OLKILUOTO LP TURBINE EXHAUST PERFORMANCE ENHANCEMENT PROGRAMME

摘要

Teollisuuden Voima Oy (TVO) awarded Alstom a contract to retrofit the eight low pressure turbines on units 1 and 2 of their nuclear power station at Olkiluoto, Eurajoki, Finland in May 2007. The unit 1 turbines were installed during the 2010 annual outage, which won the international "Outage of the year" award in a competition organised by Nuclear Engineering International Magazine. The units have been uprated approximately 30% since initial plant commissioning, and the cooling-water pumps were upgraded at the same time as the turbine retrofit, so that the steam volumetric flow through the diffuser and hood has increased significantly. Following the installation of the Unit 1 turbines it was decided to carry out a further performance enhancement program, as opportunities were identified to reduce the losses in the turbine diffuser/hood system at low condenser pressures. Alstom, working together with TVO, conducted an extensive study of the flow conditions in the diffuser, hood and ductwork between the turbine last stage blade and the condenser. The study included a full audit of the geometry including structural support features; steam extraction pipework and steam bypass dump tubes. The complete geometry was modelled both in several CFD calculation domains, from 2D to full 3D, and in a representative model turbine at Alstom’s R&D facilities. Several candidate design features were identified with potential to improve the performance. The candidates were evaluated and optimised using advanced CFD tools, and the most promising verified in the model turbine; a total of 27 configurations were tested in a four month test campaign. A number of improvement features were finally selected, mechanically designed and manufactured in time for application on unit 2 in 2011. The performance tests on the second unit indicate that the enhancement features led to a performance improvement of circa 5 MW per unit, which was consistent with predictions and the model turbine tests. This paper describes the approach adopted during the performance enhancement program, the selected design features, and some interesting enhancement features that were not finally selected. The results of the verification are also presented. Verification was performed both in the model turbine and through measurements taken on unit 2 after the installation on site, using special instrumentation installed during the outage.