I thought we were talking about STEAM turbines - how does "I don't see any piston engines on commercial airliner" have to do with anything???
And I agreed with you- that in a tight band of constraints a very large steam turbine will be more efficient but only if you stay within those constraints.
I have 12 ICE's because - I heat my house with wood, I have a large garden, I have back up power generation, and I run a small furniture business. And I love everything about all of it except buying fossil fuels.
To get information look for information - call or visit Cyclone - but do yourself a favor and read up a little first.