Numerical Modeling of the Turbulent Spark Ignition Dynamics of Gasoline Surrogates at Fuel-Lean, High Pressure, High Temperature Conditions

• Applicant: Professor Dr. Ulrich Maas
• Subject Area: Energy Process Engineering
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 387641749

• Final Report Year: 2023

Final Report Abstract

The scientific aim of this research project was to numerically model turbulent spark ignition of gasoline surrogates. The focus was on fuel-lean, high pressure, high temperature conditions relevant to spark ignition (SI) engine operation conditions, and on spark energies near the minimum ignition energy (MIE), in near-isotropic turbulence. The project was based on a hierarchical modeling concept. It was imbedded in the call for joint projects ("MOST-DFG Joint Research Projects"). The Taiwanese partner performed experimental investigations of the ignition of gasoline surrogates. The ignition and early flame propagation process of primary reference fuels (PRF) was studied numerically. Simulations were performed to investigate the dependence of minimum ignition energy (MIE) on different parameters such as ignition source size, ignition source geometry and mixture composition (equivalence ratio and research octane number, RON). Reduced chemistry was generated for the ignition process to reduce the computational cost. The reduced chemistry was applied for turbulent ignition processes. The Reaction-Diffusion Manifolds (REDIMs) model, which accounts for the influence of the transport processes (e.g., convection, diffusion) on the chemical kinetics, was used to reduce the dimension of governing conservation equations for the species and, thus, to reduce the computational cost. The REDIM model was then applied to turbulent flames. The coupling with turbulent processes was based on a projection method. The coupling strategy has been tested, and it is found that with the correct coupling strategy between reduced chemistry model and the turbulent mixing models, turbulent extinction and ignition can be well captured. In the simulations, three qualitatively different scenarios after ignition were observed for PRFs: I) Ignition failure. II) Flame kernel formation and flame extinction. III) Flame kernel formation and self-sustained flame propagation. The reason for the flame extinction was found to be the strong diffusion for curved flames with small flame radius. A non-linear dependence of the minimum ignition energy on octane number was found and analyzed. The resulting knowledge helps to understand the slow burning, misfire, and partially burning cycles frequently observed in SI engines operated at fuel-lean conditions.

Publications

• Automatic Construction of REDIM Reduced Chemistry with a Detailed Transport and Its Application to CH4 Counterflow Flames. Energy & Fuels, 34(12), 16572-16584.
  Yu, Chunkan; Li, Xing; Wu, Chunwei; Neagos, Alexander & Maas, Ulrich
  
• REDIM reduced chemistry for the simulation of counterflow diffusion flames with oscillating strain rates. Combustion Theory and Modelling, 24(4), 682-704.
  Yu, Chunkan; Minuzzi, Felipe & Maas, Ulrich
  
• Validation of an Eulerian Stochastic Fields Solver Coupled with Reaction–Diffusion Manifolds on LES of Methane/Air Non-premixed Flames. Flow, Turbulence and Combustion, 107(2), 441-477.
  Breda, Paola; Yu, Chunkan; Maas, Ulrich & Pfitzner, Michael
  
• A novel model for incorporation of differential diffusion effects in PDF simulations of non-premixed turbulent flames based on reaction-diffusion manifolds (REDIM). Physics of Fluids, 33(2).
  Yu, Chunkan; Breda, Paola; Minuzzi, Felipe; Pfitzner, Michael & Maas, Ulrich
  
• Coupling of mixing models with manifold based simplified chemistry in PDF modeling of turbulent reacting flows. Proceedings of the Combustion Institute, 38(2), 2645-2653.
  Yu, Chunkan; Breda, Paola; Pfitzner, Michael & Maas, Ulrich
  
• Experimental and numerical investigations on extinction strain rates in non-premixed counterflow methane and propane flames in an oxygen reduced environment. Fuel, 298, 120781.
  Eckart, Sven; Yu, Chunkan; Maas, Ulrich & Krause, Hartmut
  
• Implementation of the Scalar Dissipation Rate in the REDIM Concept and its Validation for the Piloted Non-Premixed Turbulent Jet Flames. Eurasian Chemico-Technological Journal, 23(3), 169.
  Yu, C. & Maas, U.
  
• Numerical studies on minimum ignition energies in methane/air and iso-octane/air mixtures (2021), Proceedings of the 13th Symposium International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions.
  Wu, Chunwei; Schießl, Robert & Maas, Ulrich
  
• Numerical studies on minimum ignition energies in methane/air and iso-octane/air mixtures. Journal of Loss Prevention in the Process Industries, 72, 104557.
  Wu, Chunwei; Schießl, Robert & Maas, Ulrich
  
• Numerical study on spark ignition of laminar lean premixed methane-air flames in counterflow configuration. Combustion Science and Technology, 195(9), 2085-2109.
  Yu, Chunkan; Markus, Detlev; Schießl, Robert & Maas, Ulrich
  
• Reaction-Diffusion Manifolds (REDIM) Method for Ignition by Hot Gas and Spark Ignition Processes in Counterflow Flame Configurations. Combustion Science and Technology, 195(10), 2400-2422.
  Yu, Chunkan & Maas, Ulrich
  
• Reaction-Diffusion Manifolds including differential diffusion applied to methane/air combustion in strong extinction regimes. Combustion Theory and Modelling, 26(3), 451-481.
  Breda, Paola; Yu, Chunkan; Maas, Ulrich & Pfitzner, Michael
  
• Numerical and experimental studies on minimum ignition energies in primary reference fuel/air mixtures. Proceedings of the Combustion Institute, 39(2), 1987-1996.
  Wu, Chunwei; Chen, Yi-Rong; Schießl, Robert; Shy, Shenqyang (Steven) & Maas, Ulrich