How to match propeller with engine?

Discussion in 'Diesel Engines' started by ZeusGaryulo, May 18, 2016.

  1. ZeusGaryulo
    Joined: Mar 2016
    Posts: 4
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    Location: Southampton

    ZeusGaryulo New Member

    Hello,

    I am helping in the design of a 60' powerboat, is going to have two MAN V8-1200 engines (882 kW-2300 rpm), my question is, should I calculate the propeller to point A (882 kW-2300 rpm), point B (95% rated power-2300 rpm) or point C (95% rated power-95% rated rpm) of the engine curve?

    I have read that is not a good design choice to design for point A, because there is not power allowance if the engine needs to provide some extra power.

    I also have read that diesel engines works really confortable at maximun rpm and almost maximun power (95% let's say), but my doubt is that when the engine gives its rated power it would rotating at higher rpm than rated (103% let's say). That's why I cannot decide between point B and C.

    Someone can help me?

    Many thanks!
     
  2. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 109, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    For longest service life and lowest fuel burn per HP many large engine folks will suggest 80% of rated power at 90% of rated RPM.

    Low fuel burn and long engine life should be more of a concern than the last K of speed.
     
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