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• input/output Remote Reset PLC/DCS or DTM-CFG To Danger To Alert Power Supply 1 Power Supply 1 TM0181 Cable TM0180
• Proximity Probe Figure 4. DTM10 system installation [22]. Air-admission system Figure 5 shows the air-admission system used to prevent the vortex effect at the Darca-1 HPP. With part 3 of the slip ring cover valve, shown in the upper section of Figure 5, the amount of air is admitted through the shaft. Normally, this valve is left fully open for maximum air admission. The Francis turbine section of the air-admission system is presented in Figure 6. Here, owing to the check valve in the lower part, airflow is directed upwardly in a one-way manner. Using a check valve in the lower section, pressured water is not permitted to flow through the turbines–generator shaft to the HPP building for any reason. Due to centrally injected air, the vortex oscillation amplitude is decreased; thus, hitting the draft tube is prevented. As a result, the turbine–generator group can operate more efficiently. Figure 7 shows the data from the turbine and generators used at the Darca-1 HPP. Either of the 2 units was operating while the vibration was being measured. Air admission system slip ring cover part 3 8x M10x33 Hex Head Screw 8x Hex Nut Air admission system slip ring cover part 1 8x M12x25 Hex Head Screw Air admission system slip ring cover O-ring d6 6x M16x50 Hex Head Screw Generator shaft A Figure 8. Water flow computer monitoring. Figure 8 presents the HPP SCADA system, software that was developed by Voith. The immediate turbine regulator controls, power, voltage, current, frequency, power factor, source water level control, main suction hatch controls, and check valve controls of the respective units (unit 1 and unit 2) can be seen and performed by the monitor. Figure 9. Francis turbine computer monitoring. In Figure 9, functions such as the monitoring and control of the spherical valve, tracking of the helix pressure, measuring of the turbine flow, positioning of the turbine hatch, speed check, and general monitoring can be performed. Figure 10. Francis turbine upper and lower bearings. In Figure 10, the control and monitoring of the generator’s upper and lower bearings, turbine bearings, and stator temperature can be observed. Figure 11 shows the upper section of a generator without an air-admission system. Figure 12 shows the upper section of a generator with an air-admission system mounted onto it. With the valve located on the top, the air-admission rate can be adjusted manually. Based on the experiments performed, this valve is adjusted to the fully open position in the case of the Darca-1 HPP. Figure 11. Generator without an air-admission system. Figure 12. Generator with air admission system. Results As in Darca-1, a generator that operates without an air-admission system can produce only 44 MW of power despite the fact that its capacity in the safe-vibration range is 49.5 MW. However, after installation of the air-admission system, the generator is now able to produce power under 49.5 MW at full load, within the safe vibration range. Figure 13 shows the power production of a generator without an air-admission system and bearing vibrations. Figure 13. Power production of a generator without an air-admission system and bearing vibrations. Figure 14 shows the measured rates of a system without an air-admission tool. These rates were obtained from the Darca-1 HPP databank, during a period of 3 min and 14 s, on 17.11.2009 at 1050 hours. Here, the significant rates shown in the cursor 1 and cursor 2 columns are circled. In the case of the system without air Figure 14. Measurement panel without air admission. admission, for the turbine bearing’s relative radial vibration, cursor 1 = 551.8519 ym and cursor 2 = 533.3333 ym; for the actual power, cursor 1 = 47.3047 MW and cursor 2 = 49.7583 MW. The steady-state actual power was measured as 44.0837 MW and the turbine bearing’s relative radial vibration was 475.9259 ym. Figure 15. Power production of a generator with an air-admission system and bearing vibrations. Figure 15 shows the vibration rates of the turbine–generator group with an air-admission system and the actual power produced by the generator. The data used in the study was obtained from the Darca-1 HPP databank during a period of 3 min and 42 s, on 07.05.2010 at 0845 hours. Based on the results, for the turbine bearing’s relative radial vibration, cursor 1 = 355.5555 ym and cursor 2 = 370.3704 ym; for the actual power, cursor 1 = 49.4023 MW and cursor 2 = 49.3393 MW. The steady-state actual power was measured as 49.5406 MW and the turbine bearing’s relative radial vibration was 372.2224 ym. Figure 16 shows the measured rates of a system with an air-admission tool. Figure 16. Measurement panel with air admission. Conclusion
• In this study, the effect of the Francis turbine air-admission system on both the efficiency of the generator’s power production and the vibration of the turbine has been investigated. Due to the air-admission system, it was determined that the actual power production increased by 11.11% and reached 49.5 MW, and the relative radial vibration of the Francis turbine decreased by 27.68%. Because the generator operates at full capacity, the power production was increased about 4,752,000 KWh annually. Considering that the vibration of the Francis turbine decreased by 27.68%, its contribution to the life cycle of the turbine is clear. This improvement will decrease power cutoffs and positively affect the periodic maintenance of the turbine. One of the most important parts of the turbines is their bearings; the lower the amplitude, the better the operating time of the bearings. It is obvious that the decrease in vibration will improve the operating time of the bearings for both the generator and the turbines. Acknowledgments The author would like to express his gratitude to Voith Hydro for granting permission to study the Darca-1 air-admission system and for sharing the technical photos of the system. Thanks are also given to Yapsan Enerji A.. for allowing the author to conduct a study at the Darca-1 HPP facilities and for their contributions and valuable information. References S. Pejovic, “Understanding the effects of draft tube vortex core resonance”, Hydro Review Worldwide, Vol. 8, pp. 28–33, 2000. O. Kirschner, A. Ruprecht, E. G¨ ode, “Experimental investigation of pressure pulsation in a simplified draft tube”, Proceedings of the 3rd IAHR International Meeting of the Workgroup on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, pp. 55–64, 2009. J. Paik, M. Sotiropoulos, M.J. Sale, “Numerical simulation of swirling flow in complex hydroturbine draft tube using unsteady statistical turbulence models”, Journal of Hydraulic Engineering, Vol. 131, pp. 441–456, 2005. R.H. Thicke, “Practical solutions for draft tube instability”, Water Power & Dam Construction, Vol. 33, pp. 31–37, 19 B. Papillon, J. Kirejczyk, M. Sabourin, “Atmospheric air admission in hydro turbines”, Hydrovision, paper 3C, 2000. R. Susan-Resiga, T.C. Vu, S. Muntean, G.D. Ciocan, B. Nennemann, “Jet control of the draft tube vortex rope in Francis turbines at partial discharge”, Proceedings of the 23rd IAHR Symposium on Hydraulic Machinery and Systems, paper F192, 2006. R. Susan-Resiga, S. Muntean, V. Hasmatuchi, F. Avellan, I. Anton, “Analysis and prevention of vortex breakdown in the simplified discharge cone of a Francis turbine”, Journal of Fluids Engineering, Vol. 132, doi:10.1115/1.4001486, 20 A. Bosioc, C. Tanasa, S. Muntean, R.F. Susan-Resiga, “Unsteady pressure measurements and numerical investigation of the jet control method in a conical diffuser with swirling flow”, Proceedings of the 25th IAHR Symposium on Hydraulic Machinery and Systems, 2010. A. Baya, S. Muntean, V.C. Cˆ ampian, A. Cuzmo, M. Diaconescu, G. Balan, “Experimental investigations of the unsteady flow in a Francis turbine draft tube cone”, 25th IAHR Symposium on Hydraulic Machinery and Systems, Vol. 12, doi:10.1088/1755-1315/12/1/012007, 2010.
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