Development of a K-k-∊ Phenomenological Model to Predict In-Cylinder Turbulence

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Authors Abstract
The turbulent flow field inside the cylinder plays a major role in spark ignition (SI) engines. Multiple phenomena that occur during the high pressure part of the engine cycle, such as early flame kernel development, flame propagation and gas-to-wall heat transfer, are influenced by in-cylinder turbulence. Turbulence inside the cylinder is primarily generated via high shear flows that occur during the intake process, via high velocity injection sprays and by the destruction of macro-scale motions produced by tumbling and/or swirling structures close to top dead center (TDC) . Understanding such complex flow phenomena typically requires detailed 3D-CFD simulations. Such calculations are computationally very expensive and are typically carried out for a limited number of operating conditions. On the other hand, quasi-dimensional simulations, which provide a limited description of the in-cylinder processes, are computationally inexpensive. They require only a small fraction of the computational resources needed for CFD calculations and can be carried out for a large number of cases. Such simulations typically use zero dimensional (0D) phenomenological sub-models to simulate the various in-cylinder phenomena such as heat transfer, combustion, flow variations etc.
The current study presents a newly developed sub-model, available as a part of the software GT-SUITE, which governs the evolution of the mean and turbulent flow inside the cylinder. Within a 0D context, the accurate knowledge of in-cylinder turbulence levels close to ignition is essential to reliably model turbulent flame propagation. However, engines running with stratified charge and/or early spark timings also require the accurate estimation of turbulence levels over the intake and compression strokes. The new model aims to accurately predict in-cylinder turbulence levels over the entire engine cycle. It utilizes a K-k- approach, where K and k are the mean and turbulent kinetic energy and is the turbulent dissipation rate. The study shows that the model, once calibrated for a particular engine using 3D-CFD results, has the capability to predict the temporal evolution of in-cylinder flow quantities and also responds well to changes in the operating conditions of the engine such as variations in speed, valve lift and timing.
Meta TagsDetails
Fogla, N., Bybee, M., Mirzaeian, M., Millo, F. et al., "Development of a K-k-∊ Phenomenological Model to Predict In-Cylinder Turbulence," Engines 10(2):562-575, 2017,
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Mar 28, 2017
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Journal Article