Partial Blockage Effects on Turbine Internal Swirl Cooling due to Particle Deposition

Authors

Xing Yang  - Xi'an Jiaotong University, China; University of Stuttgart, Germany
Florian Seibold - University of Stuttgart, Germany
Zhenping Feng - Xi'an Jiaotong University, China
Bernhard Weigand - University of Stuttgart, Germany

Abstract

Internal cooling passages of gas turbine components are inevitable to be partially blocked by the accumulation of atmospheric particulates that are ingested into the engine and carried with the secondary air flow when aircrafts encounter with volcanic ash clouds and take-off and land in an environment contaminated with sand and dust. Build-ups of those foreign particulates within the internal passages are known to cause a high risk of the failure of hot turbine components because the particle deposits could deteriorate overall thermal performance of the internal cooling configuration. In this study, fly-ash deposition effects within a swirl cooling system are modeled by partially clogging the swirl tube, which has not previously been documented in literature, to the authors’ knowledge. The swirl cooling system consists of a swirl generator section with two tangential jet nozzles and a swirl tube. Swirl number calculated by geometrical parameters of the swirl generator is 5.3. Three typical blockage cases with deposition blockage in the jet nozzles, in the swirl generator, and in the swirl tube are considered. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations of swirling flow through the partially-blocked swirl cooling system are performed at a constant mass flow rate of cooling air, which results in a Reynolds number of 1.0´105 based on the axial velocity of bulk flow in the swirl tube and tube diameter, and at a constant inlet-to-outlet pressure ratio, respectively. The partial blockage effects on swirl cooling are presented and discussed in terms of axial and circumferential velocities, swirl numbers, vorticities, pressure penalties, heat transfer, and overall thermal performance. In comparisons with a baseline swirl tube without blockages, the blockage at the jet nozzle throat helps to intensify the swirling flow and thus increases the heat transfer levels throughout the swirl tube, while the blockage in the swirl generator significantly dissipates the swirling flow, resulting in reduced overall thermal performance at this point. Although the blockage within the swirl tube disturbs the swirling flow downstream of the blockage, generating the lowest heat transfer levels, the swirling flow and heat transfer upstream of the blockage are intensified, on the contrary. When a constant pressure ratio is imposed at the nozzle inlet and swirl tube outlet, the mass flow rate of the cooling air through the swirl cooling system is reduced, somewhat, due to the blockage, but the overall thermal performance in the swirl tube with a blockage in the swirl generator section is still higher, relative to the baseline swirl cooling configuration. The aim of this work is to reveal the deposition effects on the special swirling flow behaviors and attempt to quantify the contribution of particle deposition positions within the swirl cooling system to its flow fields and thermal performance. The findings of this study are expected to provide basic knowledge of swirling flow integrated with deposition blockage in a swirl tube.