Title:

Kind
Code:

A1

Abstract:

A multi-stage electric pump unit, of those that consist of a multi-stage centrifugal pump with an electric motor coupled directly to the pump, where each stage consists of a pump, an impeller and a diffuser, which each have channels with vaned and vaneless zones. These zones are delimited by a shroud-surface and a hub-surface, where the b angle is the angle of the tangent at each point, characterized because, given that the Y-axis of the electric pump is the radial co-ordinate and X is the axial co-ordinate, for flow rates, Q, between 2500 and 8000 liters/minute, the points of the impeller and diffuser surface comply with the sixth degree polynomial equation, Y=f(x)=Ax6+Bx5 +Cx4+Dx3+Ex2+Fx+G, and changing the constants of the equation for each part-zone of the diffuser and impeller.

Applicable to hydraulic machines.

Inventors:

Duran, Silvia (Beasain, ES)

Rodriguez, Maria Elena (Beasain, ES)

Rodriguez, Maria Elena (Beasain, ES)

Application Number:

10/691181

Publication Date:

09/16/2004

Filing Date:

10/22/2003

Export Citation:

Assignee:

DURAN SILVIA

RODRIGUEZ MARIA ELENA

RODRIGUEZ MARIA ELENA

Primary Class:

International Classes:

View Patent Images:

Related US Applications:

20070041845 | Motor-driven metering pump | February, 2007 | Freudenberger |

20070297921 | CONDUIT SEAT FOR AN ATOMIZING DEVICE | December, 2007 | Huang |

20060204384 | Water cannon | September, 2006 | Cornell et al. |

20100008798 | BLOWER NOISE MUFFLER APPARATUS AND SYSTEM | January, 2010 | Clawson et al. |

20060222515 | Drainage system for compressor separators | October, 2006 | Delmotte et al. |

20050196298 | Gas compressor dual drive mechanism | September, 2005 | Manning |

20080304985 | TURBO-MOLECULAR PUMP | December, 2008 | Onishi |

20090169402 | Membrane Pump | July, 2009 | Stenberg |

20080213101 | Shower Wast Pump Control | September, 2008 | Stimpson et al. |

20090087321 | TWO-STAGE COMPRESSION ROTARY COMPRESSOR | April, 2009 | Morozumi et al. |

20080069706 | Centrifugal pump device for a heat-dissipating system | March, 2008 | Huang |

Primary Examiner:

VERDIER, CHRISTOPHER M

Attorney, Agent or Firm:

LUCAS & MERCANTI, LLP (NEW YORK, NY, US)

Claims:

1. A multi-stage electric pump unit, of those that consist of a multi-stage centrifugal pump with an electric motor coupled directly to the pump, where each stage consists of a pump, an impeller and a diffuser, which each have channels with vaned and vaneless zones. These zones are delimited by a shroud-surface and a hub-surface, where the β angle is the angle of the tangent at each point, characterised because, given that the Y-axis of the electric pump is the radial co-ordinate and X is the axial co-ordinate, for flow rates, Q, between 2500 and 8000 litres/minute, the points of the impeller and diffuser surface comply with the sixth degree polynomial equation, Y=f(x)=Ax^{6} +Bx^{5} +Cx^{4} +Dx^{3} +Ex^{2} +Fx +G, where on the diffuser: a) on the hub, the vaneless zone; A=B=C=D=E=0; F=0.6605; G=20.45; b) on the shroud, the vaneless zone; A=B=C=D=E=0; F=0.7225; G=55.648 c) on the hub, the vaned zone; A=−9E-09; B=7 E-06; C=−0.0019; D=0.3064; E=−26.923; F=1256.3; G=−24283 d) on the shroud, the vaned zone; A=1E-10; B=−9E-08; C=2E-05; D=−0.0033; E=0.2349; F=−7.616; G=174.28 e) on the hub, the vaneless zone; A=0; B=0; C=−1E-05; D=0.0073; E=−1.7542; F=186.27; G=−7311.6; f) on the shroud, the vaneless zone; A=0; B=0; C=0; D=0.0053; E=−2.6745; F=446.37; −G=24717; g) on the hub, β; A=0; B=0; C=1E-06; D=−0.0002; E=0.0203; F=−1.0819; G=156.82; h) on the shroud, β; A=0; B=0; C=3E-07; D=−1E-04; E=0.0101; F=−0.7587; G=175:

2. A multi-stage electric pump unit, in accordance with the preceding claim, characterised because on the impeller: a1) on the hub, the vaneless zone; A=0; B=0; C=0; D=6 E-05; E=0.0014; F=−0.0146; G=27.511; b1) on the shroud, the vaneless zone; A=0; B=0; C=0; D=0; E=0; F=0; G=64.5; c1) on the hub, the vaned zone; A=0; B=0; C=5 E-06; D=−0.0014; E=0.1535; F=−6.3821; G=121.24; d1) on the shroud, the vaned zone; A=−4E-08; B=8E-06; C=−0.0006; D=0.0247; E=−04771; F=4.3023; G=50.015; e1) on the hub, β; A=0; B=3E-09; C=−9E-07; D=0 .0001 ; E=−0.0042; F=−0.0915; G=34.402; f1) on the shroud, β; A=0; B=1E-09; C=−5E-07; D=6 E−05; E=−0.0044; F=0.1822; G=22.2.

3. A multi-stage electric pump unit, in accordance with the first claim, characterised because on the impeller: a2) on the hub, the vaneless zone; A=0; B=0; C=0; D=5 E-05; E=0.0013; F=−0.0139; G=27.511 b2) on the shroud, the vaneless zone; A=0; B=0; C=0; D=0; E=0; F=0; G=64.5 c2) on the hub, the vaned zone; A=0; B=0; C=5E-06; D=−0.0012; E=0.1205; F=−4.7599; G=93.614 d2) on the shroud, the vaned zone; A=0; B=7E−07; C=−0.0001; D=0.0058; E=−0.113; F=0.8709; G=62.273 e2) on the hub, β; A=0; B=0; C=9E-08; D=−3E-05; E=0.0002; F=0.0246; G=41.062 f2) on the shroud, β; A=0; B=0; C=−6E-07; D=0.0001;E=−0.0126; F=0.5887; G=23.694.

2. A multi-stage electric pump unit, in accordance with the preceding claim, characterised because on the impeller: a1) on the hub, the vaneless zone; A=0; B=0; C=0; D=

3. A multi-stage electric pump unit, in accordance with the first claim, characterised because on the impeller: a2) on the hub, the vaneless zone; A=0; B=0; C=0; D=

Description:

[0001] Multi-stage electric pump units are hydraulic machines that consist of multi-stage centrifugal pumps, the electric motor of which is directly coupled to the pump part.

[0002] The main hydraulic elements are the impeller and the diffuser. The impeller is the key element in every pump (it converts the rotation speed into pressure), although the body, or diffuser, is highly important, given that it redirects the fluid from the impeller outlet to the inlet of the next impeller, thereby recovering the static pressure. When the desired head is very high, various impellers are positioned in a series, thus the designation, clean water multi-stage units.

[0003] What is demanded of an electric pump is that it provide maximum efficiency, and this will be achieved if the impeller and diffuser provide maximum efficiency.

[0004] The efficiency rating of modem electric pumps is usually between 75% and 85% of the total work input into the electric pump.

[0005] The objective of this invention is to exceed that efficiency.

[0006] The inventor has considered the following to be fundamental: that the pump reach stability, that cavitation and turbulence be prevented, that the curvature and non-curvature zones of the impeller and diffuser vanes be such that the flow is guided perfectly and that this flow correctly follow the direction of the vanes.

[0007] The applicant has developed a multi-stage electric pump unit, of those that consist of a multi-stage centrifugal pump and an electric motor directly coupled to the pump, where each stage of the pump consists of an impeller and a diffuser that each have channels with vaned and vaneless zones. These zones are delimited between a shroud-surface and a hub-surface, where the β angle is the angle of the tangent at each point, which is characteristic because, given that the Y-axis of the electric pump is the radial co-ordinate and X is the axial co-ordinate, for flow rates Q between 2500 and 8000 1/min., the points of the surface of the impeller and of the diffuser comply with the following sixth-degree polynomial equation: Y=f(x)=Ax^{6}^{5}^{4}^{3}^{2}

[0008] a) on the hub, the vaneless zone; A=B=C=D=E=0; F=0.6605; G=20.45;

[0009] b) on the shroud, the vaneless zone; A=B=C=D=E=0; F=0.7225; G=55.648

[0010] c) on the hub, the vaned zone; A=−9E-09; B=7E-06; C=−0.0019; D=0.3064; E=−26.923; F=1256.3; G=−24283

[0011] d) on the shroud, the vaned zone; A=1E-10; B=−9E-08; C=2E-05; D=−0.0033; E=0.2349; F=−7.616; G=174.28

[0012] e) on the hub, the vaneless zone; A=0; B=0; C=−1E-05; D=0.0073; E=−1.7542; F=186.27; G=−7311.6;

[0013] f) on the shroud, the vaneless zone; A=0; B=0; C=0; D=0.0053; E=−2.6745; F=446.37; −G=24717;

[0014] g) on the hub, β; A=0; B=0; C=1E-06; D=−0.0002; E=0.0203; F=−1.0819; G=156.82;

[0015] h) on the shroud, β; A=0; B=0; C=3E-07; D=−1E−E-04; E-=0.0101; F=−0.7587; G=175.

[0016] For different flow rates, the constants of the polynomial are modified for the impeller.

[0017] With these geometric characteristics of the electric pump components, the efficiencies obtained with the electric pumps are substantially higher than currently known efficiencies, thereby reaching increases of up to 14%, which is surprising in these kinds of machines.

[0018] In conventional technology, both the impeller and the diffuser are made of a casting, thereby preventing the precision of the geometric shapes/curves, which have characteristics that are so difficult and special to both bodies.

[0019] In the invention, and once the aforementioned polynomial equation is developed, a machining centre can be programmed precisely, thereby achieving the fewest deviations by the actual geometric shapes with respect to the theoretical shapes, and as a result, very small deviations by the actual efficiencies with respect to the theoretical efficiencies.

[0020] In order to understand the object of this invention better, explanatory figures have been attached.

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] The nomenclature used is the following:

[0029] A ∈ [2.3, 5] This means that A belongs to a closed interval (the end values of the interval are included), which end values are 2.3 and 5. In other words, A can take any value encompassed between 2.3 and 5, both inclusive.

[0030] Q means the flow rate, the units of which are in 1/min.

[0031] The plane (Z, R) is the plane defined in

[0032] The shroud and hub are the curves shown in the figure, for both the impeller and the body or diffuser. All of these curves show axisymmetry (axial symmetry).

[0033] β angle (°) (

[0034] The graph (p, M %) provides values of P for each value of M % (percentage of the distance travelled over the vane, hereby understanding that 0% is the start of the vane and 100% is the end of the same).

[0035] Impeller and/or diffuser channel.

[0036] This corresponds to the volume of fluid enclosed between two consecutive vanes, the shroud and the hub of the impeller and/or diffuser.

[0037] “Double curvature”

[0038] This is the magnitude of the tangential co-ordinate from the edge of the vane entry until the edge of the vane exit.

[0039] Given a distribution of beta, the “double curvature” values are set at the entry (at both the shroud and the hub) for the complete definition of the impeller channel (likewise for the diffuser).

[0040] The constituent elements of the impeller and diffuser are the following:

[0041] (T) Shroud: This is the outer-most flow surface of a pump flow path.

[0042] Vane: A surface (with a certain distribution of thickness) with an aerodynamic shape that extends from the hub of an impeller or stator and is responsible for the course of the flow, and as regards rotating vanes, for transferring the force to the flow.

[0043] (C) Hub: This is the innermost flow surface of a pump flow path.

[0044] The walls of the impeller and/or diffuser channel that are not vanes are the shroud (T) and the hub (C).

[0045] Once the flow enters the impeller channel, the limit layers begin to develop for the entire vane on the shroud and hub surfaces. The heart of the flow, at least initially, tends to follow the vane channel reasonably well, thereby assuming a uniform input flow. If any distortion occurs at the input flow, then the heart of the flow will be characterised by the presence of vortices from the start, which must be avoided.

[0046] Vortices (see

[0047] The points of contact with the walls of the channel (v=0) slow down the fluid particles that go close to the walls. A layer called a limit layer is thus formed, within which the speeds of the fluid particles are less than in the undisturbed zone.

_{LIMIT LAYER}_{ALL OTHER PARTICLES}

[0048] Where U is the total speed of the particles.

[0049] δ is defined as the height of the limit layer (CP) (see

[0050] To the extent that the flow advances in the impeller channel, both the heart of the flow (CF) and the surface of the limit layer experience complex force-fields, and they develop more complicated flow shapes. The limit layers initially follow the free-flow direction. However, to the extent that the fluid advances in the impeller channel, both the limit layers and the heart of the flow are influenced by a force field through the channel. It is for this reason that a secondary flow develops around the heart of the flow, which is near the suction surface of the shroud, and a flow with an elevated moment develops in the pressure area of the hub.

[0051] In general, a secondary flow is considered a flow in which viscous effects are predominant. Conversely, a primary flow is considered a flow in which the kinetic effects are predominant.

[0052] As a general characteristic, it can be affirmed that both the primary flow and the secondary flow comply with conservation equations (equations that, together with the contour conditions, govern the behaviour of the fluid flow as it transfers through the duct, whether rotating or fixed).

[0053] The basic fluid dynamics characteristics of a pump stage can be introduced by examining in detail each one of the components and their dominant velocity triangles, using the following principles:

[0054] 1) The first principle is the mass conservation principle.

[0055] 2) Newton's equation of movement in a system of angular co-ordinates.

[0056] 3) Euler's equation of turbomachinery, which simply states that the increase of enthalpy is equal to the change in angular momentum.

[0057] With these principles, the velocity triangles at various positions of the flow field can be examined.

[0058] The first important point is the inlet (

[0059] It is hereby recognised that there is a large variety of possibilities for inlet flow states for a same flow that is pulled towards the eye of the impeller with a meridian speed of C_{m}

[0060] The flow is found with the pump wheel moving at a perimeter speed of U=2·π·r·N. The velocity triangle is written in accordance with the following basic principle:

[0061] For an inlet flow to the impeller where C_{θ}

[0062] If β is equal to the vane angle, then the flow correctly follows the vane direction. However, under different operational conditions, the angle can be greater or less than the vane angle, and as a result thereof, the flow will experience a certain level of incidence. The inlet flow state can also be substantially modified in the event that there is any pre-rotation (rotating water before it enters the wheel), either in the same rotation direction as or contrary to the motor shaft.

[0063] This ideal inlet to the impeller can be achieved with an appropriate intake design.

[0064] By varying both the mass flow and the flow area, the relative speed W_{1t }_{m }

[0065] The meridian speed component, C_{m}

[0066] For both radial and curved vanes, the resulting absolute flow angle (α) is very large: typically β=50° to 80° (radial reference) or α′=10° to 40° (tangential reference). It is most common for this angle to be α′=15° to 25° and a=65° to 75°. The velocity triangle at the output is important not only for determining the work level or pressure increase, but also for understanding the variation in pressure with changes in the mass flow.

[0067] Once the operating conditions are specified and the impeller efficiency level is known, then the flow can be calculated from the input to the output, in addition to being able to make a good estimate of the slip factor. The resulting flow field is characterised by having a considerable quantity of kinetic energy with a certain rotation at the output.

[0068] The efficiency, as previously described, relates the isoentropic work (isoentropic work: the least work that could be used to reached the desired head) to the real work. This is a strict definition of thermodynamics.

[0069] In order to be able to define the velocity triangles, it is necessary to know the efficiency value of the impeller, and obtaining this is not simple.

[0070] The next step to be considered is the discharge from a vaneless diffuser, or at any point within a vaneless diffuser.

[0071] It is possible to convert kinetic energy into an increase of the static pressure by changing the radius of the path described for the median flow, in accordance with the law of conservation of angular momentum.

[0072] Angular momentum is related to the angular momentum at the output of the impeller in accordance with the law of conservation of angular momentum. In fact, part of this angular momentum is destroyed to the extent that the flow transfers through a vaneless diffuser. Therefore, more precise calculations must be made in order to be able to estimate the level of this degradation. It can be said that approximately 5% to 15% can be lost due angular momentum.

[0073] The meridian component of the total speed (C_{m}

[0074] The variation of the area that the flow must follow in the diffuser is used as a second measure of the conversion of kinetic energy into an increase of the pressure energy.

[0075] As the connection point between different components, diffusers also play an important role in regulating the flow levels and in controlling the radial thrusts.

[0076] Vaneless diffusers (

[0077] The existence of a vaneless diffuser between the impeller and the diffuser body (vaned) helps to prevent coupling of the vibration modes between the vanes of the diffuser body and the vanes of the diffuser, thereby preventing the edge of the vane of the diffuser body at the input from becoming loaded and failing due to fatigue.

[0078] An impeller that is followed by a continuous diffuser body of vanes that begins immediately after the discharge from the impeller and extends to the start of the next stage can also be used.

[0079] Considering all of these conditioning factors, the applicant has been performing a considerable number of actual experiments and, computed using the Computational Fluid Dynamics (CFD) technique, has been determining point by point the optimum geometry at each point of the fluid path in a pump in order to achieve optimum efficiency.

[0080] With this geometry represented on co-ordinate axes where the Y-axis of the pump is the ordinate reference (Y≡R) and X≡Z is the radial co-ordinate on the Y-abscissas, and applying the mathematical technique to this geometry, he has developed a simple equation, but one that complies with the experimental results obtained and that has an error margin of ±3.5%.

[0081] This equation is the polynomial Y=Ax^{6 +Bx}^{5 +CX}^{4 +Dx}^{3 +Ex}^{2}

[0082]

[0083]

[0084] The flow rates, Q, that have been worked with are in a range from 2500 to 8000 litres/minute.

[0085] In the trials performed, the applicant considered that the essential element in the electric pump for reaching optimum efficiency was the body-diffuser, wherefore it remained unchanged, while it was advisable to modify the impeller as the range of the flow rate (Q) was modified. Therefore, flow rate values (Q_{1}_{2}

[0086] The equations are the following:

Y = f(x) = Ax^{6 }^{5 }^{4 }^{3 }^{2 } | ||||||||

Identification | A | B | C | D | E | F | G | Interval |

Q_{1} | 0 | 0 | 0 | 6E−05 | 0.0014 | −0.0146 | 27.511 | [1, 40.5] |

Q_{1} | 0 | 0 | 0 | 0 | 0 | 0 | 64.5 | [1, 9] |

Q_{1} | 0 | 0 | 5E−06 | −0.0014 | 0.1535 | −6.3821 | 121.24 | [40.5, 83] |

Q_{1} | −4E−08 | 8E−06 | −0.0006 | 0.0247 | −04771 | 4.3023 | 50.015 | [9, 54.09] |

Q_{1} | 0 | 3E−09 | −9E−07 | 0.0001 | −0.0042 | −0.0915 | 34.402 | [0, 100] |

Q_{1} | 0 | 1E−09 | −5E−07 | 6E−05 | −0.0044 | 0.1822 | 22.2 | [0, 100] |

Q_{1 }_{2} | 0 | 0 | 0 | 0 | 0 | 0.6605 | 20.45 | [83, 88] |

Q_{1 }_{2} | 0 | 0 | 0 | 0 | 0 | 0.7225 | 55.648 | [54.09, 60] |

Q_{1 }_{2} | −9E−09 | 7E−06 | −0.0019 | 0.3064 | −26.923 | 1256.3 | −24283 | [88, 154] |

Q_{1 }_{2} | 1E−10 | −9E−08 | 2E−05 | −0.0033 | 0.2349 | −7.616 | 174.28 | [60, 163.5] |

Q_{1 }_{2} | 0 | 0 | −1E−05 | 0.0073 | −1.7542 | 186.27 | −7311.6 | [154, 174] |

Q_{1 }_{2} | 0 | 0 | 0 | 0.0053 | −2.6745 | 446.37 | −24717 | [163.5, 174] |

Q_{1 }_{2} | 0 | 0 | 1E−06 | −0.0002 | 0.0203 | −1.0819 | 156.82 | [0, 100] |

Q_{1 }_{2} | 0 | 0 | 3E−07 | −1E−04 | 0.0101 | −0.7587 | 175 | [0, 100] |

Q_{2} | 0 | 0 | 0 | 5E−05 | 0.0013 | −0.0139 | 27.511 | [1, 41] |

Q_{2} | 0 | 0 | 0 | 0 | 0 | 0 | 64.5 | [1, 7] |

Q_{2} | 0 | 0 | 5E−06 | −0.0012 | 0.1205 | −4.7599 | 93.614 | [41, 83] |

Q_{2} | 0 | 7E−07 | −0.0001 | 0.0058 | −0.113 | 0.8709 | 62.273 | [7, 54.09] |

Q_{2} | 0 | 0 | 9E−08 | −3E−05 | 0.0002 | 0.0246 | 41.062 | [0, 100] |

Q_{2} | 0 | 0 | −6E−07 | 0.0001 | −0.0126 | 0.5887 | 23.694 | [0, 100] |

[0087] Where:

[0088] I: Impeller.

[0089] D: Body or diffuser.

[0090] A: Vaned zone.

[0091] NA: Vaneless zone.

[0092] T: Shroud.

[0093] C: Hub. β: Beta angle.

[0094] Many measurements were taken in laboratories on the known efficiencies of electric pumps and on the efficiencies with the prototypes developed in accordance with the geometry of the elements adapted to the stated polynomial equation.

[0095] As an example, thirteen results for different flow rates (Q) have been attached. In these examples, in all the new electric pumps, the same kind of body-diffuser has been used, and a first kind of impeller for flow rates (Q_{1}_{2}

Old hydraulic | New hydraulic | |

efficiency | efficiency | |

Q_{1} | ||

3250 | 69.64 | 75.164 |

3750 | 75.2 | 80.33 |

4250 | 78.2 | 86 |

4500 | 79.15 | 87.2 |

4800 | 80.3 | 88.37 |

5100 | 80.4 | 87.5 |

5400 | 79.9 | 85 |

5700 | 77.5 | 82.4 |

Q_{2} | ||

5000 | 75 | 85.43 |

5500 | 78 | 86.7 |

6000 | 79 | 86.2 |

6500 | 76.5 | 83.7 |

7000 | 72 | 79.366 |