Correlation of CCV Between In-Cylinder Swirl Ratio and Polar Velocity Profile in Valve Seat Region Using LES Under Motored Engine Condition

Abstract

-An analysis of Transparent Combustion Chamber (TCC3) engine Large-Eddy Simulation (LES) result was carried out to investigate Cycle-to-Cycle Variation (CCV) correlation between incylinder swirl ratio and flow in the valve seat region of the intake port to address a challenging question on "What causes CCV of in-cylinder flow". Polar Velocity (PV) profile, mean velocities normal to a ringshaped cutting surface in the valve seat region, is calculated to depict intake port flow. A Net Polar Velocity (NPV) can be defined by performing the vector sum of the polar velocity around the intake valve. A standard deviation of PV is also calculated from azimuthal distribution of PV magnitudes relative to its mean value. The analysis of 18 LES cycles of TCC3 engine with a two-valve, pancake-shaped combustion chamber shows that similar CCV of in-cylinder swirl ratio patterns are observed at different crank angles from Intake Valve Opening (IVO) to Exhaust Valve Opening (EVO). Further analysis shows clear correlations of CCV between in-cylinder swirl ratio and NPV magnitude and the standard deviation of PV at selected crank angles from IVO to EVO. The correlations get significantly better with the ring-shaped cutting surface moves from up-stream to downstream of the valve-seat region. This study reveals that the CCV of in-cylinder swirl ratio is built up gradually from upstream to downstream in the intake port and valve-seat region. Further evaluation of the analysis method is planned for a four-valve engine as an evaluation metric for better engine intake port design and combustion chamber optimization.

Methodology for the large-eddy simulation and particle image velocimetry analysis of large-scale flow structures on TCC-III engine under motored condition

“…Abraham et al 18 conducted LES and experimental research to investigate flow patterns to find the causes of the CCV. Yang and Kuo 19 investigated the CCV correlation between the swirl ratio and valve curtain flow. From a numerical standpoint, Ko et al 20 investigated the influence of the grid density of the intake system on the flow CCV.…”

Multi-plane time-resolved Particle Image Velocimetry (PIV) flow field measurements in an optical Spark-Ignition Direct-Injection (SIDI) engine for Large-Eddy Simulation (LES) model validations

“…However, the nature of in-cylinder flow fields is highly complex and cyclic which have not yet been thoroughly investigated. To elucidate these characteristics, Large-Eddy Simulation (LES) has been applied to simulate the in-cylinder flow fields and quantify the cyclic variations of engine flows under motoring or firing operations [1][2][3][4][5]. The high temporal evolution of the flow fields predicted by LES results improves the understanding of critical in-cylinder process with time-resolved information.…”

“…In order to construct reliable LES models, the simulation results of in-cylinder flow fields with high temporal and spatial resolutions are commonly validated with highspeed Particle Image Velocimetry (PIV) data [4][5][6][7]. In most research, planar PIV is used to measure the flow fields to validate the LES model by focusing only on the velocity comparison on a specific plane [8,9] or a targeted spatial zone or location near the intake valve [5,10]. When comparing the velocity results between PIV and LES, the Relevance Index (RI) is commonly used.…”

IFP Energies nouvelles International Conference

“…Finally X. Yang and T-W. Kuo [7] used LES of flow inside a motored research single cylinder engine to study the correlation between cyclic variability of the swirl generated by intake and compression and the variability of the intake valve curtain flow.…”