Verification of Rotordynamic Design Using 1/5 Scaled Model Rotor of 270 MW-Class Gas Turbine Center-Tied Rotor

Gas turbine power generation is relatively minor in terms of pollutant emissions, such as nitrogen oxides or sulfur oxides, as compared to thermal power generation using coal or petroleum. This is because of the use of liquefied natural gas, known as an eco-friendly power generation solution. Large gas turbines used for power generation are suitable for the power load demanded by modern society, which fluctuates very much with respect to power consumption because it takes only about 10–20 min to reach the entire output from the start-up. A large gas turbine used for power generation is a rotating machine that features a high degree of difficulty in mechanical design due to its fast start-up characteristics, structural complexity, and high operating temperature, while also emphasizing stability. Customers are demanding operational reliability as a prerequisite before evaluating the performance of a gas turbine. It is very important to design and verify the rotor dynamics sufficiently and accurately from the design stage prior to fabrication in light of that it is very difficult to change the rotor dynamics characteristics once the design is completed and finished. Many researchers are trying to improve the design completeness, but the researches that actually design and verify the power generation gas turbine are limited only to a few manufacturers with the original technology, so there is little verification of actual gas turbine. In this paper, rotor dynamics analysis and verification of a 270 MW class DGT-300H gas turbine rotor newly developed by DHI. To verify the center tie-rod type rotor design of a large gas turbine for power generation, which was conceptually designed using in-house design tools, a 1/5 scaled model was designed by applying the dynamic scaling law. In order to verify the suitability of the applied tie-rod design, the characteristics of the variation of the natural frequency with the variation of the pre-tightening force were tested in order to confirm the dynamic proper pre-tightening force. The design of the scaled model rotor was created, the model was designed and fabricated, and the natural frequencies were analyzed and tested to confirm the validity of the design method and the suitability of the analysis results. After the design of the large gas turbine rotor for 270 MW class power generation, the natural frequencies of the rotor before the blade installation were analyzed and the suitability of the design was verified by implementing a vibration test of the rotor before blade installation.