I ran into something interesting. One of our EAA members has a Zenith 601 with an O-200 that has been having temperature problems. I have written about it here before. He put an oil cooler on it last summer which helped but oil temps are still high given ambient temps. A couple weeks ago he asked me to help put a scoop on the bottom of the cowl to blow air on the sump to try to cool the oil more. I wasn't optimistic about the effectiveness of this idea but I went ahead and helped him.
I cut a 5"x1"slot in the bottom of the cowl and bent up a simple scoop out of flat stock to put over the slot. Then I put an air deflector inside to try to channel the air over the sump.
He has flown it a couple times for several hours. The scoop didn't seem to help the oil temp but CHT's are about 30 degrees lower. He thinks the air coming in the scoop is somehow accelerating the flow inside the cowl and out of the cowl exit. I don't see how that could be. After some thought, I now think the the scoop is generating vortices which are accelerating the flow past the cowl exit on the outside and lowering the pressure there so more air is flowing through the cowl.
This makes me wonder if getting rid of the scoop and putting vortex generators on the forward lower cowl would be a better solution. Has anybody done this?
I cut a 5"x1"slot in the bottom of the cowl and bent up a simple scoop out of flat stock to put over the slot. Then I put an air deflector inside to try to channel the air over the sump.
He has flown it a couple times for several hours. The scoop didn't seem to help the oil temp but CHT's are about 30 degrees lower. He thinks the air coming in the scoop is somehow accelerating the flow inside the cowl and out of the cowl exit. I don't see how that could be. After some thought, I now think the the scoop is generating vortices which are accelerating the flow past the cowl exit on the outside and lowering the pressure there so more air is flowing through the cowl.
This makes me wonder if getting rid of the scoop and putting vortex generators on the forward lower cowl would be a better solution. Has anybody done this?
