Argonne National Laboratory represents the United States’ Department of Energy’s commitment to cooperative research and scientific discovery. Since its inception in 1946, Argonne has pioneered laboratory research and experimentation as the first national laboratory in the United States. While a significant amount of research in the decades following its founding centered around nuclear energy and applications, Argonne has transitioned from nuclear research to include additional energy sources and storage since the beginning of the 21st century. Now, Argonne constitutes a scientific community of leading researchers, with projects across a spectrum of computational, quantum, and interdisciplinary fields.
Among the contributors in this area are Dr. Joohan Kim and Dr. Riccardo Scarcelli. Their work on modeling spark discharge processes in spark-ignition (SI) engines was recently recognized by Argonne. Dr. Kim received a Postdoctoral Performance Award in the area of Engineering Research, along with ten other postdoctoral appointees whose contributions set a standard not only for the quality of their discoveries, but also for the ingenuity of their techniques and demonstrated leadership capabilities. According to Argonne, awardees’ works have upheld core values of scientific impact, integrity, respect, safety, and teamwork.
Within the highly competitive automotive industry, the need for innovation through design presents opportunities for new tools and technologies to be utilized. Regulations from governing entities seek to strike a balance between meeting climate goals through greater restrictions on CO2 emissions from automobiles, while relying on the transportation industry and automotives to fuel trade and commerce. With restrictions focused solely on reducing emissions, applications that meet these criteria without sacrificing capabilities stands out for both manufacturers and legislators alike.
Dr. Kim’s work highlights the need for predictive models which can optimize operational parameters for SI systems in order to maximize thermal efficiency gain and lower engine development costs. Creating these predictive models requires advanced simulation software capable of solving and coupling electromagnetic physics and fluid dynamics into a computational framework. When we asked about his use of simulations, Dr. Kim said, “high-fidelity simulations enable us to perform in-depth analysis of the spark-ignition process, including energy transfer, birth of flame kernel, and thermo-chemical properties; these would be difficult to obtain using experimental techniques only.” He went on to add that, “with a fundamental understanding of complex physics, we can develop predictive models that make simulation-based optimization robust and reliable.”
“VizSpark provided a fully-coupled framework between electromagnetic physics and fluid dynamics, and thereby we were able to diagnose the plasma properties occurring within tens of nanoseconds without many assumptions.”
Dr. Kim’s study utilized VizSpark simulations to accurately estimate electrical discharge shape, as well as temperature and pressure of plasma kernels, thus providing a set of robust initial and boundary conditions for studying flame kernel growth under engine-like conditions. He noted “VizSpark provided a fully-coupled framework between electromagnetic physics and fluid dynamics, and thereby we were able to diagnose the plasma properties occurring within tens of nanoseconds without many assumptions.”
VizSpark is a robust, industrial simulation tool for high-fidelity modeling of thermal (arc) plasmas. Additionally, VizSpark is fully parallelized and can be used to perform large, 3D simulations with complex geometries. Its comprehensive solvers and scalability make it ideal for solving real world engineering problems.
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Automobiles have significantly improved the lives of humans – nothing is too far these days with a car. In our vehicle, we set off to drive for work, make a short spree to the local grocery store, cruise on a long road trip, get our packages delivered, and what-have-you.
We almost never notice the complex mechanisms of a car that reliably get us from point to point (until it breaks down…). Every time we start our car to carry out our business on the road and until we turn it off, there are, on average, a few thousand explosions per minute inside the engines of our car that set us in motion. That is almost 20 times every second for each cylinder!
Hidden Consequences of the “Bang” Part of Combustion
Spark plug ignites fuel-air mixtures by inducing a dielectric breakdown in the spark gap. In order to initiate the breakdown, sufficient voltage difference across the electrodes is supplied until the breakdown happens. This phenomenon leads to formation of a spark – a form of plasma and is akin to formation of lightning, but on a much smaller scale.
At such intense continuous operating conditions, every stroke of the engine causes the electrodes on the spark plug to undergo various phenomena such as melting, vaporization, sputtering, and oxidation. These processes cause electrodes to erode which leads to degraded performance of the engine. More often than not, when you are trying to start the engine – and it fails or if your car is sluggish, it is likely due to eroded electrodes which are causing this nuisance. Electrode erosion affects formation of spark between the electrodes.
Spark plug erosion is a complex multi-physics transient phenomena which involves coupling of surface physics (electrode depletion), thermal plasma physics (spark formation), circuit dynamics (ignition coils), turbulent chemical interactions (combustion) and heat transfer.
The spark between the electrodes lasts only for a few milliseconds, depending on the ignition system. On the other hand, the erosion of the electrodes could take up to years. Modelling misfires and erosion are arduous as the model needs to accurately capture multi-physics phenomena that occur in completely different time scales.
This poses a problem: how do you simulate physics of spark plugs which occur at different time scales, with highest possible fidelity, simultaneously, within a matter of hours?
Here is where multiphysics capabilities of VizSpark opens new dimensions of understanding erosion – our thermal equilibrium plasma solver developed at Esgee Technologies, has been successfully used by major automotive companies to understand the spark formation and erosion behavior of the electrodes.
VizSpark provides multiphysics tools for mixing and matching electromagnetics, plasma, fluid dynamics, chemistry, circuit dynamics and many more, in a single easy-to-use framework.
For example, our CircuitLib module in VizSpark allows for flexibility in a variety of configurations which power the electrode. The circuit parameters are coupled with the fluid dynamics module. This means you could generate a spark in a realistic manner as it would happen in an engine.
The figure on the left, captures variations in the spark properties which are reflected in the results generated by the coupling of physics. Industrial researchers rely on the highly resolved current and voltage readings to understand the misfires that lead to erosion. Using VizSpark simulation, they have developed a predictive ability to design high-efficiency spark plugs by optimizing electrode geometry.
Next comes the massively scalable multi-processor, multi-node capability of VizSpark which is implemented at all stages of the simulation: mesh partitioning and simulation. The video on the right shows our high fidelity 3D representation of the geometry involved in this study. Here the top electrode is grounded, while the bottom electrode is connected to a current source to power the spark plug. Here, the geometry is an accurate representation of a J-type spark plug. Using partitioned mesh, Vizspark takes advantage of parallel processing and speeds up the simulation by many folds.
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Esgee Technologies gave a talk on “High-Fidelity Modeling of Spark Plug Ignition and Erosion” at the VERIFI workshop on Ignition for Internal Combustion Engines during July 27-28, at the Argonne National Lab in Chicago, Illinois. The talk focused on recent developments for modelling spark ignition kernels using a fully coupled plasma ignition model and a modelling approach for simulating lifetime erosion of spark plugs using an arc plasma model.
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