Free-Piston Engines: Recent Trends and Novel Designs

Dear Colleagues,

For many years, researchers have presented the potential of free-piston engines to increase efficiency, decrease emissions, run on multifuel, and offer compact architectures.  Unlike conventional rotary engines, linear engine piston motion is not prescribed by the crankshaft, and no crankcase is needed. Furthermore, the elimination of the canted piston connecting the rod to the crankshaft reduces piston ring and skirt friction losses.  The linear engine compression ratio is changeable and variable. This can enable advanced combustion regimes such as homogeneous charge compression ignition HCCI over a broad operating space. HCCI operates on lean mixtures and lower temperatures than spark-based ignition and diesel engines. Moreover, other types of heat engines, such as Stirling engines, can utilize the linear arrangement for more efficient operation. Linear engines also enable the direct activation of loads, such as compressors, pumps, or linear electrical generators.

The evolution of sensor and control technologies made the actual operation of free-piston engines possible. About 30 years ago, my group demonstrated a free-piston engine/generator with two back-to-back reciprocating pistons and generated 320 Watts of electricity at the system operating frequency.

Since then, there has been a considerable amount of research into this area. This Special Issue will be devoted to the latest research and development of free-piston engines, which are more widely applicable in this age of the solid-state manipulation of frequency and waveform. We seek submissions related to the design, development, analysis, and modeling of such free-piston engines.

Prof. Dr. Parviz Famouri
Guest Editor

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• free-piston
• linear engines
• linear generators