Hi Nerd,
I wonder when you suggest using multiple stages of the Tesla turbine, if one of us doesn't understand it properly? (I.E. Me?).
An impulse turbine can develop about 50% of tractive energy - per rotor - I think? (something due to geometry when the gas stream turns 90degrees from input to exhaust direction against each blade? ). But maybe it was "half-speed" (1/4 kinetic energy remaining?). So multiple rotors each extracting 50% of energy (or is that velocity??) leave a lot to be collected by a later stage (I think?), as the exhaust from the first stage can give 50% to the second, then 50% to the third... etc. so the shaft accumulates 50% + 25% + 12.5% etc. thus achieving high efficiencies?
But the whole principle I think Tesla achieved was a single stage obtaining ~80~90% of the energy, so the exhaust contained too little to make a further stage useful? (back then!).
Also, in the Tesla mode the helix is very fine (e.g. there are smoke demos to show this on Utube?). It starts as a coarse helix at lower speeds, but when the turbine achieves true Tesla mode the helix manages to make thousands of rotations from the outer high velocity zone to the centre "near rotor speed at exhaust ports" - which was maybe 1/10th of the initial speed. And energy is proportional to Vsquared... so necessarily Tesla was right in the possible efficiency he could predict - and achieved. All in a single stage. Or maybe I missed something and got it all wrong? (I often do!!). It is all due to the progressive slowing of the gas stream per revolution that the gas stream makes, as it slows it naturally finds a slower surface - which is at a smaller radius - thus generating the helix, naturally. So the exhaust outflow from the Tesla turbine is very slow (and low pressure, and cool, having lost the energy). You can't get enough velocity, pressure or temperature from the Tesla turbine to power another stage. - I think? - but I really am unsure now, with your suggestion.
An impulse turbine does a Momentum exchange, by turning the gas stream through 90degrees, it needs a force to turn the gas stream, reacted on the blade (like any aerofoil works?), so the reaction force turns the turbine wheel. But the gas stream still contains a lot of energy. Hence the Parson's turbine multi-stage approach?
The idea that Toymaker is using seems interesting: Useing an impulse turbine to extract "half" the energy at a lowish turbine speed, then let the remaining gas stream pass through a Tesla type array of disc-slots, to extract more energy... But I fear the impulse momentum exchange will direct the gas stream "backwards" (and inwards?) from the tips, so rotating in the wrong direction, and thus effectively extracting some energy from the discs... lowering the efficiency? Or maybe simply going in the right direction, but so slowly so as to make very little difference? I.E> after the impulse outer ring, the gas simply transits directly to the exhaust holes in the middle, without any "Tesla" style input to the rotor. But I don't know! - SO I am watching the thread to find out and learn..
Cheers!
K2
