“…Therefore, FPEG should reduce power running as much as possible and operate with regeneration only [25,26]. The switching of the Pulse-width-modulation inverter adjusts the current value of the coil, allowing the braking thrust of the linear generator to be controlled [27]. FPEG realizes arbitrary piston movement by applying a braking thrust controlled by an inverter to the piston (moving element), whose movement is not fixed by the crank.…”
A free-piston engine linear generator (FPEG) is constructed by combining a reciprocating internal combustion engine and a linear generator. FPEG is required to improve both the accuracy of the top-dead-center (TDC) positioning considering frequent combustion fluctuations and the reduction of power consumption. This paper confirms the influence of intermittent velocity control on power running suppression and TDC position deviation in a dual-cylinder FPEG. Intermittent velocity control is a simple method, which consists of repeatedly turning the speed control on and off. The experimental results of the glow engine indicate that this control suppresses power consumption and enables continuous combustion. The setting range for intermittent speed control, which continues operation only through regenerative operation, must be determined by considering the gain value. In addition, this paper explains the effects of the control range of intermittent velocity control on power generation efficiency, piston motion frequency, and TDC position deviation in the dual-cylinder FPEG. Increasing the range ratio of intermittent speed control improves power generation efficiency, but it also increases the standard deviation of TDC position.INDEX TERMS Free-piston engine, linear generator, generation control, speed control, and top-deadcenter
“…Therefore, FPEG should reduce power running as much as possible and operate with regeneration only [25,26]. The switching of the Pulse-width-modulation inverter adjusts the current value of the coil, allowing the braking thrust of the linear generator to be controlled [27]. FPEG realizes arbitrary piston movement by applying a braking thrust controlled by an inverter to the piston (moving element), whose movement is not fixed by the crank.…”
A free-piston engine linear generator (FPEG) is constructed by combining a reciprocating internal combustion engine and a linear generator. FPEG is required to improve both the accuracy of the top-dead-center (TDC) positioning considering frequent combustion fluctuations and the reduction of power consumption. This paper confirms the influence of intermittent velocity control on power running suppression and TDC position deviation in a dual-cylinder FPEG. Intermittent velocity control is a simple method, which consists of repeatedly turning the speed control on and off. The experimental results of the glow engine indicate that this control suppresses power consumption and enables continuous combustion. The setting range for intermittent speed control, which continues operation only through regenerative operation, must be determined by considering the gain value. In addition, this paper explains the effects of the control range of intermittent velocity control on power generation efficiency, piston motion frequency, and TDC position deviation in the dual-cylinder FPEG. Increasing the range ratio of intermittent speed control improves power generation efficiency, but it also increases the standard deviation of TDC position.INDEX TERMS Free-piston engine, linear generator, generation control, speed control, and top-deadcenter
“…The position-tracking method is preferred in estimating the TDC for other FP-LEG control applications. 135,136 Some opposed-piston FP-LEGs use an external high-pressure gas source to drive the piston and achieve the target CR in one stroke. 45 To avoid using supercharging equipment during the starting process, which could be complex.…”
Section: Starting Process Controlmentioning
confidence: 99%
“…The position-tracking method is preferred in estimating the TDC for other FP-LEG control applications. 135,136…”
Section: Control Strategies Of Fp-leg Systemsmentioning
confidence: 99%
“…Wu et al 146 used the trajectory tracking control method to minimise cyclic fluctuation and maintain the system’s stable operation and operational targets. Vu and Lim, 136 investigated the predictive-fuzzy logic (PFL) control, and the results indicated that it is a more effective control strategy. It improves the engine performance compared to the PID in settling time, target TDC error, and cycle-to-cycle variation.…”
Section: Control Strategies Of Fp-leg Systemsmentioning
Linear engines, or widely called free piston engines, have their advantages compared to conventional engines with crankshafts, for example, lower friction loss, compact structure, fuel adaptability, flexible compression ratio, etc. Among the linear engine conceptual designs and prototypes, Linear Engine Generator (LEG) incorporating a linear engine (internal or external combustion) and a linear alternator provides an alternative and attractive solution for hybrid electrical powertrains in transport applications. Due to the advantages of linear engines, hydrogen, synthetic hydrogen carrier fuels and biofuels are easier to adopt on LEG, making it an appealing technology for decarbonisation. This paper explicitly reviews LEG research and development on state-of-art solutions and recent progress in linear engine improvement, linear alternator design optimisation, and integrated LEG system control. Key performance indicators of the linear engine generator, like power output, thermal and electrical efficiency, etc., are summarised to present a general picture of up-to-date LEG development. Recommendations for further LEG development are provided at the end of the paper regarding the review outcomes.
“…The piston assembly is mainly affected by gas pressure F p in both cylinders, gas pressure F s in scavenging chamber, electromagnetic force F e , and friction force F f . These forces are transmitted in the direction of piston motion 26–28 and are coupled with time-varying piston motion. Consequently, the piston forces during transmission are shown in Figure 3:Figure 3.Force diagram of piston assembly.…”
The free-piston hybrid power system (FPHS) is affected by the dynamic coupling of combustion drive, power transmission, piston motion, excitation generation and gas exchange, and its operating state is very different from that of traditional engines. In this paper, the influence of the change of electromagnetic load on the ventilation stability of the whole system is studied by combining the method of system simulation and experimental validation. A dynamic-ventilation one-dimensional coupled gas exchange model was established, and the influence of the fluctuation of the electromagnetic load on the gas exchange is simulated by combining the thermodynamic model with the magnetic inductive load model. The results show that the scavenging efficiency is positively correlated with the load fluctuation, while the trapping efficiency changes with the opposite rule. Specifically, increasing the electromagnetic load properly will increase the time of gas exchange and obtain more fresh charge. The reduction of the electromagnetic load will make the compression process have higher gas pressure and temperature, which the mixture of oil and gas is more homogeneous and the combustion rate is faster after ignition. The stability of the ventilation performance of FPHS is very sensitive to electromagnetic fluctuations. The control of FPHS system can be achieved by adjusting the electromagnetic load.
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