Author: Prashant Malavade, Santhana G Babu, Luca Frosini, Simone Marchetti.

Abstract:

*In Gas Turbine design key important role is to establish proper clearance between rotating and statoric parts during operating conditions which controls the performance, cooling flow requirements, part performance etc., These clearances have to be optimized to meet the product requirements. Too tight the  clearance at assembly condition causes excessive rubbing during starting or shutdown of the gas turbine which could cause excessive heat generation and damage the rotating and statoric parts. In some case, rubbing can cause tip librations and damages to the flow path causing aero dynamic losses. Similarly, if clearance is large at assembly condition causes aerodynamic losses. In this paper describes the experience of Baker Hughes, a GE company (BHGE) in design of compressor case wherein different design options in casing design with and without considering external features / components are considered to have adequate clearance between rotating and statoric parts. It also describes the Heat shield design iterations which was provided on a compressor case to establish proper thermal response during transient operating conditions. This helps in providing adequate clearance without causing excessive rubs or too large clearance avoiding aerodynamic losses. During the course of designing heat shield, challenges encountered during development stage considering clearance, manufacturing aspects, assembly feasibility and part life capabilities like Low cycle fatigue, High cycle fatigue requirements would be discussed in the paper. As the Heat shield is subjected to high thermal gradient due to temperature difference in axial direction this paper describes how the heat shield is fixed to casing without causing stress raisers due to fixity. Constrained growth on the heat shield provides huge stresses beyond the material limit causing it to fail before the product requirement time period. To avoid constrained growth, this paper describes how the heat shield is connected to casing by different means are mentioned. It also describes the impact on frequency margin if there is not adequate fixity in heat shield design. Some of the design parameters like circumferential & axial ribs and intermittent stiffeners and its influence on stress by comparing against yield and on frequency margin with reference to potential driver are also discussed in this paper. It also incorporates the methods to control intersegment leakages and design features to avoid interface interference. Low cycle assessment with reference to different Manufacturing options of ribs connected to heat shield is analyzed. Simulation heat shield design using Finite Element modeling techniques and its best practices would also be dealt in this paper.*

Keywords: Clearance, LCF, HCF, Optimization


Design of Heat Shield for Compressor Case of Industrial Gas Turbine to Meet Clearance Requirement

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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