scholarly journals Interaction of Rim Seal and Annulus Flows in an Axial Flow Turbine

2004 ◽  
Vol 126 (4) ◽  
pp. 786-793 ◽  
Author(s):  
C. Cao ◽  
J. W. Chew ◽  
P. R. Millington ◽  
S. I. Hogg
Keyword(s):  
Axial Flow ◽  
Fast Response ◽  
Pressure Measurements ◽  
Cfd Models ◽  
Flow Features ◽  
Rotor Disk ◽  
Computational Fluid Dynamics Cfd ◽  
Axial Clearance ◽  
Response Pressure ◽  
Good Agreement

A combined computational fluid dynamics (CFD) and experimental study of interaction of main gas path and rim sealing flow is reported. The experiments were conducted on a two stage axial turbine and included pressure measurements for the cavity formed between the stage 2 rotor disk and the upstream diaphragm for two values of the diaphragm-to-rotor axial clearance. The pressure measurements indicate that ingestion of the highly swirling annulus flow leads to increased vortex strength within the cavity. This effect is particularly strong for the larger axial clearance. Results from a number of steady and unsteady CFD models have been compared to the measured results. Good agreement between measurement and calculation for time-averaged pressures was obtained using unsteady CFD models, which predicted previously unknown unsteady flow features. This led to fast response pressure transducer measurements being made on the rig, and these confirmed the CFD prediction.

scholarly journals Interaction of Rim Seal and Annulus Flows in an Axial Flow Turbine

2003 ◽  
Author(s):  
C. Cao ◽  
J. W. Chew ◽  
P. R. Millington ◽  
S. I. Hogg
Keyword(s):  
Axial Flow ◽  
Fast Response ◽  
Pressure Measurements ◽  
Cfd Models ◽  
Annulus Flow ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Axial Clearance ◽  
Response Pressure ◽  
Good Agreement

A combined computational fluid dynamics (CFD) and experimental study of interaction of main gas path and rim sealing flow is reported. The experiments were conducted on a two stage axial turbine and included pressure measurements for the cavity formed between the stage 2 rotor disc and the upstream diaphragm for two values of the diaphragm-to-rotor axial clearance. The pressure measurements indicate that ingestion of the highly swirling annulus flow leads to increased vortex strength within the cavity. This effect is particularly strong for the larger axial clearance. Results from a number of steady and unsteady CFD models have been compared to the measured results. Good agreement between measurement and calculation for time-averaged pressures was obtained using unsteady CFD models, which predicted previously unknown unsteady flow features. This led to fast response pressure transducer measurements being made on the rig, and these confirmed the CFD prediction.

scholarly journals A Parallel CFD Tool to Produce Faulty Blade Signatures for Diagnostic Purposes

1998 ◽  
Author(s):  
D. G. Koubogiannis ◽  
V. P. Iliadis ◽  
K. C. Giannakoglou
Keyword(s):  
High Speed ◽  
Unstructured Grids ◽  
Fast Response ◽  
Operating Conditions ◽  
Pressure Measurements ◽  
Diagnostic Systems ◽  
Compressor Cascade ◽  
Computational Fluid Dynamics Cfd ◽  
Response Pressure ◽  
The One

In the turbomachinery field, many diagnostic systems utilize databases with symptoms corresponding to the most frequent operation faults. Thanks to Computational Fluid Dynamics (CFD), databases can be created without costly experiments, whereas the use of unstructured grids in combination with parallel processing makes the whole task easy and fast to accomplish. In this paper, a procedure that builds up a database for gas-turbine fault diagnosis is demonstrated. Advanced CFD tools that operate concurrently on multi-processor platforms are used. The so-prepared database contributes to the identification of faults through the analysis of the unsteady pressure signals that correspond to hypothetical sensors located in the inter-blade region. The pressure signals are post-processed in a similar way to the one experimentalists employ for fast-response pressure measurements. Symptoms related to displaced and/or twisted blades in an industrial high-speed compressor cascade, at design and off-design operating conditions, are analyzed.

An Experimental Investigation of the Flow Through an Axial-Flow Pump

1995 ◽  
Vol 117 (3) ◽  
pp. 485-490 ◽  
Author(s):  
W. C. Zierke ◽  
W. A. Straka ◽  
P. D. Taylor
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Axial Flow ◽  
Fast Response ◽  
Complex Flow ◽  
Penn State ◽  
Response Pressure ◽  
Axial Flow Pump ◽  
Scale Experiment ◽  
High Reynolds

The high Reynolds number pump (HIREP) facility at ARL Penn State has been used to perform a low-speed, large-scale experiment of the incompressible flow of water through a two-blade-row turbomachine. The objectives of this experiment were to provide a database for comparison with three-dimensional, turbulent flow computations, to evaluate engineering models, and to improve our physical understanding of many of the phenomena involved in this complex flow field. This summary paper briefly describes the experimental facility, as well as the experimental techniques—such as flow visualization, static-pressure measurements, laser Doppler velocimetry, and both slow- and fast-response pressure probes. Then, proceeding from the inlet to the exit of the pump, the paper presents highlights of experimental measurements and data analysis, giving examples of measured physical phenomena such as endwall boundary layers, separation regions, wakes, and secondary vortical structures. In conclusion, this paper provides a synopsis of a well-controlled, larger scope experiment that should prove helpful to those who wish to use the database.

Prediction and Validation of the Transient Pressure Field in a Centrifugal Compressor With Vaned Diffuser for the Application in High Cycle Fatigue Stress Estimations

2021 ◽  
Author(s):  
Gökay Bacakci ◽  
Friedrich Fröhlig ◽  
Lukas Stuhldreier ◽  
Johannes Deutsch ◽  
Peter Jeschke
Keyword(s):  
Centrifugal Compressor ◽  
High Cycle Fatigue ◽  
Pressure Field ◽  
Transient Flow ◽  
Pressure Fluctuations ◽  
Fast Response ◽  
Pressure Measurements ◽  
Cycle Fatigue ◽  
Transient Pressure ◽  
Response Pressure

Abstract In this paper, the transient pressure field in a centrifugal compressor is predicted by the Nonlinear Harmonic (NLH) method, as well as the unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations and validated by transient pressure measurements. The accurate prediction of these pressure fluctuations is crucial, because they have a significant influence on the High-Cycle-Fatigue (HCF) behavior in turbomachinery applications. As the first step, excited and non-excited rotational speeds, caused by rotor-stator interactions, are identified by modal analysis performed on a single segment impeller assembly. In order to eliminate any additional pressure fluctuations caused by blade vibrations, three non-excited operating points at different rotational speed levels are selected for the transient flow simulations. The transient pressure fields predicted by these methods are validated by transient pressure measurements at three circumferentially different locations on the impeller shroud. A study of the modeling of these fast-response pressure probes in numerical calculations also falls within the scope of this work in order to identify its effect on the transient pressure amplitudes. The results of the numerical calculations and measurements are compared in the frequency domain by performing Fast-Fourier Transformations (FFT) and Short-Time Fourier Transformations (STFT) on the numerical and experimental data respectively. It is shown that the transient pressure field in a single staged centrifugal compressor is calculated accurately by both of the numerical methods in comparison to the transient flow measurements. This paper demonstrates that the numerical modeling of the fast-response pressure sensors has a significant impact on the unsteady pressure amplitudes, which needs to be taken into account for a reliable experimental validation process.

scholarly journals Analysis of Simulated Axial-Flow Turbomachine Wakes for Estimation of Frequency-Response Requirements for Fast-Response Pressure Probes

1974 ◽  
Author(s):  
G. H. Junkhan
Keyword(s):  
Frequency Response ◽  
Axial Flow ◽  
Fast Response ◽  
Maximum Pressure ◽  
Pressure Time ◽  
Total Head ◽  
Blade Row ◽  
Probe Frequency ◽  
Response Pressure ◽  
Electronic Filters

Various types of fast-response pressure probes are currently used in turbomachines. One application of these probes is for the measurement of time varying total pressures downstream of an aixal-flow machine rotor. In this paper, the frequency-response requirements for a probe placed in such a stream are estimated using a simulated wake pressure-time function. The analysis indicates that the minimum required response depends mainly on the maximum pressure difference from wake to free stream, the blade passing frequency and the blade row geometry. One of the assumptions made in the analysis is that a fast-response probe with a short total head tube in front of the transducer behaves approximately as a second-order dynamic system. Experimental results are given to illustrate probe behavior both in frequency-response tests and behind an axial-flow rotor. Improved probe frequency response using electronic filters is also illustrated.

Use of Pressure Measurements to Determine Effectiveness of Turbine Rim Seals

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
J. Michael Owen ◽  
Kang Wu ◽  
James A. Scobie ◽  
Carl M. Sangan ◽  
GeonHwan Cho ◽  
...  
Keyword(s):  
Pressure Difference ◽  
Radial Clearance ◽  
Pressure Measurements ◽  
Sweet Spot ◽  
Hot Gas ◽  
Mainstream Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Concentration Measurements ◽  
Arbitrary Location ◽  
Good Agreement

The ingress of hot gas through the rim seal of a gas turbine depends on the pressure difference between the mainstream flow in the turbine annulus and that in the wheel-space radially inward of the rim seal. In this paper, a previously published orifice model is modified so that the sealing effectiveness εc determined from concentration measurements in a rig could be used to determine εp, the effectiveness determined from pressure measurements in an engine. It is assumed that there is a hypothetical “sweet spot” on the vane platform where the measured pressures would ensure that the calculated value of εp equals εc, the value determined from concentration measurements. Experimental measurements for a radial-clearance seal show that, as predicted, the hypothetical pressure difference at the sweet spot is linearly related to the pressure difference measured at an arbitrary location on the vane platform. There is good agreement between the values of εp determined using the theoretical model and values of εc determined from concentration measurements. Supporting computations, using a 3D steady computational fluid dynamics (CFD) code, show that the axial location of the sweet spot is very close to the upstream edge of the seal clearance. It is shown how parameters obtained from measurements of pressure and concentration in a rig could, in principle, be used to calculate the sealing effectiveness in an engine.

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

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

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

Multiphase CFD Analysis of a Subsea Intervention System

2015 ◽  
Author(s):  
Elham Maghsoudi ◽  
Uday Godse ◽  
Alistair Gill
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Large Scale ◽  
Cfd Analysis ◽  
Cfd Models ◽  
System A ◽  
Mixing Behavior ◽  
Computational Fluid Dynamics Cfd ◽  
2D And 3D ◽  
Good Agreement

In this study, a computational fluid dynamics (CFD) analysis was conducted to evaluate a new design of an intervention system. A multiphase analysis was performed to understand the mixing characteristics as the cement is pumped into the well and the degree to which the cement could be contaminated with spacer fluid. A transient multiphase analysis was conducted to examine the flow and the mixing behavior through the various sections of the intervention system. A combination of 2D and 3D CFD models was used, depending upon the geometry in each section. The results indicated that the intervention system operates efficiently without diluting the cement. Non-Newtonian methods used in CFD were validated using available theoretical and experimental data. In a large-scale yard test, good agreement was obtained for resin and water; however, cement did not show good agreement as the flow rate increased over 1 bbl/min.

Application of Complex Demodulation for Pseudo-Key-Phasor Recovery From Fast-Response Pressure Measurements

2014 ◽  
Author(s):  
Jordan W. Ilott ◽  
W. D. E. Allan ◽  
Asad Asghar
Keyword(s):  
High Speed ◽  
Phase Synchronization ◽  
Mechanical Design ◽  
Fast Response ◽  
Pressure Measurements ◽  
Sampled Data ◽  
Rotor Speed ◽  
Pressure Transducers ◽  
Complex Demodulation ◽  
Response Pressure

When digitizing the output of fast-response pressure transducers installed on rotating machinery, it is often desirable to use a phase-synchronized method. The mechanical design of many turbomachines, particularly those not originally designed for a research application, can make it difficult to install the physical key-phasor needed to acquire phase-synchronized measurements. A method of phase-synchronization using a pseudo-key-phasor is presented in this paper. The technique applies complex demodulation to recover a pseudo-key-phasor signal from the blade-passing signal recorded in sampled data. The recovered pseudo-key-phasor is then used to digitally resample the data at a constant phase angle, removing the effect of small rotor speed variations. Example applications of this technique to vibration measurements can be found in the literature; however, examples of application to rotor pressure measurement were not. The technique has been applied to fast-response pressure measurements taken on the shroud of a high speed centrifugal compressor. It was found that this technique was able to remove the effect of rotor speed variations from data sampled with equal time intervals, making them suitable for phase averaging.

Ground Flutter Simulation Test Based on Reduced Order Modeling of Aerodynamics by CFD/CSD Coupling Method

2019 ◽  
Vol 11 (01) ◽  
pp. 1950008
Author(s):  
Binwen Wang ◽  
Xueling Fan
Keyword(s):  
Aerodynamic Force ◽  
Test System ◽  
Simulation Test ◽  
Robust Controller ◽  
Test Technique ◽  
Reduced Order ◽  
Aerodynamic Model ◽  
Flutter Boundary ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Flutter is an aeroelastic phenomenon that may cause severe damage to aircraft. Traditional flutter evaluation methods have many disadvantages (e.g., complex, costly and time-consuming) which could be overcome by ground flutter test technique. In this study, an unsteady aerodynamic model is obtained using computational fluid dynamics (CFD) code according to the procedure of frequency domain aerodynamic calculation. Then, the genetic algorithm (GA) method is adopted to optimize interpolation points for both excitation and response. Furthermore, the minimum-state method is utilized for rational fitting so as to establish an aerodynamic model in time domain. The aerodynamic force is simulated through exciters and the precision of simulation is guaranteed by multi-input and multi-output robust controller. Finally, ground flutter simulation test system is employed to acquire the flutter boundary through response under a range of air speeds. A good agreement is observed for both velocity and frequency of flutter between the test and modeling results.

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