Boundary Layer and Loss Measurements on the Rotor of an Axial-Flow Turbine

H. P. Hodson

doi:10.1115/1.3239576

Boundary Layer and Loss Measurements on the Rotor of an Axial-Flow Turbine

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3239576 ◽

1984 ◽

Vol 106 (2) ◽

pp. 391-399 ◽

Cited By ~ 30

Author(s):

H. P. Hodson

Keyword(s):

Boundary Layers ◽

Large Scale ◽

Axial Flow ◽

Turbine Rotor ◽

Wind Tunnels ◽

Shear Stresses ◽

Surface Shear ◽

Laminar Boundary Layers ◽

Rotor Stator Interaction ◽

Profile Loss

The aerodynamic efficiency of an axial-flow turbine is significantly less than that predicted by measurements made on equivalent cascades which operate with steady inflow. This difference in efficiencies is strongly dependent upon the rotor-stator axial spacing. An experimental investigation of the rotor-stator interaction has therefore been conducted using a large-scale, low-speed turbine. The blade profile loss and surface shear stresses are presented for the midspan of the rotor and for a rectilinear cascade of identical geometry. Both wind tunnels were operated at a Reynolds number of 3.15 × 105. The turbine rotor midspan profile loss was approximately 50 percent higher than that of the rectilinear cascade. The shear stress measurements indicate that as a stator wake is connected through a rotor passage, the laminar boundary layers undergo transition in the vicinity of the wake. The 50 percent increase in loss is due to the time-dependent transitional nature of the boundary layers.

Download Full-text

Visualisation of Turbulent Wedges Under Favourable Pressure Gradients Using Both Shear-Sensitive and Temperature-Sensitive Liquid Crystals

Volume 2: Symposia and General Papers, Parts A and B ◽

10.1115/fedsm2002-31168 ◽

2002 ◽

Author(s):

S. Zhong ◽

T. P. Chong ◽

H. P. Hodson

Keyword(s):

Liquid Crystals ◽

Pressure Gradient ◽

Boundary Layers ◽

Turbine Blades ◽

Temperature Sensitive ◽

Shear Stresses ◽

Pressure Gradients ◽

Surface Shear ◽

The Difference ◽

Thermal Boundary Layers

Turbulent wedges induced by a 3D surface roughness placed in a laminar boundary layer over a flat plate were visualised for the first time using both shear-sensitive and temperature-sensitive liquid crystals. The experiments were carried out at three different levels of favourable pressure gradients. The purpose of this investigation was to examine the spreading angles of the turbulent wedges indicated by their associated surface shear stresses and heat transfer characteristics and hence obtain further insight about the difference in the behaviour of transitional momentum and thermal boundary layers when a streamwise pressure gradient exists. It was shown that under a zero pressure gradient the spreading angles indicated by the two types of liquid crystals are the same, but the difference increases as the level of favourable pressure gradient increases. The result from the present study could have an important implication to the transition modelling of thermal boundary layers over gas turbine blades.

Download Full-text

Turbine Rotor-Stator Interaction

Journal of Engineering for Power ◽

10.1115/1.3227339 ◽

1982 ◽

Vol 104 (4) ◽

pp. 729-742 ◽

Cited By ~ 163

Author(s):

R. P. Dring ◽

H. D. Joslyn ◽

L. W. Hardin ◽

J. H. Wagner

Keyword(s):

Thin Film ◽

Heat Transfer ◽

Potential Flow ◽

Large Scale ◽

Turbine Rotor ◽

Turbine Stage ◽

Pressure Surface ◽

Surface Time ◽

Aerodynamic Interaction ◽

Rotor Stator Interaction

The aerodynamic interaction between the rotor and stator airfoils of a large scale axial turbine stage have been studied experimentally. The data included measurements of the time averaged and instantaneous surface pressures and surface thin film gage output on both the rotor and stator at midspan. The data also included measurement of the stator suction and pressure surface time averaged heat transfer at midspan. The data was acquired with rotor-stator axial gaps of 15 and 65 percent of axial chord. The upstream potential flow influence of the rotor on the stator was seen as well as the downstream potential flow and wake influences of the stator on the rotor. It was also seen that at the 15 percent axial gap, the stator heat-transfer coefficient was typically 25 percent higher than that at the 65 percent gap.

Download Full-text

Negative Incidence Flow Over a Turbine Rotor Blade

Volume 1: Turbomachinery ◽

10.1115/83-gt-23 ◽

1983 ◽

Cited By ~ 2

Author(s):

H. David Joslyn ◽

Robert P. Dring

Keyword(s):

Gas Turbines ◽

Large Scale ◽

Three Dimensional ◽

Axial Flow ◽

Turbine Rotor ◽

Surface Flow ◽

Separated Flows ◽

Turbine Rotor Blade ◽

Pressure Surface ◽

Pressure Distributions

The operation of variable cycle gas turbines at negative incidence can result in highly three dimensional separated flows on the turbine rotor pressure surface. These flows can impact both performance and durability. The present program was conducted to experimentally study the behavior of surface flow on a large scale axial flow turbine rotor with incidence varying up to and including negative incidence separation. Fullspan pressure distributions and surface flow visualization were acquired over a range of incidence. The data indicate that at large negative incidence, pressure surface separation occurred and extended to 60 percent chord at midspan. These separated flows were simulated at midspan by applying potential flow theory to match the measured pressure distributions.

Download Full-text

The spanwise perturbation of two-dimensional boundary layers

Journal of Fluid Mechanics ◽

10.1017/s0022112066000557 ◽

1966 ◽

Vol 24 (1) ◽

pp. 153-164 ◽

Cited By ~ 35

Author(s):

S. C. Crow

Keyword(s):

Boundary Layer ◽

Boundary Layers ◽

Plate Boundary ◽

Wind Tunnels ◽

Two Dimensional ◽

Surface Shear ◽

Flow Reynolds Number ◽

Two Dimensional Flow ◽

Dimensional Boundary ◽

Small Periodic

Large spanwise variations of boundary-layer thickness and surface shear have been found recently in wind tunnels designed to maintain two-dimensional flow. Bradshaw (1965) argues that these variations are caused by minute deflexions in the free-stream flow rather than by any intrinsic instability of the boundary layers. This paper is a study of the effect of a small, periodic transverse flow on a flat-plate boundary layer. The perturbation flow Reynolds number is assumed to be O(1) as it is in the experiments.

Download Full-text

Endwall Boundary Layer Flows and Losses in an Axial Turbine Stage

Journal of Engineering for Power ◽

10.1115/1.3227248 ◽

1982 ◽

Vol 104 (1) ◽

pp. 184-193 ◽

Cited By ~ 8

Author(s):

I. H. Hunter

Keyword(s):

Boundary Layer ◽

Large Scale ◽

Experimental Studies ◽

Axial Flow ◽

Turbine Rotor ◽

Secondary Flows ◽

Boundary Layer Flows ◽

Wall Boundary Layer ◽

Instantaneous Position ◽

Insight Into

In order to gain an insight into boundary layer phenomena in axial flow turbines, experimental studies were carried out on a large-scale, low speed, single stage machine. Low and high frequency instrumentation supplemented by flow visualizations were used to determine the details of the flows and losses in the stator and rotor blade rows. Measurements of the turbine stator flows, which were obtained at two different inlet wall boundary layer thicknesses, were generally consistent with typical linear cascade observations. A major difference concerned the presence of appreciable radially directed flow. Hot-wire anemometry measurements at the turbine rotor exit, revealed strong secondary flows at the high turning hub section. The flow pattern was seen to be influenced by the spacing between the two rows of blades and by the rotor’s instantaneous position with respect to the periodic flow field arising from the upstream stator row.

Download Full-text

An Experimental Study of Passage-to-Passage Flow Interactions in a Single Stage Axial Flow Research Turbine Rotor

Volume 2B: Turbomachinery ◽

10.1115/gt2019-91629 ◽

2019 ◽

Cited By ~ 1

Author(s):

Veerandra C. Andichamy ◽

Cengiz Camci ◽

Yong W. Kim

Keyword(s):

Large Scale ◽

Dynamic Pressure ◽

Turbine Blades ◽

Axial Flow ◽

Turbine Rotor ◽

Single Stage ◽

Tip Clearance ◽

Turbine Stage ◽

Blade Passage ◽

Flow Interactions

Abstract During the lifetime of a turbine stage, some of the blade tips may undergo changes due to mechanical rubbing with casing surface and also due to thermal oxidation. Understanding the effect these damaged blades have over the undamaged blades is essential to estimate the performance of the turbine stage in the operable tip clearance range. In this paper, the passage to passage aerodynamic interaction in a turbine stage is studied by modifying the tip gap of selected turbine blades and analyzing their effect on the neighboring blade passage flows. The experiments in this study are carried out in a single-stage low-speed axial turbine facility. All measurements are taken in the stationary frame of reference using a time-accurate differential dynamic pressure transducer mounted in a Kiel probe head. The experimental results from this study show that even with a significant increase on a selected blade’s tip clearance, its effect on the AFTRF turbine flow is only confined to its neighboring blade passage. The disturbances due to the altered tip clearance of one passage are not measurably propagated to its neighboring turbine passages. The changes made in one of the blades in a turbine stage do not significantly alter the aerodynamic performance of other blades. This result is particularly important for large-scale turbine research rigs such as AFTRF where the unsteady total pressure field is mapped in a time-efficient and phase-locked manner.

Download Full-text

Unsteady Endwall/Tip-Clearance Flows and Losses due to Turbine Rotor-Stator Interaction

Volume 1: Turbomachinery ◽

10.1115/94-gt-461 ◽

1994 ◽

Cited By ~ 6

Author(s):

Atsumasa Yamamoto ◽

Takayuki Matsunuma ◽

Kenichiro Ikeuchi ◽

Eisuke Outa

Keyword(s):

Static Pressure ◽

Axial Flow ◽

Leading Edge ◽

Turbine Rotor ◽

Tip Clearance ◽

Time Dependent ◽

Random Fluctuation ◽

Generation Process ◽

Rotor Stator Interaction ◽

Random Fluctuations

Unsteady static pressure on the tip endwall of a 1.5-stage low-speed axial-flow turbine was measured in detail using a micro high-response pressure transducer to investigate effects of rotor-stator interaction on the endwall and tip-clearance flows which play important roles in turbine loss generation process. In the present paper, distributions of the time-averaged and the time-dependent pressures over the rust-stage rotor and the second-stage stator are presented. Also time-averaged and time-dependent random fluctuations of the pressure were analyzed to understand unsteady behaviors of the flows and the associated losses over the endwall as well as inside the blade tip clearance. These unsteady characteristics were described for three rotor speeds with different incidences or loadings. Significantly large random fluctuations occur around the blade surfaces, particularly at the inlet and the outlet of the tip gap of the leakage flows, and in a flow separated region from the blade leading edge in a large negative incidence case A strong relation was found between the random fluctuation of the endwall static pressure and the total pressure loss inside the rotor, where large random fluctuation is attributed to high loss and vice versa. It can be seen clearly that the loss generation process is fairly unsteady due to the rotor-stator interaction.

Download Full-text