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
Laser sensor LAH-G1 - optical distance sensors with measurement value display
15.08.2017 | WayCon Positionsmesstechnik GmbH
Engineers find better way to detect nanoparticles
14.08.2017 | Washington University in St. Louis
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences