RU2238435C1 - Liquid-packed ring machine - Google Patents

Abstract

FIELD: mechanical engineering; vacuum and compression facilities.

SUBSTANCE: invention can be used in liquid-packed ring machines. Proposed machine has housing with cylindrical inner bore, end face covers with suction and delivery ports working wheel with hub and blades installed eccentric ally in bore, and thin-walled bushing with longitudinal slots on inner surface installed concentrically in bore for rotation. Rear wall of each slot in direction of rotation is arranged square to surface of bushing, and front wall is mated with rear at its base forming acute angle and is made flat or curvilinear. Eccentricity ξ is determined from definite dependence.

EFFECT: increase accuracy of calculation of eccentricity, reduced time taken for and cost of finishing operations aimed at reduction specific power of liquid-packed ring machine.

1 dwg

Description

The invention relates to vacuum and compressor technology and can be used in liquid ring machines (LCD).

Known liquid ring machine (RU 2000480 C1, F 04 C 7/00, F 04 C 19/00, 09/07/1993), comprising a housing with a cylindrical inner bore, end caps with suction and discharge windows and an impeller eccentrically mounted in the bore with a hub and vanes, in which the eccentricity is determined from the ratio

where ε is the relative eccentricity, b / p;

e - absolute eccentricity, m;

ψ is the blocking factor of the volume of the impeller, b / r;

and - the minimum value of the immersion of the blades of the impeller in the liquid ring (at the place of greatest removal of the impeller from the inner bore of the housing), m;

ν = r ₁ / r ₂ , b / p;

r ₁ = radius of the impeller hub, m;

r ₂ = outer radius of the impeller, m;

δ = Δ / r ₂ , b / p;

Δ is the minimum clearance between the blades of the impeller and the inner bore of the casing (the minimum height of the bladeless space), m;

ζ = b / b ₀ , b / p;

b - width of the bezoplatochny space, m;

b ₀ - the length of the rotor without taking into account the thickness of the stiffeners, m;

k ₁ - empirical coefficient taking into account the departure of the inner surface of the liquid ring from the hub of the impeller in cross section with a minimum height of the bladeless space, b / r;

k ₁₁ is an empirical coefficient characterizing the ratio of the average circumferential velocity of the fluid flow in the bladeless space at the place of least distance of the impeller from the inner bore of the casing to the peripheral speed of the ends of the blades of the impeller, b / r;

k ₂₂ is an empirical coefficient characterizing the ratio of the average peripheral velocity of the fluid flow in the bladeless space at the place of greatest distance of the impeller from the inner bore of the casing to the peripheral speed of the ends of the blades of the impeller, b / r.

The disadvantage of this design is a significant loss of power on the friction of the liquid ring on the inner bore of the housing.

Also known is a liquid ring machine (SU 1629611, F 04 C 7/00; F 04 C 19/00, publ. 23.02.91), comprising a housing with a cylindrical inner bore, end caps with suction and discharge windows, eccentrically mounted in the bore an impeller with a hub and blades, as well as a thin-walled sleeve with longitudinal grooves on the inner surface, which is concentrically mounted in a bore with the possibility of rotation. When the impeller rotates under the action of centrifugal forces, the fluid is discarded to the periphery, forming a fluid ring that rotates the thin-walled sleeve with a frequency close to the rotational speed of the impeller. This leads to an increase in the average velocity of the fluid flow in the brushless space in the tangential direction and to a decrease in the gradient of the fluid velocity in the radial direction. Due to this, liquid friction in the ring and, consequently, power consumption for the LCD drive are reduced.

The disadvantage of this design is the lack of consideration of the influence of a thin-walled sleeve with grooves rotated by the liquid ring on the change in the flow velocity of the liquid in the jacketless space of the LCM, as well as the accuracy of determining the eccentricity value.

An object of the invention is to reduce the specific power of the LCD.

The technical result is achieved by the fact that in a liquid-ring machine containing a housing with a cylindrical inner bore, end caps with suction and discharge windows, an impeller eccentrically mounted in the bore with a hub and vanes, and a thin-walled sleeve concentrically installed in the bore with the possibility of rotation longitudinal grooves on the inner surface, while the rear wall in the direction of rotation of each groove is normal to the surface of the sleeve, and the front wall is mated back at its base to form an acute angle and is flat or curved, and the magnitude of the eccentricity ε is determined from the following relation:

where ε is the relative eccentricity, b / p;

e - absolute eccentricity, m;

ψ is the blocking factor of the volume of the impeller, b / r;

and - the minimum value of the immersion of the blades of the impeller in the liquid ring (at the place of greatest removal of the impeller from the inner bore of the housing), m;

ν = r ₁ / r ₂ , b / p;

r ₁ = radius of the impeller hub, m;

r ₂ = outer radius of the impeller, m;

δ = Δ / r ₂ , b / p;

Δ is the minimum clearance between the blades of the impeller and the inner bore of the casing (the minimum height of the bladeless space), m;

ζ = b / b ₀ , b / p;

b - width of the bezoplatochny space, m;

b ₀ - the length of the rotor without taking into account the thickness of the stiffeners, m;

k ₁ - empirical coefficient taking into account the departure of the inner surface of the liquid ring from the hub of the impeller in cross section with a minimum height of the bladeless space, b / r;

k ₁₁ is an empirical coefficient characterizing the ratio of the average circumferential velocity of the fluid flow in the bladeless space at the place of least distance of the impeller from the inner bore of the casing to the peripheral speed of the ends of the blades of the impeller, b / r;

k ₂₂ is an empirical coefficient characterizing the ratio of the average peripheral velocity of the fluid flow in the bladeless space at the location of the greatest distance of the impeller from the inner bore of the casing to the peripheral speed of the ends of the blades of the impeller, b / r;

k _W is an empirical coefficient that takes into account, ceteris paribus, an increase in the average fluid flow rate in a space without a gap when a thin-walled sleeve is introduced into a cylindrical internal groove, b / r.

Recommended ranges of parameter values included in the ratio for determining the eccentricity value:

0.7 ≤ ψ ≤ 0.9,

0.005 ≤ a / r ² ≤ 0.015,

0.35≤ ν≤ 0.60,

0.005 ≤ δ ≤ 0.030.

The empirical coefficients k ₁ , k ₁₁ , k ₂₂ and k _{W are} proposed to be determined by the following relationships:

where E _u = (p _n- p _sun ) / pu $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ - Euler number, b / r;

τ = r _n / r _vs - nominal degree of pressure increase, b / r;

r _n , r _bc - nominal pressure, respectively, in the discharge and suction nozzles, Pa;

p is the density of the working fluid, kg / m ³ ;

u ₂ = 2π r ₂ n _pk - peripheral speed of the ends of the blades of the impeller, m / s;

n _pk - the frequency of rotation of the impeller, s ^-1 .

The value of k _{1 is} determined for 1 ≤ τ ≤ 3 in the range 0.2 ≤ Е _u ≤ 0.85 and for 3 <τ ≤ 7.5 in the range 0.2 ≤ Е _u ≤ 0.55. For physical reasons, there cannot be k ₁ > 1, therefore, if as a result of calculations for this dependence the value k ₁ > 1, then take k ₁ = 1

k ₁₁ = (k _11rad -kμμ) k _oc ,

where k _11rad = (1,583 · 10 ^-3 · β $\genfrac{}{}{0ex}{}{}{\text{2}}$ +0.598) is an empirical coefficient that takes into account the influence of the output angle of inclination of the blades of the impeller on the peripheral velocity of fluid flow in the bladeless space at the place of least distance of the impeller from the inner bore of the housing, b / r;

β ₂ - the value of the output angle of inclination of the blades of the impeller, deg;

kμ is an empirical coefficient that takes into account the influence of the viscosity of the working fluid on the speed of its flow in the space without a gap, kμ = 3.59;

μ is the dynamic viscosity of the working fluid, Pa · s;

k _oc = (l-3 · 10 ^-3 / b) is an empirical averaging coefficient that takes into account the non-uniformity of the peripheral velocity of the fluid flow across the width of the bladeless space, b / p; defined for values b ≥ 0.03 m;

k ₂₂ = (kψ -kμμ) k _{oc oc kc} ;

where kψ = {[1- (1-ν) / π · tgβ ₂ ] · μ _z } ^1/2 - coefficient taking into account the influence of the shape and number of impeller blades, b / p;

μ _z = [1 + π · sin β _2/2 · z · (1-ν)] ^-1, b / p;

π ≈ 3.1416;

z is the number of impeller blades, b / r;

k _sun = (1,081-2,017 · 10 ^-6 · R _sun ) is an empirical coefficient that takes into account the influence of the suction pressure on the peripheral flow rate of the liquid in the bladeless space at the place of the greatest distance of the impeller from the inner bore of the housing, b / r.

Here k ₁ , k ₁₁ and k _{22 are} defined for the following LCD conditions:

p _sun ≤ 100 kPa, 100 kPa ≤ p _n ≤ 115 kPa, 1 · 10 ^-3 Pa · s≤ μ ≤ 80 · 10 ^-3 Pa · s,

870 kg / m ³ ≤ p ≤ 1200 kg / m ³ .

For other modes of operation of the LCD, the values of these coefficients can be determined additionally.

k _W = 1 + 2.5 · 10 ^-3 (u _W / u ₂ ) + 7.5 · 10 ^-2 (u _W / u ₂ ) ² ;

because:

u _W = 2π r _W n _W - peripheral speed of the inner surface of the sleeve, m / s;

r _W is the radius of the inner surface of the sleeve, m;

n _W is the rotational speed of the sleeve, s ^-1 ;

follows that:

k _W = 1 + 2.5 · 10 ^-3 (r _W n _W / r ₂ n _pk ) + 7.5 · 10 ^-2 (r _W n _w / r ₂ n _pk ) ² .

For physical reasons, the value of n _W can be 0≤ n _W ≤ n _pk . This means that the coefficient k _w reaches its maximum value at n _w = n _pk and is

k _{W max} = 1 + 2.5 · 10 ^-3 (r _W / r ₂ ) + 7.5 · 10 ^-2 (r _W / r ₂ ) ² ,

and the minimum, with n _W = 0 (thin-walled sleeve is stationary) and is k _ktmin = 1.

The invention is illustrated in the drawing, which shows a section of the LCD.

The liquid ring machine comprises a housing 1 with a cylindrical inner bore 2, end caps 3 with suction windows 4 and pressure windows 5, an impeller 6 mounted eccentrically in the bore 2 with a hub 7 and vanes 8, and also rotatably mounted in the bore 2 with rotation thin-walled sleeve 9 with longitudinal grooves 10 on the inner surface, while the rear wall in the direction of rotation of each groove is normal to the surface of the sleeve, and the front wall is mated to the rear at its base with mations acute angle and is flat or curved, and the eccentricity ε is determined from the following relation:

where ε is the relative eccentricity, b / p;

e - absolute eccentricity, m;

ψ is the blocking factor of the volume of the impeller, b / r;

and - the minimum value of the immersion of the blades of the impeller in the liquid ring (at the place of greatest removal of the impeller from the inner bore of the housing), m;

ν = r ₁ / r ₂ , b / p;

r ₁ = radius of the impeller hub, m;

r ₂ = outer radius of the impeller, m;

δ = Δ / r ₂ , b / p;

Δ is the minimum clearance between the blades of the impeller and the inner bore of the casing (the minimum height of the bladeless space), m;

ζ = b / b ₀ , b / p;

b - width of the bezoplatochny space, m;

b ₀ - the length of the rotor without taking into account the thickness of the stiffeners, m;

k ₁ - empirical coefficient taking into account the departure of the inner surface of the liquid ring from the hub of the impeller in cross section with a minimum height of the bladeless space, b / r;

k ₁₁ is an empirical coefficient characterizing the ratio of the average circumferential velocity of the fluid flow in the bladeless space at the place of least distance of the impeller from the inner bore of the casing to the peripheral speed of the ends of the blades of the impeller, b / r;

k ₂₂ is an empirical coefficient characterizing the ratio of the average peripheral velocity of the fluid flow in the bladeless space at the place of greatest distance of the impeller from the inner bore of the casing to the peripheral speed of the ends of the blades of the impeller, b / r;

k _W is an empirical coefficient that takes into account, ceteris paribus, an increase in the average velocity of fluid flow in a space without a gap when a thin-walled sleeve is introduced into a cylindrical internal groove, b / r.

The liquid ring machine operates as follows.

When the impeller 6 rotates with the hub 7 and the blades 8 inside the housing 1, it is discarded to the periphery by the action of centrifugal forces, forming a fluid ring that rotates the thin-walled sleeve 9, interacting with the longitudinal grooves 10 on its inner surface. Between the inner surface of the liquid ring, the end caps 3, the hub 7 and the blades 8 of the impeller 6, cells are formed, the gas volume of which changes when the impeller 6 rotates around its axis due to the presence of eccentricity, while the volume first increases and gas flows through the suction window 4 into LCD, and then decreases and the compressed gas through the discharge window 5 is removed from the LCD. The maximum volume is the cell farthest from the inner bore 2 of the housing 1 or the inner surface of the thin-walled sleeve 9, rotated by the liquid ring with a frequency close to the rotational speed of the impeller 6. The presence of a rotating thin-walled sleeve 9 leads to an increase in the average fluid flow rate in the space without tangential direction and a decrease in the gradient of the fluid velocity in the radial direction. This leads to a decrease in liquid friction in the ring and the specific power on the LCD drive. Due to the establishment of the impeller 6 relative to the inner bore 2 of the housing 1 with an eccentricity ε, the value of which is determined from the proposed ratio, this cell has the maximum possible gas volume, in addition, guaranteed immersion of the blades 8 of the impeller 6 in the liquid ring, which prevents the flow of gas between cells.

Thus, the invention allows to reduce the specific power of the LCD by increasing the accuracy of calculating the magnitude of the eccentricity.

Claims (1)

A liquid ring machine comprising a body with a cylindrical inner bore, end caps with suction and discharge windows, an impeller eccentrically mounted in the bore with a hub and vanes, and a thin-walled sleeve with longitudinal grooves on the inner surface that is concentrically mounted in the bore with the possibility of rotation and differs the fact that the rear wall in the direction of rotation of each groove is normal to the surface of the sleeve, and the front wall is mated to the rear at its base with images acute angle and is made flat or curved, and the eccentricity ε is determined from the following relationship:

where ε is the relative eccentricity, b / p; e - absolute eccentricity, m; ψ is the blocking factor of the volume of the impeller, b / r; and - the minimum value of the immersion of the blades of the impeller in the liquid ring (at the place of greatest removal of the impeller from the inner bore of the housing), m; ν = r ₁ / r ₂ , b / p; r ₁ = radius of the impeller hub, m; r ₂ = outer radius of the impeller, m; δ = Δ / r ₂ , b / p; Δ is the minimum clearance between the blades of the impeller and the inner bore of the casing (the minimum height of the bladeless space), m; ζ = b / b ₀ , b / p; b - width of the bezoplatochny space, m; b ₀ - the length of the rotor without taking into account the thickness of the stiffeners, m; k ₁ - empirical coefficient taking into account the departure of the inner surface of the liquid ring from the hub of the impeller in cross section with a minimum height of the bladeless space, b / r; k ₁₁ is an empirical coefficient characterizing the ratio of the average circumferential velocity of the fluid flow in the bladeless space at the place of least distance of the impeller from the inner bore of the casing to the peripheral speed of the ends of the blades of the impeller, b / r; k ₂₂ is an empirical coefficient characterizing the ratio of the average peripheral velocity of the fluid flow in the bladeless space at the place of greatest distance of the impeller from the inner bore of the casing to the peripheral speed of the ends of the blades of the impeller, b / r. K _W is an empirical coefficient that takes into account, all other things being equal, an increase in the average liquid flow rate in a space without a gap when a thin-walled sleeve is introduced into a cylindrical internal groove, b / r.