Experimentally Observed Unsteady Work at Inlet to and Exit From an Axial Flow Turbine Rotor

2012 ◽  
Author(s):  
Martin G. Rose ◽  
Philipp Jenny ◽  
Jochen Gier ◽  
Reza S. Abhari
Keyword(s):  
World Literature ◽  
Static Pressure ◽  
Free Stream ◽  
Axial Flow ◽  
Fast Response ◽  
Turbine Rotor ◽  
Work Distribution ◽  
Wake Interaction ◽  
Absolute Frame ◽  
The Relationship

World literature has introduced the aerodynamic importance of unsteadiness in turbines. In particular the unsteady static pressure field determines the work of the machine. The unsteadiness can redistribute the total pressure in a cascade with wake interaction. It has been shown that differences in work between wake and free-stream can act to rectify the wakes and boost efficiency. In this paper FRAP (Fast Response Aerodynamic Probe) data is used to study the nature of the unsteady work in the flow at entry to and exit from a rotating turbine blade. The topic is addressed experimentally, theoretically and computationally. It is found at both rotor inlet and exit that upstream wakes influence the unsteady work distribution. The relationship between the unsteady work in the absolute frame, the relative frame and the momentum of the fluid circumferentially is derived and verified experimentally. Computational results (URANS) are compared to the experimental results: reasonable agreement is found at rotor exit but significant differences at rotor inlet are found. The CFD has failed to capture the von Karman vortices and has dramatically lower levels of unsteady work. The experimental unsteady work distribution suggests possible effects of wake bending and vortex instability.

Experimentally Observed Unsteady Work at Inlet to and Exit From an Axial Flow Turbine Rotor

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Martin G. Rose ◽  
Philipp Jenny ◽  
Jochen Gier ◽  
Reza S. Abhari
Keyword(s):  
World Literature ◽  
Axial Flow ◽  
Fast Response ◽  
Turbine Rotor ◽  
Navier Stokes ◽  
Work Distribution ◽  
Wake Interaction ◽  
Computational Fluid Dynamics Cfd ◽  
Absolute Frame ◽  
The Relationship

World literature has introduced the aerodynamic importance of unsteadiness in turbines. In particular, the unsteady static pressure field determines the work of the machine. The unsteadiness can redistribute the total pressure in a cascade with wake interaction. It has been shown that differences in work between wake and free stream can act to rectify the wakes and boost efficiency. In this paper, fast response aerodynamic probe (FRAP) data are used to study the nature of the unsteady work in the flow at entry to and exit from a rotating turbine blade. The topic is addressed experimentally, theoretically, and computationally. It is found at both rotor inlet and exit that upstream wakes influence the unsteady work distribution. The relationship between the unsteady work in the absolute frame, the relative frame, and the momentum of the fluid circumferentially is derived and verified experimentally. Computational results (unsteady Reynolds-averaged Navier–Stokes (URANS)) are compared to the experimental results: reasonable agreement is found at rotor exit, but significant differences at rotor inlet are found. The computational fluid dynamics (CFD) has failed to capture the von Karman vortices and has dramatically lower levels of unsteady work. The experimental unsteady work distribution suggests possible effects of wake bending and vortex instability.

Stall Inception and Development in an Axial Flow Aeroengine

1994 ◽  
Vol 116 (2) ◽  
pp. 216-225 ◽  
Author(s):  
A. G. Wilson ◽  
C. Freeman
Keyword(s):  
High Speed ◽  
Engine Speed ◽  
Static Pressure ◽  
Flow Instability ◽  
Axial Flow ◽  
Fast Response ◽  
Rotating Stall ◽  
Flow Disturbance ◽  
Stall Inception ◽  
Small Flow

This paper describes the phenomenon of stall and surge in an axial flow aeroengine using fast response static pressure measurements from the compressor of a Rolls-Royce VIPER engine. It details the growth of flow instability at various speeds, from a small zone of stalled fluid involving only a few blades into the violent surge motion of the entire machine. Various observations from earlier theoretical and compressor rig results are confirmed by these new engine measurements. The main findings are as follows: (1) The point of stall inception moves rearward as engine speed increases, and is shown to be simply related to the axial matching of the compressor. (2) The final unstable operation of the machine can be divided into rotating stall at low speed and surge or multiple surge at high speed. (3) The inception process is independent of whether the final unstable operation is rotating stall or multiple surge. (4) Stall/surge always starts as a circumferentially small flow disturbance, rotating around the annulus at some fraction of rotor speed.

scholarly journals Stall Inception and Development in an Axial Flow Aeroengine

1993 ◽  
Author(s):  
Alexander G. Wilson ◽  
Chris Freeman
Keyword(s):  
High Speed ◽  
Engine Speed ◽  
Static Pressure ◽  
Flow Instability ◽  
Axial Flow ◽  
Fast Response ◽  
Rotating Stall ◽  
Flow Disturbance ◽  
Stall Inception ◽  
Small Flow

This paper describes the phenomenon of stall and surge in an axial flow aeroengine using fast response static pressure measurements from the compressor of a Rolls-Royce VIPER engine. It details the growth of flow instability at various speeds, from a small zone of stalled fluid involving only a few blades into the violent surge motion of the entire machine. Various observations from earlier theoretical and compressor rig results are confirmed by these new engine measurements. The main findings are as follows: 1. The point of stall inception moves rearwards as engine speed increases, and is shown to be simply related to the axial matching of the compressor. 2. The final unstable operation of the machine can be divided into rotating stall at low speed and surge or multiple surge at high speed. 3. The inception process is independent of whether the final unstable operation is rotating stall or multiple surge. 4. Stall/surge always starts as a circumferentially small flow disturbance, rotating around the annulus at some fraction of rotor speed.

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

1994 ◽  
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.

Unsteady Numerical Simulation of Shock Systems in Vaneless Counter-Rotating Turbine

2005 ◽  
Author(s):  
Huishe Wang ◽  
Qingjun Zhao ◽  
Xiaolu Zhao ◽  
Jianzhong Xu
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Nozzle Design ◽  
Suction Surface ◽  
Rotor Wake ◽  
Wake Interaction ◽  
Unsteady Numerical Simulation ◽  
Almost All

A detailed unsteady numerical simulation has been carried out to investigate the shock systems in the high pressure (HP) turbine rotor and unsteady shock-wake interaction between coupled blade rows in a 1+1/2 counter-rotating turbine (VCRT). For the VCRT HP rotor, due to the convergent-divergent nozzle design, along almost all the span, fishtail shock systems appear after the trailing edge, where the pitch averaged relative Mach number is exceeding the value of 1.4 and up to 1.5 approximately (except the both endwalls). A group of pressure waves create from the suction surface after about 60% axial chord in the VCRT HP rotor, and those waves interact with the inner-extending shock (IES). IES first impinges on the next HP rotor suction surface and its echo wave is strong enough and cannot be neglected, then the echo wave interacts with the HP rotor wake. Strongly influenced by the HP rotor wake and LP rotor, the HP rotor outer-extending shock (OES) varies periodically when moving from one LP rotor leading edge to the next. In VCRT, the relative Mach numbers in front of IES and OES are not equal, and in front of IES, the maximum relative Mach number is more than 2.0, but in front of OES, the maximum relative Mach number is less than 1.9. Moreover, behind IES and OES, the flow is supersonic. Though the shocks are intensified in VCRT, the loss resulted in by the shocks is acceptable, and the HP rotor using convergent-divergent nozzle design can obtain major benefits.

Influence of Leading Edge Fillet and Nonaxisymmetric Contoured Endwall on Turbine NGV Exit Flow Structure and Interactions With the Rim Seal Flow

2013 ◽  
Author(s):  
Özhan H. Turgut ◽  
Cengiz Camcı
Keyword(s):  
Flow Structure ◽  
Total Pressure ◽  
Guide Vane ◽  
Axial Flow ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Constant Thickness ◽  
Computational Evaluation ◽  
Nozzle Guide

Three different ways are employed in the present paper to reduce the secondary flow related total pressure loss. These are nonaxisymmetric endwall contouring, leading edge (LE) fillet, and the combination of these two approaches. Experimental investigation and computational simulations are applied for the performance assessments. The experiments are carried out in the Axial Flow Turbine Research Facility (AFTRF) having a diameter of 91.66cm. The NGV exit flow structure was examined under the influence of a 29 bladed high pressure turbine rotor assembly operating at 1300 rpm. For the experimental measurement comparison, a reference Flat Insert endwall is installed in the nozzle guide vane (NGV) passage. It has a constant thickness with a cylindrical surface and is manufactured by a stereolithography (SLA) method. Four different LE fillets are designed, and they are attached to both cylindrical Flat Insert and the contoured endwall. Total pressure measurements are taken at rotor inlet plane with Kiel probe. The probe traversing is completed with one vane pitch and from 8% to 38% span. For one of the designs, area averaged loss is reduced by 15.06%. The simulation estimated this reduction as 7.11%. Computational evaluation is performed with the rotating domain and the rim seal flow between the NGV and the rotor blades. The most effective design reduced the mass averaged loss by 1.28% over the whole passage at the NGV exit.

Influence of Turbulent Flow Characteristics and Coherent Vortices on the Pressure Recovery of Annular Diffusers: Part A — Experimental Results

2015 ◽  
Author(s):  
Marcus Kuschel ◽  
Bastian Drechsel ◽  
David Kluß ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Static Pressure ◽  
Turbulent Transport ◽  
Axial Flow ◽  
Pressure Recovery ◽  
Turbulence Structure ◽  
Reynolds Stresses ◽  
Wide Range ◽  
Operating Points

Exhaust diffusers downstream of turbines are used to transform the kinetic energy of the flow into static pressure. The static pressure at the turbine outlet is thus decreased by the diffuser, which in turn increases the technical work as well as the efficiency of the turbine significantly. Consequently, diffuser designs aim to achieve high pressure recovery at a wide range of operating points. Current diffuser design is based on conservative design charts, developed for laminar, uniform, axial flow. However, several previous investigations have shown that the aerodynamic loading and the pressure recovery of diffusers can be increased significantly if the turbine outflow is taken into consideration. Although it is known that the turbine outflow can reduce boundary layer separations in the diffuser, less information is available regarding the physical mechanisms that are responsible for the stabilization of the diffuser flow. An analysis using the Lumley invariance charts shows that high pressure recovery is only achieved for those operating points in which the near-shroud turbulence structure is axi-symmetric with a major radial turbulent transport component. This turbulent transport originates mainly from the wake and the tip vortices of the upstream rotor. These structures energize the boundary layer and thus suppress separation. A logarithmic function is shown that correlates empirically the pressure recovery vs. the relevant Reynolds stresses. The present results suggest that an improved prediction of diffuser performance requires modeling approaches that account for the anisotropy of turbulence.

Ntrauterine programming of women’s health as a determinant of the reproductive potential of a population

2017 ◽  
pp. 10-15
Author(s):  
L.G. Nazarenko ◽  
◽  
N.S. Nestertsova ◽  
Keyword(s):  
World Literature ◽  
System Development ◽  
Reproductive Potential ◽  
The Body ◽  
Large For Gestational Age ◽  
Relevant Research ◽  
Gynecological Diseases ◽  
The World ◽  
Oncological Diseases ◽  
The Relationship

The relationship between the body weight of women at birth and the development in the future of gynecological diseases or deviations in the development of the reproductive system, development of oncological diseases and the timing of menopause have been analyzed. The results of clinical studies conducted at different times in different countries of the world, which cover the topic of this article, are presented. An overview of the world literature presented in the article, substantiates the relevance of conducting relevant research in the Ukrainian population. Key words: low birth weight, large-for-gestational-age fetus, gynecology disease.

scholarly journals Dancing with Myriam: Creating and Staging a New Metaphor for the Process of Translation

2015 ◽  
Vol 7 (1) ◽  
pp. 71
Author(s):  
Paula Pratt
Keyword(s):  
Literary Criticism ◽  
World Literature ◽  
African Women ◽  
Literary Texts ◽  
North African ◽  
Translation Process ◽  
Oral Interpretation ◽  
Doctoral Work ◽  
As Relationship ◽  
The Relationship

This article tells the story, and analyzes the development, of a “staged metaphor” for the translation process, from its chance inception over ten years ago, to the more recent revision and staging of the script. In 2005, I was teaching world literature at Al Akhawayn University in Ifrane, Morocco, while also researching the writing of Irish and North African women. I chose to focus on those women writing in Irish, Tachelhit, Arabic, or French, whose work had been translated into English. I was initially inspired by Nuala Ni Dhomhnaill’s poem, “The Language Issue,” which compares the "sending forth" of her writing to a potential reader, to the story of Moses being discovered by Pharoah’s daughter. My ultimate goal was to produce a chamber theatre play, based on the Irish and North African texts, which would dramatize a metaphor for the translation process. This was an outgrowth of my doctoral work, in which I had drawn on oral interpretation theorists, who see the performance of literary texts as an accepted means of doing literary criticism. Accordingly, I also expanded the project to include the observations of translation theorists, and I incorporated these into the creation of the script for a chamber theatre performance. After directing a staging of the script in Morocco in 2007, I realized that I needed to add more choreographed movement, and to incorporate the character of Moses’s and Myriam’s mother into the metaphor. The addition of dance, and the foregrounding of the relationship between Myriam and her mother, draws unapologetically on female relationships. It is my conclusion that the revised metaphor, with the addition of these elements, is validated by Yves Bonnefoy’s and Henri Meschonnic's depictions of “translation as relationship with an author,” and that, the metaphor does indeed “provide . . . fresh insights.”

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