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Title:
CENTRIFUGAL PUMP WITH TWO CANTILEVERED IMPELLERS AND WITH MOTOR COOLED BY TWO FANS ARRANGED IN SERIES
Document Type and Number:
WIPO Patent Application WO/2016/128802
Kind Code:
A1
Abstract:
Two centrifugal pumps used in parallel and driven by a single electrical motor. The impellers of the pumps are placed at both ends of a shaft, with the motor in between. The motor is cooled by two fans fluidically arranged in series, driven by the pump shaft, and placed on both axial sides of the motor.

Inventors:
SULUR SUBRAMANIAM VANAGAMUDI (IN)
MURUGAN KATHIRVEL (IN)
SULUR PONMUDI VIGNESWARAN (IN)
LAKSHMI NARASIMHAN CHANDRASEKAR (IN)
KOVI VIMALATHITHAN CHOLAN (IN)
SRINIVASAN MADHAVAN (IN)
Application Number:
PCT/IB2015/052803
Publication Date:
August 18, 2016
Filing Date:
April 17, 2015
Export Citation:
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Assignee:
SULUR SUBRAMANIAM VANAGAMUDI (IN)
MURUGAN KATHIRVEL (IN)
SULUR PONMUDI VIGNESWARAN (IN)
LAKSHMI NARASIMHAN CHANDRASEKAR (IN)
KOVI VIMALATHITHAN CHOLAN (IN)
SRINIVASAN MADHAVAN (IN)
International Classes:
F04D13/06; F04D13/14; F04D17/16; F04D29/58; H02K9/06
Domestic Patent References:
WO2011132106A12011-10-27
WO1996019672A11996-06-27
Foreign References:
US20110175468A12011-07-21
IN383MU2010A2010-04-22
Attorney, Agent or Firm:
TASE, Vijay et al. (3rd floor Arena House, Plot no 103, Road no 12,,Opp Saffron Spice Hotel., MID, Andheri Mumbai 7, IN)
Download PDF:
Claims:
Claims

1. A centrifugal pump characterized in that said pump comprises a single rotor motor, two inlet ports and two outlet ports and wherein two fans are provided, namely a suction fan and an exhaust fan.

2. A centrifugal pump as claimed in claim 1 wherein said rotor motor is further provided with a shaft, and wherein ends of said shaft emerge out of said rotor motor on either side of said rotor motor, and further provided are

- two impellers, namely a first impeller and a second impeller, provided inside respective impeller housings, namely a first impeller housing and a second impeller housing; said respective housings carrying said respective impellers are mounted on respective ends of said shaft,

- two suction ports, namely a first suction port and a second suction port, provided on the impeller housing corresponding to said two impellers, such that fluid to be pumped is sucked in through respective suction ports and enters the respective impeller housings through respective suction mouths of said impellers,

- two delivery ports, namely a first delivery port and a second delivery port, provided corresponding to said two impeller housings, wherein upon operation of said pump, fluid sucked through suction ports enters said respective impeller housings through said suction mouths of said impellers and exits from said respective delivery ports.

3. A centrifugal pump as claimed in claims 1 and 2, wherein said motor body is provided with slots which run parallel to the axis of said shaft.

4. A centrifugal pump as claimed in claim 3, wherein said external air suction slots are placed on the lower side of the motor body.

5. A centrifugal pump as claimed in claims 1-4, wherein said motor body is provided with an end cover near the exhaust fan end of said motor body, wherein said end cover further comprises hot air expulsion holes.

6. A centrifugal pump as claimed in claims 1-5, wherein any one or both of said impeller housings are either volute type or of circular type.

7. A centrifugal pump as claimed in claims 1-6, wherein shaft mounting ports of said first and said second impellers are provided on opposite faces in respect of the direction of rotation of each impeller.

8. A centrifugal pump as claimed in claims 1 to 7, wherein the curvatures of the vanes of said first and said second impellers are configured in a manner that the fluid that enters the respective said impeller housings through respective suction mouths is released out of delivery ports.

9. A centrifugal pump as claimed in claims 1 to 8, wherein the air space between the stator winding and said motor body is at least 4mm.

10. A centrifugal pump as claimed in claims 1 to 9, wherein the space between the rotor and the stator is at least 0.6mm.

11. A centrifugal pump as claimed in claims 1-10, characterized in that said first impeller and said second impeller may be selected from any of radial-flow, axial-flow, or mixed-flow types.

12. A centrifugal pump as claimed in claims 1-11, characterized in that said first impeller housing and said second impeller housing may be any of the volute or circular type.

13. A centrifugal pump as claimed in claims 1-12, wherein the two said impellers are of the same type as each other.

14. A centrifugal pump as claimed in claims 1-13, wherein the two said impeller housings are of the same type as each other.

15. A centrifugal pump as claimed in claims 1 to 14, wherein said exhaust fan is larger than said suction fan.

16. A centrifugal pump as claimed in claims 1 to 15, wherein water suction ports and shaft mounting ports of said first and said second impellers are provided on opposite faces in respect of the direction of rotation of each said impeller.

Description:
CENTRIFUGAL PUMP WITH TWO CANTILEVERED IMPELLERS AND WITH MOTOR COOLED BY TWO FANS ARRANGED IN SERIES

Field of invention:

The present invention is related to fluid pumps. In particular the invention is related to centrifugal pumps used for pumping water or liquids of similar viscosity.

Background of the invention:

A conventional centrifugal pump works with an electrical power driven motor connected to the pump on its driving end. The non-driving end of a conventional pump typically has a cooling fan which is used for continuous cooling of the motor to avoid overheating of the motor in continuous application.

The driving end of the motor has an extended shaft which is connected to a impeller housing (also termed as pump housing) which houses an impeller which is either of a closed or an open type. In the monoblock type arrangement, the impeller housing is an integral part of the motor whereas in the non-monoblock arrangement, the impeller housing is separate and connected to the motor shaft by means of a coupling.

A monoblock type is generally meant for light duty application whereas for heavy and continuous duty, the non monoblock type is preferred. A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure and flow rate of a fluid. Centrifugal pumps are the most common type of pumps used to move liquids through a piping system. The fluid enters the pump impeller along or near the rotating axis and is accelerated by the impeller— flowing either radially outward or axially into a diffuser/volute chamber— from where it exits into the downstream piping system. Centrifugal pumps are typically used for large discharge through smaller heads at the upstream ends.

Indian patent application no. 383/MUM/2010 described a centrifugal pump. One of the drawbacks of existing pumps such as these is that its motor was cooled externally with a single fan provided and the fresh air was made to pass through the fins of the motor. Also the air space or clearance (2E) between the stator winding (8) and motor body (2B) is not large enough to provide free circulation of air. On the other hand the air gap between the rotor and the stator winding (8) in the existing pumps is such that the current drawn by the motor is not optimal.

Losses of a typical centrifugal pump are internal and external type. Several types of internal losses are known including the hydraulic losses or blade losses by friction, leakage losses, friction losses ate the external walls of wheels. The external losses include sliding surface losses, air friction losses at the clutches, and energy consumption of directly propelled auxiliary machines. While it is known that several attempts have been made and continue to be made to minimise these losses, the percentage improvement by minimising these losses is small. There is therefore a need to provide an improved pump that will improve the output more than that obtained by improvement in the above mentioned aspects.

Any continuously operating pumps are expensive to run and maintain. There's therefore a need to provide improved pumps that will be more economic to provide and maintain.

Objects of the invention:

Accordingly, one of the objects of the present invention is to provide a centrifugal pump that is more economic to provide, operate, and maintain.

A further objective of the present invention is to provide a centrifugal pump that uses fewer resources per unit volume of the pumped fluid than the conventional pumps.

Summary of invention:

The present invention discloses an improved centrifugal pump that provides nearly double the output measured in terms of the volume of liquid pumped per unit time than a conventional pump of the same HP rating for almost the same power consumption. The improved pump operates on a single motor and has two suction mouths and two delivery ports provided on the impeller housing. It also has two cooling fans, a reduced air gap between the rotor and stator windings, and an increased clearance between the stator winding and the stator body. The improved pump sucks up the water to be pumped through the two suction mouths and is pumped out via the two outlet ports after passing through a novel arrangement of motor with a dual end shaft, impellers and impeller housings, cooling fans, bearings.

List of figures:

Figure 1 - A view of the conventional pump

Figure 1 A - Typical operation of a centrifugal pump

Figure 2 - A view of the operational pump of the present invention

Figure 2 A - An exploded view of the invention

Figure 2B - The shaft of the present invention

Figure 2C - The shaft of the present invention showing the suction and exhaust fans

Figure 2D - Stator, and the motor body with slots

Figure 3- Motor end cover

Figure 4 - Motor with suction fan fitted to it

Figure 5 - Impeller housings of the present invention placed side by side

Figure 6 - Impellers of the present invention in a side view

Figure 7 - Impellers of the present invention in front view

Figure 8 - Different types of impellers List of parts:

Conventional pump - 1, Impeller back plate - 4C

Pump of the present invention - 1 A Impeller vanes - 4E

Motor - 2, Shaft 2A, motor body 2B, Impeller hub - 4F

slots 2C, holes 2D, air space between Impeller housing (or pump housing) stator winding and motor body 2E, - 5A, 5B

space between rotor and the stator 2F Impeller housing side cover - 5C1,

End cover - 2G 5C2

First suction port - 3 A Bearings - 6 A, 6B

Second suction port - 3B Suction fan, 7A, Exhaust fan 7B

Suction mouth - 3C, 3D Coil (or stator winding) - 8

First impeller - 4A Delivery ports - 9A and 9B

Second impeller - 4B Suction flanges - 10A and 10B

Impeller Face plate 4D

Description of invention:

The present invention comprises a modified centrifugal pump (1A). As shown in Figure 1 and 1A, the conventional centrifugal pumps (1) have a single motor, single suction port and a single delivery port. A central shaft emerging from a rotor (the prime mover) drives the impeller that is enclosed in a housing. There is a cooling fan or other suitable mechanisms to cool the moving parts which need to be cooled as they heat up during the operation. A typical conventional pump (1) has a single shaft that ends in the rotor motor. The other end of the shaft is connected to an impeller that rotates to create suction which draws water which when passed over an impeller is sent through the outlet or delivery port under pressure and at a velocity. The shaft also drives the cooling fan.

The present invention comprises a modified centrifugal pump (1A) comprising a single motor (2) a single shaft (2A), and a first impeller (4A) and a second impeller (4B) which are respectively housed in a first and a second impeller housing (5A, 5B). As a unique feature of the invention, there are two fans provided, a suction fan (7 A) and an exhaust fan (7B), which together carry out the function of cooling the motor. All other parts that are necessary for working of a typical centrifugal pump are provided in a modified form as appropriate. This will be apparent from the forthcoming description.

As seen from Figure 2, the pump of the present invention has two suction ports (termed as a first suction port (3 A) and a second suction port (3B)) and two delivery ports (termed as first delivery port (9 A) and a second delivery port (9B)), and a single motor (2). The water taken in via two suction ports (3A, 3B) enters the volute or casing through the respective suction mouth (3C, 3D) of the respective impellers (4 A, 4B). The impellers (4A, 4B) which rotate with the help of the energy provided by an energy source such as an electric motor, throw out the water through the two delivery ports (9 A, 9B) that are provided on the impeller housings (5 A, 5B). In the process, the water has gained sufficient head to reach a certain height.

It can be seen from Figure 2A that the pump of the present invention comprises what can be termed as 'two halves' which are preferably bilaterally symmetrical in the way which its several parts are arranged. Figure 2A shows an exploded view of the present invention and the direction of rotation of the vanes (4E) and Figure 2B shows the modified shaft of the present invention. The shaft (2A) has been modified such that it is placed securely inside the rotor motor (2) and either end of the shaft (2A) is modified such that impellers (4A, 4B) may be mounted on the ends in a manner known to a person skilled in the art. It is clear from this figure that necessary parts required for making of a functional centrifugal pump, such as, but not limited to, impellers, housing, bearings, are provided at each end of the shaft to facilitate this.

As seen from Figures 2D and 2F, one novel aspect of the present invention is that a suction and an exhaust fan (7A, 7B) is provided. Also, the motor body (2B) has been provided with suction slots (2C), which run in parallel to the axis of the shaft (2A), on the bottom side near the suction end, in order to facilitate efficient suction cool air from environment.

Figure 2A shows the modified motor (2B) used in the present invention. It can be seen that it comprises a single rotor motor (2) but it has been modified such that the shaft (2 A) extends out on either side of the motor (2A). One of the inventive features of the present invention is that, unlike the conventional pumps, impellers (4A, 4B) are provided at each end of the shaft (2A). This allows water to be sucked in on each end of the shaft (2A). Another feature of the present invention is that the impellers (4A, 4B) are modified such that they rotate in the same direction as each other. In other words, the impellers (4A, 4B) of the present invention are designed and configured such that when viewed from any one side along the axis, both impellers rotate in the same direction. Specifically, this means that the water suction ports (3 A, 3B) and shaft mounting ports of the impeller for right and left side impellers are provided on opposite faces in respect of the direction of rotation of each impeller (see figures 5 and 6). In other words, if one impeller is viewed as a 'right hand' impeller in terms of the direction of its rotation and that of the water flowing out, the other impeller would be termed as a 'left hand' impeller.

Figure 5shows a view of an impeller housing (5 A) and a delivery port (9 A). As can be seen from Figure 5, the relative arrangement of the impeller housings (5A, 5B, placed side by side for illustration purpose), the delivery ports (9 A, 9B), and the impeller face plates (4D) mirror each other when placed side by side. This is also evident from Figure 6, which show the modified impellers (4A, 4B) of the present invention, placed side by side for the purpose of illustration, and which are placed on either side of the shaft (2A) such that the impeller hubs (4F) are placed on the that surface of the respective impellers (the face plate, see Figure 7) which allow water to be thrown out of the delivery ports (9 A, 9B) in the same direction when the impellers (4A, 4B) are placed in their respective places on either end of the shaft (2A).

Figure 8 shows some of the several impeller designs currently used for centrifugal pumps. The impellers used in the invention may be modified from any of these or other similar impellers, modifications being those described in this document. In particular, the hubs, the suction mouths, vane directions of the impellers of the present invention are so oriented and located as to facilitate entry and exit of water from both ends of the shaft. The impellers suitable for the invention may be of radial-flow, axial-flow, or mixed-flow type. They may be closed or open, or semi-open or vortex type. Some of the conventional vanes are shown in Figure 8, which can be modified for use in the present invention in accordance with the guidelines provided earlier.

Impeller housings or casings suitable for the invention are typically of two types, namely volute and circular. Either type of casing may be used in the pump of the present invention. The impellers (4A, 4B) are fitted inside the casings. It is well known that a volute casing builds a higher head but have low capacity whereas the circular casings are used for low head and high capacity. The casings can be designed either as solid casings or split casings. Solid casing implies a design in which the entire casing including the discharge nozzle is all contained in one casting or fabricated piece. A split casing implies two or more parts are fastened together.

A further feature of the improved pump is that it has two fans (7A and 7B) for the purpose of cooling, however they function in a different manner than the conventional arrangement of single fan. In the present invention, one fan is typically smaller than the other one. In the conventional designs, the motor is cooled externally with a single fan provided on side and the fresh air is made to pass through the fins of the motor. In the present and improved design, an air suction fan (7A) has been provided on the one end of the rotor shaft which sucks fresh air through the slots (2C) provided at bottom of the motor body and pushes the sucked air above the stator winding (8). Another smaller fan— the exhaust fan (7B), which is fitted on the other end of rotor shaft— receives the air and throws the circulated hot air out of the holes (2D) provided at the relevant end cover (2G) of the motor. The end cover at the other end of the motor body (2B) is not provided with holes.

Yet another feature of the improved pump is that the clearance (2E) between the stator winding (8) and the motor body (2B) has been increased (to 4mm) to accommodate increased air flow which ensures improved cooling. As a result of this, the winding temperature is always maintained within acceptable limits (approximately 130 °C).

In order to cope with the added load of higher throughput of liquid, the winding (8) is constructed using two runs of 21 gauge copper wire or its equivalent. It has been observed that this leads to increased motor efficiency with the same consumption of the current.

In the 5hp tested pump manufactured according to the invention, an F-class insulation has been used in order to ensure optimum life of the motor in continuous and increased load conditions. The F-class insulation is used to protect the winding (8) from excessive heat. However, any other suitable insulation may be used.

Another improved feature of the pump of the invention is the optimisation of the space (2F) between the rotor and the stator winding (8). The amount of current drawn by the motor depends on this parameter. This space is maintained at 0.6 mm in the improved pump of the invention.

The inventors have found that the length of the stator is also an important parameter in a pump's efficiency. By increasing the motor length by 25%, the winding area and the rotor length have been increased to accommodate two cooling fans inside of the motor, thus improving the cooling efficiency and ensuring the optimum life of the motor winding (8). The life of winding depends based on the input parameters like voltage, frequency, load of the motor etc. If these parameters are maintained unchanged, then the winding can last even for decades. For the present invention, a life of a minimum of 5 years can be expected.

Pumps of virtually any capacity may be built using the disclosure made herein. As in the case of conventional pumps, the capacity of the dual action pump disclosed herein depends on a number of factors such as the character of the processed liquid— its density and viscosity, pump size and its inlet and outlet sections, the impeller size and the rotational speed of the impeller, size and shape of cavities between the vanes, and the pump suction and discharge temperature and pressure conditions. The design of impellers for the pump of the present invention follows the established methods of the impeller design.

The benefits of the invention are best understood through the following example. Two pumps were tested, a Crompton Greaves make centrifugal monoset MIK 52, 50 X 40 pump of 5hp rating and an Apex dual pump of 5hp rating that was constructed using same motor. The output (litres/hr) and power consumption (watts/hr) was recorded along with the head to which the water rises. An F-class insulation was used in order to ensure optimum life of the motor in continuous and increased load conditions. Table 1: Specification of the motor used in the experiments.

TECHNICAL COMPARISON BETWEEN A STANDARD PUMP AND APEX DUAL PUMP

Note: 1 day = 8 hours, 1 month = 30 days, 1 year = 365 days

The data provided in table 1 is to be used by the way of examples and not taken as limit on the parameters that influence the invention. It is evident from the above data that a 5.0 hp Apex dual pump of the present invention offers the following advantages over a standard pump of similar rating: delivers 10008 L/hr of additional output

delivers 37,296 litres per hour as compared with 27,288 litres of a standard pump

- The pump of the present invention uses a current of 8.8 Amps versus the

7.5 Amp used by a standard pump, however, the pump of the invention delivers an energy saving of 1.8 KW in an hour's operation. This leads to an annual saving of 5196 KW (Rs. 28,000 at the current energy costs) per pump assuming an 8 hours/day operation for 365 days of the year.

- In terms of the material costs, the pump of the invention pump is more economical to manufacture as it uses a single rotor and a motor.

Although the above example relates to fluids of viscosity similar to water, the pump of the present invention is useful with other fluids The pump of the present invention is useful for pumping all types of fluids including oils, mud slurries, and wet concrete.

It is evident that the present invention has the following embodiments. A centrifugal pump characterized in that said pump comprises a single rotor motor, two inlet ports and two outlet ports and wherein two fans are provided, namely a suction fan and an exhaust fan.

A centrifugal pump as described in embodiment 1 wherein said rotor motor is further provided with a shaft, and wherein ends of said shaft emerge out of said motor on either side of said motor, and further provided are

- two impellers, namely a first impeller and a second impeller, provided inside respective impeller housings, namely a first impeller housing and a second impeller housing; said respective housings carrying said respective impellers are mounted on respective ends of said shaft,

- two suction ports, namely a first suction port and a second suction port, provided on the impeller housing corresponding to said two impellers, such that fluid to be pumped is sucked in through respective suction ports and enters the respective impeller housings through respective suction mouths of said impellers,

- two delivery ports, namely a first delivery port and a second delivery port, provided corresponding to said two impeller housings, wherein upon operation of said pump, fluid sucked through suction ports enters said respective impeller housings through said suction mouths of said impellers and exits from said respective delivery ports. A centrifugal pump as described in embodiments 1 and 2, wherein the body of said rotor motor is provided with slots which run parallel to the axis of said shaft.

A centrifugal pump as described in embodiment 3, wherein said external air suction slots are placed on the lower side of the motor body.

A centrifugal pump as described in embodiments 1-4, wherein said motor body is provided with an end cover at near the exhaust fan end of said motor body, wherein said end cover further comprises hot air explusion holes.

A centrifugal pump as described in embodiments 1-5, wherein any one or both of said impeller housings are either volute type or of circular type. A centrifugal pump as described in embodiments 1-6, wherein shaft mounting ports of the impeller for right and left side impellers are provided on opposite faces in respect of the direction of rotation of each impeller.

A centrifugal pump as described in embodiments 1 to 7, wherein the curvatures of the vanes of said impellers are configured in a manner that the fluid that enters the impeller housings through respective suction mouths is released out of delivery ports.

A centrifugal pump as described in embodiments 1 to 8, wherein the air space between the stator winding and motor body is at least 4mm. 10. A centrifugal pump as described in embodiments 1 to 9, wherein the space between the rotor and the stator is at least 0.6mm.

11. A centrifugal pump as described in embodiments 1-10, characterized in that said first impeller and said second impeller may be selected from any of radial-flow, axial-flow, or mixed-flow types.

12. A centrifugal pump as described in embodiments 1-11, characterized in that said first impeller housing and second impeller housing may be any of the volute or circular type.

13. A centrifugal pump as described in embodiments 1-12, wherein the two impellers are of the same type as each other.

14. A centrifugal pump as described in embodiments 1-13, wherein the two impeller housings are of the same type as each other.

15. A centrifugal pump as described in embodiments 1-14, wherein said exhaust fan is larger than said suction fan.

16. A centrifugal pump as described in embodiments 1-15, wherein water suction ports and shaft mounting ports of said first and said second impellers are provided on opposite faces in respect of the direction of rotation of each said impeller.

While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.