Abstract
A collaborative effort is described to benchmark the TCC-III engine, and to illustrate the application of this data for the evaluation of sub-grid scale models and valve simulation details on the fidelity of Large-Eddy Simulations (LES). The TCC-III is a spark ignition 4-stroke 2-valve engine with a flat head and piston and is equipped with a full quartz liner for maximum optical access that allows high-speed flow measurements with Particle Image Velocimetry (PIV); the TCC-III has new valve seats and a modified intake-system compared to previous configurations. This work is an extension of a previous study at an engine speed of 800 RPM and an intake manifold pressure (MAP) of 95 kPa, where a one-equation eddy viscosity LES model yielded accurate qualitative and quantitative predictions of ensemble averaged mean and RMS velocities during the intake and compression stroke. Here, experimental data were acquired with parametric variation of engine speed and intake manifold absolute pressure to assess the capability of LES models over a range of operating conditions of practical relevance. This paper focuses on the repeatability and accuracy of the measured PIV data, acquired at 1 300 RPM, at two different MAP (95 kPa and 40 kPa), and imaged at multiple data planes and crank angles. Two examples are provided, illustrating the application of this data to LES model development. In one example, the experimental data are used to distinguish between the efficacies of a one-equation eddy viscosity model versus a dynamic structure one-equation model for the sub-grid stresses. The second example addresses the effects of numerical intake-valve opening strategy and local mesh refinement in the valve curtain.
Highlights
Reynolds-Average Navier Stokes (RANS) simulation of reciprocating Internal Combustion Engine (ICE) combustion has matured to be a valuable tool for engineering design
Two operating conditions will be highlighted here to illustrate how changes in intake manifold pressure affect the filling dynamics of the cylinder and how the simulations pick up this process
Encouraging results that point to this lead to investigations of increasing the mesh resolution around the valves to better capture the dynamics of the valve opening and closing events; this resulted in higher accuracy for the numerical nature of valving events in CFD
Summary
Reynolds-Average Navier Stokes (RANS) simulation of reciprocating Internal Combustion Engine (ICE) combustion has matured to be a valuable tool for engineering design. LES has been used to simulate flow and combustion in modern engine concepts such as four-valve pent-roof spark-ignition, Diesel, and HCCI engines [3,4,5,6,7,8,9]. The accuracy of the sub-grid-models (Sub-GridScale, SGS), the numerical schemes in use, and more, have an impact on how well the in-cylinder processes can be simulated These computations rely on accurate experimental data to identify the underlying physics and benchmark the simulation results. With accurate and repeatable experimental data is it possible to achieve a meaningful assessment and validation of the simulations With this purpose in mind, the Transparent Combustion Chamber (TCC-0) engine was originally designed (circa 1990), built, and used for more fundamental investigations of the in-cylinder flow and combustion CCV using the nascent Particle Image Velocimetry (PIV). Complementing the more recent LES calculations noted above, there are experimental data available from measurements within motored and fired four-valve pent roof engines [11, 12]
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