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Conditional Moment Closure Model for Ignition of Homogeneous Fuel/Air Mixtures in Internal Combustion Engines

Wang, Wei
http://rave.ohiolink.edu/etdc/view?acc_num=osu1577882100318004

Abstract Details

2020, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
To improve the fuel economy and to reduce the emission in internal combustion (IC) engines, advanced engine technologies such as the homogeneous charge compression ignition (HCCI), further increasing the compression ratio, and gasoline engine downsizing with charge boosting need to be further developed. The development of these technologies is restricted by the prediction and control of the ignition of premixed fuel/air mixtures. The ignition of the premixed mixtures in IC engines is governed by complex chemical kinetics. The in-cylinder flow turbulence, temperature inhomogeneity, and other mixture conditions affect the ignition processes by influencing the chemical reaction rates. In this study, the conditional moment closure (CMC) method is extended for the ignition of the premixed mixtures with temperature inhomogeneity in IC engines. A CMC model based on sensible enthalpy is developed for the ignition of the premixed mixtures. Closure models for the mixing statistics of sensible enthalpy are proposed based on a mapping method. A method to couple the CMC model with a multidimensional flow solver for the prediction of knock in SI engines is developed. In the coupling, a method to reduce the computational cost by solving a subset of species in the flow solver is proposed. The sensible-enthalpy-based CMC model and a total-enthalpy-based formulation are assessed with data from 2-D direct numerical simulation (DNS) of the ignition of homogeneous primary reference fuel (PRF)-air mixtures with temperature inhomogeneity under HCCI conditions and spark ignition (SI) engine knocking conditions. Results show that the total-enthalpy-based CMC gives good predictions of the heat release rate (HRR) under HCCI conditions when the temperature inhomogeneity level is low, but leads to substantial overprediction under SI engine knocking conditions regardless of the thermal stratification levels. The sensible enthalpy formulation gives good predictions of the HRR for the ignition under HCCI and SI engine knocking conditions due to suppressed conditional temperature fluctuations. The proposed mixing models are found to generally well capture the mixing characteristics of the reacting scalar. A method to couple the CMC model with a multidimensional flow solver is developed and the spatially-integrated total-enthalpy-based CMC model is implemented into CONVERGE user defined functions (UDF) for knock prediction in SI engines using large eddy simulation (LES). Multicycle LES of a gasoline direct injection (GDI) engine is conducted with the total-enthalpy-based CMC model and the results are compared with data from engine experiments. Results show that the onsets of knock in reference knocking cases are captured. The effects of spark timing (ST) retarding and wall temperature on the occurrence of knock are investigated.
Seung Hyun Kim, Dr. (Advisor)
Datta Gaitonde, Dr. (Committee Member)
Sutton Jeffrey, Dr. (Committee Member)
Shawn Midlam-Mohler, Dr. (Committee Member)
145 p.
Mechanical Engineering
CMC; ignition; IC engine; knock; HCCI; LES

Recommended Citations

Citations

  • Wang, W. (2020). Conditional Moment Closure Model for Ignition of Homogeneous Fuel/Air Mixtures in Internal Combustion Engines [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1577882100318004

    APA Style (7th edition)

  • Wang, Wei. Conditional Moment Closure Model for Ignition of Homogeneous Fuel/Air Mixtures in Internal Combustion Engines. 2020. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1577882100318004.

    MLA Style (8th edition)

  • Wang, Wei. "Conditional Moment Closure Model for Ignition of Homogeneous Fuel/Air Mixtures in Internal Combustion Engines." Doctoral dissertation, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1577882100318004

    Chicago Manual of Style (17th edition)

osu1577882100318004
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This open access ETD is published by The Ohio State University and OhioLINK.