Cooling air flow over/through the engine is indeed determined by the pressure differential at the engine. However, in the apples-to-apples comparison don't loose sight where that pressure differential comes from. There is the ram air due to the hurricane force winds hitting the front of the cowl and the suction created at the exit of the cowl. Relatively smooth flow to and from the engine also may help. Turbulence in the cylinder fin area helps heat transfer from the hot fins to the cooling air. If the heated air does not get out of the cowl easily, then the flow is diminished accordingly. Your fax NACA exit ramps may do wonders for the exit flow or maybe not. Some flow measurements in that area at the exit ducts might confirm or deny the utility of your design. If flow measurements are not practical, perhaps some tuft testing on the bottom of the fuselage and cowl may yield some useful info.
Sid Wood Tri-gear KR-2 N6242 Mechanicsville, MD, USA smw...@md.metrocast.net In the interest of testing, pure science, the pursuit of happiness and the ultimate truth, Oscar Zuniga suggested pressure testing my plenums vs Joe's more conventional baffle setup, especially since we already had some pretty good comparison info from earlier. What else would you expect from one of Southwest Research Institutes's engineers? So he mailed me his Dwyer differential pressure gauge with 0"-10" of water range, and I flew it Sunday with one end in the plenum and the other under the cylinders, in an effort to determine that pressure difference between top and bottom sides of the engine. I got a lot of good info, but the other side of the coin is that we'll do the same with Joe's engine at Corvair College #16 so we can compare apples to apples an get an idea if plenums are an advantage over traditional baffles, or it's a wash. Corvair College will be held November 6-8 at Ed Fisher's hangar at White Plains Airport in Gilbert, South Carolina ( http://www.airnav.com/airport/SC45 ). See http://www.flycorvair.com/hangar.html for more info, but space is limited. Bring a good attitude and a desire to learn about Corvair engines if you show up (and bring me a couple of dark ales, please). Mark Langford N56ML "at" hiwaay.net website at http://www.N56ML.com
