A free-piston engine is a linear crank less internal combustion engine.
Combination of a reciprocating engine and a rotary turbine.
It consists of a gasifier and a turbine. Compressor piston are directly attached to diesel piston.
The piston is free because its motion is not controlled by the position of a rotating crankshaft Hence, It is called a free piston engine.
Important features of the free-piston engine are potential reductions in frictional losses.
Operating principle :
The free-piston engine is restricted to the two-stroke operating principle, as a power stroke is required on every cycle. Although two-stroke engines suffer from poorer performance compared to four strokes, this performance gap is declining and recent years have seen an increased interest in small scale two-stroke engines.
Important steps in this direction are :
Combination of a reciprocating engine and a rotary turbine.
It consists of a gasifier and a turbine. Compressor piston are directly attached to diesel piston.
The piston is free because its motion is not controlled by the position of a rotating crankshaft Hence, It is called a free piston engine.
Important features of the free-piston engine are potential reductions in frictional losses.
Operating principle :
The free-piston engine is restricted to the two-stroke operating principle, as a power stroke is required on every cycle. Although two-stroke engines suffer from poorer performance compared to four strokes, this performance gap is declining and recent years have seen an increased interest in small scale two-stroke engines.
Important steps in this direction are :
- Improvements in the fuel properties
- Component design changes for higher efficiency
- Lower cost and weight
- Higher part load efficiency
- Possible multi-fuel operation
- Reduced frictional loss
- Simple design
- few moving parts
- variable compression ratio
Free piston engine are usually divided into three categories :
- Single Piston
- Dual Piston
- Opposed Piston
Advantages of free-piston engine :
- Mechanical simplicity
- Flexibility and reliability
- Power to weight ratio
- Multi fuel capability
- Low turbine operating temperature
- Less vibration and noise
- Less maintenance
- Easy to start piston
- Highly suitable for waste heat recovery
- Give high degree of maneuverability
- Less manufacturing cost
Disadvantages of free-piston engine :
- Poor fuel economy
- Stability of fuel supply
- Poor part load efficiency
- High combustion rate
- Reduction gearing is require
Application of free-piston engine :
- Submarine air compressor units
- Suitable power generation
- Ship propulsion
- Road and rail traction
- Aircraft
- High speed centrifugal air compressor
- Mixed gas-steam cycle
- For pumping oil
- Free-piston gas generators
- Hydraulic free-piston engines