Optimized Induction Airbox for Reciprocating Engines

Discussion in 'Tests and Improvements' started by Toobuilder, Feb 26, 2019.

  1. May 2, 2019 #21

    Toobuilder

    Toobuilder

    Toobuilder

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    Exhaust augmented cooling is used on my Rocket as well (but that's going to be a different thread).

    Concerning the blade effect on ram pressure, it's real. I tested this years ago on my Hiperbipe (link below). The inlet pitot was a 3 inch diameter tube attached to the airbox with a hose clamp.

    http://www.airport-data.com/aircraft/photo/000576349L.html

    This allowed me to adjust the distance from the prop easily. I confirmed that the closer the inlet was to the blade, the higher the MP. This was repeatable.

    It should be noted that I placed the inlet well off center to get as far out on the prop arc as possible. The Rocket is similar, with the center of the inlet well out of the root area at 14 inches.
     
  2. May 2, 2019 #22

    nerobro

    nerobro

    nerobro

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    Awesome work.
     
  3. May 2, 2019 #23

    Victor Bravo

    Victor Bravo

    Victor Bravo

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    How much of a MP increase did you see, compared to an inlet location that was further away from the propeller and/or closer to the center of the propeller? Meaning, of course, if someone put their intake further outboard and close to the propeller, on some benchmark airplane (C-172, T-craft, Beech Bonanza), is there half a horsepower to be found or ten horsepower to be found?
     
  4. May 2, 2019 #24

    Toobuilder

    Toobuilder

    Toobuilder

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    I'd really have to dig to find the numbers that I saw, but IIRC the difference between full aft and full forward was .5 to .75 inch of MP. This was taken from a steam guage (no EFIS back then), so the exact measurement is of dubious scientific value. This airplane was 180 HP and would go 170 MPH in level flight, so there was plenty of Q anyway.

    The compelling point was made however: closer to the blade is better. I did not test variables of the blade station (distance from centerline). I simply went as far out as reasonable.
     
  5. May 4, 2019 #25

    plncraze

    plncraze

    plncraze

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    In Kent Paser's book Speed with Economy he said that one of Ed Swearingen's kids who had designed the induction system for the SX-300 told him to get the prop as close as possible. Paser also angled the intake to catch the air as it was swirling off the prop. Paser also clocked his fixed pitch prop to coincide with the opening of the intake valves. Paser has a formula in his book for intake air volume.
    Also thanks for sharing this!! Your project is AWESOME!!
     
    mcrae0104 and Toobuilder like this.

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