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Numerical and Experimental Investigation of In-Cylinder Flow in a Loop-Scavenged Two-Stroke Free Piston Engine
Technical Paper
2012-32-0114
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
In this paper experimental measurements and simulations of the gas flow inside the combustion chamber of a free piston engine are presented. This combustion unit is integrated into a power train concept, named free-piston linear generator (FPLG), which is designed as a new type of gasoline engine for hybrid electric vehicles. By combining a two stroke combustion chamber, a linear alternator and an adjustable gas spring the engine design aims at a highly efficient conversion of chemical energy into electrical energy. In this context a high system efficiency can only be reached if a two stroke combustion cycle is applied. Efficiency advantages are expected due to the missing mechanical link to a crank which enables a new flexibility in terms of stroke and compression ratio. Instead of scavenging ports the presented FPLG combustion unit has poppet valves which are actuated by a variable electro-magnetic valve train. Hence the gas exchange components are independent from the piston trajectory.
The resulting scavenging flow has a complex three dimensional flow field, which is strongly affected by the location and pressure level of the inlet and the outlet ports. In order to improve the overall efficiency of the two-stroke operating mode fundamental knowledge of the scavenging process is required. Therefore computational fluid dynamic simulations as well as laser diagnostic measurements have been conducted. Using the software package ANSYS CFX 13, a three dimensional mesh of the combustion chamber with valves and pipes was modeled including dynamic mesh movement and automatic re-meshing. The experimental measurements were realized by means of the Particle Image Velocimetry (PIV) techniques. The existing cylinder has been replaced by an optically accessible combustion chamber dummy, whose geometry is equal to that of the combustion chamber during the scavenging process. The two dimensional instantaneous velocity fields were measured in three different section planes which allowed for detailed validation of the CFD simulations.
Through the combination of experimental and numerical methods, an in-depth knowledge of in-cylinder processes during scavenging of a poppet valve two stroke engine was attained. In terms of the global flow field the CFD results show a good accordance with the measured PIV results. Whereas the positions of local velocity peaks are predicted very well, absolute values of velocity deviate to some extent. The authors assume that this discrepancy can be explained by the standard turbulence model and the spatial discretization. Nevertheless the capability of the developed CFD Model to predict in-cylinder flow structures was demonstrated. As a consequence this numerical tool can be used for future simulations in order to investigate new cylinder head geometries and gasoline direct injection.
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Haag, J., Ferrari, C., Starcke, J., Stöhr, M. et al., "Numerical and Experimental Investigation of In-Cylinder Flow in a Loop-Scavenged Two-Stroke Free Piston Engine," SAE Technical Paper 2012-32-0114, 2012, https://doi.org/10.4271/2012-32-0114.Also In
References
- Mikalsen, R. Roskilly, A.P. A review of free-piston engine history and application Applied Thermal Engineering 27 2007 2339 2352
- Achten, P. “A Review of Free Piston Concepts,” SAE Technical Paper 941776 1994 10.4271/941776
- Aichlmayr, H. T. Design Considerations, Modeling, and Analysis of Micro-Homogeneous Charge Compression Ignition Combustion Free Piston Engines PhD Thesis University of Minnesota
- Carter, D. Wechner, E. “The Free Piston Power Pack: Sustainable Power for Hybrid Electric Vehicles,” SAE Technical Paper 2003-01-3277 2003 10.4271/2003-01-3277
- Ferziger, J.H. Peric, M. Computational Methods for Fluid Dynamics 2nd Springer Verlag 2001
- Wang, J. Howe, D. A linear permanent magnet generator for a free-piston energy converter 2005 IEEE International Electric Machines and Drives Conference (IEMDC)
- 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
- Pohl, S.-E. Gräf, M. Dynamic Simulation of a Free-Piston Linear Alternator in Modelica Proceedings of the 4 th international Modelica Conference 2005
- Pohl, S.-E. Der Freikolbenlineargenerator - Theoretische Betrachtung des Gesamtsystems und experimentelle Untersuchungen zum Teilsystem der Gasfeder Dissertation DLR - Forschungsbericht 2007
- Kock, F. Ferrari, C. Flatness-Based High Frequency Control of a Hydraulic Actuator Journal of Dynamic Systems, Measurement, and Control March 2012 134
- Rinderknecht, F. The linear generator as integral component of an energy converter for electric vehicles European All-Wheel Drive Congress Graz 2011
- Rinderknecht, F. Herzog, H.-G. Adaptation and optimization of a linear generator for a hybrid vehicle concept Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition 2010 Shenzhen China
- Heywood, John B. Internal Combustion Engine Fundamentals McGraw-Hill
- Osborne, R. Stokes, J. Lake, T. Carden, P. et al. “Development of a Two-Stroke/Four-Stroke Switching Gasoline Engine - The 2/4 SIGHT Concept,” SAE Technical Paper 2005-01-1137 2005 10.4271/2005-01-1137
- Hooper, P.R Al-Shemmeri, T. Goodwin, M. J. Advanced modern low-emission two-stroke cycle engines Proc.IMechE 225 J. Automobile Engineering
- Compact Dynamics GmbH Manual EVT Dynaline
- ANSYS Germany GmbH Germany IC Engine simulations with ANSYS CFX and ANSYS ICEM CFD - Setup Documentation
- Stansfield, P. Wigley, G. Catto, J. Pitcher, G. PIV analysis of in-cylinder flow structures over a range of realistic engine speed 13 th Int. Symp. on Application of Laser Techniques to Fluid Mechanics
- Heywood, J. Sher, E. The Two-Stroke Cycle Engine - Its development, Operation and Design 1999 Taylor & Francis
- Stöhr, M. Sadanandan, R. Meier, W. Phase-resolved Characterization of vortex-flames interaction in a turbulent swirl flame Experiments in Fluids 2011 5 4 1152 1167
- Petschenig, E. Glanz, R. Sorger, H. Differential Flow Field Analysis in Engine Development MTZ worldwide edition 2010 05
- Hentschel, W. Optical Diagnostics for Combustion Process Development of Direct-Injection Gasoline Engines Proceedings of the Combustion Instiute 28 2000 1119 1135
- Li, Y. Zhao, H. Peng, Z. Ladommatos, N. Particle Image Velocimetry measurements of in-cylinder flow in internal combustion engines - experiment and flow structure analysis Proceedings of the institution of Mechanical Engineers, Part D
- Kohse-Höinghaus, K. Jeffries, J.B. Applied Combustion Diagnostics 2002 Taylor & Francis
- Fajardo, C. Sick, V. Development of a high-speed UV particle image velocimetry technique and application for measurements in internal combustion engines Experiments in Fluids 2009 46 43 53