Assessment of a zero‐dimensional model of tumble in four‐valve high performance engine

Abstract

PurposeThe purpose of this paper is to assess a phenomenological zero‐dimensional model (0‐D model) in order to evaluate both the in‐cylinder tumble motion and turbulence in high‐performance engine, focusing on the capability and sensitivity of the model.Design/methodology/approachThe study was performed using a four‐valve pentroof engine, testing two different intake ports. The first one was a conventional port and the second one was design in such a way to promote tumble. CFD simulations for admission and compression strokes under different engine conditions were carried out. Then, the in‐cylinder entrance mass and mean velocities from CFD were imposed as boundary conditions in the 0‐D model.FindingsMarked discrepancies between 0‐D model and CFD results were found. As expected, for the original port, CFD results displayed a poor tumble generation during the admission period. It was followed by a fast degradation of the tumble momentum along the compression stroke due to it was not dominant over the other two momentum components. 0‐D model overestimated the entrance‐tumble but underestimated the vortex degradation along the compression stroke, resulting in higher tumble predictions, thereby it is not recommended for low‐tumble engines. As for the modified port, 0‐D model assumptions were closer to the in‐cylinder flow field from CFD, but results underestimated the entrance‐tumble during the intake stroke and predicted excessive tumble at the end of the compression stroke. Summarizing, 0‐D model neither showed sensitivity to changes in the intake port because of the scarce information about the entrance‐flow field nor it was not suitable to evaluate the tumble degradation.Originality/valueThe limitations of the current model were highlighted, given possible guidelines in order to improve it.

A New Physics-Based Modeling Approach for a 0D Turbulence Model to Reflect the Intake Port and Chamber Geometries and the Corresponding Flow Structures in High-Tumble Spark-Ignition Engines

“…In several previous researches on tumble modeling found in literature, a 2D linear velocity profile is assumed to represent the flow field inside the cylinder [5,20,21]. These studies postulated that boundary velocities at the top, bottom, and wall side are all equal regardless of the piston position, which the authors suspect to be inconsistent with the real situation.…”

In-cylinder flow control in a four-valve spark ignition engine: numerical and experimental steady rig tests

“…gravity). Turbulence was modelled through a standard k-e model, which is commonly employed for performing steady and dynamic engine simulations [3,7,[12][13][14][15]. The transport equations for the turbulent kinetic energy k and the turbulence dissipation rate e are Swirl.…”

“…It is clear that the full swirl strategy would not be suitable at high load and high engine speed. The conservation of high tumble from the intake stroke until the end of the compression stroke can be related to the shape and intensity of the macro vortex of tumble [1,15,26]. In this sense, the conservation of swirl motion is promoted by the cylinder shape [27].…”

Refinement of a 0D Turbulence Model to Predict Tumble and Turbulent Intensity in SI Engines. Part II: Model Concept, Validation and Discussion

“…A simplified methodology is proposed in [15], where a linear decrease of the tumble vortex is imposed as a function of the piston distance from the cylinder head. In [16,17], more physical tumble models are introduced, capable of considering the geometry of the intake system, and the valve and the cylinder port inclination. In [18], a model is developed, describing both tumble and swirl motions, and their dissipation in turbulence.…”