Cooling inlets placement, airflow
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Cooling inlets placement, airflow
Hello, I am a pilot student. I have purchased experimental UL airplane and experience issues with the poor engine cooling. I've found an article recently, but I am not allowed to link it here (please search it in google, it is the first link - published on kitplanes): www.kitplanes.com/cooling-inlets-part-2/ and I am wondering if it describes my problem, because I am affraid it does.
My plane has cooling inlets on the sides of cowling, which, according to the article, is the worst possible placement. I will repeat related paragraph below and attach picture of my plane. There are two radiators on the sides, one for motor block, second for turbo intercooler. The air outlet is at the bottom - bottom cover (not installed on 1st picture) ends some distance before and below the cabin floor.
Can somebody help?
It’s also important to avoid placing inlets in areas where the flow is moving fast and the air pressure is low. A particularly poor place to locate an inlet is on the sides of the cowling, particularly in the forward half of the side of the cowling. This is a natural low-pressure zone, and the inlet will have to capture fast-moving air and use the momentum of that fast-moving air to force it down the inlet. There is no easy way to slow the air down efficiently once it passes into the inlet, so a side-mounted inlet is likely to have poor flow and low pressure recovery. In some cases, the external air pressure is low enough that the inlet cannot recover enough ram pressure to drive the air into the duct, and it’s not uncommon to have poorly placed inlets flow backward if they are in a low enough pressure zone.
Now I don't know how to attach the picture, because they seem to change into hyperlink and I am not allowed to use hyperlinks as a new member here :-(
Well it is Yetti j-03, this airplane: http://www.aerohangar.cz/ultralight/...tti-j-03-120hp I hope this will be allowed to post here (?)
My plane has cooling inlets on the sides of cowling, which, according to the article, is the worst possible placement. I will repeat related paragraph below and attach picture of my plane. There are two radiators on the sides, one for motor block, second for turbo intercooler. The air outlet is at the bottom - bottom cover (not installed on 1st picture) ends some distance before and below the cabin floor.
Can somebody help?
It’s also important to avoid placing inlets in areas where the flow is moving fast and the air pressure is low. A particularly poor place to locate an inlet is on the sides of the cowling, particularly in the forward half of the side of the cowling. This is a natural low-pressure zone, and the inlet will have to capture fast-moving air and use the momentum of that fast-moving air to force it down the inlet. There is no easy way to slow the air down efficiently once it passes into the inlet, so a side-mounted inlet is likely to have poor flow and low pressure recovery. In some cases, the external air pressure is low enough that the inlet cannot recover enough ram pressure to drive the air into the duct, and it’s not uncommon to have poorly placed inlets flow backward if they are in a low enough pressure zone.
Now I don't know how to attach the picture, because they seem to change into hyperlink and I am not allowed to use hyperlinks as a new member here :-(
Well it is Yetti j-03, this airplane: http://www.aerohangar.cz/ultralight/...tti-j-03-120hp I hope this will be allowed to post here (?)
Last edited by lukehe; 12th Apr 2024 at 15:02.
The article you linked to shows inlets for air-cooled engines. Your Rotax 915IS is (mostly) water cooled and should work without any issues with the cooling setup on your aeroplane, if everything has been hooked up, cowled and installed correctly. From the description I get the impression that you are running a partially non-standard engine installation in that there is a reducer(?) involved? I wouldn't trust internet wisdom but take the aeroplane to a knowledgable aircraft mechanic. Because it is an experimental, you cannot rely on the basic information and experience from the factory and others, you may be involved in some (light) test flying along the way, even if you're not aware of it.
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There is water cooled automotive engine. It cools poorly. I didi mod of air intake, extending it more upfront, but idt did no big improvment. I wonder if the air output can be the bottleneck now.
Who says he has a Rotax 915? I'd not be surprised if the engine were either a local conversion of some car engine, or the six-cylinder Jabiru 3300.
Agreed though that there is a world of difference between cooling air-cooled and liquid-cooled.
Agreed though that there is a world of difference between cooling air-cooled and liquid-cooled.
Last edited by Jan Olieslagers; 16th Apr 2024 at 14:20.
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Such a long walk down this thread and still no photograph with the cowling removed, no sense of where anything is. The scoops look like they capture air into the cowling, but then the exhaust looks restricted in comparison and has some difficult route to pass air over anything inside the cowling.
In other heat transfer systems I've seen, they are designed to allow air to bypass the item that generates heat; usually a big problem with finned heatsinks as even a small gap over the tops of the fins is a far less restrictive path than it is through the fins.
In cars there are often fan shrouds to seal the entire radiator to force all the make-up air ejected by the fan to go through the radiator rather than bypassing from under the car.
In other heat transfer systems I've seen, they are designed to allow air to bypass the item that generates heat; usually a big problem with finned heatsinks as even a small gap over the tops of the fins is a far less restrictive path than it is through the fins.
In cars there are often fan shrouds to seal the entire radiator to force all the make-up air ejected by the fan to go through the radiator rather than bypassing from under the car.
