IEC TS 62882:2020
(Main)Hydraulic machines - Francis turbine pressure fluctuation transposition
Hydraulic machines - Francis turbine pressure fluctuation transposition
IEC/TS 62882:2020(E) which is a Technical Specification, provides pressure fluctuation transposition methods for Francis turbines and pump-turbines operating as turbines, including:
- description of pressure fluctuations, the phenomena causing them and the related problems;
- characterization of the phenomena covered by this document, including but not limited to inter-blade vortices, draft tube vortices rope and rotor-stator interaction;
- demonstration that both operating conditions and Thoma numbers (cavitation conditions) are primary parameters influencing pressure fluctuations;
- recommendation of ways to measure and analyse pressure fluctuations;
- identification of potential resonances in test rigs and prototypes;
- identification of methods, to transpose the measurement results from model to prototype or provide ways to predict pressure fluctuations in prototypes based on statistics or experience;
- recommendation of a data acquisition system, including the type and mounting position of model and prototype transducers and to define the similitude condition between model and prototype;
- presentation of pressure fluctuation measurements comparing the model turbine and the corresponding prototype;
- discussion of parameters used for the transposition from model to prototype, for example, the peak to peak value at 97 % confidence interval, the RMS value or the standard deviation in the time domain and the relation of main frequency and the rotational frequency in the frequency domain obtained by FFT;
- discussion of the uncertainty of the pressure fluctuation transposition from model to prototype;
- discussion of factors which influence the transposition, including those which cannot be simulated on the model test rig such as waterway system and mechanical system;
- establishment of the transposition methods for different types of pressure fluctuations;
- suggestion of possible methods for mitigating pressure fluctuation;
- definition of the limitations of the specification.
This document is limited to normal operation conditions. Hydraulic stability phenomena related to von Karman vortices, transients, runaway speed and speed no load are excluded from this document.
This document provides means to identify potential resonances in model test rigs and prototype turbines. Scaling-up resonance conditions are not treated in this document. When resonance exists, the transposition methods identified in this document do not apply. Under these conditions, the relationship between model and prototype pressure fluctuations cannot be determined.
This document is concerned neither with the structural details of the machines nor the mechanical properties of their components, so long as these characteristics do not affect model pressure fluctuations or the relationship between model and prototype pressure fluctuations.
General Information
Standards Content (Sample)
IEC TS 62882 ®
Edition 1.0 2020-09
TECHNICAL
SPECIFICATION
colour
inside
Hydraulic machines – Francis turbine pressure fluctuation transposition
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IEC TS 62882 ®
Edition 1.0 2020-09
TECHNICAL
SPECIFICATION
colour
inside
Hydraulic machines – Francis turbine pressure fluctuation transposition
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.140 ISBN 978-2-8322-8786-6
– 2 – IEC TS 62882:2020 © IEC 2020
CONTENTS
FOREWORD . 9
INTRODUCTION . 11
1 Scope . 12
2 Normative references . 13
3 Terms, definitions, symbols and units . 13
3.1 General terms and definitions . 13
3.2 Units . 13
3.3 Overview of the terms, definitions, symbols and units used in this document . 14
3.3.1 Subscripts and symbols . 15
3.3.2 Geometric terms and definitions . 16
3.3.3 Physical quantities and properties terms and definitions . 17
3.3.4 Discharge, velocity and speed terms and definitions . 17
3.3.5 Pressure terms and definitions . 18
3.3.6 Specific energy terms and definitions. 18
3.3.7 Height and head terms and definitions . 19
3.3.8 Power and torque terms and definitions . 20
3.3.9 Efficiency terms and definitions . 21
3.3.10 General terms and definitions relating to fluctuating quantities . 21
3.3.11 Fluid dynamic and scaling terms and definitions . 24
3.3.12 Dimensionless terms and definitions . 24
4 Description of pressure fluctuation phenomena. 25
4.1 General . 25
4.2 Pressure fluctuations overview . 30
4.3 General description of draft tube flow in Francis turbines . 32
4.4 Detailed description of pressure fluctuation phenomena . 34
4.4.1 Mode 1: Pressure fluctuation in high load . 34
4.4.2 Mode 2: Pressure fluctuation in best operation range. 35
4.4.3 Mode 3: Pressure fluctuation in upper part load . 35
4.4.4 Mode 4: Pressure fluctuation in part load . 36
4.4.5 Mode 5: Pressure fluctuation in deep part load . 38
4.4.6 Modes 6.a and 6.b: Rotor-stator interaction (RSI) pressure fluctuation. 39
5 Specifications of pressure fluctuation measurement and analysis . 41
5.1 General . 41
5.1.1 Overview . 41
5.1.2 Purpose of the measurements . 41
5.1.3 Procedures and parameters to record . 42
5.1.4 Locations of pressure fluctuation test transducers . 43
5.1.5 Data acquisition for pressure fluctuation measurements . 44
5.1.6 Transducers and calibration . 45
5.2 Pressure fluctuation on a model turbine . 45
5.2.1 General . 45
5.2.2 Homology and limitations . 46
5.2.3 Detailed procedures. 46
5.3 Special requirements and information for a prototype turbine . 48
5.3.1 General . 48
5.3.2 Source of information . 48
5.3.3 Important aspects . 48
5.4 Analysis, presentation and interpretation of results . 49
5.4.1 General . 49
5.4.2 Time-domain analysis . 49
5.4.3 Frequency-domain analysis . 50
5.4.4 Non-dimensional frequency and pressure . 50
5.4.5 Presentation and interpretation of pressure fluctuations . 50
6 Identification of potential resonances in test rig and prototype . 51
6.1 General . 51
6.2 Identify resonance in test rig . 53
6.3 Possible resonance and self-excited pressure fluctuation in prototype . 53
6.3.1 General . 53
6.3.2 Draft tube vortex related resonances and self-excited pressure
fluctuation in prototype . 53
6.3.3 Rotor-stator interaction (RSI) related resonance . 55
6.3.4 Resonance with fluctuation modes not treated in this document . 55
7 Transposition method and procedure . 56
7.1 General . 56
7.2 Parameters influencing transposition . 56
7.2.1 Model test head . 56
7.2.2 Thoma number . 56
7.2.3 Froude number . 57
7.3 Relevant quantities for transposition . 57
7.3.1 Fluctuation frequency . 57
7.3.2 Fluctuation amplitude . 57
7.4 Transposable types of fluctuations . 57
7.5 Statistical analysis of model and prototype transposition accuracy . 58
8 Mitigations . 59
8.1 Draft tube vortex phenomena . 59
8.1.1 General . 59
8.1.2 Draft tube fins . 59
8.1.3 Draft tube with a central column . 60
8.1.4 Air admission . 61
8.1.5 AVR or PSS parameter tuning . 62
8.2 Runner inter-blade vortex. 63
8.3 Blade interaction . 63
8.4 Operation restriction . 63
Annex A (informative) Example of pressure fluctuation records . 64
Annex B (informative) Typical pressure fluctuation transducers parameters for model
test . 83
Annex C (informative) Pressure transducer dynamic calibration . 84
C.1 Fast valve opening method . 84
C.2 Rotating valve method . 84
C.3 Electrical spark method . 85
Annex D (informative) Proposed remote pressure measurement fluctuation correction . 86
D.1 General . 86
D.2 Correction method theory . 86
D.3 Measuring and estimating tube frequency response . 87
– 4 – IEC TS 62882:2020 © IEC 2020
D.4 Pressure fluctuation correction . 89
D.5 Limitations . 92
Annex E (informative) Forced response analysis for Francis turbines operating in part
load conditions. 93
E.1 General . 93
E.2 Systematic methodology based on detailed modelling of hydroelectric power
plant .
...
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