I've been busy with the ducted fan projects and have some data. About ten years ago I built a rolling test, called "The Blue Machine," stand to investigate using a CVT as a engine speed reduction unit to drive a propeller. It worked quite well and that another story. As a result of the ME-262 interest I said I was going to build a large ducted fan. So far the 11 inch diameter fan has been tested using my rolling test stand and I have some data. The fan rotor consists of a purpose built hub that holds 16 Rolls Royce Avon jet engine compressor blades and the angle of attach can be set before a test. The max rpm was limited to the 9 hp engine that drives through a Comet CVT. Depending on the blade angle I was able to get the rotor up to 9000 rpm, but the max thrust of 25 lbs occurred at about 6500 rpm. I have a 35 hp 2si two cycle engine that I will eventually the lawn mower engine with. I should be able to get about 100 lbs of thrust with the additional hp.
The Blue Machine is instrumented for engine and fan rpm, fan thrust and torque and airspeed.
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Today I installed a 17 inch diameter fan the has 12 compressor blades from a Russian jet engine. I will run it first with the small engine then install the 2si. I am predicting about 125 lbs of thrust with that unit.
The key to maximizing thrust is high rotor rpm. To get 300 lbs of thrust out of the 17 inch fan would require running it at 19,000 rpm. Unfortunately, the sonic tip speed occurs at about 15,000 rpm and practically speaking 900 feet per second is pushing it structurally. That limits the unit to about 13,000 rpm and 150 lbs of thrust. The only way too get more thrust is to use more blades for more blade area or make a larger diameter fan.
I will report on the 17 inch fan testing later this week. Some photos of the equipment have been attached.