Session: 34-07 Turbomachinery Design

Paper Number: 151335

Cooling Performance Prediction of Turbine Blades and Vanes for Conceptual Design 

The first step of the development of aero engines, the preliminary design, is an iterative process that includes the major components and disciplines. The key design factors are determined in this phase, upon which the subsequent development process is built entirely. Therefore, a successful preliminary design is not only essential for meeting the requirements but also leads to a more qualitative design, a shorter overall design phase, and lower overall development costs.

For the preliminary mechanical design of turbine blades and vanes, only the most dominant damage and failure effects, such as creep, oxidation, and fatigue, are considered. To determine the lifetime of components, the material temperature is one key factor and, therefore, decisive for the following dimensioning and weight estimation.

Modern cooled turbine blades and vanes use internal multi-pass passages with turbulators, inlays for impingement flows, film-cooling holes with optimized shapes and angles, individual cooling solutions for the leading and trailing edges, and many more features to enhance the cooling performance. An exact calculation of the material temperature of such blades and vanes requires the consideration of the complex external and internal flow fields and boundary layers of the blades and vanes. Additionally, advanced cooling features such as turbulators, which actively influence the internal boundary layers, or film-cooling, which highly influences the external flow field, must be considered. Many geometrical and aerodynamical aspects of this calculation are not entirely determined in the preliminary design phase. The use of simplified methods is required.

The goal of the work presented in this paper is to develop a novel method to predict the cooling performance, the material temperatures, and the needed cooling air mass flows for turbine blades and vanes in the preliminary design phase. 

The method is not only intended for conceptual studies but aims to provide a practical approach that serves as a starting point for the detailed design of industrial design tools. 

The main goal of the method is to improve the overall mechanical preliminary design, including the sizing and mass estimation of cooled turbine blades and vanes.

The method uses the 0-dimensional approach of Holland and Thake, which is already used in the currently existing design process and describes the cooling performance with few technology parameters. This approach is extended by an automatic selection of a suitable cooling technique. The optimal cooling technique is a compromise between achieving heat transfer as high as necessary to reach the required component lifetime but as less advanced as possible to minimize cooling mass flow, pressure loss, costs, etc., which are only considered in the later phases of design. Each cooling technique is modeled by matching technology parameters. Some cooling techniques include the use of a thermal barrier coating to improve the cooling performance even further. The following mass flow estimation uses physical calculations instead of correlations. The calculation is extended to a 1-dimensional approach considering a radial main gas temperature distribution. The cooling design is done at the mechanical design point. The required cooling mass flow is then calculated for each operating point of the engine mission. 

The method’s results are compared with 3D-FEM heat transfer calculations used for later design phases and with the results of other cooling performance estimation methods. Sensibility studies are done to identify the major influences on the calculated material temperature, cooling mass flow and cooling performance. Moreover, the method is tested within the whole turbine preliminary design process to analyze its influences on the mass and dimensions.

The work in this paper was done in cooperation with MTU Aero Engines AG in the context of the mechanical preliminary design of turbines.

Presenting Author: Patrick Bachmann Technical University of Munich - Institute of Turbomachinery and Flight Propulsion

Presenting Author Biography: Patrick Bachmann is an aerospace engineer currently pursuing his PhD at the Technical University of Munich in collaboration with MTU Aero Engines AG. He holds a bachelor's degree in mechanical engineering from the Technical University of Darmstadt and a master's in aerospace from the Technical University of Munich. His research focuses on the mechanical preliminary design of turbines.

Authors:

Patrick Bachmann Technical University of Munich - Institute of Turbomachinery and Flight Propulsion
Marianne Reijerkerk MTU Aero Engines AG München
Nelli Steinkamp MTU Aero Engines AG München
Volker Gümmer Technical University of Munich - Institute of Turbomachinery and Flight Propulsion