Free-piston engines

The free-piston engine is an old concept which was in use in the period 1930-1960 in a variety of applications. The earliest commercially successful free-piston engines served as air compressors in German naval vessels, where they provided advantages of compactness, high fuel efficiency, and low noise and vibrations compared with conventional technologies. With the success of the free-piston air compressor, such engines were subsequently used as gas generators, producing hot gas for driving a turbine.

In addition to simplicity and low frictional losses, the free-piston engine provided attractive features such as fuel flexibility and the possibility of high-pressure operation. However, as conventional gas turbine and internal combustion engine technology advanced, the interest in the free-piston engine concept dropped and the concept was abandoned around 1960.

Recently, there has been a significant renewed interest in the free-piston engine concept. With the availability of modern, microprocessor-based control technology, numerous research groups worldwide seek to exploit the flexibility, compactness, and efficiency advantages offered by this concept.


The Sir Joseph Swan Institute of Energy Research have studied several free-piston engine configurations for highly efficient power generation in various applications:

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