BR102016021270A2 - pump to drive a highly viscous fluid - Google Patents

Abstract

A pump for conducting a highly viscous fluid is proposed comprising a housing (2) with at least a first inlet (3) and an outlet (4) for the fluid, a pusher (5) for conducting fluid from the inlet (3) to outlet (4), wherein the impeller (5) is arranged on a rotary shaft (6) for rotation about an axial direction (a) and comprises a front cover (7) facing the first inlet (3) of the pump wherein the housing (2) is provided with an immobile impeller opening (8) for receiving the front cover (7) of the impeller (5) and having a diameter (d), wherein the front cover (7) and the immobile impeller opening (8) forms a slot (9) having a length (1) in the axial direction (a), wherein the ratio of the length (1) of the slot (9) and the diameter (d) of the impeller opening (8) is at most 0.092.

Description

Invention Patent Descriptive Report for "PUMP FOR DRIVING A HIGH VISCY FLUID".

The invention relates to a pump for conducting a highly viscous fluid according to the preamble of the independent claim.

Pumps for pumping highly viscous fluids are used in many different industries, for example in the oil and gas processing industry to conduct hydrocarbon fluids. Here, these pumps are used for different applications such as oilfield crude oil extraction, oil transportation or other hydrocarbon fluids through pipelines or within refineries. But also in other industries, for example the food industry or the chemical industry there is usually a need to drive highly viscous fluids.

The viscosity of a fluid is a measurement for the internal friction generated in a flowing fluid and a characteristic property of the fluid. Within the framework of this application the term "viscosity" or "viscous" is used to draw the kinematic viscosity of the fluid and the term "highly viscous fluid" must be understood such that the fluid has a kinematic viscosity of at least 10-4 m2. / s, which is 100 centistokes (cSt).

For pumping highly viscous fluids it is known to use centrifugal pumps. Pumping highly viscous fluids with centrifugal pumps requires considerably more pump energy than, for example, pumping water. The higher the fluid viscosity becomes, the more energy the pump needs to deliver the required pumping volume. Especially in the oil and gas industry the main focus - at least in the past - was on pumping volume, ie the flow generated by the pump, and pump reliability rather than pump efficiency. However, lately more efficient pump use is sought. It is desired to have the highest possible ratio of energy, especially hydraulic energy, delivered by the pump to the energy required to drive the pump. This desire is mainly based on a heightened awareness of environmental protection and a responsible person who deals with available resources as well as high energy costs.

[005] To improve the efficiency of a pump for pumping highly viscous fluids, it is known to use impeller specific designs, especially impellers with high main coefficients. The main impeller coefficient may be increased, for example, by increasing the blade exit angle or the number of blades or the width of the impeller outlet. Instead of these measurements there is still a need to further improve the efficiency of a pump to pump highly viscous fluids.

Thus, it is an object of the invention to propose a new pump to drive highly viscous fluids that have a better efficiency, ie a high ratio of the energy delivered by the pump when pumping the fluid into the energy that is supplied to the pump to drive the pump. bomb The subject matter of the invention which fulfills this object is characterized by the features of the independent claim.

Thus, according to the invention a pump for conducting a highly viscous fluid is proposed, comprising a housing with at least a first inlet and an outlet for the fluid, an impeller for conducting fluid from the inlet to the outlet, wherein the impeller is arranged on a pivot axis for rotation about an axial direction and comprises a front cover facing the first pump inlet, the housing is provided with an immobile impeller opening for receiving the impeller front cover and having a diameter, wherein the front cover and the opening of the immobile impeller form a slot having a length in the axial direction, wherein the ratio of the slot length and the diameter of the impeller opening is at most 0.092.

The invention is in particular based on the finding that pump efficiency can be increased by pumping highly viscous fluids by designing the slit between the impeller front cover and the considerably shorter immobile impeller opening than was made. in the prior art.

The slot which is sometimes also designed as the maze is required to seal the high pressure side of the impeller, more particularly the lateral space, against the pump inlet. The impeller is arranged in the opening of the immobile impeller which is a part of the pump that is immovable with respect to the housing and adapted to receive the impeller. On the mounted side, the impeller is located in said impeller opening such that there is a gap or maze between the outer circumferential surface of the impeller front cover and the inner circumferential surface of the immobile impeller opening. This slot has an axial length that provides a seal between the side space on the high pressure side of the impeller and the pump inlet, which is the low pressure side of the pump.

During pump operation, a back flow is generated flowing from the high pressure side of the impeller, which is to a single stage pump in the region near the pump outlet, through the side space and through the gap between the front cover and impeller opening immobile back to the low pressure side of the impeller.

The slot or maze, respectively, is designed as a radial clearance or labyrinth seal, ie it provides clearance with respect to the radial direction. Thus, the main flow through the slot is in the axial direction, ie parallel to the axis. This has to be distinguished from an axial or labyrinth clearance seal that extends perpendicularly or obliquely to the axis, so the main flow through an axial clearance seal is in the radial or oblique direction with respect to the radial direction. In an axial clearance seal, the clearance in the axial direction changes in relative motion of the motionless part and the pivoting part in the axial direction, where in a radial clearance seal the clearance in the radial direction changes in relative motion of the property portion. and the rotating part in the radial direction.

An essential finding is that due to the short axial length of the slit (i.e. the maze) proposed by the invention, slit energy losses are decreasing inter alia due to reduced drag in the lateral space. On the other hand, it can be expected that shortening the crack would result in a reduced sealing action thereby increasing the return flow at the pump. However, an increase in return flow reduces pump efficiency and thus violates improved efficiency. Thus, the unexpected finding is that by shortening the slit with respect to the axial direction all pump efficiency increases despite the risk of improved return flow.

According to the invention, the slot length should not exceed 0.092 times the diameter of the impeller opening.

The ideal slit length depends on a number of factors, for example fluid viscosity. Thus, depending on the specific application it may be preferred that the ratio of slot length and impeller aperture diameter is at most 0.073 and preferably at most 0.055.

There are still applications for which it is advantageous when the ratio of slot length and impeller aperture diameter is at most 0.037 and preferably at most 0.019.

For practical reasons there is still a preferred lower limit for slot length. According to the preferred design, the ratio of slot length and impeller aperture diameter is at least 0.0001.

In order to generate the desired sealing effect by the slot it is preferred to have a radial clearance between the front cover and the impeller opening which is at most 0.0045 times the diameter of the impeller opening. Radial clearance is the extent of the gap with respect to the radial direction, ie perpendicular to the axial direction, and can be considered as the width of the slot. This radial clearance is the minimum distance between the outer circumferential surface of the impeller front cover and the inner circumferential surface of the immobile impeller opening along the slot.

The two surfaces that delimit the slot can be drawn as level surfaces.

According to another embodiment, the slot comprises a plurality of lands consecutively arranged with respect to the axial direction, wherein two adjacent lands are respectively separated by a groove. In such an embodiment the two surfaces delimiting the slot are not uniform. The outer circumferential surface portion of the impeller front delimiting the slot or the inner circumferential surface portion of the immobile impeller opening delimiting the slot may be provided with a plurality of lands and grooves therebetween. In such an embodiment, the length of the slot in the axial direction is defined as the sum of the lengths of all individual earths in the axial direction. The grooves do not contribute to the overall length of the slot in the axial direction.

According to a preferred embodiment, the immobile inlet opening comprises a wear ring delimiting the slit with respect to the radial direction, the wear ring being arranged immobile with respect to the housing.

Supplementary or as an alternative measure, it is also possible for the impeller to comprise a wear ring delimiting the slot with respect to the radial direction, the wear ring being immobile with respect to the impeller.

The invention is especially suitable for many types of centrifugal pumps. The pump may be designed, for example, as a single suction pump or a double suction pump, as a single stage pump or as a multistage pump. When the pump is designed as a single suction pump, it may have a rear impeller cover in addition to the front cover. In such a design it is also possible for the rear cover of the impeller to form a slot with a portion being immovable with respect to the housing. This slot in the rear cover may be designed in a similar manner as explained with respect to the slot in the front cover of the impeller.

According to a preferred embodiment, the pump is designed as a double suction pump, having a second fluid inlet which is disposed opposite the first pump inlet, wherein the impeller is designed as a double suction impeller. comprising vanes for conducting fluid from both the first inlet and the second inlet to the outlet.

For such a design as a double suction pump it is preferred that the impeller comprises a second front cover facing the second pump inlet, wherein the housing is provided with a second impeller opening immobile to receive the second front cover of the pump. having a diameter, wherein the second front cover and second opening of the immobile impeller form a second slot having a length in the axial direction and wherein the ratio of the length of the second slot and the diameter of the second impeller opening is at most 0.092.

Depending on the specific application, it may be preferred that also the ratio of the length of the second slot and the diameter of the second impeller opening is at most 0.073 and preferably at most 0.055.

There are still applications in which it is advantageous when the ratio of second slot length and second impeller aperture diameter is at most 0.037 and preferably at most 0.019.

Still for the second slot it is advantageous when there is a radial clearance between the second front cover and the second impeller opening which is at most 0.0045 times the diameter of the second impeller opening.

It is an especially preferred measurement when the slot and the second slot are designed essentially in an identical manner.

According to one essential application, the pump is designed for use in the oil and gas industry.

Other advantageous measurements and embodiments of the invention will become apparent from the dependent claims.

The invention will be explained in more detail below with reference to the drawings. Shown in a schematic representation: [0033] Figure 1: A cross-sectional view of a pump embodiment according to the invention, [0034] Figure 2: An enlarged representation of details I in Figure 1, [0035] Figure 3: a sketch of the front cover and a wear ring as part of the immobile impeller opening, [0036] Figure 4: as figure 3, but for one embodiment of the embodiment, [0037] Figure 5: a second design variant of the gap between the front cover and the opening of the immobile impeller; and Figure 6: an illustration of a comparison of a pump according to the invention with prior art pumps.

Figure 1 shows a cross-sectional view of a embodiment of a pump according to the invention which is drawn in its entity with reference numeral 1. Figure 2 shows an enlarged representation of details I in Figure 1. Pump 1 is designed to drive a highly viscous fluid, while the term "highly viscous" has the meaning that the kinematic viscosity of the fluid is at least 10-4 m2 / s, which is 100 centistokes (cSt).

In this embodiment, pump 1 is designed as a single suction single stage centrifugal pump. This design is a preferred embodiment which is in practice useful for many applications. Of course, the invention is not restricted to this design. A pump according to the invention may further be designed as a single suction centrifugal pump or as a multistage centrifugal pump or as any other type of centrifugal pump. Based on the description of the embodiment shown in FIG. 1 and FIG. 2 it is not a problem for one skilled in the art to construct a pump according to the invention which is designed as another type of pump, especially centrifugal pump, for example a pump. single suction

The double suction pump 1 comprises a housing 2 with a first inlet 3, a second inlet 3 'and an outlet 4 for the fluid to be pumped. The fluid may be, for example, crude oil, oil or any other hydrocarbon fluid being highly viscous. Pump 1 has an impeller 5 with a plurality of vanes 51 to drive fluid from first inlet 3 and second inlet 3 'to outlet 4. Impeller 5 is disposed on a rotary axis 6 for rotation about an axial direction A The axial direction A is defined by the axis of the shaft 6 around which the impeller 5 rotates during operation. Axis 6 is rotated by a drive unit (not shown). The direction perpendicular to the axial direction A is referred to as the radial direction.

The first inlet 3 and the second inlet 3 'are arranged opposite each other with respect to the axial direction A. Thus, according to the representation in figure 1, fluid is flowing from both the left and right sides in the direction. A to the impeller 5, while fluid from the first inlet 3 is flowing in the opposite direction to impeller 5 as the fluid from the second inlet 3 '. The impeller 5 carries both fluid arriving from the first inlet 3 and fluid arriving from the second inlet 3 'to the radial direction to the pump outlet 4.

The impeller 5 comprises a front cover 7 covering the vanes 51 and facing the first inlet 3 of the pump 1. Since in this embodiment the impeller 5 is designed as a double suction impeller 5 it comprises a second cover front 7 'facing the second inlet 3' and covering the vanes 51 on the side of the impeller 5 that turns to the second inlet 3 '.

The housing 2 is provided with an immobile impeller opening 8 to receive the front cover 7 of the impeller 5. The immobile impeller opening 8 is immovable with respect to the housing 2 of pump 1 and has a circular cross-sectional diameter D, while diameter D draws the smallest diameter of that portion of the opening of the immobile impeller 8 receiving the front cover 7.

In an analogous form, the housing 2 comprises a second opening of the immobile impeller 8 'to receive the second front cover 7' of the impeller 5.

In the assembled state, the impeller 5 is arranged coaxially within the opening of the immobile impeller 8 so that the outer circumferential surface of the front cover 7 faces the internal circumferential surface of the immobile impeller opening 8. Thus , the front cover 7 and the opening of the immobile impeller 8 form a slot 9 (see also Figure 3) between the front cover 7 and the opening of the immobile impeller 8. Slot 9 is further called a maze. It has an essentially annular shape and provides sealing action as explained below. Slot 9 has a length L which is the extension of slit 9 in axial direction A. Slot 9 extends parallel to axis 6 or parallel to axial direction A, respectively. Thus, the return flow is flowing through slot 9 parallel to axis 6 and in the opposite direction as fluid flowing through respective inlet 3. Thus, viewed in the main flow direction of fluid entering through respective inlet 3 the starting position of slot 9, i.e. the opening through which fluid enters slot 9, is disposed behind the end position of slot 9, i.e. the opening through which fluid exits slot 9.

In an analogous form, a second slot 9 'is formed between the second front cover 7' and the second opening of the immobile impeller 8 '. The second slot 9 'has a length L' in the axial direction A and the second opening of the immobile impeller 8 'has a diameter D'. Slot 9 'extends to axis 6 or parallel to axial direction A, respectively. Preferably, but not necessarily, length L 'is equal to length L and diameter D' is equal to diameter D. Since the design and arrangement of second slot 9 'may be identical as slot 9, the following description is only it will refer to slot 9. It is to be understood that this description applies in a similarly analogous fashion even to second slot 9 '.

Slot 9 or maze 9 seals a side space 10 located on the high pressure side of impeller 5 against the low pressure side of impeller 5 which is located in inlet 3. Side space 10 is located on high side pressure of impeller 5 near pump outlet 1 and bounded by front cover 7 of pump 5 as well as pump housing 2. During pump 1 operation, a back flow is generated from the outlet 4 region through the space 10. The return flow passes through the slot or maze 9 essentially flowing in the axial direction A, ie parallel to the axis 6 and reaches the low pressure side of the impeller 5 near the first inlet 3. It is obvious that the flow of return reduces pump efficiency 1.

Thus, it is one of the functions of slot 9 to provide some sealing action to limit return flow. This is why slot 9 is also called the maze.

It is the basic idea of the present invention to shorten the lengths L (see figure 2 and figure 3) of slot 9 in the axial direction A as compared to known prior art solutions. Although it could be expected that a shortening of length L would result in a high return flow which in turn reduces the efficiency of the pump, it has been found that by shortening the slit length L of all overall pump 1 efficiency can be increased. .

Referring to Figure 2 and Figure 3, the drawing of slot 9 will now be explained in more detail. In the embodiment according to Figure 1, the immobile inlet opening 8 comprises a wear ring 11 delimiting the slot 9 with respect to the radial direction. The wear ring 11 faces the outer circumferential surface of the front cover 7 which is inserted into the immobile inlet opening 8. The wear ring 11 is fixedly mounted to the housing 2, thus the wear ring 11 is immovable with respect to the housing 2.

Figure 3 shows a sketch of the front cover 7 and the wear ring 11 as part of the opening of the immobile impeller 8 to more clearly understand the dimensions of slot 9.

According to the invention, the length L of slot 9 is designed such that the ratio of the length L and the diameter D of the impeller opening 8 is at most 0.092, ie L / D <0.092.

As already mentioned, the diameter D draws the smallest diameter of the immobile impeller opening 8, ie the diameter at this location where the wear ring 11 was closest to the outer circumferential surface of the front cover 7. The length L of slot 9 is the extension in axial direction A of this region where the immobile impeller opening 8 and the front cover 7 approach.

[0054] In the arrangement shown in figure 3, the wear ring 11 is designed with a protrusion 111 in the radial direction. Consequently, the length L of slot 9 is equal to the extent of protrusion 111 in the axial direction 9.

The second parameter defining the geometry of slot 9 is the radial clearance R between the front cover 7 and the opening of the immobile impeller 8 or the wear ring 11, respectively, along the axial extension of slot 9. The clearance Radial R draws the minimum radial clearance along slot 9.

In practice, it has been shown to be advantageous when the radial clearance R does not exceed 0.0045 times the diameter D of the immobile inlet opening 8, ie preferably the R / D condition <0.0045 is met.

The optimal length L of slot 9 depends on its application. There are several factors that influence an appropriate choice of slot length L 9, for example, the kinematic viscosity of the specific fluid to be pumped, the pressure increase generated by the pump, the flow through the pump or other pump operating parameters 1.

For a given set of pump 1 operating parameters, the lengths L of slot 9 should preferably be reduced with increasing viscosity of the fluid to be pumped.

In practice and depending on the application, it may be preferred that the L / D ratio does not exceed 0.073 or more preferred does not exceed 0.055, or even more preferred does not exceed 0.037 or specifically preferred does not exceed 0.019.

According to preferred embodiments of pump 1, the minimum L / D ratio is 0.0001, ie the length L of slot 9 is preferably at least 0.0001 times the aperture diameter of the immobile impeller. 8 or wear ring 11, respectively.

Figure 4 shows in a similar representation to figure 3 a variant of pump mode 1. According to this variant, impeller 5 and more particularly the front cover 7 of impeller 5 comprises a wear ring 11 'which delimits slot 9 with respect to radial direction. The wear ring 11 'is fixedly connected to the impeller 5 and rotatable with the impeller 5. In this embodiment, the opening of the immobile impeller 8 may comprise a wear ring 11, too, but may still be designed without a wear ring.

Figure 5 illustrates a second variant for slot design 9 between the front cover 7 and the opening of the immobile impeller 8. According to the second variant, the opening of the immobile impeller 8 or wear ring 11, respectively , or as an alternative (not shown) the front cover 7 is designed such that slot 9 comprises a plurality of lands 12 consecutively disposed with respect to axial direction A, wherein two adjacent lands 12 are respectively separated by a groove 13. In such a drawing, the total length L of slot 9 is the sum of the individual lengths L1, L2, L3, L4, L5 of all lands 12 in the axial direction. Groove length does not contribute to the total lengths L of slot 9, ie L = L1 + L2 + L3 + L4 + L5. It should be understood that the number of lands and furrows as well as their geometric design shown in figure 5 is exemplary only.

The pump 1 according to the invention has a better pump efficiency as compared to pumps known in the state of the art. Pump efficiency draws the ratio of the energy delivered by the pump and the energy inserted into the pump, ie the energy that is used to drive the pump. The energy delivered by the pump is usually the hydraulic energy generated by the pump 1.

Figure 6 illustrates the comparison of a pump according to the invention with prior art pumps. The graph shows the efficiency of pump P as a function of the viscosity V of the fluid driven by the pump. For the sake of a better understanding the graph is standardized so that the pump efficiency of the prior art pumps P equals the horizontal viscosity axis V, ie the efficiency of the pump P to the prior art pump always stays on the V axis for each viscosity. Thus, the graph directly shows the increase in pump efficiency of pump 1 according to the invention as compared to a prior art pump. The pump efficiency of the pump according to the invention is represented by the K curve. As can be clearly seen, provided that the viscosity of the fluid is greater than a specific value V1, the pump 1 according to the invention has an efficiency of high pump compared to the prior art pump. The efficiency gain is increasing with the fluid viscosity. The specific viscosity value V1 where the pump 1 according to the invention becomes more efficient than the prior art pump is generally less than the value of 10-4 m2 / s. Thus, for a highly viscous fluid the pump 1 according to the invention has a higher pump efficiency than the prior art pump.

Although specific reference has been made for the purpose of explaining one embodiment, where pump 1 is designed as a single suction single stage centrifugal pump, the invention is by no means restricted to such embodiments. The pump according to the invention may be further designed as any other type of centrifugal pump, for example as a single suction pump or as a multistage pump. In particular, the invention is applicable to both centrifugal pumps with a closed impeller, i.e. an impeller having a front cover and a rear cover, and centrifugal pumps with a semi-open impeller, ie having a rear cover, but neither front cover. In such designs where the impeller has a back cover or a back cover only, the slot design 9 according to the invention may be used for the back cover in a similarly similar manner as described herein with reference to the front cover.

Claims (15)

1. Pump for conducting a highly viscous fluid comprising a housing (2) with at least a first inlet (3) and a fluid outlet (4), a pusher (5) for conducting fluid from inlet (3) at the outlet (4), wherein the impeller (5) is disposed on a rotary shaft (6) for rotation around an axial direction (A) and comprises a front cover (7) facing the first inlet (3) of the pump wherein the housing (2) is provided with an immobile impeller opening (8) for receiving the front cover (7) of the impeller (5) and having a diameter (D), wherein the front cover (7) and the immobile impeller opening (8) form a slot (9) having a length (L) in the axial direction (A), characterized in that the ratio of the length (L) of the slot (9) and the diameter (D) of the impeller opening (8) is at most 0.092. Pump according to claim 1, characterized in that the ratio of the length (L) of the slot (9) and the diameter (D) of the impeller opening (8) is at most 0.073 and preferably at most 0.055. . Pump according to any one of the preceding claims, characterized in that the ratio of the length (L) of the slot (9) and the diameter (D) of the impeller opening (8) is at most 0.037 and preferably at maximum 0.019. Pump according to any one of the preceding claims, characterized in that the ratio of the length (L) of the slot (9) and the diameter (D) of the impeller opening (8) is at least 0.0001. Pump according to one of the preceding claims, characterized in that it has a radial clearance (R) between the front cover (7) and the impeller opening (8) which is at most 0.0045 times the diameter ( D) from the impeller opening (8). Pump according to any one of the preceding claims, characterized in that the slot (9) comprises a plurality of lands (12) consecutively disposed with respect to the axial direction (A) and in which two adjacent lands (12) are respectively separated by a groove (13). Pump according to any one of the preceding claims, characterized in that the immobile inlet opening (8) comprises a wear ring (11) delimiting the slot (9) with respect to the radial direction, the locking ring. wear (11) being disposed immovably with respect to the housing (2). Pump according to one of the preceding claims, characterized in that the impeller (5) comprises a wear ring (11 ') delimiting the slot (9) with respect to the radial direction, the wear ring ( 11 ') being immobile disposed with respect to the impeller (5). Pump according to one of the preceding claims, being designed as a double suction pump having a second inlet (3 ') for the fluid being disposed opposite the first inlet (3) of the pump, characterized in that that the impeller (5) is designed as a double suction impeller (5) comprising vanes (51) to drive fluid from both the first inlet (3) and the second inlet (3 ') to the outlet (4). Pump according to Claim 9, characterized in that the impeller (5) comprises a second front cover (7 ') facing the second inlet (3') of the pump, wherein the housing (2) is provided. with a second immobile impeller opening (8) for receiving the second impeller front cover (7 ') and having a diameter (D'), wherein the second front cover (7 ') and the second immobile impeller opening (8) ') form a second slot (9') having a length (L ') in the axial direction (A) and wherein the ratio of the length (L') of the second slot (9 ') and the diameter (D') of the second impeller opening (8 ') is at most 0.092. Pump according to claim 9 or 10, characterized in that the ratio of the length (L ') of the second slot (9') and the diameter of the second impeller opening (8 ') is a maximum of 0.073 and preferably at most 0.055. Pump according to any one of claims 9 to 11, characterized in that the ratio of the length (L ') of the second slot (9') and the diameter (D ') of the second impeller opening (8' ) is at most 0.037 and preferably at most 0.019. Pump according to any one of claims 9 to 12, characterized in that it has a radial clearance between the second front cover (7 ') and the second impeller opening (8') which is at most 0.0045 instead the diameter (D ') of the second impeller opening (8). Pump according to any one of claims 9 to 12, characterized in that the slot (9) and the second slot (9 ') are designed essentially in an identical manner. Pump according to any one of the preceding claims, characterized in that it is designed for use in the oil and gas industry.