Research On The Operating Stability Of Francis Turbine

With the increase of unit capacity, size and rotational speed of the hydraulicgenerator in the large hydropower station, the problem of hydraulic instability on theFrancis turbo-generator sets has become more and more important during its designand operation. According to the instability problem of the hydraulic turbo-generator set, a greatdeal of research works have been done in the practice measure or the model test aboutthe draft tube pressure of the generator, and the low-frequency pressure-pulse causedby the water flow in the draft tube has been analyzed. Some improving measurementscorrespondingly on the damages of the draft tube have been suggested in Wan jia zhaihydropower station. As the destruction causing by self-vibration often appears, the damage part andlevel are very different in different hydropower generator during its operation. For along period, the understanding of the quality problem of the set installment andmaintenance is much lack at the generator stability. Therefore, the improvingapproach about the stability of the hydraulic generator has been investigated, that canavoid or alleviate the self-vibration of the generator. At present, there are no uniform evaluation standards about the operatingstability of the hydraulic turbo-generator set at home and overseas. Especially thehydraulic pressure-pulse of Francis turbine generator in the draft tube, the value?H / H is usually used to appraise the stability in the practice. It has proved that thesame value of ?H / H has different influence on the different water head during theoperating of hydraulic generator. All these make the value of ?H / H uncertainty.Then, the pressure-pulse of the operating hydropower generator has been discussedand investigated in this paper. According to the above, the usage of the evaluationparameter has been obtained for the operating stability. Based on the tests of the stability about 2# generator in Wan jia zhai hydropowerstation, some suggestion of the stability project hydropower generator has beenproposed. Though the practice measure of the stability in Wan jia zhai hydropower stationand the frequency analysis of the measuring data, the results showed that the vibrationin 2# set mainly was caused by the hydraulic elements. At last, some measurements toeliminating and decreasing the vibration are given.