Pneumoacoustic bar atomizer

Abstract

A mechanical device used to atomize liquids. The device eliminates circular instability at elevated generation frequencies, producing drops of 30-40μ. This is achieved when the central bar has been made with the diameter equal to the diameter of the nozzle. The longitudinal grooves in the central bar are located at the distance which does not exceed the quarter of the wave length of the nozzle working frequency. The depth of grooves at the central bar 8, their width t, number n, the generation frequency f, the width of the resonance groove of the pneumoacoustic bar nozzle a and the distance between the circular gas nozzle H and the bottom of the ring-like resonator were selected based on the ratio:
S=n.Math.8.Math.t,
where S is the aggregate cross section of grooves upon the preset gas efficiency;
12.5˜f.Math.8˜15;
1.8˜a/8˜2.1;
7˜H/8˜8.

Claims

1. A pneumoacoustic nozzle comprising: a cylindrical body having a central cylindrical hole and an inlet gas channel extending therethrough; a central bar inserted into the central cylindrical hole and having a part projecting from the cylindrical body, and having an inlet channel for liquids; a liquid circular chamber in fluid communication with the inlet channel for liquids; a nozzle for liquids in fluid communication with the liquid circular chamber and embracing the central bar; a ring-like resonator mounted on the projecting part of the central bar, which working part faces the cylindrical body, the working part having an annular resonance groove formed therein wherein the gas nozzle and the nozzle for liquids are coaxially installed, the nozzle for liquids being located further on along a radius as measured from a central axis line of the cylindrical body; a feedwell having an internal surface, the feedwell embracing the cylindrical body, forming a circular chamber and nozzle for liquids are made by longitudinal grooves in the cylindrical body, the grooves being limited by the internal surface of the feedwell, wherein the central bar has a diameter equal to the diameter of the gas nozzle and the longitudinal grooves are separated from each other by a distance that does not exceed a quarter length of a working frequency of the gas nozzle.

2. The pneumoacoustic nozzle according to claim 1, wherein a depth of each groove at the central bar is δ, the width of each groove is t, a number of the grooves is n, a generation frequency is f, the resonance groove having a width σ, and a distance H between the circular gas nozzle and a bottom of the resonance groove were selected based on the ratio:
S=n.Math.δ.Math.t, Where S is an aggregate cross section area of the grooves;
12.5≦f.Math.δ≦15
1.8≦σ/δ≦2.1;
7≦H/δ≦8.

3. The pneumoacoustic nozzle according to claim 2, wherein the nozzle generates drops having a size between about 30 microns and about 40 microns.

Description

(1) The main idea of the invention has been explained on FIG. 1 and FIG. 2.

(2) FIG. 1 shows the longitudinal cross section of the proposed device, where 1 is the cylindrical body, 2—the central body, 3—the cylindrical gas nozzle, 4—the central bar, 5—the inlet channel, 6—end-to-end gas channels, 7—the ring-like resonator in the shape of a disc with cylindrical bore protruding behind the cylindrical gas nozzle 3, 8—feedwell, embracing the body 1; 9 is the inlet nipple, supplying liquids, which is mounted on the feedwell 8; 10 is the distribution ring-like chamber; 11—the circular liquid channel; 12—circular nozzle for liquids; H—the distance between the circular gas nozzle and the bottom of the ring-like resonator 7; σ is the width of the resonant groove of the nozzle.

(3) FIG. 2 shows the cross section of the nozzle before the gas\liquid outlet from the gas\liquid nozzles, where 3 is the cylindrical gas nozzle; 7—ring-like resonator shaped as the disc; 11—circular liquid channel; 13—longitudinal grooves of the depth δ and width t.

(4) The pneumoacoustic bar nozzle operates according to the following mode:

(5) Gas enters through the gas channel 5 and the feed through gas channels 6 (under the over critical pressure) to the nozzle, created in the bar 4 by the system of longitudinal grooves 13. At the nozzle edge 3, the flat isolated jets have the Mach number equal to one. Drum-like structure, emerging inside each of the flat isolated jets, is slowed down by the ring-like resonator 7. The compression wave appears before the ring-like resonator while after it there is the subsonic flow zone. The area between the flat wave and the resonator bottom 7 makes up the quarter-wave “virtual” resonator which determines the nozzle generation frequency.

(6) The reinforcement of vibrations in this zone results in emergence of blast waves on the surface of jets and these waves are emitted in the surrounding space and, in particular, creating capillary waves on the top surface of the liquid film flowing out of the nozzle for liquids 12, separating the liquid drops and making the fog in the treated room.

(7) The frequency of acoustic vibrations' generation f is determined by the thickness of a jet at the nozzle edge 3. Selecting the depth of the longitudinal grooves 13 it is possible to determine the dispersity of the produced drops. The average size of the produced drops is equal to 0.3λ.sub.K, where the length of the capillary wave is λ.sub.K≅f.sup.−2/3.
The depth δ of the longitudinal grooves 13 on the central bar 4 and the acoustic vibrations' frequency f are bound by the ratio δ=γ/f, where δ is measured in mm, f—in kHz, and the coefficient γ for the ultrasonic range of frequencies often equal to 13.8±1.1 and it depends on the pressure of the atomizing gas P.sub.0, while the width of grooves t and their number n is determined by the aggregate cross section of grooves S=n.Math.δ.Math.t upon the preset efficiency of the nozzle using gas Q.sub.g(kg/s): Q.sub.g=0.4 P.sub.a.Math.S.Math.T.sup.1/2, where P.sub.a is the absolute gas pressure (kg/cm.sup.2), T—absolute gas temperature (K), S (cm.sup.2). The generation frequency of acoustic vibrations f actuated in the pneumoacoustic bar nozzle depends also on the geometric parameters of the resonator.

(8) For efficient work of the pneumoacoustic generator, embedding the gas nozzle and the resonator, the width of the resonance groove σ (FIG. 1) was selected within the range (1.8-2.1) δ, and the distance between the circular gas nozzle and the resonator H was selected in the range (7-8) δ.