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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175 views

What are these painted lines on the fan blades of Rolls Royce Pearl 15?

I'm not sure that they are painted lines but it looks they are. What are they for? More images:
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What different intake designs are there, and what are their pros and cons?

I noticed that over the years (on fighter jets specifically) there have been many different methods of directing air into the engines. Primarily, the nose-intake, side intake, and underbody intakes ...
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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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Why is the F-104 Starfighter’s afterburner thrust not greatly impacted by altitude?

Here is a page from the F-104 flight manual. It shows the flight envelope for the F-104 Starfighter with the powerful J79-GE-19 turbojet engine: I have a question regarding the shape of the ...
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Acoustic analysis from an aircraft engine?

I have found it surprisingly easy to find information on jet engines; however, I've been unable to find acoustic information so I can make a noise spectrum model. I'm looking for oscillations from ...
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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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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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72 views

What is the speed of gas in the core of a jet engine?

Coming from a slightly related question, I want to know what is the speed of the gas in the core of a jet engine, after combustion but before the first turbine stage. I'll just pick a random example: ...
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What is the fan pressure ratio in a turbofan?

What is it and how does it affect efficiency and thrust?
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Why would changes in jet-engine power settings not result in changes in engine loudness?

My casual AAR reading has dredged up another counterintuitive detail of aircraft behaviour, this time regarding the relationship between engine power and engine loudness: 1.16.7.3 Sound Similar to ...
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70 views

Why does the LEAP 1A HPT run at such a high RPM?

I've watched the N2 on the LEAP sit at 100% at cruise and fluctuate as high as 101%. Why does the HPT run at such a high RPM?
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Which dust size causes most damage to turbine engines?

I'm conducting some research on my bachelor's thesis on predictive maintenance and I have so far not been able to find a solution to the following question: Which size of dust is more damaging to the ...
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128 views

How hot is the outer casing of a turbofan engine?

I am able to find temperatures inside different components of turbofan engines, but I can't seem to find what would be the temperature of the external casing/shell of the engine. For example, ...
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129 views

What advantage does Kawasaki C-2 have with a twin-engine configuration as compared to its competitors like An-70 or A-400?

While reading about various military transports, I came across the specs of Kawasaki C-2 and a few questions popped up. So please bear with me here if I list them all together as points, I hope ...
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131 views

What is a compressor cascade?

Is a compressor cascade just the representation of the blade ring of an actual turbomachine? What is the difference between linear cascade and annular cascade? A diagram or a reference would be great.
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Does the angular momentum of a jet engine affect aircraft performance?

I am interested, do jet engines have angular momentum? And how does such momentum affect airplane stability?
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301 views

Can the assumed temperature be lower than the flat rated temperature?

I was playing with reduced takeoff thrust in a Boeing 737-800 simulator yesterday and was surprised that I could enter assumed temperatures below the flat rated temperature of the engines. The ...
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51 views

Is there a way to determine maximum rpm for axial compressor due to material limitations?

I'm looking for RPM to Stress relation to determine maximum rotational speed that compressor/turbine blades can have without undergoing deformation due to centrifugal tensile stress. I've come come ...
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128 views

Do rotating deflagration engines exist?

Pulsejets (which could have been called pulse deflagration engines) rely on pulsed deflagration to generate energy and thrust. Their pulsed mode makes them hideously loud and rather inefficient, but ...
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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 ...
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What could cause an engine shutdown on a Q400 with CDS codes 732, 907, 915 and 938?

A Bombardier Q400 displays error code 938 on the Central Diagnostics System(CDS), which is attributed to turbomachinery chip detector. An examination shows debris in the detector hitch which is ...
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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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Why CFM International has changed the profile of the fan struts used at their CFM 56 turbofan?

See images below Image of a early version of a CFM56 turbofan showing the fan struts [![Image of a CFM56 7B26 showing the fan struts][3]][3] image description here]5]5ttps://i.stack.imgur.com/...
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128 views

How do the contrarotating turbines work in the F-119-PW-100?

I was reading about the F22 Raptor and found out that its powerplants use contrarotating turbines. How does this work Also, if the spools and their connected compressors are rotating in opposite ...
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53 views

Effect on pressure and/or volume of a real vs. ideal compressor

I'm looking at the Brayton cycle and trying to understand what happens when we move from the ideal cycle (isentropic compression/expansion) to the real world where we have adiabatic compression/...
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187 views

Was the speed trim system on the B737 Classic modified to counter increased thrust?

How much additional thrust did the 737 classic generate compared to the original 737? Was the speed trim system added to counter the additional thrust?
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Why at increasing BPR the efflux area should be enlarged (at high BPR)?

I am working on a university project. I have to comment on this chart (that represents efflux area variation with the variation of the BPR). Every other engine data are kept unchanged (turbine entry ...
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230 views

Why use turbofan engines for high altitude flight?

I noticed that a lot of high altitude aircraft have turbofans for engines. So I researched and figured out that turboprop engines are more efficient. But most high altitude aircraft like the Global ...
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128 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
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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 ...
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Are there any performance details available for the D8 Double Bubble engines?

For the D8 Double Bubble, what are the thrust requirements for the engines? Has it been stated what the estimated max thrust will be for each engine? Source: sputniknews.com
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227 views

What is the order of Reynolds number inside the Compressor at cruise conditions?

I am doing a CFD study on a probe that will be installed inside a compressor of a civil aircraft for my final year project. I need to know the Reynolds number inside a compressor at cruise conditions. ...
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420 views

What are the specifications for the CFE738-1-1B?

I'm designing an aircraft for fun, and I've selected a CFE738-1-1B as the engine. It's never going to fly outside of X Plane, but it's still fun, so I'd like to make the X Plane version as realistic ...
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306 views

What is the fuel/air ratio of the CFM56-5A1 engine (in the A320 model)?

I could find the fan-bypass ratio, which was 6:1 (on some models 5:1) but I was unable to find the fuel to air ratio used in this engine. For reference, it is a high-bypass turbofan engine.
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Why do compressors work from rear to the front?

Frequently in many compressor aerodynamics books, this is mentioned as something obvious. I believe it is the reason why on actual compressor testing the way you move up and down its characteristic is ...
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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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116 views

Why do thrust vectoring nozzles delay?

I saw a video demonstrating the SU-30's thrust vectoring nozzles and noticed that the horizontal stabilizers begin moving up/down before the nozzles do. It seems that the F-22 also has this delay. ...
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Is excess power always increasing with a decreasing altitude at iso-mach?

For an aircraft with a jet engine, let's say the power margin at M1.5 at an altitude Z1 is x. Is the power margin at a lower altitude Z1-H at M1.5 always greater than x ? From my point of view, there ...
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Are variable area exhaust nozzles or variable area throats more impactful?

I was reading this NACA research paper where, while discussing an adjustable plug-type nozzle, they state: Although this nozzle did not have independently variable area throat and exit areas, as ...
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What is the diameter of each stage of the PW800 engine compressor and turbine?

I am an Aerospace Engineering student working to analyze P&WC's PW800 engine family--specifically, the PW814GA, for a project and we need to know some hard-to-find data. Does anyone knows where I ...
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What is the engine shell temperature?

What are the highest temperature locations in the outer shell on an aircraft engine? Particularly, modern turbofans like the Trent 900 for example. I'm interested in the temperature constraints of ...
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What are the differences between turbojet and turbofan (low and high by-pass ratio) in the graph of thrust relative to speed?

What are the curves of thrust relative to velocity of the turbojet, low-bypass turbofan and high-bypass turbofan engines from static thrust to Mach 4 generally. Approximation is okay as long it has ...
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Does the safe taxi distance vary behind jet types for light aircraft?

It would seem a light aircraft taxiing behind a business jet could be closer than a B747. Perhaps there is a law (country or international) regulating power setting of a jet taxiing. One authors ...
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At what operating temperatures would the Trent 900 need to operate, to equate to the efficiency of current geared turbofans?

What is the minimum optimum operating temperature (in degrees Celsius) that would be required for the Trent 900 to operate at, for it to attain the level of fuel efficiency of current geared turbo ...