Abstract
The proposed paper describes the upgrading procedure of the six units installed at HPP Stejaru in Romania in the sixties of the last century. The power plant is furnished with two identical 55 MW units and four identical 28 MW units. The scope of the upgrading was same for all units, to install new runner and wicket gate assembly into the existing spiral case and draft tube. The paper is focused especially on the procedure of the hydraulic design of the new Francis type runner due to demanding request for unusually wide range of operation for such type of turbine. The most challenging was the condition of adoption of wicket gate height, which was insufficient regarding specific speed of the new runner. The first CFD computations confirmed that the standard design of the runner was not able to fulfill the expected parameters. Therefore, the automatic mathematical designer driven optimization process was applied. The results of the optimization iteration process were confirmed during development tests and finally approved by additional acceptance tests carried out at the neutral laboratory as was required in tender specification. The performance features of the new turbine were found as excellent especially applicable for wide range of operation heads and outputs. Even in the marginal operation there are not expected any troubles with the cavitation or excessive pressure pulsations and turbine vibrations. The manufacturing process of the new components is now in the progress.
Published Version
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