Theoretical and experimental investigation into the required minimum starting force for a linear engine–linear generator integrated system

In this paper the starting process of the linear engine–linear generator integrated system is described, and the required minimum starting force for the linear engine–linear generator integrated system, both with persistent oscillations and also considering the number of starting strokes based on the principle of single-degree-of-freedom damped forced vibrations, is theoretically analysed. The theoretical expression for the required minimum starting force is obtained, as well as the relationship between the minimum starting force and the structural parameters. Bench tests are also conducted to validate the theory. The results show that the required minimum starting force that satisfies persistent oscillations is related to the cylinder bore, the displacement, the moving mass and the friction coefficient. When considering the number of starting strokes, the required minimum starting force is related to the number of starting strokes, the compression energy, the displacement, the moving mass and the friction coefficient. When the number of starting strokes is designated as four, this satisfies the formation of a combustible mixture; the minimum starting force is slightly larger than the value that satisfies persistent oscillations. The consistency between the test results and the theoretical calculations indicates that the theoretical model of the minimum starting force has a certain reference value for the design of a linear engine–linear generator integrated system.