The optimal path of piston motion for Otto cycle with linear phenomenological heat transfer law

2009 ◽  
Vol 52 (5) ◽  
pp. 708-719 ◽  
Author(s):  
ShaoJun Xia ◽  
LinGen Chen ◽  
FengRui Sun
Keyword(s):  
Heat Transfer ◽  
Optimal Path ◽  
Otto Cycle ◽  
Piston Motion

Predicting the Performance of Diesel Engine Combustion Chambers

1969 ◽  
Vol 184 (10) ◽  
pp. 241-299 ◽  
Author(s):  
D. B. Spalding
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Numerical Analysis ◽  
Finite Difference ◽  
Fluid Dynamic ◽  
Combustion Chambers ◽  
Piston Motion ◽  
Engine Combustion ◽  
Growth Of Knowledge ◽  
Dynamic Heat Transfer

The availability of large digital computers, the recent development of adequate techniques of numerical analysis, and the growth of knowledge about the laws of turbulence, have combined to make possible the development of a comprehensive prediction procedure for the fluid-dynamic, heat transfer and combustion phenomena which take place in diesel engine combustion chambers. The difficulties, and means of surmounting them, are discussed in the lecture; it is argued that a very useful first stage would be a procedure applicable to axisymmetrical chambers; this could be constructed by extending already established techniques and knowledge. The procedure would be of the finite difference variety, and would employ a grid which expanded and contracted to accord with the piston motion.

In-cylinder heat transfer and gas motion of a free-piston diesel engine generator

2017 ◽  
Vol 231 (8) ◽  
pp. 739-752 ◽  
Author(s):  
Chenheng Yuan ◽  
Jing Xu ◽  
Huihua Feng
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Attractive Alternative ◽  
Piston Engine ◽  
Piston Motion ◽  
Compression Process ◽  
Free Piston ◽  
Reciprocating Engine ◽  
Free Piston Engine ◽  
Significant Difference

The free-piston engine generator is an attractive alternative to the conventional reciprocating engine due to the feature that it moves without crankshaft system. This paper presented a simulation for the investigation on the characteristic of in-cylinder gas motion and heat transfer in a compression ignited free-piston engine generator. An operation experiment was performed to obtain the precise piston motion for the modeling of heat transfer and gas flow. The development of the multi-dimensional model was described, and simulation results were presented and showed good similarity with the experimental data. Then, the heat transfer and gas motion in the free-piston engine generator were discussed, on which the influences of piston motion were also investigated compared with a corresponding conventional reciprocating engine. The results indicated that compared with the conventional reciprocating engine, a higher level of squish and reverse squish effect was found for the free-piston engine generator due to its faster motion around top dead center, while its slower piston motion led to weaker gas turbulence in the compression process. Moreover, the free-piston engine generator and conventional reciprocating engine did not show a significant difference in heat transfer during the compression process, however, an obvious advantage of heat transfer was indicated for the free-piston engine generator in combustion and expansion processes due to its lower combustion temperature and the reduced time that is available for heat transfer caused by its faster expansion. The mechanism for such differences is that the free-piston engine generator moves with uneven equivalent speed.

Fundamental Explorations of Spring-Varied, Free Piston Linear Engine Devices

2014 ◽  
Author(s):  
Matthew C. Robinson ◽  
Nigel N. Clark
Keyword(s):  
Heat Transfer ◽  
Compression Ratio ◽  
Combustion Engine ◽  
System Stability ◽  
Otto Cycle ◽  
Restoring Force ◽  
Free Piston ◽  
Mass System ◽  
Heat Addition ◽  
Linear Engine

The conventional crank-based internal combustion engine faces many challenges to remain a viable option for electric power generation. Limitations in mechanical, thermal, and combustion efficiencies must be overcome by innovations in existing technologies and progress towards new ones. The free piston linear engine (FPLE) is a device with the potential to meet these challenges. Friction losses are reduced by avoiding rotational motion and linkages. Instead, electrical power is generated by the oscillation of the translator through a stator. Meanwhile, naturally variable compression ratio provides a unique platform to employ advanced combustion regimes. Possibly high variations in stroke length also result in unknown dead center piston positions and greater difficulties in compression control as compared to conventional engines. Without control, adverse occurrences such as misfire, stall, over-fueling, and rapid load changes pose greater complications for stable system operation. Based on previous research, it is believed that incorporating springs will advance former designs by both increasing system frequency and providing a restoring force to improve cycle-to-cycle stability. Despite growing interest in the FPLE, current literature does not address the use of springs within a dual, opposed piston design. This investigation is an extension of recent efforts in the fundamental analysis of such a device. Previous work by the authors combined the dynamics of a damped, spring mass system with in-cylinder thermodynamic expressions to produce a closed-form non-dimensional model. Simulations of this model were used to describe ideal Otto cycle as the equilibrium operating point. The present work demonstrates more realistic modelling of the device in three distinct areas. In the previous model, the work term was a constant coefficient over the length of the stroke, instantaneous heat addition (representing combustion) was only seen at top dead center positions, and the use of the Otto cycle included no mechanism for heat transfer except at dead center positions. Instead, a position based sinusoid is employed for the work coefficient causing changes to the velocity and acceleration profiles. Instantaneous heat addition prior to top dead center is allowed causing the compression ratio to decrease towards stable, Otto operation. And, a simple heat transfer scheme is used to permit cylinder gas heat exchange throughout the stroke resulting in deviation from Otto operation. Regardless, simulations show that natural system stability arises under the right conditions. Highest efficiencies are achieved at a high compression ratio with minimal heat transfer and near-TDC combustion.

Effect of Piston Motion on Combustion of CNG Free Piston Engine (FPE)

2014 ◽  
Vol 889-890 ◽  
pp. 501-506
Author(s):  
Ning Xia Yin ◽  
Zhao Ping Xu ◽  
Si Qin Chang ◽  
Ji Ming Lin
Keyword(s):  
Heat Transfer ◽  
Combustion Process ◽  
Engine Performance ◽  
Expansion Ratio ◽  
Nox Emissions ◽  
Piston Engine ◽  
Piston Motion ◽  
Free Piston ◽  
Beneficial Effects ◽  
Free Piston Engine

CNG is thought to be one of the most promising alternatives to traditional fuels. The multi-fuel ability is another characteristic of the FPE. The piston motion can be controlled to have beneficial effects on the engine performance. This article investigates the effect of piston motion on combustion of four-stroke CNG FPE using a multidimensional simulation model. It is found that the high piston acceleration and velocity at top dead center increases expansion ratio and fasting combustion, reduces the heat transfer losses and decreased NOx emissions formation. At the same time, the turbulent kinetic energy of the gas during the combustion process is added.

scholarly journals Wall Heat Transfer Analysis of Internal Combustion Engine with Free Piston Linear Motion

2018 ◽  
Vol 7 (3.17) ◽  
pp. 141
Author(s):  
Mior A. Said ◽  
L K. Mun ◽  
A R. A. Aziz ◽  
. .
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Combustion Engine ◽  
Linear Motion ◽  
Piston Engine ◽  
Piston Motion ◽  
Free Piston ◽  
Free Piston Engine ◽  
Set Up ◽  
Motion Profile

The manuscript should contain an abstract. The abstract should be self-contained and citation-free and should not exceed 200 words. The abstract should state the purpose, approach, results and conclusions of the work.  The author should assume that the reader has some knowledge of the subject but has not read the paper. Thus, the abstract should be intelligible and complete in it-self (no numerical references); it should not cite figures, tables, or sections of the paper. The abstract should be written using third person instead of first person. Intensive researches are being carried out on the main power generator for free piston linear generator(FPLG) by both the academic and industrial research group due to its potential as a high fuel efficiency and low emission engine. The linear generator, which is a coil and a translator positioned to move linearly back and forth relative to each other. The study investigates the heat transfer data of internal combustion engine with free piston linear motion profile and compared with the conventional reciprocating engine for one cycle motion only. Engine simulation software GT-Power is employed which utilize the 1-D thermodynamic modeling. All parameters for both free-piston engine are set-up to be the same except for the piston motion profile and the injection timing. Both conventional and free piston engine models are built, simulation settings are set up, and simulations are launched in GT-ISE.  Once simulation is done, results are viewed in GT-POST, the data collected was analysed and compared to investigate the dictinct effect of piston motion to heat transfer profile and data. The overall trend shows that free piston engine have a lower heat transfer rate throughout majority of the cycle. This finding agrees that due to less time of piston near top dead centre area, heat transfer losses to the wall per cycle are reduced. The heat transfer profile of the free piston also shown distinct feature compared to conventional with rapid increase and decrease of heat transfer rate, followed by a secondary peak of gradual decline of the profile.  

Fundamental Explorations of Spring-Varied, Free Piston Linear Engine Devices

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Matthew C. Robinson ◽  
Nigel N. Clark
Keyword(s):  
Heat Transfer ◽  
Compression Ratio ◽  
Combustion Engine ◽  
System Stability ◽  
Otto Cycle ◽  
Restoring Force ◽  
Free Piston ◽  
Mass System ◽  
Heat Addition ◽  
Linear Engine

The conventional crank-based internal combustion engine faces many challenges to remain a viable option for electric power generation. Limitations in mechanical, thermal, and combustion efficiencies must be overcome by innovations in existing technologies and progress toward new ones. The free piston linear engine (FPLE) has the potential to meet these challenges. Friction losses are reduced by avoiding rotational motion and linkages. Instead, electrical power is generated by the oscillation of the translator through a stator. Naturally, variable compression ratio provides a unique platform to employ advanced combustion regimes. However, possibly high variations in stroke length result in unknown dead center piston positions and greater difficulties in compression control as compared to conventional engines. Without control, adverse occurrences such as misfire, stall, over-fueling, and rapid load changes pose greater complications for stable system operation. Based on previous research, it is believed that incorporating springs will advance former designs by both increasing system frequency and providing a restoring force to improve cycle-to-cycle stability. Despite growing interest in the FPLE, current literature does not address the use of springs within a dual, opposed piston design. This investigation is an extension of recent efforts in the fundamental analysis of such a device. Previous work by the authors combined the dynamics of a damped, spring mass system with in-cylinder thermodynamic expressions to produce a closed-form nondimensional model. Simulations of this model were used to describe ideal Otto cycle as the equilibrium operating point. The present work demonstrates more realistic modeling of the device in three distinct areas. In the previous model, the work term was a constant coefficient over the length of the stroke, instantaneous heat addition (representing combustion) was only seen at top dead center (TDC) positions, and the use of the Otto cycle included no mechanism for heat transfer except at dead center positions. Instead, a position based sinusoid is employed for the work coefficient causing changes to the velocity and acceleration profiles. Instantaneous heat addition prior to TDC is allowed causing the compression ratio to decrease toward stable, Otto operation, and a simple heat transfer scheme is used to permit cylinder gas heat exchange throughout the stroke resulting in deviation from Otto operation. Regardless, simulations show that natural system stability arises under the right conditions. Highest efficiencies are achieved at a high compression ratio with minimal heat transfer and near-TDC combustion.

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