freakingfast

My Feedback: (3)

Would you guys find the following statement accurate?

"In aircraft even slow flying models, when you cool something ram-air/dynamically, generally you want the inlet smaller than the outlet or the airflow stalls and goes around. Usually the outlet should be a minimum 1 1/2 times the area of the inlet. I have seen this problem time and time again where engines or high discharge batteries overheat. It's a common misconception that a big scoop can force air fast out of a little exit."

Kmot

My Feedback: (24)

I think your right. I actually thought the ratio was more like 1:3

the pope

I think your on the right track . I read somewhere that the x3 out let was a bit big as the heated air doesn't expand that much . I think that baffleing and a lip on the outlet to create a negative airflow zone , that sucks air out is a good idea as well in a cowled applications is the key. On F.G. they have a fair bit of info in regards to this and the late P E Rivers has some very useful pics to explain all of this .Try and search and if nobody can find it I think I have it saved somewhere . Cheers the pope

Sport_Pilot

Yes and no. If the engine is well baffled so that all of the air or almost all of the air must go through the fins, then the ratio can be smaller than 1 1/2 times. Actually for a completely unbaffled engine the outlet probably needs to be more like twice the size of the inlet. Many full sized aircraft have ratios of close to one to one with cowl flaps that about double the outlet size.

Rudolph Hart

Sport pilot is dead right popey and have you sold all your jett engines yet??

freakingfast

My Feedback: (3)

Perfect, thanks guys