Combustion Chamber Turbulance to Lower Octane Requirements

Discussion in 'Engines' started by Balljoint, May 9, 2014.

  1. Balljoint

    Balljoint Member

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    This may not have an answer; but was there any aviation engine implementation of Harry Ricardo’s work around 1920 to lower the octane requirement by inducing combustion chamber turbulence? It seems that most aviation engines have hemispherical combustion chambers that tend to be turbulence free. Induced turbulence by swirl or squish as the piston moves through the compression stroke can increase the rate of flame travel by convection 15X or better. Fuel mixture detonation is combustion rate sensitive such that a faster flame travel appreciable lowers the octane requirement. Seems like a natural for supercharged engines.

    Ricardo was active during the war but mainly as a proponent of sleeve valves.
     
  2. GregP

    GregP Well-Known Member

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    Harry was a wonder. Don't know about chamber turbulence, but the German MW50 system was a direct result of Harry's work.
     
  3. Shortround6

    Shortround6 Well-Known Member

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    Like a lot of things you have conflicting requirements and effects. The "hemi" head allowed larger valves to be used than a 'squish' head (in general) and in the 1920s with gasoline there is only so much compression you can use anyway. 6:1 was high compression in those days for an supercharged engine. Flat heads (L shaped combustion chamber) offer a lot scope for 'squish' but don't breath very well.
    A lot of time they were balancing fuel efficiency against power. Features that promoted high fuel efficiency often did not promote high specific power either form displacement or weight.

    You also have production considerations. The more complicated you make the cylinder head the harder it is to produce.
     
  4. Balljoint

    Balljoint Member

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    A bit of research found the RR did in fact attempt to use the concept in the development “Ramp Head” Merlin B. However, there were localized detonation problems and the need for a workable prewar engine caused them to revert to a safer earlier design. Apparently the concept was not revisited.
     
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