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22 results on '"See, Yee Chee"'

10. Development of a Virtual CFR Engine Model for Knocking Combustion Analysis

Author

Universitat Politècnica de València. Departamento de Máquinas y Motores Térmicos - Departament de Màquines i Motors Tèrmics, U.S. Department of Energy, Pal, Pinaki, Kolodziej, Christopher, Choi, Seungmok, Som, Sibendu, Broatch, A., Gómez-Soriano, Josep, Wu, Yunchao, Lu, Tianfeng, See, Yee Chee, Universitat Politècnica de València. Departamento de Máquinas y Motores Térmicos - Departament de Màquines i Motors Tèrmics, U.S. Department of Energy, Pal, Pinaki, Kolodziej, Christopher, Choi, Seungmok, Som, Sibendu, Broatch, A., Gómez-Soriano, Josep, Wu, Yunchao, Lu, Tianfeng, and See, Yee Chee

Abstract

[EN] Knock is a major bottleneck to achieving higher thermal efficiency in spark-ignited (SI) engines. The overall tendency to knock is highly dependent on fuel anti-knock quality as well as engine operating conditions. It is, therefore, critical to gain a better understanding of fuel-engine interactions in order to develop robust knock mitigation strategies. In the present work, a numerical model based on three-dimensional (3-D) computational fluid dynamics (CFD) was developed to capture knock in a Cooperative Fuel Research (CFR) engine. For combustion modeling, a hybrid approach incorporating the G-equation model to track turbulent flame propagation, and a homogeneous reactor multi-zone model to predict end-gas auto-ignition ahead of the flame front and post-flame oxidation in the burned zone, was employed. In addition, a novel methodology was implemented wherein a laminar flame speed lookup table generated a priori from a chemical kinetic mechanism could be used to provide flame speed as an input to the G-equation model, instead of using conventional empirical correlations. Multi-cycle Reynolds-Averaged Navier Stokes (RANS) simulations were performed for two different spark timings (STs) corresponding to non-knocking and knocking conditions, with other operating conditions kept the same as those of a standard Research Octane Number (RON) test. Iso-octane was considered as the fuel for the numerical study. Two different reduced kinetic mechanisms were employed to describe end-gas auto-ignition chemistry and to generate the flame speed lookup table. Experimental data, including intake/exhaust boundary conditions, was provided by a spark timing sweep study conducted in an in-house CFR engine. Moreover, cylinder wall/valve/port surface temperatures and residual gas fraction (RGF) were estimated using a well-calibrated one-dimensional (1-D) model. On the other hand, a novel methodology was also developed to analyze experimental data for the knocking case and identify

Published
2018

22. Analysis of Hydrodynamic Instabilities and Combustion Dynamics in Turbulent Reacting Flows.

Author

See, Yee Chee

Subjects
Large Eddy Simulation, Combustion, Linear Stability Analysis, Flamelet
Abstract

The design of new gas turbine engine combustors is largely driven by the demand for higher fuel efficiencies and increasingly stringent emission regulations. Predictive modeling capabilities can assist in the design-process of such advanced combustion systems. These modeling capabilities can generally be categorized into low-order and high-fidelity approaches. This work considers both approaches to model, analyze, and characterize hydrodynamic and combustion-driven instabilities in turbulent reacting flows. Several model-developments are performed in order to improve the physical representation of low-order models, thereby enabling a consistent representation of fundamental combustion-physical processes, including the reaction-chemistry, the thermo-viscous-diffusive transport, and the combustion representation. The resulting model-formulation is demonstrated in application to linear stability analysis of a jet-diffusion flame. Comparisons with experimental data and detailed simulation results are performed, and fundamental physical processes, related to the coupling of buoyancy, transport-properties, and the representation of the reaction chemistry, are analyzed. The second part of this work addresses the high-fidelity modeling, and large-eddy simulations of a dual-swirl gas-turbine model combustor are performed. A comprehensive model-analysis is conducted to systematically investigate the influence of mesh-resolution, subgrid-models, boundary-conditions, and closure-formulations on the flow-field structure and flame-shape. A prior model examination is performed to assess the role of the combustion-regime representation, and it is found that premixed and non-premixed combustion-models provide comparable results. Comprehensive comparisons with experimental data are performed and it is shown that the combustion models accurately capture the complex combustion dynamics present in this burner. Effects of heat-losses and the representation of flame-wrinkling at the residual scales on the flow-field structure are analyzed, and limitations of these combustion models are examined.

Published
2014

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