Shock Waves Might Offer The Jolt Needed To Reach Mars
August 3, 2020 USC
Applying shockwaves can improve conditions for fluid mixing in supersonic combustion engines, paving the way for flights at speeds five times faster than the speed of sound.
Ivan Bermejo-Moreno likes his coffee with a touch of turbulence. But instead of mixing coffee and cream with a spoon, when it comes to hypersonic jet planes – planes that can fly five times faster than sound – he likes to mix oxygen from the air and jet fuel using something a bit stronger: shock waves.
Similar principles govern fluid mixing in aircraft engines, where oxygen from the air has to mix with fuel to help propel it at a certain speed. USC researchers in the USC Viterbi Department of Aerospace and Mechanical Engineering, including Xiangyu Gao, a USC Viterbi Ph.D. student who recently defended his dissertation, and his doctoral advisor, Assistant Professor Ivan Bermejo-Moreno, are studying how to achieve efficient mixing at high speeds. Better mixing allows supersonic combustion engines—in which airflow is greater than the speed of sound—to remain shorter in length while enabling vehicles to move hypersonically. One approach to achieve this is to use shock waves.
A shockwave is characterized by an abrupt change in pressure, temperature and density of a medium and moves faster than the local speed of sound. “Without applying a shock wave, mixing will occur, as in the example with coffee and cream, but it will take much longer,” Bermejo-Moreno said. “Shock waves amplify turbulence—similar to a spoon in the coffee example—and the more turbulence you have, the more rapidly mixing can occur.”
The researchers recently published a study in the Journal of Fluid Mechanics , which shares conditions in which such rapid mixing—which supports faster, more efficient vehicles—can occur. Once a shock wave—a sudden and strong disturbance in a medium—is produced, the speed of the fluid passing through it will be drastically reduced, also allowing more time for mixing. This puts the fuel and air in a better condition for combustion, and will increase the temperature, making it easier to auto-ignite, the researchers said.
In conditions where mixing can be handled efficiently enough to support hypersonic vehicles, there are numerous implications, including commercial applications for the exploration of space.
Said Bermejo-Moreno: “Imagine instead of a rocket you have something lighter and smaller that could take us all the way to Mars. The combination of scramjets and rotating detonation engines, both based on shock waves and turbulence, may one day do just that.”
The research team also includes Johan Larsson, associate professor of mechanical engineering at the University of Maryland. The researchers conducted this study performing massively parallel numerical simulations on the supercomputers at USC’s High Performance Computing Center and at Argonne National Laboratory.
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scource: https://scienceblog.com/517711/shock-waves-might-offer-the-jolt-needed-to-reach-mars/