Research on the Operating Characteristics of Hydraulic Free-Piston Engines: A Systematic Review and Meta-Analysis

The hydraulic free-piston engine (HFPE) is a kind of hybrid-powered machine which combines the reciprocating piston-type internal combustion and plunger pump as whole. In recent years, HFPE has been investigated by number research groups worldwide due to its potential advantages high efficiency, energy savings, reduced emissions multi-fuel operation. Therefore, our study aimed assess operating characteristics, core questions progress HFPEs via systematic review meta-analysis. We included operational control, starting misfire in-cylinder working processes stability. conducted literature search using electronic databases. on mainly concentrated four kinds engine, according piston arrangement form: single piston, dual pistons, opposed pistons four-cylinder complex configuration. in China Zhejiang University, Tianjin Jilin University Beijing Institute Technology. addition, China, focused process while free considering machinery dynamics. Regarding future research, it very important that we solve instabilities brought about chance fluctuations process, will involve system’s cyclical variation, method predicting instability recovery after instability.