The Base Pressure and Loss of a Family of Four Turbine Blades

1988 ◽  
Vol 110 (1) ◽  
pp. 9-17 ◽  
Author(s):  
L. Xu ◽  
J. D. Denton
Keyword(s):  
Dominant Role ◽  
Turbine Blades ◽  
Base Pressure ◽  
Trailing Edge ◽  
Edge Geometry ◽  
Trailing Edges ◽  
Loss Prediction ◽  
Turbine Cascades ◽  
Profile Loss ◽  
Made In

Measurements of the effect of trailing edge geometry on the base pressure and loss of a family of four turbine cascades are presented. The measurements were made in the transonic range of Mach number from 0.8 to 1.2. It is found that, for blades with typical trailing edge thickness, the trailing edge loss is the major source of profile loss at these speeds and that the base pressure plays a dominant role in determining the loss. For blades with thick trailing edges an accurate prediction of base pressure is crucial to loss prediction. However, it is found that current methods of base pressure prediction are unable to give reliable predictions.

scholarly journals The Influence of Trailing Edge Ejection on the Base Pressure in Transonic Turbine Cascades

1982 ◽  
Author(s):  
C. H. Sieverding
Keyword(s):  
Turbine Blades ◽  
Density Ratio ◽  
Main Flow ◽  
Coolant Flow ◽  
Base Pressure ◽  
Trailing Edge ◽  
Number Range ◽  
Transonic Turbine ◽  
Turbine Cascades ◽  
Transonic Cascade

This paper summarizes the results of base pressure studies on transonic turbine blades in presence of an ejection of coolant flow from a slot in the trailing edge. The first part of the paper reports on tests carried out on a enlarged model of the overhang section of a typical transonic cascade. This model provides valuable information about the detailed trailing edge pressure distribution and points to an asymmetric evolution of the base pressure on both sides of the slot in presence of a bleed. The second part of the paper presents experimental results from cascade tests covering an outlet Mach number range from M2, is = 0.5 to 1.35. These experiments underline the importance of the coolant flow impact on the base pressure and confirm the asymmetry of the base pressure with respect to the cooling slot. Tests with different coolant flow gases point to the significance of a proper simulation of the density ratio between coolant flow and main flow.

The Influence of Trailing Edge Ejection on the Base Pressure in Transonic Turbine Cascades

1983 ◽  
Vol 105 (2) ◽  
pp. 215-222 ◽  
Author(s):  
C. H. Sieverding
Keyword(s):  
Turbine Blades ◽  
Density Ratio ◽  
Main Flow ◽  
Coolant Flow ◽  
Base Pressure ◽  
Trailing Edge ◽  
Number Range ◽  
Transonic Turbine ◽  
Turbine Cascades ◽  
Transonic Cascade

This paper summarizes the results of base pressure studies on transonic turbine blades in the presence of an ejection of coolant flow from a slot in the trailing edge. The first part of the paper reports on tests carried out on a enlarged model of the overhang section of a typical transonic cascade. This model provides valuable information about the detailed trailing edge pressure distribution and points to an asymmetric evolution of the base pressure on both sides of the slot in the presence of a bleed. The second part of the paper presents experimental results from cascade tests covering an outlet Mach number range M2, is = 0.5 to 1.35. These experiments underline the importance of the coolant flow impact on the base pressure and confirm the asymmetry of the base pressure with respect to the cooling slot. Tests with different coolant flow gases point to the significance of a proper simulation of the density ratio between coolant flow and main flow.

The Effects of Trailing Edge Thickness on the Losses of Ultrahigh Lift Low Pressure Turbine Blades

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Chao Zhou ◽  
Howard Hodson ◽  
Christoph Himmel
Keyword(s):  
Turbine Blades ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Base Pressure ◽  
Manufacturing Cost ◽  
Surface Boundary ◽  
Trailing Edge ◽  
Low Pressure Turbine ◽  
Sst Model ◽  
Profile Loss

Experimental, numerical and analytical methods were used to investigate the effects of the blade trailing edge thickness on the profile loss of ultrahigh-lift low-pressure turbine blades. Two cascades, the T106C and the T2, were studied. The loss obtained based on the data at the blade trailing edge plane and the plane 0.3 Chord downstream of the trailing edge agree with each other for T106C blade with and without upstream wakes at different Reynolds numbers. The blade profile losses were broken down as the suction surface boundary loss, the pressure side boundary loss and the mixing loss downstream of the trailing edge for six Reynolds numbers. Trailing edge thicknesses varying from 1.4% to 4.7% pitch were investigated at a Reynolds number of 210,000. It was found that the flow distributions across the passage at the trailing edge planes were highly nonuniform. In particular, and as a result, the trailing edge base pressure was higher than the mixed-out static pressure, so the contribution of the base pressure to the mixing loss downstream of the trailing edge plane was to reduce the loss. When the trailing edge thickness increases, there are three main effects: (1) the area with high base pressure region increases, which tends to reduce the downstream mixing loss; (2) the base pressure reduces, which tends to increase the loss; and (3) the flow diffusion downstream of the trailing edge, which tends to increase the loss. The overall result is the combined effect. For the T106C cascade, increasing the trailing edge thickness from 1.9% pitch to 2.8% pitch has a small effect on the loss. Further increasing the trailing edge thickness increases the loss. The T2 blade has a higher lift than the T106C blade, so the effects of the base pressure in reducing the mixing loss downstream of the trailing edge is more evident. The experimental results show that the profile loss first decreases and then increases as the trailing edge thickness increases. CFD, using the transition k-ω SST model and the k-ω SST model, provides good predictions of the aerodynamic performance. It was used to study the cases with trailing edge thicknesses of 1.4% pitch and 2.9% pitch. The profile loss is almost the same for these two trailing edge thickness. The results show that it is possible to use thicker blade trailing edges in low pressure turbines without aerodynamic penalty. This can lead to benefits in terms of mechanical integrity and manufacturing cost reductions.

The Effects of Trailing Edge Thickness on the Losses of Ultra-High Lift LP Turbine Blades

2013 ◽  
Author(s):  
Chao Zhou ◽  
Howard Hodson ◽  
Christoph Himmel
Keyword(s):  
Turbine Blades ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Base Pressure ◽  
Manufacturing Cost ◽  
Surface Boundary ◽  
Trailing Edge ◽  
High Lift ◽  
Sst Model ◽  
Profile Loss

Experimental, numerical and analytical methods were used to investigate the effects of the blade trailing edge thickness on the profile loss of ultra-high lift low pressure turbine blades. Two cascades, the T106C and the T2, were studied. The loss obtained based on the data at the blade trailing edge plane and the plane 0.3 Chord downstream of the trailing edge agree with each other for T106C blade with and without upstream wakes at different Reynolds numbers. The blade profile losses were broken down as the suction surface boundary loss, the pressure side boundary loss and the mixing loss downstream of the trailing edge for six Reynolds numbers. Trailing edge thicknesses varying from 1.4% to 4.7% Pitch were investigated at a Reynolds number of 210000. It was found that the flow distributions across the passage at the trailing edge planes were highly non-uniform. In particular, and as a result, the trailing edge base pressure was higher than the mixed-out static pressure, so the contribution of the base pressure to the mixing loss downstream of the trailing edge plane was to reduce the loss. When the trailing edge thickness increases, there are three main effects: 1) The area with high base pressure region increase, which tends to reduce the downstream mixing loss; 2) The base pressure reduces, which tends to increase the loss; 3) The flow diffusion downstream of the trailing edge, which tends to increase the loss. The overall result is the combined effect. For the T106C cascade, increasing the trailing edge thickness from 1.9% Pitch to 2.8% Pitch has a small effect on the loss. Further increasing the trailing edge thickness increases the loss. The T2 blade has a higher lift than the T106C blade, so the effects of the base pressure in reducing the mixing loss downstream of the trailing edge is more evident. The experimental results show that the profile loss first decreases and then increases as the trailing edge thickness increases. CFD, using the transition k-ω SST model and the k-ω SST model, provides good predictions of the aerodynamic performance. It was used to study the cases with trailing edge thicknesses of 1.4% Pitch and 2.9% Pitch. The profile loss is almost the same for these two trailing edge thickness. The results show that it is possible to use thicker blade trailing edges in low pressure turbines without aerodynamic penalty. This can lead to benefits in terms of mechanical integrity and manufacturing cost reductions.

Influence of Mach Number on Profile Loss of Axial-Flow Gas Turbine Blades

2016 ◽  
Author(s):  
M. D. Kibsey ◽  
S. A. Sjolander
Keyword(s):  
Mach Number ◽  
Turbine Blades ◽  
Base Pressure ◽  
Current Profile ◽  
Trailing Edge ◽  
Complex Behaviour ◽  
Number Range ◽  
Profile Losses ◽  
Mach Numbers ◽  
Profile Loss

The current profile loss prediction methods for axial turbine blades usually predict a monotonic increase in profile losses at outlet Mach numbers above 1.0, while linear cascade testing in the literature has revealed a more complex behaviour. An objective of this investigation was to help clarify the flow features that are most influential on the profile losses in the transonic and supersonic regimes. Four linear cascades of turbine blades were investigated both experimentally and computationally, at design incidence. Measurements were carried out over an outlet Mach number range of roughly 0.5 to 1.4, and a Reynolds number range of about 5 × 105 to 1.4×106. It was found that the profile losses of the four cascades exhibited a loss “plateau”, where the total pressure loss coefficient became approximately constant over a range of outlet Mach numbers spanning the low supersonic range. Cascades of different geometries exhibited different extents of this loss plateau, and a commonly used Mach number correction for profile losses did not capture the behaviour. In the literature, a relationship has been observed between the base pressure and the profile losses. The base pressure was linked to the losses in the trailing edge wake and in the trailing edge shock system. For this reason, base pressure data were obtained from blades instrumented with a static tap at the trailing edge, and also from computational fluid dynamics (CFD). The results provided insight into the role of the base pressure in the profile losses through the transonic regime. It was concluded from this study that an accurate prediction of the base pressure may serve as a basis for a revised Mach number correction to be applied to the profile loss correlation in the transonic and supersonic flow regimes.

Computational Study of the Risø-B1-18 Airfoil with a Hinged Flap Providing Variable Trailing Edge Geometry

2005 ◽  
Vol 29 (2) ◽  
pp. 89-113 ◽  
Author(s):  
Niels Troldborg
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Computational Study ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Flow Conditions ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Edge Geometry ◽  
Fully Developed Turbulent Flow

A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Risø-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should be to decrease fatigue-inducing oscillations on the blades. The computations were conducted using a 2D incompressible RANS solver with a k-w turbulence model under the assumption of a fully developed turbulent flow. The investigations were conducted at a Reynolds number of Re = 1.6 · 106. Calculations conducted on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades. It is concluded that a moderately curved flap with flap chord to airfoil curve ratio between 0.05 and 0.10 would be an optimum choice.

Experimental and Numerical Investigation on the Performance of a Family of Three HP Transonic Turbine Blades

2004 ◽  
Author(s):  
D. Corriveau ◽  
S. A. Sjolander
Keyword(s):  
Flow Velocity ◽  
Turbine Blades ◽  
Suction Side ◽  
Experimental Results ◽  
Base Pressure ◽  
Suction Surface ◽  
Trailing Edge ◽  
Lower Base ◽  
Shock System ◽  
Transonic Turbine

Experimental results concerning the performance of three high-pressure (HP) transonic turbine blades having fore-, aft- and mid-loadings have been presented previously by Corriveau and Sjolander [1]. Results from that study indicated that by shifting the loading towards the rear of the airfoil, improvements in loss performance of the order of 20% could be obtained near the design Mach number. In order to gain a better understanding of the underlying reasons for the improved loss performance of the aft-loaded blade, additional measurements were performed on the three cascades. Furthermore, 2-D numerical simulations of the cascade flow were performed in order to help in the interpretation of the experimental results. Based on the analysis of additional wake traverse data and base pressure measurements combined with the numerical results, it was found that the poorer loss performance of the baseline mid-loaded profile compared to the aft-loaded blade could be traced back to the former’s higher rear suction side curvature. The presence of higher rear suction surface curvature resulted in higher flow velocity in that region. Higher flow velocity at the trailing edge in turn contributed to reducing the base pressure. The lower base pressure at the trailing edge resulted in a stronger trailing edge shock system for the mid-loaded blade. This shock system increased the losses for the mid-loaded baseline profile when compared to the aft-loaded profile.

Techniques for Aerodynamic Loss Measurement of Transonic Turbine Cascades With Trailing-Edge Region Coolant Ejection

1992 ◽  
Author(s):  
D. J. Mee
Keyword(s):  
Total Pressure ◽  
Free Stream ◽  
Turbine Blades ◽  
Flux Ratio ◽  
Edge Region ◽  
Trailing Edge ◽  
Aerodynamic Loss ◽  
Transonic Turbine ◽  
Turbine Cascades ◽  
Density Ratios

Experimental techniques associated with the measurement of loss of transonic turbine blades with trailing-edge region coolant ejection are considered. Results from experiments with different coolant to free stream gas density ratios indicate that it is not always adequate to simulate only the coolant blowing rate. However, for the measurement of loss, the present experimental results indicate that it may be adequate to simulate the momentum flux ratio. In loss calculations the value used for the total pressure of the coolant gas is discussed and shown to influence a comparison of different cooling geometries.

A study of three-dimensional aspects of vortex shedding from a bluff body with a mild geometric disturbance

1997 ◽  
Vol 330 ◽  
pp. 85-112 ◽  
Author(s):  
N. TOMBAZIS ◽  
P. W. BEARMAN
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Vortex Formation ◽  
Three Dimensional ◽  
Base Pressure ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Trailing Edges ◽  
Mode Transitions

Experiments have been carried out to study the three-dimensional characteristics of vortex shedding from a half-ellipse shape with a blunt trailing edge. In order to control the occurrence of vortex dislocations, the trailing edges of the models used were constructed with a series of periodic waves across their spans. Flow visualization was carried out in a water tunnel at a Reynolds number of 2500, based on trailing-edge thickness. A number of shedding modes were observed and the sequence of mode transitions recorded. Quantitative data were obtained from wind tunnel measurements performed at a Reynolds number of 40000. Two shedding frequencies were recorded with the higher frequency occurring at spanwise positions coinciding with minima in the chord. At these same positions the base pressure was lowest and the vortex formation length longest. Arguments are put forward to explain these observations. It is shown that the concept of a universal Strouhal number holds, even when the flow is three-dimensional. The spanwise variation in time-average base pressure is predicted using the estimated amount of time the flow spends at the two shedding frequencies.

Blade Trailing Edge Heat Transfer

1980 ◽  
Author(s):  
A. Brown ◽  
B. Mandjikas ◽  
J. M. Mudyiwa
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Internal Heat ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Trailing Edge ◽  
Pillar Diameter ◽  
Trailing Edges ◽  
Pillar Arrays ◽  
Internal Heat Transfer

In this article measurements of heat transfer, pressure loss, and friction factor inside simulated trailing edges of turbine blades are presented. The trailing edges considered are vented and the internal heat transfer surfaces are extended by means of staggered arrays of pillars interconnecting the blade pressure and suction surfaces. A number of pillar arrays and trailing edge configurations are considered, namely pillar pitch to diameter ratios nominally of 2, 3, and 4 and trailing edge included angles of 0, 10, 15, and 20 deg. The range of Reynolds numbers covered based on pillar diameter and maximum velocity through a row of pillars is from 104 to 2 × 105.

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