Click for Mulder Click for Glendinning Click for Delta Click for Nordhavn Click for Mulder

Turbo Inlet Air Flow Question

Discussion in 'Engines' started by Capt Ralph, Mar 20, 2022.

You need to be registered and signed in to view this content.
  1. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    I'm looking to improve my crank case ventilation system on Ole Bertie.
    A new air filter adapter sleeve is required between the 5" turbo inlet and non-OEM air filter (K&N can type).
    This sleeve will also include the low pressure hose nipple to the CCV can (Racor CCV8000). This nipple would be just inches before the compressor blades of the turbo.

    The question;
    On the insides of this sleeve, where is the highest air velocity found (most suction) ; in the middle of the tube or towards the inside surface of the tube.
    I have experiment with a nipple towards the middle with lass than exciting results. If you look at the turbine blades, It looks like more velocity would be on the outside of center.

    For the Air Pilots out there, When a bird gets sucked in, does it hit on the outside or inside of the first compressor blade set.

    I wish I could remember my static air flow instruction from 2 life times ago.
    Those slow brain cells were dealt with long ago.
  2. Robertoman

    Robertoman Member

    Joined:
    Dec 15, 2010
    Messages:
    71
    Location:
    San Diego
    Hey Capt, I don't know what you are exactly trying to do.
    As I recall you have 12-71s, One of the advertisers here has some really nice crankcase breather stuff.
    The new stuff is pretty decent.
    Oh, by the way I recently saw a Russian jet that ingested a projectile and most of the turbine blade damage was toward the outer edge of the compressor blades!
    Does that help?
  3. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Just asking, where is the lowest pressure, (Most vacuum) in the center or sides just before the compressing turbo wheel..
  4. mapism

    mapism Senior Member

    Joined:
    Aug 9, 2008
    Messages:
    2,111
    Location:
    Sardinia
    I would think that the inlet air velocity should be higher in the center, simply due to lack of drag.
    I'm not sure that the comparison with anything hitting jet blades makes sense BTW, because there are centrifugal forces involved with the turbine rotation, that do not affect the inlet section you are interested in.
    Besides, in a turbo (contrarily to jets) the compressed air flow is forced perpendicularly to the inlet, rather than along the same direction.
  5. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Ah, um ur, the front compressor blade of a jet engine works the same way as the front of a turbo.
    However, I do agree with the idea of the sides of the inlet offering drag.
    This is why my first attempt was a angled outlet in the middle inches before the turbo entrance.
    OEM models just have a hose barb on the side of the tube.

    Going to have to make a fan model and recreate my question.
    This could take some serious amounts of brain lubrication. This may take a while since these lubricants do affect the slower brain cell more. I just have to stay on top of these issues.
    Hopefully, some static engineer will come forth before these extremums are implemented.
  6. mapism

    mapism Senior Member

    Joined:
    Aug 9, 2008
    Messages:
    2,111
    Location:
    Sardinia
    I wasn't arguing with the jet engine comparison as such, just with the object hitting its external fan.
    Which I would expect to hit the fan blades wherever its position is in front of them at the instant of impact.
    And right after that, if there's one way it can deviate in its path, I think it's outward, but more due to centrifugal effect than air speed.

    If we stick to the air flow inside the inlet section, I see no reason why it should be much different (speed aside) from a NA engine.
    Hence my inference that the only thing affecting air speed inside the inlet is the drag along its sides.

    That said, if there's something I'm NOT, it's a fluid dynamics engineer.
    So, happy to stand corrected if anyone knows better.
    In fact, you made me curious by now to learn more about this!
  7. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Another thought that I have not expressed but feel it is a part of my problem and question;
    The turbo wheel is supported by its center hub, shaft, bearing and casting to make this all work.
    Like that aircraft jet engine, there is so much center-line, I don't see the max flow at the center just before the compressor rotor.
  8. rtrafford

    rtrafford Senior Member

    Joined:
    Jul 13, 2019
    Messages:
    1,578
    Location:
    Vero Beach
    That air flow is at its best in the center when away from the fan blade, but the velocity meets high pressure at the center of the fan hub, and it accelerates to the outer edges of the turbo. As the air flow has to work around that bubble of high pressure, it will be at its fastest as it reaches the outer edges of the blade.
  9. mapism

    mapism Senior Member

    Joined:
    Aug 9, 2008
    Messages:
    2,111
    Location:
    Sardinia
    Interesting and very logical explanation, thanks.
    When I said that in the inlet section I would expect the air flow to behave similarly to a NA engine, I did think that the fan blade and its bulb are bound to introduce some relevant differences.
    But CR in his OP mentioned a nipple placed "inches" before the fan blade, so I assumed that we were still talking of the unrestricted section of the inlet. Now, I appreciate that this is a bit of a "how long is a piece of string" question, but how large would you think the high pressure bubble can be in front of the fan?
    Just curious.
  10. rtrafford

    rtrafford Senior Member

    Joined:
    Jul 13, 2019
    Messages:
    1,578
    Location:
    Vero Beach
    Haven't studied the dimensions of a DD turbo, but the area is quite small, nonetheless present. In addition the widest portion of the fan blades at the outer edge also create the most low pressure path to work together with the core of higher pressure, setting up the stream.

    I don't recall that hub extending past the blades. I actually recall the hub being recessed slightly. Been too long...
  11. AIRSEP Guru

    AIRSEP Guru New Member

    Joined:
    Jan 18, 2010
    Messages:
    9
    Location:
    Los Angeles
    Hi guys, interestingly enough, the design, size and configuration of the air filter can alter the air flow in relationship to how
    it "hits" the turbo blades..i.e. smooth or choppy w/vortex. That said, sorry to hear you are looking at Racor unit. Walker AIRSEP was factory installed and made standard at DDC during the Penske years. To truly upgrade, install an AIRSEP kit, and all the engineering is done for you, and say goodbye to oil leaks. See schematic example of system. We are happy to help.

    Attached Files:

  12. rtrafford

    rtrafford Senior Member

    Joined:
    Jul 13, 2019
    Messages:
    1,578
    Location:
    Vero Beach
    Interesting discovery. The top 1.25" hose is apparently worn and weakened, losing some of its structure and collapses under load. Replacing all four of these with new silicone hoses...whereas I used to think a hose that was soft and supple was in good shape..........
  13. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    This is happening on your boat? That is some suction if you are collapsing the hoses.
    Are your sep oil filters clogged?
  14. rtrafford

    rtrafford Senior Member

    Joined:
    Jul 13, 2019
    Messages:
    1,578
    Location:
    Vero Beach
    No, filters are new. Hoses are extremely soft. Replacing the hoses, disassembling and cleaning all thoroughly and reinstalling. New hoses are much more firm silicone than the existing. Makes me think they were either an improper replacement prior, or they've just deteriorated with time and heat? Weird. Never woulda thunk it.
  15. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Air-Sep oil collator/filters are new (not air filters)?

    My bud has the old Walker with non serviceable oil collator/separators/filters. Not passing crank case fumes. Think they were on Noahs boat.

    New Walkers have the serviceable oil filters.
  16. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Back to my junk.
    You can see (poorly) the 5.25" turbo inlet but the compressor turbine is only 3" in diameter.
    20220323_115441a.jpg
    So, the question is(was), where would the max low pressure (suction) be just in front of this.

    Here is my prototype air filter with draw fitting inserted in center and side positions.
    20220323_115559a.jpg 20220323_115547a.jpg

    I have been operating with it in-between these positions but always looking to improve.

    Does this help? Any more thoughts from the galleries?

    Side view of air prototype air filter with low pressure fitting.
    20220323_115620a.jpg

    You can see that the pressure fitting would be rite in front of the compressor turbine when installed.

    20220319_133835a.jpg
    Last edited: Apr 2, 2022
  17. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Next idea, Home made manometer.
    Going to apply science to a 44 year old Detroit.

    In recognition of our Great Forum Guy, A measure unit of vacuum may be called;;; A Pascal