New, detailed flow field measurements are presented for a very large low-speed cascade representative of a high-pressure turbine rotor blade with turning of 110deg and blade chord of 1.0m. Data were obtained for tip leakage and passage secondary flow at a Reynolds number of 4.0×105, based on exit velocity and blade axial chord. Tip clearance levels ranged from 0% to 1.68% of blade span (0% to 3% of blade chord). Particle image velocimetry was used to obtain flow field maps of several planes parallel to the tip surface within the tip gap, and adjacent passage flow. Vector maps were also obtained for planes normal to the tip surface in the direction of the tip leakage flow. Secondary flow was measured at planes normal to the blade exit angle at locations upstream and downstream of the trailing edge. The interaction between the tip leakage vortex and passage vortex is clearly defined, revealing the dominant effect of the tip leakage flow on the tip end-wall secondary flow. The relative motion between the casing and the blade tip was simulated using a motor-driven moving belt system. A reduction in the magnitude of the undertip flow near the end wall due to the moving wall is observed and the effect on the tip leakage vortex examined.
An introduction is given to a new rotating wheelspace test vehicle known as the GE Hot Gas Ingestion Rig (HGIR). This scaled 1.5 stage turbine rig is configured similar to a current generation heavy duty gas turbine. It has a broad spectrum of measurement capability, including radial and circumferential ports for CO2 measurements that are used to measure the sealing effectiveness from candidate rim seal geometries. Engine-matched conditions are presented in a non-dimensional form that demonstrate the value of this fully capable test facility, including static pressure signatures at stage 1 nozzle exit, exit Reynolds number, exit Mach number and rotational Reynolds number. This paper also provides details of the operating conditions and assessment of a thermal steady-state condition achieved consistently throughout each test. Part I of this two-part paper focuses on the geometric details of this new state-of-the-art wheelspace rig, the measurement capabilities currently available and planned, and the results from the baseline geometry. The test data from this test vehicle are used to validate reduced order models, including unsteady CFD models. Details of the CFD modeling and validation are presented in the Part II paper Ding et al. [1]. Measurement uncertainties for all key parameters as well as the repeatability of the test rig to reproduce test conditions are presented to demonstrate the rigor taken in the design and operation of this testing facility.
High resolution Nusselt number distributions were measured on the blade tip surface of a large, 1.0 m chord, low-speed cascade representative of a high-pressure turbine. Data were obtained at a Reynolds number of 4.0×105 based on exit velocity and blade axial chord. Tip clearance levels ranged from 0.56% to 1.68% design span or equally from 1% to 3% of the blade chord. An infrared camera, looking through the hollow blade, made detailed temperature measurements on a constant heat flux tip surface. The relative motion between the endwall and the blade tip was simulated by a moving belt. The moving belt endwall significantly shifts the region of high Nusselt number distribution and reduces the overall averaged Nusselt number on the tip surface by up to 13.3%. The addition of a suction side squealer tip significantly reduced local tip heat transfer and resulted in a 32% reduction in averaged Nusselt number. Analysis of pressure measurements on the blade airfoil surface and tip surface along with particle image velocimetry velocity flow fields in the gap gives an understanding of the heat transfer mechanism.
Fundamental test data for different rim seal geometries have been obtained from the Hot Gas Ingestion Rig (HGIR), a scaled 1.5-stage turbine rig configured from a current generation heavy duty gas turbine. With well-controlled operating conditions the rig has provided valuable sets of data for CFD tool validation. Part I of this work [1] introduced details on the HGIR design and test data summary from selected rim seal configurations and test conditions. In this study, Part II, CFD simulations were carried out on the baseline test configuration, and different modeling approaches were compared to identify and validate a “reduced-order” CFD methodology, i.e. CFX analyses using the k-ε model with scalable wall function. The results show steady state CFD simulation to be incapable of predicting the ingestion levels observed from rig data. However, unsteady solutions using a two-vane/four-blade sector model including a stator-rotor domain interface showed ingestion over the outer rim seal that was in reasonably good agreement with test data. Good agreement was also obtained on pressure distributions in the circumferential direction. The identified “reduced-order” CFD modeling methodology demonstrated enough sensitivity to differentiate between sealing geometry variations, and thus can be applied to guide rim seal design.
New, detailed flow field measurements are presented for a very large low-speed cascade representative of a high-pressure turbine rotor blade with turning of 110 degrees and blade chord of 1.0 m. Data was obtained for tip leakage and passage secondary flow at a Reynolds number of 4.0 × 105, based on exit velocity and blade axial chord. Tip clearance levels ranged from 0% to 1.68% of blade span (0% to 3% of blade chord). Particle Image Velocimetry (PIV) was used to obtain flow field maps of several planes parallel to the tip surface within the tip gap, and adjacent passage flow. Vector maps were also obtained for planes normal to the tip surface in the direction of the tip leakage flow. Secondary flow was measured at planes normal to the blade exit angle at locations upstream and downstream of the trailing edge. The interaction between the tip leakage vortex and passage vortex is clearly defined, revealing the dominant effect of the tip leakage flow on the tip endwall secondary flow. The relative motion between the casing and the blade tip was simulated using a motor-driven moving belt system. A reduction in the magnitude of the under-tip flow near the endwall due to the moving wall is observed and the effect on the tip leakage vortex examined.
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