The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Neil William Harvey - One of the best experts on this subject based on the ideXlab platform.
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Pressure Surface Separations in Low-Pressure Turbines—Part 1: Midspan Behavior
Journal of Turbomachinery, 2002Co-Authors: Michael J. Brear, Howard P. Hodson, Neil William HarveyAbstract:This paper describes an investigation into the behaviour of the Pressure Surface separation at midspan in a linear cascade. It is f ound that the Pressure Surface separation can be a significant contributor to the profile loss of a thin, solid, low Pressure turbine blade that is typical of current engine designs. Numerical predictions are first used to study the inviscid behaviour of the blade. These show a strong incidence dependence around the leading edge of the profile. Experiments then show clearly that all characteristics of the Pressure Surface separation are controlled primarily by the incidence. It is also shown that the effects of wake passing, freestream turbulence and Reynolds number are of secondary importance. A simple two-part model of the Pressure Surface flow is then proposed. This model suggests that the Pressure surf ace separation is highly dissipative through the action of its strong turbulent shear. As the incidence is reduced, the increasing blockage of the Pressure Surface separation then raises the velocity in the separated shear layer to levels at which the separation can create significant loss. NOMENCLATURE Cd dissipation coefficient
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Pressure Surface Separations in Low-Pressure Turbines—Part 2: Interactions With the Secondary Flow
Journal of Turbomachinery, 2002Co-Authors: Michael J. Brear, Howard P. Hodson, P. González, Neil William HarveyAbstract:This paper describes a study of the interaction between the Pressure Surface separation and the sec ondary flow on low Pressure turbine blades. It is found that this interaction can sign ificantly affect the strength of the secondary flow and the loss that it creates. Experimental and numerical techniques are used to study the secondary flow in a family of four low Pressure turbine blades in linear cascade. These blades are typical of current designs, share the same suction Surface and pitch, but have differing Pressure Surfaces. A mechanism for the interaction between the Pressure Surface separation and the secondary flow is proposed and is used to explain the variations in the secondary flows of the four blades. This mechanism is based on simple dynamical secondary flow concepts and is similar to the aft-loading argument commonly used in modern turbine design. NOMENCLATURE Cd dissipation coefficient CX axial chord (m) () X P L C
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Pressure Surface Separations in Low Pressure Turbines: Part 1 of 2 — Midspan Behaviour
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001Co-Authors: Michael J. Brear, Howard P. Hodson, Neil William HarveyAbstract:This paper describes an investigation into the behaviour of the Pressure Surface separation at midspan in a linear cascade. It is found that the Pressure Surface separation can be a significant contributor to the profile loss of a thin, solid, low Pressure turbine blade that is typical of current engine designs.Numerical predictions are first used to study the inviscid behaviour of the blade. These show a strong incidence dependence around the leading edge of the profile. Experiments then show clearly that all characteristics of the Pressure Surface separation are controlled primarily by the incidence. It is also shown that the effects of wake passing, freestream turbulence and Reynolds number are of secondary importance.A simple two-part model of the Pressure Surface flow is then proposed. This model suggests that the Pressure Surface separation is highly dissipative through the action of its strong turbulent shear. As the incidence is reduced, the increasing blockage of the Pressure Surface separation then raises the velocity in the separated shear layer to levels at which the separation can create significant loss.Copyright © 2001 by ASME
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Pressure Surface Separations in Low Pressure Turbines: Part 2 of 2 — Interactions With the Secondary Flow
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001Co-Authors: Michael J. Brear, Howard P. Hodson, P. González, Neil William HarveyAbstract:This paper describes a study of the interaction between the Pressure Surface separation and the secondary flow on low Pressure turbine blades. It is found that this interaction can significantly affect the strength of the secondary flow and the loss that it creates. Experimental and numerical techniques are used to study the secondary flow in a family of four low Pressure turbine blades in linear cascade. These blades are typical of current designs, share the same suction Surface and pitch, but have differing Pressure Surfaces.A mechanism for the interaction between the Pressure Surface separation and the secondary flow is proposed and is used to explain the variations in the secondary flows of the four blades. This mechanism is based on simple dynamical secondary flow concepts and is similar to the aft-loading argument commonly used in modern turbine design.Copyright © 2001 by ASME
Howard P. Hodson - One of the best experts on this subject based on the ideXlab platform.
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Pressure Surface Separations in Low-Pressure Turbines—Part 1: Midspan Behavior
Journal of Turbomachinery, 2002Co-Authors: Michael J. Brear, Howard P. Hodson, Neil William HarveyAbstract:This paper describes an investigation into the behaviour of the Pressure Surface separation at midspan in a linear cascade. It is f ound that the Pressure Surface separation can be a significant contributor to the profile loss of a thin, solid, low Pressure turbine blade that is typical of current engine designs. Numerical predictions are first used to study the inviscid behaviour of the blade. These show a strong incidence dependence around the leading edge of the profile. Experiments then show clearly that all characteristics of the Pressure Surface separation are controlled primarily by the incidence. It is also shown that the effects of wake passing, freestream turbulence and Reynolds number are of secondary importance. A simple two-part model of the Pressure Surface flow is then proposed. This model suggests that the Pressure surf ace separation is highly dissipative through the action of its strong turbulent shear. As the incidence is reduced, the increasing blockage of the Pressure Surface separation then raises the velocity in the separated shear layer to levels at which the separation can create significant loss. NOMENCLATURE Cd dissipation coefficient
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Pressure Surface Separations in Low-Pressure Turbines—Part 2: Interactions With the Secondary Flow
Journal of Turbomachinery, 2002Co-Authors: Michael J. Brear, Howard P. Hodson, P. González, Neil William HarveyAbstract:This paper describes a study of the interaction between the Pressure Surface separation and the sec ondary flow on low Pressure turbine blades. It is found that this interaction can sign ificantly affect the strength of the secondary flow and the loss that it creates. Experimental and numerical techniques are used to study the secondary flow in a family of four low Pressure turbine blades in linear cascade. These blades are typical of current designs, share the same suction Surface and pitch, but have differing Pressure Surfaces. A mechanism for the interaction between the Pressure Surface separation and the secondary flow is proposed and is used to explain the variations in the secondary flows of the four blades. This mechanism is based on simple dynamical secondary flow concepts and is similar to the aft-loading argument commonly used in modern turbine design. NOMENCLATURE Cd dissipation coefficient CX axial chord (m) () X P L C
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Pressure and Suction Surfaces Redesign for High-Lift Low-Pressure Turbines
Journal of Turbomachinery, 2002Co-Authors: P. González, I. Ulizar, R. Vázquez, Howard P. HodsonAbstract:Nowadays there is a big effort toward improving the low-Pressure turbine efficiency even to the extent of penalizing other relevant design parameters. LP turbine efficiency influences SFC more than other modules in the engine. Most of the research has been oriented to reduce profile losses, modifying the suction Surface, the Pressure Surface, or the three-dimensional regions of the flow. To date, the Pressure Surface has received very little attention. The dependence of the profile losses on the behavior of both Pressure and suction Surfaces has been investigated for the case of a high-lift design that is representative of a modern civil engine LP turbine. The experimental work described in this paper consists of two different sets of experiments: the first one concluded an improved Pressure Surface definition, and the second set was oriented to achieve further improvement in losses modifying the profile suction Surface. Three profiles were designed and tested over a range of conditions. The first profile is a thin-solid design. This profile has a large Pressure side separation bubble extending from near the leading edge to midchord. The second profile is a hollow design with the same suction Surface as the first one, but avoiding Pressure Surface separation. The third one is also a hollow design with the same Pressure Surface as the second profile, but more aft loaded suction Surface. The study is part of a wider ongoing research program covering the effects of the different design parameters on losses. The paper describes the experiments conducted in a low-speed linear cascade facility. It gathers together steady and unsteady loss measurements by wake traverse and Surface Pressure distributions for all the profiles. It is shown that thick profiles generate only around 90 percent of the losses of a thin-solid profile with the same suction Surface. The results support the idea of an optimum axial position for the peak Mach number. Caution is recommended, as profile aft loading would not be a completely secure method for reducing losses.
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Pressure and Suction Surfaces Redesign for High Lift Low Pressure Turbines
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001Co-Authors: P. González, I. Ulizar, R. Vázquez, Howard P. HodsonAbstract:Nowadays there is a big effort toward improving the low Pressure turbine efficiency even to the extent of penalising other relevant design parameters. LP turbine efficiency influences SFC more than other modules in the engine. Most of the research has been oriented to reduce profile losses, modifying the suction Surface, the Pressure Surface or the three-dimensional regions of the flow. To date, the Pressure Surface has received very little attention. The dependence of the profile losses on the behaviour of both Pressure and suction Surfaces has been investigated for the case of a high lift design that is representative of a modern civil engine LP turbine. The experimental work described in this paper consists on two different sets of experiments: the first one concluded an improved Pressure Surface definition and the second set was oriented to achieve further improvement in losses modifying the profile suction Surface. Three profiles were designed and tested over a range of conditions. The first profile is a thin-solid design. This profile has a large Pressure side separation bubble extending from near the leading edge to mid-chord. The second profile is a hollow design with the same suction Surface as the first one but avoiding Pressure Surface separation. The third one is also a hollow design with the same Pressure Surface as the second profile but more aft loaded suction Surface. The study is part of a wider on-going research programme covering the effects of the different design parameters on losses. The paper describes the experiments conducted in a lowspeed linear cascade facility. It gathers together steady and unsteady loss measurements by wake traverse and Surface Pressure distributions for all the profiles. It is shown that thick profiles generates only around 90% of the losses of a thinsolid profile with the same suction Surface. The results support the idea of an optimum position axial position for the peak Mach number. Caution is recommended as profile aft loading would not be a completely secure method for reducing losses. NOMENCLATURE α1 Inlet flow angle. α2 Outlet flow angle. Cax Axial chord. I Incidence.
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Pressure Surface Separations in Low Pressure Turbines: Part 1 of 2 — Midspan Behaviour
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001Co-Authors: Michael J. Brear, Howard P. Hodson, Neil William HarveyAbstract:This paper describes an investigation into the behaviour of the Pressure Surface separation at midspan in a linear cascade. It is found that the Pressure Surface separation can be a significant contributor to the profile loss of a thin, solid, low Pressure turbine blade that is typical of current engine designs.Numerical predictions are first used to study the inviscid behaviour of the blade. These show a strong incidence dependence around the leading edge of the profile. Experiments then show clearly that all characteristics of the Pressure Surface separation are controlled primarily by the incidence. It is also shown that the effects of wake passing, freestream turbulence and Reynolds number are of secondary importance.A simple two-part model of the Pressure Surface flow is then proposed. This model suggests that the Pressure Surface separation is highly dissipative through the action of its strong turbulent shear. As the incidence is reduced, the increasing blockage of the Pressure Surface separation then raises the velocity in the separated shear layer to levels at which the separation can create significant loss.Copyright © 2001 by ASME
John K. Eaton - One of the best experts on this subject based on the ideXlab platform.
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Heat Transfer Coefficient Measurements on the Film-Cooled Pressure Surface of a Transonic Airfoil
Journal of Turbomachinery, 2013Co-Authors: Paul M. Kodzwa, John K. EatonAbstract:This paper presents isoenergetic temperature and steady-state film-cooled heat transfer coefficient measurements on the Pressure Surface of a modern, highly cambered transonic airfoil. A single passage model simulated the idealized two-dimensional flow path between blades in a modern transonic turbine. This set up offered a simpler construction than a linear cascade but produced an equivalent flow condition. Furthermore, this model allowed the use of steady-state, constant Surface heat fluxes. We used wide-band thermochromic liquid crystals (TLCs) viewed through a novel miniature periscope system to perform high-accuracy (±0.2 °C) thermography. The peak Mach number along the Pressure Surface was 1.5, and maximum turbulence intensity was 30%. We used air and carbon dioxide as injectant to simulate the density ratios characteristic of the film cooling problem. We found significant differences between isoenergetic and recovery temperature distributions with a strongly accelerated mainstream and detached coolant jets. Our heat transfer data showed some general similarities with lower-speed data immediately downstream of injection; however, we also observed significant heat transfer attenuation far downstream at high blowing conditions. Our measurements suggested that the momentum ratio was the most appropriate variable to parameterize the effect of injectant density once jet lift-off occurred. We noted several nonintuitive results in our turbulence effect studies. First, we found that increased mainstream turbulence can be overwhelmed by the local augmentation of coolant injection. Second, we observed complex interactions between turbulence level, coolant density, and blowing rate with an accelerating mainstream.
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Heat transfer coefficient measurements on the Pressure Surface of a transonic airfoil
Experiments in Fluids, 2010Co-Authors: Paul M. Kodzwa, John K. EatonAbstract:This paper presents steady-state recovery temperature and heat transfer coefficient measurements on the Pressure Surface of a modern, highly cambered transonic airfoil. These measurements were collected with a peak Mach number of 1.5 and a maximum turbulence intensity of 30%. We used a single passage model to simulate the idealized two-dimensional flow path between rotor blades in a modern transonic turbine. This set up offered a simpler construction than a linear cascade, yet produced an equivalent flow condition. We performed validated high accuracy (±0.2°C) Surface temperature measurements using wide-band thermochromic liquid crystals allowing separate measurements of the previously listed parameters with the same heat transfer Surface. We achieved maximum heat transfer coefficient uncertainties that were equivalent to similar investigations (±10%). Two key observations are the heat transfer coefficient along the aft portion of the airfoil is sensitive to the Surface heat flux and is highly insensitive to the level of freestream turbulence. Possible explanations for these observations are discussed.
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Film Effectiveness Measurements on the Pressure Surface of a Transonic Airfoil
Journal of Propulsion and Power, 2010Co-Authors: Paul M. Kodzwa, John K. EatonAbstract:This paper presents steady-state film effectiveness measurements for two rows of compound-angle round holes on the Pressure Surface of a modern, highly cambered, transonic airfoil. A single-passage model was used to simulate the idealized two-dimensional flowpath between rotor blades in a modern transonic turbine. This setup offered a simpler construction than a linear cascade, yet produced an equivalent flow condition. Validated high-accuracy (±0.2°C) Surface-temperature measurements were performed using wideband thermochromic liquid crystals, allowing direct measurement of the adiabatic cooled-wall temperature. The peak Mach number along the Pressure Surface was 1.5 and maximum turbulence intensity was 30%. To simulate the effect of temperature gradients on coolant behavior, carbon dioxide and air were used as the injectant. The data indicate that jet blowoff appears to occur at blowing rates that are significantly higher than previously observed. Furthermore, the data suggest that increasing injectant density only improves effectiveness when the coolant jets are attached to the Surface. It was observed that at high turbulence levels, the attached coolant jets degrade faster and jet blowoff is suppressed as blowing rates are increased.
Michael J. Brear - One of the best experts on this subject based on the ideXlab platform.
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Pressure Surface Separations in Low-Pressure Turbines—Part 1: Midspan Behavior
Journal of Turbomachinery, 2002Co-Authors: Michael J. Brear, Howard P. Hodson, Neil William HarveyAbstract:This paper describes an investigation into the behaviour of the Pressure Surface separation at midspan in a linear cascade. It is f ound that the Pressure Surface separation can be a significant contributor to the profile loss of a thin, solid, low Pressure turbine blade that is typical of current engine designs. Numerical predictions are first used to study the inviscid behaviour of the blade. These show a strong incidence dependence around the leading edge of the profile. Experiments then show clearly that all characteristics of the Pressure Surface separation are controlled primarily by the incidence. It is also shown that the effects of wake passing, freestream turbulence and Reynolds number are of secondary importance. A simple two-part model of the Pressure Surface flow is then proposed. This model suggests that the Pressure surf ace separation is highly dissipative through the action of its strong turbulent shear. As the incidence is reduced, the increasing blockage of the Pressure Surface separation then raises the velocity in the separated shear layer to levels at which the separation can create significant loss. NOMENCLATURE Cd dissipation coefficient
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Pressure Surface Separations in Low-Pressure Turbines—Part 2: Interactions With the Secondary Flow
Journal of Turbomachinery, 2002Co-Authors: Michael J. Brear, Howard P. Hodson, P. González, Neil William HarveyAbstract:This paper describes a study of the interaction between the Pressure Surface separation and the sec ondary flow on low Pressure turbine blades. It is found that this interaction can sign ificantly affect the strength of the secondary flow and the loss that it creates. Experimental and numerical techniques are used to study the secondary flow in a family of four low Pressure turbine blades in linear cascade. These blades are typical of current designs, share the same suction Surface and pitch, but have differing Pressure Surfaces. A mechanism for the interaction between the Pressure Surface separation and the secondary flow is proposed and is used to explain the variations in the secondary flows of the four blades. This mechanism is based on simple dynamical secondary flow concepts and is similar to the aft-loading argument commonly used in modern turbine design. NOMENCLATURE Cd dissipation coefficient CX axial chord (m) () X P L C
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Pressure Surface Separations in Low Pressure Turbines: Part 1 of 2 — Midspan Behaviour
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001Co-Authors: Michael J. Brear, Howard P. Hodson, Neil William HarveyAbstract:This paper describes an investigation into the behaviour of the Pressure Surface separation at midspan in a linear cascade. It is found that the Pressure Surface separation can be a significant contributor to the profile loss of a thin, solid, low Pressure turbine blade that is typical of current engine designs.Numerical predictions are first used to study the inviscid behaviour of the blade. These show a strong incidence dependence around the leading edge of the profile. Experiments then show clearly that all characteristics of the Pressure Surface separation are controlled primarily by the incidence. It is also shown that the effects of wake passing, freestream turbulence and Reynolds number are of secondary importance.A simple two-part model of the Pressure Surface flow is then proposed. This model suggests that the Pressure Surface separation is highly dissipative through the action of its strong turbulent shear. As the incidence is reduced, the increasing blockage of the Pressure Surface separation then raises the velocity in the separated shear layer to levels at which the separation can create significant loss.Copyright © 2001 by ASME
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Pressure Surface Separations in Low Pressure Turbines: Part 2 of 2 — Interactions With the Secondary Flow
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001Co-Authors: Michael J. Brear, Howard P. Hodson, P. González, Neil William HarveyAbstract:This paper describes a study of the interaction between the Pressure Surface separation and the secondary flow on low Pressure turbine blades. It is found that this interaction can significantly affect the strength of the secondary flow and the loss that it creates. Experimental and numerical techniques are used to study the secondary flow in a family of four low Pressure turbine blades in linear cascade. These blades are typical of current designs, share the same suction Surface and pitch, but have differing Pressure Surfaces.A mechanism for the interaction between the Pressure Surface separation and the secondary flow is proposed and is used to explain the variations in the secondary flows of the four blades. This mechanism is based on simple dynamical secondary flow concepts and is similar to the aft-loading argument commonly used in modern turbine design.Copyright © 2001 by ASME
Paul M. Kodzwa - One of the best experts on this subject based on the ideXlab platform.
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Heat Transfer Coefficient Measurements on the Film-Cooled Pressure Surface of a Transonic Airfoil
Journal of Turbomachinery, 2013Co-Authors: Paul M. Kodzwa, John K. EatonAbstract:This paper presents isoenergetic temperature and steady-state film-cooled heat transfer coefficient measurements on the Pressure Surface of a modern, highly cambered transonic airfoil. A single passage model simulated the idealized two-dimensional flow path between blades in a modern transonic turbine. This set up offered a simpler construction than a linear cascade but produced an equivalent flow condition. Furthermore, this model allowed the use of steady-state, constant Surface heat fluxes. We used wide-band thermochromic liquid crystals (TLCs) viewed through a novel miniature periscope system to perform high-accuracy (±0.2 °C) thermography. The peak Mach number along the Pressure Surface was 1.5, and maximum turbulence intensity was 30%. We used air and carbon dioxide as injectant to simulate the density ratios characteristic of the film cooling problem. We found significant differences between isoenergetic and recovery temperature distributions with a strongly accelerated mainstream and detached coolant jets. Our heat transfer data showed some general similarities with lower-speed data immediately downstream of injection; however, we also observed significant heat transfer attenuation far downstream at high blowing conditions. Our measurements suggested that the momentum ratio was the most appropriate variable to parameterize the effect of injectant density once jet lift-off occurred. We noted several nonintuitive results in our turbulence effect studies. First, we found that increased mainstream turbulence can be overwhelmed by the local augmentation of coolant injection. Second, we observed complex interactions between turbulence level, coolant density, and blowing rate with an accelerating mainstream.
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Heat transfer coefficient measurements on the Pressure Surface of a transonic airfoil
Experiments in Fluids, 2010Co-Authors: Paul M. Kodzwa, John K. EatonAbstract:This paper presents steady-state recovery temperature and heat transfer coefficient measurements on the Pressure Surface of a modern, highly cambered transonic airfoil. These measurements were collected with a peak Mach number of 1.5 and a maximum turbulence intensity of 30%. We used a single passage model to simulate the idealized two-dimensional flow path between rotor blades in a modern transonic turbine. This set up offered a simpler construction than a linear cascade, yet produced an equivalent flow condition. We performed validated high accuracy (±0.2°C) Surface temperature measurements using wide-band thermochromic liquid crystals allowing separate measurements of the previously listed parameters with the same heat transfer Surface. We achieved maximum heat transfer coefficient uncertainties that were equivalent to similar investigations (±10%). Two key observations are the heat transfer coefficient along the aft portion of the airfoil is sensitive to the Surface heat flux and is highly insensitive to the level of freestream turbulence. Possible explanations for these observations are discussed.
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Film Effectiveness Measurements on the Pressure Surface of a Transonic Airfoil
Journal of Propulsion and Power, 2010Co-Authors: Paul M. Kodzwa, John K. EatonAbstract:This paper presents steady-state film effectiveness measurements for two rows of compound-angle round holes on the Pressure Surface of a modern, highly cambered, transonic airfoil. A single-passage model was used to simulate the idealized two-dimensional flowpath between rotor blades in a modern transonic turbine. This setup offered a simpler construction than a linear cascade, yet produced an equivalent flow condition. Validated high-accuracy (±0.2°C) Surface-temperature measurements were performed using wideband thermochromic liquid crystals, allowing direct measurement of the adiabatic cooled-wall temperature. The peak Mach number along the Pressure Surface was 1.5 and maximum turbulence intensity was 30%. To simulate the effect of temperature gradients on coolant behavior, carbon dioxide and air were used as the injectant. The data indicate that jet blowoff appears to occur at blowing rates that are significantly higher than previously observed. Furthermore, the data suggest that increasing injectant density only improves effectiveness when the coolant jets are attached to the Surface. It was observed that at high turbulence levels, the attached coolant jets degrade faster and jet blowoff is suppressed as blowing rates are increased.