Off-Design Performance of a Linear Cascade of Turbine Blades

1990 ◽  
Author(s):  
B. Tremblay ◽  
S. A. Sjolander ◽  
S. H. Moustapha
Keyword(s):  
Reynolds Number ◽  
Total Pressure ◽  
Critical Reynolds Number ◽  
Turbine Blades ◽  
Surface Flow ◽  
Turning Angle ◽  
Linear Cascade ◽  
Pressure Losses ◽  
Design Performance ◽  
Loss Coefficients

A recent survey of the literature showed a clear need for additional experimental results on the off-design performance of turbines, particularly for airfoils of recent design. This study presents measurements of the low-speed two-dimensional performance of a linear cascade of turbine blades with a turning angle of 87 degrees. The incidence was varied between −25 and +25 degrees in 5 degree steps. The blade surface pressures, total pressure loss coefficients and trailing-edge deviations are presented for all values of incidence. The influence of incidence on the critical Reynolds number is also examined. Surface flow visualization is presented for different values of Reynolds number and incidence to aid in the physical interpretation of the measurements. The measured total pressure losses agree very well with the new off-design correlation introduced by Moustapha et al. (1989).

Effects of Periodic Unsteadiness on Secondary Flows in High Pressure Turbine Passages

2013 ◽  
Author(s):  
Ralph J. Volino ◽  
Christopher D. Galvin ◽  
Mounir B. Ibrahim
Keyword(s):  
Reynolds Number ◽  
High Pressure ◽  
Total Pressure ◽  
Turbine Blades ◽  
Secondary Flows ◽  
High Pressure Turbine ◽  
Pressure Losses ◽  
Flow Losses ◽  
Pressure Distributions ◽  
Lower Reynolds Number

Secondary flow losses were investigated experimentally in a linear cascade of high pressure turbine blades in a low speed wind tunnel. Periodic wakes were generated with moving rods upstream of the cascade to simulate the effect of wakes from upstream vanes in an engine. Velocities, turbulence levels and turbulence spectra were documented downstream of the wakes generated by the upstream rods and downstream of the cascade airfoils. Pressure distributions were documented on the airfoils at the midspan and near the tip. Total pressure loss through the passage was measured at the midspan and in the endwall boundary layer. Cases were documented with and without upstream wakes at a Reynolds number of 30,000 based on inlet velocity and axial chord. An additional case was acquired at Re = 60,000 without wakes. The effects of wakes and Reynolds number on the pressure distribution on the airfoils were small. In the cases without wakes, total pressure losses were 27% higher at the lower Reynolds number due to thicker boundary layers. Upstream wakes cause an increase of about 80% in total pressure losses at the midspan and a 36% increase near the endwall. Much of this is due to the loss associated with the upstream wakes themselves, but with this direct effect subtracted the losses are still 20% higher in the case with wakes at the midspan with local increases comparable near the endwall.

scholarly journals Turbulence model performance for ventilation components pressure losses

2021 ◽  
Author(s):  
Karsten Tawackolian ◽  
Martin Kriegel
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Pressure Loss ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Test Case ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Near Wall

AbstractThis study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×104 and 6×105, depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×105. An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ε turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

scholarly journals Aerodynamic Losses in Turbines with and without Film Cooling, as Influenced by Mainstream Turbulence, Surface Roughness, Airfoil Shape, and Mach Number

2012 ◽  
Vol 2012 ◽  
pp. 1-28 ◽  
Author(s):  
Phil Ligrani
Keyword(s):  
Surface Roughness ◽  
Mach Number ◽  
Film Cooling ◽  
Total Pressure ◽  
High Speed ◽  
Density Ratio ◽  
Aerodynamic Loss ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Exit Mach Number

The influences of a variety of different physical phenomena are described as they affect the aerodynamic performance of turbine airfoils in compressible, high-speed flows with either subsonic or transonic Mach number distributions. The presented experimental and numerically predicted results are from a series of investigations which have taken place over the past 32 years. Considered are (i) symmetric airfoils with no film cooling, (ii) symmetric airfoils with film cooling, (iii) cambered vanes with no film cooling, and (iv) cambered vanes with film cooling. When no film cooling is employed on the symmetric airfoils and cambered vanes, experimentally measured and numerically predicted variations of freestream turbulence intensity, surface roughness, exit Mach number, and airfoil camber are considered as they influence local and integrated total pressure losses, deficits of local kinetic energy, Mach number deficits, area-averaged loss coefficients, mass-averaged total pressure loss coefficients, omega loss coefficients, second law loss parameters, and distributions of integrated aerodynamic loss. Similar quantities are measured, and similar parameters are considered when film-cooling is employed on airfoil suction surfaces, along with film cooling density ratio, blowing ratio, Mach number ratio, hole orientation, hole shape, and number of rows of holes.

scholarly journals Experimental Investigation of Tandem Blade Cascades With Double-Circular ARC Profiles

1985 ◽  
Author(s):  
Wu Guochuan ◽  
Zhuang Biaonan ◽  
Guo Bingheng
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Mach Number ◽  
Total Pressure ◽  
Incidence Angle ◽  
Axial Direction ◽  
Geometrical Parameters ◽  
Optimal Conditions ◽  
Turning Angle ◽  
Circular Arc

24 double circular are tandem blade cascades of three different chord-ratios were investigated under different displacements in peripheral and axial direction. The inlet Mach number was 0.3. The Reynolds number based on blade chord was 2.7×105. The characteristics of the tandem blade cascades, such as the dependence of turning angle and coefficient of total pressure loss on incidence angle were obtained. The ranges of main geometrical parameters under optimal conditions were recommended.

Combustion Turbine Exhaust Duct, Silencer, and Stack Scale Modeling

2021 ◽  
Author(s):  
Robert Craven ◽  
Keith Kirkpatrick ◽  
Stephen Idem
Keyword(s):  
Reynolds Number ◽  
Power Plant ◽  
Pressure Loss ◽  
Total Pressure ◽  
Exhaust System ◽  
Total Pressure Loss ◽  
Scale Model ◽  
Pressure Losses ◽  
Exhaust Duct ◽  
On Line

Abstract After constructing a scale model of planned changes to a power plant exhaust system, tests were performed to measure pressure losses in the transition, silencer, and stack. A dimension of 0.30 m (1.0 ft) for the scale model corresponded to 3.7 m (12.0 ft) at full scale. To the extent possible, the scale model tests exhibited geometric similarity with the actual power plant. Total pressure loss coefficients varied between 2.122, 1.969, and 1.932, for three separate scale model configurations that were considered. A combination of turning vanes and splitter vanes in the five-gore elbow, coupled with the use of turning vanes in the rectangular elbow yielded the lowest total pressure loss. Although Reynolds number similarity between the scale model experiments and the actual power plant was not attained, Reynolds number independence was achieved in the tests. The results from this study was applied to model pressure loss in the actual power plant. The scale model testing revealed that utilization of the exhaust ducting design designated as Case A would yield a sufficiently low pressure loss that it would not degrade the performance of the combustion turbine in the power plant to be repaired. Therefore it was selected for inclusion in the retro-fitting of the power plant to facilitate its being quickly brought back on-line.

The compound bowing design in a highly loaded linear cascade with large turning angle

2020 ◽  
Vol 234 (16) ◽  
pp. 2323-2336
Author(s):  
Xingxu Xue ◽  
Songtao Wang ◽  
Lei Luo ◽  
Xun Zhou
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Side Effect ◽  
Adverse Pressure Gradient ◽  
Suction Surface ◽  
Turning Angle ◽  
Linear Cascade ◽  
Velocity Triangle ◽  
Highly Loaded

Numerical simulation was carried out to study the influences of blade-bowing designs based on a highly loaded cascade with large turning angle, while the compound bowing design showed much lower endwall loss than the conventional design in this study. Generally, it showed that the increased turning angle would strengthen the adverse pressure gradient on the suction surface, so the side effect of negative blade bowing angle would be enhanced because of the reduced flow filed stability near suction–endwall corner. However, the positive corner bowing angle that applied in the compound bowing design would enhance the flow field stability near the suction–endwall corner by adjusting spanwise pressure gradient and velocity triangle, so the side effect of negative blade bowing angle would be suppressed and lead to weaker secondary flow. In detail, the blade bowing angle (as well as the corner bowing angle in the conventional bowed cascades) was varied from −5° to −30° in this study, while the reductions of the loss coefficient in the compound bowed cascades were about 0.662.16 times higher (the absolute differences were about 0.0067 0.0097) than the corresponding conventional bowed cascades. Moreover, the Reynolds number and Mach number at the outlet plane were kept at 2.4 × 105 and 0.6, respectively, during the bowing design to ensure the comparability.

Production and Development of Secondary Flows and Losses in Two Types of Straight Turbine Cascades: Part 1—A Stator Case

1987 ◽  
Vol 109 (2) ◽  
pp. 186-193 ◽  
Author(s):  
A. Yamamoto
Keyword(s):  
Secondary Flow ◽  
Total Pressure ◽  
Experimental Information ◽  
Secondary Flows ◽  
Accumulation Process ◽  
Flow Angle ◽  
Turning Angle ◽  
Pressure Losses ◽  
Flow Vectors ◽  
Turbine Cascades

The present study intends to give some experimental information on secondary flows and on the associated total pressure losses occurring within turbine cascades. Part 1 of the paper describes the mechanism of production and development of the loss caused by secondary flows in a straight stator cascade with a turning angle of about 65 deg. A full representation of superimposed secondary flow vectors and loss contours is given at fourteen serial traverse planes located throughout the cascade. The presentation shows the mechanism clearly. Distributions of static pressures and of the loss on various planes close to blade surfaces and close to an endwall surface are given to show the loss accumulation process over the surfaces of the cascade passage. Variation of mass-averaged flow angle, velocity and loss through the cascade, and evolution of overall loss from upstream to downstream of the cascade are also given. Part 2 of the paper describes the mechanism in a straight rotor cascade with a turning angle of about 102 deg.

Contraction/Expansion Effects in 90° Miter Bends in Rectangular Xurographic Microchannels

2011 ◽  
Author(s):  
Lam Nguyen ◽  
John Elsnab ◽  
Tim Ameel
Keyword(s):  
Reynolds Number ◽  
Critical Reynolds Number ◽  
Area Ratio ◽  
Loss Coefficient ◽  
Sidewall Roughness ◽  
Cross Sectional ◽  
Loss Coefficients ◽  
Minor Losses ◽  
High Reynolds ◽  
Reported Data

Xurography is an inexpensive rapid prototyping technology for the development of microfluidic systems. Imprecision in the xurographic tape cutting process can result in undesired changes in channel dimensions near features that require a change in cutting direction, such as 90° miter bends. An experimental study of water flow in rectangular xurographic microchannels incorporating 90° miter bends with different channel widths in each leg is reported. A set of twelve microchannels, with channel depth approximately 105 micrometers and aspect ratio ranging from 0.071 to 0.435, were fabricated from double-sided adhesive Kapton® polyimide tape and two rectangular glass plates. The channels were reinforced with a mechanical clamping system, enabling high Reynolds number, Re, flows (up to Re = 3200) where Re was based upon hydraulic diameter and average velocity. Reported data include friction factor and critical Reynolds number for straight microchannels and loss coefficients for flow through 90° miter bends that contain either a contraction or expansion with cross-sectional area ratios of 0.5, 0.333 and 0.2. The critical Reynolds number, Recr, ranged from 1750 to 2300 and was found to be dependent on channel defects such as sidewall roughness, adhesive droplets, and corner imperfections. Loss coefficients through 90° miter bends with expansion decrease rapidly for Re < Recr. At the transition, the loss coefficient suddenly drops and approaches an asymptotic value for Re > Recr. For 90° miter bends with contractions, loss coefficients gradually decrease with increasing Re for 150 < Re < 1400. In addition, the loss coefficient decreases with decreasing area ratio through the contraction or expansion. The minor loss coefficient data were found to be dependent on Reynolds numbers and area ratio of contraction/expansion at the bend. The results suggest that the effect of the contraction/expansion was the dominant mechanism for minor losses in the 90° miter bend.

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.

Influence of a Novel Three-Dimensional Leading Edge Geometry on the Aerodynamic Performance of Transonic Cascade Vanes

2012 ◽  
Author(s):  
D. Bouchard ◽  
A. Asghar ◽  
J. Hardes ◽  
R. Edwards ◽  
W. D. E. Allan ◽  
...  
Keyword(s):  
Total Pressure ◽  
Three Dimensional ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Surface Flow ◽  
Pressure Losses ◽  
Low Pressure Turbine ◽  
Edge Geometry ◽  
Turbine Vane ◽  
Transonic Cascade

This paper addresses the issue of aerodynamic performance of a novel 3D leading edge modification to a reference vane. An analysis of tubercles found in nature and some engineering applications was used to synthesize new leading edge geometry. Three variations of the reference low pressure turbine vane were obtained by changing the characteristic parameters of the tubercles. Shock structure, surface flow visualization and total pressure measurements were made through experiments in a cascade rig, as well as through computational fluid dynamics. The tests were carried out at design zero incidence and off-design ±10-deg and ±5-deg incidences. The performance of the new 3D leading edge geometries was compared against the reference vane. Some leading edge tubercle configurations were effective at decreasing total pressure losses at positive inlet incidence angles. Numerical results supplemented experimental results.

Sign in / Sign up

Export Citation Format

Share Document