Integrated OGV Design for an Aggressive S-Shaped Compressor Transition Duct

Abstract

Within gas turbines the ability to design shorter aggressive S-shaped ducts is advantageous from a performance and weight saving perspective. However, current design philosophies tend to treat the S-shaped duct as an isolated component, neglecting the potential advantages of integrating the design with the upstream or downstream components. In this paper such a design concept is numerically developed in which the upstream compressor outlet guide vanes are incorporated into the first bend of the S-shaped duct. Positioning the vane row within the first bend imparts a strong radial gradient to the pressure field within the vane passage. Tangential lean and axial sweep are employed such that the vane geometry is modified to exactly match the resulting inclined static pressure field. The integrated design is experimentally assessed and compared to a conventional non-integrated design on a fully annular low speed test facility incorporating a single stage axial compressor. Several traverse planes are used to gather five-hole probe data which allow the flow structure to be examined through the rotor, outlet guide vane and within the transition ducts. The two designs employ almost identical duct geometry, but integration of the vane row reduces the system length by 21%. Due to successful matching of the static pressure field, the upstream influence of the integrated vane row is minimal and the rotor performance is unchanged. Similarly the flow development within both S-shaped ducts is similar such that the circumferentially averaged profiles at duct exit are almost identical, and the operation of a downstream component would be unaffected. Overall system loss remains nominally unchanged despite the inclusion of lean and sweep and a reduction in system length. Finally, the numerical design predictions show good agreement with the experimental data thereby successfully validating the design process.

The Influence of Fan Root Flow on the Aerodynamic of a Low-Pressure Compressor Transition Duct

“…The ESS extend though the first bend of the duct such that at plane B the radial pressure gradient due to turning is small. This contrasts with previous studies (Walker et al [12][13][14]) where the OGV wakes have been subject to a strong pressure gradient which drives the low momentum wake fluid into the inner wall. This generates a pair of counter rotating vortices but also serves to re-energizes the inner wall boundary.…”

“…A schematic of the duct is shown in Fig. 3 where it is compared to the LU2 duct used in the previous work of Walker et al [13].…”

“…1. Phase 1 -pre-existing rotor from the work of Walker et al [13] which had a nominally flat total pressure profile, broadly representative of a typical IP compressor exit.…”

“…[3][4][5], Bailey and Carrotte [6], Bailey et al [7] studied the fundamental aerodynamics and the effect of compressor generated inlet conditions. Additionally, Ortiz-Duenas et al [8], Barker et al [9,10], Karakasis et al [11], and Walker et al [12][13][14] studied more aggressive ducts and improved integration with the compression system.…”

A New Approach to Designing the S-Shaped Annular Duct for Industrial Centrifugal Compressor

“…Marn et al [9] have carried out a detailed experimental investigation of the flow field development and its implications for the turbine duct performance. Walker et al [10] have shown that the flow characteristics are very dependent on the duct geometrical parameters.…”