Logo SFB 871 Produkt-Regeneration
Logo: SFB 871
Logo SFB 871 Produkt-Regeneration
Logo: SFB 871
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A Inspection and condition assessment

Project Area A, “Inspection and condition assessment", focuses on the development of new methods for sensitive investigations of the condition of engines, the damage assessment of hot path e.g. turbine components, their base materials, and their coatings.

This forms the basis for localizing and diagnosing damage. It is also a basis for a the evaluation of the condition of individual engines and their components. This evaluation is required in order to plan regeneration processes individually, i.e. for each specific customer and each specific component and for acceptance testing after the regeneration has been carried out.  

The subprojects of project area A are:

A1Non Destructive Characterization of Turbine Blades
A2Multiscale Geometry Measurement
A3Evaluation of the Condition of a Jet Engine through Exhaust Jet Analysis
A4Influence of Combustion Chamber Defects on the Exhaust Jet
A5Dissembly in the Regeneration Path
A6Mixing and Combustor Signature



A1 Non Destructive Characterization of Turbine Blades

Non Destructive Characterization of Turbine Blades

Non Destructive Characterization of Coating and Material Conditions of Heavily Stressed Turbine Components
The work program includes the further development of the High Frequency Eddy Current Technology and High Frequency Induction Thermography with pulsed excitation for detection and classification of local defects and material changes in the component-multilayer system even for hard accessible and complex shaped turbine components, such as blisk-type compressor blades, during component inspection and quality assessment of repair procedures. For this purpose, it is planned to adapt the testing techniques to the new geometries and materials, to develop a remote field eddy current testing technique for determination of defect depth, and to automate as well as to integrate the test systems into the regeneration path.


A2 Multiscale Geometry Measurement

Multi-Scale Measurement System with Lasertracker Reference

Multiscale Measurement of Blade Geometries with Robot-Supported, Laser-Positioned Multi-Sensor-Techniques
The multiscale measurement system, which was developed within the first funding period of subproject A2, is expanded with a robust white-light interferometer for difficult-to-access geometries and a pericentric laser scanner for the fast and accurate measurement of edge geometries. An observer-based orientation estimation allows to convert the geometric data from the different optical sensors into a common coordinate-system and derive a holistic state model of the blade to be regenerated, which provides the database for the planning of the particular regeneration path.


A3 Exhaust Gas Analysis

Density and Temperature Field of an Exhaust Jet

Evaluation of the Condition of a Jet Engine through Exhaust Jet Analysis
In subproject A3 the tomographic reconstruction of density fields by the use of the optical background-oriented schlieren method (BOS) will be developed further to allow a better quantitative reconstruction of high density gradients. Thereby, a small number of viewing directions and the resolution of unsteady effects will also be considered. Furthermore, a method for an automated detection and assessment of coherent structures in an exhaust jet will be developed. A validation will be done by comparing the results of numerical simulations of an exhaust jet of an engine with experimental results obtained by equivalent BOS measurements.


A4 Influence of Combustion Chamber Defects on the Exhaust Jet (finished 2017)

Temperature at the Combustor Outlet in the case of a Failure of one Fuel Nozzle

Influence of Combustion Chamber Defects on the Exhaust Jet
Combustor-specific distortions and the resulting textures in the exhaust jet are mapped by numerical computation methods and in parallel detected with non-intrusive optical measurement techniques. The aim is to assign measurable exhaust gas patterns to distortions sources in the combustion chamber. The test chamber will be equipped with three individually controllable burners, allowing smaller combustion chamber defects to be examined. The tomographic BOS technique (see subproject A3) is complemented by measurement of the exhaust gas composition by use of the Tunable Diode Laser Absorption Spectroscopy.


A5 Dissembly in the Regeneration Path

Adaptable and Component-Protecting Disassembly in the Regeneration Path
Disassembly is a symptomatic contributor to uncertainty in the regeneration chain. Uncertainty is caused by product property changes, for example unknown solidification in the assembly joints, which is quantified in the sub-project A5 for planning disassembly forces. Solidification states, which are assigned to product loads such as operating hours, are learned by a model-based process. Furthermore, the states are decoupled from the product properties, to enable product-independent application. The adaptability of the process is addressed using a predefined impact procedure and a corresponding control system, which is part of a whole workplace concept including handling operation.


A6 Mixing and Combustor Signature

Temperature at the Combustor Outlet in the case of a Failure of one Fuel Nozzle

Impact of Mixing on the Signature of Combustor Defects
Combustor defects have an impact on the turbine performance and can be detected from the analysis of the exhaust gas pattern if the signature is sufficiently significant. Mixing processes reduce the information content, and impede the detection of defects in the exhaust path. In sub-project A6, possible combustor defects and the impact on the hot gas path will be simulated. The mixing processes will be analysed in detail on different laboratory burning chamber configurations with increasing complexity with experimental and numerical methods, such that a model approach for the complex turbulent mixing can be developed which will also be applicable to real jet engines.