RU2344001C2 - Alarm for oncoming resonant waves - Google Patents

Abstract

FIELD: physics; acoustics.

SUBSTANCE: present invention pertains to acoustics, particularly to devices for generating resonant acoustic oscillations in flowing liquid or gas medium, and can be used for making all types of high quality dispersion systems. The device comprises coaxially fitted cylindrical stator in form of a concentric acoustic resonator or hollow rotor, in the adjacent surfaces of which there are through openings, uniformly distributed around, an actuator for uniform rotation of the rotor, apparatus letting liquid or gas mixture into the rotor and product outlets. The hollow rotor of the alarm consists of a series of longitudinal sections with number of openings different by one from the number of openings of the stator for generation of progressive rotating resonant wave of oscillations in the resonator - straight, in the direction of rotation of the rotor, - if more by one and inversely, in the opposite direction of rotation of the rotor, - if less by one. The number of such sections of the rotor is arbitrary, and they alternate so as to provide for counter rotation of resonant propagating waves on adjacent borders of sections. All outlets are at a tangent to the outer surface of the stator in the direction corresponding to the rotary waves and are directed in the same transverse direction. That way, the alarm generates opposite resonant rotary waves, obtained from a single rotor.

EFFECT: increased output of the propellant with simultaneous increase of its efficiency, as well as simplification and reliability of the device.

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Description

The invention relates to acoustics, and in particular to devices for creating powerful resonant acoustic vibrations in a flowing liquid or gaseous medium, and can be used in oil and gas, medical, chemical, pharmaceutical, perfumery, cosmetic, food, energy, metallurgical, engineering and other industries for the production of all kinds of high-quality dispersed systems.

Sirens are practically the only powerful sources of acoustic vibrations for liquid and gaseous media, containing a hollow stator and a rotor with a series of equally spaced identical holes on adjacent surfaces / Bergman L. Ultrasound and its use in science and technology. M .: Publishing house of foreign countries. L-ry, 1957. 726 p. /.

The idea of combining a siren as the most powerful source of acoustic vibrations and the phenomenon of resonance as a method of accumulating vibrational energy is implemented in a dispersant, a device for the production of high-quality dispersed systems, on rotating resonant acoustic waves / Sviyazheninov E.D. Hydroacoustic siren. Patent for invention No. 2284229. Priority 04/28/04 /.

In this device, adopted as a prototype, to coordinate the disturbance frequencies and the natural frequencies of the oscillations of the resonator, it is not a standing wave but a traveling wave that is excited by a rotating wave, which is achieved by modifying the perforation of the siren rotor. The resonant mode of operation provides optimal conditions for pumping mechanical energy into the oscillatory system to perform work, such as grinding and mixing media. This is most relevant for liquid and gaseous media that are not “afraid” of increased vibrations, pressures and fatigue damage. A rotating resonant wave fits perfectly into the technical purpose of the device - mixing and grinding of dispersed media, because stagnant areas are eliminated and product flowing through. The prototype introduced a siren with a new type of perforation, which allows you to create a rotating acoustic wave that is both coincident and opposite to the direction of rotation of the rotor, capable of exciting low-frequency two-node (along the circumferential coordinate) forms of natural vibrations in a circular region. The resonant siren is surrounded by a concentric resonant sounding chamber tuned to the fundamental frequency of just such natural forms of acoustic vibrations.

The objective of the present invention is to increase the performance of the dispersant while increasing its effectiveness.

The problem is solved by introducing an elongated shaft of the siren rotor, consisting of an arbitrary number of sequentially alternating two types of sections, leading to the generation on the same rotating shaft of the same number of counterpropagating resonant rotating waves. A concomitant effect is the technological simplicity, efficiency and reliability of the device.

At the same time, traveling rotating resonant waves are excited on one rotating shaft in the medium being processed, alternately changing the directions of rotation when moving in the axial direction, which creates the oncoming movement of the rotating layers and improves the quality of the dispersion of the product without any additional technological and energy costs. Multisectional shaft increases its length and, accordingly, the throughput of the dispersant.

The essence of the above is illustrated by drawings, in which Figs. 1, 2, 3 show a diagram of a resonant siren generating counterpropagating rotating waves taken from a single rotor, Fig. 4 shows the eigenmodes of the excited resonant oscillations, Fig. 5 shows the corresponding natural frequencies, in Fig.6, 7 - amplitude-frequency and phase-frequency characteristics of forced oscillations, Fig.8 is a diagram of the excitation of the resonator, Fig.9 is a diagram of the effect of gas flows flowing from the holes of the rotor on the stator holes, Fig.10, 11 - nomograms of structural pairs Siren measures: resonant frequencies of oscillations of the treated dispersed medium, rotor speeds, outer and inner stator radii, and the number of stator openings.

The resonant siren on rotating counterpropagating waves (Figs. 1, 2, 3) contains a coaxially mounted hollow cylindrical stator 1 in the form of a circular concentric acoustic resonator and a hollow rotor 2 rotating inside it. Through adjacent openings are made in adjacent surfaces of the stator and rotor. The stator is uniform throughout the longitudinal dimension and has n holes. The rotor in length consists of an arbitrary number of alternating segments containing n + 1 (figure 1, 2) and n-1 (figure 1, 3) holes, respectively. The rotor rotates evenly by the drive 3 and contains means for supplying a liquid or gaseous mixture inside it under a slight pressure 4. It is possible in this quality to use only the rotor impeller, like centrifugal pumps. The output nozzles 5 are located tangentially on the outer radius of the stator and are oriented in the direction of the traveling wave, along or against the rotation of the rotor, Fig.2, 3, respectively. For the convenience of product output, they are all oriented in the same transverse direction. Therefore, the nozzles located in the sections of the forward and reverse rotating waves are diametrically opposite (Figs. 1, 2, 3). In the practical use of a dispersant for a heavy, especially liquid dispersed medium, it is advisable to direct the nozzles vertically downwards for the finished product to flow into the filter with further transportation to storage tanks.

The main meaning of the invention is to combine a radial siren as the most powerful source of acoustic vibrations and the phenomenon of resonance as a method of accumulating vibrational energy. It is compositionally rational to surround the siren with a circular cylindrical resonator. However, the traditional siren generates standing waves - axisymmetric vibrations, and the thickness of the resonator having the corresponding natural frequency is unrealistically large. To match the frequency of the siren perturbation and the natural frequencies of the oscillations of the resonator, it is not necessary to excite an axisymmetric standing wave, but a two-node traveling wave. This is most functional for mixing and grinding particles of media to obtain the desired disperse system, because stagnant processing zones are eliminated and flowing movement of the product is carried out. To excite a traveling rotating wave, a special form of perforation of its rotor is proposed. As a result, a two-node asymmetric eigenoscillation wave with the lowest eigenfrequencies is easily excited in the resonator in the circumferential direction. This wave is traveling, in contrast to the standing wave generated by the traditional siren. Moreover, by choosing the perforation of the rotor, the direction of its rotation can easily be reversed with the same rotating rotor. Three main results are obtained from this approach. First: the proposed siren, even without a resonator, by itself, can be used as an indicator of all-round visibility on weakly attenuated low-frequency waves in acoustics. Second: a new type of perforation opens up the possibility of using resonance with a siren as a pathogen. Third: allows you to receive oncoming resonant traveling waves on one rotating shaft of the rotor. The latter is especially important for mixing and grinding liquid or gaseous media.

So, the vibrations of a liquid or gaseous mixture are carried out in an annular cylindrical cavity - a stator. Axisymmetric natural oscillations of the liquid (gas) in the annular cavity (Fig. 4, dashed line), excited by traditional sirens with the same perforation of the rotor and stator, have natural frequencies that are infinitely increasing with decreasing thickness (Fig. 5, dashed line, where ρ - the ratio of the inner radius of the concentric acoustic resonator to the outer, 0 <ρ <1, α = α (ρ) is the root of the corresponding frequency equation), which would require an excessive increase in rotor speed and a decrease in the perforation pitch (i.e., increase equal number of holes in the adjacent surfaces of the rotor and stator) to achieve a resonant excitation frequency and increase the thickness of the resonator to reduce the fundamental frequency of the axisymmetric oscillations. In this regard, it is advisable to create a resonant traveling two-node wave in the stator / Sviyazheninov E.D. Spectral methods for solving problems on the oscillations of dissipative mechanical and electrodynamic systems with distributed parameters: Dis ... doct. tech. Sciences, St. Petersburg, 1994, 432 pp. /. Two-node in the tangential direction, the natural form of oscillation in the annular cylindrical region (Fig. 4, solid line) has the lowest natural oscillation frequencies of all existing (Fig. 5, solid line), which opens the way to the use of resonance in a circular concentric stator of small thickness with available low rotor speeds and not too small perforation step. When resonance is implemented, it is not necessary to pump the medium to be processed into the resonator under high pressure to create sufficient powerful excitation pulses. Even with a weak inlet pressure on the resonator, intense acoustic vibrations will occur in it due to in-phase pumping and accumulation of vibrational mechanical energy in the medium. The main (lowest) resonance of the two-node oscillation mode was selected, which has the lowest frequency and provides the greatest amplification of oscillations, which follows from the amplitude-frequency characteristic for oscillations single-period along the circumference (Fig. 6). On the phase-frequency characteristic (Fig. 7), it is seen how the phase conditions of the optimal pumping of energy into the oscillatory system are satisfied at the resonance.

To excite a non-axisymmetric traveling resonant wave, an unconventional siren scheme is proposed, namely a new type of its perforation. As before, the holes on the rotor and stator are evenly distributed in the circumferential direction, but the number of rotor holes is one more (to create a direct, or incident, traveling wave, coinciding with the direction of rotation of the rotor) or one less (to get the opposite or counter , waves opposite to the direction of rotation of the rotor) than on the stator (Fig. 8).

Device operation

When the rotor rotates uniformly with an angular velocity ω _p , on the surface of which there are n + 1 or n-1 radial gas flows uniformly spaced from each other, each of the n slots on the stator surface experiences alternating pressure pulsations (Fig. 8).

Let at the initial moment one of the slots of the rotor and stator coincide (Fig. 9). The pressure pulse from the gas flowing out of the rotor is transmitted to the stator resonator. When the rotor rotates through an angle

(in a direct wave) or on

(at the reverse) a pressure shock will occur at the neighboring hole of the resonator - in the direction of rotation of the rotor or against. When the rotor is rotated through an angle (n + 1) δ = 2π / n or by nδ = 2π / (n-1), a pressure impulse runs around the circle exactly once in the forward or reverse direction. Thus, the angular velocity of rotation of the pressure pulse on the inner surface of the resonator is ω = (n + 1) ω _p - in the forward and ω = (n-1) ω _p - in the opposite direction.

ротора 2 (фиг.1, 2, 3) находится из условия достижения резонанса:Final speed

rotor 2 (figure 1, 2, 3) is found to achieve resonance:

f = ν / (n + 1)

- for a siren on a direct traveling wave and

f = ν / (n-1)

, n - число отверстий статора.- for a siren on a reverse traveling wave, where ν is the natural frequency of the acoustic oscillations of the resonator,

, n is the number of stator holes.

From the rotor side, a rapidly rotating excess pressure pulse acts on the surface of the stator resonator. The harmonic composition of a single pulse is a series of circumferential harmonics, of which the two-node (single-period) in the tangential direction has the largest amplitude. It is this fundamental harmonic that serves to excite the resonant traveling wave of oscillations - a single-period (two-node) in the tangential direction of the sine wave. The amplitude-frequency characteristic of the two-node oscillations of a viscous heat-conducting compressible liquid medium in the resonator (Fig.6) shows that the first (main) resonance provides the greatest amplification of the oscillations. For an annular cylindrical resonator 1 (1, 2, 3) of the outer radius R and the ratio of the inner radius to the outer ρ, the frequency of the fundamental tone is equal to:

where c is the speed of sound in the fluid (gas) filling the rotor, α = α (ρ) is the first (lowest) root of the transcendental frequency equation:

where J ₁ (α), N ₁ (α) are the first-order Bessel and Neumann functions, respectively.

. Фиг.5 показывает также, что собственные частоты осесимметричных колебаний неограниченно увеличиваются с ростом ρ (штриховая линия), тогда как частоты двухузловых - монотонно убывают с ростом ρ (и асимптотически приближаясь к α=1), что и требуется для согласования сирены, - возбудителя, с акустической камерой, - резонатором.The function α = α (ρ) from formula (1) is represented by a graph (Fig. 5, solid line) for all real specific ratios of the inner radius of the concentric resonator to the outer 0 <ρ <1. In Fig. 5, the first subscript i of the function α _ij (ρ) means that it is the i-th root of the equation (2) in increasing order, and the second subscript k shows the number of pairs of nodes of the excited waveform in the tangential direction. So, i = 1 corresponds to the first (lower) root of the equation, k = 1 corresponds to the two-node (with one nodal diameter) eigenoscillation implemented in the device, while k = 0 is axisymmetric, i.e. independent of the angular coordinate. Both of these forms are depicted in figure 4. Figure 5 shows that when ρ = 0 we have a particular case of a continuous resonator, which is indicated by the superscripts (c) for the corresponding values of

. Figure 5 also shows that the eigenfrequencies of axisymmetric oscillations increase unlimitedly with increasing ρ (dashed line), while the frequencies of two-node ones monotonically decrease with increasing ρ (and asymptotically approaching α = 1), which is required for matching the siren of the pathogen , with an acoustic camera, a resonator.

To conduct a design analysis and calculation of structural parameters according to the above calculation formulas, nomograms of a resonant siren are constructed (Figs. 10, 11). It is most easy to select its main structural parameters from them: resonant frequencies of oscillations of the treated dispersed medium, rotor speeds, outer and inner radii of the stator — the resonant sounding chamber, and the number of stator openings. For example, we set the resonant vibrational frequency ν and the ratio of the internal and external radii of the resonator ρ. Then, from the curve ν (R), we determine the corresponding external radius R, and from the family of lines ν (f) we select a combination of perforation n and the number of rotor revolutions f. It can be seen from the nomograms that for real-life practical mixtures, the siren parameters are easily implemented. So, as a drive, it is quite possible to use the most common low-speed asynchronous electric motors.

An example of calculating the parameters of a resonant siren generating counterpropagating rotating waves taken from a single rotor

Let the medium to be treated be oil, and it is required to excite the frequency of its processing ν = 500 Hz in the resonator with the ratio of the internal radius to the external ρ = 0.5.

Then, along the curve ν (R) of Figs. 10, 11, we find the necessary external radius of the resonator chamber: R = 58 cm. According to the family of lines ν (f) or by the formulas:

f = ν / (n + 1)

- for a siren on a direct traveling wave and

f = ν / (n-1)

- for a siren on a reverse traveling wave, we obtain possible combinations of the number of holes n and the number of rotor revolutions f:

n, number: 10 20 30 40 50 60 70 80 90 100;

when using a direct traveling wave:

f, r / c: 50 25 17 13 10 8 7 6 6 5;

when using a reverse traveling wave:

f, r / c: 56 26 17 13 10 8 7 6 6 5.

It can be seen from the presented table that for real practically important cases of a sufficiently large number of stator openings, the rotor rotation frequency, which provides resonant excitation of a rotating wave, either direct or counter, is the same. Consequently, counterpropagating rotating waves, simultaneously located in the resonance condition, are removed from one multisectional rotor. An arbitrary, theoretically unlimited number of alternating counterpropagating resonant rotating waves gives a very simple reliable high-performance effective device for producing high-quality dispersed systems.

References

1. Bergman L. Ultrasound and its application in science and technology. M .: Publishing house of foreign countries. L-Ry, 1957. 726 p.

2. Sviyazheninov E.D. Hydroacoustic siren. Patent for invention No. 2284229. Priority 04/28/04. (prototype).

3. Sviyazheninov E. D. Spectral methods for solving problems on the oscillations of dissipative mechanical and electrodynamic systems with distributed parameters: Dis ... doct. tech. sciences. St. Petersburg, 1994, 432 p.

Claims (1)

A resonant counterpropagating siren, including a coaxially mounted cylindrical stator in the form of a concentric acoustic resonator and a hollow rotor, in adjacent surfaces of which there are through slotted holes evenly spaced around the circumference, a drive for uniform rotation of the rotor, a means for supplying a liquid or gaseous mixture to the rotor and outlet pipes for outputting the product, characterized in that the hollow rotor of the siren consists of successive longitudinal sections made with the number of holes different per unit of the number of stator openings for the implementation of a traveling rotating resonant wave of oscillations in the resonator — direct (passing), relative to the direction of rotation of the rotor — in the case of one more and inverse (counter), in the case of one less, the number of such segments of the rotor is arbitrary, and they are sequentially alternated to ensure counter-rotation of resonant traveling waves at adjacent section boundaries, all output nozzles are tangent to the outer surface of the stator in the direction of the corresponding traveling waves and are equally directed in the transverse direction, while the device parameters are selected from the expressions
f = ν / n,

where ν is the frequency of the generated hydroacoustic or acoustic vibrations, respectively, in a liquid or gaseous medium in the resonator,
f is the rotor speed,
n is the number of stator holes,
R is the outer radius of the resonator,
C is the speed of sound in a liquid or gaseous medium entering the resonator,
α is the lower root of the transcendental equation

where J ₁ , N ₁ - respectively, the Bessel and Neumann functions of the first order,
ρ is the given ratio of the inner radius of the concentric resonator to the outer R.

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