Intake Screens on Jet Engines ?

[aseanaero]

With the frequent damage and danger to turbofan and jet engines from items like FOD and bird injestion I wonder what technical issues preclude the use of a wide opening wire mesh intake screen ?

Is the effect on intake efficiency that dramatic that it's not practical or is there some other reason that precludes a cleverly engineered solution ?

[leewan]

For a start, deicing the wire mesh would be a tricky issue. And it would also affect the airflow into the engine thereby impacting the efficiency. And what do you do when a couple of birds gets stuck on the wire mesh ????

[Intruder]

1) Drag.

2) Thrust reduction.

3) Longevity.

4) When they break, they become FOD, too...

[Canuckbirdstrike]

The simple reason is that the impact force increases as the square of speed. Start doing the math of even a 2.5 lb bird hitting a surface at 250 knots and the force is high enough that building any sort of effective screen acnnot be practically done.

Take a look at bird strike damage pictures at even low speed and you will see that even airframe structures are not immune to damage.

This is a great theoretical idea that surfaces regularly, but is currently an engineering impossibility.

[aseanaero]

In 2050 an intake laser matrix to chop the bird up into engine digestable bits :ok:

[Rainboe]

Well one day they will simply install automatic phasers to zap FOD from getting into the intake. They work very well because we have all seen in Star Trek, things go all silhouettey and then disappear completely, possibly just giving an instantaneous view of the skeleton before vanishing. Quick, clean and safe, they are undoubtedly the best solution. But until they are invented, we are going to constantly get this daft chestnut forever resurrected by people who don't know about trying Search.

In case people think Star Trek thingummies are daft, tell me in what way my iPhone differs from a Tricorder? (apart from not giving you a complete medical with a 'tweeting' sound). We laughed at them then, but they are here.

[jefferybond]

If phasers exist, then so do warp-drives. Problem solved!

[SNS3Guppy]

Intake screens have been used on some turbojet equipment. Intake screens are commonly used on some turbopropeller equipment, too.

[good spark]

older generation engines such as the p&w jt3 had the no1 bearing in the inlet casing so a bird stands a good chanch of being reduced to a mush before it hit the fan,
later engines with big fan technology like cfm56 etc no1 bearing is behind the fan so no protection
best thing to do is keep your aircraft with big fan motors out of africa.

[cessnapuppy]

In case people think Star Trek thingummies are daft, tell me in what way my iPhone differs from a Tricorder? (apart from not giving you a complete medical with a 'tweeting' sound). We laughed at them then, but they are here. indeed. With a little bit of practice, you can use your IPHONE to have your prostate checked! Go ahead, try it! (you know you want to!)

[Port Strobe]

In 2050 an intake l@ser matrix to chop the bird up into engine digestable bits

The way some cost cutting measures are leaning there'll be no wastage there, chopped bird will be tapped off at the HPC and on the crew menu in no time!

[Bruce Wayne]

Rainboe... a Trekkie !! who would've thunk it !! :ok:

[Rainboe]

Go on- I got a feeling I will regret this....but....I will lay my head on the block....how do I check my prostate with an iphone? Is there an app for it? Did you know it even has an app to measure windspeed? I love it.

They got to forget that Transporter thing, or we are all stuffed in this industry!

[lomapaseo]

Go on- I got a feeling I will regret this....but....I will lay my head on the block....how do I check my prostate with an iphone? Is there an app for it? .....

First, you have to bend way over

[Rainboe]

Before you go any futher, I don't think I can reach! I think I maybe a little out of tune with the world in not wanting to take that any further! I thought there maybe an iProstate app for 59 pence- it would not surprise me in the least.

[TURIN]

Is there an app for checking your sight. The iEye? :}

[muduckace]

One strike and you would not just be shredding bird but damaging metal not to mention creating less airflow into the inlet that contributes to many other turbine engine problems. The current designs are better at tossing the chickens into the bypass flow, less and larger blades to damage on the fan. Trust them, they have a good handle on it.

[NSEU]

"Is there an app for checking your sight. The iEye?"

Yes, one especially for Star Trek captains.. .the "iEye Captain".

The engines canna' take any more FOD, captain...

[Mech one]

I seem to remember a Westland Wyvern from HMS Eagle (813 Sqdn), fitted with intake guards, went down in a Norwegian Fjord around about 1957 time. The most likely cause was thought to be engine failure due to the intake icing over. Anyone with any history on this incident?

[barit1]

Lots of helos use separator devices, variously called EAPS (engine air particle separator) or IPS (inertial particle separator) to remove sand, dust etc. from inlet air. It's a bit of a drag on engine performance, but pays off by reducing compressor erosion for longer service life.

Depending on the dimensions of the device, it may be effective on birds, but could be a real hazard in ice.

The H-53's deployed on the Iranian hostage rescue mission (1979) used EAPS, which was probably a mistake because they reduced engine output (and thus helo lift capacity); When you're on a life-or-death mission, you really don't care if the engine lasts an extra 2000 hrs. :rolleyes:

[muduckace]

I wonder if a device similar to a blender protruding out of the nose cone to chop/dice and deflect out to the bypass area would be effective w/o disturbing airflow.

[Jackcon]

First and foremost, which size wire mesh would you be looking at? Are you talking about something fine, like lets say 80 x 80 mesh? Or something with more of a wide opening like a 4 x 4 wire mesh? (Difference can be found here: Custom Wire Cloth - Belleville Wire Cloth Co - Cedar Grove, NJ (http://www.bwire.com/) )

The fine wire mesh would probably restrict air flow too much. This would cut down on air flow almost near the 50% range and for obvious reason that will not work. The larger wire mesh with bigger openings presents different problems, the main one being a bird sticking to the mesh and staying there for an entire flight. I don't see this working, but there may possibly be a way to angle the mesh and get this done?

[barit1]

I have read of an early axial-flow engine (J47) with retractable inlet screen segments - used during TO & low-altitude ops. They retracted outward into the inlet case when not needed.

Not sure how successful they were.

[blah blah blah]

Anyone remember the early MiG 29 and its louvres? Or the later variants with mesh screens, much like the SU 27?

[EEngr]

blah

I was just thinking about the MiG system as I scrolled by your post. Good for FOD prevention on takeoff and landing from substandard runways. But its a performance penalty (weight and complexity) that the military is willing to accept. Not so for commercial.

As others have stated, this may work well at low speeds (takeoff and landing) with runway debris. But bird strikes at higher speed will need too much structural strength. Better to clean the runway and shoot and eat the birds.