Thermodynamic Simulation and Prototype Testing of a Four-Stroke Free-Piston Engine

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Jiming Lin ◽  
Zhaoping Xu ◽  
Siqin Chang ◽  
Ningxia Yin ◽  
Hao Yan
Keyword(s):  
Thermodynamic Simulation ◽  
Thermodynamic Cycle ◽  
Energy Conversion Efficiency ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine ◽  
Simulation And Experiment ◽  
Intake Stroke ◽  
Engine System ◽  
Insight Into

In order to achieve higher-energy conversion efficiency, a free-piston engine with an improved four-stroke thermodynamic cycle is investigated in this paper. This cycle is optimized according to the variable strokes feature and is characterized by the short intake stroke, the complete expansion stroke, the external pressurization, and the intercooling. The development of a four-stroke free-piston engine system simulation model was described, and the effects of the cycle on the system performances were qualitatively analyzed. According to the experiment of the prototype, the generating efficiency of 33.4% can be achieved when the system is fueled with gasoline and the output power is significantly increased from 1.62 to 2.68 kW. The simulation and experiment results are analyzed in detail, giving insight into the performances of the system. Studies show that the energy-saving and environmental protection performances of the system can be significantly promoted by using the improved thermodynamic cycle.

Friction characteristics of piston rings in a free-piston engine generator

2016 ◽  
Vol 18 (9) ◽  
pp. 871-885 ◽  
Author(s):  
Chenheng Yuan ◽  
Jing Xu ◽  
Huihua Feng ◽  
Yituan He
Keyword(s):  
Friction Model ◽  
Piston Engine ◽  
Piston Rings ◽  
Coupled Models ◽  
Free Piston ◽  
Friction Characteristics ◽  
Friction Power ◽  
Reciprocating Engine ◽  
Free Piston Engine ◽  
Insight Into

Free-piston engine generator is a new alternative to traditional reciprocating engine, which moves without mechanical restriction of crankshaft system. This article investigated numerically the friction characteristics of piston rings in a free-piston diesel engine generator by adopting coupled models of dynamic and friction. The development of the dynamic model and friction model was described, and an iterative calculation method was presented, giving insight into the coupled parameters of these two models. The detailed effects of the dynamic on friction and lubrication were investigated compared with a corresponding traditional crank engine. The friction characteristics of the free-piston engine generator were found to differ clearly from those of the traditional engine due to its special piston motion. Compared with the traditional engine, the minimum lubricant film thickness of piston rings in the free-piston engine generator is thicker and lasts shorter at the dead center regions, but it is generally thinner at other positions. The average friction force, friction power, and friction work of the piston rings in the free-piston engine generator are less than the traditional engine due to the better lubrication in endpoints region. Meanwhile, the friction power of the free-piston engine generator increases with the increase in fuel mass or decrease in load. The friction efficiency varies in correlation with the generator load; the optimum friction efficiency can be obtained by either increasing or decreasing from a certain generator load.

scholarly journals Generator Design Considering Mover Action to Improve Energy Conversion Efficiency in a Free-Piston Engine Generator

Electronics ◽  
2021 ◽  
Vol 10 (17) ◽  
pp. 2142
Author(s):  
Mitsuhide Sato ◽  
Shoma Irie ◽  
Jianping Zheng ◽  
Tsutomu Mizuno ◽  
Fumiya Nishimura ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Conversion Efficiency ◽  
Design Method ◽  
Energy Conversion Efficiency ◽  
Field Analysis ◽  
Piston Engine ◽  
Free Piston ◽  
Engine Efficiency ◽  
Free Piston Engine ◽  
Linear Generators

In a free-piston engine generator (FPEG), the power of the engine can be directly regenerated by linear generators without a crank. The mover motion of this system is interrelated with engine and power generation efficiencies due to the direct connection between the mover of the generator and the piston of the engine. The generator should be designed to improve the overall energy conversion efficiency. The dimensions and mass of the mover limit its operating stroke and drive frequency. Herein, we propose a method for designing linear generators and constructing FPEG systems, considering the mover operation to improve engine efficiency. We evaluated the effect of mover operation on the engine and generation efficiencies using thermal and electromagnetic field analysis software. The proposed design method improves the overall energy conversion efficiency compared with a generator that considers only the maximization of generation efficiency. Setting the mover operation for higher engine efficiency and designing a linear generator to realize the operation can effectively improve the energy conversion efficiency of FPEGs.

scholarly journals Electromagnetic Loss Analysis of a Linear Motor System Designed for a Free-Piston Engine Generator

Electronics ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 621 ◽  
Author(s):  
Yunqin Hu ◽  
Zhaoping Xu ◽  
Lijie Yang ◽  
Liang Liu
Keyword(s):  
Motor System ◽  
Pulse Width Modulation ◽  
High Efficiency ◽  
Electrical Energy ◽  
Element Model ◽  
Energy Conversion Efficiency ◽  
Linear Motor ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine

A free-piston engine generator is a new type of power generating device, which has the advantages of high efficiency and simple structure. In this paper, a linear motor system composed of a moving-coil linear motor with axial magnetized magnets and a H-bridge pulse-width modulation (PWM) rectifier is designed for portable free-piston engine generators. Based on the finite-element model of the motor and physical model of the rectifier, the combined electromagnetic model is presented and then validated by the prototype-tested results. The electromagnetic processes of the linear motor system are simulated. The electromagnetic losses during the standard working cycle are analyzed. Under the rated reciprocating frequency of 50 Hz and the rated reciprocating stroke of 36 mm, the mechanical-to-electrical energy conversion efficiency of 86.3% can be obtained by the linear motor system, which meets the requirement of portable free-piston engine generators.

scholarly journals Two-Stroke Thermodynamic Cycle Optimization of a Single-Cylinder Free-Piston Engine Generator

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Houliang Yu ◽  
Zhaoping Xu ◽  
Qinglin Zhang ◽  
Liang Liu ◽  
Ru Hua
Keyword(s):  
Simulation Model ◽  
Performance Optimization ◽  
Thermodynamic Cycle ◽  
Prototype System ◽  
Injection Timing ◽  
Connecting Rod ◽  
Piston Engine ◽  
Free Piston ◽  
Single Cylinder ◽  
Free Piston Engine

A free-piston engine generator (FPEG) is a new type of energy converter, which eliminates the crankshaft and connecting rod mechanism. In order to achieve efficient energy conversion, the two-stroke thermodynamic performance optimization of a single-cylinder free-piston engine generator is investigated in this paper. Firstly, the components, four-stroke thermodynamic cycle, two-stroke thermodynamic cycle, and prototype system of the FPEG are presented in detail. The one-dimensional flow simulation model of the FPEG is created based on the gas dynamics equation, Weber combustion function, and heat transfer function, and then the model is validated by the data tested from the prototype system. According to the four-stroke experimental results of the FPEG, an effective power of 4.75 kW and a peak pressure of 21.02 bar have been obtained. Then, the two-stroke thermodynamic cycle is simulated and compared under the different control parameters of intake air pressure, injection timing, ignition timing, and valve timing through the simulation model. The optimized results show that an indicated thermal efficiency of 27.6%, an indicated power of 6.7 kW, and a maximal working frequency of 25 Hz can be achieved by the prototype system, when the two-stroke thermodynamic cycle is used.

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

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3530
Author(s):  
Fukang Ma ◽  
Shuanlu Zhang ◽  
Zhenfeng Zhao ◽  
Yifang Wang
Keyword(s):  
Systematic Review ◽  
High Efficiency ◽  
Meta Analysis ◽  
Combustion Process ◽  
Research Progress ◽  
Future Research ◽  
Operating Characteristics ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine

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

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