Automotive Use
A turbocharged engine is sometimes considered to be a combined cycle engine with the turbocharger extracting extra energy from the exhaust gases. However, the efficiency gain of such a design has more to do with extracting more power from a smaller and lighter engine (thereby improving efficiency as measured by the distance travelled by the vehicle per unit volume of fuel) than it does the actual thermal efficiency of the engine (work done per unit input energy).
On large marine diesels turbo-compounding has been employed where the turbocharger physically pushes the engine around via some sort of gearing arrangement.
Combined cycles have traditionally only been used in large power plants. BMW, however, has proposed that automobiles use exhaust heat to drive steam turbines. This can even be connected to the car or truck's cooling system to save space and weight, but also to provide a condenser in the same location as the radiator and preheating of the water using heat from the engine block. However, stirling engines can also be used if light weight is a priority (as in a sports car or racing application), because they use a gas such as air rather than water as the working fluid.
It may be possible to use the pistons in a reciprocating engine for both combustion and steam expansion as in the Crower engine.
Read more about this topic: Combined Cycle