Numerical Calculation of the Process Parameters, which Optimise the Gas Turbine Blade Coating Process by Thermal Spraying, for given Spray Paths

• Research unit: COST
• Project number: C02.0021

Key words (English)

Gas turbine blading; coating; thermal spray; tbc; simulation; optimization

Research programs (English)

COST-Action 526 - Automatic Process Optimization in Materials Technology

Short description (English)

See abstract

Partners and International Organizations (English)

B, CZ, DK, FIN, F, D, H, PL, SI, CH, GB

Abstract (English)

The blading of a gas turbine has to be protected from the hot gas stream. This can be achieved by different techniques, such as cooling air, metallic coating or thermal barrier coating (TBC). The present project is concerned with the process of applying TBC on a turbine blade. Specifically, the project targets the following points: § The development of criteria and strategies for the optimization of the coating process, which include the coating thickness, porosity distribution and the total coating time as parameters of the objective function. § The development of methods for the optimization of a spray path for complex 3D shapes by taking into account equipment, process and tooling limitations. Offline simulation tool To achieve a prediction of coating thickness which is qualitatively right and quantita-tively within acceptable limits to enable an offline assessment of coating quality, se-lected spray parameter variations have been applied and the resulting coating thick-ness was measured by 3D scanning. In an optimization loop the deviation between measured spray result and simulator prediction was minimized, resulting in an im-proved set of simulation tool parameters. In parallel, the usability of the offline simulation tool was reworked to simplify the definition of a spray path for a given gas turbine blade/vane. In particular, this re-duces the number of input variables, enabling an improved manual operation as well as a more efficient numerical optimization. Optimization environment For baselining the simulator and for the offline spray path generation the same opti-mization software Java Optimization Environment (JOE) developed by ALSTOM (Switzerland) Ltd is applied. Optimization § Coating strategy This step aims at defining the most appropriate coating strategy. Considering the high number of variables in a spray path definition for a blade/vane, a reduction of variables is needed for both, easier manual input and for numerical optimization. To achieve this the surface to be coated is partitioned into subdomains, which can be treated individually. § Parametrization This step requires a parametrization of a spray path for each subdomain as defined in the coating strategy. This means that the possible spray paths have to be de-scribed in a mathematical form with a limited number of free parameters. An exam-ple for the spray path parametrization of a concave side airfoil was worked out.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C02.0021