Free Piston Engine The Free Piston Engine is a combination of reciprocating engine and rotary turbine. It is called free piston engine because the freedom motion for Mechanical linkage which gives variable stroke according to load. ADVANTAGES 1. Mechanical simplicity 2. Less power to weight ratio 3. Lower turbine operating tempeatures 4. Multi fuel capability 5. Flexibility and reliability 6. Easy starting and control LIMITATIONS 1. Poor fuel economic 2. Less stability 3. Poor part load efficiency 4. High combustine rates 5. Reduction gearing APPLICATIONS 1. Free piston engines are widely used as submarine air compressor units 2. These engines are suitable for power generation in medium power range 3. Free piston engine have been tride in ship propulsion, road and rail traction and even in aircrafts. 4. It is used in mixed gas steam cycle