Performance analysis of a single-piston free piston expander-linear generator with intake timing control strategy based on piston displacement

•A test rig of single-piston FPE-LG prototype is established and tested.•Intake timing control strategy based on piston displacement is presented.•Effects of intake duration and stroke length on FPE-LG performance are investigated.•The work-electric conversion efficiency is defined and analyzed. A s...

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Bibliographic Details
Published in:Applied thermal engineering 2019-04, Vol.152, p.751-761
Main Authors: Li, Jian, Zhang, Hongguang, Tian, Yaming, Hou, Xiaochen, Xu, Yonghong, Zhao, Tenglong, Wu, Yuting
Format: Article
Language:English
Subjects:
Displacement
Electric potential
Energy conversion efficiency
External pressure
Free piston expander
Generators
Intake timing control strategy
Linear generator
Load resistance
Prototypes
Pumps
Rankine cycle
Single piston
Thermal energy
Work-electric conversion efficiency
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Summary:•A test rig of single-piston FPE-LG prototype is established and tested.•Intake timing control strategy based on piston displacement is presented.•Effects of intake duration and stroke length on FPE-LG performance are investigated.•The work-electric conversion efficiency is defined and analyzed. A single-piston free piston expander-linear generator (FPE-LG) prototype for a small-scale Organic Rankine Cycle system is presented. The steady-state operation of the prototype is successfully achieved, which indicates the feasibility of single-piston FPE-LG with intake timing control strategy based on piston displacement. The effects of intake duration, intake pressure, theoretical stroke, and external load resistance (R) on operational performance and energy conversion efficiency are investigated. Results show that the piston is running at a relatively high velocity when it approaches the predetermined special displacement point (X1 or X2). The peak voltage, current, and power output increase linearly as the intake pressure and duration increase. The theoretical stroke exerts a minimal effect on peak velocity and peak voltage output but considerably affects the operating frequency. The peak power output and work-electric conversion efficiency (ηw-e) increase first and then decrease with increasing external load resistance. The peak output power and ηw-e reach the maximum value of 32.5 W and 30.8%, respectively, with an optimal R = 80 Ω. As the intake duration increases, the indicated efficiency increases gradually, whereas ηw-e shows an increasing and then decreasing trend. The optimal intake duration for reaching the maximum ηw-e is variable under different operation conditions.
ISSN:1359-4311
1873-5606
DOI:10.1016/j.applthermaleng.2019.02.121