Aero Engines

AG TURBO 2020 - COORETEC 3.1.4 -

Optimization of Secondary Air System Flows in Different Operating Conditions

The enhancement of thermal efficiency of gas turbines comes along with an increase of turbine entry temperature. This trend demands high efficient cooling of turbine discs and blades as well as reliable sealing of the internal disc space against hot gas ingestion from the annulus. These cooling and sealing mass flows are provided by the secondary air system (SAS). Due to the fact that these flows are taken from the primary cycle after compressor work is added to the fluid, the SAS causes losses in the whole engine’s efficiency.

Facing different requirements in each operating point, the typically fixed SAS of an aero engine is designed to worst-case conditions to guarantee engine’s safety at all times. Hence, those mass flows considerably exceed the requirements in a far scope of the operational range. The resulting significant efficiency losses could be reduced by a novel flexible SAS in order to raise the engine’s efficiency and reduce the fuel consumption.

This project’s aim is the development of a method, which allows an estimation of the impact of variable secondary air flows on whole engine’s behavior. Considering this as the elementary design tool of a flexible SAS, a simulation environment is to be established which optimizes secondary air flows in each operating point. Therefore a multidisciplinary procedure is necessary: A detailed 1D-CFD simulation of the SAS will be coupled with a full-thermodynamic simulation of the engine’s cycle (synthesis model), providing the air system’s boundary conditions. Hereon additional models will be built up to ensure the air system’s customers critical requirements, e.g. cooling of turbine blades and discs, and to analyze the effects of optimized mass flows to the whole engine, e.g. their impacts on compressor-stability, lifetimes or changes in SFC.

Advanced work packages will focus on the technical feasibility of flexible SAS. For this purpose the simulation will be extended by characteristics of self-regulating flow devices (fluidics).

This method addresses both aero-engines and stationary gas-turbines, although with differing boundary conditions. To allow easy application of this method to all partners within AG TURBO, the used simulation software is either commercial or freeware, whereat the simulation-environment’s code is designed for easy implementation of in-house-software or extension with further modules.

Excerpt of applied software:

  • NetBeans (simulation environment)
  • GTlab (synthesis model)
  • Flowmaster (SAS model)

Person of contact: Dr.-Ing. Dominik Woelki

The research project is funded by the Federal Ministry for Economic Affairs and Energy as well as the industrial partner Rolls-Royce Germany, 2012/2016


Prof. Dr.-Ing.

Dieter Peitsch

Institute of Aeronautics and Astronautics

+49 30 314-22878

+49 30 314-79448



Woelki, D.; Peitsch, D.
Betriebspunktabhängige Kühlluftführung für Gasturbinen
August 2016


Woelki, D.; Peitsch, D.
Modellierung variabler Sekundärluftsysteme zur Bewertung ihrer Auswirkungen auf das Gesamtsystem Gasturbine
In Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Editor
September 2014