Free Piston Engine - Advantages and Disadvantages

What is Free Piston Engine?

A free-piston engine is a type of internal combustion engine where the pistons are not connected to any crankshaft, but rather each piston has its own crankshaft.

This configuration allows for more power from a smaller displacement or weight than an equivalent reciprocating piston engine. 

Advantages and Disadvantages of Free piston engine:

Advantages of a Free Piston Engine:

1. Low weight and high efficiency. 
2. It is more flexible and reliable.
3. It required less maintenance.
4. It is easy to manufacture.
5. The power to weight ratio is high.
6. It generates extremely low vibration because there are no working parts in contact with each other.
7. The lack of any rotary elements (such as a crankshaft) makes it fast to start and stop. 
8. Materials for a free-piston engine are simpler and cheaper than those of a conventional mechanically-driven automotive engine.
9. An engine motivated by a single-piston can be as much as 3x lighter than an equivalent multi-piston diesel engine, which reduces fuel consumption and vehicle weight for the same power output. Consuming less fuel efficacy is good for the environment and also saves you money on gas at the pump! Fewer vehicles on the road equal less air pollution.
10. Free piston engines operate on resources less expensive than fossil fuels, such as electricity or compressed air.
11. They can also utilize biofuels more efficiently by delivering peak torque at low rpm due to the operating fluid being constantly used by all pistons simultaneously. This also minimizes pumping losses from having to move fuel from an outer container into the cylinder during each stroke. 
12. The torque produced by a free-piston engine can be adjusted by varying the driver's position on the machine. This makes a free-piston engine a very light and mobile device that is easy to fix or even use as a portable power generator. 
13. Unlike previous models, the piston is not directly connected to the output shaft, instead, it pushes on an airtight skirt between it and the cylinder wall. 
14. Because there are no phases of compression or power strokes, gases expand uniformly through a 360° circle on each rotation of the crank which boosts efficiency. 
15. There is no reciprocating source of vibration or torsional load nor sudden shocks transmitted from one end to another as in an ordinary engine so abrupt changes in speed can be tolerated without excessive stress either internally or externally. 

Disadvantages of a Free Piston Engine:

1. It has low stability.
2. Less fuel efficiency.
3. It is not good at part-load efficiency.
4. It is unsuitable for hauling heavy loads over long distances or powering a machine tool factory of daily public transportation services. 
5. A disadvantage of this machine is that it cannot sustain itself perpetually as external forces must take over from time to time to adjust where the load travels. In essence, this limits its overall efficiency (most engines require constant energy input). 
6. These engines produce more noise than most other types of reciprocating engines do. 

Free Piston Stirling Engine GIF | Gfycat