Performance of a Turbine Rim Seal Subject to Rotationally-Driven and Pressure-Driven Ingestion

Abstract

This experimental study considered the performance of a chute rim seal downstream of turbine inlet guide vanes (but without rotor blades). The experimental set up reproduced rotationally-driven ingestion without vanes and conditions of pressure-driven ingestion with vanes. The maximum rotor speed was 9000 rpm corresponding to a rotational Reynolds number of 3.3x106 with a flow coefficient of 0.485. Measurements of mean pressures in the annulus and the disc rim cavity as well as values of sealing effectiveness deduced from gas concentration data are presented. At high values of flow coefficient (low rotational speeds), the circumferential pressure variation generated by the vanes drove relatively high levels of ingestion into the disc rim cavity. For a given purge flow rate, increasing the disc rotational speed led to a reduction in ingestion, shown by higher values of sealing effectiveness, despite the presence of upstream vanes. At U_ax/((Ob))="0.485" , the sealing effectiveness approached that associated with purely rotationally-driven ingestion. A map of sealing effectiveness against non-dimensional purge flow summarises the results and illustrates the combined rotational and pressure-driven effects on the ingestion mechanism. The results imply that flow coefficient is an important parameter in rim sealing and that rotational effects are important in many applications, especially turbines with low flow coefficient

Flow and Ingestion in a Turbine Disc Cavity under Rotationally-Dominated Conditions

“…The results of an investigation of the disc pumping effect in a turbine disc cavity with a chute rim seal arrangement are presented in this paper extending the preliminary study by Bru Revert et al [9]. The effect of annulus pressure asymmetries created by the presence of NGVs in the gas path is compared by Bru Revert et al [1] to the results of this study. The sealing performance is assessed based on pressure measurements and values of sealing effectiveness derived from readings of gas concentration in the absence of external flow and with an axial axisymmetric annulus flow.…”

“…This investigation focuses on the performance of a chute rim seal with no blades and vanes in the annulus, such that ingestion is expected to be driven by the effects of rotation. Bru Revert et al [1] showed that this scenario is relevant for high pressure turbines at low flow coefficients.…”

“…Chew's correlation could be fitted to different seal geometries by adjusting the empirical constant k which indicates the ability to prevent ingestion of each rim seal design. The model is detailed in Equation (1), where U m is the mean flow velocity through the rim seal, Ω is the angular speed and b is the rotor disc radius.…”

AIAA Propulsion and Energy 2021 Forum

“…Beard et al (2017) upgraded its capability to study the secondary air system with focus on turbine stator-rotor cavities. Recently, Bru-Revert et al (2021) redesigned the air feed supply system to allow for steady state long duration tests in a reduced span gas path to investigate the sealing performance of the chute rim seal arrangement of the original ORF. The modularity of the modified ORF and the refinement of the cavity instrumentation enabled the study of different mechanisms of ingestion through vaneless and vaned gas path configurations.…”

“…The rotor disc dynamic pressure at the hub was used to non-dimensionalise the pressure. CFD results are compared with the experimental data available from Bru-Revert et al (2021). Experimental results reported for the vaneless configuration in were obtained for a non-dimensional sealing flow ratio of 𝑈 m /(Ωb) = 0.04, and rotational Reynolds number Re θ ~ 3.3E+06.…”