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. 2021 Sep 2;14(17):5015.
doi: 10.3390/ma14175015.

A Short Note about the Impact Action of a Water Jet Stabilized by a Coaxial Air Stream in the Air and Underwater

Josef Poláček  1 , Irena Marie Hlaváčová  1 , Martin Tyč  1
Affiliations

A Short Note about the Impact Action of a Water Jet Stabilized by a Coaxial Air Stream in the Air and Underwater

Josef Poláček et al. Materials (Basel). .

Abstract

A new original method, applying a coaxial protective airflow, was tested aiming to improve the pure water jet efficiency in surface layer removal or medium hard materials cutting or blasting. The dual action of the air flow is expected: the air co-flowing the water jet with approximately the same velocity should prevent the central jet from breaking up into tiny droplets in the near field, and simultaneously, it should support jet decomposition into big parts with enough destructive potential in the far-field. A brief survey of the relevant literature dealing with the water jet instability is presented, introducing four recognized breakup regimes. An original cutting head designed to generate a waterjet surrounded by protective coaxial air flow is introduced. The submitted device is supposed to operate within the first wind-induced regime. Two types of experiments, consisting of blasting limestone bricks placed either in the air or underwater, were realized. The depths of kerfs produced with different water pressures and air overpressures were evaluated. While no substantial positive effect was recognized in the air performance, the submerged blasting of the same material under similar conditions appeared to be promising.

Keywords: blasting; coaxial air flow; jet stabilization; pure water jet; submerged jet operation.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) an example of cutting in the air; (b) an example of submerged cutting.
Figure 2
Figure 2
The bottom part of the combined air/water cutting head: (a) overall view; (b) vertical cut; (c) inside view.
Figure 3
Figure 3
Scheme of the cutting head equipped with an air supply: (a) vertical cut through the bottom part; (b) overall cut along the whole cutting head, one of the air feeding pipes can be seen below.
Figure 4
Figure 4
Influence of coaxial air flow on average kerf depths for water pressure 10–20 MPa.
Figure 5
Figure 5
The average kerf depths after blasting with and without protective coaxial air flow with water pressures 10, 15, 20 MPa; the first column on the left represents blasting without air flow.
Figure 6
Figure 6
Influence of coaxial air flow on average kerf depths for submerged blasting with water pressure 20 MPa and two different stand-off distances.
See this image and copyright information in PMC

References

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