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Study on Relationship Between Turbulent Burning Velocity and Karlovitz Number Under EGR Conditions
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on September 15, 2020 by SAE International in United States
The purpose of this paper is to find a universal law to predict a turbulent burning velocity under various operating conditions and engine specifications. This paper presents the relationship between turbulent burning velocity and Karlovitz number. The turbulent burning velocity was measured using a single-cylinder gasoline engine, which has an external-exhaust gas recirculation (EGR) system. In the experiment, various engine operating parameters, such as engine speed, EGR rate and various engine specifications, which mean different types of intake ports were tested. Karlovitz number was calculated with three dimensional computational fluid dynamics (3D-CFD) and detailed chemical reaction calculation, which calculation condition was based on the experiment. The experimental and calculation result shows that turbulent burning velocity is predicted by using Karlovitz number in the engine conditions, which burning velocity varies depending on engine speed, EGR rate and the designs of intake ports. The results indicate that Karlovitz number, which shows a local behavior of flame and corresponds to the ratio of chemical time scale and turbulent time scale, can be extended to an indicator of the global combustion performance in engine.