The design of a low reaction turbine blade profiles was carried out to improve the steam flow efficiency. The blade profiles geometry design for both the stationary and moving blades and reprofiling of them are done using Vista ATBlade, according to the aerodynamic analysis results from the cascade analysis code MISES.
The original stator profile is aft-loaded, and the new one present in this paper is highly-aft-loaded (HAL) to depress the development of secondary flow further, while maintaining even lower profile loss and wider incidence angle tolerance. The newly designed moving blade is more robust compared with the original one, thus it has larger aspect ratio under the same blade section average stress level, and with better incidence tolerant capability as well.
The planar cascade air tests were first carried out to verify the stator profile loss improvement, with a decrease of energy loss coefficient of almost 0.8% obtained under the Reynolds number of about 1e6. Then the annular cascade air tests with fully 360 degrees stator blades installed were conducted to validate the reduction of endwall loss and the profile loss as well, and to measure the mass flow capability (real mass flow/ideal mass flow).
Finally, two three-stage tests for the original blades and the new one were developed to verify the improvement under real multi-stages flow conditions. All the stages for both tests are designed with the hub reaction of about 15%, without interstage swirl, in the design condition. The flow probes at upstream of first stage stator and downstream of last stage moving blade, the hydraulic dynamometer and the flowmeter are used to test the overall efficiency. Three traverse planes are located at the upstream, middle and downstream of the second stage to measure the flow properties using five hole pneumatic probes. The test results showed a increase of overall efficiency of about 1.5%.
The CFD simulations showed very good agreement of mass flow capability with the tests, for both the stator annular and multi-stage tests.
The application of the newly designed blade profiles in SanHe subcritical reheat 300MW steam turbine (16.7MPa/537°C/537°C) retrofit gives the final proof of the efficiency improvement. The measured efficiency showed remarkable performance, with an increase of efficiency of 1.5%–2.2% for both the HP and IP cylinder.