Showing papers by "Bo Gao published in 2015"

Vibration Characteristics Induced by Cavitation in a Centrifugal Pump with Slope Volute

Abstract: Cavitation is one of the instability sources in centrifugal pump, which would cause some unexpected results. The goal of this paper was to analyze the influence of cavitation process on different frequency bands in a centrifugal pump with slope volute. And special attention was paid to low frequency signals, which were often filtered in the reported researches. Results show that at noncavitation condition, vibration level is closely related to flow structure interior pump. At partial flow rates, especially low flow rates, vibration level increases rapidly with the onset of rotating stall. At cavitation condition, it is proved that cavitation process has a significant impact on low frequency signals. With cavitation number decreasing, vibration level first rises to a local maximum, then it drops to a local minimum, and finally it rises again. At different flow rates, vibration trends in variable frequency bands differ obviously. Critical point inferred from vibration level is much larger than that from 3% head drop, which indicates that cavitation occurs much earlier than that reflected in head curve. Also, it is noted that high frequency signals almost increase simultaneously with cavitation occurring, which can be used to detect cavitation in centrifugal pump.

Experimental and numerical analysis of unsteady pressure pulsation in a centrifugal pump with slope volute

Abstract: This study experimentally and numerically investigates the unsteady flow in a centrifugal pump with special slope volute under various conditions to illustrate the detailed flow structures and pressure pulsation within the model pump. Whole flow passage is considered during the numerical simulation; pressure pulsation signals are extracted using nine fast-response pressure transducers. The Root mean square (RMS) method is introduced to deal with the discrete components at fBPF of the different monitoring points along the volute casing, which is an effective attempt to evaluate the overall pulsating level of the model pump. Results show that numerical method can predict the components at fBPF effectively; however, it has limited ability in capturing noise frequencies motivated by unsteady separate flow and non-linear interaction effect. Around the nominal flow rate, the predicted amplitudes at fBPF agree well with the experimental results, showing larger difference at the off-design conditions. To predict the pulsating level of the components at fBPF, two fitted equations of the RMS values versus the flow rate and specific speed are carried out, which would be very helpful in evaluating the pressure pulsation level in the centrifugal pump.

Investigation on Vibration Characteristics in a Centrifugal Pump with Special Slope Volute

Abstract: Vibration is one of the main problems which should be considered seriously in designing and operating a centrifugal pump. In this paper, a special slope volute was proposed to reduce vibration level of centrifugal pump. The goal of this paper was to analyze vibration characteristics of slope volute pump and provide a new method to reduce vibration energy in centrifugal pump. Experiments were carried out to obtain vibration signals at different flow rates of slope volute pump, which were compared with conventional spiral volute pump. Results show that vibration level is closely related to flow structure interior pump. At low flow rates, especially, vibration energy increases rapidly with the onset of rotating stall. Rotor-stator interaction mechanism changes when adopting slope volute. In slope volute pump, the peaks in power spectra correspond to different harmonics of fBPF at three measuring directions; however, in spiral volute pump, the predominant components always correspond to 2fBPF. From comparison...

Centrifugal pump impeller with elliptic blade outlet shape

Abstract: The invention relates to a centrifugal pump impeller with an elliptic blade outlet shape. Elliptic blade outlet edges (1) and (2) are respectively connected with and are smoothly tangent to blade working surfaces (3) and blade back surfaces (4).According to elliptic blade outlets, the blade outlet shape is adjusted, a blade outlet wake flow structure is improved, the velocity gradient of the working surface and the back surface of each blade outlet is reduced, and a bad mixing flow structure of each blade outlet is reduced, so that an impeller outlet flow field is uniformly reconstructed, the hydraulic loss of the centrifugal pump impeller is reduced, and the purpose of improving the centrifugal pump performance is achieved. The elliptic blade outlet edges (1) and (2) are smooth in shapes, have same elliptic geometrical shapes and are connected with and are smoothly tangent to the blade working surfaces (3) and the blade back surfaces (4); end points (5) of the elliptic outlet edges (1) and (2) are flush with impeller outlet edges (6); the influence of an included angle theta of tangent lines of each elliptic blade outlet on the centrifugal pump performance is obvious, and a variation range is 20 to 60 degrees.

Mixed-flow-pump impeller with working-face oval blade outlet sides

Abstract: The invention relates to a mixed-flow-pump impeller, in particular to a mixed-flow-pump impeller with working-face oval blade outlet sides, and belongs to the field of fluid machines. The mixed-flow-pump impeller with the working-face oval blade outlet sides is composed of a front cover plate, blades and a back cover plate. The blades are connected with the front cover plate and the back cover plate. The mixed-flow-pump impeller is characterized in that each oval blade outlet side is located at the tail end of the corresponding blade of the mixed-flow-pump impeller, the length of each oval blade outlet side is one fifth to one fourth of the length of the whole corresponding blade, the blade working face and the blade back face of each oval blade outlet side are in an oval arc shape, and the eccentricity e of each oval arc is larger than zero and smaller than one. According to the mixed-flow-pump impeller, starting from improving the structures of the blade working face outlet sides, the shapes of an original outlet of the mixed-flow-pump impeller is changed through the oval blade outlet sides, the backflow structure at the outlet is controlled and avoided accordingly, and the hydraulic losses of the mixed-flow-pump impeller are reduced so that the aim of efficient running of a mixed-flow pump can be achieved.

Investigation on Rotor-Stator Interaction in a Low Specific Speed Centrifugal Pump

Abstract: In centrifugal pump, due to intense rotor-stator interaction, high amplitude pressure pulsating would be induced, and it has a crucial influence on the stable operating of the pump. In this paper, a low specific speed centrifugal pump is investigated to illustrate unsteady flow within the centrifugal pump. Pressure pulsation signals are attained by mounting 20 monitoring points along the spiral volute, covering all the interested region of the model pump. FFT (Fast Fourier Transform algorithm) is applied to analyze the time-domain pressure signals.Results show that in pressure spectra, evident peaks at blade passing frequency fBPF together with its high harmonics can be identified, and the amplitudes are closely associated with operating conditions of the model pump and the positions of the monitoring points. At nominal flow rate, four vortical regions with high amplitude are captured inside the model pump. And the unsteady vortical structure at the near tongue region is related to the relative position of the impeller with respect to the tongue, and the upstream effect of the volute tongue significantly affects the vorticity distribution on the blade pressure side.At off-design conditions, the interaction pattern between the vortical structure and the volute tongue is significantly affected compared with that at the rated condition, as to the upstream effect of the tongue. At high flow rate, partial vortex would separate from the main vortex, but at low flow rate, the cutting and impingement effects of the tongue are much weaker due to almost all the vortex moving to the narrow side of the tongue.Based on the analysis of rotor-stator interaction in the model pump, some conclusions could be obtained. Pressure amplitudes at fBPF are associated with the positions of monitoring points and operating conditions of the model pump. Vorticity magnitude at blade exit increases as the impeller passes the volute tongue. And the fluid-dynamic blade-volute interaction is dominated by the vorticity shedding from blade trailing edge and their impingement on the volute tongue with subsequent cutting and distortion. And high pressure amplitude is generated with the corresponding high vorticity magnitude observed. So the intense interaction between flow structures (jet-wake pattern) and volute tongue is crucial to unsteady pressure pulsation. Thus, to lower pressure pulsation amplitude and fluid dynamic forces, controlling the vortical structure at blade trailing edge is an effective method.Copyright © 2015 by KSME

Diffuse type diversion ring matched with radial asymmetric guide blade bodies of pump

Abstract: The invention relates to a diffuse type diversion ring matched with radial asymmetric guide blade bodies of a pump, and belongs to the field of fluid machinery. The diffuse type diversion ring is characterized in that outlet sections of front and back cover plates of radial guide blade bodies are lengthened to form guide rings. In order to improve the hydraulic efficiency, the diffuse type diversion ring also can adopt the following technical scheme: the radial guide blade bodies consist of blades and the front and back cover plates; the blades are positioned between the front and back cover plates; two blades aligned to the outlet end of an annular pumping chamber and arranged anticlockwise are respectively a first blade and a second blade; an included angle between the first blade and the center line is beta 1; an included angle between the second blade and the center line is beta 2; beta 1 is equal to beta 2; the beta 1 is in a value range of 15-300, preferably 240; and the rest ten blades are symmetrically arranged in the peripheral direction. The diffuse type diversion ring improves the hydraulic matching performance of the asymmetric guide blade bodies and the pumping chamber so as to improve the efficiency and the operation stability of the pump.

Mixed flow impeller with suction side back blade

Abstract: The invention relates to a mixed flow pump, and in particular relates to a mixed flow impeller with a suction side back blade. The mixed flow impeller with the suction side back blade is characterized in that the suction side back blade is arranged between every two adjacent blades in a running channel of the mixed flow impeller; the suction side back blade is separated from a blade working surface and is mounted on the back surface of the blade. According to the mixed flow impeller with the suction side back blade, the suction side back blade is arranged in the running channel of the impeller and can be used for highly stopping any adverse axial flowing, so as to lower down the velocity gradient in the running channel; therefore, the uniformity of the structure of a flowing field of the running cannel of the impeller can be raised, and as a result, the performance of the pump can be further improved.

Centrifugal impeller with vaneless flow-splitting sheets

Abstract: The invention provides a centrifugal impeller with vaneless flow-splitting sheets, wherein the vaneless flow-splitting sheets are bent sheets with uniform thicknesses; the vaneless flow-splitting sheets are connected with a front impeller cover plate and a rear impeller cover plate; each vaneless flow-splitting sheet is located between two vanes; and the vaneless flow-splitting sheets are distributed circumferentially. The vaneless flow-splitting sheets block part of the passage of the outlet of the impeller to realize uniform reconstruction of the outflow field of the impeller to achieve the purpose of improving the performance of a pump. The outer surfaces of the vaneless flow-splitting sheets are flushed with the outlet of the impeller and are as thick as the edges of the outlets of the vanes; and the number of the vaneless flow-splitting sheets is the same as that of the vanes of the impeller. The vaneless flow-splitting sheets are far away from the working surface of the vanes and closer to the back surfaces of the vanes; the distance between the center of each vaneless flow-splitting sheet and the back surface of the outlet of the corresponding vane is 1/4 to 1/2 of the length of the arc between every two adjacent vanes; and the blocking area of the vaneless flow-splitting sheets is 1/6 to 1/3 of the area of the cross section of the passage of the outlet of the impeller.

Centrifugal pump impeller with round blade outlet sides

Abstract: The invention relates to a centrifugal pump impeller, and belongs to the field of fluid machines. The centrifugal pump impeller with round blade outlet sides is composed of a front cover plate, a rear cover plate and blades; the blades are located between the front cover plate and the rear cover plate; and the centrifugal pump impeller is characterized in that blade working faces and blade back faces are intersected in the circumferential direction of the blade outlet sides to form the round blade outlet sides. Geometrical shapes of blade outlets are changed, so that a flow structure of an impeller outlet is controlled, and therefore blade outlet complex flow fields can be evenly reconstructed. Flowing of the impeller outlet is controlled, and therefore hydraulic losses of an impeller are reduced, and the aims of improving the performance of a centrifugal pump is achieved; and the centrifugal pump impeller has an important significance in improvement of the efficiency of the centrifugal pump.