Questions tagged [turbofan]

A type of jet engine which uses two different airflow streams (one passing through the core and another blown past it by a fan) for obtaining thrust.

Filter by
Sorted by
Tagged with
1
vote
1answer
86 views

Is axial bearing in turbo fan,turbo jet engines neutraly loaded?

Is axial bearing in turbo fan,turbo jet engines neutraly loaded,if yes then turbine/fan and compresor produce eqaul and opposite force? If yes ,where then thrust come from,at internal walls,must be ...
2
votes
1answer
177 views

Do aircraft engines come with electric generators?

For turbojet/fan/prop engines, do they come with an electric generator when delivered to aircraft manufacturers, or it is something that the aircraft manufacturer has to find or make themselves? I am ...
6
votes
2answers
252 views

Do turbine engines contain engine oil and fire-extinguishing fluid?

When aircraft turbine engine companies sell their engines to aircraft manufacturers, does the product contain the tank and pipe for engine oil and fire extinguishing fluid in the same package? Or is ...
5
votes
2answers
1k views

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.
2
votes
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/...
4
votes
1answer
153 views

Will N1 shaft turn at the same time as N2 shaft?

For Turbo Fan Engine CFM56-7, was wondering how come the Fan blades (N1 shaft) turns when I turn the N2 Shaft manually. I thought N1 shaft is connected to the fan and booster rotor and LPT rotor and ...
3
votes
1answer
159 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
votes
1answer
190 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 ...
2
votes
0answers
279 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?
2
votes
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 ...
2
votes
2answers
302 views

Why do large civil airliners use cold rather than hot thrust reversers?

Is it because cold thrust reversers are best for turbofans and most civil airliners have turbofan engines?
0
votes
1answer
90 views

Turbo-electric engine vs high by-pass-ratio Turbo fan, which config. would seem more efficient? (Liquid Hydrogen Fuel)

Would be a turbo-electric config using 2 turbofans as generators for a 150 pax. aircraft more efficient than a very high bypass rationed Turbofan that burns hydrogen? If not, then why are all ...
0
votes
1answer
56 views

Does aircraft nacelle length/shape/geometry affect the contrail formation?

This is coming from Question 1 and further down Question 2. I think the nacelle and exhaust cone do affect the contrail formation in some way, what is the relationship between them? Do the famous 787 ...
2
votes
1answer
436 views

What are variable stator vanes?

Most turbofans nowadays use "variable stator vanes"; what are these, what is their purpose, and how does it affect a gas turbine's performance?
0
votes
0answers
38 views

Bleed air examples and percentages [duplicate]

I'm doing an assignment in GSP where I've got to examine bleed air and it's effect on thrust and fuel consumption. I've got to simulate 1-10% bleed air and then answer whether the drop in performance ...
1
vote
1answer
136 views

What is the relation between N1 and Wing anti-ice

When wing anti-ice is selected, the N1 or EPR limit is automatically reduced, and the idle N1 or EPR is automatically increased. What does this statement mean ???
-1
votes
3answers
186 views

What amount of electricity could we get from the Seebeck effect on a kerosene turbofan?

Edit: I rewrote my post. To downvoters, can you comment on your reasons? As a kind reminder: Downvote questions that don't show any research effort or don't contain enough information to be clear and ...
2
votes
1answer
145 views

Efficiency of the Kuznetsov NK-88 or NK-89 engine burning hydrogen

It's tough to find data about turbofan efficiency running on hydrogen. The Tupolev Tu-155 has been used as a test bed for exotic fuels right before the fall of the soviet union, without much follow-up....
2
votes
0answers
176 views

Why Not Just Replace All the Fan Blades?

It looks like operators will have to remove all their P&W powered B777s from service until they have checked the engines. Since the problem seems to be fatigue (which is a function of time) in a ...
4
votes
1answer
991 views

Why are jet engine fan blades painted?

I came across this extremely interesting article with details on a 2018 United Airlines Boeing 777 engine failure, which is also related to the more widely-publicized failure a few days ago: http://...
0
votes
0answers
38 views

Comparison of specific thrust vs. speed, for EDFs and propellers

I stumbled upon this graph showing the decrease in specific thrust (Thrust by Power) in relation to velocity, for a Schuebeler EDF: https://www.researchgate.net/figure/Specific-thrust-T-P-vs-airspeed-...
6
votes
1answer
188 views

What are the engine-out implications of giant turbofans?

It seems that turbofans for civil airliners are improving fuel efficiency by building larger and larger fans that spin slower. For example, the RR Trent 800 introduced in 1993 had a diameter of 2.8m, ...
2
votes
0answers
77 views

What is the fan pressure ratio in a turbofan?

What is it and how does it affect efficiency and thrust?
1
vote
0answers
56 views

Texts on aero-engine structures

I have been scouring the web for resources on aero-engine structures and structural design (preferably civil turbofans) but unfortunately it seems like they are hard to come by. I would like dedicated ...
2
votes
0answers
94 views

What's this outlet of IAE V2500 for? [duplicate]

Anybody knows what is this outlet for and why it is designed in such way? Edit: On MD-90 didn't see such thingy
4
votes
2answers
265 views

The latest turbofan aircraft feature an exposed exhaust cone, does it come with some benefits? [duplicate]

Aircraft like Airbus A320neo/A330neo/A350 series have a visible exhaust cone, which is not visible in the older versions of Boeing 747, Airbus A330/A321/A319 etc. Why is this design preferred over the ...
10
votes
1answer
415 views

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

I'm not sure that they are painted but it looks like they are. What are they for? More images:
1
vote
2answers
255 views

What kind of test is going on in this image?

Some times we see images of jet engines on the net that have strange colors. For example take a look at the bellow image. What the operator is doing? Why the color of blades are white with red on its ...
2
votes
0answers
71 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?
0
votes
1answer
249 views

Would large, low aspect ratio fan/propeller blades be more efficient? Why not?

With reference to this answer We read in the above that accelerating a larger mass of air by a smaller amount is (theoretically) more efficient. This is an advantage of a larger propeller than is ...
0
votes
1answer
127 views

What is the purpose of air that passes through the engine core in a turbofan engine? Is it mainly to spin the fan rotor? [duplicate]

The majority of the air going through the bypass is producing most of the thrust and providing the air that cools the engine. Does is also provide the pressurization and cooling/heating for the cabins?...
1
vote
1answer
110 views

Why are high-bypass turbofans faster than turboprops?

The turboprop, and especially the high-blade-count propfan, differs from the high-bypass turbofan principally in throwing away the draggy outer ducting. This makes it easier to obtain a greater ...
0
votes
0answers
32 views

At what range does the turbofan start to become more economical than a turboprop? [duplicate]

By more economical I only mean 'burns less fuel'. I'm under the impression that at optimal cruise speed and altitude a turbofan will burn less fuel per mile per passenger than a turboprop, but I might ...
7
votes
1answer
299 views

What causes the horn-like noise during the start-up of some jet engines?

Here's the specific sound I'm talking about (it starts specifically 56 seconds into the video, as well as at 2:02 for the second engine): I've only really heard that ...
1
vote
2answers
320 views

Why would sea level static thrust have a takeoff and a maximum continuous value?

In the type certificate data sheet for a jet engine, there is this table static thrust is the thrust generated by the engine when the plane is at rest with respect to the Earth and the surrounding ...
2
votes
2answers
92 views

What do these temperature data listed in the EASA Type Certificate Data Sheet mean?

Could you tell me what is the Maximum Permissible Indicated Turbine Temperature (ITT) and the ambient limit temperature for sea level static thrust?
4
votes
3answers
341 views

Do turbofan nacelles generate lift?

Since they are essentially an annular wing, how much do they contribute if at all to an aircraft's total lift? Would the effect of this lift be noticeable enough to help cancel out the drag they ...
3
votes
1answer
496 views

Why do some Turbofan engines have multi-stage fans?

I was wondering why some turbofan engine have multi-stage fans. e.g. F-119 engine: F100 Saturn AL-31
28
votes
2answers
6k views

Are large jet turbofans so easy to spin?

In this question, in the accepted answer, there is a comment by alephzero that says one can actually rotate a large turbofan's blades with one finger! Is that true, ...
0
votes
1answer
129 views

What gas turbines have the following configuration?

Is there any jet engines--with published data on the dimension of the turbines and compressors--that are of the configuration of 2 Low Pressure compressor, 8 High Pressure compressor, 2 High Pressure ...
2
votes
1answer
228 views

What is the most recent turbofan engine that used steel for its bypass fan blades?

I haven't been able to locate any engines that use steel for the bypass fan. All sources suggest Ti and composites are used for blade construction. Apart from the weight steel could partially make up ...
0
votes
1answer
50 views

Why is tangential velocity a loss of kinetic energy in a turbine section?

While researching turbine engines I came across a statement The mass of airflow naturally does not change in the transfer of energy to the rotor system, but the velocity of mass flow being slowed ...
6
votes
3answers
408 views

Why don't turbofan engines have shrouds affixed to the fan blades?

For a turbofan to be efficient the gap between the blades and the shroud has to be extremely small. Why don't we just attach the shroud directly to the blades and let it spin as one? Would that ...
7
votes
7answers
3k views

Why don't bypass ducts in jet engines narrow down the flow to accelerate it?

Since decreasing the flow area increases flow velocity, why don't turbofan bypass ducts narrow down to produce more thrust?
1
vote
1answer
182 views

What is the temperature range of engine mounts connected to the pylon?

I want to know what is the temperature of the engine mounts in modern turbofan engines for example, Rolls Royce Trent 900. Also, what are the temperature considerations you need to make while ...
2
votes
0answers
131 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, ...
3
votes
1answer
303 views

Why does turbofan exhaust appear to reverse direction?

Yesterday I was at the airport planespotting. I observed the exhaust of a couple of turbofan engines, and found it curious how the fluid seemed to behave as it was leaving the engine and gaining ...
2
votes
2answers
326 views

Is it true that high-bypass engines are inherently inefficient at higher speeds?

Power consumption=Kinetic energy=$1/2mv^2$. Thrust=momentum change=$mv$. I keep being told that aircraft engines are most efficient when their exhaust velocity closely matches the freestream. The ...
2
votes
1answer
237 views

Why can’t the newest high-bypass turbofans run at their EPR, temperature, and RPM limits simultaneously at sea level?

The General Electric GE9X turbofan (used on the 777X), unlike the vast majority of turbofans before it, did not undergo the traditional triple-redline test (where the engine is run for a prolonged ...
2
votes
1answer
383 views

Does jet engine exhaust velocity relative to itself remain constant despite speed changes?

Maybe this is a stupid question. I seem to have been told, the velocity of the exhaust leaving an airbreathing jet engine relative to the engine, is constant despite changes in airspeed. However, to ...

1
2 3 4 5