ASME Turbo Expo 2018 – GT2018-75712

The desired reduction of secondary air consumption of gas turbines is especially challenging when the sealing of stator-rotor cavities is concerned, where it is necessary to guarantee integrity against hot gas ingestion. Sealing and thermal performance of gas turbine stator-rotor cavities are directly dependent on the rim configuration. This paper provides a CFD-based characterization of heavy-duty gas turbine wheel-spaces when dealing with real engine operating conditions and geometries. Focusing on the rim seal configuration, the geometrical arrangement of the ingestion-cavity, the buffer-cavity and the inner cavities were investigated to improve the ingress flow-discouraging behaviour. The study reveals that the most important geometrical parameters affecting the rim sealing effectiveness are those related to the ingestion-cavity. Moreover, an empirical model to predict the stator-rotor cavity sealing performance in off-design conditions was proposed. The model, that consists in an extension of a well-known literature approach, performed well at the analysed operating conditions, confirming to be an excellent tool for the early design phases. Finally, an investigation on the unsteady behaviour of the seal highlights a coupling with an acoustic mode of the cavity, suggesting possible reasons to justify the presence of rotating structures embedded into the cavity flow.

http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=2701085

https://www.researchgate.net/publication/327406498_Effect_of_Rim_Seal_Configuration_on_Gas_Turbine_Cavity_Sealing_in_Both_Design_and_Off-Design_Conditions

 

J. Turbomach 141(8) 2019 – Transaction of ASME Turbo Expo 2018

Impinging jet arrays are typically used to cool several gas turbine parts. Some examples of such applications can be found in the internal cooling of high-pressure turbine airfoils or in the turbine blade tip clearances control of aero-engines. The effect of the wall-to-jets temperature ratio (TR) on heat transfer is generally neglected by the correlations available in the open literature. In the present contribution, the impact of the temperature ratio on the heat transfer for a real engine active clearance control system is analyzed by means of validated computational fluid dynamics (CFD) computations. At different jets Reynolds number and considering several impingement array arrangements, a wide range of target wall-to-jets temperature ratio is accounted for. Computational results prove that both local and averaged Nusselt numbers reduce with increasing. An in-depth analysis of the numerical data shows that the last mentioned evidence is motivated by both the heat transfer incurring between the spent coolant flow and the fresh jets and the variation of gas properties with temperature through the boundary layer. A scaling procedure, based on the TR power law, was proposed to estimate the Nusselt number at different wall temperature levels necessary to correct available open-literature correlations, typically developed with small temperature differences, for real engine applications.

http://turbomachinery.asmedigitalcollection.asme.org/article.aspx?articleid=2729002

https://www.researchgate.net/publication/331855212_EFFECT_OF_TEMPERATURE_RATIO_ON_JET_IMPINGEMENT_HEAT_TRANSFER_IN_ACTIVE_CLEARANCE_CONTROL_SYSTEMS