Investigation on Energy Loss in Centrifugal Pump Based on Entropy Generation and High-Order Spectrum Analysis

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Baoling Cui ◽  
Chenliang Zhang
Keyword(s):  
Energy Loss ◽  
Internal Energy ◽  
Centrifugal Pump ◽  
Entropy Generation ◽  
Spectrum Analysis ◽  
Pressure Pulsation ◽  
High Order ◽  
Energy Losses ◽  
Fundamental Characteristic ◽  
Order Spectrum

Abstract Full-open, straight-blade centrifugal pumps have the advantages of simple structure and high stability at high speeds. However, this type of centrifugal pump has a large internal energy loss and low efficiency. The flow loss caused by unstable flow accounts for most of the internal energy loss of a centrifugal pump, and this energy dissipates mainly to the surroundings of the pump in the form of pressure pulsation and vibration. In this study, to effectively understand the hydraulic behavior and energy loss in a centrifugal pump, the energy losses in the pump were numerically analyzed by the entropy generation method, the distribution of the energies of pressure pulsation and vibration was evaluated based on experimental results at different flowrates, and the correlation between flow and energy loss at 20% of the design flowrate (Qd) was investigated by high-order spectrum analysis. The energies of pressure pulsation and vibration in the experiment were evaluated by the root-mean-square (RMS) value. The distribution of the entropy generation rate (EGR) indicated large energy losses at the diffusion section of the volute, clearance, tongue, and blade inlet. At 20% of the design flowrate (Qd), the energy loss was caused by the backflow near the tongue, and the EGR at EP2 had a nonlinear fundamental characteristic frequency of 0.44fn. By bispectrum and coherence analysis, the nonlinear fundamental characteristic frequencies generated by the unforced flow were analyzed, and it was found that unforced flow was transmitted to one another in the near-tongue region.

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

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.

Blade Thickness Redesign to Improve Efficiency and Decrease Unsteady Pressure Pulsation of a Low Specific Speed Centrifugal Pump

2021 ◽  
Author(s):  
Chengshuo Wu ◽  
Peng Wu ◽  
Dazhuan Wu
Keyword(s):  
Energy Loss ◽  
Secondary Flow ◽  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
Dynamic Performance ◽  
Entropy Generation Rate ◽  
Pressure Pulsations ◽  
Blade Thickness ◽  
Low Specific Speed ◽  
Specific Speed

Abstract The existence of secondary flow in the impeller brings extra energy loss and aggravates the pressure pulsation which will worsen the hydraulic and dynamic performance of the pump. In this paper, based on the forces balance in the direction perpendicular to the streamline, an optimal design method for the blade thickness of a low specific speed centrifugal pump is proposed to suppress the secondary flow in the impeller. The origin impellers with 5 and 7 cylinder blades are redesigned and the hydraulic and dynamic performance of the model pump are investigated by numerical simulation and experimental. Results show that the blade modification proposed in this paper can effectively improve the efficiency of the model pump and reduce the internal pressure pulsations. The internal flow analysis shows that the performance improvement attributes to the suppression of secondary flow in the impeller. And the entropy generation rate is introduced to measure and locate the loss in the pump. Results show that on the one hand, the suppression of secondary flow can reduce the energy loss in the pump and improve the efficiency; on the other hand, it can repress the jet wake structure at impeller outlet and alleviate the intensity of pressure pulsations.

Studying on the Magnetorheological Fluids and its Rheometer

2011 ◽  
Vol 230-232 ◽  
pp. 1396-1401 ◽  
Author(s):  
Bing San Chen ◽  
Ji Bin Jiang ◽  
Fu Jiang Zhang
Keyword(s):  
Dynamic Characteristics ◽  
Spectrum Analysis ◽  
Computer Software ◽  
High Order ◽  
Step Motor ◽  
Order Analysis ◽  
Analysis Process ◽  
Mr Fluids ◽  
Order Spectrum ◽  
Measurement And Analysis

This paper presents a magnetorheological(MR) rheometer which consists of a pair of rotating parallel disc, step motor, the signal collecting device, computer software for dynamic analysis etc.. In order to assess the performance of the MR rheometer, high-order spectrum analysis tools are used. The theoretical and experimental results indicate that the rheometer is useful to test the dynamic charicteristics of the MR fluids and the high-order analysis might be helpful to describe MR rheometer dynamic characteristics. The measurement and analysis process based on virtual instruments are automatically controlled by computer in this paper.

Analysis of Statistical Characteristics of the Laser Vibrometer’s Static Signal Noise

2014 ◽  
Vol 986-987 ◽  
pp. 2048-2051
Author(s):  
Jing Yang ◽  
Jian Long Tang ◽  
Jun Hui Hou ◽  
Xue Zhang ◽  
Zhi Shan Wu
Keyword(s):  
Power Spectrum ◽  
Frequency Spectrum ◽  
Spectrum Analysis ◽  
Noise Signal ◽  
High Order ◽  
Random Signal ◽  
Statistical Characteristics ◽  
Signal Noise ◽  
Order Spectrum ◽  
Laser Signal

The static signal is collected through the experiment, and the probability density function model is established. The static random signal noise is analyzed by frequency spectrum, power spectrum and high order spectrum analysis. It is found that the third order spectrum of the laser static signal is zero by the high order spectrum analysis. Noise signal is only to analyze on the frequency spectrum and power spectrum. The results show that the static laser signal has the characteristics of stationary Gauss random signal.

Structural Damage Identification Based on Moving Load and High-Order Spectrum Analysis

2012 ◽  
Vol 594-597 ◽  
pp. 1082-1085
Author(s):  
Bu Yu Wang
Keyword(s):  
Neural Network ◽  
Spectrum Analysis ◽  
Structural Damage ◽  
Damage Identification ◽  
Moving Load ◽  
High Order ◽  
Structural Vibration ◽  
Order Spectrum ◽  
Nonlinear Character ◽  
Non Stationary Signal

Moving load could enhance damage-structural nonlinear character. High-order statistical analysis described character of non-stationary signal more exactly than traditional fourier spectrum based on second-order statistics analysis. The result of high-order spectrum analysis was two-dimensional，and spectrum entropy of different frequency can extract its intrinsic information and characters from it. Using these characters, the structural damage pattern could be recognized by neural network. The validity of this method was reviewed by a beam under moving load. When structure has damage, its state information can be extracted availably from high-order spectrum entropy of structural vibration, and it isn’t sensitive to noise. It can be used as eigenvectors of pattern recognition based on neural network.

scholarly journals Dynamic Equilibrium Equations in Unified Mechanics Theory

2021 ◽  
Vol 2 (1) ◽  
pp. 63-80
Author(s):  
Noushad Bin Jamal Bin Jamal M ◽  
Hsiao Wei Lee ◽  
Chebolu Lakshmana Rao ◽  
Cemal Basaran
Keyword(s):  
Energy Loss ◽  
Entropy Generation ◽  
Equilibrium Equation ◽  
Dynamic Equilibrium ◽  
Free Vibration Analysis ◽  
Newtonian Mechanics ◽  
Equilibrium Equations ◽  
Time Coordinate ◽  
Proposed Model ◽  
Laws Of Thermodynamics

Traditionally dynamic analysis is done using Newton’s universal laws of the equation of motion. According to the laws of Newtonian mechanics, the x, y, z, space-time coordinate system does not include a term for energy loss, an empirical damping term “C” is used in the dynamic equilibrium equation. Energy loss in any system is governed by the laws of thermodynamics. Unified Mechanics Theory (UMT) unifies the universal laws of motion of Newton and the laws of thermodynamics at ab-initio level. As a result, the energy loss [entropy generation] is automatically included in the laws of the Unified Mechanics Theory (UMT). Using unified mechanics theory, the dynamic equilibrium equation is derived and presented. One-dimensional free vibration analysis with frictional dissipation is used to compare the results of the proposed model with that of a Newtonian mechanics equation. For the proposed entropy generation equation in the system, the trend of predictions is comparable with the reported experimental results and Newtonian mechanics-based predictions.

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

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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