Monty Roberts wrote:

Well folks, the inevitable has happened, I closed on a property I have been trying to buy for the last 6 months yesterday. Unfortunately this will once again put the airplane on hold, as well as my heat exchanger data collection. I have a lot of remodeling work to do and a shop to build. I knew this was coming, and as painful as the distraction is, it is necessary.  :-(

So far what I have learned is that for each design there will be an Ideal tube length. This is found by taking the worst case, Vy, army standard air (which is standard air except the temp is about 100 F). You then take the coolant mass flow through the tube, and the heat transfer coefficient (which we need to measure) and the air mass flow across the radiator. You size the tube to give you near ambient air, coolant temp at the exit. The length and width of the radiator will be inter-related due to the fact that as you increase the number of tubes the mass flow in each tube changes, giving a different Ideal length. I'm also pretty sure that the individual mass flows of the air and coolant will be optimized if you base them on the ratio of the specific heats of the two. Anyway the end result of all of this is that you should be able to develop a relationship for this engine where you plug in the climb speed, power output, and radiator core data and you get a curve of length/width ratio for optimum design. So as soon as I get out from under this mess, that is going to be my goal. I am thinking of writing the results in a booklet form. This info is sorely needed. I must have a couple dozen aircraft design books and there is not a single one that address this issue adequately. They simply say cooling drag is a large component of the airframe drag and is a good place to try to improve. No details, or at least no practical details.

The real problem is the airframe integration. It would be really easy to make this engine a pylon mount unit with the heat exchangers all in the pod, a nice inlet in front and augmentor to the rear. But that means multiple engines, expense etc. Of course there is the thought of a larger cosy4/starship clone, or better yet a smaller Piaggio .........  Oh well, first I need a place to live :-)


Monty Roberts
RMI
1795 Berry St.
Fayetteville, AR 72701
tmrbrts@swbell.net

The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
ACRE NL web site.
http://home.earthlink.net/~rotaryeng/            http://www.linux.org