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Study on the Use of Springs in a Dual Free Piston Engine Alternator
Technical Paper
2016-01-2233
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
The free piston engine combined with a linear electric alternator has the potential to be a highly efficient converter from fossil fuel energy to electrical power. With only a single major moving part (the translating rod), mechanical friction is reduced compared to conventional crankshaft technology. Instead of crankshaft linkages, the motion of the translator is driven by the force balance between the engine cylinder, alternator, damping losses, and springs. Focusing primarily on mechanical springs, this paper explores the use of springs to increase engine speed and reduce cyclic variability. A numeric model has been constructed in MATLAB®/Simulink to represent the various subsystems, including the engine, alternator, and springs. Within the simulation is a controller that forces the engine to operate at a constant compression ratio by affecting the alternator load. The complex interdependence of the free piston engine alternator is analyzed with respect to parametric changes to the spring stiffness. For a fixed compression ratio, it is shown that an increase in spring stiffness from 50 to 350 kN/m (which practically must be associated with an increase in total moving mass) raises system frequency (18%) and power (12%), but can also lead to a relatively small loss of system efficiency (2%). This is due to the decrease of charging efficiency (EGR increased by 12%) for fixed intake/exhaust conditions and higher frictional losses (4%). The gain in system frequency and power output is diminished according to the increased moving mass associated with stiffer springs. This study also investigates the ability of springs to dampen cyclic variation in response to combustion variation. Normally distributed noise is added to combustion efficiency and duration. Coefficients of variation of compression ratio and peak pressure are used to represent cycle to cycle variation response and compared for varied spring stiffnesses. It is shown that the stiff springs can be used to dampen the effects of combustion stochastics and the resulting variation brought on by cylinder pressure variation. This results in lower controller demand and higher operational sustainability.
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Citation
Robinson, M. and Clark, N., "Study on the Use of Springs in a Dual Free Piston Engine Alternator," SAE Technical Paper 2016-01-2233, 2016, https://doi.org/10.4271/2016-01-2233.Also In
References
- Kosaka , H. , Akita , T. , Moriya , K. , Goto , S. et al. Development of Free Piston Engine Linear Generator System Part 1 - Investigation of Fundamental Characteristics SAE Technical Paper 2014-01-1203 2014 10.4271/2014-01-1203
- Mikalsen , R. and Roskilly , A. The Control of a Free-Piston Engine Generator. Part 1: Fundamental Analyses Applied Energy 87 4 1273 1280 2010 10.1016/j.apenergy.2009.06.036
- Mikalsen , R. and Roskilly , A. A Review of Free-Piston Engine History and Applications Applied Thermal Engineering 27 14-15 2339 2352 2007
- Clark , N. , Nandkumar , S. , Atkinson , C. , Atkinson , R. et al Experimental Examination of a Small Bore Linear Two-Stroke Engine ASME Internal Combustion Engine Fall Conference Clymer, NY 33 42 1998
- Tóth-Nagy , C. and Clark , N. The Linear Engine in 2004 SAE Technical Paper 2005-01-2140 2005 10.4271/2005-01-2140
- Rinderknecht , F. A Highly Efficient Energy Converter for a Hybrid Vehicle Concept - Focused on the Linear Generator of the Next Generation 8th International Conference and Exhibition on Ecological Vehicles and Renewable Energies Monte-Carlo, France 1 7 2013 10.1109/EVER.2013.6521533
- Robinson , M. Analysis and Optimization of a Dual Free Piston, Spring Assisted, Linear Engine Generator Ph.D. Dissertation West Virginia University Morgantown, WV 2015
- Robinson , M. and Clark , N. Effect of Combustion Timing and Heat Loss on Spring-Assisted Linear Engine Translator Motion SAE Int. J. Engines 9 1 546 564 2016 10.4271/2016-01-0560
- Wakuri , Y. , Hamatake , T. , Soejima , M. , and Kitahara , T. Piston Ring Friction in Internal Combustion Engines Tribology International 25 5 299 308 1992 10.1016/0301-679X(92)90027-K
- Wahab , H. , Ibraheem , R. , and Shakir , M. Study of Piston Ring Dynamics during Operation of a Diesel Engine Journal of Science and Engineering 2 2 71 79 2013
- Goldsborough , S. and Van Blarigan , P. A Numerical Study of a Free Piston IC Engine Operating on Homogeneous Charge Compression Ignition Combustion SAE Technical Paper 1999-01-0619 1999 10.4271/1999-01-0619
- Schneider , S. , Rinderknecht , F. , and Friedrich , H. Design of Future Concepts and Variants of the Free Piston Linear Generator 9th International Conference on Ecological Vehicles and Renewable Energies Monte-Carlo, France 1 8 2014 10.1109/EVER.2014.6844029
- Liao , K. , Liu , Y. , Kim , D. , Urzua , P. , and Tian , T. Practical Challenges in Determining Piston Ring Friction Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 227 112 225 2013 10.1177/1350650112465364
- Egnell , R. Combustion Diagnostics by Means of Multizone Heat Release Analysis and NO Calculation SAE Technical Paper 981424 1998 10.4271/981424
- Hohenberg , G. Advanced Approaches for Heat Transfer Calculations SAE Technical Paper 790825 1979 10.4271/790825
- Atkinson , C. , Petreanu , S. , Clark , N. , Atkinson , R. et al. Numerical Simulation of a Two-Stroke Linear Engine-Alternator Combination SAE Technical Paper 1999-01-0921 1999 10.4271/1999-01-0921
- Jia , B. , Zuo , Z. , Tian , G. , Feng , H. Development and Validation of a Free-Piston Engine Generator Numerical Model Energy Conversion and Management 91 333 341 2015 10.1016/j.enconman.2014.11.054
- Sher , E. and Harari , R. A Simple and Realistic Model for the Scavenging Process in a Crankcase-Scavenged 2-Stroke Cycle Engine Proceedings of the Institute of Mechanical Engineers, Part A: Journal of Power and Energy 205 2 129 137 1991
- Snyder , C. NASA Glenn thermodynamic database [Online] http://www.grc.nasa.gov/WWW/CEAWeb/ceaThermoBuild.htm
- Cawthorne , W. Optimization of a Brushless Permanent Magnet Linear Alternator for Use with a Linear Internal Combustion Engine Ph.D. Dissertation West Virginia University Morgantown, WV 1999
- Li , Q. , Xiao , J. , and Huang , Z. Simulation of a Two-Stroke Free-Piston Engine for Electrical Power Generation Energy and Fuels 22 5 3443 3449 2008 10.1021/ef800217k
- Feng , H. , Song , Y. , Zuo , Z. , Shang , J. et al Stable Operation and Electricity Generating Characteristics of a Single-Cylinder Free Piston Engine Linear Generator: Simulation and Experiments Energies 8 2 765 785 2015 10.3390/en8020765
- Cho , H. and He , B. Combustion and Emission Characteristics of a Natural Gas Engine Under Different Operating Conditions Environmental Engineering Research 14 2 95 101 2009 10.4491/eer.2009.14.2.095