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Your search keyword '"Kwak, Kyoung Hyun"' showing total 2 results
Start Over Author "Kwak, Kyoung Hyun" Topic ignition delay
2 results on '"Kwak, Kyoung Hyun"'

1. Knock detection in a quasi-dimensional SI combustion simulation using ignition delay and knock combustion modeling.

Author

Kwak, Kyoung Hyun, Jung, Dewey, Park, Hyunil, Paeng, Jeonghwan, and Hwang, Kyumin

Subjects
*SPARK ignition engines, *DIESEL motor combustion, *HEAT release rates, *COMBUSTION, *ENGINE testing, *ANTIKNOCK gasoline, *KNOCK in automobile engines
Abstract

In spark ignition (SI) engines, knock suppression is essential to improve fuel economy. Integrating new technologies into already complex downsized turbocharged engines increases the number of design and control variables substantially and requires extensive engine testing. Utilizing simulation-based study in an engine development process is crucial to reduce expensive and time-consuming engine tests. A quasi-dimensional (quasi-D) two-zone SI engine model is typically used in SI engine simulations. However, the usefulness of quasi-D-based simulation tools is often limited by the predictive capability of knock models. In this study, a novel knock model intended to be implemented in quasi-D SI engine simulation was developed. The model comprises a two-stage ignition delay model, a knock combustion model, and a knock index model. The knock model simulates the heat release spike during a knock combustion, which can be observed from the apparent heat release rate generated with the low-pass filtered cylinder pressure data. The model was calibrated and validated against engine experimental data. Its capability of knock detection and knock-limited spark timing estimation was demonstrated under various conditions of octane numbers, air–fuel equivalence ratios, and coolant temperatures with toluene primary reference fuel (TRPF). The knock model was also able to capture different knock characteristics between TPRF and primary reference fuel (PRF) in modern downsized turbocharged SI engines. The proposed methodology represents a useful tool to be employed during the development phase of an engine to reduce the experimental efforts while improving the engine performance at knock borderline. [ABSTRACT FROM AUTHOR]

Published
2021
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2. Fuel Sensitive Combustion Model Based On Quasi-Dimensional Multi-Zone Approach For Direct Injection Compression Ignition Engines.

Author

Kwak, Kyoung Hyun

Subjects
Diesel Engine, Quasi-dimensional Multi-zone Simulation, Alternative Fuels, Ignition Delay, Multi-component Evaporation, Spray Model
Abstract

This study describes a development of fuel sensitive quasi-dimensional multi-zone model for a direct injection compression ignition (DICI) engine. The objective is to develop fuel sensitive sub models of the DICI combustion process and integrate them into a thermodynamic engine cycle simulation. The proposed spray and evaporation models comprise the sub-models including fuel sensitive spray breakup, improved zone velocity estimations with transient fuel injection, spray penetration and tracking of evaporated fuel components. On these foundations, ignition delay models are formulated with two different descriptions based on the origin of the charge properties in a DICI engine. The global ignition delay model is based on the global combustion chamber charge properties while the local ignition delay model includes variations in properties of each spray zones. The Cetane number is used to describe a fuel effect for both models. Then, the premixed combustion model is reformulated to calculate a proper burn rate profile with respect to equivalence ratio and scale the profile with diluted air. While the developed models are validated and evaluated by comparing the predictions with experimental data, some of important conclusions have been made. In the spray formation model, the degree of viscosity and surface tension effect on the spray formation and air entrainment is much more pronounced with DME fuel. For the fuels closer to the conventional DF2, the effect of those properties is minimal. The evaporation model includes the behavior of evaporation at high pressure. The rate of evaporation is usually suppressed with higher pressure but at lower temperature than typical engine-like conditions, the effect is inverted. This effect might be significant for the low temperature combustion. Of the two proposed ignition delay models the local model has a slightly better accuracy compared to the global model. The results demonstrate the improvements that can be obtained when additional fuel specific properties are included in the spray ignition model. Although the proposed fuel sensitive combustion model calculates fuel effect to the combustion, the effect of ignition delay to the overall result of engine cycle simulation was much more dominant with given fuels in this study.

Published
2014

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