For the first time, scientists from Skoltech theoretically predicted the effect of synchronization, a kind of self-ordering, in detonation waves. Gorenje's discovery could help curb the inherently chaotic process in a way that stabilizes combustion in a rotating detonation engine, an experimental device that could save significant amounts of fuel compared to traditional rocket and ship engines. The study was published in the prestigious journal of Fluid Mechanics and was recognized as the best theoretical work of the year at a conference at the Institute of Chemical Physics of the Russian Academy of Sciences.

Detonation engine

Detonation engines are being developed in order to achieve fuel savings due to a more efficient combustion mode. Gorenje During detonation, gorenje products propagate at supersonic speed, which theoretically increases efficiency by 25%.

"In an engine with rotating detonation, a smaller cylinder is located inside a larger cylinder, a combustible mixture is periodically injected into the cavity between them, and its combustion occurs in a continuous detonation mode: a wave circles around a small cylinder. Gorenje However, due to the chaotic nature of the process, the detonation wave in general will not behave so predictably and regularly cycle after cycle. In particular, the speed of wave propagation can fluctuate quite strongly and unpredictably over time, making the engine unstable," explains the head of the study, associate professor at Skoltech Aslan Kasimov.

Skoltech has found a way to curb the detonation wave by regulating its fluctuations. To do this, scientists have theoretically demonstrated the effect of synchronization in the field of detonation for the first time.

What is synchronization?

For the first time, synchronization was discovered by Huygens in the XVII century. He observed a pair of pendulum clocks that hang on one beam and, as it turned out, because of this subtle connection with time, they synchronize the oscillations of the pendulums - they begin to move either in phase or in antiphase. Since then, synchronization has been discovered not only in mechanics, but also in various fields of chemistry, medicine, biology and even sociology.

"For example, some fireflies blink at a certain frequency. When a lot of such fireflies gather in one place, they begin to blink synchronously due to a very weak connection with each other: each beetle can only see its nearest neighbors," says the first author of the work, Andrei Goldin, a graduate student at Skoltech, and gives a number of other examples from different fields.

Thus, it has been experimentally shown that the natural biorhythm of each person can have a periodicity other than 24 hours — this can be seen if the subject is placed in an artificial environment without day or night. The fact that under the influence of periodic external influences (sunrise, noon, sunset), the internal rhythms of humans and animals adjust to a 24-hour cycle is also synchronization.

A pacemaker is also a similar periodic external influence that regulates the internal vibrations of the heart — neutralizes arrhythmia.

From the point of view of synchronization, it is possible to consider the rotation of the Moon to the Earth always with one side, and even the dependence of the number of victims of serial killers on the date.

In their new work, scientists from Skoltech for the first time demonstrated the phenomenon of synchronization for a detonation wave.

How is synchronization in detonation?

The nature of detonation is such that the detonation wave propagates "jerkily", that is, with variable velocity, even in a perfectly homogeneous medium. This means that the wave itself is an oscillator, like a heart with an arrhythmia in the example with a pacemaker. Moreover, it is with arrhythmia, because the fluctuations of this wave are quite unpredictable — recall, this is what interferes with the operation of the detonation engine.

"It turns out that fluctuations in the velocity of the detonation wave can be ordered by an external periodic effect, only this is not an effect in the usual sense, but natural inhomogeneities of the medium. The wave propagates in a combustible mixture, which, in the case of an engine, is injected by jets into the annular cavity between the two cylinders. In this case, the heterogeneity of the environment can be imagined as a series of areas more or less saturated with fuel (a strip of air, a strip of fuel, etc.), explains Kasimov. "So, by changing the design of the engine, for example, the distance between adjacent injectors, you can change the characteristic scale of the inhomogeneities of the medium that the detonation wave encounters."

As the researchers found out, the complex internal vibrations of the detonation wave are able to be ordered due to synchronization with the "vibrations" (periodic heterogeneity) of the medium. If we consider the set of characteristic scales of heterogeneity of the medium, it turns out that there are entire continuous ranges of these scales in which the oscillations of a known detonation wave are regularized, that is, it continues to propagate in "jerks", but these jerks become very predictable.

Due to the special shape of the graph, the totality of such ranges is called Arnold languages - they are described for the first time in the field of detonation.

Will Arnold's tongues start the detonation engine?

The discovery of synchronization and Arnold languages in detonation waves lays the foundation for further research, which in the future should answer the question of which engine design will curb the detonation wave by controlling its speed. So far, scientists have performed calculations in one dimension; in the engine, the process occurs in three at once.

The material is published on the popular science portal Naked Science.