Towards Accurate and Validated Open-Source Simulaons 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 Conno 6 , Nathan J. Quinlan 1,2,3 , Rory F.D. Monaghan 1,2,3,4 1 School of Engineering, Naonal University of Ireland Galway 2 Ryan Instute for Environmental, Marine and Energy Research, Galway 3 MaREI@NUIG 4 Combuson Chemistry Centre, Naonal University of Ireland Galway 5 Physico-Chemical Fundamentals of Combuson, RWTH Aachen University 6 BURN Joint Research Group, Vrije Universiteit Brussel, Université Libre de Bruxelles Movaon Understanding the combuson chemistry of fuels is a vital aspect in the development of new, highly efficient ICEs (Internal Combuson Engines) and gas turbines. This knowledge of the combuson 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-ignion behavior of fuel mixtures, and the results that are produced are used to develop chemical kinec mechanisms. These chemical kinec mechanisms are widely used to model combuson and reacng 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, linearMoonLayersFvMesh, which uses the OpenFOAM mesh modifier layerAddionRemoval. This means that cells are removed during the compression. Fig 7. Layer Removal 2. Soluon Mapping The second approach uses soluon mapping. The fluid domain is separated into several regions, each of which is solved individually. Aſter one region has been solved, the results are ‘mapped’ to the next region. Fig 8. Soluon Mapping Problems with RCMs An issue that arises during the operaon of an RCM, is that of temperature inhomogeneity. As the piston moves through the cylinder, rollup vorces are formed. These vorces result in the transportaon of cool gas from the cylinder walls into the core of the gas mixture. The use of a piston crevice migates against the formaon of these vorces. Fig 3. Vortex Formaon [3] Fig 4. Temperature Inhomogeneity [4] OpenFOAM Open-Source CFD OpenFOAM is a CFD toolbox that has an extensive library of solvers for both stac and dynamic analyses. It is widely used in academia in lieu of expensive commercial soſtware. The potenal 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 Simulaon [6] Numerical Modelling Due to the important role crevice design has in the operaon of RCMs, its design is crical. A great deal of numerical analysis has been conducted into crevice design. Of parcular note is the work of Yousefian, et al., (2018) (Fig 5.). This work found that a 3D LES (Large Eddy Simulaon) simulaon was required when undertaking advanced analysis into crevice design. Fig 5. LES Simulaon of RCM 100 ms aſter EOC [5] Current Progress To date, the majority of work has been on the development of the changing topology approach. This method has a disnct advantage in that cell deformaon is reduced. Figure 9 shows mesh deformaon for cases with 1. No topological change or soluon mapping 2. Soluon mapping with three regions 3. Topological change with layer removal Fig 9. Mesh Deformaon (t=1 @ EOC) Future Work • Further development of linearMoonLayersFvMesh solver • Development of soluon mapping case for full compression stroke • Evaluaon of layer addion removal and soluon mapping methods • Transion from RANS turbulence models to LES Acknowledgments I would like to thank the School of Engineering NUI Galway, the Combuson 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 combuson in spark-ignion engines. Progress in Energy and Combuson 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 ignion characteriscs of hydrocarbon autoignion and an invesgaon 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 formaon 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’, Combuson and Flame, 141(4), pp. 417–430. doi: hps://doi.org/10.1016/j.combuslame.2005.01.015. [5] Yousefian, Sajjad & Quinlan, Nathan & Monaghan, Rory. (2018). Simulaon of turbulent flow in a rapid compression machine: Large Eddy Simulaon and computaonally efficient alternaves for the design of ignion delay me 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’, Combuson and Flame. Elsevier, 198, pp. 393–411. doi: 10.1016/J.COMBUSTFLAME.2018.09.030. Objecves • Development of 3D LES OpenFOAM case for single piston RCM • Flow visualisaon using Reynolds equivalent apparatus • Development of 3D LES OpenFOAM case for double piston RCM • Visualisaon using PIV (Parcle Image Velocimetry) and MTV (Molecular Tagging Velocimetry)