Effects of modifying the blade trailing edge profile on unsteady pressure pulsations and flow structures in a centrifugal pump

et al. 2020

Applied Sciences

The parameters of blade trailing edge have an important influence on the performance of centrifugal pump and internal unstable flow. In this study, the influences of cutting angles of blade trailing edge on unstable pressure pulsation and unstable flow structure are investigated using a centrifugal pump under off-design conditions through large eddy simulation. Three typical blade trailing edges, namely, original trailing edge (OTE), 15° cutting angle of blade trailing edge (OBS15) and 30° cutting angle of blade trailing edge (OBS30), are analysed. Results show that the cutting angle of blade trailing edge has a certain effect on the performance of the centrifugal pump. Under part-load conditions, the OBS30 impeller evidently contributes to the reduction in pressure pulsation intensity. By contrast, the OBS15 impeller has opposite effect because of the increase in wake vortex intensity. The OBS30 impeller can effectively improve the unstable vortex structure caused by backflow at the centrifugal pump tongue using a new Ω method. Consequently, reduction in the unstable flow structure mainly contributes to the reduction in pressure pulsation used by the proper cutting angle of blade trailing edge.

Section: Analysis Of Unstable Flow Structurementioning

confidence: 99%

Section: Analysis Of Unstable Flow Structurementioning

confidence: 99%

Influence of Cutting Angle of Blade Trailing Edge on Unsteady Flow in a Centrifugal Pump Under Off-Design Conditions

Cui

et al. 2020

Applied Sciences

“…(node,t) = P(node)+P(node,t) (11) where the numerical value of P(node) is defined the arithmetic mean value of pressure in one revolution (12) where N is the number of time steps, t0 is the initial moment and ∆ is the time step length. Thus the value of P(node,t) is the difference between instantaneous pressure value (node,t) and P(node) P(node,t)=P(node,t)-P(node) (13) ̃( , ) is worth in-depth study as it indicates the instability of the inner flow of centrifugal pump.…”

Section: Pressure Pulsation Characteristicsmentioning

confidence: 99%

“…C P ' decreases to the minimum (slightly higher than 0.01) under Q0.9. Subsequently, it increases continuously with the continuous To further compare pressure fluctuation characteristics under different flow rates, the time-varying curves P(node, t) of pressure at different monitoring nodes are decomposed into the fixed component P(node) and the fluctuating component P(node, t), as shown in Equation (11).…”

Section: Pressure Pulsation Characteristicsmentioning

confidence: 99%

“…Similar pulsation tendency is also fund in the hydraulic radial force on the impeller, because the hydraulic force mainly depends on the integration of pressure on the impeller surfaces. In addition, there are also other obvious frequency components rather than f BPF or multiple f n , which are stimulated by a serious complex unsteady flow behaviors, such as the jet-wake pattern along the blade extension direction, the flow impact on the tongue, and the flow separation on the blade suction surface [10][11][12]. The above behaviors usually become more evident under off-design conditions and would take much greater risks for the operation of centrifugal pump [13,14].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

CFD-Rotordynamics Sequential Coupling Simulation Approach for the Flow-Induced Vibration of Rotor System in Centrifugal Pump

You

et al. 2020

Applied Sciences

Featured Application: The numerical approach in this article can provide abundant information about the flow induced vibration of the pump rotor and may offer theoretical guidance to the design of reducing vibration and safety monitoring of centrifugal pumps.Abstract: Vibration of the rotor system is closely related with the operation stability of centrifugal pump, and it is inevitably induced by the unsteady inner flow. An unsteady computational fluid dynamics model coupling with a rotordynamics model was presented, and the corresponding numerical calculation program, including a self-designed rotordynamics code, was developed on the commercial package ANSYS Workbench. The validity of the numerical calculation model was verified by a hydraulic performance and vibration test based on an industrial centrifugal pump. The hydraulic radial forces on impeller, pressure pulsation, deformation, and vibration of the main shaft under nine different flow rates were systematically investigated and explained preliminarily from the view of inner unstable flow. Results show that the blade passing frequency is the dominant frequency in the fluctuation of the above dynamical behaviors, which is closely related to the rotor-stator interaction between the impeller and volute casing. This study built the connection between internal fluid flow in the centrifugal pump and the vibration of its external rotor structure, and may provide theoretical references for the design of vibration-reducing and safety monitoring strategies design of centrifugal pumps.3 of 33 former works, the first and foremost improvement of this work is the application of rotordynamics in the CSD, where the bearing damping matrix and gyroscopic matrix have been added to the general dynamic equation. With this advantage, the above new approach is able to provide a wealth shaft oscillation information including vibration velocity and shaft centerline orbit, with both the unsteady hydraulic force on the impeller and the rotor dynamic properties in consideration.In this article, an industrial split-case double suction centrifugal pump was chosen for study, and the unsteady flow as well as rotor assembly vibration behaviors under different operation conditions were investigated. The remaining of this article was organized as follows. In Section 2, the mathematical model and its overall frame are presented. Section 3 describes the computation details and experiment setup for a research case. Sections 4 and 5 are the analysis and discussion for the numerical and experimental results, followed by the conclusions in Section 6. Sequential Coupling Model Hypothesis and SimplificationThis study constructs the CFD-rotordynamics sequential coupling numerical model of centrifugal pump mainly based on following hypotheses and simplifications:(1) The coupling between flow field and rotordynamics belongs to one-way coupling. It means that only influences of flow induced exciting force on the vibration behavior of the rotor system were considered, but interferences of the deformati...

Effect of the staggered impeller on reducing unsteady pressure pulsations of a centrifugal pump

Jiang

Energy Science & Engineering

Liu

et al. 2021

Self Cite

The emitted noise and vibration induced by the unsteady flow of the centrifugal pump are always focused during its running, which is also associated with the high amplitude pressure pulsations. How to reduce pressure pulsations remains a crucial problem for the researcher considering low noise design of the centrifugal pump. In the current research, a special staggered impeller is proposed to reduce intense pressure pulsations of a centrifugal pump with n s = 69 based on alleviating rotor-stator interaction. The numerical simulation method is conducted to illustrate the influence of staggered impeller on the pump performance and pressure pulsations, and three typical flow rates (0.8Ф N -1.2Ф N ) are simulated. Resultsshow that the staggered impeller will lead to the pump head increasing, and at the design working condition, the increment reaches about 3% compared with the original impeller. Meanwhile, the pump efficiency is little affected by the staggered impeller, which is almost identical with the original impeller. From comparison of pressure spectra at 20 monitoring points around the impeller outlet, it is validated that the staggered impeller contributes significantly to decreasing pressure pulsations at the concerned working conditions. At the blade passing frequency, the averaged reduction of 20 points reaches 89% by using the staggered impeller at 1.0Ф N . The reduction reaches to 90%, 80% at 0.8Ф N , 1.2Ф N , respectively. Caused by the rib within the staggered impeller, the internal flow field in the blade channel will be affected. Finally, it is concluded that the proposed staggered impeller surely has a significant effect on alleviating intense pressure pulsation of the model pump and does not obviously alter the global performance of the pump, which is very promising during the low noise pump design considering its feasibility for manufacturing.