Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lasers measure jet disintegration

19.04.2017

Planar laser induced fluorescence uncovers characteristics of fluid behavior important to jet propulsion and medicine

There are many processes, such as propulsion, in which fluid in a supercritical state, where the temperature and pressure put a substance beyond a distinguishable liquid or gas phase, is injected in an environment of supercritical thermodynamic conditions. Under these conditions, mixing and interaction dynamics do not behave as they would in their well-defined liquid or gas phases.


Shadowgraph images with PLIF density gradient maps of a subcritical injection into an environment of subcritical conditions compared with the two imaging results for injection with all conditions supercritical.

Credit: DeSouza and Segal

Rocket engines, gas turbines and diesel engines experience conditions in their combustion chamber that exceed the critical conditions of their fuel, and supercritical finely atomized sprays are used to coat tablets in the production of medicines. In both cases, understanding the precise dynamics of how the fluid breaks up and disperses can lead to fundamental improvements in the ways such systems are built.

The study of jet disintegration in particular focuses on fuel breakup and mixing within the combustion chamber of propulsion devices. A team of researchers at the University of Florida applied spectroscopic diagnostics techniques to learn more about the fundamentals of sub- and supercritical jet disintegration, and reports their new findings this week in the journal Physics of Fluids, by AIP Publishing.

"The Planar Laser Induced Fluorescence (PLIF) technique and the process of correcting for absorption effects is a tool that is unique to the Combustion and Propulsion Laboratory," said Shaun DeSouza, a researcher at the University of Florida and lead author of the publication. "This method provides quantitative data for comparison with the qualitative data produced by the shadowgraph technique." While imaging studies of jets have been performed by many different research institutions, there is limited quantitative density data reported in these studies.

To get that quantitative data, DeSouza and his collaborator ran 48 tests of jets injected from a single orifice into a chamber with one of a range of sub- to supercritical temperature and pressure combinations. They used a fluid called fluoroketone in these tests because of its low critical temperature and pressure, characteristics governing the supercritical behavior of interest, as well as its distinct spectral features well suited to PLIF detection.

The current study of single orifice jets injected into a chamber of sub- to supercritical temperatures and pressures was focused on the effect of the chamber-to-injectant density ratio on the jet disintegration with 48 tests run over an extensive density ratio range. For these tests, researchers used fluoroketone as the working fluid because it has a comparatively low critical temperature and pressure and a strong absorption in the near ultraviolet range making it a good choice for shadowgraph and PLIF visualization.

The results of the study demonstrated the accuracy of PLIF, imaging single planes of the flow field through the center of the jet, leading to noticeable differences in the measured spreading angle compared to shadowgraphy. Unlike shadowgraphy, which integratively images the entire jet, PLIF provides more detailed density information that illuminates features shadowgraphy can't detect.

Each imaging technique offers complementary advantages, with PLIF providing quantitative density results and shadowgraphy providing very detailed flow visualization. While the shadowgraph data agreed with previous visualization studies, the PLIF results that provided quantitative measurement of central jet plane density and density gradients offered new and differing results.

The results also revealed trends key to understanding and improving applications like jet propulsion, such as an increase in normalized drop diameter and a decrease in droplet population as chamber temperatures increased. According to the work, however, both droplet size and distribution were independent of chamber pressure.

"The next step for this line of research is to expand the thermodynamic conditions explored and to improve imaging hardware to gain a better understanding under a larger variety of conditions," said DeSouza.

###

The article, "Sub-and supercritical jet disintegration," is authored by Shaun DeSouza and Corin Segal. The article will appear in Physics of Fluids April 18, 2017 (DOI: 10.1063/1.4979486). After that date, it can be accessed at http://aip.scitation.org/doi/full/10.1063/1.4979486.

Media Contact

Julia Majors
media@aip.org
301-209-3090

 @jasonbardi

http://www.aip.org 

Julia Majors | EurekAlert!

More articles from Physics and Astronomy:

nachricht Tiny lasers from a gallery of whispers
20.09.2017 | American Institute of Physics

nachricht New quantum phenomena in graphene superlattices
19.09.2017 | Graphene Flagship

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

Im Focus: Silencing bacteria

HZI researchers pave the way for new agents that render hospital pathogens mute

Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Molecular Force Sensors

20.09.2017 | Life Sciences

Producing electricity during flight

20.09.2017 | Power and Electrical Engineering

Tiny lasers from a gallery of whispers

20.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>