FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
■■ *
A Multi-stage Centrifugal Pump with Hybrid Diffusion Technology.
APPLICANT(S):
Crompton Greaves Limited, CG House, 6th Floor, Dr. Annie Besant Road, Worli, Mumbai -400030, Maharashtra, India; an Indian Company.
INVENTOR (S):
Garje Pravin and Akole Anil of Crompton Greaves Limited, Pumps Division, C-19, MIDC, Ahmednagar-414 111, Maharashtra, India; both Indian Nationals.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
This invention relates to the field of mechanical engineering and fluid dynamics.
Particularly, this invention relates to the field of pumps, impellers, turbines, motors, and the like.
Specifically, this invention relates to a multi-stage centrifugal pump with hybrid diffusion technology.
BACKGROUND OF THE INVENTION:
A pump is a device that moves fluids by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid; Centrifugal, Positive displacement,
Pumps convert mechanical energy to fluid energy by its rotary or reciprocating action. Pumps operate via many energy sources, including manual operation, electricity, engines, solar or wind power, come in many sizes, from microscopic for use in medical applications to large industrial pumps.
Like most pumps, a centrifugal pump converts mechanical energy from a motor to energy of a moving fluid. A portion of the energy goes into kinetic energy of the fluid. Fluid enters axially through eye of the casing, is caught up in the impeller blades,.and is whirled tangentially and radially outward until it leaves through all circumferential parts of the impeller into the-diffuser part of the casing. The fluid gains both velocity and pressure while passing through the impeller. The diffuser or volute chamber of the casing decelerates the flow and further increases the pressure.
Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. Common uses include water, sewage, petroleum and petrochemical pumping. The reverse function of the centrifugal pump is a water turbine converting potential energy of water pressure into mechanical rotational energy.

Figures 1 and 2 illustrate various views of the centrifugal pump of the prior art. As can be seen, it is a 2-stage pump with both stages having volute for velocity diffusion. Velocity generated by a first impeller (14) in the first stage is diffused into pressure by a first volute (12). The pressurized water which is the output from the first volute is supplied by crossover arrangement to next stage suction. The next stage comprises a second impeller (18) and a second delivery volute (20). An inter-stage plate (16) separated the first impeller (14) from the second impeller (18), thereby separating the first stage from the second stage. Major losses take place in this crossover flow path (that is from the 1st stage exit to the 2nd stage inlet). Designing of this flow path from 1st stage exit to 2n stage entry is very challenging and even, if designed properly, it is very difficult to avoid losses. Also, there is space constraint to design this flow path. For proper designing of flow path for crossover, there is need for more space and overall pump size (length and width) increases, due to which weight of the pump also increases. Also, the suction volute and delivery volute are complex parts for manufacturing - as they have complicated internal features. Therefore, casting costs also increase. Furthermore, chances of casting rejection increases. Also, in this case, both impellers are arranged back to back due to which vane direction of both impellers is opposite; because of which two different impellers and patterns for two different impellers need to be made; which lead s to more initial investment.
Additionally, as suction as well as delivery casings are much complex in design, it is difficult for casting which leads to more casting rejection and more inaccuracy of casting which again leads to performance deterioration. Losses in crossover are very high due to which efficiency of pump is very less.
Therefore, there is a need for a centrifugal multi-stage pump with hybrid methodology / technique for velocity diffusion which obviates the deficits of the prior art.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a centrifugal multistage pump with hybrid (different in final stage in relation with rest of the stages) technique to diffuse velocity in different stages to optimize the performance of the pump.

Another object of the invention is to provide a multi-stage centrifugal pump which reduces complexities in design and casting.
Another object of the invention is to provide a multi-stage centrifugal pump which reduces complexities in suction volute casing.
Yet another object of the invention is to provide a multi-stage centrifugal pump in which losses in crossover flow from first stage to second stage is reduced.
Still another object of the invention is to provide a multi-stage centrifugal pump wherein multiple separate impeller designs are not required for corresponding multiplicity of stages.
Still another object of this invention is to use last stage diffusion through volute casing to reduce exit iosses which typicaiiy occurs after iast stage if diffuser casing is used when water or fluid is forced into delivery chamber.
An additional object of the invention is to provide a multi-stage centrifugal pump wherein design and casting challenges relating to pump design are overcome.
SUMMARY OF THE INVENTION;
According to this invention, there is provided a multi-stage centrifugal pump with hybrid diffusion technology, said pump comprising:
• at least a first stage for said multi-stage centrifugal pump comprising at least a suction annular casing, said first stage further comprising at least a first impeller;
• at least an end stage for said multi-stage centrifugal pump comprising at least an end impeller, said end stage further comprising at least a delivery volute casing adapted to deliver said fluid at the exit stage; and
• at least an intermediate plate with return channels, said intermediate plate adapted to separate stages in the multiplicity of stages of said multi-stage centrifugal pump, thereby providing at least an intermediate plate between any two adjacently located impellers in said multi-stage centrifugal.pump.'

Typically, said at least a first stage for said multi-stage centrifugal pump is a suction side stage.
Typically, said suction annular casing comprises at least a first plate with an inside annular rim of standard thickness.
Typically, said suction annular casing comprises diffusers which aid in diffusion on fluid during exit from said at least a first impeller.
Typically, said end stage for said multi-stage centrifugal pump comprises said delivery volute casing to diffuse velocity into pressure and is and exit stage adapted to deliver said fluid out of said pump.
Typically, said return channels are vane type return channels.
Typically, said intermediate plate is a diffuser plate.
Typically, all stages and components, therein, are axially aligned.
1 Typically, said delivery volute casing comprises an inner plate from which axially flowing fluid with high velocity of fluid is diffused into pressure and fluid is channeled orthogonally into an exit path.
Additionally, said pump comprises at least an intermittent stage for said multi-stage centrifugal pump, said intermittent stage comprising at least an impeller and at least an intermediate plate with return channels.
Typically, said at least a first stage comprises at least a suction annular casing adapted to be diffuser type suction casing.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates an exploded view of a 2-stage centrifugal pump of the prior art;

Figure 2 illustrates a sectional exploded view of a 2-stage centrifugal pump of the prior art; and
Figure 3 illustrates a flow path for fluid entering, passing, and exiting the centrifugal pump of the prior arts of Figures 1 and 2.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 4 illustrates an exploded view of a 2-stage centrifugal pump;
Figure 5 illustrates a sectional exploded view of a 2-stage centrifugal pump;
Figure 6 illustrates a flow path for fluid entering, passing, and exiting the centrifugal pump of Figures 4 and 5;
Figure 7a illustrates a comparative graph of head versus flow rate while comparing prior art's (old design) multi-stage centrifugal pump with current invention's (new design) multi-stage centrifugal pump;
Figure 7b illustrates a comparative graph of power versus flow rate while comparing prior art's (old design) multi-stage centrifugal pump with current invention's (new design) multi-stage centrifugal pump; and
Figure 7c illustrates a comparative graph of efficiency versus flow rate while comparing prior art's (old design) multi-stage centrifugal pump with current invention's (new design) multi-stage centrifugal pump.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a multi-stage centrifugal pump. Figure 4 illustrates an exploded view of a 2-stage centrifugal pump. Figure 5 illustrates a sectional exploded view of a 2-stage centrifugal pump.

Figure 6 illustrates a flow path for fluid entering, passing, and exiting the centrifugal pump of Figures 4 and 5.
In accordance with an embodiment of this invention, there is provided a first stage for the multistage centrifugal pump.
In at least an embodiment of the first stage for the multi-stage centrifugal pump, there is provided a suction annular casing (22) at suction side. This suction annular casing has a first plate with an inside annular rim of standard thickness. This suction annular casing aids in diffusion on fluid after exit from the first Impeller.
In at least an embodiment of the first stage for the multi-stage centrifugal pump, there is provided a first impeller (24). This impeller is a standard design impeller, which design is constant through the multiplicity of stages. The impeller channelises the flow and imparts velocity to fluid as shown in Figure 6 of the accompanying drawings.
In at least an embodiment of the first stage for the multi-stage centrifugal pump, there is provided an intermediate plate with return channels (26). This intermediate plate separates the stages in the multiplicity of stages of the multi-stage centrifugal pump. Typically, the return channels are vane type return channels. This intermediate plate is the diffuser plate. This removes cross overflow path and channelises the fluid as shown in Figure 6 of the accompanying drawings. Vane type return channels between the impellers are used to diffuse the velocity generated in first impeller partially and also it will take water back to centre up to suction of next stage. Overall efficiency of the pump increases due to removal of cross overflow path.
In accordance with another embodiment of the invention, there is provided an end stage for the multi-stage centrifugal pump.
In at least an embodiment of the end stage for the multi-stage centrifugal pump, there is provided an end impeller (28). This impeller is similar to the first impeller. The impeller channelises the flow of fluid as shown in Figure 6 of the accompanying drawings.

In at least an embodiment of the end stage for the multi-stage centrifugal pump, there is provided a delivery volute casing (30) adapted to diffuse velocity into pressure-and to deliver the fluid at the exit stage. This delivery volute casing has been designed to comprise an inner plate (32) from which axially flowing fluid is channeled orthogonally into an exit path, The flow of fluid towards and through the exit path is seen in Figure 6 of the accompanying drawings. The last stage casing is volute type casing.
All the stages and components, therein, are axially aligned.
In accordance with yet another embodiment of the invention, there is provided an intermittent stage for the multi-stage centrifugal pump. In its most basic form, intermittent stage(s) is not required. In multi-stage pumps, a plurality of intermittent stages may be required. In order to expand the pump from a 2-stage pump to a multi-stage pump, the configuration of an impeller (similar to the other impellers) followed by an intermediate plate with return channels is repeated; depending upon the number of stages required. Thus, in any configuration, two adjacently located impellers are separated by the intermediate plate with return channels.
Velocity of fluid generated by the 1st impeller is partially diffused into pressure by annular casing type diffuser and this pressurised fluid is brought back to the next stage inlet by means of vane type return channels, also during this remaining velocity is diffused into pressure by vane type return channel, located on the intermediate plate. In this type of arrangement, losses are very less. The vane type return channels are designed with approximately constant flow area. The use of return channels aid in reduction of total length and width of the pump - even in multi-stage designing. Furthermore, path of fluid flow is changed to be less complicated. Length of shaft from motor bearing support is very small as compared to prior art, and hence, overhang of shaft is small which results in less shaft stresses and deflection. Shaft diameter can also be reduced in the current design. Since, impellers are exactly same in each stage, only pattern for impeller is required, which saves initial investment in pattern designing and inventory.
In this invention, the invention step is to combine three different type of velocity diffusion technologies, that is first volute casing type (constantly increasing area orthogonally - used in second stage), second is annular casing type (simple cylindrical part with neck area - used in first stage), and third is vane type diffuser (return channels with optimum area- used in between

the stages) in centrifugal pump. Due to optimum used of diffusion technologies, losses are less as well as complexity of required parts is less.
Figure 7a illustrates a comparative graph of head versus flow rate while comparing prior art's (old design) multi-stage centrifugal pump with current invention's (new design) multi-stage centrifugal pump.
Figure 7b illustrates a comparative graph of power versus flow rate while comparing prior art's (old design) multi-stage centrifugal pump with current invention's (new design) multi-stage centrifugal pump.
Figure 7c illustrates a comparative graph of efficiency versus flow rate while comparing prior art's (old design) multi-stage centrifugal pump with current invention's(new* design) multi-stage centrifugal pump.
In all the three graphs, advantages of the current invention's multi-stage centrifugal pump are evidently seen.
The INVENTIVE STEP of this invention lies in providing an annular diffuser at the suction side, providing vane type return channel diffusers intermittently, between adjacently located impellers in multiple stages, and providing delivery volute casing at the delivery side thereby smooth exit of fluid outside the pump. Each of the impellers used in each of the stages are of same design, thereby reducing inventory and associated costs, thereof. As compared to conventional multistage pumps with diffuser design, the initial stage casings will have diffusers but last stage casing will be volute type. This avoids exit losses at delivery as volute allows smooth exit.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A multi-stage centrifugal pump with hybrid diffusion technology, said pump comprising:
. • at least a first stage for said multi-stage centrifugal pump comprising at least a suction annular casing, said first stage further comprising at least at least a first impeller;
• at least an end stage for said multi-stage centrifugal pump comprising at least an end impeller, said end stage further comprising at least a delivery volute casing adapted to deliver said fluid at the exit stage; and
• at least an intermediate plate with return channels, said intermediate plate adapted to separate stages in the multiplicity of stages of said multi-stage centrifugal pump, thereby providing at least an intermediate plate between any two adjacently located impellers in said multi-stage centrifugal pump.

2. The multi-stage centrifugal pump as claimed in claim 1 wherein, said at least a first stage for said multi-stage centrifugal pump is a suction side stage.
3. The multi-stage centrifugal pump as claimed in claim 1 wherein, said suction annular
■-.■-.. i-* * ■ -* casing comprises at least a first plate with an inside annular rim of standard thickness.
4. The multi-stage centrifugal pump as claimed in claim 1 wherein, said suction annular casing comprises diffusers which aid in diffusion on fluid during exit from said at least a first impeller.
5. The multi-stage centrifugal pump as claimed in claim 1 wherein, said end stage for said multi-stage centrifugal pump comprises said delivery volute casing to diffuse velocity into pressure and is and exit stage adapted to deliver said fluid out of said pump.
6. The multi-stage centrifugal pumps as claimed in claim 1 wherein, said return channels are vane type return channels.
7. The multi-stage centrifugal pump as claimed in claim 1 wherein, said intermediate plate is a diffuser plate.

8. The multi-stage centrifugal pump as claimed in claim 1 wherein, all stages and components, therein, are axially aligned.
9. The multi-stage centrifugal pump as claimed in claim 1 wherein, said delivery volute casing comprises an inner plate from which axially flowing fluid with high velocity of fluid is diffused into pressure and fluid is channeled orthogonally into an exit path.
10. The multi-stage centrifugal pump as claimed in claim 1 wherein, said pump comprising at least an intermittent stage for said multi-stage centrifugal pump, said intermittent stage comprising at least an impeller and at least an intermediate plate with return channels.
11. The multi-stage centrifugal pump as claimed in claim 1 wherein, said at least a first stage comprising at least a suction annular casing adapted to be diffuser type suction casting.