Hi jh5speed,
Thanks for the tips and advice which I've passed on to the N.T. kitchen turbine department.
Apparently they have tried using a compressor (mechanical bellows of soft leather nailed between flat wooden plates) which increases the kinetics and raised the combustion temperature. The more energetic exhaust flue gas turned the turbine more quickly.
It seems to be a win win situation, but the bellows operator is demanding extra pay because of the increase in thermal efficiency. They are now working on a mechanically driven set of bellows from the extra power from their turbine.
They want to know if it is worth adding a second turbine, downstream of the first to work the bellows?
They are grateful for the advise on the turbine wash and suitable gearbox lubrication.