Russian developers from MAI have proposed an unusual method for atomizing fuel components in a liquid rocket engine: instead of a conventional circular jet cross-section, the authors suggest forming a complex profile that continuously rotates along the channel. This solution, according to the patent description, should enhance flow turbulence and improve the mixing of fuel components.
The design is based on an injector with a hollow tip and a sleeve. One component under pressure passes through the axial channel of the tip, the second — through the annular gap between the tip and the sleeve. At the outlet, a jet with a non-circular cross-section is formed, which gradually changes its orientation as the flow moves.
To form such a channel, it is proposed to use a Joachimsthal channel surface — a complex geometric surface known in mathematics and engineering design. In the considered invention, it is no longer used as an element of the shell structure, but to define the shape of the flow part of the injector. The cross-section of the jet can continuously rotate by a total angle from 30° to 540°.
For surfaces of the second and third types, the boundary of the cross-section is proposed to be described by a cosinusoidal law. The number of rays can be 3, 4, 5, or 6, and the ratio of the cosine amplitude to the base radius is set in the range of 0.4–1.3.
The patent claims a technical result — an increase in the turbulent kinetic energy of the jet by 1.5–2 times. In the calculated example provided by the authors, numerical modeling showed a 1.5-fold increase in the mass-averaged turbulent kinetic energy. It is assumed that this will improve component mixing and increase the completeness of their combustion.
However, this is a patent technical solution. The patent does not contain data on experimental verification of the injector on a working liquid rocket engine; the result presented was obtained by numerical modeling. Therefore, the 1.5–2 times indicator should be correctly cited as a claimed technical result, and not as a confirmed characteristic of a working engine.
For a liquid rocket engine, the quality of atomization is of fundamental importance: after exiting the injector, the liquid component must break into droplets and mix with the other component. The conditions of subsequent combustion and the efficiency of the chamber depend on the characteristics of this process.
What physics says: the very idea of enhancing turbulence by changing the channel geometry does not contradict basic hydrodynamics. However, additional turbulence does not come for free — the flow energy is taken from its total energy budget and is associated with pressure losses when passing through the injector. Therefore, the practical value of the proposed geometry is determined by whether it will be possible to obtain better atomization without excessive increase in hydraulic losses. This is a matter of calculation and experiment.
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