Mailing List lml@lancaironline.net Message #45243
From: Paul Lipps <elippse@sbcglobal.net>
Sender: <marv@lancaironline.net>
Subject: Cooling
Date: Thu, 06 Dec 2007 14:40:30 -0500
To: <lml@lancaironline.net>
    That little curved section you see that's on the right-hand side of the duct immediately below the cylinder is the exhaust from the flange to the mixing box. It flares from the flange to be 5" wide by 0.5" high where it goes into the cooling air duct. The exhaust flow adds momentum to the air to overcome the pressure drop through the fins and thus reduces the cooling drag. Since the air is kept in intimate contact with the fins by the shroud surrounding the cylinder, cooling efficiency is enhanced over the normal baffle system and so I only require 12 sq.in. total cooling-area inlet for my 125HP O-235, which is about 1.4 lb/sec at 10,000' dalt, 200 mph TAS with total flow through the inlets. The engine runs very cool, and I can close down the outlets at the ends of the ducts to get the cylinders up to about 370 F and reduce drag to get about 3-5 mph more.
    I said a mixing box, but it is really a proprietary design which is undergoing the patent proces. It's a special design nozzle which generates a low-pressure where the exhaust flow is introduced to the cooling air and makes up for the pressure drop through the fins. When you see the side view of the box, the exhaust is coming in from the right through that curved duct. It enters the cooling air stream probably about 2" below the bottom of the fins on the head. I designed a one-box cooling-exhaust augmenter using this principle for Kevin Eldredge's Relentless NXT, driven by the exhaust from the two turbo-chargers, and it works extremely well; It's located at the bottom rear of the cowling.  I just recently designed a somewhat-similar two-box arrangement for someone with a fast Glasair. Each box will be driven by two separate exhaust ducts on each side of the engine. It will be interesting to see if he shows a measurable speed increase with this since he has much "before" data on his plane.
    One of the Reno Lancairs had an MT prop I designed, but due to other problems, it wasn't able to be raced. As soon as some info is available about before-after performance with this prop, I hope to release this info, with the concurrence of the owner, of course. Of course, he may not want others to know!
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