Rotating Detonation Engine to make rockets fuel-efficient, lightweight

A new type of engine -- called a rotating detonation engine -- promises to make rockets not only more fuel-efficient but also more lightweight and less complicated to construct, say researchers. For the findings, published in the journal Physical Review E, researchers at the University of Washington have developed a mathematical model that describes how these engines work.

According to a March 2023 study, the research adopted air and gas mixtures with the same main composition as kerosene as the reactants. The study also designed the isolator, injector, and annular combustor, and performed an experimental study under the condition of high enthalpy airflow.

With this information, engineers can, for the first time, develop tests to improve these engines and make them more stable, they said.

"The rotating detonation engine field is still in its infancy. We have tons of data about these engines, but we don't understand what is going on, I tried to recast our results by looking at pattern formations instead of asking an engineering question -- such as how to get the highest performing engine -- and then boom, it turned out that it works," said study lead author James Koch from University of Washington in the US.

"This combustion process is literally a detonation -- an explosion -- but behind this initial start-up phase, we see a number of stable combustion pulses form that continues to consume available propellant," Koch added.

According to the researchers, this produces high pressure and temperature that drives exhaust out the back of the engine at high speeds, which can generate thrust.

To try to be able to describe how these engines work, the researchers first developed an experimental rotating detonation engine where they could control different parameters, such as the size of the gap between the cylinders.

Then they recorded the combustion processes with a high-speed camera.

Each experiment took only 0.5 seconds to complete, but the researchers recorded these experiments at 240,000 frames per second so they could see what was happening in slow motion.

From there, the researchers developed a mathematical model to mimic what they saw in the videos.

"This is the only model in the literature currently capable of describing the diverse and complex dynamics of these rotating detonation engines that we observe in experiments," said study co-author J Nathan Kutz.

The model allowed the researchers to determine for the first time whether an engine of this type would be stable or unstable. It also allowed them to assess how well a specific engine was performing.

"This new approach is different from conventional wisdom in the field, and its broad applications and new insights were a complete surprise to me," said co-author Carl Knowlen, a UW research associate professor in aeronautics and astronautics.

According to the researchers, right now the model is not quite ready for engineers to use.