Hydro abrasive Erosion in Hydro Power VOITH HYDRO

Transcription

1 Hydro abrasive Erosion in Hydro Power VOITH HYDRO Arvind Jaiswal Harshdeep Rana 1

2 Content IEC Erosion model and Recommendations Sediment erosion in Hydro Power Voith Hydro protective coating systems R&D work in coating lab Computation of erosion by CFD analysis 2

3 IEC Erosion Model (IEC abstract) Abrasion rate In order to demonstrate how different critical aspects impact the particle abrasion rate in the turbine, the following formula is considered Again, these functions are engineering approximations in order to Source: Source: JD SharmaPower Corporation, Bhutan obtain useful results for hydraulic machines. We then have the following formula. ds/dt = (particle velocity)3,4 C Khardness Ksize Kshape Kf /RSp Km Source: Sultan Alam Consultant, France 3

4 IEC Erosion Model. Source: Source: JD SharmaPower Corporation, Bhutan Source: Sultan Alam Consultant, France 4

5 IEC Erosion Model So the final, time integrated formula becomes: S = W3,4 PL Km Kf / RSp Recommendations. Thicker runner blades may result in decreased efficiency and Source: increased risk of vibrations from von Karman vortices, Source: JD SharmaPower Corporation, Bhutan Fewer runner blades (in order to improve the access to the blade surfaces for thermal spray surface treatment) may result in reduced cavitation performance,, Source: Sultan Alam Consultant, France 5

6 IEC Erosion Model Recommendations Abrasion resistant coatings may initially result in increased surface roughness, which may reduce the efficiency, Reduced runner blade overhang Source: may result in reduced Source: JD SharmaPower cavitation Corporation, Bhutan performance, which in turn may reduce the output that can be achieved for a turbine upgrade, Many abrasion resistance design features will increase the total cost of the power plant. Source: Sultan Alam Consultant, France 6

7 Characteristics of rivers Source: Source: JD SharmaPower Corporation, Bhutan Source: Sultan Alam Consultant, France 7

8 Characteristics of rivers Source: Source: JD Sharma Sultan Alam Power Corporation Consultant,, France Bhutan 8

9 Example: Facing plates & guide vanes 9

10 Sediments in rivers Source:R.K. Vishnoi, THDC Ltd 10

11 Problems Caused by Hydroabrasive Erosion Hydroabrasive Erosion leads to high costs due to... Mainenance and repairs Short maintenance intervals Loss of efficiency Loss of productive time Hydroabrasive erosion increases the economical risk of a hydro power project 11

12 Erosion in Fluids Terms and Definitions erosion = material loss Erosion Erosion- corrosion Hydro-abrasive erosion Cavitation Droplet impact 12

13 Hydro-Abrasive Erosion Mechanism Impacts of Particles lead to damages due to... Ploughing, cutting at small angles Hammering, fatigue cracking at large angles 13

14 Example of Hydro-Abrasive Wear 14

15 Example of Hydro-Abrasive Wear 15

16 Different Approaches for Sediment Management Civil works Desilting chambers Flushing Facilities Recommendations about performance Design of water reservoir Constructive means Type of machine Hydraulic layout Focus of Voith Hydro Protective Coatings Sediment monitoring 16

17 Voith Hydro Protective Coating Systems 17

18 Coating systems: Overview VH offers two different protective coatings Hard Coating (Diaturb ) Hard tungsten-carbides in ductile CoCr-matrix Soft Coating (Softurb ) Polyurethane based system 18

19 Hard coating: Diaturb Key figures: Material: WC-CoCr Process: HVOF Hardness: HV0.3 Thickness: 300 m Roughness: 5 7 m R a Bonding strength: > 60 MPa 19

20 Preparation of surface before Hard Coating Heating the job 3 2. Protecting surface not to be coated 3. Shot Blasting 20

21 Diaturb 532 coating Coating by robot of Head Covers Application: 2008 VSPO (Austria) Component: Head Cover Diameter: 2000mm 21

22 Diaturb 532 coating: SMX-project HVOF - coating applied on: Runner hub Runner blades Facing plates (up /low part) Discharge ring (up /low part) Guide vanes (prior to Softurb) Application: 1999/2000 Type: Kaplan Diameter: ~ 6100 mm Output: ~ 60 MW head: 30 m speed: 100 rpm 22

23 Diaturb 532 coating: Rangipo coated wear rings partially coated runner Application: 2001 Type: Francis Diameter: ~ 2500 mm Output: ~ 72 MW head: 210 m 23

24 Effect of hard coating: Wicket gates & facing plates Inspection after an operation time of h unprotected protected by Diaturb hard coating 24

25 Loss of efficiency [%] Efficiency loss [%] Effect of hard coating: Efficiency of Pelton runner 5 4,5 4 3,5 3 2,5 2 1,5 1 0,5 0 Pelton runner: uncoated Hardcoat Hardcoat + opt. geometry Sediment load [t] 25

26 Soft coating: Softurb Multi-component polyurethane coating system Application: 1. Grit blasting 2. Cleaning with solvent 3. Primer 4. Bonding agent 5. Polyurethane (multiple layers) 26

27 Application of sprayable Softurb Application of precoating (red) to ensure good adhesion Final result 27

28 Voith Philosopy of Coating Francis Turbine: Softurb 80 (polyurethane) Coating Runner Also we recommend Softurb 80 coating in stay vane and draft tube in high silt and cavitation prone area 28

29 Voith Philosopy of Coating Guide vane 29

30 Voith Hydro coating systems: Combined approach Both types of protective coating offers very good protection from hydroabrasive erosion Each type has it individual strengthes and weaknesses Softurb Pros - Very good abrasion protection - Application without heavy machinery - Local repairs and repairs on site possible (can be maintained before dissassembly is necessary) Cons - Sensitive to impacts of large object (stones) - Layer tolarences (± 0.5 mm) - Allowable head range Diaturb - Good abrasion protection - Tight layer tolerances - Mechanical strength - Difficult application on site - Applicability restircted by accessibility - Local repairs and repairs on site difficult - Cost 30

31 Pictures Application process: Left: Partial Diaturb coating Right: Softurb on top 31

32 R&D work in coating lab 32

33 Importance of coating in Voith Hydro We have laboratory specifically dedicated to testing of coatings at Voith Hydro Engineering Center (VHEC), Germany 33

34 Voith Hydro Coating Lab: Slurry pot test Operation: Finger shaped samples are rotating in a mixture of water and sand Focus: Evaluation of coatings / materials with regard to resistance against hydro abrasion 34

35 Slurry pot test results: Examples boundary conditions: - medium: water & quartz sand (5 wt%) - test duration: 240 h v rel v rel v rel Steel Diaturb on Steel Softurb on Steel 35

36 Evaluation of sediment characteristics Dorferbach (A) Marsyangdi (NP) Tobelbach (GER) Rangit (IN) Iskut (CAN) 36

37 Slurry pot test results for different sediments Tests performed with sieve fraction 125µm - 250µm Abrasion depends on mineralogy and particle shape and is therefore unique for every location 37

38 Slurry pot test results for different grain sizes sediment from Canadian river Significant influence of particle size observed 38

39 Development of hard coatings: Examinations and test setup Torch system Gas-operated HVOF (air-cooled) Gas-operated HVOF (water-cooled) Keroseneoperated HVOF Fuel Ethene Hydrogen Kerosene Powder GTV DIATURB.8 GTV DIATURB.8 GTV DIATURB.1 Composition WC-Co-Cr Particle size µm µm µm Designation Ethene Hydrogen Kerosene 39

40 Development of hardcoatings: Influence of type of fuel

41 Droplet Impact Test Rig Rotational speed of sample holder: approx /min water jets Circumferential speed of specimen (outermost position): approx. 72 m/s specimens Gravimetric and visual evaluation of test results 41

42 Quality of different HVOF-coatings WC-CoCr coating Same chemistry, thickness and hardness, but: different process Diaturb No. of impacts = Mio. 1.5 Mio. 2.1 Mio. 3 Mio. 42

43 Results of droplet impingement test: Volume loss compared to steel 43

44 Examinations in coating lab: Summary & Conclusions Burner type and energy medium used for depositing DIATURB coatings have a significant influence on the structure and the properties of the deposited layers. Although the coating characteristics for the gas-operated spray systems are a little more unfavorable, they can still be used to make highly wear-resistant coatings. Under hydro-abrasive exposure, all of the DIATURB layers were distinctly smoothed, wherein the different porosities have only little influence on the roughness values. The resistance of DIATURB coatings against droplet impingement is similar to steel (1.4313) or even better. 44

45 Computation of erosion by CFD analysis 45

46 CFD-modelling and particle tracking for hydro power components runner guide vanes stay vanes 46

47 scale (qualitative) Influence of particle size high wear low wear particle size: 100 µm particle size: 2000 µm => Calculation of local erosion depth 47

48 Flow (m^3/s) Influence of operating conditions t06 t01 t05 t03 Optimum t04 Head (m) t 06 t 04 48

49 Comparison with the real world: Inlet edge of Francis runner Appearance of erosion CFD-calculation 49

50 Comparison with the real world: Trailing edge of Francis runner Appearance of erosion => Very good match between CFD calculation and runner CFD-calculation showing pressure side 50

51 Computation of erosion: Summary & Conclusion Comparision of life time for different designs is possible with CFD and laboratory tests. Input from customer necessary regarding: expected sediment load over time expected particle size distribution for the accumulated sediment load intended operating conditions sediment sample from site for adjusting calculation using comparative laboratory tests 51

52 52