No, that's interesting, but that's not it. I was thinking of how turbofans have at least 3 sets of moving blades: the fan, the compressor, and the turbine. The turbine blades are behind the combustion chambers and they are pushed by the thrusting exhaust in order to power the fan at the front of the engine. (https://en.wikipedia.org/wiki/Turbofan)
The general theory behind this is called the Brayton Cycle (https://en.wikipedia.org/wiki/Brayton_cycle), and you can see if you read about it that they are all some form of blowing on your own sails, it's a basic design principle that increases the engine efficiency by capturing some of the output. And it still seems to defy intuition to me, I find it hard to understand how reducing the output and putting it back through something that is less than 100% efficient can end up saving energy or increasing output... it's counter-intuitive.
Anyway, I wonder if installing a fan on your sailboat technically makes it a Brayton Cycle engine... mmm maybe not since the sail doesn't power the fan...
The general theory behind this is called the Brayton Cycle (https://en.wikipedia.org/wiki/Brayton_cycle), and you can see if you read about it that they are all some form of blowing on your own sails, it's a basic design principle that increases the engine efficiency by capturing some of the output. And it still seems to defy intuition to me, I find it hard to understand how reducing the output and putting it back through something that is less than 100% efficient can end up saving energy or increasing output... it's counter-intuitive.
Anyway, I wonder if installing a fan on your sailboat technically makes it a Brayton Cycle engine... mmm maybe not since the sail doesn't power the fan...