Research Collection Doctoral Thesis Simulation of Turbulent Premixed Combustion of Hydrogen- Methane Admixtures in Internal Combustion Engines Author(s): Koch, Jann Publication Date: 2019 Permanent Link: https://doi.org/10.3929/ethz-b-000373062 Rights / License: In Copyright - Non-Commercial Use Permitted This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library Diss. ETH No. 25722 SIMULATION OF TURBULENT PREMIXED COMBUSTION OF HYDROGEN-METHANE ADMIXTURES IN INTERNAL COMBUSTION ENGINES A dissertation submitted to ETH ZURICH for the degree of Doctor of Sciences presented by Jann Koch Master of Science ETH in Mechanical Engineering born March 28, 1988 citizen of Ruswil LU, Switzerland accepted on the recommendation of Prof. Konstantinos Boulouchos, examiner Prof. Andreas Kempf, co-examiner Dr. Yuri M. Wright, co-examiner 2019 Jann Koch [email protected] Dedicated to my family The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails. William Arthur Ward Acknowledgements The present work was carried out at the Laboratory of Aerothermochem- istry and Combustion Systems (LAV) at the Swiss Federal Institute of Technology (ETH) Zurich. Financial support from the Swiss Federal Office of Energy (BfE, grant no. SI/500644-01) and from the Swiss Competence Centre Energy and Mobility (CCEM, project \RENERG2") is gratefully acknowledged. Firstly, I would like to thank Professor Konstantinos Boulouchos for provid- ing me with the unique opportunity to undertake this work in the course of the past years. Throughout this period he guided me with constant trust and encouragement. His involvement helped my development on a professional as well as personal level. My appreciation towards Professor Kempf for his interest in this work and willingness to act as a co-examiner shall be expressed here as well. My special thanks go to Dr. Yuri M. Wright who provided me not only with theoretical guidance but also introduced me to the scientific commu- nity. His push to present at global conferences helped my personal growth tremendously. Also Jacoby shall be mentioned here. I am grateful for the discussions and inputs from Dr. Michele Bolla. His very own way of direct and honest advice, offered also outside of standard office hours, was invaluable when it came to decision making throughout the course of this work. I'd like to thank Dr. Thomas Kammermann and Christian Sch¨urch for pro- viding me with much needed experimental results and meeting my yearn- ings for high fidelity data within a setup as complex and experimentally dirty as a full metal IC-engine. I consider the successful and smooth col- laboration a key point of this work, to which they contributed substantially by broadening my horizon from their point of view as an experimentalist which helped identifying and understanding key processes. A fruitful exchange and collaboration was had with Dr. Karri Keskinen from Aalto University, Helsinki Finland. The outcome was not only limited to well-accepted publications but also the proof that alcoholic beverages and enthusiasm for cars and engines bridges cultures and languages. iii I am thankful for Dr. Martin Schmitt who supervised my Master thesis which in turn set the stage for this work. We became office colleagues that profited from each others expertise. I also want to thank Dr. George Gian- nakopoulos who continued in Martins position and extended the scope of our LES-DNS exchange with deep-dives into asymptotic theory of laminar flames, always challenging the seemingly commonly accepted. My thanks go to my numerous colleagues of the laboratory. They had to endure my daily gastronomical critique during lunch break. We shared countless much needed coffee breaks with our very own interpretation of office sports. Great times were had in and outside the scope of our research and friendships were bond for the future. I am thankful for my friends that kept me busy and distracted outside my research work. They showed great understanding for my deep-dives and moods that at times left me less available to join their plans. Finally, I would like to express my sincerest gratitude towards my family. They recognized the spark lingering within me early on. They promoted this very spark to become a baby-flame throughout my childhood by al- lowing me to follow all my curiosities and interests for the world. And they let it grow to become a fully established flame by covering my back and providing me with all the encouragement, understanding and support to pursuit this work. Among many key lessons I also got taught the impor- tance of taking a step back and letting the mind come to rest. A substantial amount of the achievement made today belongs to them. Z¨urich, December 2018 Jann Koch iv Contents List of publications viii Abstract x Zusammenfassung xii 1 Introduction 1 1.1 Motivation . .1 1.2 Objective of this dissertation . .5 1.3 Thesis structure . .6 2 State of the Art 7 2.1 Turbulent flows in IC engines . .7 2.1.1 DNS . .8 2.1.2 RANS . .9 2.1.3 LES . 10 2.2 Premixed combustion . 13 2.2.1 Laminar premixed flames . 13 2.2.2 Turbulent premixed combustion fundamentals . 14 2.2.3 Modelling of turbulent premixed combustion . 17 2.3 Hydrogen Addition . 23 2.4 Conclusion . 26 3 Methodology 27 3.1 Experimental Setup . 27 3.2 GT-Power model . 28 3.3 Simulation framework . 29 3.4 Boundary conditions . 29 3.5 Turbulence model . 29 3.6 Combustion model . 32 3.6.1 Laminar flame speed . 33 3.6.2 Turbulent flame speed . 34 3.6.3 Ingnition and early flame phase treatment . 35 3.6.4 Wall effects . 36 4 Contribution 39 4.1 Comparability of measurements and numerical prediction . 40 4.2 Publication I: RANS of the mean cycle for methane chemistry 40 4.2.1 Turbulent flame speed closure . 41 4.2.2 Impact of turbulence model . 42 4.3 Publication II: Assessment of LES combustion models based on DNS data . 43 4.4 Publication III: Cyclic variability of the combustion process for a single component fuel . 47 4.5 Publication IV & V: Effect of hydrogen addition . 50 4.5.1 Publication IV: Mean cycle . 51 4.5.2 Publication V: Cyclic variability . 53 5 Conclusion and outlook 57 5.1 Conclusion . 57 5.2 Outlook . 60 Nomenclature 63 List of Tables 67 List of Figures 67 Bibliography 71 Curriculum Vitae 91 Publications 97 Publication I . 99 Publication II . 115 Publication III . 129 Publication IV . 149 Publication V . 163 vi vii List of publications This thesis consists of an overview and of the following publications which are referred to in the text by their Roman numerals and can be found appended to this document. I. J.Koch, G. Xu, Y.M. Wright, K. Boulouchos and M. Schiliro. "Comparison and Sensitivity Analysis of Turbulent Flame Speed Clo- sures in the RANS G-Equation Context for Two Distinct Engines", SAE International Journal of Engines, 2016. doi: 10.4271/2016-01-2236 II. J.Koch, S. Geringer, D. Farrace, S. Pandurangi, M. Bolla, Y.M. Wright, M. Jafargholi, Ch. Frouzakis and K. Boulouchos. "Assessment of Two Premixed LES Combustion Models in an Engine- Like Geometry", SAE Technical Paper 2018-01-0176, 2018. doi: 10.4271/2018-01-0176 III. J.Koch, M. Schmitt, Y.M. Wright, K. Steurs and K. Boulouchos. "LES Multi-Cycle Analysis of the Combustion Process in a Small SI Engine", SAE International Journal of Engines, 2014. doi: 10.4271/2014-01-1138 IV. J.Koch, Ch. Sch¨urch, Y.M. Wright and K. Boulouchos. "CRFD Modelling Methane-Hydrogen Admixtures in IC-Engines Part I: RANS", International Journal of Engine Research, in submission V. J.Koch, Ch. Sch¨urch, Y.M. Wright and K. Boulouchos. "CRFD Modelling Methane-Hydrogen Admixtures in IC-Engines Part II: LES", International Journal of Engine Research, in submission viii ix Abstract Pushed by the demand of de-fossilisation of the road-based transporta- tion sector, new powertrain technologies arise in form of electrification. Their potential and acceptance within the population can be increased in combination with range extenders in form of a small SI engine, operated with compressed natural gas. The necessary change in the energy sys- tem to meet global climate targets will lead to an increase in the share of renewable energies, where major contributors are in the form of wind and photovoltaic. The integration of these technologies is challenging, as their supply undergoes pronounced fluctuations. In order to deal with the unavoidable imbalance between supply, storage solutions are a key technol- ogy. In Switzerland, a viable storage solution could be power-to-gas which utilizes the excess renewable power at zero marginal cost for the production of hydrogen and methane, which is then stored in the gas grid. In this context, gas engines maintain their relevance. One aspect of pre- mixed gas combustion are cyclic fluctuations of the combustion process caused by the interaction of the flame propagation with the turbulent flow field. These fluctuations limit the optimal engine tuning and are responsi- ble of emissions of unburned hydrocarbons. Vast research has shown the beneficial effect of small amounts of hydrogen addition to methane combus- tion in terms of lowering cyclic variability ands lowering engine emissions. Whereas a lot of experimental work has been performed, only little research has been performed on the numerical investigation of hydrogen-methane addition, and more specifically its effect on the cyclic variability of the combustion process. This thesis provides a combustion model suited to reactive 3-dimensional computational fluid mechanics that is capable of reproducing the cyclic variations of the combustion process and moreover, to consider the influ- ence of hydrogen addition on the resulting fluctuations.