This content is not included in your SAE MOBILUS subscription, or you are not logged in.
An Experimental Assessment of Turbulence Production, Reynolds Stress and Length Scale (Dissipation) Modeling in a Swirl-Supported DI Diesel Engine
ISSN: 0148-7191, e-ISSN: 2688-3627
Published March 03, 2003 by SAE International in United States
Annotation ability available
Simultaneous measurements of the radial and the tangential components of velocity are obtained in a high-speed, direct-injection diesel engine typical of automotive applications. Results are presented for engine operation with fuel injection, but without combustion, for three different swirl ratios and four injection pressures. With the mean and fluctuating velocities, the r-θ plane shear stress and the mean flow gradients are obtained. Longitudinal and transverse length scales are also estimated via Taylor's hypothesis. The flow is shown to be sufficiently homogeneous and stationary to obtain meaningful length scale estimates. Concurrently, the flow and injection processes are simulated with KIVA-3V employing a RNG k-ε turbulence model.
The measured turbulent kinetic energy k, r-θ plane mean strain rates ( 〈Srθ〉, 〈Srr〉, and 〈Sθθ〉 ), deviatoric turbulent stresses , and the r-θ plane turbulence production terms are compared directly to the simulated results. The model predicts the qualitative trends in k well, but under-predicts the magnitude of the late-cycle turbulence at the higher swirl ratios. The mean strain rates, turbulent stresses, and turbulence production terms generally agree qualitatively. Both the experimental and the simulated results indicate that redistribution of the mean flow angular momentum by the fuel injection event is an important source of late-cycle turbulence. This redistribution enhances r-θ plane turbulence production at low swirl ratios through formation of unstable mean flow distributions with negative radial gradients in mean flow angular momentum. Additionally, r-z plane vortical flow structures are formed by a competition between the inward displacement of high angular momentum fluid by the fuel jets and the centrifugal forces acting to force the high momentum fluid back to the bowl periphery. Model results indicate that these flow structures can also be important sources of turbulence at higher swirl ratios.
The measured length scales, mean strain rates, and turbulent kinetic energy are used to assess directly the validity of the isotropic eddy viscosity hypothesis. This modeling hypothesis is found to provide good estimates of and , despite the high levels of flow swirl. However, the data indicate that the modeled is underestimated when unstable mean flow distributions exist. Further, under some conditions, no model based solely on local flow properties is likely to predict the measured . Poor agreement is found between the measured and modeled .
The under-prediction of k at high swirl, coupled with the generally good agreement in 〈Srθ〉, , and Prθ, suggest that the under-prediction of k is predominantly due to an over-estimation of ε after the injection event. This suggestion is further supported by a comparison of the temporal evolution of the measured and modeled length scales.
CitationMiles, P., Megerle, M., Nagel, Z., Reitz, R. et al., "An Experimental Assessment of Turbulence Production, Reynolds Stress and Length Scale (Dissipation) Modeling in a Swirl-Supported DI Diesel Engine," SAE Technical Paper 2003-01-1072, 2003, https://doi.org/10.4271/2003-01-1072.
Computer Aided Engineering of Vehicle & Engine Systems & Components
Number: SP-1740; Published: 2003-03-03
Number: SP-1740; Published: 2003-03-03
- Miles, P. Megerle, M. Sick, V. Richards, K. Nagel, Z. Reitz, R. “The Evolution of Flow Structures and Turbulence in a Fired HSDI Diesel Engine,” SAE Paper No. 2001-01-3501 2001
- Miles, P. Megerle, M. Hammer, J. Nagel, Z. Reitz, R.D. Sick, V. “Late-Cycle Turbulence Generation in Swirl-Supported, Direct-Injection Diesel Engines,” SAE Paper No. 2002-01-0891 2002
- Miles, P.C. Megerle, M. Nagel, Z. Liu, Y. Reitz, R.D. Lai, M.-C. Sick, V. “The Influence of Swirl and Injection Pressure on Post-Combustion Turbulence in a HSDI Diesel Engine,” Proc. of Thermo- and Fluid-Dynamic Processes in Diesel Engines Valencia, Spain Sept. 10-13 2002
- Miles, P.C. Megerle, M. Nagel, Z. Reitz, R.D. Sick, V. “Measurements and Modeling of Reynolds Stress and Turbulence Production in a Swirl-Supported, Direct-Injection Diesel Engine,” Proc. 29 th Intl. Symp. on Combustion July 21-26 Sapporo, Japan 2002
- Han, Z. Reitz, R.D. “Turbulence Modeling of Internal Combustion Engines Using RNG k-ε Models,” Combust. Sci. and Tech. 106 267 295 1995
- Kong, S.-C. Han, Z. Reitz, R.D. “The Development and Application of a Diesel Ignition and Combustion Model for Multidimensional Engine Simulation,” SAE Paper No. 950278 Trans. SAE 104 1995
- Fansler, T.D. French, D.T. “Cycle-Resolved Laser-Velocimetry Measurements in a Reentrant-Bowl-in-Piston Engine,” SAE Paper No. 880377 Trans. SAE 97 1988
- Valentino, G. Auriemma, M. Corcione, F.E. Macchioni, R. Seccia, G. “Evaluation of Time and Spatial Scales in a DI Diesel Engine,” 8 th Intl. Symp. On Appl. Of Laser Tech. To Fluid Mech. Lisbon, Portugal July 8-11 1996
- Lumley, J.L. Engines: An Introduction Cambridge University Press 1999
- Tennekes, H. Lumley, J.L. A First Course in Turbulence MIT Press 1972
- Hinze, J.O. Turbulence McGraw-Hill 1959
- Ikegami, M. Shioji, M. Nishimoto, K. “Turbulence Intensity and Spatial Integral Scale During Compression and Expansion Strokes in a Four-Cycle Reciprocating Engine,” SAE Paper No. 870372 SAE Trans. 96 1987
- Fraser, R.A. Bracco, F.V. “Cycle-Resolved Integral Length Scale Measurements in an I.C. Engine SAE Paper No. 880381 SAE Trans. 97 1988
- Fraser, R.A. Bracco, F.V. “Cycle-Resolved LDV Integral Length Scale Measurements Investigating Clearance Height Scaling, Isotropy, and Homogeneity in an I.C. Engine SAE Paper No. 890615 SAE Trans. 98 1989
- Comte-Bellot, G. Corrsin, S. “Simple-Eulerian Time Correlation of Full- and Narrow-Band Velocity Signals in Grid-Generated, ‘Isotropic’ Turbulence,” J. Fluid Mech. 48 273 337 1971
- Amsden, A.A. O'Rourke, P.J. Butler, T.D. “KIVA-II: A computer Program for Chemically Reactive Flows with Sprays,” Los Alamos National Laboratory Technical Report LA-11560-MS 1989
- Han, Z. Reitz, R.D. Corcione, F.E. Valentino, G. “Interpretation of k-ε Computed Turbulence Length Scale Predictions for Engine Flows,” Proc. 26 th Intl. Symp. on Combustion 2717 2723 The Combustion Institute 1996
- Kaario, O. Larmi, M. Tanner, F. “Relating Integral Length Scale to Turbulent Time Scale and Comparing k-ε and RNG k-ε Turbulence Models in Combustion Simulation,” SAE Paper No. 2002-01-1117 2002