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A type of turbine engine which uses two different airflows (one driven to the core and another to the fan) for obtaining thrust.

0
votes
1answer
65 views

Which one will be louder: a turbofan or a contra-rotating electric propeller engine, if both are of comparable thrust? [on hold]

If we have two engines that produce similar (to identical) thrust, the first being a classical turbofan and the other a contra-rotating unducted electric prop-engine, which will be louder.
25
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
116 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). ...
1
vote
1answer
182 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
104 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
80 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
173 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
91 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
194 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-...
2
votes
1answer
144 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
31 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
263 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
170 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
215 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, ...
1
vote
1answer
165 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 ...
12
votes
3answers
3k 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
248 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
63 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
3k 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
67 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 ...
-3
votes
1answer
160 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
624 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
103 views

What devices measure EPR & RPM on a turbofan engine?

What devices measure EPR & RPM on a turbofan engine?
1
vote
1answer
177 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
158 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
143 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
238 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
480 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
111 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
60 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
56 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 ...
3
votes
1answer
190 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
66 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
197 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 ...
3
votes
1answer
558 views

Is a turboprop or a turbofan more eco-friendly?

If we compare them, which one wins? Why? And, what about CO2 emissions?
4
votes
3answers
639 views

Why does the Trent XWB have intermediate compressor stages?

I realized that the Rolls-Royce Trent XWB on the Airbus A350 has intermediate compressor stages. Why is that? Other engines like the CFM56 or IAE V2500 that power most of the A320-family have low ...
20
votes
2answers
4k views

Why are only some aircraft in this formation creating contrails?

The Republic Day celebrations at New Delhi, India had a series of flypasts by the Indian Air Force. What struck me the most was that in a formation with a C-17 in middle and two Su-30MKI flanking it, ...
-5
votes
1answer
177 views

does the compressor section of a jet engine creates a depression in front of it, due to air be sucked at a great rate [duplicate]

for large Jumbos like the Airbus A380 and the Boeing 747 - 800 at maximum thrust at take off, does the compressor section of a jet engine creates a depression in front of it, due to air be sucked at a ...
3
votes
1answer
169 views

Is it possible to add “planets” to the gearbox of a Trent 1000?

The gearbox of a geared turbofan engine has 4 reducing gear small wheels being spun by a larger wheel or gear, simultaneously spinning the shaft that is attached to the fan. That is 8 points of ...
4
votes
1answer
700 views

Do fan blades use bell shaped lift distribution curves?

Seeing the organic curvature of some newer fans in turbofan engines, I'm curious if they use bell shaped lift distribution curves in their design, or something else all together.
5
votes
1answer
143 views

Could the Busemann's biplane concept be used in a turbofan engine?

Would incorporating the Busemann's biplane concept in the turbofan engine fan blades and engine casing make it more efficient, if fan tip speeds were allowed to move above the speed of sound by ...
5
votes
1answer
564 views

Why does the CF6/CFM56 Turbofan Fan Frame contain 12 circular holes between the primary and secondary flow?

This question is related to the answer I found on this particular thread, about the Frames in a Turbofan. In a turbofan what holds the spinning axis? I went on this thread after some research on ...
2
votes
1answer
361 views

Is there a pressure rise and velocity change across a turbofan fan and stator?

I've been looking at the pressure / velocity / temperature diagrams across jet engines. These have really helped me to understand the different roles that the compressor/turbine stator and rotors play,...
3
votes
2answers
301 views

Why is a contra-rotating High Pressure section more efficient? [duplicate]

In the Rolls Royce Trent 900 marketing material, the use of contra-rotating HP system is described as increasing the efficiency of the engine. Can anyone explain why/how that increases the efficiency?
16
votes
3answers
3k views

Can high-bypass turbofans cruise at high altitude?

They have talked for years about re-engining the B-52 with something more modern than its TF33-P-3/JT3D turbofans, which are fairly low-bypass (1.42:1 for the JT3D). Modern engines are much higher ...
0
votes
3answers
233 views

Does a trent 900 engine have the ability to spin extra or more fans?

Given that the most modern geared turbo fans gear down spinning the fan, which essentially translates to requiring less torque or horse power to spin the fans. If the gearing down is in the magnitute ...
6
votes
3answers
1k views

Would it take 7 to 10 times more energy to lift a turbofan-helicopter?

I want to figure out how much energy it would take to lift a turbofan-helicopter. For reference I started with a rotor helicopter and assumed $T=100\ \mathrm{kN}$ gross weight and $d = 16\ \mathrm m$ ...
1
vote
2answers
555 views

What is the maximum speed of all the stages of a geared bypass tubojet engine?

What is the maximum speed of all the stages of a geared bypass tubojet engine before they start losing efficiency.
1
vote
2answers
303 views

Can a turbofan maintain torque when spinning fast?

I assume turbofan fan rpm could be increased only when: Using most modern jet engines (Airbus A380 and the Boeing B747-800) Using a magnetic gearbox which can handle more torque dor the same weight ...
1
vote
1answer
288 views

What is the drag induced by a high bypass jet engine on an airliner?

What is the drag induced by a turbo bypass jet engine in a typical most modern airliner like the 777, the Jumbo Jet (Boeing 747-8) and the Airbus A380? Given that the jet is travelling faster than ...