Three-Dimensional Flow in a Low-Pressure Turbine Cascade at Its Design Condition

1987 ◽  
Vol 109 (2) ◽  
pp. 177-185 ◽  
Author(s):  
H. P. Hodson ◽  
R. G. Dominy
Keyword(s):  
High Speed ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Low Pressure ◽  
Surface Flow ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Three Dimensional Flow ◽  
Low Pressure Turbine ◽  
Dimensional Flow

This paper describes an experimental study of the three-dimensional flow within a high-speed linear cascade of low-pressure turbine blades. Data were obtained using pneumatic probes and a surface flow visualization technique. It is found that in general, the flow may be described using concepts derived from previous studies of high-pressure turbines. In detail, however, there are differences. These include the existence of a significant trailing shed vortex and the interaction of the endwall fluid with the suction surface flow. At an aspect ratio of 1.8, the primary and secondary losses are of equal magnitude.

Analytical Theory of Three Dimensional Flow in Centrifugal Compressors

1981 ◽  
Vol 23 (4) ◽  
pp. 179-191 ◽  
Author(s):  
C. Bosman
Keyword(s):  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Surface Flow ◽  
Centrifugal Compressors ◽  
Three Dimensional Flow ◽  
Stream Tube ◽  
Stream Surface ◽  
Dimensional Flow ◽  
Passage Vortex ◽  
Turbomachine Blade

Inviscid, compressible flow along a rotating elemental stream-tube is taken as a model for flow through a turbomachine blade passage. For this model an analytic expression for the relative secondary vorticity of the flow is derived which permits the mean stream-surface twist about the tube axis to be evaluated. This twist implies a migration of the fluid particles from one tube corner to the contiguous tube corner, a flow feature suppressed by all existing stream-sheet flow calculations in turbomachine blade rows. The analysis is applied to a centrifugal compressor configuration where the effects on the secondary flow of hub/shroud geometry, blade shape, compressibility, and meridional diffusion are investigated. The stream-surface twist, not being primarily dependent upon the elemental nature of the stream-tube is taken as a measure of stream-surface twist and consequent surface flow migration in finite blade passages. The levels of twist obtained from the analysis are similar to those obtained in three dimensional flow calculations using primitive variables as illustrated by Bosman (1) (2)‡ and show that existing streamsheet and streamsheet stacking methods, all of which suppress the relative passage vortex are an inadequate model of the flow in centrifugal compressors. The analysis clearly shows that contrary to common assumption, centrifugal compressor impellers are capable of generating a passage vortex in the same direction as that of blade rotation.

The Effects of Inlet Boundary Layer Condition and Periodically Incoming Wakes on Secondary Flow in a Low Pressure Turbine Cascade

2020 ◽  
Author(s):  
Tobias Schubert ◽  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
High Speed ◽  
Low Pressure ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Low Pressure Turbine ◽  
Speed Flow ◽  
Unsteady Inflow

Abstract A particular turbine cascade design is presented with the goal of providing a basis for high quality investigations of endwall flow at high-speed flow conditions and unsteady inflow. The key feature of the design is an integrated two-part flat plate serving as a cascade endwall at part-span, which enables a variation of the inlet endwall boundary layer conditions. The new design is applied to the T106A low pressure turbine cascade for endwall flow investigations in the High-Speed Cascade Wind Tunnel of the Institute of Jet Propulsion at the Bundeswehr University Munich. Measurements are conducted at realistic flow conditions (M2th = 0.59, Re2th = 2·105) in three cases of different endwall boundary layer conditions with and without periodically incoming wakes. The endwall boundary layer is characterized by 1D-CTA measurements upstream of the blade passage. Secondary flow is evaluated by Five-hole-probe measurements in the turbine exit flow. A strong similarity is found between the time-averaged effects of unsteady inflow conditions and the effects of changing inlet endwall boundary layer conditions regarding the attenuation of secondary flow. Furthermore, the experimental investigations show, that all design goals for the improved T106A cascade are met.

Effects of Reynolds Number and Freestream Turbulence on Turbine Tip Clearance Flow

2005 ◽  
Vol 128 (1) ◽  
pp. 166-177 ◽  
Author(s):  
Takayuki Matsunuma
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Freestream Turbulence ◽  
Tip Leakage Flow ◽  
Three Dimensional Flow ◽  
Dimensional Flow

Tip clearance losses represent a major efficiency penalty of turbine blades. This paper describes the effect of tip clearance on the aerodynamic characteristics of an unshrouded axial-flow turbine cascade under very low Reynolds number conditions. The Reynolds number based on the true chord length and exit velocity of the turbine cascade was varied from 4.4×104 to 26.6×104 by changing the velocity of fluid flow. The freestream turbulence intensity was varied between 0.5% and 4.1% by modifying turbulence generation sheet settings. Three-dimensional flow fields at the exit of the turbine cascade were measured both with and without tip clearance using a five-hole pressure probe. Tip leakage flow generated a large high total pressure loss region. Variations in the Reynolds number and freestream turbulence intensity changed the distributions of three-dimensional flow, but had no effect on the mass-averaged tip clearance loss of the turbine cascade.

A Comparison of Turbulence Levels From Particle Image Velocimetry and Constant Temperature Anemometry Downstream of a Low-Pressure Turbine Cascade at High-Speed Flow Conditions

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Particle Image Velocimetry ◽  
Constant Temperature ◽  
High Speed ◽  
Particle Image ◽  
Low Pressure ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Turbine Cascade ◽  
Low Pressure Turbine ◽  
Image Velocimetry

Abstract The development and verification of new turbulence models for Reynolds-averaged Navier–Stokes (RANS) equation-based numerical methods require reliable experimental data with a deep understanding of the underlying turbulence mechanisms. High accurate turbulence measurements are normally limited to simplified test cases under optimal experimental conditions. This work presents comprehensive three-dimensional data of turbulent flow quantities, comparing advanced constant temperature anemometry (CTA) and stereoscopic particle image velocimetry (PIV) methods under realistic test conditions. The experiments are conducted downstream of a linear, low-pressure turbine cascade at engine relevant high-speed operating conditions. The special combination of high subsonic Mach and low Reynolds number results in a low density test environment, challenging for all applied measurement techniques. Detailed discussions about influences affecting the measured result for each specific measuring technique are given. The presented time mean fields as well as total turbulence data demonstrate with an average deviation of ΔTu<0.4% and ΔC/Cref<0.9% an extraordinary good agreement between the results from the triple sensor hot-wire probe and the 2D3C-PIV setup. Most differences between PIV and CTA can be explained by the finite probe size and individual geometry.

The Off-Design Performance of a Low-Pressure Turbine Cascade

1987 ◽  
Vol 109 (2) ◽  
pp. 201-209 ◽  
Author(s):  
H. P. Hodson ◽  
R. G. Dominy
Keyword(s):  
Reynolds Numbers ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Surface Flow ◽  
Operating Conditions ◽  
Turbine Cascade ◽  
Linear Cascade ◽  
Design Performance ◽  
Low Pressure Turbine ◽  
Wide Range

The ability of a given blade profile to operate over a wide range of conditions is often of the utmost importance. This paper reports the off-design performance of a low-pressure turbine rotor root section in a linear cascade. Data were obtained using pneumatic probes and surface flow visualization. The effects of incidence (+9, 0, −20 deg), Reynolds (1.5, 2.9, 6.0 × 105), pitch-chord ratio (0.46, 0.56, 0.69), and inlet boundary layer thickness (0.011, 0.022 δ*/C) are discussed. Particular attention is paid to the three dimensionality of the flow field. Significant differences in the detail of the flow occur over the range of operating conditions investigated. It is found that the production of new secondary loss is greatest at lower Reynolds numbers, positive incidence, and the higher pitch-chord ratios.

Effects of Reynolds Number and Free-Stream Turbulence on Turbine Tip Clearance Flow

2005 ◽  
Author(s):  
Takayuki Matsunuma
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Three Dimensional Flow ◽  
Free Stream Turbulence ◽  
Dimensional Flow

Tip clearance losses represent a major efficiency penalty of turbine blades. This paper describes the effect of tip clearance on the aerodynamic characteristics of an unshrouded axial-flow turbine cascade under very low Reynolds number conditions. The Reynolds number based on the true chord length and exit velocity of the turbine cascade was varied from 4.4 × 104 to 26.6 × 104 by changing the velocity of fluid flow. The free-stream turbulence intensity was varied between 0.5% and 4.1% by modifying turbulence generation sheet settings. Three-dimensional flow fields at the exit of the turbine cascade were measured both with and without tip clearance using a five-hole pressure probe. Tip leakage flow generated a large high total pressure loss region. Variations in the Reynolds number and free-stream turbulence intensity changed the distributions of three-dimensional flow, but had no effect on the mass-averaged tip clearance loss of the turbine cascade.

Experimental Study on the Three-Dimensional Flow Within a Compressor Cascade With Tip Clearance: Part I—Velocity and Pressure Fields

1993 ◽  
Vol 115 (3) ◽  
pp. 435-443 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Surface Flow ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Compressor Cascade ◽  
Three Dimensional Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Dimensional Flow

Experimental results from a study of the three-dimensional flow in a linear compressor cascade with stationary endwall at design conditions are presented for tip clearance levels of 1.0, 2.0, and 3.3 percent of chord, compared with the no-clearance case. In addition to five-hole probe measurements, extensive surface flow visualizations are conducted. It is observed that for the smaller clearance cases a weak horseshoe vortex forms in the front of the blade leading edge. At all the tip gap cases, a multiple tip vortex structure with three discrete vortices around the midchord is found. The tip leakage vortex core is well defined after the midchord but does not cover a significant area in traverse planes. The presence of the tip leakage vortex results in the passage vortex moving close to the endwall and the suction side.

The Aerodynamic Mixing Effect of Discrete Cooling Jets With Mainstream Flow on a Highly Loaded Turbine Blade

1996 ◽  
Vol 118 (3) ◽  
pp. 468-478 ◽  
Author(s):  
G. Wilfert ◽  
L. Fottner
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Suction Side ◽  
Horseshoe Vortex ◽  
Surface Flow ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Mixing Processes

For the application of film cooling to turbine blades, experimental investigations were performed on the mixing processes in the near-hole region with a row of holes on the suction suction side of a turbine cascade. Data were obtained using pneumatic probes, pressure tappings, and a three-dimensional subminiature hot-wire probe, as well as surface flow visualization techniques. It was found that at low blowing rates, a cooling jet behaves very much like a normal obstacle and the mixing mainly takes place in the boundary layer. With increasing blowing rates, the jet penetrates deeper into the mainstream. The variation of the turbulence level at the inlet of the turbine cascade and the Reynolds number showed a strong influence on the mixing behavior. The kidney-shaped vortex and as an important achievement the individual horseshoe vortex of each single jet were detected and their exact positions were obtained. This way it was found that the position of the horseshoe vortex is strongly dependent on the blowing rate and this influences the aerodynamic mixing mechanisms. A two-dimensional code for the calculation of boundary layer flows called GRAFTUS was used; however, the comparison with the measurements showed only limited agreement for cascade flow with blowing due to the strong three-dimensional flow pattern.

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