With the latest release of Simcenter STAR-CCM+ 2019.3, the In-Cylinder Solution now offers IC engine combustion capabilities.
Simcenter STAR-CCM+ In-Cylinder Solution
While we all continuously hear about the electrification of automotive powertrains, the reality is that the internal combustion engine will not disappear anytime soon and will be a staple of powertrains for decades to come. The push to downsize the internal combustion engine and the integration into hybrid powertrain platforms present many new challenges for engine development which can only be overcome using extensive CFD simulation.
The In-Cylinder Solution add-on to Simcenter STAR-CCM+ allows you to perform accurate in-cylinder CFD simulations of engines easily. Default settings and automatically-created post-processing output are aimed at giving the engineer a “running start” and mean that you don’t need to be a CFD expert to set up and run one of the most challenging CFD simulations around!
Simcenter STAR-CCM+ In-Cylinder Solution benefits and features at a glance:
- problem set up: setup an engine simulation in minutes
- automatic meshing: morph and map takes care of moving component
- cold flow: maximize trapped air mass
- charge motion: improve mixing of inducted air and injected fuel
- combustion: maximize combustion efficiency
- design exploration: automatically optimize engine performance
- validation: excellent correlation with experimental data
Simple Problem Set Up
The In-Cylinder add-on opens up a minimal interface which shows only those inputs required for setting up an in-cylinder simulation, presenting a “top-down” workflow (you start at the top and work your way down through various levels). Most menus are one or two levels deep.
You do not have to be an expert Simcenter STAR-CCM+ user to set up and run in-cylinder simulations using the add-on as it uses an application-specific workflow and simplified interface. However, expert users can use those In-Cylinder simulations as the starting point for performing more complicated multiphysics engine simulations that exploit the full range of Simcenter STAR-CCM+ simulation capabilities.
The Simcenter STAR-CCM+ In-Cylinder Solution has been specifically developed to make setup quick and easy and leave time for the analyst to spend on “engineering” the solution rather than setting up the problem with lots of mouse miles and button clicks. From fast setup of typical multi-hole injectors which can easily be customized for spray targeting, to quick selection of fuels, to automatic setup of common post-processing outputs like liquid and vapour penetration plots and fuel mass tracking, the add-on has been designed to make the simulation setup easy and allow engineers to derive the most value of out the simulation process.
The In-Cylinder solution employs a simulation driver to run a transient mesh motion process. You only need to create a single initial mesh (comprising of trimmed cells and prism layers to capture boundary layer flow features). All of the mesh movement is automatically taken care of by the add-on, which automatically morphs and maps the mesh to account for the movement of the piston and valves. The tool performs quality checks on the mesh as it morphs, automatically creating a new undistorted mesh when necessary and mapping the simulation results to it.
The mesh is automatically refined in critical areas in line with best-practice: around the valve, the valve seat, the valve throat, up into the ports and around the gasket gap. This is done automatically for every simulation and does not require manual intervention by the user. The user has complete control over the mesh setup and can add additional regions of refinement (such as around a spark plug) as required.
This morph-map approach has been extensively tested and is highly conservative of mass for all practical applications.
Any in-cylinder simulation is among the most complex CFD simulations you can perform. The combination of high-speed flows, mesh motion requiring an EXTREMELY high level of mass conservation, and very small time scales (fractions of a crank-angle degree typically need time steps on the order of 1e-006 [s]) means a lot of work goes into the setup, and the numerics must be carefully selected to accomplish stable runs with reasonable turn-around times. This is even before we start layering on complex physics models when we include fuel injection (Lagrangian spray, droplet-wall interactions, wall films) and combustion (ignition, flame propagation, emissions formation, knock).
For this reason, a lot of simulation performed early in the development process is concentrated on so-called “cold-flow”. This involves modeling the transient process of the airflow in the cylinder, typically with the objective of maximizing the trapped air mass and examining the bulk motion (swirl and tumble) that this flow induces. Often we also look at the evolution of turbulence to better understand the potential for fuel and air mixing and, specifically in spark-ignited engines, what the turbulence levels around the spark plug are at the intended time of ignition (start of combustion).
Simcenter STAR-CCM+’s In-Cylinder solution allows you to set up cold flow simulations for multi-valve engines with the automated setup of mesh motion, letting you go from raw CAD geometry to running simulation in just minutes.
With the Simcenter STAR-CCM+ 13.04, we took a big step forward with the capability to set up and run “charge motion” simulations. This builds upon our previous “cold flow” capability by including the setup of liquid fuel injection and modeling the ensuing mixing process. Charge motion simulations allow engine manufacturers to improve combustion quality, by controlling the mixing of inducted air with injected fuel by identifying and rectifying rich or lean mixture regions, especially in critical parts of the cycle, such as when the piston approaches TDC and during spark ignition. This is especially important in today’s direct injection designs, where the injection of fuel directly into the cylinder greatly impacts the bulk flow and turbulence level – the insight provided by simulation is more important than ever.
Another critical role which charge motion simulation plays is the assessment for potential formation of harmful emissions. Again, ideally, we want to achieve high-quality mixing of fuel and air, which is especially challenging in direct injection systems where, at high load operating points, there is fuel injection during large portions of the engine cycle. Simulation tells us not only where we have lean and rich pockets of charge, but how fast the liquid fuel is evaporating, how much is impacting on surfaces in the cylinder, and if it’s forming films or pools on those surfaces. All of these give indications of the magnitude of harmful emissions formation which, if not mitigated, will need to be “cleaned up” downstream of the engine using expensive aftertreatment devices in the exhaust line.
Over the years OEMs have developed large databases for design guidelines based purely upon charge motion, using just the bulk motion inside the cylinder, metrics of fuel and air mixing quality, and levels of turbulence around the spark plug which tell them whether combustion is going to be good or not, saving them valuable engineering time, especially in the early design stages of a combustion system.
With the latest release of Simcenter STAR-CCM+ 2019.3 the In-Cylinder Solution now offers the first IC engine combustion capabilities. Yet, the ECFM-3Z combustion model is just the beginning. With three releases per year we are continuously increasing the breadth of capabilities with further high class combustion model options and submodels to capture knock and emissions.
Automated Design Exploration
With the power of the Simcenter STAR-CCM+ platform and the recently-released Design Manager, users can leverage the automation capabilities, scalability, and flexibility of the platform to easily and quickly execute design studies to optimize their engines for the next generation.
Additionally, since the In-Cylinder add-on automatically creates a parametric model, you’re only a few mouse clicks away from easily sweeping multiple operating conditions to understand the bulk motion and turbulence at different speeds/loads.
With Simcenter STAR-CCM+ 13.06 a swapping of geometries has been introduced allowing for easy setup of geometric design variation studies and the re-use of existing simulation setup on another geometry.
Both the In-cylinder Solution and Simcenter STAR-CCM+ have been extensively validated for engine simulations, using both proprietary and public domain engine designs.One example is our validation of the University of Michigan Transparent Combustion Chamber-III (TCC-III) Optical Internal Combustion Engine, which is a 2-valve head, 4-stroke, spark-ignition engine with a pancake-shape combustion chamber.
The results demonstrate excellent correlation with global thermodynamics variables (including cylinder trapped mass, pressure, and temperature) and, compared with visualization from the experimental rig, the major features of the flow field are also well captured.
For more details our most recent combustion validation watch our On-Demand Webinar on CFD simulation of in-cylinder combustion
Committed to the IC Engine Market
Siemens Digital Industries Software is completely dedicated to the Engine Simulation market, recognizing that internal combustion engines are here to stay and that only advanced simulation can deliver the cleaner more efficient engines that society deserves.
As part of Simcenter STAR-CCM+, the In-Cylinder solution will receive updates three times per year and will continue to add features that address these simulations.
At any time, a dedicated team of outstanding engine CFD experts will be there to support you, solving even the toughest problems in in-cylinder CFD.
On the Road
We’re on the road with our In-Cylinder solution: Take the occasion and learn more about the Simcenter STAR-CCM+ In-Cylinder Solution by joining our presentations and talking to us at one of the upcoming events:
2019 Simcenter Conference, December 2-4, Amsterdam, NL
19th Stuttgart International Symposium, March 19 -20 2019, Stuttgart, GER International Multidimensional Engine Modeling Meeting IMEM, April 8, 2019, Detroit, MI, USA
20th Annual ICE Workshop for In-Cylinder CFD Simulation (Americas), April 12, 2019, Livonia, MI, USA
Annual ICE Workshop for In-Cylinder CFD Simulation (Europe) de / en, May 21, 2019, Stuttgart, GER
Seventeenth International Conference on Numerical Combustion, May 6-8, 2019, Aachen, GER
Realize Live, June 10-13, 2019, Detroit, MI, USA
NAFEMS World Congress 2019, June 17-20,2019, Quebec City, CAN
For information on or to download Simcenter STAR-CCM+, please visit the Steve Portal.