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Konrad Vogeler - One of the best experts on this subject based on the ideXlab platform.

  • periodical unsteady flow within a rotor Blade Row of an axial compressor part ii wake tip clearance vortex interaction
    Journal of Turbomachinery-transactions of The Asme, 2008
    Co-Authors: Ronald Mailach, Ingolf Lehmann, Konrad Vogeler
    Abstract:

    In this two-part paper, results of the periodical unsteady flow field within the third rotor Blade Row of the four-stage Dresden low-speed research compressor are presented. The main part of the experimental investigations was performed using laser Doppler anemometry. Results of the flow field at several spanwise positions between midspan and rotor Blade tip will be discussed. In addition, time-resolving pressure sensors at midspan of the rotor Blades provide information about the unsteady profile pressure distribution. In Part II of the paper, the flow field in the rotor Blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the rotor Blade tip clearance vortices. Consequently, in the rotor frame of reference, the tip clearance vortices are periodical with the stator Blade passing frequency. Due to the wakes, the tip clearance vortices are separated into different segments. Along the mean vortex trajectory, these parts can be characterized by alternating patches of higher and lower velocities and flow turning or subsequent counter-rotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence, the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time.

  • steady and unsteady flow field in a multistage low speed axial compressor a test case
    ASME Turbo Expo 2008: Power for Land Sea and Air, 2008
    Co-Authors: Mario Kunzelmann, Ronald Mailach, Ralf Muller, Konrad Vogeler
    Abstract:

    This paper introduces a new test case for compressor aerodynamics. The dataset is provided for the Dresden four-stage Low-Speed Research Compressor (LSRC), which was put into operation in 1995. The compressor consists of four identical stages, which are preceded by an inlet guide vane. The data set will be provided for the reference blading of the compressor with cantilevered stator vanes. This blading was developed on the basis of the profiles of a middle stage of a high-pressure compressor of a jet engine. This paper makes available the blading geometry as well as a variety of flow field measurement results. This includes the compressor map, selected pressure distributions and other results of flow field measurements with conventional techniques (e.g. Pitot probes, 5-hole probes). Furthermore different aspects of Blade Row interactions were addressed in this compressor within recent years. The periodical unsteady flow field within a selected rotor Blade Row was investigated using Laser-Doppler-Anemometry. Further results on the unsteady profile pressures and profile boundary layers will be provided. Supplementary, numerical results will be compared to the experiments. Results are available for several stages of the compressor and different operating points. With this test case a unique database for the aerodynamics in a multistage axial compressor will be provided that can be used for the validation of numerical codes.Copyright © 2008 by ASME

  • rotor stator interactions in a four stage low speed axial compressor part ii unsteady aerodynamic forces of rotor and stator Blades
    Journal of Turbomachinery-transactions of The Asme, 2004
    Co-Authors: Ronald Mailach, Lutz Muller, Konrad Vogeler
    Abstract:

    This two-part paper presents detailed experimental investigations of unsteady aerodynamic Blade Row interactions in the four-stage low-speed research compressor of Dresden. In Part I of the paper the unsteady profile pressure distributions for the nominal setup of the compressor are discussed. Furthermore the effect of Blade Row clocking on the unsteady profile pressures is investigated. Part II deals with the unsteady aerodynamic Blade forces, which are determined from the measured profile pressure distributions. A method to calculate the aerodynamic Blade forces on the basis of the experimental data is presented. The resulting aerodynamic Blade forces are discussed for the rotor and stator Blade Rows of the first stage and the third stage of the compressor. Different operating points between design point and stability limit of the compressor were chosen to investigate the influence of loading on the aerodynamic force excitation. The time traces and the frequency contents of the unsteady aerodynamic Blade force are discussed. Strong periodic influences of the incoming wakes and of potential effects of downstream Blade Rows can be observed. The amplitude and shape of the unsteady aerodynamic Blade force depend on the interaction of the superimposed influences of the Blade Rows.

  • aerodynamic Blade Row interactions in an axial compressor part i unsteady boundary layer development
    Journal of Turbomachinery-transactions of The Asme, 2004
    Co-Authors: Ronald Mailach, Konrad Vogeler
    Abstract:

    This two-part paper presents experimental investigations of unsteady aerodynamic Blade Row interactions in the first stage of the four-stage low-speed research compressor of Dresden. Both the unsteady boundary layer development and the unsteady pressure distribution of the stator Blades are investigated for several operating points. The measurements were carried out on pressure side and suction side at midspan. In Part I of the paper the investigations of the unsteady boundary layer behavior are presented. The experiments were carried out using surface-mounted hot-film sensors. Additional information on the time-resolved flow between the Blade Rows were obtained with a hot-wire probe. The unsteady boundary layer development is strongly influenced by the incoming wakes. Within the predominantly laminar boundary layer in the front part of the Blade a clear response of the boundary layer to the velocity and turbulence structure of the incoming wakes can be observed. The time-resolved structure of the boundary layer for several operating points of the compressor is analyzed in detail. The topic calmed regions, which can be coupled to the wake passing, is discussed. As a result an improved description of the complex boundary layer structure is given.

  • aerodynamic Blade Row interactions in an axial compressor part ii unsteady profile pressure distribution and Blade forces
    Journal of Turbomachinery-transactions of The Asme, 2004
    Co-Authors: Ronald Mailach, Konrad Vogeler
    Abstract:

    This two-part paper presents experimental investigations of unsteady aerodynamic Blade Row interactions in the first stage of the four-stage low-speed research compressor of Dresden. Both the unsteady boundary layer development and the unsteady pressure distribution of the stator Blades are investigated for several operating points. The measurements were carried out on pressure side and suction side at midspan. In Part II of the paper the investigations of the unsteady pressure distribution on the stator Blades are presented. The experiments were carried out using piezoresistive miniature pressure sensors, which are embedded into the pressure and suction side surface of a single Blade. The unsteady pressure distribution on the Blade is analyzed for the design point and an operating point near the stability limit. The investigations show that it is strongly influenced by both the incoming wakes and the potential flow field of the downstream rotor Blade Row. If a disturbance arrives the leading edge or the trailing edge of the Blade the pressure changes nearly simultaneously along the Blade chord. Thus the unsteady profile pressure distribution is independent of the wake propagation within the Blade passage. A phase shift of the reaction on pressure and suction side is observed. The unsteady response of the boundary layer and the profile pressure distribution is compared. Based on the unsteady pressure distribution the unsteady pressure forces of the Blades are calculated and discussed.

Ronald Mailach - One of the best experts on this subject based on the ideXlab platform.

  • PS Pressure side
    2015
    Co-Authors: Dirk Witteck, Ronald Mailach, Derek Micallef, S Stator
    Abstract:

    Usually, in a turbine an uneven number of Blades are se-lected for vane and Blade Rows to reduce the level of interaction forces. To consider all unsteady flow phenomena within a turbine the computation of the full annulus is required causing consid-erable computational cost. Transient Blade Row methods using few passages reduce the numerical effort significantly. Neverthe-less, those approaches provide accurate results. This contribu-tion presents three different unsteady approaches to compare the accuracy and the computational effort, using a full annulus un-steady CFD simulation as a reference. The first approach mod-ifies the Blade-to-Blade ratio whereas the second method scales the circumferential flow pattern to reach spatial and temporal periodicity. Third approach is based on time-inclining method to overcome unequal Blade pitches with less numerical effort. All unsteady CFD simulations are carried out for the transonic test turbine VKI BRITE EURAM using the commercial CFD solver ANSYS CFX 14.5. The resulting unsteady pressure disturbances and Blade forces of the different transient Blade Row methods are compared to each other as well as to experimental data. Finally, the accuracy and the computational costs are discussed in more detail

  • periodical unsteady flow within a rotor Blade Row of an axial compressor part ii wake tip clearance vortex interaction
    Journal of Turbomachinery-transactions of The Asme, 2008
    Co-Authors: Ronald Mailach, Ingolf Lehmann, Konrad Vogeler
    Abstract:

    In this two-part paper, results of the periodical unsteady flow field within the third rotor Blade Row of the four-stage Dresden low-speed research compressor are presented. The main part of the experimental investigations was performed using laser Doppler anemometry. Results of the flow field at several spanwise positions between midspan and rotor Blade tip will be discussed. In addition, time-resolving pressure sensors at midspan of the rotor Blades provide information about the unsteady profile pressure distribution. In Part II of the paper, the flow field in the rotor Blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the rotor Blade tip clearance vortices. Consequently, in the rotor frame of reference, the tip clearance vortices are periodical with the stator Blade passing frequency. Due to the wakes, the tip clearance vortices are separated into different segments. Along the mean vortex trajectory, these parts can be characterized by alternating patches of higher and lower velocities and flow turning or subsequent counter-rotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence, the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time.

  • steady and unsteady flow field in a multistage low speed axial compressor a test case
    ASME Turbo Expo 2008: Power for Land Sea and Air, 2008
    Co-Authors: Mario Kunzelmann, Ronald Mailach, Ralf Muller, Konrad Vogeler
    Abstract:

    This paper introduces a new test case for compressor aerodynamics. The dataset is provided for the Dresden four-stage Low-Speed Research Compressor (LSRC), which was put into operation in 1995. The compressor consists of four identical stages, which are preceded by an inlet guide vane. The data set will be provided for the reference blading of the compressor with cantilevered stator vanes. This blading was developed on the basis of the profiles of a middle stage of a high-pressure compressor of a jet engine. This paper makes available the blading geometry as well as a variety of flow field measurement results. This includes the compressor map, selected pressure distributions and other results of flow field measurements with conventional techniques (e.g. Pitot probes, 5-hole probes). Furthermore different aspects of Blade Row interactions were addressed in this compressor within recent years. The periodical unsteady flow field within a selected rotor Blade Row was investigated using Laser-Doppler-Anemometry. Further results on the unsteady profile pressures and profile boundary layers will be provided. Supplementary, numerical results will be compared to the experiments. Results are available for several stages of the compressor and different operating points. With this test case a unique database for the aerodynamics in a multistage axial compressor will be provided that can be used for the validation of numerical codes.Copyright © 2008 by ASME

  • rotor stator interactions in a four stage low speed axial compressor part ii unsteady aerodynamic forces of rotor and stator Blades
    Journal of Turbomachinery-transactions of The Asme, 2004
    Co-Authors: Ronald Mailach, Lutz Muller, Konrad Vogeler
    Abstract:

    This two-part paper presents detailed experimental investigations of unsteady aerodynamic Blade Row interactions in the four-stage low-speed research compressor of Dresden. In Part I of the paper the unsteady profile pressure distributions for the nominal setup of the compressor are discussed. Furthermore the effect of Blade Row clocking on the unsteady profile pressures is investigated. Part II deals with the unsteady aerodynamic Blade forces, which are determined from the measured profile pressure distributions. A method to calculate the aerodynamic Blade forces on the basis of the experimental data is presented. The resulting aerodynamic Blade forces are discussed for the rotor and stator Blade Rows of the first stage and the third stage of the compressor. Different operating points between design point and stability limit of the compressor were chosen to investigate the influence of loading on the aerodynamic force excitation. The time traces and the frequency contents of the unsteady aerodynamic Blade force are discussed. Strong periodic influences of the incoming wakes and of potential effects of downstream Blade Rows can be observed. The amplitude and shape of the unsteady aerodynamic Blade force depend on the interaction of the superimposed influences of the Blade Rows.

  • aerodynamic Blade Row interactions in an axial compressor part i unsteady boundary layer development
    Journal of Turbomachinery-transactions of The Asme, 2004
    Co-Authors: Ronald Mailach, Konrad Vogeler
    Abstract:

    This two-part paper presents experimental investigations of unsteady aerodynamic Blade Row interactions in the first stage of the four-stage low-speed research compressor of Dresden. Both the unsteady boundary layer development and the unsteady pressure distribution of the stator Blades are investigated for several operating points. The measurements were carried out on pressure side and suction side at midspan. In Part I of the paper the investigations of the unsteady boundary layer behavior are presented. The experiments were carried out using surface-mounted hot-film sensors. Additional information on the time-resolved flow between the Blade Rows were obtained with a hot-wire probe. The unsteady boundary layer development is strongly influenced by the incoming wakes. Within the predominantly laminar boundary layer in the front part of the Blade a clear response of the boundary layer to the velocity and turbulence structure of the incoming wakes can be observed. The time-resolved structure of the boundary layer for several operating points of the compressor is analyzed in detail. The topic calmed regions, which can be coupled to the wake passing, is discussed. As a result an improved description of the complex boundary layer structure is given.

Sanford Fleeter - One of the best experts on this subject based on the ideXlab platform.

  • multi Blade Row interactions in a transonic axial compressor part i stator particle image velocimetry piv investigation
    Journal of Turbomachinery-transactions of The Asme, 2002
    Co-Authors: Albert J Sanders, John Papalia, Sanford Fleeter
    Abstract:

    Multi-Blade Row interactions in an advanced design 1 & 1/2 stage axial-flow compressor are experimentally investigated at both subsonic and transonic rotor operating conditions using particle image velocimetry (PIV). Transonic rotor operation had a significant impact on the downstream stator unsteady flow field due to phenomena associated with the intra-stator transport of the chopped rotor wake segments. In the stator reference frame, the rotor wakes have a slip velocity relative to the mean flow that causes the low-momentum wake fluid to migrate across the vane passage and accumulate on the stator pressure surface as the chopped wake segments are transported downstream. This results in the generation of counterrotating vortices on each side of the chopped wake segment that convect downstream with the mean flow and act as an additional source of unsteadiness to the vane pressure surface. These interaction phenomena are not evident in the PIV data at the part-speed compressor operating condition due to the much lower velocity deficit and hence slip velocity associated with the subsonic rotor wakes.

  • multi Blade Row interactions in a transonic axial compressor part i stator particle image velocimetry piv investigation
    Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 2001
    Co-Authors: Albert J Sanders, John Papalia, Sanford Fleeter
    Abstract:

    Multi-Blade Row interactions in an advanced design 1&1/2 stage axial-flow compressor are experimentally investigated at both subsonic and transonic rotor operating conditions using particle image velocimetry (PIV). Transonic rotor operation had a significant impact on the downstream stator unsteady flow field due to phenomena associated with the intra-stator transport of the chopped rotor wake segments. In the stator reference frame, the rotor wakes have a slip velocity relative to the mean flow that causes the low momentum wake fluid to migrate across the vane passage and accumulate on the stator pressure surface as the chopped wake segments are transported downstream. This results in the generation of counter-rotating vortices on each side of the chopped wake segment that convect downstream with the mean flow and act as an additional source of unsteadiness to the vane pressure surface. These interaction phenomena are not evident in the PIV data at the part-speed compressor operating condition due to the much lower velocity deficit and hence slip velocity associated with the subsonic rotor wakes.Copyright © 2001 by ASME

  • measured rotor wake and potential forcing functions including Blade Row interactions
    Journal of Propulsion and Power, 1998
    Co-Authors: Robert T Johnston, John M Feiereisen, Sanford Fleeter
    Abstract:

    A fundamental experiment is directed at the acquisition and analysis of data dee ning compressible forcing functions generated by a rotor, including interactions with the upstream-generated inlet guide vane (IGV) wakes, for application to wake forcing function models in turbomachine forced-response design systems. The research fan facility consists of an IGV Row and a downstream rotor. IGV‐ rotor axial spacing is variable, with the IGV Row able to be indexed circumferentially, thereby enabling the rotor wakes to be measured both in the IGV freestream and wakes. At a rotor-relative Mach number of 0.6 unsteady measurements are made of the rotor wake pressure and velocity e elds for two IGV‐ rotor axial spacings and with the rotor wake measured in the IGV freestream and wake regions. The decay characteristics of the rotor Blade wakes are compared to empirical correlations. After Fourier decomposition, a vortical‐ potential gust splitting analysis is implemented and applied to the e rst-harmonic data to determine the vortical and potential harmonic wake gust forcing functions both upstream and downstream of the rotor. The potential gust component of the rotor wakes upstream of the rotor is found to be dominated by the e rst-harmonic component with small contributions from the second and third harmonics. Higher harmonics of the vortical gust component of the rotor wakes measured both in and out of the IGV wakes are found to be signie cantly reduced in the IGV wake regions.

Budimir Rosic - One of the best experts on this subject based on the ideXlab platform.

  • Aerodynamic Analysis of Steam Turbine Feed-Heating Steam Extractions
    Journal of Engineering for Gas Turbines and Power, 2014
    Co-Authors: Budimir Rosic, C. M. Mazzoni, Zoe Bignell
    Abstract:

    Feed-heating in steam turbines, the use of steam extracted from the turbine to heat the feed-water, is known to raise the plant efficiency and so is included in most steam turbine power plant designs. The steam is extracted through an extraction slot that runs around the casing downstream of a rotor Blade Row. The slot is connected to a plenum, which runs around the outside of the turbine annulus. Steam flows to the feed-heaters through a pipe connected usually to the bottom of the plenum. The steam extraction is driven by a circumferentially nonuniform pressure gradient in the plenum. This causes the mass flow rate of steam extracted to vary circumferentially, which affects the main passage flow downstream of the extraction point. The flow in the extraction plenum and the influence of the steam extraction on the mainstream aerodynamics is analyzed numerically in this paper. A complete annulus with the extraction slot and plenum together with the downstream stator and rotor Blade Rows is modeled in this study. The results reveal a highly nonuniform steam extraction around the annulus with the highest extraction rates from the bottom nearest the extraction pipe and the lowest at the top of the annulus. This difference in extraction rates modifies the flow angle and loss circumferential distribution downstream of the stator Blade Row. This study finds out that the distribution of steam extraction around the annulus and its influence on the main passage flow could be greatly improved by changing the shape and increasing the volume of the extraction slot and plenum.

  • control of shroud leakage loss by reducing circumferential mixing
    Journal of Turbomachinery-transactions of The Asme, 2008
    Co-Authors: Budimir Rosic, J D Denton
    Abstract:

    Shroud leakage flow undergoes little change in the tangential velocity as it passes over the shroud. Mixing due to the difference in tangential velocity between the main stream flow and the leakage flow creates a significant proportion of the total loss associated with shroud leakage flow. The unturned leakage flow also causes negative incidence and intensifies the secondary flows in the downstream Blade Row. This paper describes the experimental results of a concept to turn the rotor shroud leakage flow in the direction of the main Blade passage flow in order to reduce the aerodynamic mixing losses. A three-stage air model turbine with low aspect ratio blading was used in this study. A series of different stationary turning vane geometries placed into the rotor shroud exit cavity downstream of each rotor Blade Row was tested. A significant improvement in flow angle and loss in the downstream stator Blade Rows was measured together with an increase in turbine brake efficiency of 0.4 %.

  • the control of shroud leakage loss by reducing circumferential mixing
    Journal of Turbomachinery-transactions of The Asme, 2006
    Co-Authors: Budimir Rosic
    Abstract:

    Shroud leakage flow undergoes little change in the tangential velocity as it passes over the shroud. Mixing due to the difference in tangential velocity between the main stream flow and the leakage flow creates a significant proportion of the total loss associated with shroud leakage flow. The unturned leakage flow also causes negative incidence and intensifies the secondary flows in the downstream Blade Row. This paper describes the experimental results of a concept to turn the rotor shroud leakage flow in the direction of the main Blade passage flow in order to reduce the aerodynamic mixing losses. A three-stage air model turbine with low aspect ratio blading was used in this study. A series of different stationary turning vane geometries placed into the rotor shroud exit cavity downstream of each rotor Blade Row was tested. A significant improvement in flow angle and loss in the downstream stator Blade Rows was measured together with an increase in turbine brake efficiency of 0.4%.Copyright © 2006 by ASME

Pullan G - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Blade Row Interaction on Rotor Film Cooling
    'Organisation for Economic Co-Operation and Development (OECD)', 2020
    Co-Authors: Brind James, Pullan G
    Abstract:

    The mechanisms of Blade Row interaction affecting rotor film cooling are identified in order to make recommendations for the design of film cooling in the real, unsteady turbine environment. Present design practice makes the simplifying assumption of steady boundary conditions, despite intrinsic unsteadiness due to Blade Row interaction; we argue that if film cooling responds non-linearly to unsteadiness, the time-averaged performance will then be in error. Non-linear behaviour is confirmed using experimental measurements of flat-plate cylindrical film cooling holes, main-stream unsteadiness causing a reduction in film effectiveness of up to 31\% at constant time-averaged boundary condition. Unsteady computations are used to identify the Blade Row interaction mechanisms in a high-pressure turbine rotor: a `negative jet' associated with the upstream vane wake, and frozen and propagating vane potential field interactions. A quasi-steady model is used to predict unsteady excursions in momentum flux ratio of rotor cooling holes, with fluctuations of at least $\pm$30\% observed for all hole locations. Computations with modified upstream vanes are used to vary the relative strength of wake and potential field interactions. In general, both mechanisms contribute to rotor film cooling unsteadiness. It is recommended that the designer should choose a cooling configuration which behaves linearly over the expected unsteady excursions in momentum flux ratio as predicted by a quasi-steady hole model.Mitsubishi Heavy Industrie

  • Effect of Blade Row interaction on rotor film cooling
    2020
    Co-Authors: Brind J, Pullan G
    Abstract:

    The mechanisms of Blade Row interaction affecting rotor film cooling are identified to make recommendations for the design of film cooling in the real, unsteady turbine environment. Present design practice makes the simplifying assumption of steady boundary conditions despite intrinsic unsteadiness due to Blade Row interaction; we argue that if film cooling responds nonlinearly to unsteadiness, the time-averaged performance will then be in error. Nonlinear behavior is confirmed using experimental measurements of flat-plate cylindrical film cooling holes, mainstream unsteadiness causing a reduction in film effectiveness of up to 31% at constant time-averaged boundary condition. Unsteady computations are used to identify the Blade Row interaction mechanisms in a high-pressure turbine rotor: a “negative jet” associated with the upstream vane wake, and frozen and propagating vane potential field interactions. A quasi-steady model is used to predict unsteady excursions in momentum flux ratio of rotor cooling holes, with fluctuations of at least ±30% observed for all hole locations. Computations with modified upstream vanes are used to vary the relative strength of wake and potential field interactions. In general, both mechanisms contribute to rotor film cooling unsteadiness. It is recommended that the designer should choose a cooling configuration that behaves linearly over the expected unsteady excursions in momentum flux ratio as predicted by a quasi-steady hole model

  • Effect of Blade Row interaction on rotor film cooling
    'Organisation for Economic Co-Operation and Development (OECD)', 2020
    Co-Authors: Brind James, Pullan G
    Abstract:

    Abstract The mechanisms of Blade Row interaction affecting rotor film cooling are identified to make recommendations for the design of film cooling in the real, unsteady turbine environment. Present design practice makes the simplifying assumption of steady boundary conditions despite intrinsic unsteadiness due to Blade Row interaction; we argue that if film cooling responds nonlinearly to unsteadiness, the time-averaged performance will then be in error. Nonlinear behavior is confirmed using experimental measurements of flat-plate cylindrical film cooling holes, mainstream unsteadiness causing a reduction in film effectiveness of up to 31% at constant time-averaged boundary condition. Unsteady computations are used to identify the Blade Row interaction mechanisms in a high-pressure turbine rotor: a “negative jet” associated with the upstream vane wake, and frozen and propagating vane potential field interactions. A quasi-steady model is used to predict unsteady excursions in momentum flux ratio of rotor cooling holes, with fluctuations of at least ±30% observed for all hole locations. Computations with modified upstream vanes are used to vary the relative strength of wake and potential field interactions. In general, both mechanisms contribute to rotor film cooling unsteadiness. It is recommended that the designer should choose a cooling configuration that behaves linearly over the expected unsteady excursions in momentum flux ratio as predicted by a quasi-steady hole model.Mitsubishi Heavy Industrie

  • Effect of Blade Row interaction on rotor film cooling
    2019
    Co-Authors: Brind J, Pullan G
    Abstract:

    The mechanisms of Blade Row interaction affecting rotor film cooling are identified in order to make recommendations for the design of film cooling in the real, unsteady turbine environment. Present design practice makes the simplifying assumption of steady boundary conditions, despite intrinsic unsteadiness due to Blade Row interaction; we argue that if film cooling responds non-linearly to unsteadiness, the time-averaged performance will then be in error. Non-linear behaviour is confirmed using experimental measurements of flat-plate cylindrical film cooling holes, main-stream unsteadiness causing a reduction in film effectiveness of up to 31% at constant time-averaged boundary condition. Unsteady computations are used to identify the Blade Row interaction mechanisms in a high-pressure turbine rotor: a ‘negative jet’ associated with the upstream vane wake, and frozen and propagating vane potential field interactions. A quasi-steady model is used to predict unsteady excursions in momentum flux ratio of rotor cooling holes, with fluctuations of at least ±30% observed for all hole locations. Computations with modified upstream vanes are used to vary the relative strength of wake and potential field interactions. In general, both mechanisms contribute to rotor film cooling unsteadiness. It is recommended that the designer should choose a cooling configuration which behaves linearly over the expected unsteady excursions in momentum flux ratio as predicted by a quasi-steady hole model