Large eddy simulations of in-cylinder turbulence for internal combustion engines: A review

Abstract

While engineering applications of the large eddy simulation (LES) technique are becoming a common reality in many branches of engineering and science, its application to engine flows has lagged behind due to the relatively more complex nature of both the flow and the geometry relevant to in-cylinder flows. In this paper a review of the limited number of LES applications to engine flows is given, and most significant results from these studies are presented. Also, the LES formulation appropriate for engine applications is briefly described, along with the main characteristics of in-cylinder flows. As expected, engine applications of LES are not of the so-called ‘high-fidelity’ type, but rather they employ formally second-order accurate numerical schemes in conjunction with finite volume formulation. The subgrid scale (SGS) models used are also kept as simple as possible, mostly using a variant of the Smagorinsky model. Nevertheless, this review reveals that even with relatively coarse grids, LES captures much more interesting features of in-cylinder flows, such as the large coherent vortical flow structures developed during the intake stroke. In the opinion of the present authors, a low-resolution LES provides a better solution than RANS (Reynolds averaged Navier-Stokes) with moderate grid resolution because the important features of flow dynamics cannot be reproduced in RANS due to the high level of non-physical diffusion. Of course, some overheads in computational costs must be paid for this benefit obtained from LES.

Evaluating Large-Eddy Simulation (LES) and High-Speed Particle Image Velocimetry (PIV) with Phase-Invariant Proper Orthogonal Decomposition (POD)

“…Early reviews of LES applications to IC engines include Celik et al [17] and Haworth [14]. Early LES attempts on IC engines were limited to simple engine configurations; these works include LES for a simplified motored engine configuration by Haworth and Jansen [16], a study of turbulence statistics for a motored engine configuration by Celik et al [18,19], turbulent premixed-flame propaga- tion in IC engines on relatively coarse grids by Naitoh et al [20], and LES of Diesel fuel injection and combustion by Smirnov et al [21] and Smith et al [22].…”

Towards Large Eddy Simulation in Internal-Combustion Engines: Simulation of a Compressed Tumble Flow

“…A better candidate for a tool allowing to predict them are Large Eddy Simulation (LES) techniques. These techniques have proven their great potential when applied to the prediction of acoustic instability in gas turbine combustion chambers [9], and they start to be developed for piston engine applications as discussed by Celik et al [4].…”

The Study of Turbulent Fluctuation Characteristics in a Small Rotary Engine with a Peripheral Port Based on the Improved Delayed Detached Eddy Simulation Shear-Stress Transport (IDDES-SST) Method

“…For numerical simulation, the transient turbulent characteristics of the conventional reciprocating engine have already been investigated through large eddy simulation (LES) [8][9][10][11]. Although LES is considered a high-fidelity method, it requires a huge amount of computational expense [12].…”