Effect of Nonlinear Spring Characteristics on the Efficiency of Free-Piston Engine Generator

Shoma Irie (), Mitsuhide Sato (), Tsutomu Mizuno, Fumiya Nishimura and Kaname Naganuma
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Shoma Irie: Faculty of Engineering, Shinshu University, Nagano 380-8553, Japan
Mitsuhide Sato: Faculty of Engineering, Shinshu University, Nagano 380-8553, Japan
Tsutomu Mizuno: Faculty of Engineering, Shinshu University, Nagano 380-8553, Japan
Fumiya Nishimura: Department of Mechanical Engineering, College of Engineering, Kanazawa Institute of Technology, Nonoichi 921-8501, Japan
Kaname Naganuma: Department of Mechanical Engineering, College of Engineering, Kanazawa Institute of Technology, Nonoichi 921-8501, Japan

Energies, 2022, vol. 15, issue 20, 1-17

Abstract: Piston motion is an important factor in improving the energy conversion efficiency of free-piston engine generators (FPEGs), and an air cylinder is an important component affecting piston motion. In this study, the effect of the air cylinder specifications on the piston drive frequency and energy conversion efficiency is clarified. By considering that the repulsion force of an air cylinder is nonlinear, the main factors that change the piston drive frequency were investigated by simulation. In addition, a piston drive frequency diagram was drawn based on the top surface area of the air cylinder and the compression ratio to discuss the effect of the air cylinder specifications on the piston drive frequency. The results indicate that the air cylinder specifications affect the piston drive frequency and generation force of a linear machine. Moreover, the structure of the air cylinder and the constraints on the maximum generation force of the linear machine narrow the possible operating range in the piston drive frequency. The air cylinder specifications based on the piston drive frequency diagram improved the FPEG energy conversion efficiency by 0.5%.

Keywords: linear generator; free-piston engine; air cylinder; nonlinear spring; piston drive frequency; generation control (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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