The Temporal-Spatial Features of Pressure Pulsation in the Diffusers of a Large-Scale Vaned-Voluted Centrifugal Pump

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.

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Efficiency improvement and evaluation of a centrifugal pump with vaned diffuser

Advances in Mechanical Engineering ◽

10.1177/1687814019825904 ◽

2019 ◽

Vol 11 (3) ◽

pp. 168781401982590 ◽

Cited By ~ 2

Author(s):

Kai Wang ◽

Yu-cheng Jing ◽

Xiang-hui He ◽

Hou-lin Liu

Keyword(s):

Centrifugal Pump ◽

Axial Force ◽

Flow Rate ◽

Pressure Pulsation ◽

Energy Performance ◽

Radial Force ◽

Design Flow ◽

Vaned Diffuser ◽

Original Scheme ◽

Design Flow Rate

In order to enhance the efficiency of centrifugal pump, the structure of a centrifugal pump with vaned diffuser, whose specific speed is 190, was numerically improved by trimming back-blades of impeller and smoothing sharp corner in annular chamber. The energy performance, the internal flow field, the axial force, the radial force, and the pressure pulsation of the pump were analyzed. Results show that efficiency of the improving scheme 1 under the design flow rate is 77.47%, which can balance 69.82% of the axial force, while efficiency of the improving scheme 2 under the design flow rate is the maximum, which could still balance 62.74% of the axial force. The pressure pulsations of the improving scheme 2 at the typical monitoring points are less than that of the improving scheme 1 and the original scheme. The difference of the radial force peak between the improving scheme 1 and the improving scheme 2 is very small. The vector distributions of the radial force of the improving scheme 1 and the improving scheme 2 are more uniform than that of the original scheme. Considering the efficiency, pressure pulsation, and axial force, experiment measurements on the improving scheme 2 were carried out to verify the effectiveness of the improvement result. Results of energy performance experiment show that efficiency of the improving scheme 2 under the design flow rate is 76.48%, which is 5.26 percentage points higher than that of the original scheme.

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Effect of vaned diffuser clocking position on hydraulic performance and pressure pulsation of centrifugal pump

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650920967247 ◽

2020 ◽

pp. 095765092096724

Author(s):

Hongyu Guan ◽

Wei Jiang ◽

Yuchuan Wang ◽

Gaoyang Hou ◽

Xiangyuan Zhu ◽

...

Keyword(s):

Energy Loss ◽

Centrifugal Pump ◽

Pressure Pulsation ◽

Guide Vane ◽

Hydraulic Performance ◽

Design Flow ◽

Maximum Difference ◽

Centrifugal Pumps ◽

Vaned Diffuser ◽

Diffuser Flow

The clocking position of the vaned diffuser, the circumferential position of the vaned diffuser relative to the volute, has a certain effect on the performance of the centrifugal pump. Therefore, this paper studies the guide vane centrifugal pump from the aspects of pressure pulsation, hydraulic performance, and energy loss. The maximum difference in efficiency is 3.4% under the design flow rate, and the maximum difference in the head coefficient is 4.7%. The hydraulic performance and pressure pulsation present different trends with the increase of the vaned diffuser clock angle. When the hydraulic performance and pressure pulsation are relatively good, the circumferential distance between the tongue and the upstream vaned diffuser blade is 3/4 of the diffuser flow path. In addition, the recommended vaned diffuser installation location may also be suitable for centrifugal pumps of similar construction. The energy loss was visualized using the theory of entropy production. The distributions of energy loss and flow field indicate that the energy loss of impeller and vaned diffuser changes little. The change of the vortex in the tongue and outlet area will cause a significant change in the energy loss of the volute, which is the main reason that the hydraulic performance of the centrifugal pump is affected by the clocking position of the vaned diffuser.

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Influence of Impeller Sinusoidal Tubercle Trailing Edge On Pressure Pulsation in a Centrifugal Pump At Nominal Flow Rate

Journal of Fluids Engineering ◽

10.1115/1.4050640 ◽

2021 ◽

Author(s):

Yanpi Lin ◽

Xiaojun Li ◽

Bowen Li ◽

Xiao-Qi Jia ◽

Zuchao Zhu

Keyword(s):

Centrifugal Pump ◽

High Speed ◽

Pressure Pulsation ◽

Humpback Whales ◽

Centrifugal Pumps ◽

Trailing Edge ◽

Rotor Stator Interaction ◽

High Speed Rotation ◽

Operation Stability ◽

Speed Rotation

Abstract The high-speed rotation of impellers leads to strong rotor-stator interaction, which mainly causes the pressure pulsation of centrifugal pumps. An impeller with a bionic sinusoidal tubercle trailing edge (STTE) can reduce the intensity of the rotor-stator interaction and thus reduce the pressure pulsation of the centrifugal pump. In this study three profiles of STTE were designed based on the pectoral fin structure of humpback whales of which the influence on the pressure pulsation of centrifugal pumps was studied via experiment and numerical simulation. Results show that a reasonable design of STTE can effectively eliminate the high-frequency pressure pulsation in the rotor-stator interaction region of the centrifugal pump. The use of STTE2 and STTE3 profiles affects the amplitude reduction of pressure pulsation at the blade passing frequency (fBPF). Compared with the impeller without the STTE profile, the amplitudes of pressure pulsation with STTE2 and STTE3 profiles are decreased by 47.10% and 44.20% at the pump discharge, while the decrease, at the volute throat are 30.36% and 25.97%, respectively. Detailed flow structures inside the pump show that the STTE profile can inhibit the vortex generation at the blade trailing edge, and the local high-intensity pressure pulsation can be reasonably avoided. This study helps improve the pressure pulsation characteristic of centrifugal pumps and their operation stability.

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Influence of the Blade Trailing Edge Profile on the Performance and Unsteady Pressure Pulsations in a Low Specific Speed Centrifugal Pump

Journal of Fluids Engineering ◽

10.1115/1.4031911 ◽

2016 ◽

Vol 138 (5) ◽

Cited By ~ 38

Author(s):

Bo Gao ◽

Ning Zhang ◽

Zhong Li ◽

Dan Ni ◽

MinGuan Yang

Keyword(s):

Centrifugal Pump ◽

Pressure Pulsation ◽

Pressure Pulsations ◽

Trailing Edge ◽

Unsteady Pressure ◽

Pulsation Amplitude ◽

Trailing Edges ◽

Edge Profile ◽

Low Specific Speed ◽

Specific Speed

The blade trailing edge profile is of crucial importance for the performance and pressure pulsations of centrifugal pumps. In the present study, numerical investigation is conducted to analyze the effect of the blade trailing edge profile influencing the performance and unsteady pressure pulsations in a low specific speed centrifugal pump. Five typical blade trailing edges are analyzed including original trailing edge (OTE), circle edge (CE), ellipse on pressure side (EPS), ellipse on suction side (ESS), and ellipse on both sides (EBS). Results show that the well-designed blade trailing edges, especially for the EPS and EBS profiles, can significantly improve the pump efficiency. Pressure amplitudes at fBPF and 2fBPF are together calculated to evaluate the influence of the blade trailing edge profile on pressure pulsations. The EPS and EBS profiles contribute obviously to pressure pulsations reduction. In contrast, the CE and ESS profiles lead to increase of pressure pulsation amplitude compared with the OTE pump. Vorticity distribution at the blade trailing edge demonstrates that the EPS and EBS profiles have an effective impact on reducing vortex intensity at the blade trailing edge. Consequently, rotor–stator interaction could be attenuated leading to lower pressure pulsation amplitude. It is thought to be the main reason of pressure pulsations reduction obtained with the proper modified blade trailing edges. The results would pave the way for further optimization of the blade trailing edge profile.

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Study on Pressure Pulsation in the Volute of a Centrifugal Pump by Large Eddy Simulation

Volume 7: Fluids Engineering Systems and Technologies ◽

10.1115/imece2014-37233 ◽

2014 ◽

Cited By ~ 1

Author(s):

Yuan Zhang ◽

Yongxue Zhang ◽

Jinya Zhang ◽

Hucan Hou

Keyword(s):

Large Eddy Simulation ◽

Unsteady Flow ◽

Centrifugal Pump ◽

Pressure Pulsation ◽

Stable Operation ◽

Flow Rates ◽

Eddy Simulation ◽

Pulsation Amplitude ◽

Blade Passing Frequency ◽

Large Eddy

Pressure pulsation caused by unsteady flow plays one of the most important roles in the stable operation of centrifugal pumps. Numerical simulation method of LES (Large Eddy Simulation) with WALE model has been used to calculate the unsteady flow in IS150-125-250 centrifugal pump passages. Three groups monitoring points distributed on 8 cross sections in different radial, circumferential, axial directions were set. And pressure pulsation in volute with different flow rates, radial distance, circumferential angles and axial distance was studied. Changing of the maximal pressure pulsation amplitude on monitoring points has been obtained by time and frequency domain analysis. The research demonstrated the maximum amplitude of pressure pulsation is located at the volute tongue, and its magnitude changes with flow rates at each monitoring point. The dominant frequency of pressure pulsation in the volute is equal to the blade passing frequency and the sub-dominant frequencies are also related to the blade passing frequency. The periodicities of circumferential pressure pulsations at different monitoring points in the volute are similar. More deviation of design flow rate results in larger pressure pulsation amplitude. Increasing radius will weaken pressure pulsation amplitude while closing to the wall of volute can strengthen the pressure pulsation. The research of pressure pulsation in volute will show great help in hydraulic design of centrifugal pump to realize longer component life, less vibration and more stable operation.

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Large-scale mapping of the catenas vegetation in Subarctic tundra

Geobotanical mapping ◽

10.31111/geobotmap/1993.3 ◽

1995 ◽

pp. 3-21

Author(s):

S. S. Kholod

Keyword(s):

Spatial Distribution ◽

Vegetation Cover ◽

Large Scale ◽

Block Diagram ◽

Abiotic Factors ◽

Ecological Factors ◽

Spatial Arrangement ◽

Geological Time ◽

Ecological Barriers ◽

Functional Zones

One of the most difficult tasks in large-scale vegetation mapping is the clarification of mechanisms of the internal integration of vegetation cover territorial units. Traditional way of searching such mechanisms is the study of ecological factors controlling the space heterogeneity of vegetation cover. In essence, this is autecological analysis of vegetation. We propose another way of searching the mechanisms of territorial integration of vegetation. It is connected with intracoenotic interrelation, in particular, with the changing role of edificator synusium in a community along the altitudinal gradient. This way of searching is illustrated in the model-plot in subarctic tundra of Central Chukotka. Our further suggestion concerns the way of depicting these mechanisms on large-scale vegetation map. As a model object we chose the catena, that is the landscape formation including all geomorphjc positions of a slope, joint by the process of moving the material down the slope. The process of peneplanation of a mountain system for a long geological time favours to the levelling the lower (accumulative) parts of slopes. The colonization of these parts of the slope by the vegetation variants, corresponding to the lowest part of catena is the result of peneplanation. Vegetation of this part of catena makes a certain biogeocoenotic work which is the levelling of the small infralandscape limits and of the boundaries in vegetation cover. This process we name as the continualization on catena. In this process the variants of vegetation in the lower part of catena are being broken into separate synusiums. This is the process of decumbation of layers described by V. B. Sochava. Up to the slope the edificator power of the shrub synusiums sharply decreases. Moss and herb synusium have "to seek" the habitats similar to those under the shrub canopy. The competition between the synusium arises resulting in arrangement of a certain spatial assemblage of vegetation cover elements. In such assemblage the position of each element is determined by both biotic (interrelation with other coenotic elements) and abiotic (presence of appropriate habitats) factors. Taking into account the biogeocoenotic character of the process of continualization on catena we name such spatial assemblage an exolutionary-biogeocoenotic series. The space within each evolutionary-biogeocoenotic series is divided by ecological barriers into some functional zones. In each of the such zones the struggle between synusiums has its individual expression and direction. In the start zone of catena (extensive pediment) the interrelations of synusiums and layers control the mutual spatial arrangement of these elements at the largest extent. Here, as a rule, there predominate edificator synusiums of low and dwarfshrubs. In the first order limit zone (the bend of pediment to the above part of the slope) one-species herb and moss synusiums, oftenly substituting each other in similar habitats, get prevalence. In the zone of active colonization of slope (denudation slope) the coenotic factor has the least role in the spatial distribution of the vegetation cover elements. In particular, phytocoenotic interactions take place only within separate microcoenoses of herbs, mosses and lichens. In the zone of the attenuation of continualization process (the upper most parts of slope, crests) phytocoenotic interactions are almost absent and the spatial distribution of vegetation cover elements depends exclusively on the abiotic factors. The principal scheme of the distribution of vegetation cover elements and the disposition of functional zones on catena are shown on block-diagram (fig. 1).

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Modeling Spatiotemporal Population Changes by Integrating DMSP-OLS and NPP-VIIRS Nighttime Light Data in Chongqing, China

Remote Sensing ◽

10.3390/rs13020284 ◽

2021 ◽

Vol 13 (2) ◽

pp. 284

Author(s):

Dan Lu ◽

Yahui Wang ◽

Qingyuan Yang ◽

Kangchuan Su ◽

Haozhe Zhang ◽

...

Keyword(s):

Spatial Distribution ◽

Relative Error ◽

Urban Areas ◽

Large Scale ◽

Population Distribution ◽

Spatial Optimization ◽

Distribution Data ◽

Mountainous Areas ◽

Mean Relative Error ◽

Nighttime Light

The sustained growth of non-farm wages has led to large-scale migration of rural population to cities in China, especially in mountainous areas. It is of great significance to study the spatial and temporal pattern of population migration mentioned above for guiding population spatial optimization and the effective supply of public services in the mountainous areas. Here, we determined the spatiotemporal evolution of population in the Chongqing municipality of China from 2000–2018 by employing multi-period spatial distribution data, including nighttime light (NTL) data from the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) and the Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS). There was a power function relationship between the two datasets at the pixel scale, with a mean relative error of NTL integration of 8.19%, 4.78% less than achieved by a previous study at the provincial scale. The spatial simulations of population distribution achieved a mean relative error of 26.98%, improved the simulation accuracy for mountainous population by nearly 20% and confirmed the feasibility of this method in Chongqing. During the study period, the spatial distribution of Chongqing’s population has increased in the west and decreased in the east, while also increased in low-altitude areas and decreased in medium-high altitude areas. Population agglomeration was common in all of districts and counties and the population density of central urban areas and its surrounding areas significantly increased, while that of non-urban areas such as northeast Chongqing significantly decreased.

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Experiment and simulation about the effect of wear-ring abrasion on the performance of a marine centrifugal pump

Advances in Mechanical Engineering ◽

10.1177/1687814021998115 ◽

2021 ◽

Vol 13 (2) ◽

pp. 168781402199811

Author(s):

Wu Xianfang ◽

Du Xinlai ◽

Tan Minggao ◽

Liu Houlin

Keyword(s):

Numerical Simulation ◽

Centrifugal Pump ◽

Pressure Pulsation ◽

Vibration Velocity ◽

Test Results ◽

Obvious Effect ◽

Performance Change ◽

Pump Test ◽

Simulation Results ◽

Axis Passing

The wear-ring abrasion can cause performance degradation of the marine centrifugal pump. In order to study the effect of front and back wear-ring clearance on a pump, test and numerical simulation were used to investigate the performance change of a pump. The test results show that the head and efficiency of pump decrease by 3.56% and 9.62% respectively at 1.0 Qd due to the wear-ring abrasion. Under 1.0 Qd, with the increase of the front wear-ring the vibration velocity at pump foot increases from 0.4 mm/s to 1.0 mm/s. The axis passing frequency (APF) at the measuring points increases significantly and there appears new characteristic frequency of 3APF and 4APF. The numerical simulation results show that the front wear-ring abrasion affects the flow at the inlet of the front chamber of the pump and impeller passage. And the back wear-ring abrasion has obvious effect on the flow in the back chamber of the pump and impeller passage, while the multi-malfunction of the front wear-ring abrasion and back wear-ring abrasion has the most obvious effect on the flow velocity and flow stability inside pump. The pressure pulsation at Blade Passing Frequency (BPF) of the three schemes all decrease with the increase of the clearance.

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Spatial Agglomeration of China’s Forest Products Manufacturing Industry: Measurement, Characteristics and Determinants

Forests ◽

10.3390/f12081006 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1006

Author(s):

Zhenhuan Chen ◽

Hongge Zhu ◽

Wencheng Zhao ◽

Menghan Zhao ◽

Yutong Zhang

Keyword(s):

Spatial Distribution ◽

Spatial Data ◽

Large Scale ◽

Manufacturing Industry ◽

Economies Of Scale ◽

Forest Products ◽

Spatial Data Analysis ◽

Forest Protection ◽

Spatial Agglomeration ◽

Continuous Space

China’s forest products manufacturing industry is experiencing the dual pressure of forest protection policies and wood scarcity and, therefore, it is of great significance to reveal the spatial agglomeration characteristics and evolution drivers of this industry to enhance its sustainable development. Based on the perspective of large-scale agglomeration in a continuous space, in this study, we used the spatial Gini coefficient and standard deviation ellipse method to investigate the spatial agglomeration degree and location distribution characteristics of China’s forest products manufacturing industry, and we used exploratory spatial data analysis to investigate its spatial agglomeration pattern. The results show that: (1) From 1988 to 2018, the degree of spatial agglomeration of China’s forest products manufacturing industry was relatively low, and the industry was characterized by a very pronounced imbalance in its spatial distribution. (2) The industry has a very clear core–periphery structure, the spatial distribution exhibits a “northeast-southwest” pattern, and the barycenter of the industrial distribution has tended to move south. (3) The industry mainly has a high–high and low–low spatial agglomeration pattern. The provinces with high–high agglomeration are few and concentrated in the southeast coastal area. (4) The spatial agglomeration and evolution characteristics of China’s forest products manufacturing industry may be simultaneously affected by forest protection policies, sources of raw materials, international trade and the degree of marketization. In the future, China’s forest products manufacturing industry should further increase the level of spatial agglomeration to fully realize the economies of scale.

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