Our DIY engines make acceptable thrust , the one in my bike video produced ~110 lbs of thrust as a pure jet , but with a freepower turbine downstream , I used a third stage Allison C20 heli engine turbine wheel , produced 115 rear wheel horsepower on the dyno . http://www.youtube.com/watch?v=CplnY9TG7NE
Our current bike build uses the 10/98 "micro" engine with ~40% more airflow 98mm comp inducer vs 89 mm for the Garrett TV84 turbo , and should produce ~150 RWH in a bike weighing ~150 Kg - 330 lbs compared to the first bikes ~280Kgs- 600 lbs ........................this bike will use the Allison C20 4th stage turbine wheel for the freepower turbine ...............its ~8.5 " diameter and will spin to ~32,000 rpm , the 10/98 gas producer spins its 5.55inch diameter compressor to ~70,000rpm at full power .....................the compressor wheel consumes ~230 HP .
A 7hp IC engine will spin your "fan" and blow some air , but it won't produce much pressure , pressure requires lotsa horsepower at the airflow rates that we use in a turbine engine .
The TV84 in the bike video consumes ~1.8 lbs/sec of air , thats ~24 cu ft/sec - 1400 CFM , the 10/98 engine close to 2000 CFM , your MASSIVE wheel could be flowing several thousand CFM if designed correctly ..................that is going to need huge amounts of HP.
Heres some maths for you to digest ..............assuming your axial compressor wheel is 10" dia with a 2" dia hub , thats a flow area of ~75 sq inches or ~0.5 square feet ,..................now axial compressors have inflow airspeeds of say 500 ft/sec , so ~250 cubic feet /second of air -15,000 CFM or ~19 lbs/sec mass flow .
If your compressor wheel attains a nominal 1.2:1 pressure ratio then there would be a 15.4 deg C rise in the air temp if the compressor is 100% efficient , your will be lucky to be 60% effic . , this will mean a temperature rise of ~26 deg C , to "convert " that 26 degrees into horsepower we do a bit of simple maths and it comes out at 15.7 hp/lb/sec , multiplied by our 19 lbs/sec and we get a horsepower requirement of 298 horsepower .
A 10inch wheel with a 1,500 ft/sec tip speed will rotate at ~35,000 rpm , assuming you wish to run the wheel at 5,000 rpm , pressures go up at the square of blade speed , you will get only 2% of the max pressure rise , 2% of a 1.2 pressure ratio is ~2.5% of ambiant 14.7psi or ~0.36 psi or ~8" of water , this is about what a leafblower turns out , now there will be a temperature rise of ~3 degrees , but you'll never get to this point because the power requirement is too great for a 7hp engine to spin even if airflow rates were reduced to half , you'd need to adjust your blading to a fine pitch setting and reduce flow appreciably .
This is not a workable proposition , please change your direction and start using much smaller components , this current design isn't workable , and I'm not going to waste anymore time explaining why , get yourself some turbocharger bits which have some hope of working .