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.
Interested in learning more about plasma flow simulations? Click here to take a look at our previous article. Feel free to follow us on Twitter and LinkedIn for more related news, or reach out to us directly at info@esgeetech.com.
Esgee Technologies will be presenting at this year’s Society of Automotive Engineers (SAE) WCX World Congress Experience held in Detroit, Michigan from April 5th to 7th. Our paper, “Modeling of Switching Characteristics of Hydrogen-Nitrogen Filled DC Contactor Under External Magnetic Field,” was chosen from hundreds of submissions to be featured at the event.
WCX is among the top annual gatherings which provides an intersectional forum between automotive engineers, researchers, scientists, and technical innovators. This year’s topics include EV technology and electrical infrastructure, energy storage and battery disposition, as well as design and safety for automated vehicles.
We sat down with Dr. Rakesh Ranjan, who will be presenting on behalf of EsgeeTech this year, in order to learn more about the applications for this research and how they align with the conference’s goals:
What applications are there for EV relay arcs? And why choose SAE to discuss them?
SAE is the biggest confluence of engineers dedicated to enhancing our mobility in an environmentally friendly manner. If you are excited about the prospect of buying a cleaner vehicle which won’t contribute to environmental pollution, it’s likely that the EV technologies behind it started as concepts presented at an SAE conference. Technologies for the future of mobility have their beginnings right here at SAE conferences.
As for EV relays, it is a critical component for the safety of electric vehicles. With increasing power needs for electric vehicles, there comes an increase in things like battery size and voltage levels required to drive vehicles. An increase in voltage means that electric isolation of safety-critical components would be delayed due to prolonged arcing. So, how safe your vehicle is could ultimately depend on how quickly the arc channel inside the EV relay quenches.
Perhaps it may not be the first feature that consumers think of when it comes to vehicle safety, but for manufacturers and anyone involved in future maintenance on the vehicle, arc-resistant equipment is key to creating a safe environment. For the owner of an electric vehicle, arc-quenching is also a means of decreasing or completely removing the risk of damage from arc flash events. That, of course, is desirable because it means lowered maintenance costs and higher longevity for critical automotive components.
What is the quick takeaway from your talk?
A one-minute synopsis of my talk would be about the use of hydrogen-nitrogen mixtures for quenching of arcs. One typically associates hydrogen with flammability, but it also has fantastically high diffusive properties which could lead to quicker arc quenching. We report how hydrogen concentration leads to smaller arc lifetimes, which in turn improves a circuit’s interruption performance. We simulated contact separation in hydrogen-enriched and pure air environments using VizSpark™ which showed us that a strong external magnetic field can stretch the arc and reduce its extinction time.
You mention that you used VizSpark™ in your research. Why choose VizSpark™ specifically? What scenarios / applications is it useful for?
VizSpark™ is a multiphysics CFD solver which is capable of capturing the interaction between the plasma and flow with high fidelity. One thing which I really like about it is its robustness for a wide range of thermal plasma problems. You can throw in tough multiphysics problems: permanent magnets, high voltages and currents, supersonic flows, conjugate heat transfer. In terms of industrial applications, I could think of EV Relays, fuses, and high-voltage circuit breakers. It could also be used for safety assessment in high-voltage applications. For example, if there is local arcing inside a battery pack and you want to assess the root-cause through V-I traces, you could potentially do it in VizSpark™.
WCX ’22 Attendees can view Dr. Ranjan’s presentation in the “Electric Motor & Power Electronics” session from 10:00 AM to 10:30 AM CDT on Wednesday, April 6th.
Thanks for reading! If you’re still curious about the topics discussed in this article, check out the following journal papers (and ask us for a free copy!):
Ranjan, Rakesh, et al. Modelling of switching characteristics of hydrogen-nitrogen filled DC contactor under external magnetic field. No. 2022-01-0728. SAE Technical Paper, 2022.
Interested in learning more about plasma flow simulations? Click here to take a look at our previous article. Feel free to follow us on Twitter and LinkedIn for more related news, or reach out to us directly at info@esgeetech.com.
The future of transportation seems to be increasingly electric. In its latest report on electric vehicles (EV), the International Energy Agency (IEA) highlights a 40% increase in EV demand despite a 16% dip in the global car sales. Moving towards electrified vehicles has also pushed a shift in the vehicle design where the mechanical components are being replaced with electronic-based automotive components. Relays play a critical role in such electrified systems.
A relay is a switch that is operated electrically and is used to control a high power circuit with a low power signal circuit. The most common type of relay is an electromechanical relay that consists of terminals for the signal and the terminals where the supply and load are connected. Upon receiving a signal, an electromagnetically operated armature closes or opens the gap between the supply and the load terminals. Traditional electromechanical relays dominate the market, over solid state relays, because of their advantages in a wide operating range of voltages and currents and the low cost to manufacture due to the simplicity in design. However, the main problem that affects the lifetime of electromechanical relays is arcing.
The primary undesirable effect of arcing is sudden load surge in a circuit. This delays the signal to the primary circuit breaker to isolate the load device, which may fail due to overcurrent. Further, arcing leads to high surface temperature which can erode the terminals and contactors or even weld the contactors to the terminals. Both of these undesirable phenomena cause a great deal of reliability and safety issues. The strength and duration of the arc have a significant impact on the safety of electric vehicles as well as on relay contactor erosion, therefore the lifetime of the relay.
Therefore, it is crucial to study the formation of arcs within relays and explore designs that suppress the arc formation. At Esgee Tech, we delve further into how this disengagement happens and what could be done to improve it further. An insight into these phenomena could allow faster mitigation of arcs and thus quicker response times.
Arc – The Most Energetic Type of Plasma Discharge
A gaseous medium that experiences a sufficiently high electric field results in ionization of the medium which causes the medium to become conductive. We call this an electrical discharge. The characteristics of an electrical discharge depends on the voltage and current as shown in the figure on the left. Discharges carrying large currents, such as illustrated in this blog post, are classified as arcs. Arc is self-sustaining, i.e., it does not require an external ionization source to maintain discharge – the internal electron and gaseous processes maintain structure of the arc.
The physics of arcs is very complex. Ambient pressure, ambient temperature, geometry of the electrodes, gas composition, electromagnetic fields, external circuit parameters and surface properties all dynamically affect the formation and quenching of arcs. Industrial designs of relays need to account for all of these tightly coupled phenomena.
Our engineers at Esgee Tech have developed VizSpark™, a robust and accurate thermalized plasma simulator. VizSpark™ allows coupling of reactive plasma mechanics, fluid dynamics, transient electromagnetics, radiative mechanisms, surface erosion physics, circuit dynamics and continuously morphing boundaries. VizSpark™ also supports complex 3D industrial geometries.
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Using VizSpark™ the industrial problem of understanding arcs and optimizing design and safety of EV relays can be effectively addressed at high fidelity.
EV Relay Computational Model and Results:
The electric vehicle relay geometry described in this blog comprises a stationary anode (left terminal), a stationary ground (right terminal) and a movable contactor that disengages to break the circuit. The circuit coupled with this domain is a 220 V DC supply via a load resistor as shown in the figure below. The gas composition in the relay is hydrogen which is kept at a pressure of 1 bar and 300 K. An external magnetic field of 1T is imposed in the z-direction (into the screen).
VizSpark™ captures breakdown of arc between the electrodes accurately as shown in the illustration below. Initially, about 35A flows through the arc, upon ignition. The Arc stretches outwards due to Lorentz force generated by the interaction of the arc with the external magnetic field. The total resistance of the arc increases as it stretches. This decreases the current and cools down the arc as temperature decreases due to reduction in joule heating. The partially extinguished arc reignites several times, around 400 µs, before finally extinguishing, in a phenomenon called restrike. VizSpark™ accurately simulates the stretching of the arc and formation of a new filament during restrikes. This is seen as a “saw-tooth” waveform in both transient voltage and current graphs.
As the gap between the contactor and terminals increases, the conditions are unfavorable for restrikes and fewer restrikes are seen in the later stages of the simulation. The potential across the gap increases to 220V and the current drops to 0A which marks a completely extinguished arc and the relay circuit is open.
Trade Studies with VizSpark™
A variety of methods can be applied to ensure faster quenching of the arc, which reduces the electrical cutoff time. A few techniques to extinguish the arc quickly are: stretching the arc through external magnetic fields, increasing the speed of the moving contactor, using gas mixtures that absorb electrons such as SF6, using gas mixtures with high thermal conductivities such as hydrogen, and using an arc chute/splitter plates to divide the main arc into smaller faster dissipating arcs. Further, use of external circuits such as snubber circuits which consist of a series configuration capacitor and resistor connected in parallel across the relay suppresses the spike in current as the voltage starts to fluctuate during arc quenching. All of these configurations can be simulated at fidelity using VizSpark™.
The computational model shown here is capable of incorporating comprehensive arc physics necessary to study quenching behavior in high-voltage EV relays. The model can be used to perform design/parametric studies on EV relays in reasonable computational time. Future work should involve detailed validation of the model with existing experimental data. Other avenues of research include incorporating eroded metal vapor, the inclusion of arc chute or splitter plates, and electrode deformation due to erosion.
We hope you are someone who is as fascinated about plasma flow simulations as we are, feel free to follow us at LinkedIn or reach out to us at info@esgeetech.com.
In the meantime, explore the following journal articles (do ask us for a free copy!):
Karpatne, A., Breden, D., and Raja, L., “Simulation of Arc Quenching in Hermetically Sealed Electric Vehicle Relays,” SAE Int. J. Passeng. Cars – Electron. Electr. Syst. 11(3):149-157, 2018, https://doi.org/10.4271/2018-01-0765.
N. Ben Jemaa, L. Doublet, L. Morin and D. Jeannot, “Break arc study for the new electrical level of 42 V in automotive applications,” Proceedings of the Forth-Seventh IEEE Holm Conference on Electrical Contacts (IEEE Cat. No.01CH37192), 2001, pp. 50-55, https://www.doi.org/10.1109/HOLM.2001.953189
R. Ma et al., “Investigation on Arc Behavior During Arc Motion in Air DC Circuit Breaker,” in IEEE Transactions on Plasma Science, vol. 41, no. 9, pp. 2551-2560, Sept. 2013, https://www.doi.org/10.1109/TPS.2013.2273832
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.
The Issue…
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?
The Solution…
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.
Here’s How…
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.
Stay Tuned for More Details
In the meantime, feel free to check out the whitepaper and other ground breaking simulations. Follow us on LinkedIn!
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.
Ignition kernel in cross-flow with arc channel and iso-octane fuel-air mass fraction. The arc physics and combustion ignition kinetics are solved simultaneously in a fully coupled manner.
