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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.

19
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1answer
6k views

What are these “pimples” on the jet engine for?

When looking into the General Electric CJ 805-23B jet engine, I have discovered that all forward section of the compressor is covered by a number of near identically looking "pimples". What are these ...
2
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0answers
34 views

How are compressor maps drawn?

I've always thought they are empirically derived: once you have your axial compressor phisically in a bench, you set both a rotational speed and a mass flow throught the turbomachine then you measure ...
0
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1answer
32 views

How to calculate power required to drive an isolated fan of a TurboFan engine?

If I isolate the fan from a TurboFan jet engine (specifically GE90) and power it electrically with a motor, how much power is required for the electrical source to drive the fan to give the same ...
0
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5answers
198 views

I wonder if it's possible to make a “compressed air” turbine engine [closed]

I wonder if it's possible to make an efficient turbine engine that uses only hot compressed air to move but only that, meaning there is no ignition involved. To put it simple can we use compressors ...
2
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1answer
189 views

What exactly is an “engine surge” in a jet engine, and what causes it?

Surge suggests that something speeds up, yet I read elsewhere that in fact in jet engines, an engine surge is actually a compressor stall. Whether that is correct or not, what exactly is doing the ...
-3
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3answers
107 views

Is it possible to calculate possible fuel savings of known turbofan engines if operational heat could be increased [closed]

Starlite is liquid paint like substance invented in 70s and perfected in the 80s by the late British inventor Maurice Ward (1933-2011). It is said to be able to withstand heat from 78 nuclear ...
0
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0answers
32 views

Adjusting nozzle shape for reduced flow rate

Suppose i have a ramjet engine, but in the combustion area i make an opening along the whole cirumference (a slit) feeding a channel, in which the pressure is the same as in the combustion chamber. ...
1
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1answer
142 views

Does preheating fuel before it reaches the turbine result in a performance improvement?

Preheating fuel before it reaches the combustion stage was first proposed several decades ago as a way to improve mixture, fuel economy, and to reduce emissions in car engines. One example of this ...
2
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7answers
289 views

How does maximum speed vary with altitude?

Question: How does a commercial jetliner's maximum speed vary with altitude ? My understanding is that drag decreases with altitude, therefore maxspeed increases with altitude. This is also what Cpt....
0
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1answer
66 views

Is jet fuel typically injected before or after the flame holder in an afterburner?

I don't have the best grasp on the intricacies of afterburners but I'd assume that if the engine has a flame holder then fuel would be injected before it in order to allow it to heat up to ...
5
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2answers
257 views

How do I optimize a turbofan engine to fly lower and slower instead of higher and faster?

I was reading something about someone who was doing this and I'm intrigued, but I have no idea what you actually do to optimize the engine to be better at lower altitudes and lower speeds?
17
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4answers
3k views

Why do uncontained engine failures still occur?

One of the absolute requirements of an aircraft turbine engine (usually some sort of turbofan or turboprop) installation is that, in the event of a destructive failure of the engine, the engine ...
0
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1answer
170 views

What is significance of N1 and N2 in Jet engine? [duplicate]

Why N1 Low pressure compressor RPM and N2 High Pressure compressor RPM are monitored in jet engines ? Why specifically compressor RPM rather than turbine RPM ? What do N1 and N2 signify in terms of ...
2
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1answer
242 views

What position was this photo of a jet engine taken from?

From that aviation photographer, I saw that beauty: Having in mind the jet engine I would see, let's say as a normal passenger, I am not really able to understand from where I am looking at that ...
3
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1answer
70 views

What is the difference between active tip clearance control system and passive tip clearance control system in turbine?

What are the main differences between turbine active tip clearance control system and passive tip clearance control system?
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1answer
124 views

Turbofan design parameters [closed]

I am writing a model for LM Prepar3D to simulate the flight model of a commercial airliner. The specification I am following requires some parameters from the engine (CFM56). ...
0
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1answer
99 views

Where could I find the FOD examples of C17? [closed]

I want to find some FOD examples of huge planes in reason of ground vortex,where should I go to search?
1
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1answer
109 views

Bright exhaust in afterburner vs no visible (bright) exhaust when not in afterburner?

When a jet engine has its afterburner engaged, a bunch of fuel is dumped into the back of the engine for additional thrust. This burning fuel causes the exhaust and inside the engine to glow brightly,...
3
votes
1answer
270 views

Why aren't there any jets with horizontal-stabilizer-mounted engines?

Looking at the spectrum of where jet aircraft put their engines, there are examples of almost every place that could conceivably used to carry a jet engine: slung under the wings buried inside the ...
0
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0answers
57 views

Does the stator blade angle changes? Why?

I have read that when jets are on the ground their compression ratio changes. With this change the stator compressor's blade angle changes. Is this true?
0
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0answers
100 views

What happened with the Boeing PETA Pulse Jet Engines

The boeing engines created a buzz when they were announced back in 2011, and were said to be proprietary technology. It created a buzz about easing VTOL concepts and more, but where does the project ...
0
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2answers
99 views

How does fuel flow and altitude affect the compression ratio of jets?

Does the compression ratio of jet engines change with altitude and/or with the rate of fuel flow?
0
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0answers
55 views

what is the impingement location of Streamwise vortices?

When I was reading an article about scalloped and lobed mixers in turbofan engines nozzle, I faced with this sentence that was comparing lobed and scalloped cases: "impingement location for the ...
0
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1answer
106 views

Wind correction on downwind during circling

A timing must be started when flying abeam the threshold on a circling approach. The FCTM of the B777/787 mentions 35 seconds and the SOPs of the Embraer 190 30 seconds. Do they need to be corrected ...
-1
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1answer
161 views

What are the Boeing 777 thrust calculations? [closed]

Can someone show typical calculations for a Boeing 777 jet engine for the following criteria: Take off thrust of the engine at 170 mph take off speed and 45 degrees F Cruising thrust required at 500 ...
0
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0answers
70 views

What‘s the diameter of the engines of the Airbus E-Fan?

does somebody know the diameter of the E-Fan‘s engines ? To me the look like around 80cm or what do you think ? Also, with more and wider blades and 60 kW motors instead of 30 couldn‘t they get much ...
1
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1answer
130 views

Hydro-pneumatic fuel controls and hydro-mechanical fuel controls

What are the advantages and disadvantages of the hydro-pneumatic controls against the hydro-mechanical controls?
2
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2answers
85 views

How can I determine specific heats of gases for turbojet engine calculations?

I'm in a combustion lab and we are performing experiments on a turbojet engine. However, I am having some trouble calculating the exit velocity and compressor/turbine powers of the engine. Consider ...
0
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0answers
92 views

What are the air mass flow rate and fan pressure ratio of the Trent XWB?

I have some basic questions regarding the Trent XWB: What's the air mass flow rate (or its range) of the Trent XWB engine? Is all of the air mass flow of the engine produced only by the 118" diameter ...
2
votes
1answer
327 views

How much fuel does an airliner consume during passenger boarding?

As I understand, sometimes APU is running during the passenger boarding. How much fuel do the APU consume during this process? Of course, it must depend on the total boarding time, so I think it ...
3
votes
2answers
186 views

Could compressor stalls be caused by air in supercritical conditions?

It is likely that in compressors of jet engines appear conditions that cause the intaken air to become supercritical, cf Is the air in a jet engine supercritical? . Is it possible that ...
5
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2answers
278 views

Is the air in a jet engine supercritical?

Nitrogen has a critical point of 126.2 K and 3.4 MPa (34 bar). Air contains 75 % of nitrogen For example, nitrogen has a critical point of 126.2 K (−147 °C) and 3.4 MPa (34 bar). source : https://...
1
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1answer
170 views

How much thrust could a 400 mm EDF produce?

there's a 195mm EDF from Schübeler that produces 25 kg of thrust at a peak power consumption of 15 kW: https://www.schuebeler-jets.de/de/produkte/hst Now, my question is: How much thrust could you ...
0
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1answer
176 views

How do you maximize an electric engines thrust?

I‘ve been recently looking for answers to this question on the internet but the jungle of propellers, fans and electric motors didn‘t quite get me an anwer. How would I have to design an electric ...
2
votes
1answer
278 views

What is the Specific Fuel Consumption of CFM56-7B24/26/27 engines?

I think the title completely says what I need. I use FSX (Flight Simulator X) to simulate flights and while flying the B738 I saw that it consumes much more fuel than the estimated amount, which is ...
-1
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1answer
92 views

How is pressure kept nearly constant in jet engine burner? [duplicate]

How do engineers make sure the pressure doesn't rise, but velocity does. I have no idea how that can work, please help!
32
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7answers
9k views

Have there been any incidents caused by an inability to shut down an engine?

I read many items on the avherald.com site where it says "engine shut down during flight" or words to similar effect. I'm wondering if there are any instances where an engine could not be shut down ...
1
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0answers
93 views

How does a partially covered air intake affect the thrust of a propeller ?

does a partially covered air intake of a ducted propeller significantly affect its thrust? If so, will it be like 10 or rather 90 percent less thrust ? Thanks for your answers! Simon
16
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3answers
3k views

How much water is produced in jet exhaust?

If a jet has typical combustion efficiency, what equivilent amount of liquid water will be created per gallon of jet or kerosene fuel. An acceptable answer can be a ratio in weight or volume to the ...
0
votes
1answer
146 views

Could the reversers of a PW4000 on a 777 be deployed in-flight? [duplicate]

Could the thrust reversers accidentally be deployed during a flight? Here, I’m referring to the PW4000 series on a B777, where the engine is similar to the type involved in the crash of Lauda Air ...
0
votes
1answer
381 views

What is the cause of cracking and corrosion in Trent 1000 engines?

According to this description and this one of some Trent 1000 engine problems, there appears to be a problem with cracking/corrosion of the fan blades, but does anyone have any insight as to why this ...
1
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1answer
100 views

Could a kerosene fueled jet engine run on methanol without significant modifications? [duplicate]

Could a kerosene fueled jet engine run on methanol without sacrificing performance other than specific impulse? Would it require changes to the fuel injection/turbopump system? Would the combustor ...
0
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0answers
60 views

How does a mixer reduce noise in a turbofan engine?

I want to know how does a mixer reduce noise in a turbofan engine? How does its shape influence the flow and the acoustics of the output air generally?
1
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0answers
67 views

Do plug nozzles improve efficiency on lower throttle settings?

Plug nozzles are used to adjust for the overexpansion/underexpansion of the exhaust with altitude. Do they also adjust for overexpansion/underexpansion of the exhaust caused by lowered mass flow ...
7
votes
2answers
261 views

What exactly does the MB-326's 'relight' button do?

The following picture shows the engine throttle of an Aermacchi MB-326, which is powered by the Rolls-Royce Viper turbojet: (source - all photos © Drive&Fly Model Club) I wonder what exactly the ...
1
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1answer
313 views

What is the relationship between EGT, Fuel Flow, N1, N2 and Air Temperature?

I initially wanted some sample data for EGT, Fuel Flow, N1 and N2 to build a prognosis system that predicts engine failure (ECTM). I searched for some sample data online but got to know that there's ...
1
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0answers
45 views

Single Engine operation on Twin Engine aircraft [duplicate]

I recently came across ETOPS and I wanted to know: How does a twin-engined aircraft balance out the lack of thrust on one side in the event that one of the engines is non operational? Any ...
-1
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1answer
73 views

How does ice affect the combustion systems of jet and piston aircraft engines? [closed]

What are the effects of ice on a jet and piston aircraft engine? I've tried Google but I'm not satisfied with the results.
0
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2answers
683 views

Does Rolls Royce produce any engine that matches the capabilities of the GE9x?

Does Rolls Royce produce any engine that matches the capabilities of the GE9x? If not, does Rolls Royce have any public plans for such an engine in the future?
13
votes
1answer
2k views

What is this aircraft that has both piston and jet engines?

A friend sent me this picture of a trimotor aircraft with what looks like two radial engines and a jet in the middle. He didn't know what is was and neither do I. Anyone recognize it?