SU1384828A1 - Method of testing stage of multistage centrifugal pump - Google Patents

Description

with Eo

X)

SD X)

The invention relates to hydraulic engineering, more specifically to the balance tests of centrifugal pumps.

The purpose of the invention is to increase the accuracy of testing in all modes of pump operation by specifying experimentally determined internal mechanical losses.

The bog wheel 1 of its layout 39 and the insert 40. In addition, the annular grooves 3 and 4 with o-rings 41 and 42 are shown on the lower part (Fig. 2).

On fig.Z shows the test stage with the installation of the impeller 1. The upper part of the corresponding

Figure 1 shows the block experiment Q in the position when the front sub-pump with the stage being tested; FIG. 2 is a diagram of a stage to be graded, equipped with an impeller mockup; on fig.Z - tested

the stage of the device, equipped with a staff of the 15 of the impeller 1 is installed disney impeller with ensuring zero costs in its sinuses; Fig. 4 is a schematic of the stage being tested, allowing to isolate the losses of idling; figure 5 - scheme of the test bench; Fig. 6 is a diagram illustrating a method for allocating the power of disk friction in the anterior sinus.

The experimental pump unit (Fig. 1) includes an impeller 1, mounted on shaft 2, front and rear collars 3 and 4 of the housing, forming respectively the front and rear sinuses 5 and 6 stages, sealed with front and interstage gap seals 7 and 8, paddle branch 9. The block contains an additional branch 10 at the inlet and a confused supply line P. At the exit of the block, a branch 12 is installed. At the entrance to the block, the shaft 2 is sealed by the sealing unit 13. The wheel 1 is fixed by means of a nut 14. To measure the pressure of the stage in the upper section 3 and 15, a series of receiving openings 16 and 17 are connected by means of leveling annular cavities 18 and 19 to pressure extraction channels 20 and 21. Crush 3 is provided with two rows of openings 22 and 23 placed circumferentially at the inlet and outlet of the front gap seal 7 and provided with leveling annular chambers 24 and 25 communicated with pressure receiving channels 26 and 27. Similarly, the cap 4 is provided with rows of holes 28 and 29 at the inlet and outlet of the interstage seal 8, chambers 30 and 31, and channels 32 and 33. Rows of holes are provided in the covers 3 and 4 for measuring the static pressures at the exit and wheel 1 34 and 35, annular chambers 36 and 37, and extraction channels 38. The difference between the devices (Fig. 2) is the installation instead of Rach 5 is sealed with a ring 4 of circular cross section, and the lower one - with the position when the Rh 42 of the back sinus 6 is sealed. On the shaft 2 (Fig 4) there is a separate sleeve 43. Stand It consists of an experimental unit 44, a bearing assembly 45, a balancing electric motor 46 and a tank 47.

0 The latter is communicated with block 44 by an inlet pipe 48 with a valve 49 and a manacacon 50 and a discharge pipe 51 with a valve 52, a flow meter 53 and a meter 54. The block 44 is provided with inlets. hydraulic lines 55 and 56 from an auxiliary pressure source (not shown). At the same time, the hydrolines 55 are brought to the outlet 12, and 56 - to the supply pipe 48 between the valve 49 and the block 44.

Manometers 57 and 58 are intended for measuring pressure drops in front and interstage seals 7 and 8. Manometer 59 is used to measure the averaged static pressure at the exit of the impeller 1 and connected to channels 38. Pressure gauges are used to measure the pressure at the inlet and outlet of the test stage. 60 and 61, connected respectively to channels 0 and 21. Leakage through the sealing unit is measured using a tank 62, the number of revolutions — a tachometer 63. The hydroline 55 is equipped with a flow meter 64.

In Figure 6, the following notation is accepted: A — pressure curve in the presence of leaks g, n, f (Q) i B — pressure curve in the absence of leaks; B - pressure curve obtained from curve A by adding leaks n, f (Q +. G,); G - power curve in the presence of leaks g ,; D - power curve in the absence of leaks.

The test method of the multistage centrifugal pump stage includes the measurement of flow, head and power at the pump shaft with a standard 5

0

five

0

five

with the impeller, as well as with the mockup of the impeller when supplying fluid from an auxiliary pressure source and determining energy performance and volume and disk losses in the anterior and posterior sinuses of the stage. Testing a stage with an impeller mockup is carried out at zero fluid flow through the stage sinuses, and before determining the energy indices, an additional step with a standard impeller is carried out at zero fluid flow alternately through the back and front sinuses.

The proposed method is implemented in the device as follows.

First, a special experiment is carried out to determine the leakage g through the front seal 7 and g through the seal B when installing the impeller layout 39 (Fig. 2). In this case, the insert 40 is sealed between the cavity of the stage and the guide vane. In this form, the pump is rotated using a balance motor 46. The frequency of rotation must correspond to the frequency during balance tests. Next, an auxiliary pressure source (not shown) is turned on, and through hydroline 55 (Fig. 5), through outlet 12, fluid is supplied to the pump. From outlet 12, it enters the interstage seal 8, passes through the posterior sinus 6, through the gap between the surface of the wheel on the outer diameter and the insert 40, through the anterior sinus 5, the forward slit seal

7, additional tap 10 and pipeline 48 to tank 47. By adjusting the pressure in hydroline 54, the flow rate and the differences P, and LP are changed, on seals 7 and 8. At the same time, the flow rate is measured using flow meter 64, and the differences ftP, and & P - gauges 57 and 58. As a result, the dependences g, fi (ЛР,) and

gj fz (uP2) -

After performing the described operation, without shutting down the entire installation from operation, all the hydraulic lines connected to the internal cavity of block 44, in particular pipeline 48, are hermetically interrupted using a valve 49. Using a balancing electric motor 16, the power consumption of the pump is determined. In this way, the disc losses in the test stage are identified, but at the same time they provide zero flow through its internal cavity, and hence through the sinuses 5 and 6 and seals 7 and 8.

Next, the result obtained, Nf, is corrected by subtracting from it the power determined by calculating N, spent on the friction of the additional surfaces resulting from the closing at the entrance and exit of the wheel. In addition, its idle power consumed for friction is determined in the bearing assembly 45, seal 13. For determination, reassembly of block 44 is performed, and sleeve 43 is installed instead of layout 39 (figure 4). In this position, the shaft is rotated when the block 44 is filled with water (from the tank 47). The power N consumed in this case is greater than the value N 1 1 of the loss of the disk friction on the shaft sections within the limits of the length of the step L. (Figure 4). The value of N-1 is determined by calculation. Thus, the power of disc friction in stagnant water is defined as

N

boyfriend

- Nnap.n kou xx

Where

NXX NX - NjE.

After that, the next stage of testing is performed. To do this, in block 44, a staff impeller 1 is mounted directly on shaft 2. When performing tests, hydraulic lines 55 and 36 must be closed and valve 49 is open. During testing, the fluid from tank 47 through line 48 enters unit 44, where it receives an increment of energy in wheel 1. Then, via outlet 12 and pipe 51, it again enters tank 47. Pump flow is controlled by valve 52 and measured by flow meter device 53. The head of the stage being tested is measured with a mana. gauge 50 and pressure gauge 61, and in general, the pressure head of the block — using a pressure gauge 50 and pressure gauge 54. The power consumption Hc p is determined using a balancer motor 46. In the process of determining the operating characteristics of the stage and block 44 in each mode of operation under investigation The pressure at the outlet of the wheel 1 mano51384S28

meter 59 and at the same time fix the РP drops, and LР on seals 7 and 8 with the help of manometers 57 and 58, which makes it possible to determine leaks in

ki g and g through the latter using the dependences g f, (uP,) and gj g, (uP), obtained in the first stage.

In order to carry out further stages of testing, two new assemblies of unit 44J are carried out, as a result of which the alternately tested stage is supplemented with sealing rings 42 and 41 installed in the grooves of covers 3 and 4 in the sealing area 7 and B (Fig. 3).

By installing a ring 42 that prevents fluid from flowing

through a slotted seal 8, providing with the help of an auxiliary pressure source via a hydroline 56. At the same time, on the other side of the seal, i.e. through the outlet 12, by means of the hydroline 55, the pressure is also maintained so that a pressure differential is created on the ring 42 (The insert 40 is also restored and the valve 49 is hermetically sealed). Starting up in such a position, block 44 and creating the corresponding values of P, determine the power consumed at this time, N then it (& P z)

The difference between the latter and Np „p„ const and gives the value uNu (iPj). Similarly, the value of

There is zero fluid flow in the posterior sinus 6 (i.e. g O; g t O). In this position, the installation is put into operation and the full measurement cycle is completed. At the same time, the pressure drops at the front and interstage seals 7 and 8 are measured. The values of the latter are indicated by UP ,. Others with the same feed rate will be the values of the power consumption Q The experimentally obtained difference between Nj and Njn is expressed in terms of its individual components as follows:

N ....

where l n ,,

- N

sn

 bN,

,, - ANeoci l) 35

40

,

u N goc,

45

changes in power losses due to disk friction due to the elimination of leakage in the posterior sinus from the axis to the periphery; power loss due to friction in seal assembly 42; the recovered part of the disk friction capacity (corresponding to the increase in the head due to its recovery). Similarly to the previous one, by installing the ring 41, a zero fluid flow in the anterior sinus 5 (g, 0; g O) is ensured. In this position, the installation is put into operation again and the full measurement cycle is performed. At the same time, the pressure drops uPj at the front and D P at 55 inter-step seals are measured. The experimentally obtained difference between the power consumed Hn and Yn

UN N

. P

(rr (), finding the difference between

(upf) and M „„

 const. For

par. nn tn Par. In this case, tests are carried out with the creation of a differential also using hydro50

These are pressure rings 41, U P, lines 55 and 56, and additional pressure sources.

In the process of testing the impeller 39 (figure 2) with the exception of flow through (flow) through the step and the sinuses 5 and 6, get the value of disk loss "ar n sinuses 5 and 6 with zero consumption in them. This value practically does not depend on the mode of operation of the pump and is therefore accepted for the entire operating characteristic of the pump constant. Further, by providing a zero leakage directly in a real pump in one of the sinuses 5 or 6, the working conditions and losses in them are brought to those that occur in it when the impeller 39 is rotated. If you now determine the actual power consumption

to express

through

her

structure

- N

np

& N ly

(2)

Pp p j

where uN is the change in the power consumed by the wheel, due to the elimination of leakage g, through the front sinus; Unftn friction power loss in the seal assembly 41,

In order to determine the components and components of Nun, n included in (1) and (2), reassembly of block 44 is again performed. At the same time, layout 39 is re-installed and special tests are carried out with alternating installation of rings 41 and 42 .

When testing with the installation of the ring 42 in the cavity of the stage, serves doNUN N

. P

(rr (), finding the difference between

(upf) and M „„

 const. For

par. nn tn Par. THIS is tested with the installation

five

five

and creating a differential also using hydro0

These are pressure rings 41, U P, lines 55 and 56, and additional pressure sources.

In the process of testing the impeller 39 (figure 2) with the exception of flow through (flow) through the step and the sinuses 5 and 6, get the value of disk loss "ar n sinuses 5 and 6 with zero consumption in them. This value practically does not depend on the mode of operation of the pump and is therefore accepted for the entire operating characteristic of the pump constant. Further, by providing a zero leakage directly in a real pump in one of the sinuses 5 or 6, the working conditions and losses in them are brought to those that occur in it when the impeller 39 is rotated. If you now determine the actual power consumption step N during normal operation and N „and N

P

n when the sinuses are sealed (alternately anterior 5 and posterior 6), then in accordance with (1) and (2) they allow to determine the values of bN HiNn, which must then be folded algebraically with

N

to get full magnitude ar. n

at DISK losses in the stage (depending on the flow rate),

those.

N

Z.TR Nnnp.M + N + DY,

(3)

The efficiency of the wheel due to an increase in the actual head by a magnitude of 15 L Hg n is determined directly using the experimental data in accordance with Fig.6. To get the value of LDL you need

where y is the specific gravity of the fluid; g g- Efficiency of the Sewage in the area between the impeller and the installation site of the pressure gauge 54 (determined by test results using the readings of the pressure gauges 59 and 54 and the calculation of averaging the difference between the values of the direct speeds in the pressure take-off sections) depending on Q.

steps obtained in the experiment with g, O, and those obtained during normal trials. In this case, the pressure characteristic obtained in the second case is corrected by adding its leakage g (H) to the pump Q flow, which is explained using the graphs in Fig. 6.

Restoration of a small part of the disk friction power leads to an increase in the pressure of a step of 20 g If 32 JJ g /

J 3631311 5 1 S Out.f

The proposed method before the cause of LN ,. J This value can be determined experimentally by directly determining the difference between the pressure characteristics obtained during normal tests and in the experiment O.

Determining the value of YN find value

DNv.z Q Q

ise

U n

LOS-e

; ore

where y is the specific gravity of the fluid; g g- Efficiency of the Squirt between the impeller and the installation site of the pressure gauge 54 (determined by test results using the readings of the pressure gauges 59 and 54 and the calculation of the average velocities in the cross sections of pressure take-offs) depending on Q

Having the last dependency and N value, find the hydraulic power

N. N.

- (N

 R

+ N, J

Next, the theoretical head, the braking power N, the efficiency of the wheel and the steps, etc., are calculated. As a result, a complete balance is made for the power supplied to the pump shaft.

CA 39

FIG. 2

Jfig ff

Fi.Z

L

g

/

i-cm /

L

/

 7 7

5B5S 752S153nri

YY 60 57 5BS2

FI.5

Claims (1)

METHOD OF TESTING THE STEP OF A MULTI-STAGE CENTRIFUGAL PUMP, including measuring the flow, pressure and power on the pump shaft with a standard impeller, as well as with a model of the impeller when supplying fluid from an auxiliary pressure source and determining energy indicators and volume and disk losses in the front and rear sinuses stages, characterized in that, in order to increase the accuracy of tests at all pump operating modes by specifying experimentally allocated internal mechanical losses, penalties with the impeller mock-up are carried out at zero fluid flow through the sinuses of the stage, and before determining the energy indicators, the steps are additionally tested with a standard impeller at zero fluid flow alternately through the rear and front sinuses of the stage. 1384828 A