Effect of key parameter on the energy consumption and start-up time in the cold start-up process of an opposed-piston free-piston linear generator

Abstract

The opposed-piston free-piston linear generator exhibits considerable energy conversion efficiency; however, its operational dynamics are highly sensitive to key parameters owing to the elimination of mechanical limitations. In the present study, an analysis was conducted on the impact of significant system variables on the operating performance of the cold start-up process in conjunction with energy decomposition. At the same time, the operational boundaries of the cold start-up process were explored. A comprehensive thermodynamic model with a cold start-up process was established to predict the operation characteristics. The established model was verified through experimental data obtained from the stable operation of a prototype. The error between simulated cylinder pressure values and experimental observations was determined to be below 1 bar. The findings indicate that as the motor force and bounce energy ratio increased, there was a corresponding reduction in both the time and total energy input necessary to accomplish the cold start-up process. To achieve lightweighting and simultaneously reduce electrical energy consumption, it is advisable to decrease the piston mass by no more than 30 %. A comprehensive energy decomposition study revealed that friction loss accounted for the majority of total energy consumption. To optimize the cold start-up process of the opposed-piston free-piston linear generator, the motor force should be between 300 and 400 N, the bounce energy ratio between 9 and 11, and the piston assembly mass optimization range between −15 % and 15 %.