Numerical Investigation of Flow through a Valve during Charge Intake in a DISI -Engine Using Large Eddy Simulation

Abstract

Apart from electric vehicles, most internal combustion (IC) engines are powered while burning petroleum-based fossil or alternative fuels after mixing with inducted air. Thereby the operations of mixing and combustion evolve in a turbulent flow environment created during the intake phase and then intensified by the piston motion and influenced by the shape of combustion chamber. In particular, the swirl and turbulence levels existing immediately before and during combustion affect the evolution of these processes and determine engine performance, noise and pollutant emissions. Both the turbulence characteristics and the bulk flow pattern in the cylinder are strongly affected by the inlet port and valve design. In the present paper, large eddy simulation (LES) is appraised and applied to studying the turbulent fluid flow around the intake valve of a single cylinder IC-engine as represented by the so called magnetic resonance velocimetry (MRV) flow bench configuration with a relatively large Reynolds number of 45,000. To avoid an intense mesh refinement near the wall, various subgrid scale models for LES; namely the Smagorinsky, wall adapting local eddy (WALE) model, SIGMA, and dynamic one equation models, are employed in combination with an appropriate wall function. For comparison purposes, the standard RANS (Reynolds-averaged Navier–Stokes) k- ε model is also used. In terms of a global mean error index for the velocity results obtained from all the models, at first it turns out that all the subgrid models show similar predictive capability except the Smagorinsky model, while the standard k- ε model experiences a higher normalized mean absolute error (nMAE) of velocity once compared with MRV data. Secondly, based on the cost-accuracy criteria, the WALE model is used with a fine mesh of ≈39 millions control volumes, the averaged velocity results showed excellent agreement between LES and MRV measurements, revealing the high prediction capability of the suggested LES tool for valve flows. Thirdly, the turbulent flow across the valve curtain clearly featured a back flow resulting in a high speed intake jet in the middle. Comprehensive LES data are generated to carry out statistical analysis in terms of (1) evolution of the turbulent morphology across the valve passage relying on the flow anisotropy map, (2) integral turbulent scales along the intake-charge stream, (3) turbulent flow properties such as turbulent kinetic energy, turbulent velocity and its intensity within the most critical zone in intake-port and along the port length, it further transpires that the most turbulence are generated across the valve passage and these are responsible for the in-cylinder turbulence.

Evaluation of a Near-Wall-Modeled Large Eddy Lattice Boltzmann Method for the Analysis of Complex Flows Relevant to IC Engines

“…Recent studies examined intake phenomena using magnetic resonance velocimetry (MRV) in a steady water flow bench [1] or low-speed particle image velocimetry (PIV) in a steady air flow bench [14,15]. The data from these experiments have been used as validation for large eddy simulation (LES) approaches [14][15][16][17][18].…”

Experimental Investigation on the High-frequency Pressure Oscillation Characteristics of a Combustion Process in a DI Diesel Engine

“…Apart from experimental research on pressure oscillation, some work has been done to calculate and simulate the cylinder pressure oscillation and describe the in-cylinder combustion process [14,30,31]. Torregrosa and Broatch et al [14] proposed a numerical calculation method that used the noise caused by the combustion process of a diesel engine to overcome the experimental limits.…”

“…Wei et al [30] predicted the wave equations for the coupling of pressure fluctuations in the combustion process of diesel engines with the Kiva program. Kaushal et al [31] used large eddy simulation (LES) to study the turbulent fluid flow around the intake valve of a single cylinder IC-engine, and found that the LES tool revealed high prediction capability of the simulation of valve flows. As a consequence, all of these simulation methods above have obtained combustion resonance to a certain extent.…”

A Wall-Adapted Anisotropic Heat Flux Model for Large Eddy Simulations of Complex Turbulent Thermal Flows

“…On the numerical side, large eddy simulation (LES) technique has proved to be a promising approach to predict complex heat and fluid flow phenomena in many thermo-fluid systems, likewise in automotive applications (Nishad et al 2019;Hasse et al 2010;Nishad et al 2012;Goryntsev et al 2014;Rutland 2011;Goryntsev et al 2010). In LES, the large three-dimensional unsteady turbulent motions are explicitly computed, whilst a turbulence closure model accounts for the influence of the unresolved more universal scales (Klein 2008;Sagaut 2006;Pope 2009).…”