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Results tagged with turbofan
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user 1961
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.
7
votes
Accepted
What methods are used to make a turbofan engine spool up quicker?
Several things come to mind, but they will all reduce efficiency and/or cost money, so they will not be popular with engine users:
For turbofans: Reduce the rotational inertia of the spinning parts …
- 237k
20
votes
In a turbofan what holds the spinning axis?
Struts. Lots of them, and with an aerodynamic shape so they don't cause too much drag. Some of those struts double as stator vanes and reduce the swirl of the internal flow. By doing this they add a l …
- 237k
9
votes
Why do turbofan engines have low pressure compressors?
Early jet engines had only one set of compressor disks which were sitting on the same shaft and spinning at the same speed. More modern designs use two or even three concentric spools, each spinning a …
- 237k
9
votes
Accepted
Could a turbofan have two adjacent fans?
Generally, it is more efficient to have one large than two small devices.
The twin fan solution not only needs a gearbox and driveshafts that a single fan solution does without, it also has more inta …
- 237k
6
votes
Why do turbofan engines not have a contrarotating second fan?
The power needed to drive a large fan is currently beyond of what is technically possible in gearbox engineering. The swirl losses of a single-stage fan can be somewhat recouped by inclining the strut …
- 237k
2
votes
What will happen to a modern high bypass engine at 80 000 feet with cruise speed of 0.8 Mach?
In a conventional turbofan engine the oxygen pressure would be too low at 80,000 ft to make combustion possible. …
- 237k
5
votes
Accepted
Why did narrowbody jetliners take so long to switch over to high-bypass engines?
There was no suitable high-bypass-ratio turbofan engine available.
What were the narrow bodies flying in the 1960s and 70s? …
- 237k
28
votes
Accepted
How does a fan differ from a propeller?
The simple answer that covers the majority of engines is that a fan has a shroud. The possible exception are unducted fans or Open Rotor Engines, which are a hybrid between a turboprop and a fan engin …
- 237k
32
votes
Why do military turbofan engines use a low bypass ratio?
The core of the General Electric F110 (installed in the F-15 and F-16 fighters, among others) became the core of the CFM-56 turbofan which is used in the Boeing 737 or the Airbus A320. …
- 237k
2
votes
Accepted
How much power is drawn by a turbofan to power its own compressor?
To answer this question, it is best to start with the compression work which has to be performed on the air flowing through the engine. If you just want to know how much power is needed to run the fan …
- 237k
7
votes
Why is there a maximum altitude to restart a jet engine?
Like most chemical processes, combustion becomes easier and faster with higher pressure. The combination of speed (which provides ram pressure) and altitude (which provides atmospheric pressure) must …
- 237k
25
votes
Can high-bypass turbofans cruise at high altitude?
Yes in principle, but some modifications are advisable.
What limits the maximum operating altitude of a jet engine (besides the thrust needed to climb up there) is the length of the combustion chambe …
- 237k
5
votes
Accepted
Could the Busemann's biplane concept be used in a turbofan engine?
No.
The Busemann biplane is a clever concept to have all shocks cancel each other, but unfortunately, the same canceling happens to all the lift. Therefore, a Busemann fan would not create any thrust …
- 237k
9
votes
Accepted
Do jet fighters use Turbojet engines, and do cargo/passenger aircraft use Turbofan engines?
No
Turbojets were mainly used in the Fourties and Fifties. As soon as pressure ratios had become high enough to allow adding a fan stage, turbofans replaced them. And the distinction is less between c …
- 237k
2
votes
Why is thrust available constant with speed for turbojet engines, when it varies with speed ...
There are several effects which in combination make constant thrust a good approximation at subsonic speed.
Thrust is created by accelerating a working mass in opposite direction. Net thrust is the d …
- 237k