The Aerodynamics of Trailing-Edge-Cooled Transonic Turbine Blades: Part 2 — Theoretical and Computational Approach

1997 ◽  
Author(s):  
Mathias Deckers ◽  
John D. Denton
Keyword(s):  
Transonic Flow ◽  
Theoretical Study ◽  
Computational Study ◽  
Control Volume ◽  
Turbine Blades ◽  
Computational Approach ◽  
Trailing Edge ◽  
Time Marching ◽  
Transonic Turbine ◽  
Volume Method

A theoretical and computational study into the aerodynamics of trailing-edge-cooled transonic turbine blades is described in this part of the paper. The theoretical study shows that, for unstaggered blades with coolant ejection, the base pressure and overall loss can be determined exactly by a simple control volume analysis. This theory suggests that a thick, cooled trailing edge with a wide slot can be more efficient than a thin, solid trailing edge. An existing time-marching finite volume method is adapted to calculate the transonic flow with trailing edge coolant ejection on a structured, quasi-orthogonal mesh. Good overall agreement between the present method, inviscid and viscous, and experimental evidence is obtained.

Investigations of Transonic Turbine Cascade With High Stagger and Low Solidity

1979 ◽  
Author(s):  
M. Inoue ◽  
S. Yamaguchi ◽  
M. Kuroumaru
Keyword(s):  
Transonic Flow ◽  
Laval Nozzle ◽  
Experimental Studies ◽  
Flow Characteristics ◽  
Chord Length ◽  
Turbine Cascade ◽  
Trailing Edge ◽  
Time Marching ◽  
Shock System ◽  
Transonic Turbine

In order to clarify the transonic flow characteristics of a turbine cascade with high stagger, low solidity and small deflections, experimental studies were carried out by shortening the chord length of a “Laval-nozzle shaped” blade with thick trailing edge. The behavior of the shock system depends on the amount of overlap between the blades. The relations between the behavior and the performances were discussed in detail. The results may be applied to more standard sections. Lastly, validity of an appropriate time marching analysis for the highly staggered cascade was investigated by comparing with the experiment.

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.

A Simple Procedure to Compute Losses in Transonic Turbines Cascades

1985 ◽  
Author(s):  
Francesco Martelli ◽  
Alberto Boretti
Keyword(s):  
Transonic Flow ◽  
Simple Procedure ◽  
Turbine Blades ◽  
Wave Interaction ◽  
Integral Boundary ◽  
Shock Wave Interaction ◽  
Time Requirements ◽  
Time Marching ◽  
Shock System ◽  
Marching Method

The prediction of losses in transonic flow in turbines is an important step in the design of turbine stages, but at the same time requirements of simplicity and speed are needed to allow the work of designers. The paper presents a procedure developed to match this goal. It uses classical codes, experimental correlations and simple geometrical models of the shock system. The result of a time marching method with standard mesh is used to run an Integral Boundary layer calculation in which shock wave interaction effects have been included. The shock system is made up of this information plus empirical correlation and a suitable procedure. A mixing calculation is then performed to get the downstream total pressure. The method has been tested with various kinds of turbine blades of which losses and data for calculations have been published. The results are quite good and the procedure appears simple and fast.

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.

Investigation on the Reduction of Trailing Edge Shock Losses for a Highly Loaded Transonic Turbine

2016 ◽  
Author(s):  
Wei Zhao ◽  
Weiwei Luo ◽  
Qingjun Zhao ◽  
Jianzhong Xu
Keyword(s):  
Turbine Blades ◽  
Strong Shock ◽  
Suction Side ◽  
Loss Reduction ◽  
Blade Profile ◽  
Trailing Edge ◽  
Pressure Loss Coefficient ◽  
Reflected Shock ◽  
Transonic Turbine ◽  
Highly Loaded

A shock loss reduction method for highly loaded transonic turbine blades with convergent passages is presented. The method is illustrated with an improved blade profile that employs a negative curvature curve on its uncovered suction side. The improved profile and a conventional baseline profile are applied to two cascades with the same solidity, chord and aspect ratio respectively. The numerical simulation results for the two cascades show that a reduction of 4.58% in the total pressure loss coefficient is obtained for the improved profile at the design condition. The effects of back pressures on the performance of both cascades are also presented, and the improved blade profile shows a much better part-load performance. The paper compares the flow fields of the baseline and the improved blade profiles to understand loss reduction mechanism especially by analyzing the shock interactions downstream of the trailing edge. It is found that, for the improved profile, the reflected shock of pressure side leg of the trailing-edge shock rotates forward and the suction side leg of the trailing-edge shock rotates backward. Therefore, the two shocks delay their intersection points where they merge into a relatively strong shock, and consequently produce less shock losses than those of the baseline profile.

The Trailing Edge Loss of Transonic Turbine Blades

1990 ◽  
Vol 112 (2) ◽  
pp. 277-285 ◽  
Author(s):  
J. D. Denton ◽  
L. Xu
Keyword(s):  
Surface Pressure ◽  
Turbine Blades ◽  
Back Pressure ◽  
Base Pressure ◽  
Mass Energy ◽  
Suction Surface ◽  
Trailing Edge ◽  
Transonic Turbine ◽  
Energy And Momentum ◽  
Unique Relationship

Trailing edge loss is one of the main sources of loss for transonic turbine blades, contributing typically 1/3 of their total loss. Transonic trailing edge flow is extremely complex, the basic flow pattern is understood but methods of predicting the loss are currently based on empirical correlations for the base pressure. These correlations are of limited accuracy. Recent findings that the base pressure and loss can be reasonably well predicted by inviscid Euler calculations are justified and explained in this paper. For unstaggered choked blading, it is shown that there is a unique relationship between the back pressure and the base pressure and any calculation that conserves mass, energy and momentum should predict this relationship and the associated loss exactly. For realistic staggered blading, which operates choked but with subsonic axial velocity, there is also a unique relationship between the back pressure and the base pressure (and hence loss) but the relationship cannot be quantified without knowing a further relationship between the base pressure and the average suction surface pressure downstream of the throat. Any calculation that conserves mass, energy and momentum and also predicts this average suction surface pressure correctly will again predict the base pressure and loss. Two-dimensional Euler solutions do not predict the suction surface pressure exactly because of shock smearing but nevertheless seem to give reasonably accurate results. The effects of boundary layer thickness and trailing edge coolant ejection are considered briefly. Coolant ejection acts to reduce the mainstream loss. It is shown that suction surface curvature downstream of the throat may be highly beneficial in reducing the loss of blades with thick trailing edges operating at high subsonic or low supersonic outlet Mach numbers.

scholarly journals The Aerodynamics of Trailing-Edge-Cooled Transonic Turbine Blades: Part 1 — Experimental Approach

1997 ◽  
Author(s):  
Mathias Deckers ◽  
John D. Denton
Keyword(s):  
Turbine Blades ◽  
Base Pressure ◽  
Stagnation Temperature ◽  
Trailing Edge ◽  
Static Pressure Distribution ◽  
Discernible Effect ◽  
Two Dimensional Flow ◽  
Shock System ◽  
Flow Through ◽  
Transonic Turbine

The research presented in this part of the paper involved a detailed experimental study of the flow through transonic turbine blading with trailing edge coolant ejection. The tests were carried out on (nearly) flat plate models representing the region of uncovered turning downstream of the throat. The investigation focused on the aerodynamic aspects associated with trailing edge ejection in steady two-dimensional flow over a range of exit Mach numbers, coolant pressure ratios and temperature ratios. The experiments showed that the simple existence of the coolant cavity leads to a substantial change of the flow field in the near wake. Consequently, the slotted unblown base was found to have considerably less loss than the solid one. The effect of coolant ejection is shown to cause a substantial increase in base pressure and reduction in overall loss. The surface static pressure distribution and boundary layers were affected by the coolant in two ways: directly from downstream, via the base pressure, and indirectly through a changed trailing edge shock system. However, the coolant stagnation temperature ratio was found to have no discernible effect on the base pressure and loss.

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.

An Investigation of a Highly Loaded Transonic Turbine Stage With Compound Leaned Vanes

1986 ◽  
Vol 108 (2) ◽  
pp. 265-269 ◽  
Author(s):  
Jing Shi ◽  
Jianyuan Han ◽  
Shiying Zhou ◽  
Mingfu Zhu ◽  
Yaoko Zhang ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Velocity Profile ◽  
Three Dimensional ◽  
Turbine Stage ◽  
Time Marching ◽  
Overall Performance ◽  
Transonic Turbine ◽  
Volume Method ◽  
Stage Efficiency ◽  
Highly Loaded

An investigation was made to compare the performance of a highly loaded transonic turbine stage with and without compound leaned vanes. In both cases, velocity distribution along the vane surfaces was calculated from a full three-dimensional time-marching finite volume method. Nozzles were tested in a wind tunnel. Through rig tests, velocity profile at the stage exit was measured and the stage overall performance obtained. Performance in both tip and hub regions was improved by using the compound leaned vanes so that the stage efficiency increased by approximately 1 percent. The improvement is particularly remarkable at off-design points.

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