All Questions
22 questions
2
votes
1
answer
185
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 ...
- 29
1
vote
1
answer
225
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.
- 13
7
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 ...
4
votes
3
answers
2k
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? ...
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 ...
- 181
3
votes
1
answer
2k
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
- 3,329
7
votes
3
answers
2k
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 ...
- 2,544
1
vote
1
answer
454
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 ...
- 41
2
votes
0
answers
773
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, ...
- 41
3
votes
2
answers
541
views
How do turbofan internals handle the load from the thrust?
To my understanding, turbofan engines get the majority of their thrust from the fan in front of the engine, up to around 70-80% while the core flow generates around 20-30%.
Forward movement is ...
- 443
40
votes
11
answers
19k
views
Why do new jet engines cost billions to design?
This question might come off as crude because it involves people's salaries, but I do not understand why new designs of large turbofans cost many billions of dollars to design. For example, the Pratt &...
- 17.9k
3
votes
3
answers
499
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 ...
- 31
-1
votes
1
answer
301
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).
...
- 1,501
1
vote
0
answers
163
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
- 351
4
votes
1
answer
974
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 ...
- 28.6k
2
votes
1
answer
484
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 ...
- 121
5
votes
3
answers
3k
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 ...
- 685
5
votes
3
answers
2k
views
How much weight does a thrust reverser add?
How much weight does a thrust reverser add to an engine?
Let's take the CFM Leap 1B as an example, which powers the new version of the Boeing 737. This engine can produce up to 130 kN of thrust for ...
- 17.9k
25
votes
2
answers
16k
views
Where is the generator in a large turbofan of a commercial airliner?
So, where do you put the electrical generator?
If it's gonna be coaxial, the only place is the rear (it will be burnt) or the front (it will get in the way of intake).
If it's gonna be coupled to a ...
- 17.9k
7
votes
5
answers
16k
views
Why do jet engine fan blades have a twisted shape?
I'm thinking: as the blades rotate, the tip moves faster than the hub. So to make the blades efficient, the blades are usually twisted. The angle of attack of the blades at the tip is lower than at ...
- 91
20
votes
2
answers
3k
views
How do turbofan nacelle lengths compare?
For example, compare the JT9D and the PW4000 below (both from Pratt & Whitney, both on a 747):
(Left, Right) The PW4000 has a longer forward nacelle, and a covered exhaust cone.
On the inside—...
user14897
25
votes
3
answers
4k
views
Why are turbofan inlets leaned/angled forward?
(Image Source: Wikipedia)
Seeing that everything is radially symmetric (apart from the nacelle mount, naturally), I wonder why the inlet (the front part of the nacelle) is usually skewed?
- 909