Identification and analysis on the variation sources of a dual-cylinder free piston engine generator and their influence on system operating characteristics. (1st March 2022)

• Record Type: Journal Article
• Authors: Zhang, Zhiyuan; Feng, Huihua; Jia, Boru; Zuo, Zhengxing; Yan, Xiaodong; Smallbone, Andrew; Roskilly, Anthony Paul
• Is Part Of: Energy. Volume 242(2022)
• Publication Date: 2022-03-01
• Subjects: Free piston engine generator -- Cyclic variation -- Cylinder-to-cylinder variation -- Stable operation -- Performance stability -- Thermal efficiency; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2021.123001
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: Stable combustion is a huge challenge for dual-cylinder free-piston engine generator (FPEG). Combustion variations are easy to occur, because the piston movement is only affected by the forces acting on the moving parts, and there is no mechanical structure limit. This paper has investigated the sources of cyclic and cylinder-to-cylinder variations for dual-cylinder FPEGs, and further analysed their effect on the piston movement characteristics in operation and engine's performance by using an established working model. This study reveals that FPEG has specific anti-interference properties but is easily affected by external conditions and operating parameters. The operation of the FPEG system should be limited to a specific range rather than fixed at a fixed compression ratio like a traditional internal combustion engine. The simulation results showed that the FPEG system returns to a stable operating state within just a few cycles for one-time combustion variations if there are no misfires, regardless of whether they occur in one cylinder or two cylinders. The operating centre deviates from the geometric centre when continuous variations occur in just one cylinder. The compression ratios and operating frequency decrease when combustion variations occur, but the compression ratio decreases significantly in normal cylinders. When continuous variations occur in two cylinders, the compression ratio, operating frequency, and free-piston engine performance are significantly reduced. Highlights: Variation sources of a dual-cylinder FPEG are identified and analysed. The anti-disturbance characteristics of FPEG system is presented. Misfire is very harmful to the stable operation of the system. System performance stability has higher requirements for control parameters. Compression ratios running at 8–10 are recommended, rather than running at a fixed value.