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

Lin, Jiming; Xu, Zhaoping; Chang, Siqin; Yin, Na; Hu, Yan

doi:10.1115/1.4026299

Cited by 19 publications

(12 citation statements)

References 13 publications

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“…In the end, the object function in Eq. (26) and various constraints in the equations mentioned abovenally formulate the original continuous optimization problem as an NLP. Then a suitable non-linear programming algorithm needs to be chosen to solve the NLP generated by GPM.…”

Section: Continuous Bolza Optimal Control Problemmentioning

confidence: 99%

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Optimal motion trajectory for the four-stroke free-piston engine with irreversible Miller cycle via a Gauss pseudospectral method

Lin

Chang

2014

Journal of Non-Equilibrium Thermodynamics

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A four-stroke free-piston engine with internal and external irreversibilities of nite combustion rate of the fuel, heat transfer and friction is investigated in this paper. Under the condition of the xed fuel consumption per cycle, the optimal piston motion trajectory for maximizing the net work output of di erent cases is derived by applying optimal control theory. Considering the path constraints and boundary conditions of this free-piston Miller cycle, a Gauss pseudospectral method (GPM) is presented for solving optimal motion trajectory. The results show that the optimal piston trajectory improves the e ciency by more than 10% and also suitably reduces the heat transfer losses compared to the conventional piston motion. By optimizing the piston motion around the top dead center (TDC), the in-cylinder gas pressure and temperature have a remarkable improvement while the heat transfer losses have a suitable reduction. The e ects of other parameters, such as combustion duration and the frictional coe cient on the piston trajectory, are also investigated. It is shown that optimizing the piston motion trajectory is a good approach for the free-piston engine to improve the e ciency and it can provide guidelines for the optimal control of the practical free-piston engine.

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Section: Continuous Bolza Optimal Control Problemmentioning

confidence: 99%

“…Based on Ref. [25,26], the present paper will further study the four-stroke free-piston Miller cycle engine with internal and external irreversibilities of nite combustion rate of the fuel, friction, and heat transfer. We also set a suitable ignition advance position which must be considered in a real engine.…”

Section: Introductionmentioning

confidence: 99%

Optimal motion trajectory for the four-stroke free-piston engine with irreversible Miller cycle via a Gauss pseudospectral method

Lin

Chang

2014

Journal of Non-Equilibrium Thermodynamics

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“…Therefore, it was necessary to model the combustion fluctuation. According to [19], it was assumed that: Combustion fluctuation was caused by random fluctuation in injected fuel mass and combustion duration, and random fluctuation was in line with the uniform distribution. The injected fuel mass designed for the prototype was 2.5 mg.…”

Section: Thermodynamic Modelmentioning

confidence: 99%

A Reciprocating Motion Control Strategy of Single-Cylinder Free-Piston Engine Generator

et al. 2020

Electronics

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Free-piston engine generator is a novel electrical power generating system developed for electric vehicles, and it is labeled as a more efficient power system than conventional engines. This paper proposes a reciprocating motion control strategy of free piston to enable the stable running of the system. The control problem was decomposed to the stroke control, the top turning center (TTC) control, and the bottom turning center (BTC) control for reducing unnecessary energy consumption during the control. An iterative learning controller (ILC) was designed for the TTC control, the BTC control was based on the combustion states estimation, and the stroke control was based on finite-state machine (FSM). The turning centers of the previous stroke and the maximum cylinder pressure of the current stroke were taken for feedback. A combined simulation model including the combustion cycle fluctuation was presented and validated by the prototype, and the performance of the control strategy was analyzed. The results showed that the system obtained the stable running and the reciprocating motion of the free piston was well controlled.

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“…Now there have been many different free-piston engines are investigated by numerous research groups due to the potential advantages in terms of high fuel efficiency and low engine emissions. For modern applications, the free-piston engine concept has been proposed for applying as hydraulic free-piston engines aiming for smaller scale applications, free-piston engine generator that aims for application in hybrid electric vehicles, and two-stroke high-speed free-piston diesel engine concept aims for marine application [21][22][23][24][25][26].…”

Section: Free-piston Enginementioning

confidence: 99%

Experimental study of the operation characteristics of an air-driven free-piston linear expander

et al. 2017

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Free-piston engine is a kind of linear internal combustion engine, and shows advantages on simple mechanical structure, low frictional losses, high thermal efficiency and operational flexibility. In this research, an experimental test rig of a dual-piston air-driven free-piston linear expander (FPLE) is established using the FPE concept. A linear generator is used to convert the mechanical work of the pistons into electricity during the expansion process. The piston dynamics, the output voltage of the generator, and the expander operation frequency, as well as the system energy conversion efficiency are identified. It is observed that the piston displacement profile is similar with a sinusoidal wave. The piston is found to run at relative high speed during the middle stroke, and peak velocity is usually achieved when the piston approaches the middle stroke. The output voltage of the generator is sensitive with the piston velocity. With higher driven pressure, the expander frequency is higher. The energy conversion efficiency increases with higher driven pressure and can reach up to 55% with a driven pressure of 3.75 bar. This research presents a fundamental analysis of a FPLE prototype, which can be used as a guidance for the future design of this FPLE type.

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

Cited by 19 publications

References 13 publications

Optimal motion trajectory for the four-stroke free-piston engine with irreversible Miller cycle via a Gauss pseudospectral method

Optimal motion trajectory for the four-stroke free-piston engine with irreversible Miller cycle via a Gauss pseudospectral method

A Reciprocating Motion Control Strategy of Single-Cylinder Free-Piston Engine Generator

Experimental study of the operation characteristics of an air-driven free-piston linear expander

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