Blowing bubbles may be fun for kids, but for engineers, bubbles can disrupt fluid flow and damage metal.
Researchers from the Fuels, Engines and Emissions Research Center at the Department of Energy’s Oak Ridge National Laboratory and collaborators from ORNL’s High Flux Isotope Reactor – a DOE Office of Science User Facility – are using neutrons to study the formation of these damage-causing bubbles in fuel injectors.
Derek Splitter and Eric Nafziger from the Fuels, Engines and Emissions Research Center at Oak Ridge National Laboratory prepare their fuel injector test system for experiments at the High Flux Isotope Reactor. They used the neutron beam at HFIR to non-destructively study the internal structure of fuel injectors for gasoline vehicles so that the internal fluid flow could be modeled based on the imaged components. Image credit: Genevieve Martin/ORNL
This team is attempting to make the first-ever neutron images of cavitation, the physical event that leads to bubble/gas formation, inside the body of a gasoline fuel injector. In August, they conducted their research at HFIR’s CG-1D beam line, which is used for neutron radiography and computed tomography, to non-destructively study the internal structure of the fuel injector. With data in hand, they will be diving deep into the analysis of the images to identify both the location and the timing of the cavitation.
“We can measure the spray of a fuel injector using X-rays, but imaging the internal structure in operation is very challenging,” said Hassina Bilheux, HFIR instrument scientist for CG-1D.
The team, led by Eric Nafziger, Derek Splitter and Todd Toops from FEERC/ORNL under a Laboratory Directed Research and Development project, studied a spray-guided gasoline direct-injection (SGDI) unmodified 6-hole injector. SGDI systems are a relatively new technology that have been developed to more precisely control fuel delivery to each cylinder and allow reduced fuel consumption in gasoline engines.
“There's a lot that is not understood about these systems, and thus a lot to be learned,” Toops said. “Our work is focused on identifying the time and location of cavitation events – to study the injector with the ability to see cavitation in action.”
A cavitation event is when a gas bubble forms in the injectors, disrupting the spray pattern and ultimately deteriorating the injector material properties.
“Neutrons are ideally suited for this study due to their high sensitivity to hydrogen atoms in the fuel and low interactions with the metal part of the injector,” said Bilheux.
Other complementary research has been done with lasers, X-rays and even with fuel injectors made partially with acrylic to make them see-through. However, those experiments had temperature and pressure limitations. This neutron technique, explained Toops, is the first to have the potential to see what’s happening inside the injector at normal operating conditions.
In order to create an experiment that closely mimics natural conditions of an engine running, Nafziger, Splitter and Toops developed a closed loop fuel injection system designed to operate with commercial and prototype injectors and deliver fuel to the injectors at pressures up to 120 atmospheres.
With 48 hours of observations for a given operating condition, they compiled approximately 1 million injection events to capture a 7 millisecond composite injection sequence, with 1 millisecond before injection, 1 millisecond of injection, and 5 milliseconds after injection. This compilation was accomplished with a 0.02 millisecond time resolution.
“In the initial analysis of the composite neutron images, it is possible to see both internal injector motion and the spray exiting the nozzle,” said Nafziger. “Just inside the nozzle area, a marked difference in fluid density is also observed during the injection event, indicating vaporization of the fluid and possible cavitation.”
The team is working on more detailed analysis of the data, and will collaborate with the ORNL high performance computing team for fluid dynamics modeling as part of the second year of their project.
UT-Battelle manages ORNL for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of the time. For more information, please visit science.energy.gov.
Kathie Bethea | newswise
Silicon solar cell of ISFH yields 25% efficiency with passivating POLO contacts
08.12.2016 | Institut für Solarenergieforschung GmbH
Robot on demand: Mobile machining of aircraft components with high precision
06.12.2016 | Fraunhofer IFAM
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Life Sciences
08.12.2016 | Physics and Astronomy
08.12.2016 | Materials Sciences