A Comprehensive Review of the Free Piston Engine Generator and Its Control

Brosnan, Patrick; Tian, Gui Yun; Montanaro, Umberto; Cockerill, Sam

doi:10.53941/ijamm0201006

Cited by 4 publications

(1 citation statement)

References 103 publications

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“…As for the rebound force from the rebound device, the single-cylinder/single-piston structure type of the FPELG rebound force mainly consists of the rebound force from the mechanical spring or the gas spring. The rebound force from the mechanical spring is described according to Hooke's law, which does not take the mass or damping of the mechanical spring into account [41]. Similarly, the rebound force from the gas spring is described according to the ideal gas equation of state [42].…”

Section: Numerical Modelsmentioning

confidence: 99%

Research on Piston Dynamics and Engine Performances of a Free-Piston Engine Linear Generator Coupling with Various Rebound Devices

Guo,

Wang,

Tong

et al. 2023

Energies

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Free-piston engine linear generators (FPELGs) are an innovative linear power device that exhibits the distinctive dynamics of pistons and performance of free-piston engines. Furthermore, the single-cylinder/single-piston FPELG structure type has more advantages than other FPELG structure types, including a straightforward structure and ease of control. However, when coupled with various rebound devices, the operational characteristics and piston and engine performance of single-cylinder/single-piston FPELGs are quite different. Therefore, this paper aims to quantitatively compare the dynamics of the piston and engine performance of single-cylinder/single-piston FPELGs coupled with various types of rebound device. The results indicate that when the equivalent stiffness of the gas spring is greater than that of the mechanical spring, the operating frequency of the piston of the FPELG coupled with a gas spring will be higher than that when coupled with a mechanical spring. During the compression stroke, the piston velocity of a FPELG coupled with a mechanical spring changes linearly, while the piston velocity of a FPELG coupled with a gas spring changes nonlinearly. FPELGs coupled with gas springs have shorter compression and expansion durations compared to those coupled with mechanical springs. In addition, the indicated powers of FPELGs coupled with ideal gas springs and mechanical springs are 1.5 kW and 1.3 kW, respectively. However, due to leakage, the thermal efficiency of a FPELG coupled with an actual gas spring is reduced by approximately 2.5% compared with the FPELG coupled with the ideal gas spring. Furthermore, the operation frequency of the piston is positively correlated with the stiffness of the mechanical spring. In addition, as the stiffness of the mechanical spring increases, the combustion process of the engine becomes close to an isovolumetric process. The changes in piston dynamics and engine performance when increasing the initial gas pressure of the gas spring are similar to those when increasing the stiffness of the mechanical spring.

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Section: Numerical Modelsmentioning

confidence: 99%