Thursday, November 20, 2014
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Cooling System Design
March 14, 2009

I had some online discussions about removing the engine driven water pump and replacing with an electric pump to save some horsepower. Some rough numbers indicate that the EJ-22 pumps something around 40 gallons per minute at 4500 rpm. A rough rule of thumb (I am told) is 1 hp for every 25-30 USGPM. So, I could potentially save about 1 hp at cruise rpm of 4100. Bummer, that just isn't worth the effort....

November 15, 2003

More progress. I have decided to install the radiator in the tail and use a P-51 style scoop. Currently am working on getting my radiator installed.

EJ22-RadiatorInTail-Fitting1-800.JPG

The final result will look something like this:

Q2-3View-Radiator-P51Scoop.gif

Yep, two fairly good size holes will need to be cut in the bottom of the fuselage (tailcone). I haven't calculated these hole sizes yet but I plan to install a couple of glass stiffeners down each size of these holes on the floor of the tailcone. The coolant will be routed thru the cockpit. No, not my favorite thing either.

The radiator duct will be a series of parts. Inside the plane, there will be three parts. 1)Duct from fuselage bottom to front side of radiator. 2) Duct from aft side of radiator to front side of bulkhead. 3) Aft side of bulkhead to fuselage bottom. This appears to be the most workable and most solid way of putting it all together. The duct on the outside of the fuselage will be one unit glassed onto the fuselage.


November 11, 2003

Winter has arrived so I'm back to cooling system design. I have decided that there is just not enough room in the cowl for a radiator and ducting so am back to the in-tail idea. The following image shows my three basic ideas:

FinleyRadiatorIdeas.gif

In all cases, the radiator (a typical car type - VW Radiator is my current plan) is mounted "in" the tailcone bulkhead.

#1 scoops the air from the bottom and out the top.
#2 scoops the air from the bottom and back out the bottom.
#3 scoops the air from twin side ducts (one on each side of the fuselage) and then out the top (or bottom).

There are plenty of pro's & con's. Space is a major issue, adding to that are bulkheads, split line, and other equipment. It's kinda hard to see in drawings of this scale but the ducting has to make some fairly radical bends which I KNOW is not efficient.

This image is an expansion of the side scoop idea (#3 in the above image) except the outlet is aft of the inlet rather than on top of the tailcone.

Q2-3View-Radiator-ScoopSides.gif

I have had a fair amount of discussion with others about the importance of getting air from a high-pressure location and dumping it in a low pressure location. To help achieve that, I have been referencing the following fluid dynamic information that David Lednicer created.

Q2-Pressure-UpperVsLower.jpg

Q2Side-FluidDynamics.jpg

I moved some really old cooling design stuff off this page. Click here to see it.

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