A wall-adapted zonal URANS/LES methodology for the scale-resolving simulation of engine flows

2021 ◽  
pp. 146808742110323
Author(s):  
Clara Iacovano ◽  
Alessandro d’Adamo ◽  
Stefano Fontanesi ◽  
Giovanni Di Ilio ◽  
Vesselin Krassimirov Krastev
Keyword(s):  
Turbulence Modeling ◽  
Direct Injection ◽  
Thermal Power ◽  
Specific Flow ◽  
Direct Injection Engines ◽  
Optical Engine ◽  
Cycle Simulation ◽  
Flow Features ◽  
Mesh Resolution ◽  
Near Wall

In the present paper, a comprehensive, wall-adapted zonal URANS/LES methodology is shown for the multidimensional simulation of modern direct-injection engines. This work is the latest update of a zonal hybrid turbulence modeling approach, specifically developed by the authors for a flexible description of in-cylinder turbulent flow features with an optimal balance between computational costs and accuracy. Compared to the previous developments, a specific near-wall treatment is added, in order to preserve full-URANS behavior in the first near-wall cells, having in mind typically available mesh resolution in this part of the fluid domain. The updated methodology is applied to the multi-cycle simulation of a reference single-cylinder optical engine, which features a twin-cam, overhead-valve pent-roof cylinder head, and is representative of the current generation of spark-ignited direct-injection thermal power units. Results based on phase-specific flow field statistics and synthetic quality indices demonstrate the consistency and effectiveness of the proposed methodology, which is then qualified as a suitable candidate for affordable scale-resolving analyses of cycle to cycle variability (CCV) phenomena in direct-injection engines.

Low-speed pre-ignition in gasoline, turbo-charged, direct injection engines: An analysis of engine testing data

2018 ◽  
Author(s):  
Andrew Harvey ◽  
Guillaume DeSercey ◽  
Morgan Heikal ◽  
Steven Begg ◽  
Richard Osborne
Keyword(s):  
Direct Injection ◽  
Direct Injection Engines ◽  
Low Speed ◽  
Testing Data ◽  
Engine Testing

Modular Turbulence Modeling Applied to an Engine Intake

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Ugochukwu R. Oriji ◽  
Paul G. Tucker
Keyword(s):  
Surface Roughness ◽  
Turbulence Modeling ◽  
Fluid Dynamic ◽  
Navier Stokes ◽  
Test Cases ◽  
Laminar Separation ◽  
Streamline Curvature ◽  
Favorable Pressure Gradient ◽  
Flow Features ◽  
The One

The one equation Spalart–Allmaras (SA) turbulence model in an extended modular form is presented. It is employed for the prediction of crosswind flow around the lip of a 90 deg sector of an intake with and without surface roughness. The flow features around the lip are complex. There exists a region of high streamline curvature. For this, the Richardson number would suggest complete degeneration to laminar flow. Also, there are regions of high favorable pressure gradient (FPG) sufficient to laminarize a turbulent boundary layer (BL). This is all terminated by a shock and followed by a laminar separation. Under these severe conditions, the SA model is insensitive to capturing the effects of laminarization and the reenergization of eddy viscosity. The latter promotes the momentum transfer and correct reattachment prior to the fan face. Through distinct modules, the SA model has been modified to account for the effect of laminarization and separation induced transition. The modules have been implemented in the Rolls-Royce HYDRA computational fluid dynamic (CFD) solver. They have been validated over a number of experimental test cases involving laminarization and also surface roughness. The validated modules are finally applied in unsteady Reynolds-averaged Navier–Stokes (URANS) mode to flow around an engine intake and comparisons made with measurements. Encouraging agreement is found and hence advances made towards a more reliable intake design framework.

scholarly journals Mixedness Measurement in Gaseous Jet Injection

2017 ◽  
Author(s):  
Martia Shahsavan ◽  
John Hunter Mack
Keyword(s):  
Combustion Chamber ◽  
Direct Injection ◽  
Premixed Combustion ◽  
Working Fluid ◽  
Scalar Dissipation ◽  
Jet Injection ◽  
Direct Injection Engines ◽  
Comprehensive Method ◽  
Mixture Homogeneity ◽  
Crucial Parameter

In turbulent non-premixed combustion applications, such as diesel and direct injection engines, the mixedness of the injected fuel with oxygen and the working fluid inside the combustion chamber is a crucial parameter since it can significantly affect the ignition behavior. In this study, a comprehensive method for investigating mixedness, defined by spatial variation and scalar dissipation, is implemented to assess the turbulent injection of hydrogen into mixture of oxygen with nitrogen, argon, and xenon. Evaluating both criteria reflects the mixture homogeneity as well as local gradients, which aids in discriminating scalar distributions with identical homogeneity and different patterns. The results indicate that replacing nitrogen with argon as the working fluid can provide more suitable ignition conditions for the hydrogen jet.

scholarly journals Experimental Study of Ceramic Coated Piston Crown for Compressed Natural Gas Direct Injection Engines

2013 ◽  
Vol 68 ◽  
pp. 505-511 ◽  
Author(s):  
Helmisyah Ahmad Jalaludin ◽  
Shahrir Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Bulan Abdullah ◽  
Nik Rosli Abdullah
Keyword(s):  
Experimental Study ◽  
Natural Gas ◽  
Direct Injection ◽  
Compressed Natural Gas ◽  
Direct Injection Engines ◽  
Piston Crown

Highly resolved experimental results of the separated flow in a channel with streamwise periodic constrictions

2016 ◽  
Vol 796 ◽  
pp. 257-284 ◽  
Author(s):  
Christian J. Kähler ◽  
Sven Scharnowski ◽  
Christian Cierpka
Keyword(s):  
Turbulent Flow ◽  
Flow Separation ◽  
Flow Direction ◽  
Separated Flow ◽  
Mean Flow ◽  
Complex Flow ◽  
Flow Measurements ◽  
Flow Features ◽  
Wall Flow ◽  
Near Wall

The understanding and accurate prediction of turbulent flow separation on smooth surfaces is still a challenging task because the separation and the reattachment locations are not fixed in space and time. Consequently, reliable experimental data are essential for the validation of numerical flow simulations and the characterization and analysis of the complex flow physics. However, the uncertainty of the existing near-wall flow measurements make a precise analysis of the near-wall flow features, such as separation/reattachment locations and other predicted near-wall flow features which are under debate, often impossible. Therefore, the periodic hill experiment at TU Munich (ERCOFTAC test case 81) was repeated using high resolution particle image velocimetry and particle tracking velocimetry. The results confirm the strong effect of the spatial resolution on the near-wall flow statistics. Furthermore, it is shown that statistically stable values of the turbulent flow variables can only be obtained for averaging times which are challenging to realize with highly resolved large eddy simulation and direct numerical simulation techniques. Additionally, the analysis implies that regions of correlated velocity fluctuations with rather uniform streamwise momentum exist in the flow. Their size in the mean flow direction can be larger than the hill spacing. The possible impact of the correlated turbulent motion on the wake region is discussed, as this interaction might be important for the understanding and control of the flow separation dynamics on smooth bodies.

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