Principal Component Analysis and Study of Port-Induced Swirl Structures in a Light-Duty Optical Diesel Engine

Abstract

In this work computational and experimental approaches are combined to characterize in-cylinder flow structures and local flow field properties during operation of the Sandia 1.9L light-duty optical Diesel engine. A full computational model of the single-cylinder research engine was used that considers the complete intake and exhaust runners and plenums, as well as the adjustable throttling devices used in the experiments to obtain different swirl ratios. The in-cylinder flow predictions were validated against an extensive set of planar PIV measurements at different vertical locations in the combustion chamber for different swirl ratio configurations. Principal Component Analysis was used to characterize precession, tilting and eccentricity, and regional averages of the in-cylinder turbulence properties in the squish region and the piston bowl. Complete sweeps of the port throttle configurations were run to study their effects on the flow structure, together with their correlation with the swirl ratio. Significant deviations between the flows in the piston bowl and squish regions were observed. Piston bowl design, more than the swirl ratio, was identified to foster flow homogeneity between these two regions. Also, analysis of the port-induced flow showed that port geometry, more than different intake port mass flow ratios, can improve turbulence levels in-cylinder.

Evaluation of the flame propagation within an SI engine using flame imaging and LES

“…The corresponding databases have provided a stronghold for engine simulations with regards to model validation and development. Together, experimental and (RANS-) modeling studies have jointly addressed studies of flow cycle-to-cycle variations (ccv) [14,23], sprays [15], ignition [24][25][26], and combustion [27]. Large Eddy Simulation (LES) studies have primarily been concentrated with the SGEmac, Darmstadt, and TCC-III engine databases.…”

Generation of Turbulence in a RCEM towards Engine Relevant Conditions for Premixed Combustion Based on CFD and PIV Investigations

“…In the following, the performed measurements are presented and compared with the numerical predictions. While measurements have been conducted for three distinct pressure ratios (20,30,40), simulations considered only the pressure ratio of 20, due to computational time constraints. The focus of the simulation is to support the understanding of the flow field outside the optical accessible area as well as to provide estimates for the integral length scale as an input to the calculation of quantities relevant to the Borghi diagram.…”

“…Intake turbulence generally dissipates rapidly; delay between end of filling and start of rapid compression is on the order of seconds and therefore turbulent kinetic energy levels are almost completely dissipated when the rapid compression stroke is initiated as shown by Gerke et al [19]. Therefore, compared to optical engines, different intake port geometries or throttling devices cannot be applied to create different in-cylinder swirl ratios or turbulence levels [20].…”

Development of On-Board In-Cylinder Gas Flow Model for Heat Loss Estimation of Diesel Engines

“…RNG k- model [35], which is one of the RANS model and widely used in engine simulations, was employed. F. Perini et al [36] and P. C. Ma et al [37] guaranteed the accuracy of RANS model by comparing results of RANS model with results of PIV. The initial time step was set to 1 × 10 −5 s, and the maximum mesh number was 2,127,510 and the minimum one was 112,243.…”