Reasons behind jet engines spinner shape

[Ronny]

Like the title said, why do they have different nose shape?
AL-31


F-135 engine

 

[thefrecklepuny]

The US J-79 had a blunt nose.

https://image.invaluable.com/housePhotos/WorldwideAuctioneers/27/671727/H20580-L208078831.jpg

 

[overscan (PaulMM)]

F-135 might be accommodating LO requirements as well as air flow requirements. Early F100s have a different shape to later ones.

 

[Ronny]

F-135 might be accommodating LO requirements as well as air flow requirements. Early F100s have a different shape to later ones.

F110 also have pointy nose though.
Also isn’t F-135 hidden from view due to the S-duct already?

 

[siegecrossbow]

Seems to me that the sharper cone takes up smaller space. Not sure if that had anything to do with the design.

 

[Ronny]

Seems to me that the sharper cone takes up smaller space. Not sure if that had anything to do with the design.

There is nothing in front of the engine so I don’t think it really matter

 

[publiusr]

Now early Soviet jets being Whittles?-might have needed blunt designs-and habit kept that look?

 

[eagle]

I'm not sure, but I think one reason the Volvo RM12 got a pointy cone was to increase bird strike resistance. The F404 has a blunt cone. The other reason was probably increased airflow.

 

[Trident]

Spinner shape is largely a question of OEM preference I think - it does have a bearing on things like FOD rejection round the core and (especially in airliners) ice accumulation, but you can execute a successful design either way. Which is also why you see manufacturers sometimes switching between styles (basic AL-31F is blunt but 117S is pointed, or F110 and F404, as eagle mentions). It's definitely not a Russian vs. US thing.

 

[Ronny]

Spinner shape is largely a question of OEM preference I think - it does have a bearing on things like FOD rejection round the core and (especially in airliners) ice accumulation, but you can execute a successful design either way. Which is also why you see manufacturers sometimes switching between styles (basic AL-31F is blunt but 117S is pointed, or F101 and F404, as eagle mentions). It's definitely not a Russian vs. US thing.

Now it sound like old jet engines have blunt nose and newer one have pointy nose

 

[sferrin]

Spinner shape is largely a question of OEM preference I think - it does have a bearing on things like FOD rejection round the core and (especially in airliners) ice accumulation, but you can execute a successful design either way. Which is also why you see manufacturers sometimes switching between styles (basic AL-31F is blunt but 117S is pointed, or F101 and F404, as eagle mentions). It's definitely not a Russian vs. US thing.

Now it sound like old jet engines have blunt nose and newer one have pointy nose

GE4 (SST) and J58 both had blunt.

 

[Trident]

Now it sound like old jet engines have blunt nose and newer one have pointy nose

For military engines that may well be the case, possibly due to RCS considerations, as Paul suggests. In the civilian world though, spinner shape has almost been characteristic enough to tell the engine manufacturer by in the past 30 years or so. P&W is blunt, GE short & pointy, RR long & pointy (almost conical). Ukraine's Progress is very RR-ish, Russia's Aviadvigatel GE-ish.

Exercise for the reader: can you tell, at a glance, which joint-venture partner was responsible for the design of the fan module on the Engine Alliance GP7200 and IAE V2500, respectively ?

 

[Ronny]

Now it sound like old jet engines have blunt nose and newer one have pointy nose

For military engines that may well be the case, possibly due to RCS considerations, as Paul suggests.

In aircraft with RCS consideration, isnt the view to the engine cone is blocked by inlet duct already?

 

[TomcatViP]

@Trident : nice one. It's more clear that way.

 

[F119Doctor]

Lots of considerations:
- strength/weight. Round is probably stronger
- anti-ice system design
- inner flow path shape
- bird strike capability
- stealth shaping
- mounting system
- bearing compartment shape underneath
- sensor mounting (F100-220/229 Ps2 probe)