DYNAMICS's user avatar
1 vote
1 answer
185 views

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 ...
Jawel7's user avatar
  • 244
2 votes
1 answer
187 views

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.
Eaza's user avatar
  • 101
0 votes
0 answers
38 views

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 ...
Jawel7's user avatar
  • 244
6 votes
3 answers
334 views

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.
bryan lawless's user avatar
1 vote
2 answers
207 views

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 ...
Jawel7's user avatar
  • 244
3 votes
1 answer
364 views

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 ...
youguysfail's user avatar
1 vote
1 answer
125 views

Why does ITT drop drastically after startup?

Is this because of the increase of air that goes through the turbine that cools the parts?
Boeing787's user avatar
  • 6,322
1 vote
1 answer
649 views

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 ...
Timothy Scherer's user avatar
9 votes
1 answer
487 views

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?
minijet88's user avatar
  • 151
0 votes
1 answer
132 views

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?
George Geo's user avatar
  • 2,101
0 votes
0 answers
70 views

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?
Akeel's user avatar
  • 1
0 votes
4 answers
386 views

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 ...
user avatar
7 votes
2 answers
297 views

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 ...
SMS von der Tann's user avatar
1 vote
1 answer
74 views

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… ...
Michael's user avatar
  • 21
-3 votes
2 answers
171 views

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?
Justintimeforfun's user avatar
0 votes
0 answers
72 views

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&...
Caymon Sawaged's user avatar
10 votes
5 answers
6k views

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?
thebiggay's user avatar
  • 109
3 votes
1 answer
155 views

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.
Mridul's user avatar
  • 1,232
4 votes
0 answers
394 views

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 (...
Darkcat Studios's user avatar
2 votes
1 answer
316 views

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?
Aditya Sharma's user avatar
1 vote
1 answer
362 views

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
Mohamed aly's user avatar
3 votes
1 answer
725 views

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
Sachin Chaudhary's user avatar

1
2 3 4 5
19