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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.

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2 answers
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How do tubojets compare to afterburning turbofans in terms of efficiency?

Turbojets used to be more common in the 40's and 50's but once jet engine design matured they pretty much went extinct in favor of the more efficient turbofan. I know one advantage of the turbojets is ...
shrimp's user avatar
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2 votes
1 answer
163 views

Is it a good idea to increase exhaust duct length?

I am a big newbie in aviation but still, I have a question: Let's assume a civil aircraft (Boeing 737 or Airbus 320), flying with those impossible real life hypothesis: the exact SAME turbofan are ...
user12642493's user avatar
9 votes
2 answers
3k views

Why is it inefficient to expel high speed gas?

I'm reading the wikipedia page on turbofans, where it says turbojets are inefficient at low speeds because: energy is wasted as the propelling jet is going much faster rearwards than the aircraft is ...
CaptainCodeman's user avatar
1 vote
1 answer
158 views

Hexagonal Texture on RB211 Turbofan Intake

I was at the science museum in London, and was looking at the Rolls Royce RB 211-22B. This particular engine was, I believe, the sixth one ever produced. The surface texture of the fan inlet looks ...
natanijelvasic's user avatar
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30 views

How does relative thrust contribution of bypass flow depend on thrust settings

The context of this question is a wish to estimate the effictiveness of cold stream thrust reversers at low speed. Given a stationary high bypass two spool turbofan at STP, e.g. the CFM56, how much, ...
Ögmundur Eiriksson's user avatar
1 vote
1 answer
155 views

Exhaust temperature of CFM56 engines range (Nozzle downstream temp)?

EGT is available but not the temp of the exhaust nozzle in the CFM56 series.
Setare's user avatar
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1 answer
172 views

Can you augment turbofan thrust using steam injected into the bypass?

Would using waste heat from the core exhaust to turn water into steam increase takeoff thrust when injected into the bypass before/aft of the fan? If so, which would be better? Could this possibly ...
usernamechecksout's user avatar
1 vote
0 answers
73 views

Engine Performance Data for GE F414-400

I am currently in Capstone for ASE, and for our course we have been tasked with reverse engineering the X-59 QueSST created by NASA and Lockheed Martin. I am the propulsion lead for our team and I ...
Derrick John's user avatar
0 votes
1 answer
118 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
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2 votes
1 answer
185 views

Turbofan engine fan blade leading edge fairing?

A lot of aircrafts feature a leading edge fairing for the wing, at the connection with fuselage, in order to reduce the airflow interference. Aerodynamically speaking, those fan blades in the turbofan ...
Frank's user avatar
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5 votes
1 answer
2k views

What is this probe on the Airbus A330 engine nacelle?

What is the purpose of the little probe seen under the A330neo?
Boeing787's user avatar
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1 vote
1 answer
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What is the EGT probe output tolerance?

What is the 'average' or general tolerance (+/-) for EGT probes output on a 'typical' commercial turbofan engine?
MFCTenor1's user avatar
1 vote
1 answer
284 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
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1 vote
2 answers
301 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
1 vote
1 answer
140 views

Where is the thrust of a turbojet felt? [duplicate]

At a high level, this is simple. Hot gas goes out the back, and Newton's third law says the engine is pushed forwards. But when you look inside the engine, it's less clear which part experiences the ...
John Dallman's user avatar
1 vote
1 answer
1k views

What does fan pressure ratio affect in an engine?

So I'm doing a project for my engineering project and nowhere can I find what the pressure ratio actually affects, in this digital sim I am using, when I adjust the FPR it has zero effect on any ...
Brendan Warner's user avatar
4 votes
7 answers
3k views

How does a fan in a turbofan engine suck air in?

I watched lots of video related to sucking process of a fan in a turbofan engine, but I'm confused at a point. In this link and many videos like this, I found the fan'...
Jawel7's user avatar
  • 244
2 votes
1 answer
394 views

What are the exit temperatures of bypass flow

Consider a typical high bypass turbofan designed for cruise at approximately mach 0.8, with a separate nozzle for the bypass air. Ideally, the bypass air would be compressed adiabatically by the ...
Ögmundur Eiriksson's user avatar
7 votes
5 answers
2k views

How do gas turbine engines and turbofan engines keep constant compressor side rpm?

How do the RPMs stay constant in a gas turbine engine? For example in car with piston engine, when you keep pressing the accelerator the rpms keep picking up, to keep the rpms constant you must let ...
Timothy Scherer's user avatar
11 votes
4 answers
2k views

If the pitch of a bypass fan blade in a turbofan is fixed how does it manage to provide thrust over such a large speed range?

A fixed pitch propeller is only good for aircraft that do around 100kts because the angle of attack on the propeller decreases as the forward airspeed of the aircraft increases, limiting the thrust ...
Ian's user avatar
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6 votes
1 answer
745 views

Why do modern turbofans have swept blades?

(Picture sources: CF6 and GE90) Aircraft have swept wings for two reasons: It reduces the thickness-to-chord ratio of the effective chord, which is ideal for flight at higher Mach numbers. At ...
Aditya Sharma's user avatar
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0 answers
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What airfoil can be used in making a turbofan engine fan blade? [duplicate]

The thing is, I am trying to make turbofan blades in Solidworks for a possible undergraduate thesis. I would like to know if there is any airfoil from the NACA series or anything plausible for this ...
Paul P.'s user avatar
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1 answer
485 views

What airfoil family does turbofan's fan blades use?

The thing is, I am trying to make turbofan blades in Solidworks for a possible undergraduate thesis. I want to know if there is any airfoil from the NACA series or any airfoil families plausible for ...
Paul P.'s user avatar
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6 votes
4 answers
6k views

Can electricity be harvested from magnets in jet engines?

I was reading about bleedless-787 power system but found out it still requires a gearbox. What if you put coils around the "tube" part of the jet and tiny magnets in the end of the fan/...
user3638379's user avatar
4 votes
2 answers
568 views

Could a F-22's exhaust stall a highjacked Boeing 767's turbofan(s) and force it to land?

Would it be possible to use a F-22's exhaust to intentionally stall a hijacked Boeing 767's turbofan engines in order to force it to land instead of shooting it down? The idea being that stalling one ...
Kim deDonado's user avatar
1 vote
1 answer
441 views

Why does the gas turbine recuperator hugely increase efficiency but slightly decrease the peak power?

I understand that the heated intake air will burn more efficiently with the fuel and that's why recuperators increase efficiency. The part I don't understand is that if efficiency is going up, why isn'...
Timothy Scherer's user avatar
9 votes
1 answer
1k views

How can a turbofan's fan generate thrust in cruising flight if air is being slowed down?

High bypass turbofans in airliners generate most of their thrust from their fans, not their "cores". However, at cruise they are actually spilling some air past the intake rather than ...
Kevin Kostlan's user avatar
0 votes
3 answers
347 views

Turbofan ‐ turboprop/shaft hybrid?

If a turbofan engine can create more thrust than a standard turbojet engine, would a turboshaft engine benefit from using a turbofan to power the shaft, in a hybrid kind of set up?
Derk Diggler's user avatar
5 votes
3 answers
4k views

How come a turboprop can't reach speeds as high as a turbofan?

I understand that turbofan powered aircraft can reach much faster speeds than turboprops like the C130 Hercules, and I can't imagine a turbofan turboprop powered 737 would be of any use really, but as ...
TomW008's user avatar
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3 votes
2 answers
376 views

Engine torque due to Turbofan engines and its effect on aircraft attitude [duplicate]

I know that for turbofan engines there will be Gyroscopic effects while pitching, rolling and yawing maneuvre. But if the aircraft is cruising at an altitude or is simply idling on the ground, what ...
itsChibi's user avatar
  • 119
0 votes
0 answers
181 views

Why does adding more blades to a propeller/fan not show a decrease in efficiency?

According to this answer increasing blade solidity increases the blade area by either enlarging chord or increasing blade count both of which reduce efficiency via reducing the lift coefficient and ...
usernamechecksout's user avatar
1 vote
1 answer
261 views

How is bleed air flow related to thrust level?

I read that the bleed flow negatively affects the thrust levels for a turbofan engine. However, I was wondering if vice-versa is true as well? Whenever the thrust levels for a turbofan are lowered at ...
Harjot Singh's user avatar
6 votes
4 answers
1k views

Why is China still heavily reliant on Russian turbofan engines?

According to Paul Schwartz, China is "still heavily reliant" on Russian turbofan engines: Beijing is still heavily reliant on Russian aircraft engines, however, due to the great difficulty ...
Rodrigo de Azevedo's user avatar
7 votes
2 answers
3k views

Why do turboprops not have a thrust value in the specifications? [duplicate]

When looking through aircraft engine specifications, turbofans always provide a thrust value, e.g. in JT8D engine: https://prattwhitney.com/products-and-services/products/commercial-engines/jt8d In ...
Msegade's user avatar
  • 173
7 votes
2 answers
671 views

Is the U2's 74,000 ft the highest a turbofan plane ever has gone?

What is the altitude record for a turbofan? The (usually) turbofan-powered U2 has gone to 74,000 ft (22.6 km) MSL, but did any turbofan plane surpass that, in a zoom climb for instance and with ...
Better not tell's user avatar
4 votes
3 answers
1k views

Why do some jet engines have fewer fan blades than others?

I have found out upon researching jet engine fan blades that they can vary from 16 to 34. Why do they vary, I mean, does decreasing or increasing the number of fan blades have any performance impact? ...
Aviation Enthusiast's user avatar
5 votes
3 answers
4k views

What is a spool in any jet engine, what is its funtion?

I am a student and I'm trying to determine how a spool works in an engine. What effect does it have depending on the number of spools on the performance of the engine? I tried to find it on Google but ...
Karandeep Singh's user avatar
6 votes
3 answers
598 views

Why is thrust (in a high bypass turbofan for e.g.) non-linear with respect to N1?

I've been studying jet engines for a short while now and I think I have a pretty decent understanding of how thrust is generated, but one thing I'm struggling a bit with is how thrust varies across ...
jpsharif's user avatar
  • 119
8 votes
1 answer
1k views

What are these white drops on the exhaust plug of a CFM56-7B engine?

Does anybody know what those white dried-up drops are? I checked out another Boeing 737-800 on the ramp and it also had the same defect so I'm guessing this is a common issue, or is it? This shows up ...
Luis's user avatar
  • 81
4 votes
1 answer
1k views

Thrust varaition of a Turbofan engine with altitude and mach number [duplicate]

my classmates and I are trying to find a mathematical model for a low bypass turbofan engine, we ended up finding a model given by Snorri on "General Aviation Aircraft Design", but the ...
AlejandroArias's user avatar
2 votes
0 answers
232 views

What are these holes on the intake of Progress D-18T which are mounted on AN-225?

I was seeing a Progress D-18T of AN-225 and saw these holes on the intake of them. What are they for?
Roh's user avatar
  • 3,329
1 vote
1 answer
182 views

What is the speed the fan blade would go if it would separate from the shaft with the engine at full throttle?

I'm making a simulation of a blade separating from the shaft to test the case of the engine, but i don't know what speed should i put on the blade to go outwards the case, anyone has any idea how to ...
Lalo Beltrán's user avatar
0 votes
1 answer
132 views

How to find the velocity of the working fluid through the fan in a turbofan engine?

Is there any formula for the velocity of the working fluid (air) through /the fan of a turbofan engine? If not, how can I find the velocity?
ganesh1102's user avatar
4 votes
2 answers
585 views

How much extinguishing agent is needed for an engine fire?

I am quite interested in the firefighting fluid tank choices in turbofan-equipped aircraft. As seen in this picture: Although this is only the APU, but the fire extinguishing agent bottle looks quite ...
Faito Dayo's user avatar
0 votes
1 answer
279 views

Why are there motive flows for the turbine pumps of Williams International FJ44-3A engine?

For my university project, I am designing the fuel supply of an aircraft using a Williams International FJ44-3A engine. Studying the related FAA TCDS, I read "Fuel from the motive flow port on ...
Faito Dayo's user avatar
1 vote
1 answer
315 views

What are the fuel system pressure and temperature requirements of a Williams FJ44 engine?

For my university project, I am designing the fuel supply and control system of an aircraft that use Williams International FJ44-3A engine. However, after scouring through its type certificate ...
Faito Dayo's user avatar
1 vote
1 answer
131 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 ...
user707264's user avatar
  • 1,958
2 votes
1 answer
262 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 ...
Faito Dayo's user avatar
6 votes
2 answers
375 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 ...
Faito Dayo's user avatar
6 votes
2 answers
5k 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.
Anugerah Radifan's user avatar

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