Flow & thermal analysis of a turbine blade

Denis Yurchenko and Pavel Krukovsky - Institute of Engineering Thermophysics, Kyiv, Ukraine

 

Within a highly complicated gas-turbine there are few elements subjected to more extreme conditions than the turbine blade. Sitting behind the combustion chambers, the blades must not only be able to withstand extreme temperatures but also high rotational speeds.

In the drive to increase performance and so hold a competitive advantage over their rivals, gas turbine manufacturers must push turbine blades harder by increasing the range of temperatures and pressures they operate under. As the operating conditions become more extreme, it is important to be able to determine the maximum local temperatures and temperature gradients within the blade as well as the stress-strain fields to ensure failure does not occur whilst in operation.

The need for improved modeling techniques has, in recent years, paved the way for 3D CFD analysis and more specifically conjugate heat transfer methods (CHT) where the temperature field within the solid as well as the fluid is considered. By modeling both blade and flowfield simultaneously errors are reduced, along with timescales and costs, and the need for code to code coupling is reduced or removed. CD-adapco’s meshing technology also adds the capability for simultaneous and
conformal meshing of both blade and fluid so removing the need for mapping across non-conformal interfaces.

Fig:01 External and internal heat transfer coefficients (far left and middle) of the turbine blade with resulting temperatures shown on the right.

 

The implementation of 3D CFD in the modeling of turbines also allows for full configuration simulation with little or no simplification of the blade geometry. Traditional bespoke codes rely on simplified geometries and flow paths so reducing geometric accuracy.

(Right - Fig:02 Temperatures of the turbine blade as well as the primary gas and cooling flow paths).

Such complicated geometries rarely have experimental data for comparative and validation purposes; this is due to the extreme operating conditions. In this case the modeling methodology is validated against existing published work and then extended to the full 3D geometry. Further to this empirical relationships may be studied to provide further verification of the simulations results.

Numerous comparisons were carried out in the current study between a range of blade profiles and empirical and experimental data. It is shown that the results of the CFD calculations are of a high quality and to a good level of accuracy allowing multiple configurations to be studied and the geometry optimized. Key to the study is the optimization of the cooling system, the design of which is critical in preventing potentially catastrophic turbine blade failure.

Editors note:
due to an oversight, CD-adapco previously published some of the images from this article without crediting them to the Institute of Engineering Thermophysics. We apologize for this, and are happy to fully credit the authors of this work.