BTW, your company site is nicely done.
I am sure Williams International or other propulsion people at that level have the experience and software to just plug your numbers in and get a near optimum prototype design. But what fun is that?
I don't know what the overall constraints are with your application - max efficiency - compactness, etc., but bigger WILL be better at that speed and thrust. A bell mouth entry will also help, but that will increase the overall diameter which your design may not permit.
If the fan can have an effective inflow area of, say, 8 in dia. at 250 kph, the rest of the propulsion numbers will fall into place giving a thrust number for an assumed fan efficiency and power input. This is just physics so far.
Your thrust HP at 30 lbs thrust is 12.4 HP. A fan and duct efficiency of 75% and a propulsion efficiency of 60% would dictate a shaft horsepower requirement of 27.5 HP. The perfect Williams Int. designed fan might get close to 85% eff. If it did, that would reduce the HP req'd to only 24.3 HP or so.
Actually, if the inflow area at speed is 8 in dia, the propulsive efficiency will be less, about 58%. As you can see, the power req'd will depend more on fan size than fan refinement, since fan SIZE has most to do with mass flow and the resulting propulsive efficiency. Getting a 75% eff. fan should be fairly straightforward, but will take some work. Expect to turn the fan aprox 30,000 rpm.
There is a beta axial flow design program called COMPR graciously provided by these folks at:
Since your fan is really a single stage axial compressor, you may be able to get some good from it. It is pointed at full sized jet engine design, so you will have to do some adjusting. For your smaller sizes and lower Re, the blading will tend toward thinner sections, wider cords, fewer blades and lighter loading of the blades. But, the basic design geometry should hold.
Of course, if there is a substantial budget for this R&D, a team of consultant and some high end software is in order. This is my shoe string approach.
