scholarly journals Comparative analysis of air and water flows in simplified hydraulic turbine models

2022 ◽  
Vol 2150 (1) ◽  
pp. 012001
Author(s):  
S G Skripkin ◽  
D A Suslov ◽  
I V Litvinov ◽  
E U Gorelikov ◽  
M A Tsoy ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Pressure Pulsation ◽  
Swirling Flow ◽  
Flow Characteristics ◽  
Hydraulic Turbine ◽  
Operating Conditions ◽  
Precessing Vortex Core ◽  
Wide Range ◽  
Turbine Runner ◽  
The Fourier Transform

Abstract This article presents a comparative analysis of flow characteristics behind a hydraulic turbine runner in air and water. Swirling flow with a precessing vortex core (PVC) was investigated using a laser Doppler anemometer and pressure pulsation sensors. The experiments were conducted on aerodynamic and hydrodynamic test rigs over a wide range of hydraulic turbine operating conditions. Part-load modes of hydraulic turbine operation were investigated using the Fourier transform of pressure pulsations obtained from acoustic sensors. The features of the swirling flow were shown for the range of operating conditions from deep partl-load to overload.

scholarly journals Manipulation of the swirling flow instability in hydraulic turbine diffuser by different methods of water injection

2018 ◽  
Vol 180 ◽  
pp. 02090 ◽  
Author(s):  
Pavel Rudolf ◽  
Jiří Litera ◽  
Germán Alejandro Ibarra Bolanos ◽  
David Štefan
Keyword(s):  
Swirling Flow ◽  
Flow Instability ◽  
Draft Tube ◽  
Water Injection ◽  
Hydraulic Turbine ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Necessary Condition ◽  
Vortex Rope ◽  
Wide Range

Vortex rope, which induces substantial pressure pulsations, arises in the draft tube (diffuser) of Francis turbine for off-design operating conditions. Present paper focuses on mitigation of those pulsations using active water jet injection control. Several modifications of the original Susan-Resiga’s idea were proposed. All modifications are driven by manipulation of the shear layer region, which is believed to play important role in swirling flow instability. While some of the methods provide results close to the original one, none of them works in such a wide range. Series of numerical experiments support the idea that the necessary condition for vortex rope pulsation mitigation is increasing the fluid momentum along the draft tube axis.

scholarly journals The Influence of Transient Regimes on Unsteady Vortex Phenomena in the Model of the Draft Tube of the Hydraulic Turbine

2019 ◽  
Vol 14 (4) ◽  
pp. 55-68
Author(s):  
D. A. Suslov ◽  
I. V. Litvinov ◽  
S. I. Shtork ◽  
E. U. Gorelikov
Keyword(s):  
Flow Rate ◽  
Swirling Flow ◽  
Draft Tube ◽  
Maximum Level ◽  
Hydraulic Turbine ◽  
Operating Conditions ◽  
Rotor Speed ◽  
Precessing Vortex Core ◽  
Transient Regimes ◽  
Partial Load

This article is devoted to study the swirling flow with the formation of the precessing vortex core (PVC) in the cone of the model of the draft tube of the hydraulic turbine. The experiments were carried out on the aerodynamic set-up both in stationary and in transient regimes of operation of the hydraulic turbine. The hydraulic turbine operating conditions were varied by continuously changing the flow rate at a constant rotor speed. The formation of the PVC in the flow and the maximum level of pressure pulsations in the regime modeling the partial load regime of a turbine are revealed. The boundaries of the occurrence of the PVC effect are determined with varying rotor speed and air flow rate. It was found that the dependence of the PVC lifetime in transition regimes correlate with the transition time. It was shown that the velocity profiles in transient conditions change quasistatically between the operation regime with partial loading of the turbine and the regime of the highest efficiency of the turbine.

Measurement of Unsteady Flow in Pump-Turbine for Hydropower Using PIV Method

2009 ◽  
Author(s):  
Nobuhiko Fukuda ◽  
Satoshi Someya ◽  
Koji Okamoto
Keyword(s):  
Rotational Speed ◽  
Velocity Measurement ◽  
Numerical Procedure ◽  
Hydraulic Turbine ◽  
Operating Conditions ◽  
High Time ◽  
Pump Turbine ◽  
Guide Vanes ◽  
Runner Blade ◽  
Wide Range

It is thought that the pressure fluctuation can occur due to the interaction between flow through guide vanes and flow into runner blades, resulting in a vibration of turbine and a blade cracking, in a hydraulic turbine operated in a wide range for flexible power demand. High accurate velocity measurement with high time/spatial resolution can help to clarify the mechanism of the interaction and to provide good experimental data for the validation of numerical procedure. So the aim of present study is to estimate the unstable velocity field quantitatively in the area between guide vanes and runner blades, using high time-resolved particle image velocimetry (PIV). Two types of velocity measurements were carried out, i.e., phase-locked measurement and high time sequential velocity measurement, in a pump-turbine model with 20 guide vanes and 6 runner blades. The characteristic of the flow field varied corresponding to the operating conditions such as flow rate and rotational speed. Opening angles of guide vanes were kept uniform. A clockwise vortex was generated at inside of the runner blade under smaller rotational speed. A counterclockwise vortex was separated at the backside of the runner blade under higher rotational speed. At any operating conditions, the velocity between guide vanes and runner blades oscillated periodically at the blade passing frequency.

scholarly journals Investigating the In-Flow Characteristics of Multi-Operation Conditions of Cross-Flow Fan in Air Conditioning Systems

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 959
Author(s):  
Weijie Zhang ◽  
Jianping Yuan ◽  
Qiaorui Si ◽  
Yanxia Fu
Keyword(s):  
Pressure Distribution ◽  
Flow Rate ◽  
Total Pressure ◽  
Air Conditioning ◽  
Pressure Pulsation ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Operating Conditions ◽  
Aerodynamic Noise ◽  
Cross Flow Fan

Cross-flow fans are widely used in numerous applications such as low-pressure ventilation, household appliances, laser instruments, and air-conditioning equipment. Cross-flow fans have superior characteristics, including simple structure, small size, stable airflow, high dynamic pressure coefficient, and low noise. In the present study, numerical simulation and experimental research were carried out to study the unique secondary flow and eccentric vortex flow characteristics of the internal flow field in multi-operating conditions. To this end the vorticity and the circumferential pressure distribution in the air duct are obtained based on the performed experiments and the correlation between spectral characteristics of multiple operating conditions and the inflow state is established. The obtained results show that when the area of the airflow passage decreases while the area of the eccentric vortex area gradually increases, then the airflow of the cross-flow fan decreases, the outlet expands, and the flow pattern uniformity reduces. It was found that wakes form in the vicinity of the blade and the tail of the volute tongue, which generate pressure pulsation, and aerodynamic noise. The pressure distribution along the inner circumference shows that the total minimum pressure appears in the eccentric vortex near the volute tongue and the volute returns near the zone. Moreover, it was found that the total pressure near the eccentric vortex is significantly smaller than that of the main flow zone. As the flow rate decreases, the pressure pulsation amplitude of the eccentric vortex region significantly increases, while the static and total pressure pulsation amplitudes are gradually increased. Close to the eccentric vortex on the inner side of the blade in the volute tongue area, total pressure is low, total pressure on the outside of the blade is not affected, and pressure difference between the inner and outer sides is large. When the flow rate of the cross-flow fan is 0.4 Qd, there is no obvious peak at the harmonic frequency of the blade passage frequency. This shows that the aerodynamic noise is caused by the main unstable flow.

Numerical Modeling of Air-Grass Flow and BPF Noise in Lawn Mowers

2007 ◽  
Author(s):  
Sergey Timushev ◽  
Alexandr Gamarnik ◽  
Anton Tsipenko
Keyword(s):  
Fluid Dynamics ◽  
Wave Equation ◽  
Pressure Pulsation ◽  
Particle Interaction ◽  
Numerical Procedure ◽  
Operating Conditions ◽  
Sound Power ◽  
Incompressible Medium ◽  
Modeling Procedure ◽  
Wide Range

The noise of domestic machines including lawnmowers be comes an urgent issue. As the technology matures, designers need better tools to predict performance and efficiency of these machines across a wide range of operating conditions and find optimal ways to reduce noise. Computational fluid dynamics is an increasingly powerful tool which enables designer to better understand all features of unsteady flow in these machines and to find optimal designs providing higher energetic characteristics, better cutting quality and lower pressure pulsation, vibration and noise. Cutting quality linked with evacuation of grass is a key lawnmower characteristic. Due to this fact application of two-phase (air-grass) lawnmower flow model is inevitable in a prediction procedure. The modeling procedure comprises determination of lawnmower average aerodynamic characteristics and CFD-CAA analysis by acoustic-vortex method to predict sound power data. This method is based on splitting the equations of compressible fluid dynamics into two modes — vortex and acoustic Computational approach applied for the vortex mode flow is a “moving body”-technique: The problem is solved in the absolute frame of coordinates and computational grid changes during the blade passing. Computations can be made in 4 stages: 1) Computation of the incompressible medium with getting average values of energetic parameters; 2) Computation of the incompressible medium for definition the source function of inhomogeneous acoustic-vortex wave equation; 3) Solution of the acoustic-vortex wave equation; 4) Computation of 2-phase flow. In the 3rd stage the pressure pulsation field can be represented like a sum of acoustic and vortex oscillation. Wave equation is solved relatively to pressure oscillation using an explicit numerical procedure. Zero pulsatory pressure is an initial condition for solution of the wave equation. The local complex specific acoustic impedance is used to define boundary conditions for the acoustical part of the pressure field. Thus the numerical procedure gives pressure pulsations field and sound power data on blade passing frequencies (BPF). For the 4th stage computations effective grass particle parameters are determined with accounting the stubble effect on flow parameters and particularities of grass particle interaction with rigid surfaces. Results of a lawnmower air-grass flow (grass particle trajectories and concentration) and corresponding BPF sound power data prediction are presented as an example of modeling procedure application.

scholarly journals Analysis of Internal Flow Characteristics of a Startup Pump Turbine at the Lowest Head under No-Load Conditions

2021 ◽  
Vol 9 (12) ◽  
pp. 1360
Author(s):  
Wei Wang ◽  
Xi Wang ◽  
Zhengwei Wang ◽  
Mabing Ni ◽  
Chunan Yang
Keyword(s):  
High Speed ◽  
Pressure Pulsation ◽  
Working Condition ◽  
Guide Vane ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Operating Conditions ◽  
Small Range ◽  
Pressure Balance ◽  
Pump Turbine

The instability of the no-load working condition of the pump turbine directly affects the grid connection of the unit, and will cause vibration and damage to the components of the unit in severe cases. In this paper, a three-dimensional full flow numerical model including the runner gap and the pressure-balance pipe was established. The method SST k-ω model was used to predict the internal flow characteristics of the pump turbine. The pressure pulsation of the runner under different operating conditions during the no-load process was compared. Because the rotation speed, flow rate, and guide vane opening of the unit change in a small range during the no-load process, the pressure pulsation characteristics of the runner are basically the same. Therefore, a working condition was selected to analyze the transient characteristics of the flow field, and it was found that there was a high-speed ring in the vaneless zone, and a stable channel vortex was generated in the runner flow passage. Analyzing the axial water thrust of each part of the runner, it was found that the axial water thrust of the runner gap was much larger than the axial water thrust of the runner blades, and it changed with time periodically. It was affected by rotor stator interaction. The main frequency was expressed as a multiple of the number of guide vanes, that is, vanes passing frequency, 22fn. During the entire no-load process, the axial water thrust of the runner changed slowly with time and fluctuated slightly.

Viscous Flow Analysis in Mixed Flow Rotors

1980 ◽  
Vol 102 (1) ◽  
pp. 193-201 ◽  
Author(s):  
I. Khalil ◽  
W. Tabakoff ◽  
A. Hamed
Keyword(s):  
Viscous Flow ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Laminar Flows ◽  
Operating Conditions ◽  
Field Analysis ◽  
Navier Stokes ◽  
Stream Channels ◽  
Wide Range

A method for analyzing the viscous flow through turbomachine rotors is presented. The field analysis is based on the solution of the full Navier-Stokes equations over the rotor blade-to-blade stream channels. An Alternating-Direction-Implicit method is employed to carry out the necessary numerical integration of the elliptic governing equations. The flow analysis may be applied to various types of turbomachine rotors. Preliminarily, only the case of laminar flows are considered in this paper. The flow characteristics within the rotors of a radial inflow turbine and a radial bladed compressor are investigated over a wide range of operating conditions. Excellent results are obtained when compared with existing experimental data. The method of this analysis is quite general and can deal with wide range of applications. Possible modification of the present study to deal with turbulent flow cases are also identified.

Unsteady Flow in a Centrifugal Compressor With Different Types of Vaned Diffusers

1988 ◽  
Vol 110 (3) ◽  
pp. 293-302 ◽  
Author(s):  
U. Haupt ◽  
U. Seidel ◽  
A. N. Abdel-Hamid ◽  
M. Rautenberg
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Reverse Flow ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Nonuniform Flow ◽  
Unsteady Pressure ◽  
Wide Range

Experiments were conducted to investigate the characteristics of self-excited flow oscillations in a high-performance centrifugal compressor system with a straight channel radial vaned diffuser. Fast response dynamic pressure transducers on the shroud wall and blade-mounted strain gages were used to identify the onset of the oscillations and their characteristics in space and time. In addition, flow characteristics near the shroud wall were visualized by an oil injection method, showing the extent of upstream directed reverse flow in the impeller range during significant unsteady flow compressor operation. Rotating nonuniform flow patterns were found in a wide range of operating speeds before the occurrence of surge. The number of lobes in the nonuniform flow patterns was dependent on the operating conditions and varied from two to four. Results of this experimental investigation were compared with those obtained from a previous investigation of the same compressor but with a cambered vane diffuser. Considerable similarity between the two configurations was found in the spatial distribution of the unsteady pressure field and in the frequencies of the fluctuations. The stability margin before the occurrence of surge and the operating regimes in which very intense pressure fluctuations were found were however different. In both cases, flow visualization techniques revealed the occurrence of reversed flow near the shroud wall of the impeller. Reverse flow extent up to the leading edge of the splitter blades systematically correlated with the occurrence of a nonuniform pressure pattern rotating with relatively high speed. Low rotational speed pressure patterns were observed when the extent of the reverse flow was up to the leading edge of the long blade. These different flow characteristics can be related to the occurrence of distinct rotating stall cell numbers. This result could be confirmed by unsteady pressure and blade vibration measurements.

Numerical Investigation on the Flow Characteristics of a Supercritical CO2 Centrifugal Compressor

2014 ◽  
Author(s):  
Hang Zhao ◽  
Qinghua Deng ◽  
Kuankuan Zheng ◽  
Hanzhen Zhang ◽  
Zhenping Feng
Keyword(s):  
Numerical Investigation ◽  
Centrifugal Compressor ◽  
Supercritical Co2 ◽  
Flow Characteristics ◽  
Low Pressure ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Vaned Diffuser ◽  
Compact Size ◽  
Wide Range

Supercritical CO2 closed-loop Brayton cycles offer the potential of better economical and practical efficiency due to its compact size and smaller compression work as compared with some traditional working fluids cycles, in which compressor is the key component. In this paper, the aerodynamic design and impeller aerodynamic optimization were conducted for a single stage centrifugal compressor with a combined vaneless and vaned diffuser, operating with CO2 slightly above the vapor-liquid critical point. The NIST REFPROP database was used for the computation of supercritical CO2 properties in design analysis and numerical investigation. The flow characteristics of the supercritical CO2 compressor were investigated by NUMECA FINE/Turbo. In order to weaken the low pressure regions, a vaneless diffuser was applied in this design, which would control and reduce the distribution differences of fluid thermodynamic states and increase fluid static pressure. The results indicate that there are no obvious low pressure regions occurring close to the leading edge of vaned diffuser. So it is observed in the design process that the vaneless diffuser could improve the aerodynamic performance of supercritical CO2 compressor. Compared with the operating conditions of the compressor only under centrifugal force, the pressure load from the aerodynamic analysis and the centrifugal load due to high speed of rotation were considered in the study of the stress and deformation of the structure of impeller by ANSYS/Mechanical. It can be concluded that supercritical CO2 provides unique properties for the compressor working process, which have a significant influence on finite element modeling in structural analysis. For the present design the maximum von Mises stress and total deformation are shown much smaller than the maximum allowable values, and thus the compressor could work in a wide range of operating conditions.

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