Dear Merriman,
The Ljungstrom radial turbine concept dates back to 1908 when it was invented by Birger and Fredrick Lungstrom, a pair of brothers who patented dozens of industrial devices including bicycles and steam turbines. Ljubgstrom’s first turbines were steam-powered with radial turbines and were mainly used to generate electricity. After a few years, Ljungstrom replaced them with more efficient axial flow turbines.
As recently as 2013 and 2014 counter-rotating, radial turbines were proposed for a light helicopter with co-axial rotors.
Sherpa flew a 1/5 scale model of its Sagita light helicopter with an internal combustion engine and air compressor behind the cockpit. That hot air (100 degrees Celcius) blows up - inside the main rotor mast - and escapes between a pair of radial turbines. The radial turbine is make of two discs with concentric circles of blades pointing up or down. Escaping air blows past these concentric circles of blades imparting rotational energy to the two discs. Since blades on the top disc are curved opposite to blades on the bottom disc, they try to counter-rotate. The top rotor is bolted to one radial turbine while the bottom rotor is bolted to the other radial turbine. ... sort of like WW1-vintage rotary engines.
Inventor Hubert Antoine claims that their new turbine is more efficient than conventional geared transmissions because hot air is doing all the hard work, with fewer moving parts.
When seen from above, radial turbine blades look similar to blades in axial flow turbines, but they are constant chord.
Unfortunately we have not heard anything from this Belgian start-up company since 2014.
Were they able to raise enough money to continue development?