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Internal combustion engine flows for motored operation
Application Challenge AC2-10 © copyright ERCOFTAC 2024
Abbreviations
ALE | Arbitrary Lagrangian-Eulerian |
aTDC | after top dead center |
bTDC | before top dead center |
BDC | bottom dead center |
CA | crank angle |
CAD | crank angle degreeCCD charge-coupled device |
CCV | cycle-to-cycle variation |
CDS | central differencing scheme |
CFD | computational fluid dynamics |
CFL | Courant-Friedrichs-Lewy |
ENO | Essentially Non-Oscillatory |
ERG | exhaust-gas-recirculation |
EVC | exhaust valve closing |
EVO | exhaust valve opening |
HS-PIV | high speed particle image velocimetry |
IC | internal combustion |
IVC | intake valve closing |
IVO | intake valve opening |
LES | large eddy simulation |
MRV | magnetic resonance velocimetry |
PIV | particle image velocimetry |
POV | field-of-view |
QSOU | quasi-second-order upwind |
QUICK | Quadratic Upwind Interpolation for Convective Kinematics |
RANS | Reynolds-averaged Navier-Stokes |
RMS | root mean square |
RPM | rounds per minute |
SAS | scale-adaptive simulation |
SRS | scale-resolving simulation |
SST | shear stress transport |
TDC | top dead center |
TUBF | Technische Universität Bergakademie Freiberg |
TUD | Technische Universität Darmstadt |
TVD | total variation diminishing |
UDE | Universität Duisburg-Essen |
URANS | unsteady Reynolds-averaged Navier-Stokes |
WG | wall-guided |
Description
Introduction
The TU Darmstadt engine is an optically accessible single cylinder spark-ignition direct injection engine. It is embedded in an especially designed test bench to provide well characterized boundary conditions and reproducible engine operation. A reproducible engine operation is needed to characterize the variety of in-cylinder processes and is a prerequisite for any comparison of experiments and simulations. The in-cylinder processes are characterized using advanced laser-diagnostics to provide measurements at high spatial and temporal resolutions. The aim of this effort is, to build up a comprehensive data set
- to give insights into the underlying physics for a better understanding of the relevant in-cylinder processes and
- for the validation of CFD simulations especially for large eddy simulations (LES).
The validation of CFD simulations for IC engines requires a variety of physical and chemical quantities and a comprehensive dataset consisting of systematic hierarchical sub-datasets. Such a validation sequence typically starts with the comparison of the non-reacting flow field and increases complexity stepwise by the addition of processes such as, combustion of perfect homogeneous air/fuel mixtures, in-cylinder mixture preparation using direct-injection and combustion of these mixtures. The presented test case is part of an ongoing effort at TU Darmstadt aiming for a detailed characterization of engine combustion addressing the non-reacting flow field \cite{Baum2014,Baum2013,Zentgraf2016}, combustion of homogenous air/fuel mixtures \cite{Peterson2015} and mixture preparation by direct injection \cite{Peterson2017}. The here presented test-case includes the sub-dataset on the non-reacting flow field (motored engine operation) providing a comprehensive data set on the first two statistical moments of flow velocities, spatial flow structures, and the dynamics of the turbulent in-cylinder flow field. The following sections summarize the work which has been presented within \cite{Baum2014}. Further details on the experimental setup and flow field data can be found in \cite{Baum2014,Baum2013,Zentgraf2016}. Additionally, simulation results obtained from three investigations using LES (Large Eddy Simulation) and hybrid URANS (unsteady Reynolds-averaged Navier-Stokes)/LES described in section \ref{sec:simulation} are presented and compared with experimental data, see section \ref{sec:evaluation}.
Relevance to industrial sector
Design or assessment parameters
Engine test bench
The engine test bench allows conditioning the intake air in terms of pressure, temperature and gas composition, port fuel injection of liquid and gaseous fuels, direct-injection, as well as reliable boundary condition control and measurement. Further, the intake and exhaust systems were designed to provide reproducible thermodynamic and flow boundary conditions and simplified meshing for three-dimensional engine flow simulations. Figure \ref{fig:testbench} shows a schematic of the engine test bench from the intake to the exhaust plenum. It shows the locations for which thermodynamic conditions (pressure and temperature) were measured during engine operation.
Figure 2: Engine test bench. |
Engine
The engine is an optically accessible single-cylinder direct injection spark ignition engine with a bore and stroke of 86\,mm. The engine features a twin-cam, overhead-valve pent-roof cylinder head, a 55\,mm height quartz-glass cylinder liner with 8\,mm window extension into the pent-roof, and a Bowditch piston arrangement with flat quartz-glass piston-crown window (75\,mm diameter). The intake manifold is designed to generate a tumble flow. The engine is operated with a geometric compression ratio of 8.5:1 and has a 499\,$\mathrm{cm^{3}}$ displacement volume. At top dead center (TDC), the clearance height is 2.6\,mm and a clearance volume of 66.61\,$\mathrm{cm^{3}}$ remaines. The piston ring top-land crevice contributes to the reported clearance volume. The piston ring pack is located 74\,mm from the piston top to prevent the piston rings from riding over the quartz-glass cylinder liner. The average spacing between the piston and cylinder-liner is 0.5\,mm. The top-land crevice volume contributes to the overall clearance volume and is included in the geometric compression ratio. For this test-case, a wall-guided (WG) cylinder-head was used equipped with a side-mounted fuel injector, a centrally located spark plug, and dual intake valves (33\,mm diameter) and exhaust valves (29\,mm diameter) located on opposite sides of the spark plug, see Figure \ref{fig:cylinderhead}.
Figure 3: Cross-section of the wall-guided cylinder head in the central tumble plane at z\,=\,0\,mm and a top view of the cylinder head. |
Flow physics and Fluid Dynamics Data
Contributed by: Carl Philip Ding,Rene Honza, Elias Baum, Andreas Dreizler — Fachgebiet Reaktive Strömungen und Messtechnik (RSM),Technische Universität Darmstadt, Germany
Contributed by: Brian Peterson — School of Engineering, University of Edinburgh, Scotland UK
Contributed by: Chao He , Wibke Leudesdorff, Guido Kuenne, Benjamin Böhm, Amsini Sadiki, Johannes Janicka — Fachgebiet Energie und Kraftwerkstechnik (EKT), Technische Universität Darmstadt, Germany
Contributed by: Peter Janas, Andreas Kempf — Institut für Verbrennung und Gasdynamik (IVG), Lehrstuhl für Fluiddynamik, Universität Duisburg-Essen, Germany
Contributed by: Stefan Buhl, Christian Hasse — Fachgebiet Simulation reaktiver Thermo-Fluid Systeme (STFS), Technische Universität Darmstadt, Germany; former: Professur Numerische Thermofluiddynamik (NTFD), Technische Universität Bergakademie Freiberg, Germany
© copyright ERCOFTAC 2018