Mechanism of the Interaction of a Ramped Bleed Slot With the Primary Flow

2005 ◽  
Author(s):  
B. A. Leishman ◽  
N. A. Cumpsty
Keyword(s):  
Static Pressure ◽  
Pressure Field ◽  
Computational Study ◽  
Large Fraction ◽  
Rear Surface ◽  
Stagnation Pressure ◽  
Stream Velocity ◽  
Compressor Cascade ◽  
Primary Flow ◽  
Blade Passage

An experimental and computational study of the ramped bleed slot in a compressor cascade is presented. The geometry is a circumferential slot downstream of the stator blade trailing edge, with endwall ramps inside the blade passage, and the paper builds on work previously reported for different bleed off-take geometries [1, 2]. The strong interaction between any bleed slot and the primary flow through the cascade can be strong, thereby causing the levels of loss and blockage in the primary flow leaving the blade passage to be increased at some bleed flow rates. Radial flow into the bleed slot is highly non-uniform because the blade-to-blade pressure field causes flow to enter the bleed slot preferentially where the static pressure is high, and to spill out into the primary flow where the static pressure is low. The mechanism for the ramped bleed slot is different from that described in the earlier papers for other geometries. For the ramped bleed slot a static pressure field, with large variations of static pressure in the circumferential direction, is set up in the slot because the endwall flow entering the slot has higher stagnation pressure downstream of the pressure surface than downstream of the suction surface of the upstream blades. The flow entering the slot with high stagnation pressure is brought to rest in a stagnation point on the downstream surface of the slot, and the consequent variation in static pressure on the rear surface sets tangential and radial components of velocity which are a large fraction of the free-stream velocity. As well as demonstrating the mechanism for the flow behaviour, the paper presents results of experiments and calculations to demonstrate the behaviour and gives guidance for the design of bleed slots by stressing the fundamental features of the flow.

Mechanism of the Interaction of a Ramped Bleed Slot With the Primary Flow

2006 ◽  
Vol 129 (4) ◽  
pp. 669-678 ◽  
Author(s):  
B. A. Leishman ◽  
N. A. Cumpsty
Keyword(s):  
Static Pressure ◽  
Pressure Field ◽  
Computational Study ◽  
Flow Behavior ◽  
Rear Surface ◽  
Stagnation Pressure ◽  
Compressor Cascade ◽  
Primary Flow ◽  
Freestream Velocity ◽  
Blade Passage

An experimental and computational study of the ramped bleed slot in a compressor cascade is presented. The geometry is a circumferential slot downstream of the stator blade trailing edge, with endwall ramps inside the blade passage, and the paper builds on work previously reported for different bleed off-take geometries (Leishman et al., 2007, ASME J. Turbomach., 129, pp. 645–658; Leishman et al., 2007, ASME J. Turbomach., 129, pp. 659–668). The strong interaction between any bleed slot and the primary flow through the cascade can be strong, thereby causing the levels of loss and blockage in the primary flow leaving the blade passage to be increased at some bleed flow rates. Radial flow into the bleed slot is highly nonuniform because the blade-to-blade pressure field causes flow to enter the bleed slot preferentially where the static pressure is high, and to spill out into the primary flow where the static pressure is low. The mechanism for the ramped bleed slot is different from that described in the earlier papers for other geometries. For the ramped bleed slot a static pressure field, with large variations of static pressure in the circumferential direction, is set up in the slot because the endwall flow entering the slot has higher stagnation pressure downstream of the pressure surface than downstream of the suction surface of the upstream blades. The flow entering the slot with high stagnation pressure is brought to rest in a stagnation point on the downstream surface of the slot, and the consequent variation in static pressure on the rear surface sets tangential and radial components of velocity which are a large fraction of the freestream velocity. As well as demonstrating the mechanism for the flow behavior, the paper presents results of experiments and calculations to demonstrate the behavior and gives guidance for the design of bleed slots by stressing the fundamental features of the flow.

The Effect on Combustor Diffuser Performance of Structural OGV/Pre-Diffuser Systems

1997 ◽  
Author(s):  
A. G. Barker ◽  
J. F. Carrotte ◽  
C. W. Frodsham
Keyword(s):  
Static Pressure ◽  
Pressure Field ◽  
Guide Vane ◽  
Stagnation Pressure ◽  
Flame Tube ◽  
Flow Swirl ◽  
Pressure Distributions ◽  
Upstream Pressure ◽  
Inlet Conditions ◽  
The Impact

An experimental investigation has been carried out to assess the aerodynamic effects of locating radial struts within the pre-diffuser of a modern combustor dump diffuser system. Engine representative inlet conditions were generated by a single stage rotor, with the diffuser system incorporating various compressor outlet guide vane (OGV)/pre-diffuser assemblies and an annular flame tube with representative porosity. Stagnation and static pressure measurements were obtained at numerous locations and included assessment of the upstream pressure field, associated with the struts, which impacts on the rotor and OGV aerodynamics. Measurements were also obtained within the feed annuli, surrounding the flame tube, with attempts also being made to assess the stagnation pressure distributions presented to a simulated flame tube burner. Initial tests were performed with an OGV row attached to a conventional 1.45 area ratio pre-diffuser, this providing the datum to which all other systems were assessed. These included systems with thin or thick struts with the strut blockage, at pre-diffuser exit, being 5% and 11% of the gas passage area respectively. For the geometries tested it was shown that the method of adjusting each pre-diffuser passage area, to account for the strut blockage, was successful in providing similar levels of reduced kinetic energy at pre-diffuser exit. Despite this, however, the presence of strut wakes and their effect on the dump cavity flow produced increases in stagnation pressure loss. These loss variations were evaluated for both the feed annuli and burner flows, with the magnitudes depending on whether the struts were aligned or midway between burners. Also assessed was the impact of the increased circumferential flow non-uniformity that was observed for the flow within the inner feed annulus. A beneficial effect produced by the struts was the significant reductions in flow swirl, within the diffuser system, relative to the datum. This improved axial alignment of the flow, provided a more uniform pressure distribution to the burners and a more stable feed to the various flame tube features.

Flow physics of highly loaded tandem compressor cascade with non-axisymmetric endwall profiling

2020 ◽  
pp. 095765092098310
Author(s):  
Zhiyuan Cao ◽  
Wei Guo ◽  
Cheng Song ◽  
Bo Liu
Keyword(s):  
Static Pressure ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Blade Loading ◽  
Tandem Configuration ◽  
Blade Passage ◽  
Corner Separation ◽  
Axial Location ◽  
Highly Loaded

Tandem configuration is an effective methodology to reduce flow separation on compressor blade suction surface and to improve blade loading. However, in modern highly loaded cases, corner separation remains as its single blade counterpart. In this study, non-axisymmetric endwall profiling (NAEP) was utilized in a highly loaded tandem cascade (diffusion factor D = 0.69), aiming at reducing its severe corner separation and revealing the unique flow mechanism while NAEP is utilized in tandem cascade. NAEP was designed in both forward (F) blade and rare (R) blade separately, and was investigated numerically in tandem environment. Results show that, NAEP in F blade passage can effectively eliminate the corner separation and reduce loss generation, whereas NAEP in R blade passage has no positive effect on corner separation and even promotes loss production. The optimal NAEP approximately removes the corner separation completely, with loss coefficient reducing by as much as 37.8%. The optimal NAEP for the tandem cascade features optimal axial location at the origin of corner separation. There is an optimal NAEP height (0.02 of blade height), under which NAEP can achieve pretty good control effect while the peak of NAEP varies in a large axial location range. In the tandem configuration, it is found that NAEP transfers blade loading from R blade to F blade; the static pressure increases significantly for the entire cascade, but the static pressure distribution of F blade does not exhibit as the design intent of NAEP. In addition, it is interesting to find that the flow turning near endwall reduces after endwall profiling, which is unique in tandem cascade and is contrast to the view on conventional configuration. On the contrary, NAEP in R blade has no influence on the corner separation of the tandem cascade; due to the decrement of cross-passage pressure gradient for R blade, the flow overturning near endwall reduces.

scholarly journals OGV Tailoring to Alleviate Pylon-OGV-Fan Interaction

1995 ◽  
Author(s):  
G. N. Shrinivas ◽  
M. B. Giles
Keyword(s):  
Static Pressure ◽  
Pressure Field ◽  
Interaction Mechanism ◽  
Pressure Variation ◽  
Linear Perturbation ◽  
Cfd Analysis ◽  
Blade Profile ◽  
Turbine Engine ◽  
Blade Passage ◽  
Actuator Disc

This paper studies the application of sensitivity analysis to the redesign of outlet guide vanes (OGV’s) in a commercial gas turbine engine. The redesign is necessitated by the interaction of the pylon induced static pressure field with the OGV’s and the fan, leading to reduced OGV efficiency and shortened fan life. The concept of cyclically varying camber is used to redesign the OGV row to achieve suppression of the downstream disturbance in the domain upstream of the OGV row. The harmonic nature of the disturbance and the tailoring permits the analysis for the redesign to be performed on only one blade passage. Sensitivity of the pressure field upstream of the OGV’s to changes in blade camber is computed, and used to modify the blade profile. The sensitivity is obtained from a linear perturbation CFD analysis; nonlinear CFD analysis and actuator disc theory (ADisc) provide validation at each step. The modifications reduce the pylon induced pressure variation at the fan by more than 70%. The presence of an interaction mechanism from the pylon to the OGV’s is investigated.

Control of Three-Dimensional Separations in Axial Compressors by Tailored Boundary Layer Suction

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Semiu A. Gbadebo ◽  
Nicholas A. Cumpsty ◽  
Tom P. Hynes
Keyword(s):  
Boundary Layer ◽  
Static Pressure ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Surface Flow ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Passage ◽  
Boundary Layer Suction ◽  
End Wall

One of the important ways of improving turbomachinery compressor performance is to control three-dimensional (3D) separations, which form over the suction surface and end wall corner of the blade passage. Based on the insights gained into the formation of these separations, this paper illustrates how an appropriately applied boundary layer suction of up to 0.7% of inlet mass flow can control and eliminate typical compressor stator hub corner 3D separation over a range of operating incidence. The paper describes, using computational fluid dynamics, the application of suction on the blade suction surface and end wall boundary layers and exemplifies the influence of end wall dividing streamline in initiating 3D separation in the blade passage. The removal of the separated region from the blade suction surface is confirmed by an experimental investigation in a compressor cascade involving surface flow visualization, surface static pressure, and exit loss measurements. The ensuing passage flow field is characterized by increased blade loading (static pressure difference between pressure and suction surface), enhanced average static pressure rise, significant loss removal, and a uniform exit flow. This result also enables the contribution of the 3D separation to the overall loss and passage blockage to be assessed.

Extracting Static Pressure From Velocimetry in Vortical Flows

2015 ◽  
Author(s):  
Jackson Merkl ◽  
Nandeesh Hiremath ◽  
Vrishank Raghav ◽  
Narayanan Komerath
Keyword(s):  
Velocity Field ◽  
Incompressible Flow ◽  
Static Pressure ◽  
Pressure Field ◽  
Reverse Flow ◽  
Stagnation Pressure ◽  
Sharp Edge ◽  
Navier Stokes ◽  
Bottom Surface ◽  
Component Velocity

The problem of extracting static pressure fields on and away from flow boundaries in complex flows, is considered. Given the correct velocity field in steady incompressible flow, an assumption of constant or known stagnation pressure allows finding the static pressure. This gives an upper bound on static pressure, and is in fact close to the real answer. The technique developed here is to start with the measured, ensemble-averaged 3-component velocity field in a periodic flow. The static pressure field computed from this velocity field in incompressible flow can be used along with the velocity field as the starting guess of a solution in a Navier-Stokes solver. The method is applied to the bottom surface near the sharp edge of a rotating rotor blade in the reverse flow domain encountered at high advance ratio in a wind tunnel. The drop in stagnation pressure along given streamlines even through the sharp-edge vortex, is shown to be very small, so that the effect on the static pressure estimate is minor. The pressure field successfully explains some features that could not otherwise be explained.

Development of a Lifetime Pressure Sensitive Paint Procedure for High-Pressure Vane Testing

2021 ◽  
Author(s):  
Papa Aye N. Aye-Addo ◽  
Guillermo Paniagua ◽  
David G. Cuadrado ◽  
Lakshya Bhatnagar ◽  
Antonio Castillo Sauca ◽  
...  
Keyword(s):  
High Pressure ◽  
Test Section ◽  
Static Pressure ◽  
Pressure Field ◽  
Optical Measurements ◽  
Wall Region ◽  
Pressure Amplitude ◽  
Pressure Sensitive Paint ◽  
Suction Surface ◽  
Pressure Sensitive

Abstract Optical measurements based on fast response Pressure Sensitive Paint (PSP) provide enhanced spatial resolution of the pressure field. This paper presents laser lifetime PSP at 20 kHz, with precise calibrations, and results from a demonstration in an annular vane cascade. The laser lifetime PSP methodology is first evaluated in a linear wind tunnel with a converging-diverging nozzle followed by a wavy surface. This test section is fully optically accessible with maximum modularity. A data reduction procedure is proposed for the PSP calibration, and optimal pixel binning is selected to reduce the uncertainty. In the annular test section, laser lifetime PSP was used to measure the time-averaged static pressure field on a section of the suction surface of a high-pressure turbine vane. Tests were performed at engine representative conditions in the Purdue Big Rig for Annular Stationary Turbine Analysis module at the Purdue Experimental Turbine Aerothermal Lab. The 2-D pressure results showed a gradual increase of pressure in the spanwise and flow directions, corroborated with local static pressure taps and computational results. The variation in PSP thickness was measured as a contribution to the uncertainty. The discrete Fourier transform of the unsteady pressure signal showed increased frequency content in wind-on conditions compared to wind-off conditions at the mid-span and 30% span. Compared to the mid-span region, the hub end wall region had an increase in frequencies and pressure amplitude. This result was anticipated given the expected presence of secondary flow structures in the near hub region.

Effects of Area Ratio and Mean Rise Angle on the Aerodynamics of Interturbine Ducts

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Yanfeng Zhang ◽  
Shuzhen Hu ◽  
Ali Mahallati ◽  
Xue-Feng Zhang ◽  
Edward Vlasic
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Static Pressure ◽  
Computational Study ◽  
Pressure Rise ◽  
Adverse Pressure Gradient ◽  
Boundary Layer Separation ◽  
Wake Flow ◽  
Height Ratio ◽  
Inlet Swirl

This work, a continuation of a series of investigations on the aerodynamics of aggressive interturbine ducts (ITD), is aimed at providing detailed understanding of the flow physics and loss mechanisms in four different ITD geometries. A systematic experimental and computational study was carried out by varying duct outlet-to-inlet area ratios (ARs) and mean rise angles while keeping the duct length-to-inlet height ratio, Reynolds number, and inlet swirl constant in all four geometries. The flow structures within the ITDs were found to be dominated by the boundary layer separation and counter-rotating vortices in both the casing and hub regions. The duct mean rise angle determined the severity of adverse pressure gradient in the casing's first bend, whereas the duct AR mainly governed the second bend's static pressure rise. The combination of upstream wake flow and the first bend's adverse pressure gradient caused the boundary layer to separate and intensify the strength of counter-rotating vortices. At high mean rise angle, the separation became stronger at the casing's first bend and moved farther upstream. At high ARs, a two-dimensional separation appeared on the casing and resulted in increased loss. Pressure loss penalties increased significantly with increasing duct mean rise angle and AR.

scholarly journals The Effect of Tip Clearance Gap Size and Wall Rotation on the Performance of a High-Speed Annular Compressor Cascade

1998 ◽  
Author(s):  
A. Doukelis ◽  
K. Mathioudakis ◽  
K. Papailiou
Keyword(s):  
High Speed ◽  
Static Pressure ◽  
Tip Clearance ◽  
Performance Characteristics ◽  
Compressor Cascade ◽  
Tip Clearance Flow ◽  
Pressure Distributions ◽  
Clearance Flow ◽  
Overall Performance ◽  
Probe Measurements

The performance of a high speed annular compressor cascade for different clearance gap sizes, with stationary or rotating hub wall is investigated. Five hole probe measurements, conducted at the inlet and outlet of the cascade, are used to derive blade performance characteristics, in the form of loss and turning distributions. Characteristics are presented in the form of circumferentially mass averaged profiles, while distributions on the exit plane provide information useful to interpret the performance of the blading. Static pressure distributions on the surface of the blades as well as inside the tip clearance gap have also been measured. A set of four clearance gap sizes, in addition to zero clearance data for the stationary wall, gives the possibility to observe the dependence of performance characteristics on clearance size, and establish the influence of rotating the hub. Overall performance is related to features of the tip clearance flow. Increasing the clearance size is found to increase losses in the clearance region, while it affects the flow in the entire passage. Wall rotation is found to improve the performance of the cascade.

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