Low-noise centrifugal pump and pressure pulsation detection method

Abstract

The invention relates to a low-noise centrifugal pump and a pressure pulsation detection method, and relates to the technical field of water pumps, the low-noise centrifugal pump comprises a pump body, the pump body is provided with an impeller cavity and a water inlet cavity, the water inlet cavity comprises a water inlet flow channel and a communicating flow channel, the communicating flow channel communicates with the impeller cavity, and the boundary of the communicating flow channel is in a curve shape; the water inlet cavity comprises a plurality of circular sections, the minimum circular section is set as S1, the maximum circular section is set as S2, and S1 is larger than or equal to 0.9 S2 and larger than or equal to S2. The air conditioner has the advantage of being capable of reducing noise.

Description

Technical Field

[0001] The present 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] When a centrifugal pump is in operation, in addition to the noise caused by the motor, noise is also generated between the impeller and the pump body due to the action of water flow. Summary of the invention

[0003] In view of the deficiencies in the prior art, one of the purposes of the present 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-mentioned purpose of the present application is achieved through the following technical solutions: A low-noise centrifugal pump comprises a pump body, wherein the pump body is provided with an impeller chamber and a water inlet chamber, the water inlet chamber comprises a water inlet flow channel and a connecting flow channel, the connecting flow channel is connected to the impeller chamber, the boundary of the connecting flow channel is curved, the water inlet chamber comprises a plurality of sections with circular cross sections, the smallest circular cross section is S1, the largest circular cross section is S2, S2≥S1≥0.9S2.

[0005] By adopting the above technical solution, the water inlet chamber is more consistent with the flow path of water entering the impeller, and the area transition is uniform, thereby reducing the probability of turbulence formation and the probability of inlet bubble formation, thereby reducing noise.

[0006] In a preferred example, the present application can be further configured as follows: the connecting flow channel includes an inlet, the impeller includes a water inlet, the inlet is used to communicate with the water inlet, the diameter of the inlet is d1, the diameter of the water inlet is d2, 44mm≤d1≤72mm, 1.05d1≤d2≤1.1d1.

[0007] By adopting the above technical solution, the inlet is enlarged so that sufficient water intake can be ensured and cavitation can be reduced.

[0008] In a preferred example, the present application can be further configured as follows: a baffle tongue is also provided in the pump body, and the gap between the impeller and the baffle tongue is X*d2, 1.15≥X≥1.03.

[0009] By adopting the above technical solution, the impact of water on the baffle is reduced, and the probability of cavitation caused by the impact is reduced.

[0010] The present application also discloses a method for detecting pressure pulsation of a low-noise centrifugal pump: applied to a low-noise centrifugal pump described in any one of the above, comprising 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, one is placed at the baffle, and the other two are gradually away from the baffle and evenly distributed on the base circle; transient simulation is performed with a time step of 2.57 degrees.

[0011] By adopting the above technical solution, the pressure data of each point can be obtained through simulation.

[0012] In a preferred example, the present application can be further configured as follows: a total of 8 simulation cycles are calculated.

[0013] In a preferred example, the present application can be further configured as follows: After obtaining the pressure data, in order to facilitate the observation of the pressure pulsation characteristics and the comparison of the pressure pulsation conditions at different locations and different monitoring points, the pressure data is dimensionlessly converted into a 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.

[0014] By adopting the above technical solution, pressure pulsation characteristics can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the water inlet chamber structure of this application.

[0016] Figure 2 It is a schematic diagram of the locations of pressure monitoring points in this application.

[0017] Figure 3 This is the data chart of the same monitoring point under the rated flow of this application.

[0018] Figure 4 This is the data chart of the same monitoring point at 1.5 times the rated flow rate of this application.

[0019] Figure 5 It is a frequency-amplitude curve diagram of the original hydraulic rated flow pressure pulsation of this application.

[0020] Figure 6 It is a frequency-amplitude curve diagram of the hydraulic rated flow pressure pulsation after optimization of this application.

[0021] Figure 7It is the frequency-amplitude curve of the original hydraulic pressure pulsation of 1.5 times the rated flow rate of this application.

[0022] Figure 8 It is a frequency-amplitude curve of hydraulic pressure pulsation at 1.5 times rated flow after optimization in this application.

[0023] Reference numerals: 1, pump body; 2, water inlet chamber; 21, water inlet channel; 22, connecting channel; 3, inlet. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with the accompanying drawings.

[0025] Reference Figure 1-Figure 8 , is a low-noise centrifugal pump disclosed in the present application, comprising a pump body 1 and an impeller, 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, and the water inlet chamber 2 comprises a plurality of sections with circular cross sections, wherein the smallest circular cross section is S1, and the largest circular cross section is S2, wherein S2≥S1≥0.9S2. The connecting channel 22 comprises an inlet 3, wherein the impeller comprises an inlet, wherein the inlet 3 is used to be connected to the inlet, wherein the diameter of the inlet 3 is d1, and the diameter of the inlet is d2, wherein 44mm≤d1≤72mm, and 1.05d1≤d2≤1.1d1. A baffle is also provided in the pump body 1, wherein the gap between the impeller and the baffle is X*d2, wherein 1.15≥X≥1.03, and the impeller is a 7-blade impeller.

[0026] The comparison of parameters before and after improvement is shown in the following table: Improvements Original hydraulic power After optimization Inlet diameter (mm) 45 72 Impeller and tongue clearance (mm) 8.6 13 Number of blades 6 7 Throat area (mm2) 1441 2550 Import pipe There are steps Fully smooth Snail form Rectangle rounded corners Round side flat The present application also discloses a method for detecting pressure pulsation of a low-noise centrifugal pump, which is applied to the above-mentioned low-noise centrifugal pump, and includes 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, one is placed at the baffle, and the other two are gradually away from the baffle and evenly distributed on the base circle; transient simulation is performed with a time step of 2.57 degrees, and the simulation is calculated for a total of 8 cycles.

[0027] 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.

[0028] After data processing, the Cp time domain diagram of the six monitoring points is obtained, see Figure 3 , the original hydraulic pressure and optimized hydraulic pressure data at the same monitoring point at rated flow are compared together.

[0029] It can be concluded that, except for Point_1 near the baffle, the hydraulics before and after optimization are similar, the hydraulics of other monitoring points after optimization are smaller than before optimization; at Point_4 on the baffle, the hydraulics after optimization are higher than the original hydraulics, and the hydraulics of the other two points after optimization are better than the original hydraulics, especially Point_6. In general, the pressure pulsation intensity of the optimized hydraulics is improved compared with the original hydraulics.

[0030] See also Figure 4 The original hydraulic pressure and optimized hydraulic pressure data at the same monitoring point under the condition of 1.5 times the rated flow rate are compared together.

[0031] It can be concluded that, except for Point_5 where the hydraulic power after optimization is similar to the original hydraulic power, the hydraulic power after optimization is superior to the original hydraulic power in all aspects. Under large flow conditions, the hydraulic pressure pulsation characteristics after optimization are significantly better than the original hydraulic power. Combined with the rated conditions, it can be predicted that the noise of the hydraulic pressure pulsation excitation after optimization will be smaller than that of the original hydraulic power.

[0032] In order to fully analyze the characteristics of pressure pulsation, the above pressure pulsation time domain distribution is transformed into frequency domain distribution through fast Fourier transform. The frequency-amplitude curve of the rated point pressure pulsation can be found in Figure 5 and Figure 6 . The pump runs at 2750RPM, the shaft frequency is 45.8Hz, the original hydraulic power is a 6-blade impeller, the impeller passing frequency is 275Hz, the optimized hydraulic power is a 7-blade impeller, and the impeller passing frequency is 320Hz. As shown in the figure, the original hydraulic power and the optimized hydraulic power have something in common in the frequency spectrum distribution at the rated point. The main frequency of the impeller is close to the shaft frequency, the amplitude is the largest, and multiple low-frequency harmonics have 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 harmonics are also distributed and the amplitude gradually decreases with the increase of frequency. The main difference is that the number of low-frequency harmonic peaks in the optimized hydraulic impeller is less, and in comparison, except for 1-4 times the shaft frequency with a large amplitude, the amplitude of other frequencies is small and basically not distributed after 700Hz. The original hydraulic impeller has more frequency harmonics distributed within 1200, which means that the inner wall of the impeller emits pressure waves of multiple frequencies outward, which will increase the risk of induced resonance.

[0033] See also Figure 7 and Figure 8, which is the frequency-amplitude curve of the pressure pulsation at 1.5 times the rated point. The overall distribution characteristics are similar to the rated point, but the amplitude is significantly reduced. The number of harmonic peaks of the impellers before and after optimization has decreased, but the original hydraulic still has a wider frequency distribution but the amplitude is slightly smaller than the optimized hydraulic. In addition, under large flow, the main frequency of the Point_6 monitoring point in the volute changes from single blade frequency to double blade frequency. Combining the above analysis of pressure pulsation in time domain and frequency domain, it can be predicted that the noise of the hydraulic after optimization excited by pressure pulsation will be smaller than the original hydraulic.

[0034] After completing the NPSH prediction and pressure pulsation analysis, it is comprehensively judged that the optimized hydraulics will be better than the original hydraulics. The noise test results are as follows: According to the inspection report, the pressure test is rated at 20 cubic meters, the noise is 55.1dB, and when fully open, the noise is 72.9dB; after optimization, the pressure test is rated at 20 cubic meters, the noise is 53.8dB, a decrease of 2% (1.3dB), and when fully open, the noise is 54.3dB, a decrease of 25.5% (18.6dB).

[0035] The implementation principle of this embodiment is: by optimizing the internal flow channel of the pump body, the noise generated during operation is greatly reduced.

[0036] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present 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 in a curved shape, and the water inlet chamber (2) comprises a plurality of sections with circular cross sections, wherein the smallest circular cross section is S1, and the largest circular cross section is S2, and S2≥S1≥0.9S2.

2. A low noise centrifugal pump according to claim 1, characterized in that: The communicating flow channel (22) includes an inlet (3), the impeller includes a water inlet, the inlet (3) is used to communicate with the water inlet, the diameter of the inlet (3) is d1, the diameter of the water inlet is d2, 44mm≤d1≤72mm, 1.05d1≤d2≤1.1d1.

3. A low noise centrifugal pump according to claim 1, characterized in that: A partition tongue is also provided in the pump body (1), and the clearance between the impeller and the partition tongue is X*d2, 1.15≥X≥1.

03.

4. A method for detecting pressure pulsation of a low-noise centrifugal pump, characterized in that: A low-noise centrifugal pump applied to any one of claims 1 to 3, comprising 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 baffle tongue, and the other two are gradually away from the baffle tongue and evenly distributed on the base circle; transient simulation is performed with 2.57 degrees as a time step.

5. A low noise centrifugal pump pressure pulsation detection method according to claim 4, characterized in that: The simulation is performed for 8 cycles in total.

6. A low noise centrifugal pump pressure pulsation detection method according to claim 4, 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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