China
Africa
Explore chapters and articles related to this topic
Overview, Background, and History
Published in John B. Heywood, Eran Sher, The Two-Stroke Cycle Engine, 2017
The free-piston engine is a combined engine and compressor unit whose power piston is directly connected to the compressor piston without any intermediate crankshaft and connecting rod linkage. The free-piston engine may be used either as a compressed air supplier for external use (the free-piston air compressor) or as a gas generator that supplies hot gas at high pressure (the free-piston gasifìer). In the latter, the air supply to the engine must be supercharged to maintain the receiver pressure upstream of the gas user. The essential features of a basic unit are illustrated in Fig. 1-8. The cylinder consists of three parts: the power, the compressor, and the bounce compartments. The piston oscillates between its bottom center (BC) and top center (TC) positions, controlling the scavenge and exhaust ports of the power cylinder as it does so. The operating cycle the working fluid follows is either an SI or a Cl two-stroke cycle. When the piston travels downward toward BC, fresh air from the atmosphere enters into the compressor through the inlet valve while the contents of the bounce cylinder are compressed. When the piston travels upward toward TC, the fresh air is compressed and then delivered to the receiver through the exit valve. During this period, the piston is driven by the high pressure in the bounce cylinder, which effectively acts like a flywheel, absorbing energy from the piston on the downward stroke and returning it on the upward stroke.
Multi Cycle Modeling, Simulating and Controlling of a Free Piston Engine with Electrical Generator under HCCI Combustion Conditions
Published in Combustion Science and Technology, 2020
Mohammad Alrbai, Matthew Robinson, Nigel Clark
For each of these applications, conventional slider-crank spark and compression ignition engines have been used for decades, though many limitations and challenges affect their performance. As one of the alternatives, the free piston engine has been introduced as a simpler and potentially more efficient device to convert fuel energy to electrical power in many applications. The fact that the free piston engine lacks crankshaft components and a valve train leads to lower mechanical energy losses compared to conventional engines. Also, its flexibility to support various fuels and combustion regimes has gained the interest of many researchers (Prados 2002). The absence of the crankshaft in the engine allows the compression ratio to vary from cycle to cycle and leads to engine dynamics and performance which varies significantly from conventional engines (Shaver 2005). On the other hand, more requirements for engine control must be met to ensure stable performance (Prados 2002; Shaver 2005).