KR20200089954A - Centrifugal pump comprising partial diffuser vanes - Google Patents

Abstract

Disclosed is a centrifugal pump, which includes: an impeller having a plurality of blades formed in the circumferential direction; and a plurality of diffusers extending from the impeller toward a gas outlet, wherein the diffuser includes: at least one diffuser is a vane positioned on a shroud side, and at least one diffuser is a vane positioned on a hub side. The centrifugal pump provided in one aspect of the present invention has high efficiency in the vicinity of the design flow rate including the partial diffuser vane, and at the same time can recover the static pressure in a wide flow rate range. In particular, the centrifugal pump including the partial diffuser vane in a specific arrangement can effectively delay the point in time when the slope of the pressure recovery coefficient becomes positive.

Description

Centrifugal pump comprising partial diffuser vanes

It relates to a centrifugal pump comprising a partial diffuser vane.

In the centrifugal pump, the diffuser plays a role of converting the velocity energy obtained by the impeller into a form of static pressure, and can be divided into a volute, a vaned diffuser, and a vanless diffuser depending on the type. have. Among these, the vane diffuser has an advantage of high pressure recovery, but has a disadvantage in that the operating range is relatively limited due to the interaction with the impeller. On the other hand, in the case of a vaneless diffuser, the pressure recovery is low, but the operating range is wide.

A study on the study of the internal flow and performance characteristics of a centrifugal machine equipped with a vane diffuser has been carried out by many researchers, and in the case of a vane-free diffuser, rather than a study on the performance characteristics, internal flow characteristics such as rotating stall Studies have been conducted on.

Meanwhile, in order to take advantage of a vane diffuser and a vane-free diffuser, some researchers have studied a partial diffuser vane that combines them.

Conventionally, Zhu et al. have conducted experiments by applying a half vane diffuser to a centrifugal pump (International Communications in Heat and Mass Transfer 79 (2016) 114-127), and in the literature, the vane diffuser in the form of a blade row is used. Disclosed is an analysis of the effect of vane height on performance. However, most of the previous studies confirmed only the performance characteristics through experiments, so the internal flow characteristics could not be confirmed.

An object of one aspect of the present invention is to provide a centrifugal pump having excellent hydraulic efficiency and internal flow characteristics of a centrifugal pump.

In order to achieve the above object, in one aspect of the present invention

An impeller having a plurality of blades formed in a circumferential direction; And

It includes a plurality of diffusers formed extending from the impeller toward the gas outlet,

The at least one diffuser includes vanes located on the shroud side,

At least one diffuser is provided with a centrifugal pump comprising a vane located on the hub side.

The centrifugal pump provided in one aspect of the present invention includes a partial diffuser vane, has high efficiency in the vicinity of the design flow rate, and at the same time can recover static pressure in a wide flow range. In particular, a centrifugal pump including a partial diffuser vane in a specific arrangement can effectively delay the time point when the slope of the pressure recovery coefficient becomes positive.

1 is a schematic view showing an example of a centrifugal pump provided in one aspect of the present invention;
2 is a schematic view showing a portion including one impeller and two diffusers in a centrifugal pump provided in one aspect of the present invention;
3 is a schematic view showing a cross section of an impeller and a diffuser in a centrifugal pump provided in one aspect of the present invention;
4 is a schematic view showing a vane located inside and a part including one impeller and two diffusers in a centrifugal pump provided in one aspect of the present invention;
5 is a schematic view showing a three-dimensional shape of the centrifugal pump model applied in Examples and Comparative Examples;
Fig. 6 (a) shows the calculation region and boundary conditions used in the numerical analysis of the present invention; Figure 6 (b) shows an example of a grid system used in the numerical analysis of the present invention;
7 shows the average voltage distribution in the pitch direction at the exit of the diffuser;
8 is a comparison of the curves of the head lift coefficient and efficiency for Example 1 and Comparative Examples 1 to 3;
9 is a comparison of the diffuser pressure recovery coefficient (CP) curves for Example 1 and Comparative Examples 1 to 3;
10 shows the distribution of the diffuser pressure recovery coefficient according to the flow rate at 50% span for Comparative Example 1;
11 shows the velocity vector distribution according to the flow rate at 50% span for Comparative Example 1;
Figure 12 shows the pressure recovery coefficient distribution according to the radial position of the diffuser of Example 1 and Comparative Examples 1 to 3;
13 shows the average flow angle distribution in the pitch direction at r/r ₂ =1.06, 1.23 and 1.40;
14 shows the velocity distribution in each cross section according to the radial position when Φ/ Φ _d =0.6;
15 shows a three-dimensional iso-surface distribution with a pressure recovery coefficient of -1 in the diffuser region when Φ/ Φ _d =1.8.

In one aspect of the invention

An impeller 100 having a plurality of blades formed in a circumferential direction; And

It includes a plurality of diffusers 200 formed extending from the impeller 100 toward the gas outlet,

At least one diffuser 200 includes a vane 211 located on the shroud 210 side,

The at least one diffuser 200 provides a centrifugal pump 1000 including a vane 221 located on the hub 220 side.

At this time, FIGS. 1 to 4 show an example of the centrifugal pump 1000 provided in one aspect of the present invention,

Hereinafter, a centrifugal pump 1000 provided in one aspect of the present invention will be described in detail with reference to FIGS. 1 to 4.

1 and 2, the centrifugal pump 1000 provided in one aspect of the present invention includes an impeller 100 and a plurality of diffusers 200. In addition, it may include an inlet pipe 300 connected to the impeller.

The impeller 100 has a plurality of blades formed in a circumferential direction, and may be positioned to be rotatable. The shape of the impeller is not limited, and may be an impeller generally applied to a centrifugal pump, a centrifugal compressor, or the like.

The diffuser 200 is formed extending from the impeller 100 toward the gas outlet, and can convert kinetic energy of a fluid (eg, gas) drawn from the inlet pipe 300 into a static pressure.

The diffuser located at the rear end of the impeller of the conventional centrifugal pump plays a role of converting the velocity energy obtained by the impeller into a form of static pressure. The dual vane diffuser has the advantage of high pressure recovery, but has a relatively limited operating range due to the interaction with the impeller, while the vane diffuser has a wide operating range. Pressure recovery has a low drawback.

Accordingly, the present invention provides a centrifugal pump to which a partial diffuser vane is applied.

In the centrifugal pump 100 provided in one aspect of the present invention, at least one diffuser 200 includes a vane 211 positioned on the shroud 210 side, and at least one diffuser 200 is a hub ( 220) includes a vane 221 located on the side.

The vanes in conventional diffusers are known. Generally, vanes that extend completely between the shroud wall and the hub wall have been used. Also known are ribbed vanes that do not extend completely between the walls of the diffuser.

At this time, as shown in Figures 3 and 4, the centrifugal pump 100 provided in one aspect of the present invention includes a vane (211, 221), at least one or more of the vanes to the shroud 210 side Located. At the same time, at least one of the vanes is located on the hub 220 side.

The vane 211 located on the shroud 210 side preferably has a span height of 25% to 75%, more preferably a span height of 30% to 70%, and a span of 40% to 60% It is preferred to have a height, preferably to have a span height of 45% to 55%. The vane 211 is formed on the wall of the shroud, but its height may be 30% to 70% of the space between the shroud and the hub, and may be 40% to 60%, and 45% to 55%.

In addition, the vane 221 located on the hub 220 side preferably has a span height of 25% to 75%, more preferably 30% to 70% of a span height, and 40% to 60% It is preferred to have a span height of 45% to 55%. The vane 221 is formed on the wall of the hub, but may have a height of 30% to 70% of the space between the shroud and the hub, 40% to 60%, and 45% to 55%.

Further, the plurality of diffusers 200 may be alternately positioned with a diffuser including a vane 211 positioned on the shroud 210 side and a vane 221 positioned on the hub 220 side. Referring to FIG. 4, when one diffuser includes a vane formed on a shroud wall, the diffuser positioned adjacent thereto includes a vane formed on the hub wall.

As described above, the centrifugal pump 1000 provided in one aspect of the present invention includes a partial diffuser vane, has high efficiency in the vicinity of the design flow rate, and can recover static pressure in a wide flow range. In particular, a centrifugal pump including a partial diffuser vane in a specific arrangement can effectively delay the time point when the slope of the pressure recovery coefficient becomes positive.

Hereinafter, the present invention will be described in detail through examples, comparative examples, and experimental examples. The following is intended to explain the present invention in more detail, and is merely for explaining the effect, and the scope of the present invention is not limitedly interpreted by the following description.

< Example 1 and Comparative example 1 to 3>

5 shows the three-dimensional shape of the centrifugal pump model applied as examples and comparative examples, and detailed shape information of the impeller and the diffuser is shown in Table 1 below.

Impeller defuser Entrance curvature radius R ₁ =141.13 Entrance curvature radius R ₃ =259.00 Exit curvature radius R ₂ =258.60 Exit curvature radius R ₄ =469.35 Outlet width 38.49 Outlet width 40 Outlet blade angle 22.3 deg Outlet blade angle 10.21 deg Blade count Z ₁ =7 Blade count Z ₂ =8

In Comparative Example 1 (FDV), a diffuser vane in the form of a channel without a gap as a reference shape was formed, and in Comparative Example 2 (PHDV), a diffuser vane of 50% span height installed in a hub was formed, and Comparative Example 3 (PTDV) As a result, a 50% span height diffuser vane installed in the shroud was formed.

In Example 1 (PSDV), a diffuser vane having a 50% span height vane alternately installed on a hub and a shroud is shown.

< Experimental Example >

-Numerical analysis method

For the analysis of compressible steady-state flow, ANSYS CFX 15.0, a commercial flow analysis program, was used, and the impeller shape definition, lattice system generation, boundary condition definition, flow analysis, and result analysis were Blade-Gen, Turbo-Grid, CFX-Pre, and CFX respectively. -It was carried out using Solver and CFX-Post. As a turbulence model, a k - ω shear stress transport (SST) model, which is effective in predicting flow separation due to a back pressure gradient and is known to be accurate for turbomachinery, was used.

Fig. 6(a) shows the calculation region and boundary conditions used in the numerical analysis of the present invention. The calculation area consisted of inlet piping, impellers and diffusers, and included single or multiple impeller and diffuser areas using periodic conditions. The rotational speed of the impeller is 1710 rpm, the working fluid by taking into account the similarity of the copper 20 ℃ water viscosity 15 × 10 ^- was used as the air 20 ℃ having a ⁶ m ² / s. Voltage and mass flow rates were given for the inlet and outlet boundary conditions, respectively. For the wall condition, the adhesive condition was used, and the stage method, which is a method of transferring properties by averaging the exit flow of the rotor in the circumferential direction, was applied as a method for treating the stator-to-wing interface.

Figure 6 (b) shows an example of a lattice system used in the numerical analysis of the present invention. It consists of a hexahedral grid for the inlet piping, impeller and diffuser areas, and maintains the y ⁺ of the first lattice point near the solid interface below 1.2, so that a low-Reynolds number SST turbulence model is applied. A lattice dependence test was performed to secure a lattice system that did not affect the number of lattices.

7 shows the average voltage distribution in the pitch direction at the exit of the diffuser, and the results obtained using 77, 142 and 2.3 million grating systems were compared. As can be seen in FIG. 7, since the results of the analysis of 1.42 million and 2.3 million grid systems do not differ significantly, 1.42 million grid systems were selected as grid systems to be collectively applied to future analysis in order to secure economic time of analysis.

Residuals of continuous equations and momentum equations were 10 ^-4 or less, and changes in the performance function per analysis number of 100 times were 0.3% or less. As a result of performing parallel calculation using a PC equipped with an Intel i7 2.67 GHz CPU, on average, 3 hours and 30 minutes for Comparative Example 1 (FDV), 8 hours for Comparative Example 2 (PHDV) and Comparative Example 3 (PTDV) And Example 1 (PSDV) took about 14 hours and 20 minutes.

-Performance function

For quantitative evaluation of hydraulic performance according to the arrangement of the partial diffuser vanes, the flow coefficient ( Φ ), lift coefficient ( ψ ), efficiency ( η ) and diffuser pressure recovery coefficient ( C _P,d ) are as follows It was defined as

<Equation 1>

<Equation 2>

<Equation 3>

<Equation 4>

(In Equations 1 to 4, p , p ^T , Q , Τ , and ω denote pressure, voltage, flow rate, torque, and angular velocity, respectively, and r ₂ and b ₂ denote impeller outlet radius and impeller outlet width, respectively. Subscripts 1, 2, 3, and 4 indicate the impeller inlet, impeller outlet, diffuser inlet, and diffuser outlet, respectively.)

) 및 압력회복계수가 0과 최대가 되는 지점에서의 유량의 차와 설계 유량의 비(

=(

-

)/

)를 정의하였다.Performance variable to define the effective operating range of the diffuser, the ratio of the flow rate to the design flow rate at the point where the pressure recovery coefficient is the maximum (

) And the ratio of the flow rate to the design flow rate at the point where the pressure recovery coefficient becomes 0 and the maximum (

=(

-

)/

).

-Result analysis

8 is a comparison of the efficiency curves for Example 1 and Comparative Examples 1 to 3 and the efficiency curves, and in Comparative Example 1 (FDV), shows the highest efficiency in the vicinity of Φ / Φ _d = 0.7, and the highest efficiency point. It tends to decrease rapidly before and after. Comparative Example 2 (PHDV), Comparative Example 3 (PTDV) and Example 1 (PSDV) show the highest efficiency in the vicinity of Φ / Φ _d =1.0, and a gentle slope over a wide range of 0.6< Φ / Φ _d <1.4 It can be seen that it has a high efficiency. In the case of the positive head coefficient, Comparative Example 1 (FDV) shows a large value at Φ / Φ _d <0.7, and then it can be confirmed that it decreases with a steep slope, Comparative Example 2 (PHDV), Comparative Example 3 (PTDV), and Example 1 (PSDV) shows a larger value than Comparative Example 1 at Φ / Φ _d >0.7, and it can be seen that it decreases with a gentle slope as the flow rate increases.

Figure 9 is a comparison of the diffuser pressure recovery coefficient ( C _P ) curve for Example 1 and Comparative Examples 1 to 3, in the case of Comparative Example 1 (FDV) shows a high value of 0.68 in Φ / Φ _d = 0.6, As the flow rate increases, it decreases rapidly, and the pressure recovery coefficient value is 0 near Φ / Φ _d =0.95 to reach a state where no more static pressure can be recovered. On the other hand, in Comparative Example 2 (PHDV), Comparative Example 3 (PTDV) and Example 1 (PSDV), the maximum value of the pressure recovery coefficient is 0.56, which is lower than that of Comparative Example 1 (FDV), but Φ / Φ _d = It can be seen that by having a positive diffuser pressure recovery coefficient value up to 1.8, it is possible to recover the static pressure over a wide flow range.

Table 2 below summarizes the main performance functions ( η _d , C _p,d , Φ _{cp, max} / Φ _d , Φ _op / Φ _d ) for each shape. In the case of the efficiency ( η _d ) at the design flow rate, the partial diffusers of Comparative Example 2 (PHDV), Comparative Example 3 (PTDV), and Example 1 (PSDV) have a value of 0.12 or more higher than Comparative Example 1 (FDV). As can be seen, the size of the values of the three arrays did not differ significantly. The pressure recovery coefficient ( C _p,d ) at the design flow rate is -0.3222 in Comparative Example 1, indicating that a large static pressure loss occurs at the design flow rate, while the partial diffuser has a positive value, of which In the case of Example 1 (PSDV), it was confirmed that 0.5620 was a significantly higher value.

Comparative Example 1 (FDV) Comparative Example 2 (PHDV) Comparative Example 3 (PTDV) Example 1 (PSDV) η _d 0.7802 0.9039 0.9038 0.9040 C _p,d -0.32222 0.5544 0.5485 0.5620 Φ _{cp, max} / Φ _d 0.6000 1.0500 1.1500 0.9500 Φ _op / Φ _d 0.3250 0.7500 0.8500 0.8500

On the other hand, the Φ _{cp, max} / Φ _d and Φ _op / Φ _d values of Comparative Example 1 (FDV) are 0.6000 and 0.3250, respectively, which are the shapes where the slope of the pressure recovery coefficient starts to be positive, evaluated to 0.6000. At the smallest flow rate, the slope of the pressure recovery coefficient changes to positive, but the area where the pressure recovery coefficient is positive is 0.3250, which is very small compared to other shapes and has a relatively narrow operating range compared to the evaluated shapes. On the other hand, Example 1 (PSDV) has the highest efficiency (0.9040) in the design flow rate compared to Comparative Example 2 (PHDV) and Comparative Example 3 (PTDV), and has a low Φ _{cp, max} / Φ _d value of 0.9500. By showing the operating stability in the low flow rate region, and having a large Φ _op / Φ _d value of 0.8500 at the same time, it has a relatively wide operating area. Therefore, it can be seen that the centrifugal pump of Example 1 (PSDV) according to the present invention has the best performance compared to other arrangements in securing hydraulic performance or operating area.

10 shows the distribution of the diffuser pressure recovery coefficient according to the flow rate at 50% span for Comparative Example 1 (FDV), in the case of Φ / Φ _d = 0.6 shows a high pressure recovery coefficient distribution in the region except the inlet, Φ / Φ _d = 0.8 shows a low pressure recovery coefficient inside the diffuser flow path. As a result, when Φ / Φ _d =1.0, it shows a low pressure recovery in the rest of the area except the inlet, and especially a low pressure recovery coefficient value at the inlet of the diffuser flow.

Figure 11 shows the velocity vector distribution according to the flow rate at 50% span for Comparative Example 1 (FDV), in the case of Φ / Φ _d = 0.6, the reverse flow begins to occur at the trailing edge of the diffuser vane, the flow rate increases Accordingly, it can be seen that a reverse flow region develops near the diffuser suction surface. This causes a reduction in the effective area of the flow path inside the diffuser. Therefore, as can be seen in Φ / Φ _d = 1.0, a high flow rate in the reduced flow path leads to a state in which pressure cannot be sufficiently recovered (see FIG. 10).

Figure 12 shows the pressure recovery coefficient distribution according to the radial position of the diffuser of Example 1 and Comparative Examples 1 to 3. In the case of Φ / Φ _d = 0.6 (Fig. 12 (a)), it can be seen that the pressure recovery coefficient also increases as the radial distance increases in common. In the case of Comparative Example 1 (FDV), 1.05< It can be seen that in the region of r / r ₂ <1.3, the rising width of the pressure recovery increases, and the value increases while maintaining a higher value than in other cases. In the case of partial diffusers (PHDV, PTDV, PSDV), it can be seen that Example 1 (PSDV) has a relatively high pressure recovery coefficient compared to other partial diffusers in all sections. In Figure 12 (b) ( Φ / Φ _d = 1.0), it can be seen that the difference between the pressure recovery coefficient distribution of Comparative Example 1 (FDV) and the partial diffuser is obvious, and in Comparative Example 1 (FDV), r / r ₂ = It decreases rapidly from around 1.05 to 1.3 and then increases gradually, but has a considerably lower pressure recovery coefficient value than a partial diffuser. In the case of the partial diffusers, it can be confirmed that the difference in the pressure recovery coefficient according to the radial position is not large. Figure 12 (c) shows the distribution of Comparative Example 2 (PHDV), Comparative Example 3 (PTDV), and Example 1 (PSDV) at Φ / Φ _d =1.8, commonly in the vicinity of r / r ₂ =1.25 It shows the smallest pressure recovery coefficient value and can be seen to increase gradually thereafter. In the case of Comparative Example 3 (PTDV), the reduction width is relatively small compared to other cases, and thus the pressure recovery coefficient value is relatively high in the subsequent section.

Figure 13 shows the average flow angle distribution in the pitch direction at r / r ₂ =1.06, 1.23 and 1.40. 13 (a) ( Φ / Φ _d = 0.6) in Comparative Example 2 (PHDV) r / r ₂ As the value increases, the flow angle near the hub increases, but the flow angle near the shroud maintains a negative value. In contrast, in Comparative Example 3 (PTDV), the flow angle near the shroud increases, but the hub increases. The flow angle in the vicinity remains negative. At this time, the negative flow angle means that the reverse flow of the flow occurs, and as shown in FIG. 11, when the reverse flow occurs, the effective area of the flow path inside the diffuser is reduced. On the other hand, Example 1 (PSDV) has a negative flow angle in the vicinity of the shroud at the inlet ( r / r ₂ =1.06), but changes to a positive value at r / r ₂ =1.23 and finally flows constant according to the span. Each distribution is shown. The flow angle distribution according to the change of r / r ₂ when Φ / Φ _d =1.8 is as shown in Fig. 13 (c). In the case of Comparative Example 2 (PHDV), the flow angle inside the flow path ( r / r ₂ =1.23, 1.40) compared to the flow angle at the inlet ( r / r ₂ =1.06) was significantly changed over the entire span region. In particular, it can be seen that the reduction was over 40° in the vicinity of the 30% span. On the other hand, in Comparative Example 3 (PTDV), the flow angle inside the flow passage shows a similar distribution when compared to the inlet flow angle, and in Example 1 (PSDV), the change in the flow angle around the shroud compared to other cases It can be seen that is relatively large.

14 shows the velocity distribution in each cross section according to the radial position when Φ / Φ _d =0.6. Comparative Example 2 (PHDV) shows a high velocity in the vicinity of the hub, Comparative Example 3 (PTDV) shows a high velocity distribution in the vicinity of the shroud, while Example 1 (PSDV) shows a lower velocity distribution than the previous two cases. . As described in FIG. 13(a), the effective area is reduced due to the development of reflux in the area without the diffuser vane (near the shroud in the case of Comparative Example 2 (PHDV) and in the hub in the case of Comparative Example 3 (PTDV)). Therefore, it means that the pressure is not sufficiently recovered by having a high flow velocity in the flow path near the vane, so the pressure recovery coefficient value of the diffuser in Example 1 (PSDV) of Φ / Φ _d = 0.6 is relatively higher than the other two cases. It is judged to be large (see Fig. 12(a)).

15 shows a three-dimensional iso-surface distribution with a pressure recovery coefficient of -1 in the diffuser region when Φ / Φ _d =1.8. In common, it can be seen that the low pressure distribution starting from the leading edge of the diffuser extends to the diffuser suction surface, the upper end, and the middle of the flow path. When comparing the relative size of the isosurface distribution, it can be seen that Comparative Example 3 (PTDV) has a relatively small size compared to the other two cases. This can be inferred due to the change in flow according to the diffuser inlet flow angle, the diffuser position and the incident angle (see FIG. 13(c)). In Comparative Example 3 (PTDV), the distribution of the flow angle at the inlet and the angle change according to the flow of the flow are not large. On the other hand, in the case of Comparative Example 2 (PHDV), it can be confirmed that the change of the sharp angle according to the flow compared to the inlet flow angle, which causes a rapid flow change due to the diffuser angle of the hub, which is relatively small compared to the inlet flow angle. It is because a large flow separation occurred, and as a result, as shown in FIG. 12(c), it was confirmed that the pressure recovery coefficient of the diffuser was low due to a decrease in local pressure recovery.

As such, the centrifugal pump provided in one aspect of the present invention includes a partial diffuser vane, has high efficiency in the vicinity of the design flow rate, and can recover static pressure in a wide flow range. In particular, a centrifugal pump including a partial diffuser vane in a specific arrangement can effectively delay the time point when the slope of the pressure recovery coefficient becomes positive.

It will be understood that the invention has been described above by way of example, and that the terms used are intended to be words for description rather than limitation. It is possible to variously modify and change the present invention in consideration of the above teachings. Therefore, it should be understood that within the scope of the appended claims, the present invention may be practiced other than specifically listed in the description.

1000: centrifugal pump
100: impeller
200: diffuser
210: shroud
211: Bain (shroud side)
220: hub
221: Bain (hub side)
300: incoming tube

Claims (4)

An impeller having a plurality of blades formed in a circumferential direction; And
It includes a plurality of diffusers formed extending from the impeller toward the gas outlet,
The at least one diffuser includes vanes located on the shroud side,
At least one diffuser is a centrifugal pump comprising a vane located on the hub side.
According to claim 1,
The plurality of diffusers,
A centrifugal pump, characterized in that a diffuser comprising vanes located on the shroud side and a diffuser comprising vanes located on the hub side are alternately positioned.
According to claim 1,
Centrifugal pump, characterized in that the vane located on the shroud side has a span height of 25% to 75%.
According to claim 1,
Centrifugal pump, characterized in that the vane located on the hub side has a span height of 25% to 75%.

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