A numerical program is built to simulate the performance of a spark ignited two-stroke free-piston engine coupled with a linear generator.The computational model combines a series of dynamic and thermodynamic equation...A numerical program is built to simulate the performance of a spark ignited two-stroke free-piston engine coupled with a linear generator.The computational model combines a series of dynamic and thermodynamic equations that are solved simultaneously to predict the performances of the engines.The dynamic analysis performed consists of an evaluation of the frictional force and load force introduced by the generator.The thermodynamic analysis used a single zone model to describe the engine's working cycle which includes intake,scavenging,compression,combustion and expansion,and to evaluate the effect of heat transfer based on the first law of thermodynamics and the ideal gas state equation.Because there is no crankshaft,a time based Wiebe equation was used to express the fraction of fuel burned in the combustion.The calculated results were validated by using the experimental data from another research group.The results indicate that the free-piston generator has some advantages over conventional engines.展开更多
The micro free-piston swing engine(MFPSE)is a new structure,free-piston internal combustion engine.The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression,power and scavenge p...The micro free-piston swing engine(MFPSE)is a new structure,free-piston internal combustion engine.The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression,power and scavenge processes based on the open thermodynamic systems were presented.A simulation was executed at given geometric parameters and initial conditions.The results manifest that the working principle of MFPSE is feasible.展开更多
In this paper,the effect of disturbances on the operation process of a methane-fueled free-piston engine generator(FPEG)was experimentally investigated.Four disturbance sources,namely step change of external load,mixt...In this paper,the effect of disturbances on the operation process of a methane-fueled free-piston engine generator(FPEG)was experimentally investigated.Four disturbance sources,namely step change of external load,mixture flow rate fluctuation,random misfire of a cylinder,and elastic collision,were identified and applied to the FPEG.The results showed that the FPEG successfully achieved a steady-state operation with load.The maximum instantaneous electric power of 127 W and the average effective electric power of 38.9 W were obtained.When an external load was instantaneously disconnected,the engine frequency increased from 26.7 Hz to 31.3 Hz.The fluctuation amplitudes of induced voltage,pressure and compression ratio were 18.9%,24.7%and 52.2%respectively in the disturbance.By contrast,when the external load was instantaneously connected,the corresponding values were 42.2%,31.3%and 64.3%respectively,indicating that the instantaneous external load connection had a greater disturbance impact on the FPEG operation stability.Despite encountering the step change of external load,the FPEG can still restore stable operation and show good anti-disturbance ability.Compared with increasing mixture flow rate,reducing the mixture flow rate has a greater disturbance impact on the engine operation stability.Although random misfire of a cylinder will cause remarkable fluctuations in piston displacement and cylinder pressure,the FPEG will not stop running,but continues to work as a single-piston engine.Minor collision event may adversely affect the stability of engine operation,but will not lead to the FPEG shutdown.However,serious collision event may lead to ignition failure and shutdown accident.展开更多
Free-piston engine generators (FPEGs) can be applied as decarbonized range extenders for electric vehicles because of their high thermal efficiency, low friction loss, and ultimate fuel flexibility. In this paper, a p...Free-piston engine generators (FPEGs) can be applied as decarbonized range extenders for electric vehicles because of their high thermal efficiency, low friction loss, and ultimate fuel flexibility. In this paper, a parameter-decoupling approach is proposed to model the design of an FPEG. The parameter-decoupling approach first divides the FPEG into three parts: a two-stroke engine, an integrated scavenging pump, and a linear permanent magnet synchronous machine (LPMSM). Then, each of these is designed according to predefined specifications and performance targets. Using this decoupling approach, a numerical model of the FPEG, including the three aforementioned parts, was developed. Empirical equations were adopted to design the engine and scavenging pump, while special considerations were applied for the LPMSM. A finite element model with a multi-objective genetic algorithm was adopted for its design. The finite element model results were fed back to the numerical model to update the LPMSM with increased fidelity. The designed FPEG produced 10.2 kW of electric power with an overall system efficiency of 38.5% in a stable manner. The model provides a solid foundation for the manufacturing of related FPEG prototypes.展开更多
This paper presents a design for a novel,palm sized,high-aspect-ratio engine.To simplify fabrication and keep the device unobtrusive,a design incorporating a two-cycle engine having a flat,rectangular piston with spri...This paper presents a design for a novel,palm sized,high-aspect-ratio engine.To simplify fabrication and keep the device unobtrusive,a design incorporating a two-cycle engine having a flat,rectangular piston with spring return was selected.An experimental engine based on this concept producing a significant amount of useful work was developed.Although results were encouraging,this geometry raised many issues to be investigated and resolved,including the effects of piston sealing,scavenging,heat losses,and combustion efficiency.Due to the complex interplay between these effects,experimental investigation was time consuming and simple models were found to be inadequate.Therefore,a more complex theoretical model accounting for these effects was developed and used to evaluate the sensitivity of engine performance to each of these parameters.The predictions of this model were used to develop recommendations for improving the experimentally developed engine.展开更多
To develop high energy-density micro power generation systems, a novel two-stroke cycle micro free-piston swing engine (MFPSE), inspired by the concept of the micro internal combustion swing engine, is proposed to sup...To develop high energy-density micro power generation systems, a novel two-stroke cycle micro free-piston swing engine (MFPSE), inspired by the concept of the micro internal combustion swing engine, is proposed to supply mechanical power for a micro power generation system. The working principle, gas exchange and ignition timing control cycles, and structure and operation advantages of the MFPSE are dis- cussed in detail. A prototype where the timing control and geometric parameters are designed with refer- ence to a traditional two-stroke cycle internal combustion engine is fabricated. The successful ignition ex- periment shows that this new concept engine is feasible and is worthy of further study.展开更多
文摘A numerical program is built to simulate the performance of a spark ignited two-stroke free-piston engine coupled with a linear generator.The computational model combines a series of dynamic and thermodynamic equations that are solved simultaneously to predict the performances of the engines.The dynamic analysis performed consists of an evaluation of the frictional force and load force introduced by the generator.The thermodynamic analysis used a single zone model to describe the engine's working cycle which includes intake,scavenging,compression,combustion and expansion,and to evaluate the effect of heat transfer based on the first law of thermodynamics and the ideal gas state equation.Because there is no crankshaft,a time based Wiebe equation was used to express the fraction of fuel burned in the combustion.The calculated results were validated by using the experimental data from another research group.The results indicate that the free-piston generator has some advantages over conventional engines.
基金National Natural Science Foundation(50375078)Key Discipline Construction Program of Beijing.
文摘The micro free-piston swing engine(MFPSE)is a new structure,free-piston internal combustion engine.The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression,power and scavenge processes based on the open thermodynamic systems were presented.A simulation was executed at given geometric parameters and initial conditions.The results manifest that the working principle of MFPSE is feasible.
基金supported by the National Natural Science Foundation of China(No.52076007)Project of Educational Commission of Henan Province of China(No.22A470007 and No.20A470008)。
文摘In this paper,the effect of disturbances on the operation process of a methane-fueled free-piston engine generator(FPEG)was experimentally investigated.Four disturbance sources,namely step change of external load,mixture flow rate fluctuation,random misfire of a cylinder,and elastic collision,were identified and applied to the FPEG.The results showed that the FPEG successfully achieved a steady-state operation with load.The maximum instantaneous electric power of 127 W and the average effective electric power of 38.9 W were obtained.When an external load was instantaneously disconnected,the engine frequency increased from 26.7 Hz to 31.3 Hz.The fluctuation amplitudes of induced voltage,pressure and compression ratio were 18.9%,24.7%and 52.2%respectively in the disturbance.By contrast,when the external load was instantaneously connected,the corresponding values were 42.2%,31.3%and 64.3%respectively,indicating that the instantaneous external load connection had a greater disturbance impact on the FPEG operation stability.Despite encountering the step change of external load,the FPEG can still restore stable operation and show good anti-disturbance ability.Compared with increasing mixture flow rate,reducing the mixture flow rate has a greater disturbance impact on the engine operation stability.Although random misfire of a cylinder will cause remarkable fluctuations in piston displacement and cylinder pressure,the FPEG will not stop running,but continues to work as a single-piston engine.Minor collision event may adversely affect the stability of engine operation,but will not lead to the FPEG shutdown.However,serious collision event may lead to ignition failure and shutdown accident.
基金the Shanghai Science and Technology Commission(No.19511108500).
文摘Free-piston engine generators (FPEGs) can be applied as decarbonized range extenders for electric vehicles because of their high thermal efficiency, low friction loss, and ultimate fuel flexibility. In this paper, a parameter-decoupling approach is proposed to model the design of an FPEG. The parameter-decoupling approach first divides the FPEG into three parts: a two-stroke engine, an integrated scavenging pump, and a linear permanent magnet synchronous machine (LPMSM). Then, each of these is designed according to predefined specifications and performance targets. Using this decoupling approach, a numerical model of the FPEG, including the three aforementioned parts, was developed. Empirical equations were adopted to design the engine and scavenging pump, while special considerations were applied for the LPMSM. A finite element model with a multi-objective genetic algorithm was adopted for its design. The finite element model results were fed back to the numerical model to update the LPMSM with increased fidelity. The designed FPEG produced 10.2 kW of electric power with an overall system efficiency of 38.5% in a stable manner. The model provides a solid foundation for the manufacturing of related FPEG prototypes.
文摘This paper presents a design for a novel,palm sized,high-aspect-ratio engine.To simplify fabrication and keep the device unobtrusive,a design incorporating a two-cycle engine having a flat,rectangular piston with spring return was selected.An experimental engine based on this concept producing a significant amount of useful work was developed.Although results were encouraging,this geometry raised many issues to be investigated and resolved,including the effects of piston sealing,scavenging,heat losses,and combustion efficiency.Due to the complex interplay between these effects,experimental investigation was time consuming and simple models were found to be inadequate.Therefore,a more complex theoretical model accounting for these effects was developed and used to evaluate the sensitivity of engine performance to each of these parameters.The predictions of this model were used to develop recommendations for improving the experimentally developed engine.
基金Supported by the National Natural Science Foundation of China (No. 50375078)
文摘To develop high energy-density micro power generation systems, a novel two-stroke cycle micro free-piston swing engine (MFPSE), inspired by the concept of the micro internal combustion swing engine, is proposed to supply mechanical power for a micro power generation system. The working principle, gas exchange and ignition timing control cycles, and structure and operation advantages of the MFPSE are dis- cussed in detail. A prototype where the timing control and geometric parameters are designed with refer- ence to a traditional two-stroke cycle internal combustion engine is fabricated. The successful ignition ex- periment shows that this new concept engine is feasible and is worthy of further study.
