Most practical heat engines are based on ideal cycles whose processes are different from the Carnot cycle (eg; constant pressure or constant volume heat addition instead of isothermal). I understand that achieving the controlled isothermal processes required by the Carnot is impractical. However, are there any real heat engines use the Carnot cycle as their basis? I'm looking to understand any implementations that do exist and why they fall short of more typically used cycles. (I do know of Stirling and Ericsson engines which are based on equally efficient cycles, but these suffer from low specific power?) Any links to papers or other resources would be much appreciated!
Alternatively, more info on why heat engines are never/rarely based on these 'optimal' cycles would be useful too! It seems counterintuitive to me that, when irreversibilities are taken into account, the efficiency of a 'less optimal' cycle would exceed that of any engine based on an 'optimum'/Carnot one