Towards Accurate and Validated Open-Source Simulations
of Rapid Compression Machines for The Study of Novel Fuels Séan J. Gorry 1,2,3,4, Karl Alexander Heufer 5, Henry J. Curran 2,3,4, Francesco Contino 6, Nathan J. Quinlan 1,2,3, Rory F.D. Monaghan 1,2,3,4
1 School of Engineering, National University of Ireland Galway 2 Ryan Institute for Environmental, Marine and Energy Research, Galway 3 MaREI@NUIG 4 Combustion Chemistry Centre, National University of Ireland Galway 5 Physico-Chemical Fundamentals of Combustion, RWTH Aachen University 6 BURN Joint Research Group, Vrije Universiteit Brussel, Université Libre de Bruxelles
Motivation
Understanding the combustion chemistry of fuels is a vital aspect in the development of new,
highly efficient ICEs (Internal Combustion Engines) and gas turbines. This knowledge of the
combustion chemistry is used to reduce emissions, and to ensure that detrimental phenomena,
such as knocking, do not occur. RCMs (Rapid Compression Machines) are used to study the
auto-ignition behavior of fuel mixtures, and the results that are produced are used to develop
chemical kinetic mechanisms. These chemical kinetic mechanisms are widely used to model
combustion and reacting flows.
Fig 1. ICE Damage Caused by Knocking [1] Fig 2. Rapid Compression Machine [2]
OpenFOAM Methodology
As the cylinder volume decreases during the compression stroke, a dynamic mesh is required.
To this end, two separate approaches are being examined.
1. Topology Change with Layer Removal
This approach uses a custom mesh solver, linearMotionLayersFvMesh, which uses the
OpenFOAM mesh modifier layerAdditionRemoval. This means that cells are removed during the
compression.
Fig 7. Layer Removal
2. Solution Mapping
The second approach uses solution mapping. The fluid domain is separated into several regions,
each of which is solved individually. After one region has been solved, the results are ‘mapped’ to
the next region.
Fig 8. Solution Mapping Problems with RCMs
An issue that arises during the operation
of an RCM, is that of temperature
inhomogeneity. As the piston moves
through the cylinder, rollup vortices are
formed. These vortices result in the
transportation of cool gas from the
cylinder walls into the core of the gas
mixture. The use of a piston crevice
mitigates against the formation of these
vortices.
Fig 3. Vortex Formation [3] Fig 4. Temperature Inhomogeneity [4]
OpenFOAM Open-Source CFD
OpenFOAM is a CFD toolbox that has an extensive library
of solvers for both static and dynamic analyses. It is
widely used in academia in lieu of expensive commercial
software. The potential for its use in the study of RCMs
was highlighted by Bourgeois et al., (2018) (Fig 6.) Its
use also facilitates a combined modelling approach
within the RCM community.
Fig 6. OpenFOAM® LES RCM Simulation [6]
Numerical Modelling
Due to the important role crevice design has in the
operation of RCMs, its design is critical. A great deal of
numerical analysis has been conducted into crevice
design. Of particular note is the work of Yousefian, et
al., (2018) (Fig 5.). This work found that a 3D LES (Large
Eddy Simulation) simulation was required when
undertaking advanced analysis into crevice design.
Fig 5. LES Simulation of RCM 100 ms after EOC [5]
Current Progress
To date, the majority of work has been on the development of the changing topology approach.
This method has a distinct advantage in that cell deformation is reduced. Figure 9 shows mesh
deformation for cases with
1. No topological change or solution mapping
2. Solution mapping with three regions
3. Topological change with layer removal
Fig 9. Mesh Deformation (t=1 @ EOC)
Future Work
• Further development of linearMotionLayersFvMesh solver
• Development of solution mapping case for full compression stroke
• Evaluation of layer addition removal and solution mapping methods
• Transition from RANS turbulence models to LES
Acknowledgments
I would like to thank the School of Engineering NUI Galway, the Combustion Chemistry Centre
NUI Galway, and PCFC RWTH Aachen University for the funding that they have provided.
References [1] Wang, Zhi & Liu, Hui & Reitz, Rolf. (2017). Knocking combustion in spark-ignition engines. Progress in Energy and Combustion Sci-
ence. 61. 78-112. 10.1016/j.pecs.2017.03.004.
[2] Chung, J. et al. (2015) ‘Rapid-compression machine studies on two-stage ignition characteristics of hydrocarbon autoignition and an investigation of new gasoline surrogates’, Energy. Pergamon, 93, pp. 1505–1514. doi: 10.1016/J.ENERGY.2015.09.077.
[3] ALLEN, J. J. and CHONG, M. S. (2000) “Vortex formation in front of a piston moving through a cylinder,” Journal of Fluid Mechanics. Cambridge University Press, 416, pp. 1–28. doi: 10.1017/S002211200000865X.
[4] Würmel, J. and Simmie, J. M. (2005) ‘CFD studies of a twin-piston rapid compression machine’, Combustion and Flame, 141(4), pp. 417–430. doi: https://doi.org/10.1016/j.combustflame.2005.01.015.
[5] Yousefian, Sajjad & Quinlan, Nathan & Monaghan, Rory. (2018). Simulation of turbulent flow in a rapid compression machine: Large Eddy Simulation and computationally efficient alternatives for the design of ignition delay time experiments. Fuel. 234. 10.1016/j.fuel.2018.06.117.
[6] Bourgeois, N. et al. (2018) ‘How to ensure the interpretability of experimental data in Rapid Compression Machines? A method to validate piston crevice designs’, Combustion and Flame. Elsevier, 198, pp. 393–411. doi: 10.1016/J.COMBUSTFLAME.2018.09.030.
Objectives
• Development of 3D LES OpenFOAM case for single piston RCM
• Flow visualisation using Reynolds equivalent apparatus
• Development of 3D LES OpenFOAM case for double piston RCM
• Visualisation using PIV (Particle Image Velocimetry) and MTV (Molecular Tagging Velocimetry)