A New Method for Determining the Aerodynamic Forces Arising in Turbine Seals

Abstract

The article presents an aerodynamic force calculation method that was developed and tested at the National Research University Moscow Power Engineering Institute’s (NRU MPEI) Department of Steam and Gas Turbines. By using the proposed method, it is possible to quickly estimate, as a first approximation, the nonconservative component of the aerodynamic force arising in turbine seals proceeding from the aerodynamic force value measured under steady-state conditions without resorting to conventional costly research methods. The possibility to calculate the aerodynamic force nonconservative component at any rotor rotation frequency under steady-state conditions is substantiated. The values of the aerodynamic force nonconservative component in the seal obtained using the new method according to the calculation expression proposed by A.G. Kostyuk were compared with the results of measuring this force for similar seal models carried out previously using the conventional methods: by means of a strain-gauge balance and from the readings in seal chamber drains. The new method for determining aerodynamic forces was then applied for estimating the blade row forces, which depend on the leak uniformity through the shroud seal and act on the R-26-17A annular turbine rotor cascade. The obtained values were compared with the data of studies carried out on the IT-1 experimental setup using the conventional method by means of strain-gauge measurements, and the comparison results have shown good agreement of the data. The proposed method makes it possible to obtain qualitatively and quantitatively valid results and can be used for comparing the seals having different configurations with respect to the nonconservative force component arising in them that can give rise to self-vibration of turbine machinery shaft lines. For perfecting the method, it is possible to use the models of rotor parts that do not need balancing and that are manufactured using inexpensive materials.