Three Component Velocity Field Measurements in the Stagnation Region of a Film Cooled Turbine Vane

2002 ◽  
Vol 124 (3) ◽  
pp. 445-452 ◽  
Author(s):  
Marc D. Polanka ◽  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Field Measurements ◽  
The Other ◽  
Test Facility ◽  
Laser Doppler Velocimeter ◽  
Stagnation Region ◽  
Turbine Engine ◽  
Mainstream Flow ◽  
Turbine Vane ◽  
Component Velocity ◽  
Very High

The showerhead region of a film-cooled turbine vane in a gas turbine engine involves a complex interaction between mainstream flow and coolant jets. This flow field was studied using three component laser Doppler velocimeter measurements in a simulated turbine vane test facility. Measurements were focused around the stagnation row of holes. Low and high mainstream turbulence conditions were used. The spanwise orientation of the coolant jets, typical for showerhead coolant holes, had a dominating effect. Very high levels of turbulence were generated by the mainstream interaction with the coolant jets. Furthermore, this turbulence was highly anisotropic, with the spanwise component of the turbulent fluctuations being twice as large as the other components. Finally, there was an interaction of the high mainstream turbulence with the coolant injection resulting in increased turbulence levels for the spanwise velocity component, but had little effect on the other velocity components.

Three Component Velocity Field Measurements in the Stagnation Region of a Film Cooled Turbine Vane

2001 ◽  
Author(s):  
Marc D. Polanka ◽  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Field Measurements ◽  
The Other ◽  
Test Facility ◽  
Laser Doppler Velocimeter ◽  
Stagnation Region ◽  
Turbine Engine ◽  
Mainstream Flow ◽  
Turbine Vane ◽  
Component Velocity ◽  
Very High

The showerhead region of a film cooled turbine vane in a gas turbine engine involves a complex interaction between mainstream flow and coolant jets. This flow field was studied using three-component laser Doppler velocimeter measurements in a simulated turbine vane test facility. Measurements were focused around the stagnation row of holes. Low and high mainstream turbulence conditions were used. The spanwise orientation of the coolant jets, typical for showerhead coolant holes, had a dominating effect. Very high levels of turbulence were generated by the mainstream interaction with the coolant jets. Furthermore, this turbulence was highly anisotropic, with the spanwise component of the turbulent fluctuations being twice as large as the other components. Finally, there was an interaction of the high mainstream turbulence with the coolant injection resulting in increased turbulence levels for the spanwise velocity component, but had little effect on the other velocity components.

Thermal Field and Flow Visualization Within the Stagnation Region of a Film Cooled Turbine Vane

2001 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Flow Visualization ◽  
Film Cooling ◽  
Laser Doppler Velocimetry ◽  
Thermal Field ◽  
Velocity Fields ◽  
Stagnation Region ◽  
Physical Mechanisms ◽  
Mainstream Flow ◽  
Turbine Vane ◽  
Adiabatic Effectiveness

To develop quality computational codes for the film cooling of a turbine vane, a detailed understanding is needed of the physical mechanisms of the mainstream-coolant interactions. In this study flow visualization, thermal profiles, and laser Doppler velocimetry measurements were used to define the thermal and velocity fields of the film cooled showerhead region of a turbine vane. The showerhead consisted of six rows of spanwise oriented coolant holes, and blowing ratios ranged from 0.8 to 2.5. Performances with low and high mainstream turbulence levels were tested. Coolant jets from the showerhead were completely separated from the surface even at relatively low blowing ratios. However, the interaction of the coolant jets from laterally adjacent holes created a barrier to the mainstream flow, resulting in relatively high adiabatic effectiveness.

scholarly journals Film Cooling Effectiveness in the Showerhead Region of a Gas Turbine Vane: Part I — Stagnation Region and Near-Pressure Side

1999 ◽  
Author(s):  
Marc D. Polanka ◽  
Virginia C. Witteveld ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Test Facility ◽  
Experimental Program ◽  
Pressure Side ◽  
Stagnation Region ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
The Impact

An experimental program to study film cooling adiabatic effectiveness in the showerhead region of a turbine vane was completed. A typical first stage turbine stator vane was modeled in a nine-times scale, low speed test facility. The leading edge showerhead consisted of a row of holes at the stagnation point of the vane as well as two rows on the pressure surface and three rows on the suction surface. Film cooling performance on the pressure side of the showerhead is described in this paper. Experiments were conducted for a number of blowing ratios, from 0.3 to 2.9, and at a density ratio of nominally 1.8. The impact of high mainstream turbulence was studied by comparing performance at turbulence levels of 0.5% and 22%. The sensitivity to the stagnation line position was also investigated. The approaching stagnation line was positioned either directly on the stagnation row of holes or just to the suction side of that row. With the stagnation line directly on the stagnation row of holes at low turbulence, the direction of the coolant jets was observed to vary along the span of the airfoil. At high turbulence, this same effect did not occur. Moreover, at the high mainstream turbulence level, the coolant from the entire stagnation row of holes seemed to be spread more evenly throughout the stagnation region. At high blowing ratios, this resulted in higher effectiveness values in the stagnation region. Farther downstream, the high mainstream turbulence reduced the effectiveness at all blowing ratios.

Thermal Field and Flow Visualization Within the Stagnation Region of a Film-Cooled Turbine Vane

2002 ◽  
Vol 124 (2) ◽  
pp. 200-206 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Flow Visualization ◽  
Film Cooling ◽  
Laser Doppler Velocimetry ◽  
Thermal Field ◽  
Velocity Fields ◽  
Stagnation Region ◽  
Physical Mechanisms ◽  
Mainstream Flow ◽  
Turbine Vane ◽  
Adiabatic Effectiveness

To develop quality computational codes for the film cooling of a turbine vane, a detailed understanding is needed of the physical mechanisms of the mainstream-coolant interactions. In this study flow visualization, thermal profiles, and laser Doppler velocimetry measurements were used to define the thermal and velocity fields of the film cooled showerhead region of a turbine vane. The showerhead consisted of six rows of spanwise oriented coolant holes, and blowing ratios ranged from 0.5 to 2.0. Performances with low and high mainstream turbulence levels were tested. Coolant jets from the showerhead were completely separated from the surface even at relatively low blowing ratios. However, the interaction of the coolant jets from laterally adjacent holes created a barrier to the mainstream flow, resulting in relatively high adiabatic effectiveness.

Combustor Turbine Interface Studies: Part 2 — Flow and Thermal Field Measurements

2002 ◽  
Author(s):  
W. F. Colban ◽  
A. T. Lethander ◽  
K. A. Thole ◽  
G. Zess
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Film Cooling ◽  
Large Scale ◽  
Field Measurements ◽  
Pressure Profile ◽  
Stagnation Line ◽  
Turbine Engine ◽  
Turbine Vane ◽  
Cooling Methods

Most turbine inlet flows resulting from the combustor exit are non-uniform in the near-platform region as a result of cooling methods used for the combustor liner. These cooling methods include injection through film-cooling holes and injection through a slot that connects the combustor and turbine. This paper presents thermal and flow field measurements in the turbine vane passage for a combustor exit flow representative of what occurs in a gas turbine engine. The experiments were performed in a large-scale wind tunnel facility that incorporates combustor and turbine vane models. The measured results for the thermal and flow fields indicate a secondary flow pattern in the vane passage that can be explained by the total pressure profile exiting the combustor. This secondary flow field is quite different than that presented for past studies with an approaching flat plate turbulent boundary layer along the upstream platform. A counter-rotating vortex that is positioned above the passage vortex was identifed from the measurements. Highly turbulent and highly unsteady flow velocities occur at flow impingment locations along the stagnation line.

Combustor Turbine Interface Studies—Part 2: Flow and Thermal Field Measurements

2003 ◽  
Vol 125 (2) ◽  
pp. 203-209 ◽  
Author(s):  
W. F. Colban ◽  
A. T. Lethander ◽  
K. A. Thole ◽  
G. Zess
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Film Cooling ◽  
Large Scale ◽  
Field Measurements ◽  
Pressure Profile ◽  
Stagnation Line ◽  
Turbine Engine ◽  
Turbine Vane ◽  
Cooling Methods

Most turbine inlet flows resulting from the combustor exit are nonuniform in the near-platform region as a result of cooling methods used for the combustor liner. These cooling methods include injection through film-cooling holes and injection through a slot that connects the combustor and turbine. This paper presents thermal and flow field measurements in the turbine vane passage for a combustor exit flow representative of what occurs in a gas turbine engine. The experiments were performed in a large-scale wind tunnel facility that incorporates combustor and turbine vane models. The measured results for the thermal and flow fields indicate a secondary flow pattern in the vane passage that can be explained by the total pressure profile exiting the combustor. This secondary flow field is quite different than that presented for past studies with an approaching flat plate turbulent boundary layer along the upstream platform. A counter-rotating vortex that is positioned above the passage vortex was identified from the measurements. Highly turbulent and highly unsteady flow velocities occur at flow impingement locations along the stagnation line.

Thrombotic Thrombocytopenic Purpura: Mechanism for Effectiveness of Plasmapheresis

1979 ◽  
Author(s):  
J. G. Kelton ◽  
P. B. Neame ◽  
I. Walker ◽  
A. G. Turpie ◽  
J. McBride ◽  
...  
Keyword(s):  
Platelet Count ◽  
Thrombotic Thrombocytopenic Purpura ◽  
The Other ◽  
Unknown Etiology ◽  
Normal Range ◽  
Antiplatelet Antibody ◽  
Thrombocytopenic Purpura ◽  
Serious Illness ◽  
Normal Platelet ◽  
Very High

Thrombotic thrombocytopenic purpura (TTP) is a rare but serious illness of unknown etiology. Treatment by plasmapheresis has been reported to be effective but the mechanism for benefit is unknown. We have investigated the effect of plasmapheresis in 2 patients with TTP by quantitating platelet associated IgG (PAIgG) levels prior to and following plasmapheresis. Both patients had very high levels of PAIgG at presentation (90 and A8 fg IgG/platelet respectively, normal 0-5). in both, the PAIgG levels progressively fell to within the normal range and the platelet count rose following plasmapheresis. One patient remained in remission with normal platelet counts and PAIgG levels. The other relapsed after plasmapheresis and the PAIgG level rose prior to the fall in platelet count. Plasmapheresis was repeated and resulted in normalization of both the platelet count and PAIgG level. It is suggested that plasmapheresis removes antiplatelet antibody or immune complexes which may be of etiological importance in this illness.

Growth Characteristics of Activated Sludges Acclimated to para-Nitrophenol in Batch and Continuous Modes

1994 ◽  
Vol 29 (7) ◽  
pp. 327-333
Author(s):  
Y. Matsui ◽  
F. Yamaguchi ◽  
Y. Suwa ◽  
Y. Urushigawa
Keyword(s):  
Growth Characteristics ◽  
The Other ◽  
Operational Mode ◽  
Continuous Mode ◽  
Relative Resistance ◽  
Batch Mode ◽  
The Given ◽  
Operational Modes ◽  
Very High ◽  
Sensitive Group

Activated sludges were acclimated to p-nitrophenol (PNP) in two operational modes, a batch and a continuous. The operational mode of the PNP acclimation of activated sludges strongly affected the physiological characteristics of predominant microorganisms responsible for PNP degradation. Predominant PNP degraders in the sludge in batch mode (Sludge B) had lower PNP affinity and were relatively insensitive to PNP concentration. Those of the sludge in continuous mode (Sludge C), on the other hand, had very high PNP affinity and were sensitive to PNP. MPN enumeration of PNP degraders in sludge B and C using media with different PNP concentrations (0.05, 0.2,0.5 and 2.0 mM) supported the above results. Medium with 0.2 mM of PNP did not recover PNP degraders in sludge C well, while it recovered PNP degraders in sludge B as well as the medium with 0.05 mM did. When switching from one operational mode to the other, the predominant population in sludge B shifted to the sensitive group, but that of sludge C did not shift at the given loading of PNP, showing relative resistance to inhibitive concentration.

Islamic hedging for pilgrimage funds: case of Indonesia

2019 ◽  
Vol 11 (3) ◽  
pp. 328-341
Author(s):  
Rifki Ismal ◽  
Nurul Izzati Septiana
Keyword(s):  
Exchange Rate ◽  
The Other ◽  
Exchange Rate Risk ◽  
Content Type ◽  
Other Hand ◽  
Rate Risk ◽  
Risk Identify ◽  
Hajj Season ◽  
The Right ◽  
Very High

Purpose The demand for Saudi Arabian real (SAR) is very high in the pilgrimage (hajj) season while the authority, unfortunately, does not hedge the hajj funds. As such, the hajj funds are potentially exposed to exchange rate risk, which can impact the value of hajj funds and generate extra cost to the pilgrims. The purpose of this paper is to conduct simulations of Islamic hedging for pilgrimage funds to: mitigate and minimize exchange rate risk, identify and recommend the ideal time, amount and tenors of Islamic hedging for hajj funds, estimate cost saving by pursuing Islamic hedging and propose technical and general recommendations for the authority. Design/methodology/approach Forward transaction mechanism is adopted to compute Islamic forward between SAR and Rupiah (Indonesian currency) or IDR. Findings – based on simulations, the paper finds that: the longer the Islamic hedging tenors, the better is the result of Islamic hedging, the decreasing of IDR/USD is the right time to hedge the hajj funds and, on the other hand, the IDR/SAR appreciation is not the right time to hedge the hajj funds. Findings Based on simulations, the paper finds that: the longer the Islamic hedging tenors, the better is the result of Islamic hedging, the decreasing of IDR/USD is the right time to hedge the hajj funds and, on the other hand, the IDR/SAR appreciation is not the right time to hedge the hajj funds. Research limitations/implications The research suggests the authority to (and not to) hedge the hajj fund, depending on economic conditions and market indicators. Even though the assessment is for the Indonesian case, other countries maintaining hajj funds might also learn from this paper. Originality/value To the best of author’s knowledge, this is the first paper in Indonesia that attempts to simulate the optimal hedging of hajj funds.

Rolling and Recrystallization Textures in High Purity Al Cold Rolled to Very High Rolling Reductions

2005 ◽  
Vol 495-497 ◽  
pp. 603-608 ◽  
Author(s):  
Atsushi Todayama ◽  
Hirosuke Inagaki
Keyword(s):  
Cold Rolling ◽  
High Purity ◽  
Work Hardening ◽  
Dynamic Recovery ◽  
The Other ◽  
Rolling Reduction ◽  
Theoretical Investigations ◽  
Theoretical Predictions ◽  
Cold Rolled ◽  
Very High

On the basis of Taylor-Bishop-Hill’s theory, many previous theoretical investigations have predicted that, at high rolling reductions, most of orientations should rotate along theβfiber from {110}<112> to {123}<634> and finally into the {112}<111> stable end orientations. Although some exceptions exist, experimental observations have shown, on the other hand, that the maximum on the β fiber is located still at about {123}<634> even after 97 % cold rolling. In the present paper, high purity Al containing 50 ppm Cu was cold rolled up to 99.4 % reduction in thickness and examined whether {112}<111> stable end orientation could be achieved experimentally. It was found that, with increasing rolling reduction above 98 %, {110}<112> decreased, while orientations in the range between {123}<634> and {112}<111> increased, suggesting that crystal rotation along the βfiber from {110}<112> toward {123}<634> and {112}<111> in fact took place. At higher rolling reductions, however, further rotation of this peak toward {112}<111> was extremely sluggish, and even at the highest rolling reduction, it could not arrive at {112}<111>. Such discrepancies between theoretical predictions and experimental observations should be ascribed to the development of dislocation substructures, which were formed by concurrent work hardening and dynamic recovery. Since such development of dislocation substructures are not taken into account in Taylor-Bishop-Hill’s theory, it seems that they can not correctly predict the development of rolling textures at very high rolling reductions, i. e. stable end orientations. On annealing specimens rolled above 98 % reduction in thickness, cube textures were very weak, suggesting that cube bands were almost completely rotated into other orientations during cold rolling. {325}<496>, which lay at an intermediate position between {123}<634> and {112}<111> along theβfiber, developed strongly in the recrystallization textures.

Sign in / Sign up

Export Citation Format

Share Document