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A large-scale, vaned-voluted centrifugal pump can be applied as the key component in water-transfer projects. Pressure pulsation will be an important factor in affecting the operation stability. This paper researches the propagation and spatial distribution law of blade passing frequency (BPF) and its harmonics on the design condition by numerical simulation. Experimental and numerical monitoring is conducted for pressure pulsation on four discrete points in the vaneless region, which shows that the BPF is dominant. The pulsation tracking network (PTN) is applied to research propagation law and spatial distribution law. It provides a reference for frequency domain information and visualization vaned diffuser. The amplitude of BPF and its harmonics decays rapidly in the vaneless region. BPF and BPF’s harmonics influence each other. BPF has local enhancement in the vaneless region when its harmonics attenuate. In the vaned diffuser, the pulsation amplitude of BPF attenuates rapidly, but the local high-pressure pulsation amplitude can be found on the vane blade concave side because of obstruction and accumulation of the vaned diffuser. In the volute, the pulsation amplitude of BPF is low with the decelerating attenuation. This study provides an effective method for understanding the pressure pulsation law in turbomachinery and other engineering flow cases.

• Application of Active noise control in a pump system with variable point of operations for the very first time. • Key technology for smart-grid controlled pump system in order to avoid undesirable pressure pulsation related issues like vibration and noise. Smart-grid control aims to use current power converter technology of pump drives for grid stabilization. Hereby, fluctuations of the power grid frequency are transmitted to the pump drive resulting in pump speed changes. Along with the inherent impeller design these pump speed changes are resulting in pressure pulsations which propagate as hydro acoustic pressure waves throughout the pump system causing noise and vibration issues in the piping system. Therefor, in order to realize smart-grid control, a solution must be found to attenuate or counteract these hydro acoustic pressure waves. In an earlier work [1] , an active noise control (ANC) system to reduce pressure pulsations at a pump's blade passing frequency (BPF) was published with the focus on constant points of operation. However, utilizing smart-grid control will results in high gradients of the pump speed and constantly changing points of operation are to be expected. This paper aims to attack those kinds of operating conditions. Within this paper, moving frequencies of interest at different pump speed gradient with and without active attenuation are analyzed and extracted from time series data by means of Vold-Kalman order tracking filter. In relation to possible fluctuations in the power grids frequency, the active attenuation performance of the ANC system is evaluated. [ABSTRACT FROM AUTHOR]

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As a kind of pump with low head and large capacity, the mixed-flow pump is widely used in large quantities of fields including water conservancy and sewage system of municipal works and so on. The pressure pulsation and flow-induced noise of pump have become two of the most important issues which have negative effect on reliability. The pressure pulsation is the interior performance of the unsteady flow in the pump and the flow-induced noise and vibration are the exterior performance of the unsteady flow in the pump. In order to study the rules of pressure pulsation and flow-induced noise change under different flow rate conditions in a mixed-flow pump and to find the relationship between pressure pulsation and flow-induced noise, the flow field and sound field were numerical simulated. This paper used the PRO/E software to build the pump model and to use the ICEM CFD to conduct the mesh division of the calculated domain. The mixed-flow pump mainly consisted of inlet pipe, impeller, volute and discharge pipe. The unsteady flow was numerical simulated based on RANS solver and SST turbulence model. During the unsteady simulation, the mixed-flow pump rotated for 18 cycles so as to improve the simulation stability. The simulation results of the last 2 periods were used to analyze the time domain characteristics and frequency domain characteristics of pressure pulsation in the pump. And by using the pressure pulsation on the blade as noise source, acoustic Boundary Element Method (BEM) was applied to simulate the flow-induced noise of the mixed-flow pump. The simulation results show that the pressure pulsation amplitude decreases from shroud to hub both at the inlet and outlet of the impeller, and the maximum pressure pulsation appears at the inlet of impeller. So it is crucial to conduct some optimal design for the shroud location in order to weaken the pressure pulsation. Along the circumferential direction in the volute, the pressure pulsation amplitude appears to be the largest near the tongue, the pressure pulsation decreases with the increase of circular angles. And at the outlet of volute, the pressure pulsation appears approximately to be nothing which indicates the flow at this location is steady. The dominant frequency of pressure pulsation in each monitoring point of the mixed-flow pump is always the blade passing frequency under different flow rate conditions. The rotor-stator interaction between the rotating blades and the stationary volute may be the major source of flow-induced noise in the mixed-flow pump. The dominant frequency of flow-induced noise is integral effected by the pressure pulsation and the structure mode of the pump. It is easy to occur resonate between fluid domain and structure domain when the domain frequency of pressure pulsation is closely equal to the domain frequency of the structure mode. The stronger the pressure pulsation is, the more intense the radiation level of corresponding flow-induced noise will produce under the same condition. Weakening the pressure pulsation in the mixed-flow pump is an effective way to reduce the flow-induced noise. This paper has reference value for study on pressure pulsation and flow-induced noise in fluid machinery. [ABSTRACT FROM AUTHOR]

The impeller diameter is one of the fundamental parameters of double channel sewage pumps. In order to analyze the effect of different impeller diameters on pressure fluctuation, the unsteady characteristics of a double channel sewage pump was numerically simulated by using the Mixture multiphase flow model and the developed standard k-e turbulence model. The double channel pump mainly consisted of volute, impeller, inlet extension and outlet extension. In order to improve the calculation stability, the impeller totally rotated for 18 cycles in the simulation and the total computation time was 0.3724 s. The simulation results of the last 2 periods were used to analyze the pressure fluctuation in the pump. Monitoring points were set in the middle of each section in volute circumference and in the tongue region so as to analyze the distribution and variation of the pressure fluctuation with the impeller diameter in the volute especially around the tongue. The calculation results were compared with the experimental data when the impeller diameter was 103 mm. The experiment was conducted in an open test platform, and the test measured the hydraulic performance of the pump and the pressure pulsation of the volute outlet. The pump head and efficiency deviation between calculated and experimental results were 2.37% and -0.46% respectively under the design condition, while the errors were slightly larger but less than 5% under other conditions, which illuminated that the numerical model and calculation methods predicted the hydraulic performance of double channel sewage pump extremely well so that it could be used to predict the characteristics under other impeller diameters. The pressure pulsation trend between calculated and experimental results fitted well and the error was small, which demonstrated that the CFD (computational fluid dynamics) method was able to forecast the distribution and variation of pressure pulsation in the pump accurately. The results showed that the pressure fluctuation of volute circumference under the design condition generally got weaker with the addition of certain amount of particles and the maximum decreased by 30.9%, and the average pressure pulsation reduction of the volute circumferential points decreased with the increase of impeller diameter. The results made clear that selecting appropriate impeller diameter could contribute to prevent pressure pulsation and the induced vibration and noise in the pump when transporting solid-liquid two-phase flow. The pressure fluctuation around the tongue got more and more sharply with the increase of impeller diameter when the water included proper amount of particles. The dominant frequency of points near the tongue was almost the blade passing frequency. Compared with water, the maximum amplitude of the reduction of the pressure pulsation increased and then decreased with the increase of impeller diameter, and the maximum reduction was 22.7%. The lower point of these points in the tongue region was affected maximumly by the rotor-stator interaction between impeller and volute. Instantaneous static pressure of every monitoring point fluctuated sharply when impeller diameter increased to 105 mm under solid-liquid two-phase flow. Selecting the appropriate impeller diameter could contribute to weaken the pressure pulsation when transporting solid-liquid two-phase flow. The study indicates that the impeller diameter has a very important impact on the distribution and variation of the double channel sewage pump and it provides the basis for the optimization design of double channel sewage pump. [ABSTRACT FROM AUTHOR]

Abstract: Pressure pulsations excited by a centrifugal turbomachinery such as compressor, fan or pump at the blade passing frequency may cause severe noise and vibrations in piping system. Therefore, the practical evaluation method of pressure pulsations is strongly recommended. In particular, the maximum pressure amplitude under the resonant conditions should be appropriately evaluated. In this study, a one-dimensional excitation source model for a compressor or pump is introduced based on the equation of motion, so as to incorporate the non-linear damping proportional to velocity squared in the total piping system including the compressor or pump. The damping characteristics of the compressor or pump are investigated by using the semi-empirical model. It is shown that the resistance coefficient of the compressor or pump depends on the Reynolds number that is defined using the equivalent velocity of the pulsating flow. The frequency response of the pressure amplitude and the pressure distribution in the piping system can be evaluated by introducing the equivalent resistance of the compressor or pump and that of piping system. In particular, the relation of the maximum pressure amplitude in piping system to the location of the excitation source under resonant conditions can be evaluated. Finally, the reduction of the pressure pulsations by use of an orifice plate is discussed in terms of the pulsation energy loss. [Copyright &y& Elsevier]

A large-scale, vaned-voluted centrifugal pump can be applied as the key component in water-transfer projects. Pressure pulsation will be an important factor in affecting the operation stability. This paper researches the propagation and spatial distribution law of blade passing frequency (BPF) and its harmonics on the design condition by numerical simulation. Experimental and numerical monitoring is conducted for pressure pulsation on four discrete points in the vaneless region, which shows that the BPF is dominant. The pulsation tracking network (PTN) is applied to research propagation law and spatial distribution law. It provides a reference for frequency domain information and visualization vaned diffuser. The amplitude of BPF and its harmonics decays rapidly in the vaneless region. BPF and BPF's harmonics influence each other. BPF has local enhancement in the vaneless region when its harmonics attenuate. In the vaned diffuser, the pulsation amplitude of BPF attenuates rapidly, but the local high-pressure pulsation amplitude can be found on the vane blade concave side because of obstruction and accumulation of the vaned diffuser. In the volute, the pulsation amplitude of BPF is low with the decelerating attenuation. This study provides an effective method for understanding the pressure pulsation law in turbomachinery and other engineering flow cases. [ABSTRACT FROM AUTHOR]