Researchers are using liquid neutron radiography to better understand supersonic fluid flow behaviour.

The aerospace race is on once again for supersonic and even hypersonic air travel. Hypersonic aircraft would travel at  Mach 5 or above – about 4,000 miles per hour. However, liquid fuel combustion at those speeds and atmospheric conditions is not well understood.

Searching for solutions to better understand supersonic fluid flow behaviour, researchers from the University of Tennessee–Knoxville and the US Air Force are using neutron radiography at the Department of Energy’s (DOE’s) Oak Ridge National Laboratory (ORNL).

The team says a better understanding of spray dynamics will lead to improved fuel injector designs for the aeronautic and automotive industries, as well as other spray-related applications used in agriculture, pharmaceuticals and manufacturing.

1,000 metres per second

“In hypersonic systems, when you’re flying at, say, Mach 5, you’re basically flying like 1,000 metres per second, and the fuel has to be sprayed into a supersonic flow, which then has less than a millisecond to burn,” said UT Associate Professor Zhili Zhang. “So we need a nozzle efficient enough to do this; but, unfortunately, there’s no standard nozzle that exists.”

Using the IMAGING beamline CG-1D at ORNL’s High Flux Isotope Reactor, the researchers designed an experiment using different nozzle configurations to study the interior and exterior flow patterns before and just after the spray is dispersed into the combustion chamber.


Neutrons are ideal for this kind of research because they can see through almost any material in a non-destructive fashion and are sensitive to light elements such as hydrogen and various hydrocarbons used in jet fuel.

Neutron radiography allowed the team to look through the metal nozzles and observe the fluid densities and flow pattern behaviours to determine how liquid fuel might flow more effectively with improved designs.

“We’re interested in developing an instrument capability that will enable people to get data on those behaviours. From there we’ll be able to know things about atomisation and temperature and other effects that deal with combustion efficiency,” said UT graduate research assistant Cary Smith. “The more we can scientifically understand those things, the better we’ll be able to design efficient nozzles for better combustion.”

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