RU171493U1 - MIXING DEVICE FOR MIXER - Google Patents

Abstract

The technical solution relates to the design of mechanical mixers for simultaneous macro- and micro-mixing of highly viscous, non-Newtonian and structured liquids, suspensions and emulsions and can be used in chemical, petrochemical, paint and varnish, pharmacological, food and other industries. The technical result of the proposed design of the mixing device is intensification the process of micromixing fluid flows radially passing through perforations the cylinder and the diffuser due to transverse vibrations with a large amplitude of these flows. The technical result is achieved in that the mixing device for the mixer includes a perforated diffuser and a propeller mixer placed in it, at the ends of the blades of which a perforated cylinder is fixed, and the diffuser consists of two parts - upper, rigidly fixed to the lid of the mixer, and lower connected to the upper vertical strings evenly spaced around their circumference.

Description

The technical solution relates to the design of mechanical mixers for simultaneous macro- and micro-mixing of highly viscous, non-Newtonian and structured liquids, suspensions and emulsions and can be used in chemical, petrochemical, paint and varnish, pharmacological, food and other industries.

The apparatus AP2-4 is known, consisting of a tank with a mixing device (low-speed mixer) and an elliptical bottom, a jacket for cooling or heating the processed product, a rotary mixing device of the GART type of a rotary-type sonar mixer and an electric motor. The rotor head has a vortex chamber formed by a rotating rotor and a fixed stator. When the rotor rotates, the fluid passes between the teeth of the rotor and stator at high speed. In this case, effective mixing, dispersion, homogenization of particles processed by solid and liquid materials occurs with simultaneous stirring by a low-speed mixer (A. Timonin. Fundamentals of design and calculation of chemical-technological and environmental equipment. Handbook. 2nd edition, revised and supplemented, T. 2 - Kaluga: publishing house N. Bochkareva, 2002, p. 906, 907).

The reasons that impede the achievement of the desired technical result include insufficient mixing efficiency, due to the fact that macro mixing of the liquid with a slow-moving mixer and micro mixing in the rotary mixing device occurs in different places of the tank volume, which reduces the mixing speed, especially when mixing highly viscous, non-Newtonian and structured liquids , since the structure is destroyed and the effective viscosity decreases in the central zone, where the low-speed mixer is located, and in riferiynoy zone of operation of the rotary liquid mixing device structure and high viscosity non-Newtonian effective persist that prevents micromixing.

A known design of a rotary apparatus of hydropercussion, comprising a housing inside which a stator and a rotor are concentrically mounted with slots made on the side walls in the form of channels in the form of subsonic nozzles with a constriction adjacent to expanding cavities having concave surfaces, while the rotor is divided into two parts : the external and internal annular recess in which the stator is placed, while the slots in the form of subsonic nozzles are made in the stator, and the slots in the form of expanding cavities are made on the outer part of the rotor, etc. why on the inner part of the rotor are blades that create centrifugal forces in the processed stream (description of the invention to patent No. 2114689 B01F 7/12, 1998).

The reasons that impede the achievement of a given technical result include insufficient micromixing efficiency, especially when mixing highly viscous, non-Newtonian and structured liquids, suspensions and emulsions, since the nozzles and slots in the rotor do not oscillate in the stator.

The closest technical solution for the totality of features to the claimed object and adopted as a prototype is the design of a mixing device, including a perforated diffuser and a propeller stirrer placed in it, while a perforated cylinder is fixed at the ends of the propeller blades to intensify the mixing process [description of the invention to the USSR copyright certificate No. 413972, B01F 7/22, 1974].

The reasons that impede the achievement of the desired technical result include the insufficient intensity of the micromixing process, since vibration is not transmitted to the flows of the mixed fluid, especially highly viscous, structured and non-Newtonian, since the perforated cylinder and diffuser do not oscillate.

The technical result of the proposed design of the mixing device is to intensify the process of micromixing of fluid flows passing radially through the holes of the perforated cylinder and the diffuser due to transverse vibrations with a large amplitude of these flows.

The technical result is achieved by the fact that the mixing device for the mixer includes a perforated diffuser and a propeller mixer placed in it, at the ends of the blades of which a perforated cylinder is fixed, the diffuser consists of two parts - the upper one, rigidly fixed to the mixer cover, and the lower one connected to the upper vertical strings evenly spaced around their circumference. The mass of the lower part of the diffuser is determined by the expression

where m _n is the mass of the lower part of the diffuser, kg;

π is the number of Archimedes;

ρ _{with the} density of the material of the jet, kg / m ³ ;

ρ _n - the density of the material of the lower part of the diffuser, kg / m ³ ;

ρ _W - the density of the mixed fluid, kg / m ³ ;

k is the number of strings in the perforated cylinder, pcs .;

n is the number of perforations;

ω is the angular speed of rotation of the mixer, r / s;

l is the length of each string, m;

d is the thickness of each string, m,

moreover, on the outside of the adjacent ends of the diffuser parts, bushings with studs are installed.

Separation of the diffuser into two parts: the upper one, rigidly fixed to the mixer cover, and the lower one, which allow them to be joined together uniformly around the circumference by strings whose vibrations from the jets of the mixed liquid formed in the holes of the perforated cylinder, additionally mix the liquid at the micro level and intensify the mixing process itself.

Creating the mass of the lower part of the diffuser, obeying the expression (1), allows you to translate the vibration of the strings into resonance mode, when the natural frequency of the vibration of each string is described by the equation [Elementary textbook of physics. Edited by G.S. Lansberg. Edition 10 revised. T. 3. - M .: Nauka, 1986, p. 127]

where f is the tension force of each string, N;

ρ _s is the density of the string material, kg / m;

l is the length of each string, m;

d is the thickness of each string, m

Since the tension force f each string is equal to the weight of the lower part of the diffuser minus the Archimedes force in the mixed fluid

and the frequency of hydroshocks of fluid flows passing through the holes of the perforated cylinder about each string

then equating the right-hand sides of equations (2) and (4), ensuring the equality of the natural frequency of the string’s vibrations with the frequency of the driving force, taking into account equation (3), after algebraic transformations we obtain expression (1) for the mass of the lower part of the diffuser, providing a resonant mode of string vibrations with large amplitude intensifying the process of micro-mixing of fluid flows passing through the holes of the perforated cylinder and the gap between the strings of the diffuser.

The installation of bushings with studs on the outside of the adjacent ends of the diffuser parts prevents the strings from twisting together with the lower part of the diffuser under the action of a rotating fluid flow, which preserves the high-amplitude resonant vibration mode of the strings and intensifies the micromixing process.

The drawing shows a diagram of a mixer with the proposed design of the mixing device.

The mixer shown in the drawing includes a housing 1 with a cover 2 and a bottom 3, a drive 4 connected to a shaft 5, on which a propeller mixer 6 is mounted, on the blades of which a perforated cylinder 7 is mounted. Axially symmetrically mounted with a shaft 5 and a perforated cylinder 7 the diffuser, divided into two parts: the upper 8 and the lower 9. The upper 8 and lower 9 parts of the diffuser are interconnected by vertical strings 10, that is, the lower part 9 of the diffuser hangs on the strings 10, creating a tensile force in them, while the mass of the lower part 9 diffuser op edelyaetsya expression (1).

To prevent the angular shift of the lower part 9 of the diffuser and the twisting of the strings 10 relative to the upper part 8 of the diffuser from the outer side of the adjacent ends of both parts 8 and 9 of the diffuser, to which the ends of the strings 10 are attached, bushings 11 with studs 12 are installed on diametrically opposite sides. the diffuser is rigidly attached by rods 13 to the cover 2. The vertical position of the strings 11 is regulated by nuts 14.

A mixing device is prepared for operation as follows.

On the cover 2 removed from the housing 1, the upper part 8 of the diffuser is mounted on the rods 13. The upper ends of the strings 10 are fixed on the lower end evenly around the circumference of this end. The required mass of the lower part 9 of the diffuser is calculated according to the expression (1), and also the lower part 9 of the diffuser is connected to it uniformly around the upper end so that it hangs on the strings 10. Insert the studs 12 into the bushings 11 and adjust the vertical position of the strings by tightening the nuts 14 10 so that the tension of all strings 11 is the same.

Then, a shaft 5 with a mixer 6 is mounted in the cover 2 and the cover 2 is hermetically connected to the housing 1. Install the drive 4 on the cover 2 and connect it to the shaft 5, pour liquid into the housing and turn on the drive 4, which transfers rotation to the shaft 5, the mixer 6 and a perforated cylinder 7 with an angular velocity of rotation ω.

The mixing device operates as follows. The drive 4 is turned on, which transmits rotation to the shaft 5 with a mixer 6 and a perforated cylinder 7 with an angular rotation speed ω. Rotating, the blades of the mixer 6 discard part of the flow of the stirred fluid in the radial direction, which passes through the holes in the perforated cylinder 7, striking the strings 10 attached between the upper 8 and lower 9 parts of the diffuser. In one second, each string 10 receives the number of hydroshocks equal to the product of the number of holes n in cylinder 7 by the number of revolutions ω, that is, the frequency of forced vibrations of the string will be described by the equation

ν = n⋅ω.

Since the mass of the lower part 9 of the diffuser suspended on the strings 10 corresponds to expression (1), that is, the tension force of each string 10 is such that the natural frequency of transverse vibrations of each string 10 corresponds to equation (2), then all strings (10) make transverse forced vibrations with a resonant frequency equal to the frequency of water hammer on them radial flow of the mixed fluid.

With resonant vibrations, the amplitude of the transverse vibrations of the strings 10 increases sharply, which provides strong micro-mixing of the liquid layers and helps to intensify the operation of the mixing device of the proposed design.

Example.

It is necessary to mix the liquid in the housing 1 having a density ρ _W = 1000 kg / m ³ . The number of revolutions of the agitator blades 6 ω = 5 r / s. The number of slotted longitudinal perforations in the perforated cylinder is 7 n = 30. The lower part 9 of the diffuser is made of steel sheet with a density ρ _n = 8000 kg / m ³ . The strings 10 are also steel, their length l = 0.15 m, thickness d = 5⋅10 ^-4 m, number k = 30, and the material density of steel strings 10 is ρ _m = 8000 kg / m ³ .

Then, according to expression (1), the mass of the lower part 9 of the diffuser should be equal to

Each of the 30 strings 10 will have a pulling force

,

,

where the last factor takes into account the decrease in tension due to the force of Archimedes.

Then the natural frequency of the transverse vibrations of each string 10 according to equation (2) will be

,

,

and the frequency of forced oscillations according to equation (3) will be

ν = n⋅ω = 150 Hz,

that is, with the mass of the lower part 9 of the diffuser calculated according to expression (1), the natural frequency of the transverse vibrations of the strings 10 coincides with the frequency of the forced vibrations of the shocks of the radial jets of liquid leaving the holes of the perforated cylinder 7.

Thus, the implementation of the diffuser 7 of two parts: the upper 8 and lower 9 and connecting them together with strings 10 with the mass of the lower part 9 of the diffuser, defined by expression (1), allows due to the resonant transverse vibrations of the strings 10 with high amplitude, when the natural frequency the oscillation of these strings coincides with the frequency of hydroshocks of the radial flows of the mixed liquid, directed by the blades of the mixer 6 through the holes of the perforated cylinder 7 to the strings 10, to provide micro-mixing of the liquid and to intensify the mixing process studies at both macro and micro levels.

Claims (13)

A mixing device for the mixer, including a perforated diffuser and a propeller mixer placed in it, at the ends of the blades of which a perforated cylinder is fixed, characterized in that the diffuser consists of two parts: the upper one, rigidly fixed to the mixer cover, and the lower one, connected to the upper one evenly spaced their circles with vertical strings, while the mass of the lower part of the diffuser is determined by the expression

where m _n is the mass of the lower part of the diffuser, kg; π is the number of Archimedes; ρ _{with the} density of the material of the strings, kg / m ³ ; ρ _n - the density of the material of the lower part of the diffuser, kg / m ³ ; ρ _W - the density of the mixed fluid, kg / m ³ ; k is the number of strings in the perforated cylinder, pcs .; n is the number of perforations in the perforated cylinder; ω is the speed of rotation of the mixer, r / s;

- the length of each string, m; d is the thickness of each string, m, moreover, on the outside of the adjacent ends of the diffuser parts, bushings with studs are installed.

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