A low-noise centrifugal pump and a pressure pulsation detection method

Abstract

This application relates to a low-noise centrifugal pump and a pressure pulsation detection method, belonging to the technical field of water pumps. It includes a pump body, and the pump body is provided with an impeller chamber and a water inlet chamber. The water inlet chamber includes a water inlet flow channel and a connecting flow channel, and the connecting flow channel is connected to the impeller chamber. The boundary of the connecting flow channel is curved. The water inlet chamber includes several cross-sections that are circular. Let the smallest circular cross-section be S1 and the largest circular cross-section be S2, where S2 ≥ S1 ≥ 0.9S2. This application has the advantage of being able to reduce noise.

Description

Technical Field

[0001] This application relates to the technical field of water pumps, and in particular to a low-noise centrifugal pump and a pressure pulsation detection method. Background Art

[0002] During the operation of a centrifugal pump, in addition to the noise generated by the motor during operation, noise will also be generated between the impeller and the pump body under the action of water flow. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, one of the purposes of this application is to provide a low-noise centrifugal pump and a pressure pulsation detection method, which have the advantage of being able to reduce noise.

[0004] The above object of this application is achieved through the following technical solutions:

[0005] A low-noise centrifugal pump includes a pump body. The pump body is provided with an impeller cavity and a water inlet cavity. The water inlet cavity includes a water inlet flow channel and a connecting flow channel. The connecting flow channel is connected to the impeller cavity. The boundary of the connecting flow channel is curved. The water inlet cavity includes a number of cross-sections that are circular. Let the smallest circular cross-section be S1 and the largest circular cross-section be S2, where S2≥S1≥0.9S2.

[0006] By adopting the above technical solution, the water inlet cavity better conforms to the flow path of water entering the impeller, and the area transition is uniform. Therefore, the probability of forming turbulent flow can be reduced, the probability of forming inlet bubbles can be reduced, and thus the noise can be reduced.

[0007] In a preferred example of this application, it can be further configured that: the connecting flow channel includes an inlet, the impeller includes a water inlet, and the inlet is used to communicate with the water inlet. Let the diameter of the inlet be d1 and the diameter of the water inlet be d2, where 44mm≤d1≤72mm and 1.05d1≤d2≤1.1d1.

[0008] By adopting the above technical solution, the increase in the inlet enables sufficient water intake and reduces cavitation.

[0009] In a preferred example of this application, it can be further configured that: there is also a cut-off tongue in the pump body, and the gap between the impeller and the cut-off tongue is X*d2, where 1.15≥X≥1.03.

[0010] By adopting the above technical solution, the impact of water on the cut-off tongue is reduced, and the probability of cavitation and the generation of cavitation caused by the impact can be reduced.

[0011] The present application also discloses a method for detecting pressure pulsation of a low-noise centrifugal pump: applied to any one of the above-mentioned low-noise centrifugal pumps, including the following steps: setting 6 pressure monitoring points, namely Point_1 - Point_6, where Point_1 - Point_3 are on the impeller and Point_4 - Point_6 are on the volute. The monitoring points on the impeller are located at the outlet of the outer edge blades of the impeller. For the monitoring points on the volute, one is placed at the tongue, and the other two are evenly distributed on the base circle gradually away from the tongue; performing transient simulation with a time step of 2.57 degrees.

[0012] By adopting the above technical solution, the pressure data of each point can be obtained through simulation.

[0013] In a preferred example of the present application, it can be further configured that: the simulation is calculated for a total of 8 circles.

[0014] In a preferred example of the present application, it can be further configured that: after obtaining the pressure data, to facilitate observing the pressure pulsation characteristics and comparing the pressure pulsation conditions of different positions and different monitoring points, the pressure data is made dimensionless and transformed into a pressure pulsation coefficient Cp. The calculation method of Cp is as follows: Cp = ΔP / [(0.5ρ(u 2 )²], where ΔP is the difference between the pressure value and the global pressure value, in Pa, ρ represents the medium density, in kg / m 3 , U 2 is the circumferential velocity at the outlet of the outer edge of the impeller, in rpm, and the calculation formula is: U 2 = πn(D 2 ) / 60, where n is the rotational speed, in rpm.

[0015] By adopting the above technical solution, the pressure pulsation characteristics can be obtained. Description of the Drawings

[0016] Figure 1 is a schematic diagram of the water inlet cavity structure of the present application.

[0017] Figure 2 is a schematic diagram of the positions of the pressure monitoring points of the present application.

[0018] Figure 3 is a data graph of the same monitoring points under the rated flow of the present application.

[0019] Figure 4 is a data graph of the same monitoring points under 1.5 times the rated flow of the present application.

[0020] Figure 5 is a frequency-amplitude curve graph of the pressure pulsation at the original hydraulic rated flow of the present application.

[0021] Figure 6It is the frequency - amplitude curve graph of the pressure pulsation of the optimized hydraulic rated flow rate of this application.

[0022] Figure 7 It is the frequency - amplitude curve graph of the pressure pulsation of 1.5 times the original hydraulic rated flow rate of this application.

[0023] Figure 8 It is the frequency - amplitude curve graph of the pressure pulsation of 1.5 times the optimized hydraulic rated flow rate of this application.

[0024] Reference numerals: 1, pump body; 2, water inlet chamber; 21, water inlet flow channel; 22, connecting flow channel; 3, inlet. Detailed implementation manners

[0025] The following further details this application with reference to the accompanying drawings.

[0026] Refer to Figure 1 - Figure 8 , a low - noise centrifugal pump disclosed in this application, includes a pump body 1 and an impeller. The pump body 1 is provided with an impeller chamber and a water inlet chamber 2. The water inlet chamber 2 includes a water inlet flow channel 21 and a connecting flow channel 22. The connecting flow channel 22 is connected to the impeller chamber. The boundary of the connecting flow channel 22 is curved. The water inlet chamber 2 includes a number of cross - sections that are circular. Let the smallest circular cross - section be S1 and the largest circular cross - section be S2, where S2≥S1≥0.9S2. The connecting flow channel 22 includes an inlet 3. The impeller includes a water inlet. The inlet 3 is used to communicate with the water inlet. Let the diameter of the inlet 3 be d1 and the diameter of the water inlet of the impeller be d2, where 44mm≤d1≤72mm and 1.05d1≤d2≤1.1d1. A cut - off tongue is also provided in the pump body 1. The gap between the impeller and the cut - off tongue is X * d2, where 1.15≥X≥1.03. The impeller is a 7 - blade impeller.

[0027] The parameter comparison before and after the improvement is shown in the following table:

[0028] Improvement item Original hydraulics After optimization Inlet diameter (mm) 45 72 Clearance between impeller and tongue (mm) 8.6 13 Number of blades 6 7 Throat area (mm2) 1441 2550 Inlet pipe With steps Fully smooth Volute type Rectangular with rounded corners Circular with side flat

[0029] This application also discloses a method for detecting the pressure pulsation of a low - noise centrifugal pump, which is applied to the above - mentioned low - noise centrifugal pump and includes the following steps: Set 6 pressure monitoring points, namely Point_1 - Point_6. Point_1 - Point_3 are on the impeller, and Point_4 - Point_6 are on the volute. The monitoring points on the impeller are located at the outer edge of the impeller blade outlet. Among the monitoring points on the volute, one is placed at the cut - off tongue, and the other two are evenly distributed on the base circle gradually away from the cut - off tongue; Conduct transient simulation with a time step of 2.57 degrees, and the simulation calculates a total of 8 laps.

[0030] After obtaining the pressure data, to facilitate the observation of the pressure pulsation characteristics and the comparison of the pressure pulsation conditions at different positions and different monitoring points, the pressure data is made dimensionless and transformed into the pressure pulsation coefficient Cp. The calculation method of Cp is as follows: Cp = ΔP / [(0.5ρ(u 2 )²], where ΔP is the difference between the pressure value and the global pressure value, with the unit of Pa, ρ represents the medium density, with the unit of kg / m 3 , U 2 is the circumferential velocity at the outer edge of the impeller outlet, with the unit of rpm. The calculation formula is: U 2 = πn(D 2 ) / 60, where n is the rotational speed, with the unit of rpm.

[0031] After data processing, the Cp time-domain diagrams of 6 monitoring points are obtained. See Figure 3 . The data of the same monitoring points of the original hydraulics and the optimized hydraulics under the rated flow rate are put together for comparison.

[0032] It can be concluded that except for Point_1 near the tongue separation, where the pressure pulsation amplitudes of the monitoring points on the impeller are hydraulically similar before and after optimization, the amplitudes of the optimized hydraulics at other monitoring points are smaller than those before optimization; at Point_4 on the tongue separation, the optimized hydraulics is higher than the original hydraulics, and the optimized hydraulics at the other two points is better than the original hydraulics, especially at Point_6 with obvious advantages. Generally speaking, compared with the original hydraulics, the pressure pulsation intensity of the optimized hydraulics has been generally improved.

[0033] See Figure 4 . The data of the same monitoring points of the original hydraulics and the optimized hydraulics under the 1.5-fold rated flow rate condition are put together for comparison.

[0034] It can be concluded that except that the optimized hydraulics and the original hydraulics are similar at Point_5, the optimized hydraulics is comprehensively better than the original hydraulics. Under the large flow rate condition, the pressure pulsation characteristics of the optimized hydraulics are significantly better than those of the original hydraulics. Combining with the rated situation, it can be predicted that the noise excited by the pressure pulsation of the optimized hydraulics will be less than that of the original hydraulics.

[0035] To comprehensively analyze the characteristics of the pressure pulsation, the above pressure pulsation time-domain distribution is transformed into the frequency-domain distribution through the fast Fourier transform. The frequency-amplitude curve of the pressure pulsation at the rated point is shown in Figure 5 and Figure 6。The pump operates at a rotational speed of 2750 RPM, with a shaft frequency of 45.8 Hz. The original hydraulics has a 6 - blade impeller, and the impeller passing frequency is 275 Hz. After optimization, the hydraulics has a 7 - blade impeller, and the impeller passing frequency is 320 Hz. As shown in the figure, the spectral distributions of the original hydraulics and the optimized hydraulics at the rated point have commonalities. The main frequency of the impeller is close to the shaft frequency, with the largest amplitude, and multiple low - frequency harmonics also have relatively large amplitudes. The main frequency in the volute is the blade frequency, but the amplitude is significantly smaller than that in the impeller. Higher blade - frequency multiples are also distributed, and the amplitude gradually decreases with increasing frequency. The main difference is that the number of low - frequency harmonic peaks in the optimized - hydraulics impeller is less. Relatively speaking, except for larger amplitudes at 1 - 4 times the shaft frequency, the amplitudes at other frequencies are smaller and basically disappear after 700 Hz. The original - hydraulics impeller has more harmonics distributed within 1200 Hz, which means that the inner wall of the impeller emits pressure waves of multiple frequencies, increasing the risk of induced resonance.

[0036] See Figure 7 and Figure 8 , which is the frequency - amplitude curve of the pressure pulsation at 1.5 times the rated - point operating condition. The overall distribution characteristics are similar to those at the rated point, but the amplitude is significantly reduced. The number of harmonic peaks of the impeller before and after optimization both decreases, but the original hydraulics still has a wider frequency distribution, although the amplitude is slightly smaller than that of the optimized hydraulics. In addition, at large flow rates, the main frequency at the monitoring point Point_6 in the volute changes from the single - blade frequency to the double - blade frequency. Based on the above - mentioned time - domain and frequency - domain analysis of the pressure pulsation, it can be predicted that the noise excited by the pressure pulsation of the optimized hydraulics will be less than that of the original hydraulics.

[0037] After predicting the net positive suction head and analyzing the pressure pulsation, it is comprehensively judged that the optimized hydraulics is better than the original hydraulics. The noise test results are as follows: According to the inspection report, for the original hydraulics, during the pressurized test at the rated 20 cubic meters, the noise is 55.1 dB, and when fully open, the noise is 72.9 dB; for the optimized hydraulics, during the pressurized test at the rated 20 cubic meters, the noise is 53.8 dB, a decrease of 2% (1.3 dB), and when fully open, the noise is 54.3 dB, a decrease of 25.5% (18.6 dB).

[0038] The implementation principle of this embodiment is: By optimizing the internal flow path of the pump body, the noise generated during operation is greatly reduced.

[0039] The embodiments of this specific implementation manner are all preferred embodiments of this application. It does not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A low noise centrifugal pump, characterized in that: The invention comprises a pump body (1), wherein the pump body (1) is provided with an impeller chamber and a water inlet chamber (2), wherein the water inlet chamber (2) comprises a water inlet channel (21) and a connecting channel (22), wherein the connecting channel (22) is connected to the impeller chamber, wherein the boundary of the connecting channel (22) is curved, wherein the water inlet chamber (2) comprises a plurality of sections with circular cross sections, wherein the area of ​​the smallest circular cross section is S1, and the area of ​​the largest circular cross section is S2, wherein S2≥S1≥0.9S2; wherein the connecting channel (22) comprises an inlet (3), wherein the impeller comprises a water inlet, wherein the inlet (3) is connected to the water inlet, wherein the diameter of the inlet (3) is d1, and the diameter of the water inlet is d2, wherein 44mm≤d1≤72mm, and 1.05d1≤d2≤1.1d1; wherein a baffle tongue is further provided in the pump body (1), wherein the gap between the impeller and the baffle tongue is X*d2, and 1.15≥X≥1.

03.

2. A method for detecting pressure pulsation of a low-noise centrifugal pump, characterized in that: A low-noise centrifugal pump applied to claim 1 comprises the following steps: setting 6 pressure monitoring points, namely Point_1-Point_6, Point_1-Point_3 on the impeller, Point_4-Point_6 on the volute, the monitoring point on the impeller is located at the outlet of the blades on the outer edge of the impeller, and the monitoring point on the volute is placed at the tongue, and the other two are gradually away from the tongue and evenly distributed on the base circle; transient simulation is performed with a time step of 2.57 degrees.

3. A low noise centrifugal pump pressure pulsation detection method according to claim 2, characterized in that: The simulation is performed for 8 cycles in total.

4. A low noise centrifugal pump pressure pulsation detection method according to claim 2, characterized in that: After obtaining the pressure data, in order to facilitate the observation of pressure pulsation characteristics and compare the pressure pulsation conditions at different locations and different monitoring points, the pressure data is converted dimensionlessly into the pressure pulsation coefficient Cp. The calculation method of Cp is as follows: Cp=ΔP / [(0.5ρ(u2)²], where ΔP is the difference between the pressure value and the global pressure value, in units of Pa, and ρ represents the medium density, in units of kg / m 3 , u2 is the circumferential speed of the impeller outer edge outlet, unit rpm, and the calculation formula is: u2=πn(d2) / 60, where n is the rotation speed, unit rpm.

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