I was talking to one our resident PHd's here at the Rocket Lab at lunch today about that and he said that a converging cooling inlet designed correctly for the speed of the airplane and cooling air flow requirements of the engine would increase the density of the air used for cooling over what we get with our stock pressure cowling. The denser air wouldn't have to travel as fast through the engine to pick up heat from it. (Lower velocity = less drag?) He also said that a properly designed divergent outlet could allow the heated air to generate a few pounds of thrust on the way out. I think that would entail a complete re-design of the cowling, and possibly a prop extension to make room for a long enough inlet. Not a trivial pursuit. Such a project would have to be a labor of love for someone.johneeb wrote:Miles etal,
Do you have an explanation of cooling drag and any ideas on how to eliminate it?
I've seen systems like this on some of the faster homebuilts but I have no idea what the results have been.
I have an acquaintance here who works for Scaled Composites who has designed a carbon composite cowling for Lycoming O-360 powered 170s for a friend of his. (He distributed some literature at the Tehachapi C-170 convention last year.) Maybe some of you Alaksa guys have seen that cowling, as it is currently undergoing STC testing up there (FSDO is more cooperative than in SoCal). I don't think it incorporates the converging/diverging idea as much as it's a lighter weight, more aesthetic way to wrap a Lyc on a 170.
Miles
