Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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 the fan) for obtaining thrust.

2
votes
1answer
52 views

Does the P&W F100 turbofan engine of the F-16 really produce this much power?

I've been trying to calculate the power a P&W F100 engine on a F-16 is producing using some of the available data on thrust and velocity and I ended up with a number that I want to confirm. Here's ...
7
votes
2answers
961 views

Gear reduction on large turbofans

Do engines like the GE90 and Trent 1000 use transmissions (planetary gears?) for RPM reduction on the fans, or are they welded directly to the same shaft as the low pressure turbine?
6
votes
2answers
419 views

Why are the engines on the MAX and neo prone to bowing?

The engines of the 737 MAX$^1$ and Airbus A320neo family$^2$ are [more] prone to bowing (shafts deforming if no debow is applied during start – as I understand it, this happens in a turnaround while ...
1
vote
1answer
49 views

Proportionally, what is more affected by a hot and high takeoff - a electrically driven propeller or a turbofan?

My assumption would be the electrically driven propeller would be less affected compared to turbofans at high altitudes and take off as although the air would be less dense at these ambient conditions,...
-2
votes
2answers
146 views

Why Engine Exhaust Nozzle can not be totally buried in aircraft fuselage? [closed]

Why The CD nozzles of the fighter aircraft are always outside the fuselage, Why the whole engine is not buried in the fuselage?? If engine shroud also can be made variable area and varies with CD ...
4
votes
2answers
212 views

Why was the DC-8-70 successful, but not the 707-700?

The first high-bypass turbofan small enough to use on a narrowbody jetliner was the GE/SNECMA CFM56, which entered service in the late 1970s as an upgrade engine for the KC-135 tanker; Boeing almost ...
2
votes
2answers
148 views

Turboprop vs turbofan (in regional aircraft)

I'm trying to figure out WHY turboprops are more efficient at lower altitudes and airspeed, while turbofans are better at faster speeds and higher altitude. Simplistically, my explanation is the ...
4
votes
1answer
63 views

Are low pressure (LP) compressors and booster compressors the same thing?

Based on the above picture, are "LP compressor" and "Booster compressor" different names for the same thing or are they actually different things?
2
votes
1answer
104 views

Turbofan engine 2 spool - Turbine drives the compressor or Starter drives the compressor [duplicate]

I have read somewhere regarding turbofan engine 2 spool that says "LP or HP turbine will drive the LP or HP compressor" "During engine starting, the starter will drive the HP compressor via the ...
0
votes
2answers
214 views

Did Boeing or Lockheed ever seriously consider releasing a widebody airliner powered by low-bypass engines?

During the 1960s race to build the first widebody jetliner, each of the three major engine manufacturers was racing to put out a high-bypass engine for one of those jumbo jets: Boeing went with Pratt ...
3
votes
2answers
206 views

Do any propellers/propfans use stator vanes? Why is this not a commonplace feature?

I understand that axial-flow turbine engines generally include stator vanes behind every(?) compressor and turbine stage. This makes quite intuitively sense, because without them the rotating blades ...
3
votes
3answers
362 views

Can a turbofan run without the fan to provide power without thrust?

Is it possible for a turbofan jet - like on a 747 - to run without the fan, if for example you just want the thrust from the internal jet to use to heat up water, not to use as thrust?
3
votes
3answers
115 views

Would there be a purpose for a set of compressors in an electric turbo fan?

This is actually a two part question. Would there be a purpose to a compressor in an electric turbofan where there is no need for a combustion chamber, and if not, is there then a purpose for a bypass ...
-1
votes
1answer
63 views

How to understand turbo machines?(compressors,fans,pumps,turbines,etc..)

From what I understood, the energy transfer between the blades and the fluid(fluid to blade or blade to fluid) occurs due to the curvature of the blade.Its because of this curvature the stream of the ...
3
votes
3answers
330 views

Why did narrowbody jetliners take so long to switch over to high-bypass engines?

High-bypass turbofans were introduced into the airliner market around 1970, when the first widebody jetliners were released (the 747 was first, followed in rapid succession by the DC-10, L-1011, and ...
9
votes
3answers
2k views

Is the bleed air passengers breathe tapped from the engines before or after it comes in contact with fuel? And why? Isn't this unhealthy?

Passengers are often surprised to hear that the air they breathe comes from inside the engines. This sounds unhealthy. Can you explain, why it is not ? Is bleed air tapped (for cabin pressurization) ...
0
votes
2answers
76 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 ...
26
votes
7answers
3k views

Why do we refer to “power” for turboprop engines and “thrust” for turbojet/fan engines?

In jet engines, I read that thrust is related to the fuel flow rate, whereas in turboprop engines power produced is related to the fuel flow rate. What is the reason and brief math behind this?
-1
votes
1answer
143 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). ...
4
votes
0answers
268 views

What will happen to a modern high bypass engine at 80 000 feet with cruise speed of 0.8 Mach?

While keeping the typical cruise speed of 0.8 Mach, will the engine shut down due to "air starvation" at such high altitude? Is it possible to design a turbofan engine, which is able to provide thrust,...
2
votes
1answer
106 views

Did turbofan engine explosions become more frequent in last years in commercial aviation?

There are many incidents with turbofan engine failures during last years. I can list: 2010-11-04 - Qantas_Flight_32 2015-09-08 - British Airways Flight 2276 2016-05-27 - Korean Air Flight 2708 2016-...
0
votes
0answers
132 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 ...
0
votes
1answer
213 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 ...
1
vote
0answers
101 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
0
votes
3answers
242 views

Does bypass air produce thrust?

How does bypass air exiting the bypass nozzle produce thrust in a turbofan engine? I thought that thrust was produced by air reacting with the fans. So if thrust happens when there is an action-...
3
votes
1answer
211 views

On a ducted propeller, how does duct length affect thrust?

So if we are looking at an aircraft with a ducted propeller (or a high bypass turbofan engine), does it matter how long the duct is? As an extreme example, would having a duct that extends 100 feet ...
0
votes
0answers
34 views

How turbofan engine efficiency increases over altitude or speed? [duplicate]

I am confused a lot about the efficiency and thrust relation with altitude and velocity of an aircraft. If thrust is related to air mass flow and velocity diffrence of bypassed air - exhaust gases ...
2
votes
2answers
306 views

Can a turbojet jet or turbofan powered aircraft land and take off from water?

Can a turbojet jet or turbofan powered aircraft land and take off from water? How much clearence from the water surface would it need for its engines so that it does not suck up water?
3
votes
2answers
182 views

How to compare two SFCs, one in thrust, the other in power (both turbofans)?

I want to compare some recent turbofan engines in terms of fuel efficiency, particularly the PW535A and FJ44-4. I found the SFC for the PW535A to be 0.44 lb/h/lbf. I couldn't find anything on the ...
4
votes
2answers
370 views

Why do compressors constrict flow if this decreases pressure?

An axial compressor (and a ramjet intake, for that matter) is commonly depicted as decreasing the volume of air travelling through as we move closer to the combustion chamber. In axial compressors, ...
2
votes
1answer
242 views

Why are most turbofans tractors, but most propfans pushers?

Turbofans and propfans are, in concept, quite similar: both have a turbojet core, plus one or more additional turbine stages that drive a fan(s) which blows air around the core (this is known as ...
13
votes
3answers
4k views

Why didn't early jetliners use turbofans?

For subsonic operation, high-bypass turbofans seem to have essentially only advantages for efficiency, noise and takeoff thrust, at least until they reach the size where ground clearance or LP/fan ...
7
votes
1answer
371 views

Why does the CF6 have a lower bypass ratio than the TF39?

The General Electric TF39, which powered the original C-5 Galaxy, was the very first high-bypass turbofan brought into mass production, with a previously unheard-of 8:1 bypass ratio. Yet, when it ...
1
vote
0answers
78 views

Is there a standard install direction of the abradable shroud honeycomb on a CF6-80c2 engine?

Is there a standard install direction of the honeycomb cells on the Fan Forward case on the CF6-80C2 abradable shroud section? I have seen engines that the honeycomb cells run point to point front ...
13
votes
1answer
5k views

Which jet engines have the highest thermal efficiency?

Some automakers (Mercedes-Benz, Toyota) have recently been making news about the improved thermal efficiency of their engines, stating that they reached the 50% mark. I was wondering if it was the ...
1
vote
2answers
80 views

What are the main sensor value that cause High pressure compressor fault in turbofan engine?

I have read the paper "Damage Propagation Modeling for Aircraft Engine Run-to-Failure Simulation" (Reference). I am doing analysis to find which sensors to monitor for the faults injected in the ...
-4
votes
1answer
182 views

Would an extra fan make turbofans more efficient in cruise?

A turbo fan engine cannot use all of its available thrust in cruise any longer that it normally does at today's technologies, otherwise it would risk a meltdown of the internal hot engine parts and ...
2
votes
1answer
852 views

Are there any differences between turbofan and turbojet engines besides bypass air?

I think I understand both engine types, but I am just wondering am I right in saying that the only difference between the two types of engines is the bypass air (i.e. a turbofan is just a turbojet ...
1
vote
1answer
150 views

What devices measure EPR & RPM on a turbofan engine?

What devices measure EPR & RPM on a turbofan engine?
1
vote
1answer
245 views

What is the fuel mass flow rate at stationary full power for the CFM56 5C2/3C1 engines?

Does anyone know what is the value of fuel mass flow rate when stationary at full power for CFM56-5C2 or CFM65-3C1 turbofan engines? I am doing a work on engine performance and it seems that only ...
1
vote
1answer
241 views

In what way are the airfoils used for a propeller different from the ones used in turbofan engine?

Airfoils are used in the blades of a propeller as well as the blades of the fan, axial compressor and turbine in a turbofan engine. Thus, the airfoils used in above two applications have different ...
2
votes
1answer
203 views

At what Mach Number do variable cycle engines (VCEs) start showing benefits over turbofans?

Currently, most supersonic engines engines are low bypass turbofans. However turbofans start becoming infeasible as the mach number increases. Variable Cycle Engines, still have noise and weight ...
2
votes
1answer
275 views

Why does a turbofan engine force bypass air into a smaller space?

I asked a question about this same concept recently but this question involves the function of the bypass air. In this YouTube video around 1 minute in the narrator says that the bypass air is pushed ...
4
votes
2answers
718 views

What causes the “growl” of some large turbofans at takeoff thrust?

There are some (all?) large turbofans which emit a distinct "growl" (some people call it a "buzzsaw" sound) at takeoff thrust. What causes it? I've seen it explained (as in this question) as the fan ...
0
votes
0answers
150 views

How can I calculate the fuel weight fraction for a single-engine turbofan GA aircraft?

How would I calculate the fuel weight fraction for different stages of flight for a single turbofan engine general aviation aircraft?
-2
votes
1answer
62 views

At what temperatures would the gearing for geared turbofans be rendered unnecessary? [closed]

If geared turbofans were fitted with material science technologies or other engineering innovations that would allow them to operate at higher temperatures exceeding their current most optimum ...
0
votes
0answers
64 views

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 ...
5
votes
1answer
253 views

Is it possible to power a B-52 bomber with four bypass turbofan engines?

Is it possible to power the B-52 Bomber with 4 bypass turbofan engines instead of the eight in its current configuration? They would have less noise and be a lot more fuel efficient.
0
votes
0answers
67 views

Would it be possible to build an engine twice the size of the Trent 900? [duplicate]

Would it be possible to build an engine twice the size of the Trent 900 in terms of physical size, i.e. doubling the diameter? Let's assume that it's feasible to build an aircraft tall enough to ...
4
votes
2answers
262 views

Would tubofan aircraft benefit from adjustable fan blades?

Would turbofan aircraft benefit from adjustable fan blades as do turboprops? Propeller aircraft adjust their propeller size, i.e. shorter propeller for cruising at maximum design altitudes where the ...