Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Airflow In The Engine  
User currently offlinesurajit001 From India, joined Dec 2012, 7 posts, RR: 0
Posted (1 year 10 months 4 days 4 hours ago) and read 3740 times:

When the airflow intake into the engine is disrupted, the engine might surge. Because the high pressured air inside the engine already will have nothing to push it out of the engine and hence it may try to escape from the front or back of the engine creating engine surges. My question is how is the airflow into the engine disrupted sometimes? Because whatever happens in the core engine, I feel the inlet of the engine gets unaffected. Air can enter the engine at any conditions even there is some problem inside the engine. Then how is the airflow intake into the engine gets disrupted? I am a starter into the concept of aerospace and so these questions have been baffling my mind. Please help me.

7 replies: All unread, jump to last
 
User currently offlinejetlife2 From United States of America, joined Jul 2006, 221 posts, RR: 25
Reply 1, posted (1 year 10 months 3 days 23 hours ago) and read 3652 times:

The most common cause of inlet disruption is crosswind. All modern engines and inlets are designed and tested to withstand a significant level of crosswind. When the air approaches the inlet from an angle the inlet itself causes distortion into the front to the engine. This provides turbulent and unsteady airflow into the engine. Eventually the level of distortion introduced into the engine is so high that some part of the engine cannot handle it causing aerodynamic stall of one or more stages. Hope that helps.

User currently offlinedakota123 From United States of America, joined Aug 2006, 116 posts, RR: 0
Reply 2, posted (1 year 10 months 3 days 15 hours ago) and read 3533 times:

Another common way for surge to develop is if one or more sets of variable-incidence stator vanes are off-schedule, such that the volume of air fed to its associated compressor stage from the preceding stage is too great and an aerodynamic stall results. When this happens airflow through the compressor stops partially or fully, or in severe cases even reverses. Conditions at the inlet absolutely will be affected, if even only momentarily as the stage unstalls as controls monitoring for such an event ntervene to alleviate the condition (or if the reduction in airflow as a result of the stall itself unstalls the stage, as can happen if the stator vanes are only slightly off-schedule). Worst case, the engine flames out due to the disruption or is tripped off by the control system.

Not quite what you were asking about, I don;t think, but still may help.

[Edited 2012-12-21 15:48:20]

User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2565 posts, RR: 25
Reply 3, posted (1 year 10 months 3 days 14 hours ago) and read 3498 times:

Quoting dakota123 (Reply 2):
Another common way for surge to develop is if one or more sets of variable-incidence stator vanes are off-schedule, such that the volume of air fed to its associated compressor stage from the preceding stage is too great and an aerodynamic stall results

It's more the case that variable stator vanes being off schedule will mean the angle of incidence at the next compressor stage is not optimal, which may lead to a stall.

The problem with an axial compressor is that the air is effectively being driven up hill, against the pressure gradient. It doesn't take much disturbance to cause a partial or complete breakdown of flow. Too much airflow at too low rpm will cause surge. Inlet guide vanes and VSVs help to guide the air to more optimal angles. Surge bleeds can be opened to take air out of the compressor, reducing airflow and increasing the surge margin and the fuel control unit will have an acceleration limiting function to keep rpm and airflow relationship away from the surge boundary.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineTWA772LR From United States of America, joined Nov 2011, 2185 posts, RR: 1
Reply 4, posted (1 year 9 months 3 weeks 3 days 8 hours ago) and read 2868 times:

Quoting jetlife2 (Reply 1):
causing aerodynamic stall of one or more stages.

Is that how compressor stalls happen?



Go coogs! \n//
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 5, posted (1 year 9 months 3 weeks 2 days 20 hours ago) and read 2753 times:

Quoting TWA772LR (Reply 4):
Is that how compressor stalls happen?

One stage (or even one blade on one stage) will go first but the instability tends to cascade through the compressor very quickly. There are stable partial stall configurations (google "Rotating compressor stall") but that's less common.

Tom.


User currently offlineAcey559 From United States of America, joined Jan 2007, 1536 posts, RR: 2
Reply 6, posted (1 year 9 months 3 weeks 2 days 18 hours ago) and read 2720 times:

Turbulence can cause engines to stall as well. That's why we turn the ignition on during turbulence, so it reduces the likelihood of that happening.

User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 7, posted (1 year 9 months 3 weeks 2 days 17 hours ago) and read 2703 times:

Quoting Acey559 (Reply 6):

Turbulence can cause engines to stall as well. That's why we turn the ignition on during turbulence, so it reduces the likelihood of that happening.

I don't think having the igniters on reduces the chance of stall, it just improves the chance of prompt recovery. Unless the engine changes compressor scheduling with the igniters on...

Tom.


Top Of Page
Forum Index

Reply To This Topic Airflow In The Engine
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
A Tube In The Engine, What Is It? posted Tue Apr 22 2003 15:22:46 by Cricri
How About An Engine In The Wing For Airplanes? posted Fri Jan 9 2009 07:11:06 by Panais
Engine In The Tail End Of A 747? posted Mon May 5 2008 00:37:58 by 1821
In The Cruise Engine Failure Twin Question posted Mon May 22 2006 00:24:08 by JulianUK
Engine Probles Then Smoke In The Cockpit posted Thu Jan 15 2004 20:14:52 by Captjetblast
What Are The Engine # Configurations In Aircraft? posted Thu Oct 4 2001 23:39:16 by Sonic99
Engine Start In The 764 posted Fri Sep 15 2000 06:42:46 by Gnomon
Aircraft Tyres Manufacturers In The World posted Wed Dec 19 2012 05:12:37 by Tupolev160
Why Are There Still Levers In The Cockpit posted Tue Dec 18 2012 01:56:51 by 456
B707 VMC Accident In The Past. posted Thu Dec 6 2012 17:19:31 by Qantas747300

Sponsor Message:
Printer friendly format