scholarly journals Loss classification and review of secondary flow models in gas turbine cascades

2020 ◽  
pp. 30-39
Author(s):  
Stanislav Piskunov ◽  
◽  
Denis Popov ◽  
Nikita Samoylenko ◽  
◽  
...  
Keyword(s):  
Total Pressure ◽  
Complete Classification ◽  
Review Article ◽  
Secondary Flows ◽  
Sources Of Information ◽  
Aerodynamic Efficiency ◽  
Flow Models ◽  
Turbofan Engines ◽  
Turbine Cascades

Much attention is paid to increasing the efficiency of turbofan engines by increasing the efficiency of the main modules. The aerodynamic efficiency of a turbine depends on the level of total pressure and kinetic energy losses, which are determined by the scale of secondary flows in the channels of the turbine cascades. There are many studies and articles on the topic of secondary flows, in which vortex structures are often given incorrect names. The problem lies in the absence of a unified model of secondary flows and mismatch in the names of the components of secondary flows in adaptation of model descriptions from English to Russian. The purpose of this review article is to consider the existing classifications of losses and the most famous models of secondary flows in turbine cascades, including the Wang model, the Goldstein and Spores model, the Sharma and Butler model, etc. The considered sources of information made it possible to single out the most complete classification of losses, compare with each other the components of secondary flows of various models, describe the mechanism of their occurrence and give the most complete nomenclature of secondary flows in turbine cascades.

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.

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

1986 ◽  
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°. A full representation of superimposed secondary flow vectors and loss contours is given at serial fourteen traverse planes located throughout the cascade, which 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°.

The Meander Paradox—A Topological View

2010 ◽  
Vol 63 (2) ◽  
Author(s):  
Albert Gyr
Keyword(s):  
Sediment Transport ◽  
Review Article ◽  
Secondary Flows ◽  
Meandering River ◽  
Least Action ◽  
General Manner ◽  
Principle Of Least Action ◽  
Different Types

Meanders are puzzling phenomena because a meandering river seems to contradict the principle of least action. Different approaches to explain this paradox are outlined by adopting a topological view, which allows for a classification of different types of meanders and to discuss the relevant mechanisms in a rather general manner. It is shown that secondary flows of helical type are the features responsible for the increase in the sediment transport when the slope of rivers decreases due to meandering and that the increase in the discharge is due to a partial Beltramisation of the flow and to a reduction in the friction at the boundary of the helical cells. The review article contains 78 references.

Application of Endwall Contouring to Transonic Turbine Cascades: Experimental Measurements at Design Conditions

2011 ◽  
Author(s):  
F. Taremi ◽  
S. A. Sjolander ◽  
T. J. Praisner
Keyword(s):  
Kinetic Energy ◽  
Flow Visualization ◽  
Flow Regime ◽  
Total Pressure ◽  
Surface Flow ◽  
Secondary Flows ◽  
Experimental Results ◽  
Pressure Losses ◽  
Turbine Cascades ◽  
Endwall Contouring

An experimental investigation of the endwall flows in two transonic linear turbine cascades was presented at the 2010 ASME Turbo Expo (GT2010–22760). Endwall contouring was subsequently implemented in these cascades to control the secondary flows, and reduce the total pressure losses. The current paper presents experimental results from these cascades to assess the effectiveness of endwall contouring in the transonic flow regime. The experimental results include blade loadings, total pressure losses, streamwise vorticity and secondary kinetic energy distributions. In addition, surface flow visualization results are presented in order to interpret the endwall limiting streamlines within the blade passages. The flat-endwall and contoured-endwall cascades produce very similar midspan loading distributions and profile losses, but exhibit different secondary flows. The endwall surface flow visualization results indicate weaker interaction between the secondary flows and the blade suction surface boundary layers in the contoured cascades. Overall, the implementation of endwall contouring results in smaller and less intense vortical structures, and the reduction of the associated secondary kinetic energy (SKE) and exit flow angle variations. However, the mass-averaged losses at the main measurement plane, located 40% axial chord lengths downstream of the cascade (1.4CX), do not corroborate the numerically predicted improvements for the contoured cascades. This is in part attributed to slower mixing rates of the secondary flows in the compressible flow regime. The mass-averaged results at 2.0CX, on the other hand, show smaller losses for the contoured cascades associated with smaller SKE dissipation downstream of the cascades. Accordingly, the mixed-out row losses also show improvements for the contoured cascades.

Application of Endwall Contouring to Transonic Turbine Cascades: Experimental Measurements at Design Conditions

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Farzad Taremi ◽  
Steen A. Sjolander ◽  
Thomas J. Praisner
Keyword(s):  
Kinetic Energy ◽  
Flow Visualization ◽  
Flow Regime ◽  
Total Pressure ◽  
Surface Flow ◽  
Secondary Flows ◽  
Pressure Losses ◽  
Turbine Cascades ◽  
Endwall Contouring ◽  
Surface Flow Visualization

An experimental investigation of the endwall flows in two high-turning turbine cascades was presented by Taremi et al. (2010, “Measurements of Endwall Flows in Transonic Linear Turbine Cascades: Part II—High Flow Turning,” ASME Conf. Proc., GT2010-22760, pp. 1343–1356). Endwall contouring was subsequently implemented in these cascades to control the secondary flows and reduce the total pressure losses. The current paper presents experimental results from these cascades to assess the effectiveness of endwall contouring in the transonic flow regime. The results include blade loadings, total pressure losses, streamwise vorticity and secondary kinetic energy distributions. In addition, surface flow visualization results are presented in order to interpret the endwall limiting streamlines within the blade passages. The flat-endwall and contoured-endwall cascades produce very similar midspan loading distributions and profile losses, but exhibit different secondary flows. The endwall surface flow visualization results indicate weaker interaction between the secondary flows and the blade suction surface boundary layers in the contoured cascades. Overall, the implementation of endwall contouring results in smaller and less intense vortical structures, and the reduction of the associated secondary kinetic energy (SKE) and exit flow angle variations. However, the mass-averaged losses at the main measurement plane, located 40% axial chord lengths downstream of the cascade (1.4CX), do not corroborate the numerically predicted improvements for the contoured cascades. This is in part attributed to slower mixing rates of the secondary flows in the compressible flow regime. The mass-averaged results at 2.0CX, on the other hand, show smaller losses for the contoured configurations associated with smaller SKE dissipation downstream of the cascades. Accordingly, the mixed-out row losses also show improvements for the contoured cascades.

scholarly journals Multiplicative automatic sequences

2021 ◽  
Author(s):  
Jakub Konieczny ◽  
Mariusz Lemańczyk ◽  
Clemens Müllner
Keyword(s):  
Complete Classification ◽  
Automatic Sequences ◽  
Complex Valued

AbstractWe obtain a complete classification of complex-valued sequences which are both multiplicative and automatic.

scholarly journals Characteristic cohomology and observables in higher spin gravity

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Alexey Sharapov ◽  
Evgeny Skvortsov
Keyword(s):  
Higher Spin Gravity ◽  
Complete Classification ◽  
Gravity Models ◽  
Simons Theory ◽  
Surface Charges ◽  
Higher Spin ◽  
Dynamical Invariants ◽  
Chern Simons ◽  
Conserved Currents

Abstract We give a complete classification of dynamical invariants in 3d and 4d Higher Spin Gravity models, with some comments on arbitrary d. These include holographic correlation functions, interaction vertices, on-shell actions, conserved currents, surface charges, and some others. Surprisingly, there are a good many conserved p-form currents with various p. The last fact, being in tension with ‘no nontrivial conserved currents in quantum gravity’ and similar statements, gives an indication of hidden integrability of the models. Our results rely on a systematic computation of Hochschild, cyclic, and Chevalley-Eilenberg cohomology for the corresponding higher spin algebras. A new invariant in Chern-Simons theory with the Weyl algebra as gauge algebra is also presented.

scholarly journals Nil-clean quadratic elements

2017 ◽  
Vol 16 (10) ◽  
pp. 1750197 ◽  
Author(s):  
Janez Šter
Keyword(s):  
Complete Classification ◽  
Strong Condition ◽  
Clean Rings

We provide a strong condition holding for nil-clean quadratic elements in any ring. In particular, our result implies that every nil-clean involution in a ring is unipotent. As a consequence, we give a complete classification of weakly nil-clean rings introduced recently in [Breaz, Danchev and Zhou, Rings in which every element is either a sum or a difference of a nilpotent and an idempotent, J. Algebra Appl. 15 (2016) 1650148, doi: 10.1142/S0219498816501486].

Effect of the turning angle on the flow and performance characteristics of long S-shaped circular diffusers

2003 ◽  
Vol 217 (1) ◽  
pp. 29-41 ◽  
Author(s):  
R B Anand ◽  
L Rai ◽  
S N Singh
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Area Ratio ◽  
Secondary Flows ◽  
Performance Characteristics ◽  
Pressure Recovery ◽  
Recovery Coefficient ◽  
Turning Angle ◽  
And Performance ◽  
Pressure Recovery Coefficient

The effect of the turning angle on the flow and performance characteristics of long S-shaped circular diffusers (length-inlet diameter ratio, L/Di = 11:4) having an area ratio of 1.9 and centre-line length of 600 mm has been established. The experiments are carried out for three S-shaped circular diffusers having angles of turn of 15°/15°, 22.5°/22.5° and 30°/30°. Velocity, static pressure and total pressure distributions at different planes along the length of the diffusers are measured using a five-hole impact probe. The turbulence intensity distribution at the same planes is also measured using a normal hot-wire probe. The static pressure recovery coefficients for 15°/15°, 22.5°/22.5° and 30°/30° diffusers are evaluated as 0.45, 0.40 and 0.35 respectively, whereas the ideal static pressure recovery coefficient is 0.72. The low performance is attributed to the generation of secondary flows due to geometrical curvature and additional losses as a result of the high surface roughness (~0.5 mm) of the diffusers. The pressure recovery coefficient of these circular test diffusers is comparatively lower than that of an S-shaped rectangular diffuser of nearly the same area ratio, even with a larger turning angle (90°/90°), i.e. 0.53. The total pressure loss coefficient for all the diffusers is nearly the same and seems to be independent of the angle of turn. The flow distribution is more uniform at the exit for the higher angle of turn diffusers.

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