The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform

Andrew Ball - One of the best experts on this subject based on the ideXlab platform.

  • ICAC - Vibration based centrifugal pump fault diagnosis based on modulation signal bispectrum analysis
    2017 23rd International Conference on Automation and Computing (ICAC), 2017
    Co-Authors: Osama Hamomd, Fengshou Gu, Samir Alabied, Yuandong Xu, Alsadak Daraz, Andrew Ball
    Abstract:

    This paper characterises vibration signals using modulation signal bispectrum method in order to develop an effective and reliable feature sets for detecting and diagnosing faults from both the bearings and impellers in a centrifugal pump. As vibration signals contain high level background noises due to inevitable flow cavitation and turbulences, effective noise reduction and reliable feature extraction are critical procedures in vibration signal analysis. Considering the modulation effect between rotating shaft and Vane passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulating components in a low frequency band for diagnosing both the bearing defects and impeller blockages. Experimental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and bearing outer-race faults to be identified under different operating conditions. Not only does this new method produces reliable diagnostic results but also it needs a bandwidth about 1000Hz, rather than the high frequency bands around 10kHz used by conventional envelope analysis.

  • Vibration based centrifugal pump fault diagnosis based on modulation signal bispectrum analysis
    2017 23rd International Conference on Automation and Computing (ICAC), 2017
    Co-Authors: Osama Hamomd, Fengshou Gu, Samir Alabied, Yuandong Xu, Alsadak Daraz, Andrew Ball
    Abstract:

    This paper characterises vibration signals using modulation signal bispectrum method in order to develop an effective and reliable feature sets for detecting and diagnosing faults from both the bearings and impellers in a centrifugal pump. As vibration signals contain high level background noises due to inevitable flow cavitation and turbulences, effective noise reduction and reliable feature extraction are critical procedures in vibration signal analysis. Considering the modulation effect between rotating shaft and Vane passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulating components in a low frequency band for diagnosing both the bearing defects and impeller blockages. Experimental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and bearing outer-race faults to be identified under different operating conditions. Not only does this new method produces reliable diagnostic results but also it needs a bandwidth about 1000Hz, rather than the high frequency bands around 10kHz used by conventional envelope analysis.

  • A NEW METHOD OF VIBRATION ANALYSIS FOR THE DIGANOSIS OF IMPELLER IN A CENTRIFUGAL PUMP
    2014
    Co-Authors: Osama Hamomd, Xiange Tian, Zhi Chen, Abdulrahman Al-braik, Fengshou Gu, Andrew Ball
    Abstract:

    Centrifugal pumps are widely used in many important industries such as power generation plants, chemical processes and petroleum refiners. The condition monitoring of centrifugal pumps is highly regarded by many researchers and users to minimize unexpected break-downs. Impellers are the core parts of pumps but often appear early damages due to flow cav-itation and erosion. This paper investigates a new approach to monitoring the conditions of impellers using surface vibration with advanced signal analysis. As overall vibration respons-es contain high level of broadband noises due to cavities and turbulences, noise reduction is critical to develop reliable and effective features. However, considering the modulation effect between rotating shaft and blade passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulations, which is different from previous researches in that broadband random sources are often used. Experi-mental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and exit Vane faults to be identified under different operating conditions.

  • The investigation of motor current signals from a centrifugal pump for fault diagnosis
    2014
    Co-Authors: Xiange Tian, Guojin Feng, Zhi Chen, Abdulrahman Al-braik, Fengshou Gu, Andrew Ball
    Abstract:

    In this paper, motor current signals from electrical control systems, rather than installing additional measurement systems, are characterised for the fault diagnosis of centrifugal pumps. Modulation signal bispectrum (MSB) analysis is applied to reveal the weak nonlinear characteristics of current signals when the pump with different impeller faults operates under a wide range of flow conditions. Experimental results show that two static features including the amplitude at supply frequency and the frequency value of bar-passing frequency can be based on to diagnose impeller defects on exit Vane tips and Inlet Vane tips. In addition, the dynamic parameter of sidebands at Vane-passing frequency can also be a good indicator for differentiating between the faults.

Osama Hamomd - One of the best experts on this subject based on the ideXlab platform.

  • Compound Fault Diagnosis of Centrifugal Pumps Using Vibration Analysis Techniques
    2018
    Co-Authors: Osama Hamomd
    Abstract:

    Centrifugal pumps are widely used in many different industrial processes, such as power generation stations, chemical processing plants, and petroleum industries. The problem of failures in centrifugal pumps is a large concern due to its significant influence on such critical industries. Particularly, as the core, parts of a pump, bearings and the impellers are subject to different corrosions and their faults can cause major degradation of pump performances and lead to the breakdown of production. Therefore, an early detection of these types of faults would provide information to take timely preventive actions. This research investigates more effective techniques for diagnosing common faults of impellers and bearings with advanced signal analysis of surface vibration. As overall vibration responses contain a high level of broadband noises due to fluid cavities and turbulences, noise reduction is critical to developing reliable and accurate features. However, considering the modulation effect between the rotating shaft, Vane passing components and any structural resonances, a modulation signal bispectrum (MSB) method is mainly used to extract these deterministic characteristics of modulations, which differs from previous researches in that the broadband vibration is often characterised with statistical methods, high frequency demodulation along spectrum analysis. Both theoretical analysis and experimental evaluation show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and exit Vane faults to be identified under different operating conditions. It starts with an in-depth examination of the vibration excitation mechanisms associated with each type of common pump faults including impeller leakages, impeller blockages, bearing inner race defects and bearing outrace defects. Subsequently, fault diagnosis was carried out using popular spectrum and envelope analysis, and more advanced kurtogram and MSB analysis. These methods all can successfully provide correct detection and diagnosis of the faults, which are induced manually to the test pump. Envelope analysis in a bands optimised with Kurtogram produces outstanding detection results for bearing faults but not the impeller faults in a frequency range as high as several thousand hertz (about 7.5kHz). In addition, it cannot provide satisfactory diagnostic results in separating the faults across different flow rates, especially when the compound faults were evaluated. This deficiency is because they do not have the capability of suppressing the random noises. Meanwhile, it has found that the MSB analysis allows both impeller and bearing faults to be detected and diagnosed. Especially, when the pump operated with compound faults both the fault types and severity can be attained by the analysis with acceptable accuracy for different flow rates. This high performance of diagnosis is due to that MSB has the unique capability of noise reduction and nonlinearity demodulation. Moreover, MSB diagnosis can be a frequency range lower than 2 times of the blade pass frequency (

  • ICAC - Vibration based centrifugal pump fault diagnosis based on modulation signal bispectrum analysis
    2017 23rd International Conference on Automation and Computing (ICAC), 2017
    Co-Authors: Osama Hamomd, Fengshou Gu, Samir Alabied, Yuandong Xu, Alsadak Daraz, Andrew Ball
    Abstract:

    This paper characterises vibration signals using modulation signal bispectrum method in order to develop an effective and reliable feature sets for detecting and diagnosing faults from both the bearings and impellers in a centrifugal pump. As vibration signals contain high level background noises due to inevitable flow cavitation and turbulences, effective noise reduction and reliable feature extraction are critical procedures in vibration signal analysis. Considering the modulation effect between rotating shaft and Vane passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulating components in a low frequency band for diagnosing both the bearing defects and impeller blockages. Experimental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and bearing outer-race faults to be identified under different operating conditions. Not only does this new method produces reliable diagnostic results but also it needs a bandwidth about 1000Hz, rather than the high frequency bands around 10kHz used by conventional envelope analysis.

  • Vibration based centrifugal pump fault diagnosis based on modulation signal bispectrum analysis
    2017 23rd International Conference on Automation and Computing (ICAC), 2017
    Co-Authors: Osama Hamomd, Fengshou Gu, Samir Alabied, Yuandong Xu, Alsadak Daraz, Andrew Ball
    Abstract:

    This paper characterises vibration signals using modulation signal bispectrum method in order to develop an effective and reliable feature sets for detecting and diagnosing faults from both the bearings and impellers in a centrifugal pump. As vibration signals contain high level background noises due to inevitable flow cavitation and turbulences, effective noise reduction and reliable feature extraction are critical procedures in vibration signal analysis. Considering the modulation effect between rotating shaft and Vane passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulating components in a low frequency band for diagnosing both the bearing defects and impeller blockages. Experimental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and bearing outer-race faults to be identified under different operating conditions. Not only does this new method produces reliable diagnostic results but also it needs a bandwidth about 1000Hz, rather than the high frequency bands around 10kHz used by conventional envelope analysis.

  • A NEW METHOD OF VIBRATION ANALYSIS FOR THE DIGANOSIS OF IMPELLER IN A CENTRIFUGAL PUMP
    2014
    Co-Authors: Osama Hamomd, Xiange Tian, Zhi Chen, Abdulrahman Al-braik, Fengshou Gu, Andrew Ball
    Abstract:

    Centrifugal pumps are widely used in many important industries such as power generation plants, chemical processes and petroleum refiners. The condition monitoring of centrifugal pumps is highly regarded by many researchers and users to minimize unexpected break-downs. Impellers are the core parts of pumps but often appear early damages due to flow cav-itation and erosion. This paper investigates a new approach to monitoring the conditions of impellers using surface vibration with advanced signal analysis. As overall vibration respons-es contain high level of broadband noises due to cavities and turbulences, noise reduction is critical to develop reliable and effective features. However, considering the modulation effect between rotating shaft and blade passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulations, which is different from previous researches in that broadband random sources are often used. Experi-mental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and exit Vane faults to be identified under different operating conditions.

Fengshou Gu - One of the best experts on this subject based on the ideXlab platform.

  • ICAC - Vibration based centrifugal pump fault diagnosis based on modulation signal bispectrum analysis
    2017 23rd International Conference on Automation and Computing (ICAC), 2017
    Co-Authors: Osama Hamomd, Fengshou Gu, Samir Alabied, Yuandong Xu, Alsadak Daraz, Andrew Ball
    Abstract:

    This paper characterises vibration signals using modulation signal bispectrum method in order to develop an effective and reliable feature sets for detecting and diagnosing faults from both the bearings and impellers in a centrifugal pump. As vibration signals contain high level background noises due to inevitable flow cavitation and turbulences, effective noise reduction and reliable feature extraction are critical procedures in vibration signal analysis. Considering the modulation effect between rotating shaft and Vane passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulating components in a low frequency band for diagnosing both the bearing defects and impeller blockages. Experimental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and bearing outer-race faults to be identified under different operating conditions. Not only does this new method produces reliable diagnostic results but also it needs a bandwidth about 1000Hz, rather than the high frequency bands around 10kHz used by conventional envelope analysis.

  • Vibration based centrifugal pump fault diagnosis based on modulation signal bispectrum analysis
    2017 23rd International Conference on Automation and Computing (ICAC), 2017
    Co-Authors: Osama Hamomd, Fengshou Gu, Samir Alabied, Yuandong Xu, Alsadak Daraz, Andrew Ball
    Abstract:

    This paper characterises vibration signals using modulation signal bispectrum method in order to develop an effective and reliable feature sets for detecting and diagnosing faults from both the bearings and impellers in a centrifugal pump. As vibration signals contain high level background noises due to inevitable flow cavitation and turbulences, effective noise reduction and reliable feature extraction are critical procedures in vibration signal analysis. Considering the modulation effect between rotating shaft and Vane passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulating components in a low frequency band for diagnosing both the bearing defects and impeller blockages. Experimental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and bearing outer-race faults to be identified under different operating conditions. Not only does this new method produces reliable diagnostic results but also it needs a bandwidth about 1000Hz, rather than the high frequency bands around 10kHz used by conventional envelope analysis.

  • A NEW METHOD OF VIBRATION ANALYSIS FOR THE DIGANOSIS OF IMPELLER IN A CENTRIFUGAL PUMP
    2014
    Co-Authors: Osama Hamomd, Xiange Tian, Zhi Chen, Abdulrahman Al-braik, Fengshou Gu, Andrew Ball
    Abstract:

    Centrifugal pumps are widely used in many important industries such as power generation plants, chemical processes and petroleum refiners. The condition monitoring of centrifugal pumps is highly regarded by many researchers and users to minimize unexpected break-downs. Impellers are the core parts of pumps but often appear early damages due to flow cav-itation and erosion. This paper investigates a new approach to monitoring the conditions of impellers using surface vibration with advanced signal analysis. As overall vibration respons-es contain high level of broadband noises due to cavities and turbulences, noise reduction is critical to develop reliable and effective features. However, considering the modulation effect between rotating shaft and blade passing components, a modulation signal bispectrum (MSB) method is employed to extract these deterministic characteristics of modulations, which is different from previous researches in that broadband random sources are often used. Experi-mental results show that the diagnostic features developed by MSB allow impellers with Inlet Vane damages and exit Vane faults to be identified under different operating conditions.

  • The investigation of motor current signals from a centrifugal pump for fault diagnosis
    2014
    Co-Authors: Xiange Tian, Guojin Feng, Zhi Chen, Abdulrahman Al-braik, Fengshou Gu, Andrew Ball
    Abstract:

    In this paper, motor current signals from electrical control systems, rather than installing additional measurement systems, are characterised for the fault diagnosis of centrifugal pumps. Modulation signal bispectrum (MSB) analysis is applied to reveal the weak nonlinear characteristics of current signals when the pump with different impeller faults operates under a wide range of flow conditions. Experimental results show that two static features including the amplitude at supply frequency and the frequency value of bar-passing frequency can be based on to diagnose impeller defects on exit Vane tips and Inlet Vane tips. In addition, the dynamic parameter of sidebands at Vane-passing frequency can also be a good indicator for differentiating between the faults.

Jamie J. Johnson - One of the best experts on this subject based on the ideXlab platform.

  • Infrared Assessment of an Optimized Vane Pressure Side Film Cooling Array
    Volume 7: Fluids and Heat Transfer Parts A B C and D, 2012
    Co-Authors: Jamie J. Johnson, Paul I. King, John P. Clark, Andrew Lethander, Natalia A. Posada
    Abstract:

    The following experimental work described here entails the investigation by infrared thermography (IRT) of full-scale flat plates intended to model the pressure side (PS) of a modern fully-cooled turbine Inlet Vane called the High-Impact Technologies (HIT) Research Turbine Vane (RTV). The imaging system is used to make detailed full-coverage, two-dimensional, steady-state measurements of flat plate surface temperature. The PS has a total of 282 film cooling holes including three rows of showerhead holes near the leading edge and a handful of rows downstream depending on the design. The flat plates precisely match the material, thickness, and cooling hole sizes on the RTV, however they are not intended to match the external pressure field or the characteristics of internal cooling beneath the airfoil surface. Surface temperature relative to individual trial freestream gas temperatures is reported for an uncooled plate, a plate with the baseline RTV cooling scheme, and for four different hole types on a plate with a 3D-optimized cooling array designed for the RTV in previous work using genetic algorithms and computational fluid dynamics (CFD). The four different cooling hole shapes tested on the downstream rows of the optimized array plates include cylindrical holes, fan-shaped holes, Vehr holes, and a new cooling hole called a mini-trench shaped (MTS) hole. Experimentation on flat plate models using infrared thermography provides large amounts of valuable data, is inexpensive and highly repeatable relative to large rotating blowdown rigs. The results provide key insights into the differences between full-PS film cooling performance on the plate versus the 3D RTV and suggests to designers the best cooling hole shape for the next build of the RTV which will soon be tested in a full-scale blowdown rig instrumented with heat flux gauges. Overall, results clearly corroborate how cooling was redistributed and improved over the PS of the RTV in the original computational design effort and suggest that certain hole shapes are best suited for certain locations on the flat plate models.© 2012 ASME

  • Optimization of a Low Heat Load Turbine Nozzle Guide Vane
    2012
    Co-Authors: Jamie J. Johnson
    Abstract:

    Abstract : Often turbomachinery airfoils are designed with aerodynamic performance foremost in mind rather than component durability. However, future aircraft systems require ever increasing levels of gas-turbine Inlet temperature causing the durability and reliability of turbine components to be an ever more important design concern. As a result, the need to provide improved heat transfer prediction and optimization methods presents itself. Here, an effort to design an airfoil with minimized heat load is reported. First, a Reynolds-Averaged Navier-Stokes (RANS) flow solver was validated over different flow regimes as well as varying boundary conditions against extensive data available in literature published by the Von Karman Institute (VKI). Next, a nominal turbine Inlet Vane was tested experimentally for heat load measurements in a shock tube linear cascade with special attention paid to leading edge and suction side characteristics and used to validate the flow solver further at the experimental conditions. The nominal airfoil geometry was then redesigned for minimum heat load by means of both design practice and two types of optimization algorithms. Finally, the new airfoil was tested experimentally and heat load trends were compared to design levels as well as the nominal Vane counterpart. Results indicate an appreciable reduction in heat load relative to the original Vane computationally and experimentally providing credible evidence to further bolster the practice of preliminary design of turbine components solely with respect to heat transfer using computational models and methods traditionally employed purely by aerodynamicists.

  • Exploring Conjugate CFD Heat Transfer Characteristics for a Film-Cooled Flat Plate and 3-D Turbine Inlet Vane
    Volume 4: Heat Transfer Parts A and B, 2012
    Co-Authors: Jamie J. Johnson, Paul I. King, John P. Clark, Peter J. Koch
    Abstract:

    As part of a thorough benchmarking of the baseline cooling design in planned optimization work, Reynolds-Averaged Navier Stokes (RANS) conjugate heat transfer (CHT) computational fluid dynamics (CFD) assessments have been accomplished at RTV design flow conditions to simulate both a cooled flat plate pressure side (PS) model infrared thermography experiment as well as a full-scale, fully-cooled, full-wheel blowdown experiment on the same high pressure turbine (HPT) Vane. Numerous past works on turbomachinery film cooling have been conducted using flat plate models because of their simplicity, repeatability, and low cost of experimentation relative to full scale rotating blowdown rigs. Some of these works generated film cooling correlations still in use today in industry for HPT components. The CFD assessments in this work provide insight into the fundamental differences between a flat plate model and a realistic 3-D Vane in terms of film cooling performance for the same PS cooling array. The comparisons of results wring out expected differences between the geometries due to aspects such as highly curved surfaces and endwall effects. However, with nearly-matched coolant-to-mainstream temperature and pressure ratios, the cooling performance between the two models is surprisingly similar, especially in the midspan region. The similarities and differences observed herein represent the rigor and accuracy afforded by simulating both the solid and fluid domains as well as the high-density unstructured meshes that take into account all individual cooling passages and internal plenums, on top of the typically-assessed external fluid flow field.© 2012 ASME

  • Three-Dimensional Film-Cooled Vane CFD Simulations and Preliminary Comparison to Experiments
    49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2011
    Co-Authors: Jamie J. Johnson, Paul I. King, John P. Clark, Peter J. Koch, Richard J. Anthony, Michael K. Ooten, Emilee A. Kasik, Ron-ho Ni
    Abstract:

    Reynolds-Averaged Navier Stokes (RANS) computational fluid dynamics (CFD) simulations are conducted using the Wilcox k-ω turbulence model within a code called LEO on a threedimensional fully film-cooled modern turbine Inlet Vane called the High Impact Technologies (HIT) Research Turbine Vane (RTV). External flows at operating conditions around the Vane and their interaction with film cooling flows from the Vane leading edge, pressure side (PS), suction side (SS), trailing edge, and hub and tip endwalls are modeled. The film cooling is modeled using a local source term in the governing equations for the added mass flux at the appropriate locations in the fluid domain along the Vane surface. Cooled and uncooled isothermal Vane simulations are conducted. Predictions of stream-wise distributions of heat flux and net heat flux reduction (NHFR) at two span locations are provided and compared to Vane-only-configuration heat flux data recently obtained in the Air Force Research Laboratory (AFRL) Turbine Research Facility (TRF) short-duration blowdown facility. Details on proper matching of experimental boundary conditions for the CFD simulations are also given in order to provide a validation case for the maturing CFD code. Uncooled and cooled experimental data show appropriate relative trends, as do the uncooled and cooled predictions. However, comparing heat flux data to predictions shows disparities that require further investigation of the cooling modeling technique and appropriate assumptions going into the model.

  • Low-Heat-Load-Vane Profile Optimization, Part 2: Short-Duration Shock-Tunnel Experiments
    Journal of Propulsion and Power, 2008
    Co-Authors: Jamie J. Johnson, Paul I. King, John P. Clark, Michael J. Flanagan, Ryan P. Lemaire
    Abstract:

    Complete knowledge of the heat transfer over the surfaces of turbine components within their harsh operating environments is key to knowing the durability of a given airfoil design. Here, a nominal turbine Inlet Vane was tested for unsteady-heat-load measurements in a low-aspect-ratio linear cascade. A new airfoil called the low-heat-load Vane, designed specifically for a reduced heat load, was tested experimentally and unsteady-heat-load trends were compared with the nominal Vane counterpart. The tests were performed in a reflected-shock tunnel to validate the flow solver and turbomachinery design system used to generate the new airfoil shape, for which special attention was paid to leading-edge and suction-side heat-flux characteristics. Results indicate an appreciable reduction in heat load relative to the nominal Vane. This work lends credibility to designing turbine airfoils for durability with the same emphasis normally given to designing for aeroperformance.

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

  • Turbine Blade Unsteady Heat Transfer Change due to Stator Indexing
    Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration, 1999
    Co-Authors: David Johnston, Sanford Fleeter
    Abstract:

    Stator indexing to alter and/or control the unsteady heat transfer of closely spaced airfoil rows in turbomachinery was studied experimentally in a two-stage low-speed research turbine. With the second Vane row fixed, the Inlet Vane row was indexed to six positions over one Vane-pitch cycle at design and high stage loadings. The aerodynamic forcing functions to the first- and second-stage rotors were measured in the rotating reference frame, with the resulting rotor blade unsteady heat transfer response quantified by an electrically heated rotor blade instrumented with thin platinum-film heat gages. The level of attenuation of unsteady heat transfer coefficient due to stator indexing was found to be both location and blade loading dependent, ranging from 10% to 80% of the maximum. Because of the attenuation’s location dependence, stator indexing is therefore best suited to minimize unsteady heat transfer in local hot spots on the blade.Copyright © 1999 by ASME

  • Turbine blade unsteady loading change due to stator indexing
    34th AIAA ASME SAE ASEE Joint Propulsion Conference and Exhibit, 1998
    Co-Authors: David Johnston, Sanford Fleeter
    Abstract:

    Stator indexing to minimize the unsteady aerodynamic loading of closely spaced airfoil rows is a new technique for the passive control of flow-induced vibrations. This technique is studied by means of experiments performed in a two-stage, low-speed, research turbine. With the second Vane row fixed, the Inlet Vane row is indexed to six positions over one Vane-pitch cycle for a range of stage loadings. The aerodynamic forcing function to the first-stage rotor is measured in the rotating reference frame, with the resulting rotor blade unsteady aerodynamic response quantified by rotor blades instrumented with dynamic pressure transducers. Reductions in the unsteady lift magnitude were achieved at all turbine operating conditions, with attenuation ranging from 37% to 74% of the maximum unsteady lift. NOMENCLATURE C chord Cp time-mean pressure coefficient Acp unsteady pressure difference coefficient, Ap/pQ, pressure surface suction surface CL unsteady lift coefficient (sectional) k reduced frequency, caC/Q fvpc fractional Vane-pitch cycle p unsteady static pressure Q tune-mean velocity magnitude, relative frame r radius M,V,W unsteady streamwise, transverse, radial velocity component U, V, W time-mean axial, tangential, radial velocity unsteady potential (P flow coefficient, L//FW p density co circular frequency of unsteadiness u unsteady velocity f blade loading coefficient, (Vi-V\)IVv subscripts 1,2 upstream, downstream of rotor blade m, v, p measured, vortical, potential perturbation x axial w wheel speed