Comparison of Linear, Non-Linear and Generalized RNG-Based k-epsilon Models for Turbulent Diesel Engine Flows

Abstract

In this work, linear, non-linear and a generalized renormalization group (RNG) two-equation RANS turbulence models of the k-epsilon form were compared for the prediction of turbulent compressible flows in diesel engines. The objectoriented, multidimensional parallel code FRESCO, developed at the University of Wisconsin, was used to test the alternative models versus the standard k-epsilon model. Test cases featured the academic backward facing step and the impinging gas jet in a quiescent chamber. Diesel engine flows featured high-pressure spray injection in a constant volume vessel from the Engine Combustion Network (ECN), as well as intake flows in a high-swirl diesel engine. For the engine intake flows, a model of the Sandia National Laboratories 1.9L light-duty single cylinder optical engine was used. An extensive experimental campaign provided validation data in terms of ensemble averages of planar PIV measurements at different vertical locations in the combustion chamber, for different swirl ratio configurations during both the intake and the compression strokes. The generalized RNG k-epsilon model provided the best accuracy trade-off for both swirl and shear flows, thanks to the polynomial expansion of coefficients C1 and C2 in the RNG kepsilon model with an effective 'dimensionality' of the strain rate field. Similar performance was seen across linear and nonlinear RNG models, which achieves good prediction of incylinder swirl flows; however, they noticeably underpredict jet penetration in the case of high-pressure sprays, suggesting the additional computational cost and lower stability of the nonlinear model do not justify greater suitability for engine calculations.

Numerical Simulation of Heat-and-Mass Transfer Processes in the Cooling Passages of a Cylinder Head in a Diesel Locomotive Engine

“…Many researchers have been investigating heat-andmass transfer processes in ICE and in the cylinder head cooling passages [6][7][8][9][10][11][12]. Studies [6][7][8] present the methodology and results of numerical simulation of heat-andmass transfer in the cooling jackets of single and individual ICE cylinder heads.…”

“…Using CFD software packages enables 3D simulation of viscous and turbulent flows of the coolant in the ICE cooling system. To model turbulent coolant flow, studies [6][7][8] recommend using the k-ε turbulence model. It enables simulating turbulent flows with high accuracy in the case of liquid flow in complex-shape passages.…”

“…The Woschni formula is used [6][7][8] to investigate the in-cylinder heat balance, calculate the values of the gas-towall heat transfer coefficients and evaluate the changes in the thermal load on the cylinder head with changing diesel engine running conditions.…”

Prospects of Using Steel Pistons in Transport Diesel Engines

“…Using advanced numerical methods for investigating the processes of injection, carburation, combustion and formation of toxic components in the engine cylinder enables investigating the processes inside the diesel engine cylinder and work out recommendations to improve the engine's indicators with a high level of information content and validity (Cursente et al, 2008;Ranjbar et al, 2009;Perini et al, 2017;Dolak and Reitz 2011;Munnannur et al, 2006;Ra et al, 2006;Genzale et al, 2008).…”

Selecting a k-ε turbulence model for investigating n-decane combustion in a diesel engine combustion chamber

“…The development of numerical simulation techniques makes it possible to simulate combustion and the formation of toxic substances in an engine cylinder with a high level of accuracy and confidence [1,2] Advanced software packages serve for simulating the processes of mixture formation, combustion and formation of toxic substances in the plane axisymmetric and three-dimensional statements [6][7][8]. Chemical mechanisms, for instance, those implemented in the CHEMKIN package, are used for a detailed description of fuel combustion kinetics [9].…”