scholarly journals Effects of the Rates on the Performance and Pressure Pulsations of a High-Speed Pump with Straight Blade

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Hao Jia ◽  
Xianghui Su ◽  
Wei Jin
Keyword(s):  
Pressure Fluctuation ◽  
High Speed ◽  
Transient Flow ◽  
Flow Instability ◽  
Harmonic Wave ◽  
Dynamic Performance ◽  
Mechanical Vibration ◽  
Straight Blade ◽  
Blade Passing Frequency ◽  
Rotor Stator Interaction

Along with the crucial requirement for efficiency improvement in the cutting-edge petrochemical technology, the evaluation of the dynamic performance characteristics of high-speed pump is becoming increasingly important. It has become a main topic in the research of high-speed pump to minimize the pressure pulsation induced by the fluid in the pump body, so as to reduce the mechanical vibration. Although the research on the transient flow characteristic and pressure fluctuation of a high-speed pump with straight blades is of great significance, it has been seldom explored. In this work, the flow instability of a 16 straight-blade high-speed centrifugal pump is studied numerically at a rotational speed of 8500 rpm and flow rate of 3 m3/h. Results show that with the influence of rotor-stator interaction, time-domain pressure signals at the tongue show double peak characteristic, whereas a single peak characteristic exists at the diffuser wall. The pressure fluctuation near the tongue is reduced to approximately half of that at the volute wall by the water ring effect accompanied with the high-pressure factor. At the tongue region, the amplitude of the blade passing frequency is reduced by the unsteady flow, whereas the harmonic wave was increased at 2–4 times of the blade passing frequency.

Transient Flow Characteristics of Contra- and Co-Rotating Swirler Arrangements of an Industrial Combustor

2015 ◽  
Author(s):  
X. Wu ◽  
E. R. Norster ◽  
Gang Xie
Keyword(s):  
Transient Flow ◽  
Vortex Breakdown ◽  
Flow Instability ◽  
Mechanical Vibration ◽  
Flow Characteristics ◽  
Main Reaction ◽  
Pressure Oscillations ◽  
Lean Burn ◽  
Significant Discrepancy ◽  
Acoustic Characteristics

Many lean-burn combustors are prone to high levels of pressure oscillations resulting in early structural failure. These oscillations have their origins with the natural acoustic characteristics of the combustor flow/geometry and amplification and excitations factors associated with well-mixed flames. The coincidence of the frequency of these excitations with the mechanical vibration modes of the combustor may result in resonance and high cycle fatigue failure. Often with high levels of pressure oscillations the fuel system itself can become coupled driving the dynamics to higher levels. Thus detailed acoustic and mechanical vibration analysis of the combustor becomes important. This paper describes the numerically predicted transient flow characteristics of two configurations of DLN combustor double swirler in contra- and co-rotating arrangements with the sole difference being in the orientation of rotation of the inner nozzle airflow. Although much useful information has been obtained from the previous steady-state analysis, there remain many unresolved issues such as discrepancies of vortex breakdown and acoustic instabilities, which is also important for a final design selection. The transient analysis was performed for each configuration to compare flow instability and acoustic characteristics where the model includes the inlet air annulus, double swirler, main reaction zone and dilution duct. The studies indicate that there is a significant discrepancy in flow structures when the vortex breaks down between the two configurations. And there exists a strong interaction for the remaining swirl with the dilution jets, resulting in the hot core penetrating far downstream inside the transient duct in the co-rotating case. An FFT analysis indicates a significant discrepancy on main low acoustic frequencies and the magnitudes of oscillatory pressure.

scholarly journals The Action Mechanism of Rotor–Stator Interaction on Hydraulic and Hydroacoustic Characteristics of a Jet Centrifugal Pump Impeller and Performance Improvement

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 465
Author(s):  
Guo ◽  
Li ◽  
Zhang ◽  
Han
Keyword(s):  
Flow Field ◽  
Pressure Fluctuation ◽  
Transient Flow ◽  
Guide Vane ◽  
Hydraulic Performance ◽  
Action Mechanism ◽  
Optimization Scheme ◽  
Fluctuation Intensity ◽  
Blade Number ◽  
Rotor Stator Interaction

The aim of this study was to investigate the action mechanism of the rotor–stator interaction (RSI) on the transient flow field and hydrodynamic noise field inside the impeller of jet centrifugal pumps (JCPs) and optimize effects of the guide vane on the hydraulic and hydroacoustic characteristics of the impeller. The numerical method of CFD (computational fluid dynamics) coupled with CFA (computational fluid acoustics) was used to analyze the correlation between the guide vane and the flow/sound performances of the impeller. The orthogonal test method, with the hydroacoustic performance of the impeller taken as the objective, was used to optimize the structural parameters of the guide vane for the stability of the hydraulic performance of the JCP. The results show that the RSI leads to a significant increase in the hydroacoustic level of the impeller, but it is indispensable for improving the hydraulic performance of the pump. The RSI effect on the fluctuation intensity of the transient flow field inside the impeller is much more sensitive than the time-average, and the fluctuation intensity of the flow field is positively correlated with the vortex intensity inside the impeller. When the impeller geometry is constant, the evolution processes of the flow field inside the impeller are mainly related to the blade number of the guide vane; when the number of guide vanes is given, the RSI effect on the hydroacoustic characteristic of the impeller is characterized by a positive correlation between the total sound pressure level (SPL) and the fluctuation intensity of the flow field. The frequency spectrum characteristics of the hydroacoustic SPL of the impeller are not consistent with the pressure fluctuation characteristics inside the impeller. The pressure fluctuation characteristics are related not only to the blade number and speed of the impeller but also to its wake characteristics determined by the guide vane. The optimization scheme for the stable hydraulic performance of the JCP significantly reduced the total SPL of the impeller compared with the original scheme, which verifies the feasibility of using the weight matrix optimization method to obtain the global optimization scheme.

scholarly journals Correlation research of rotor–stator interaction and shafting vibration in a mixed-flow pump

2019 ◽  
Vol 39 (1) ◽  
pp. 72-83 ◽  
Author(s):  
Wei Li ◽  
Leilei Ji ◽  
Weidong Shi ◽  
Yongfei Yang ◽  
Muhammad Awais ◽  
...  
Keyword(s):  
Interaction Effect ◽  
Pressure Fluctuation ◽  
Pressure Pulsation ◽  
Mixed Flow ◽  
Time Frequency ◽  
Shaft System ◽  
Blade Passing Frequency ◽  
Axis Orbit ◽  
Rotor Stator Interaction ◽  
Flow Pump

In order to study the shaft system vibration of mixed-flow pump under rotor–stator interaction, the unsteady pressure fluctuation characteristics are measured and the rotor axis orbit obtained based on the Bentley 408 data acquisition system. The relationship between pressure fluctuation and vibration characteristics of shaft system at the blade passing frequency is analyzed. The results show that the pressure fluctuation amplitude is the largest and the rotor–stator interaction effect is the most obvious in the middle of the impeller. Along the direction of the main stream, the velocity energy is converted into pressure energy, the rotor–stator interaction effect is gradually weakened, and the main frequency of the pressure pulsation gradually turns from the 4 X frequency to the 1 X frequency of the impeller rotation frequency. The hydraulic stirring vibration and other factors lead to jagged sharp corners on the original axis orbit. The axis orbit of 1 X frequency is an ellipse with little difference between long and short axis while the 2 X frequency is the opposite, from which the existence of arcuate rotary whirl and misalignment phenomenon of the rotor can be judged. Combined with time–frequency characteristics of pressure pulsation, it can be found that the hydraulic imbalance has a great influence on the vibration of the shafting, while the rotor–stator interaction at the blade passing frequency takes the second place, which is the main factor of inducing the 4 X frequency vibration of the axis orbit. This study targets is that providing practical guidance for improving operation stability and preventing the vibration failure of the mixed-flow pump.

Experimental Study of Load Variations on Pressure Fluctuations in a Prototype Reversible Pump Turbine in Generating Mode

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Yuning Zhang ◽  
Ting Chen ◽  
Jinwei Li ◽  
Jixing Yu
Keyword(s):  
Pressure Fluctuation ◽  
Draft Tube ◽  
Pressure Fluctuations ◽  
Load Condition ◽  
Dominant Frequency ◽  
Dominant Mechanism ◽  
Blade Passing Frequency ◽  
Low Load ◽  
Rotor Stator Interaction ◽  
Spiral Casing

The characteristics of pressure fluctuations in a prototype reversible pump turbine (RPT) is investigated within a wide range of load conditions with a focus on the low-load condition (e.g., 25% of rated power) with the aid of pressure signals obtained at several typical recording points (i.e., spiral casing, vaneless space, draft tube cone, and draft tube elbow). Our findings reveal that at the low-load condition, the pressure fluctuation is quite significant (e.g., above 12% in terms of nondimensional values), especially in the vaneless space and spiral casing with the dominant frequency being the blade passing frequency. Furthermore, based on the characteristics of pressure fluctuation, the investigated load range is divided into three zones. For zone I (with low load), the amplitude of pressure fluctuation is highest and the dominant mechanism is the rotor–stator interaction in the vaneless space with the blade passing frequency. For zone II (with medium load), the amplitude of pressure fluctuation is less prominent (below 5%) and the dominant mechanism is the low-frequency fluctuations induced by the swirling vortex rope. For zone III (with high load), the amplitude of pressure fluctuation is quite limited (less than 3%) and the dominant mechanism is still the rotor–stator interaction but with the dominant frequency being the harmonics of blade passing frequency. Detailed examples for all three zones are given and discussed with quantitative descriptions of propagation mechanism of fluctuation.

Experimental and Numerical Analysis of Flow Instabilities in a Radial Fan

2014 ◽  
Author(s):  
Andreas Lucius ◽  
Andreas Lehwald ◽  
Dominique Thévenin ◽  
Gunther Brenner
Keyword(s):  
High Speed ◽  
Transient Flow ◽  
Suction Side ◽  
Computational Techniques ◽  
Unsteady Forces ◽  
Operation Conditions ◽  
Image Velocimetry ◽  
Rotor Stator Interaction ◽  
Open Issue ◽  
Computational Fluid Dynamics Cfd

Dynamic loads in turbomachines may lead to severe fluid induced vibrations, in particular, if resonance conditions are matched. The major sources of such unsteadiness are rotor/stator interaction, flow separation on the blade suction side at part-load and separation due to the curvature of the shroud. In the present work, some of these phenomena are investigated using computational techniques (Computational Fluid Dynamics - CFD) as well as novel measurement methods (High-Speed Particle Image velocimetry - PIV). The measurements provide a unique database of the velocity fields in an industrial impeller at various operation conditions. They are the base for validation of the computational methods. In view of the complexity of the separated, transient and turbulent flow field, this is still an open issue. Besides that, the analysis of the transient flow fields allows the determination of the “modes” of unsteady forces und thus, to shed some light on the sources of unsteadiness in the flow.

Dynamic Performance of High-Speed Electric Multiple Unit within Multi-Body System Simulation

2019 ◽  
Vol 12 (4) ◽  
pp. 339-349
Author(s):  
Junguo Wang ◽  
Daoping Gong ◽  
Rui Sun ◽  
Yongxiang Zhao
Keyword(s):  
High Speed ◽  
Rapid Development ◽  
Dynamic Performance ◽  
Body System ◽  
High Speed Railway ◽  
Evaluation Indexes ◽  
Actual Operation ◽  
Multiple Unit ◽  
The Stability ◽  
Multi Body

Background: With the rapid development of the high-speed railway, the dynamic performance such as running stability and safety of the high-speed train is increasingly important. This paper focuses on the dynamic performance of high-speed Electric Multiple Unit (EMU), especially the dynamic characteristics of the bogie frame and car body. Various patents have been discussed in this article. Objective: To develop the Multi-Body System (MBS) model of EMU, verify whether the dynamic performance meets the actual operation requirements, and provide some useful information for dynamics and structural design of the proposed EMU. Methods: According to the technical characteristics of a typical EMU, a MBS model is established via SIMPACK, and the measured data of China high-speed railway is taken as the excitation of track random irregularity. To test the dynamic performance of the EMU, including the stability and safety, some evaluation indexes such as wheel-axle lateral forces, wheel-axle lateral vertical forces, derailment coefficients and wheel unloading rates are also calculated and analyzed in detail. Results: The MBS model of EMU has better dynamic performance especially curving performance, and some evaluation indexes of the stability and safety have also reached China’s high-speed railway standards. Conclusion: The effectiveness of the proposed MBS model is verified, and the dynamic performance of the MBS model can meet the design requirements of high-speed EMU.

Dynamic Performance of HTS Maglev and Comparisons with Another Two Types of High-Speed Railway Vehicles

Cryogenics ◽  
2021 ◽  
pp. 103321
Author(s):  
Yuhang Yuan ◽  
Jipeng Li ◽  
Zigang Deng ◽  
Zhehao Liu ◽  
Dingding Wu ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
High Speed Railway ◽  
Railway Vehicles ◽  
Hts Maglev

scholarly journals High-Speed Elevator Car Air Pressure Compensation Method Based on Coupling Analysis of Internal and External Flow Fields

2021 ◽  
Vol 11 (4) ◽  
pp. 1700
Author(s):  
Lemiao Qiu ◽  
Huifang Zhou ◽  
Zili Wang ◽  
Shuyou Zhang ◽  
Lichun Zhang ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Iterative Learning Control ◽  
High Speed ◽  
Learning Control ◽  
Flow Fields ◽  
External Flow ◽  
Iterative Learning ◽  
Air Pressure ◽  
Coupling Analysis ◽  
Pressure Compensation

As the demand for high-speed elevators grows, the requirements of elevator performance have also developed. The high speed will produce strong airflow disturbances and drastic pressure changes, which is prone to cause passenger discomfort. In this paper, an elevator car air pressure compensation method based on coupling analysis of internal and external flow fields (IE-FF) is proposed. It helps to adaptively track the ideal air pressure curve (IAPC) inside the car and controls the air pressure fluctuation to improve the ride comfort of the elevator. To obtain the air pressure transient value in the elevator car, an IE-FF modeling method is proposed. Based on the IE-FF model, the air pressure compensation system is developed. To realize the air pressure compensation inside the car, an adaptive iterative learning control (A-ILC) algorithm is proposed, to eliminate the passengers’ ear pressing due to the severe air pressure fluctuation. To verify the proposed method, the KLK2 (Canny Elevator Co., Ltd., 2015, Suzhou, China) high-speed elevator is applied. The numerical experiment results show that the proposed method has higher tracking accuracy and convergence speed compared to the classical Proportion Integral Differential (PID) algorithm and the Proportion Integral-iterative learning control (PD-ILC) algorithm.

A Nonlinear Rail Vehicle Dynamics Computer Program SAMS/Rail: Part 1—Theory and Formulations

2009 ◽  
Author(s):  
Khaled E. Zaazaa ◽  
Brian Whitten ◽  
Brian Marquis ◽  
Erik Curtis ◽  
Magdy El-Sibaie ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Contact Element ◽  
Contact Forces ◽  
Simulation Code ◽  
Vehicle Performance ◽  
Normal Contact ◽  
Advantages And Disadvantages ◽  
High Speed Trains

Accurate prediction of railroad vehicle performance requires detailed formulations of wheel-rail contact models. In the past, most dynamic simulation tools used an offline wheel-rail contact element based on look-up tables that are used by the main simulation solver. Nowadays, the use of an online nonlinear three-dimensional wheel-rail contact element is necessary in order to accurately predict the dynamic performance of high speed trains. Recently, the Federal Railroad Administration, Office of Research and Development has sponsored a project to develop a general multibody simulation code that uses an online nonlinear three-dimensional wheel-rail contact element to predict the contact forces between wheel and rail. In this paper, several nonlinear wheel-rail contact formulations are presented, each using the online three-dimensional approach. The methods presented are divided into two contact approaches. In the first Constraint Approach, the wheel is assumed to remain in contact with the rail. In this approach, the normal contact forces are determined by using the technique of Lagrange multipliers. In the second Elastic Approach, wheel/rail separation and penetration are allowed, and the normal contact forces are determined by using Hertz’s Theory. The advantages and disadvantages of each method are presented in this paper. In addition, this paper discusses future developments and improvements for the multibody system code. Some of these improvements are currently being implemented by the University of Illinois at Chicago (UIC). In the accompanying “Part 2” and “Part 3” to this paper, numerical examples are presented in order to demonstrate the results obtained from this research.

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