When I was talking about where I was in the project, Harry asked me about my baseline numbers. As a Six Sigma Black Belt, I know all about data collection, I just get lazy and don't practice what I know I should do.
So after talking to Harry, I went out and made a ground static run, short test flight, and gathered a little more data.
Total cowling inlets: 22 sq. in
Total cowling outlet 28 sq. in. (kind of estimated)
Static & ground runup
ATIS Temp/dew: 27/16 C = 80/61F
Baro: 30.03"
Dynon Outside Air Temp (OAT) sensor: 84F = 29C
Static RPM 2,400, MAP 30"
Test Altitude: 5,500'
OAT: 59F = 15C, Dynon Density Altitude: 6,700 ft.
WOT RPM: 2,850 - 2,900 RPM MAP 24.5"
IAS: 170 mph, TAS: 188 MPH
Oil temp: 215F
I found some test data from May 23, 2005, also flown at 5,500 feet. At that time, I was able to get about 3,000 RPM and had a corrected airspeed of 199 mph.
I'll refer back to this post, to see what effect my changes make.
4 comments:
Hi, nice web page. I was looking at your engine combustion air inlets and comparing them the harry's inlets. It appears that your inlets terminate at a right angle to the cooling air inlets. I would imagine in this orientation they may see fairly low pressure as the velocity in the plenum may be fairly high perpendicular to the combustion air inlet, creaing a vacuum in the combustion air inlet relative to the plenum pressure. Harry's inlets terminate with a ninety degree angle facing forward to take advantage of dynamic pressure recovery. They didn't end up this way on accident, nor was their positioning accidental. I personally witnessed harry spend many days measuring they dynamic pressure in different parts of the plenum inlets to achieve optimum location of the engine combustion air inlets. I have also built a plenum and spent more than a few hours making modifications. One lesson learned was that the pressure in the plenum is not constant. This is due I believe to the very low pressure of the air with respect to ambient in the plenum, about 1/2 psi, being dominated or at least altered by the inertial effects of the air, which, are like I said, at least equally important to the pressure. Again nice site thanks for sharing.
Good observations, Bryan. I also realized that my inlets are positioned in the expanding region of the plenum, therefore increasingly lower pressure. Changes are in the works to this area, as we speak.
I’ve been following your blog for several months, very interesting stuff. I’m a retired mechanical engineer who played with CFD for about two years on some air heated dies.
From that and my fluid dynamics book I have found that when you have high velocity flow through a “T” very little flow can make the turn into the branch. There is a large separation bubble that extends most of the way across the side tube and a very narrow band of flow into the branch. A “Y” might be better or even turning vanes like in a closed loop wind tunnel.
The lowest loss elbow has a bend radius (measured at the centerline) at least 4 times the tube diameter. A “Y” designed with this in mind may solve the problem. Hope this helps.
That is a good guideline that I wish I knew about a year ago. But I will remember it as refinements are added. Thanks.
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