Comparative analysis on friction characteristics between free-piston engine generator and traditional crankshaft engine

Li, Jian; Zuo, Zhengxing; Jia, Boru; Feng, Huihua; Wei, Yidi; Zhang, Zhiyuan; Smallbone, Andrew; Roskilly, Anthony Paul

doi:10.1016/j.enconman.2021.114630

Cited by 26 publications

(10 citation statements)

References 38 publications

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“…FPEGs do not use a bearing due to their relatively simple structure [11]. Therefore, the friction force F r is calculated as…”

Section: Basic Structure and Energy Flow Of The Fpegmentioning

confidence: 99%

“…The friction force on the engine F r_en generated by the piston rings was calculated as the product of the friction coefficient of the piston rings and the vertical drag force [11,24]. The friction force on the linear machine F r_lin was assumed to be 15 N [11].…”

Section: Basic Structure and Energy Flow Of The Fpegmentioning

confidence: 99%

“…As a result, the compression ratio (CR) can be changed to accommodate a variety of fuels, including hydrogen, which is a zero-carbon alternative fuel [8][9][10]. In addition, FPEGs have advantages such as reduced frictional loss because they have no crank mechanism [11,12] and improved thermal efficiency by varying the piston motion [13][14][15]. However, controlling the piston motion between the top dead center (TDC) and the bottom dead center (BDC) is difficult because FPEGs have no mechanical limits.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Nonlinear Spring Characteristics on the Efficiency of Free-Piston Engine Generator

et al. 2022

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Piston motion is an important factor in improving the energy conversion efficiency of free-piston engine generators (FPEGs), and an air cylinder is an important component affecting piston motion. In this study, the effect of the air cylinder specifications on the piston drive frequency and energy conversion efficiency is clarified. By considering that the repulsion force of an air cylinder is nonlinear, the main factors that change the piston drive frequency were investigated by simulation. In addition, a piston drive frequency diagram was drawn based on the top surface area of the air cylinder and the compression ratio to discuss the effect of the air cylinder specifications on the piston drive frequency. The results indicate that the air cylinder specifications affect the piston drive frequency and generation force of a linear machine. Moreover, the structure of the air cylinder and the constraints on the maximum generation force of the linear machine narrow the possible operating range in the piston drive frequency. The air cylinder specifications based on the piston drive frequency diagram improved the FPEG energy conversion efficiency by 0.5%.

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“…FPEGs do not use a bearing due to their relatively simple structure [11]. Therefore, the friction force F r is calculated as…”

Section: Basic Structure and Energy Flow Of The Fpegmentioning

confidence: 99%

Section: Basic Structure and Energy Flow Of The Fpegmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Nonlinear Spring Characteristics on the Efficiency of Free-Piston Engine Generator

et al. 2022

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“…The FPE was developed from the motor compressor apparatus proposed by the authors of [20], which eliminated the crank linkage mechanism of the reciprocating piston expander, allowing the piston to move freely within the cylinder. These features give it the advantages of compact structure, good sealability, low friction, high efficiency, and variable expansion ratio [21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Performance Prediction and Optimization of Single-Piston Free Piston Expander-Linear Generator Based on Machine Learning and Genetic Algorithm

Li,

Zuo,

Jia

et al. 2024

International Journal of Energy Research

Self Cite

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This paper proposed a single-piston free piston expander-linear generator (SFPE-LG) prototype applied to organic Rankine cycle systems. Two valve timing control strategies, namely, time control strategy (TCS) and position control strategy (PCS), were developed. Based on the experimental data, a back propagation neural network (BPNN) prediction model was established. The effects of structural parameters such as neural network layers, transfer function, training function, hidden layer nodes, and learning rate on the prediction accuracy of this BPNN model were discussed. The training and prediction accuracy of the BPNN model was verified using 5-fold cross-validation and Wilcoxon signed-rank test. Moreover, the BPNN model was integrated with a genetic algorithm to predict and optimize the maximum output power of the SFPE-LG. The results showed that the BPNN model used to predict the motion characteristics and output performance of the SFPE-LG exhibits strong learning ability and high prediction accuracy. Notably, the prediction accuracy of the BPNN model is significantly higher under the PCS compared to TCS. The effect of hidden layer nodes on mean square error (MSE) and correlation coefficient (R) is greater than that of the learning rate. When the number of hidden layer nodes exceeds 30, the BPNN model consistently achieves low MSE and high R. The optimization results showed that the SFPE-LG can obtain a maximum output power of 141.69 W under the TCS, when the working parameters are inlet pressure of 0.7 MPa, intake duration of 35 ms, load resistance of 67 Ω, and expansion duration of 104 ms, respectively.

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“…The friction power of piston ring increases along with the growth of lubricating oil temperature and operating frequency, while decreases with the growth of lubricating oil viscosity. 14 Li et al studied the effect of external resistance load and equivalent ratio on the performance of FPEG. It was found that the Top Dead Center (TDC) was susceptible to external loads and other parameters.…”

Section: Introductionmentioning

confidence: 99%

Simulation investigates on operation characteristics of free piston internal combustion generator

Yubo,

Yuchun,

Haishu

et al. 2023

Advances in Mechanical Engineering

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To study the influence of the free piston generator structure on its stable operation, this paper chose the combining mathematical and physical methods to build a simulation model to investigate the influence factors. According to the dynamic and thermodynamic equation, the mathematical model of the free piston internal combustion generator system was established. the simulation model was built with the help of MATLAB/Simulink software, and the validity of the model was verified. Based on this, the influences of ignition position and piston group mass on the operation characteristics of free piston generator were investigated. The simulation results show that the factors such as ignition position, piston group mass have significant effects on the compression ratio, cylinder pressure, maximum acceleration, etc. of the free piston generator, which provides a theoretical basis for the stable operation control of the free piston internal combustion generator.

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Comparative analysis on friction characteristics between free-piston engine generator and traditional crankshaft engine

Cited by 26 publications

References 38 publications

Effect of Nonlinear Spring Characteristics on the Efficiency of Free-Piston Engine Generator

Effect of Nonlinear Spring Characteristics on the Efficiency of Free-Piston Engine Generator

Performance Prediction and Optimization of Single-Piston Free Piston Expander-Linear Generator Based on Machine Learning and Genetic Algorithm

Simulation investigates on operation characteristics of free piston internal combustion generator

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