scispace - formally typeset
Search or ask a question

Showing papers on "Axial compressor published in 2000"


Journal ArticleDOI
TL;DR: In this article, the rotational instability (RI) is observed in axial flow fans, centrifugal compressors as well as in low-speed and high-speed axial compressors.
Abstract: Rotating instabilities (RI) have been observed in axial flow fans, centrifugal compressors as well as in low-speed and high-speed axial compressors. They are responsible for the excitation of high amplitude rotor blade vibrations and noise generation. This flow phenomenon moves relative to the rotor blades and causes periodic vortex separations at the blade tips and an axial reversed flow through the tip clearance of the rotor blades.The paper describes experimental investigations of RI in the Dresden Low-Speed Research Compressor (LSRC). The objective is to show that the fluctuation of the blade tip vortex is responsible for the origination of this flow phenomenon.RI have been found at operating points near the stability limit of the compressor with relatively large tip clearance of the rotor blades. The application of time-resolving sensors in both fixed and rotating frame of reference enables a detailed description of the circumferential structure and the spatial development of this unsteady flow phenomenon, which is limited to the blade tip region.Laser-Doppler-Anemometry (LDA) within the rotor blade passages and within the tip clearance as well as unsteady pressure measurements on the rotor blades show the structure of the blade tip vortex.It will be shown that the periodical interaction of the blade tip vortex of one blade with the flow at the adjacent blade is responsible for the generation of a rotating structure with high mode orders, termed as rotating instability (RI).Copyright © 2000 by ASME

275 citations


Book
24 Oct 2000
TL;DR: The RDA Code for Lateral Rotor Vibration analysis is described in this paper, where the authors present a detailed overview of the RDA Software Insights into Linear LRVs (SLRVs).
Abstract: Part I: Primer on Rotor Vibration Vibration Concepts and Methods One-Degree-of-Freedom Model Multi-DOF Models Modes, Excitation, and Stability of Multi-DOF Models Lateral Rotor Vibration Analysis Models Simple Linear Models Formulations for RDA Software Insights into Linear LRVs Nonlinear Effects in Rotor Dynamical Systems Torsional Rotor Vibration Analysis Models Rotor-Based Spinning Reference Frames Single Uncoupled Rotor Coupled Rotors Semidefinite Systems Part II: Rotor Dynamic Analyses RDA Code for Lateral Rotor Vibration Analyses Unbalance Steady-State Response Computations Instability Self-Excited-Vibration Threshold Computations Additional Sample Problems Bearing and Seal Rotor Dynamics Liquid-Lubricated Fluid-Film Journal Bearings Experiments to Measure Dynamic Coefficients Annular Seals Rolling Contact Bearings Squeeze-Film Dampers Magnetic Bearings Compliance Surface Foil Gas Bearings Turbo-Machinery Impeller and Blade Effects Centrifugal Pumps Centrifugal Compressors High-Pressure Steam Turbines and Gas Turbines Axial Flow Compressors Part III Monitoring and Diagnostics Rotor Vibration Measurement and Acquisition Introduction to Monitoring and Diagnostics Measured Vibration Signals and Associated Sensors Vibration Data Acquisition Signal Conditioning Vibration Severity Guidelines Casing and Bearing Cap Vibration Displacement Guidelines Standards, Guidelines, and Acceptance Criteria Shaft Displacement Criteria Signal Analysis and Identification of Vibration Causes Vibration Trending and Baselines FFT Spectrum Rotor Orbit Trajectories Bode, Polar, and Spectrum Cascade Plots Wavelet Analysis Tools Chaos Analysis Tools Symptoms and Identification of Vibration Causes Part IV Trouble-Shooting Case Studies Forced Vibration and Critical Speed Case Studies HP Steam Turbine Passage through First Critical Speed HP-IP Turbine Second Critical Speed through Power Cycling Boiler Feed Pumps: Critical Speeds at Operating Speed Nuclear Feed Water Pump Cyclic Thermal Rotor Bow Power Plant Boiler Circulating Pumps Nuclear Plant Cooling Tower Circulating Pump Resonance Generator Exciter Collector Shaft Critical Speeds Self-Excited Rotor Vibration Case Studies Swirl Brakes Cure Steam Whirl in a 1300 MW Unit Bearing Unloaded by Nozzle Forces Allows Steam Whirl Misalignment Causes Oil Whip/Steam Whirl "Duet" Additional Rotor Vibration Cases and Topics Vertical Rotor Machines Vector Turning from Synchronously Modulated Rubs Air Preheater Drive Structural Resonances Aircraft Auxiliary Power Unit Commutator Vibration-Caused Uneven Wear Impact Tests for Vibration Problem Diagnoses Bearing Looseness Effects Tilting-Pad versus Fixed-Surface Journal Bearings Base-Motion Excitations from Earthquake and Shock Parametric Excitation: Nonaxisymmetric Shaft Stiffness Rotor Balancing Index

223 citations


Journal ArticleDOI
TL;DR: In this article, the authors used the Compartment Model Approach (CMA) to develop a flow model based on the general knowledge of the hydrodynamics of both unaerated and aerated stirred vessels.

198 citations


Journal ArticleDOI
TL;DR: An application of the method of extremum seeking to the problem of maximizing the pressure rise in an axial-flow compressor and design a feedback scheme actuated through a bleed valve which simultaneously stabilizes rotating stall and surge and steers the system towards the equilibrium with maximal pressure.
Abstract: We show an application of the method of extremum seeking to the problem of maximizing the pressure rise in an axial-flow compressor. First we apply extremum seeking to the Moore-Greitzer model and design a feedback scheme actuated through a bleed valve which simultaneously stabilizes rotating stall and surge and steers the system towards the equilibrium with maximal pressure. Then we implement the scheme on a compressor rig in Murray's laboratory at the California Institute of Technology. We perform stabilization of rotating stall via air injection and implement extremum seeking through a slow bleed valve. The experiment demonstrates that extremum seeking ensures the maximization of the pressure rise starting on either side of the stall inception point. The experiment also resolves a concern that extremum seeking requires the use of periodic probing-the amplitude of probing needed to achieve convergence is far below the noise level of the compressor system (even outside rotating stall).

183 citations


Patent
Motoaki Utamura1
25 Aug 2000
TL;DR: In this paper, a gas turbine, a combined cycle plant and a compressor by which both augmentation of the power output and augmenting of the thermal efficiency can be realized by injecting liquid droplets into inlet air introduced into an entrance of a compressor with simple equipment which is suitable for practical use.
Abstract: A gas turbine, a combined cycle plant and compressor by which both augmentation of the power output and augmentation of the thermal efficiency can be realized by injecting liquid droplets into inlet air introduced into an entrance of a compressor with simple equipment which is suitable for practical use. The gas turbine includes a compressor for taking in and compressing gas, a combustor in which fuel is combusted with the gas discharged from the compressor, and a turbine driven by the combusted gas of the combustor. The gas turbine further includes a liquid droplet injection device provided on the upstream side of the compressor for injecting liquid droplets into inlet air to be supplied into the entrance of the compressor to lower the temperature of the inlet air to be introduced into the compressor so that the injected liquid droplets may be evaporated while flowing through the compressor.

167 citations


Journal ArticleDOI
TL;DR: In this article, a transonic axial compressor rotor with dis-crete injection is examined in a time-averaged Navier-Stokes CFD simulations and it is shown that tip injection increases stability by unloading the rotor tip and that increasing injection velocity improves the effectiveness of tip injection.
Abstract: Mass injection upstream of the tip of a high-speed axial compressor rotor is a stabilityenhancement approach known to be effective in suppressing stall in tip-critical rotors.This process is examined in a transonic axial compressor rotor through experiments andtime-averaged Navier-Stokes CFD simulations. Measurements and simulations for dis-crete injection are presented for a range of injection rates and distributions of injectorsaround the annulus. The simulations indicate that tip injection increases stability byunloading the rotor tip and that increasing injection velocity improves the effectiveness oftip injection. For the tested rotor, experimental results demonstrate that at 70 percentspeed the stalling flow coefficient can be reduced by 30 percent using an injected mass-flow equivalent to 1 percent of the annulus flow. At design speed, the stalling flow coef-ficient was reduced by 6 percent using an injected massflow equivalent to 2 percent of theannulus flow. The experiments show that stability enhancement is related to the mass-averaged axial velocity at the tip. For a given injected massflow, the mass-averaged axialvelocity at the tip is increased by injecting flow over discrete portions of the circumfer-ence as opposed to full-annular injection. The implications of these results on the designof recirculating casing treatments and other methods to enhance stability will bediscussed. @DOI: 10.1115/1.1330272#

157 citations


Journal ArticleDOI
TL;DR: In this paper, the authors summarized the state of 3D CFD-based models of the time average flow field within axial flow multistage turbomachines and provided the potential of providing credible results at both design and off-design operating conditions.
Abstract: This paper summarizes the state of 3D CFD based models of the time average flow field within axial flow multistage turbomachines. Emphasis is placed on models which are compatible with the industrial design environment and those models which offer the potential of providing credible results at both design and off-design operating conditions. The need to develop models which are free of aerodynamic input from semi-empirical design systems is stressed. The accuracy of such models is shown to be dependent upon their ability to account for the unsteady flow environment in multistage turbomachinery. The relevant flow physics associated with some of the unsteady flow processes present in axial flow multistage machinery are presented along with procedures which can be used to account for them in 3D CFD simulations. Sample results are presented for both axial flow compressors and axial flow turbines which help to illustrate the enhanced predictive capabilities afforded by including these procedures in 3D CFD simulations. Finally, suggestions are given for future work on the development of time average flow models.

144 citations


Journal ArticleDOI
TL;DR: In this paper, the results from the successful application of the particle imaging velocimetry (PIV) technique to both the blade passage region of a transonic axial compressor and the diffuser region of high speed centrifugal compressor are presented.
Abstract: Digital Particle Imaging Velocimetry (DPIV) is a powerful measurement technique, which can be used as an alternative or complementary approach to Laser Doppler Velocimetry (LDV) in a wide range of research applications. The instantaneous planar velocity measurements obtained with PIV make it an attractive technique for use in the study of the complex flow fields encountered in turbomachinery. The ability to acquire multiple measurement points of comparable accuracy to LDV results in reduced runtime and enables the study of both transient and steady state flow phenomena. Many of the same issues encountered in the application of LDV to rotating machinery apply in the application of PIV. Techniques for optical access, light sheet delivery, CCD camera technology and particulate seeding are discussed. Results from the successful application of the PIV technique to both the blade passage region of a transonic axial compressor and the diffuser region of a high speed centrifugal compressor are presented. Both instantaneous and time-averaged flow fields were obtained. The 95% confidence intervals for the velocity estimates were also determined.

104 citations


Journal ArticleDOI
TL;DR: In this article, a 3D Navier-Stokes CFD code was used to simulate the effects of turbine parameters on the tip leakage flow and vortex in a linear turbine cascade to understand the detailed flow physics.
Abstract: A pressure-correction based, 3D Navier-Stokes CFD code was used to simulate the effects of turbine parameters on the tip leakage flow and vortex in a linear turbine cascade to understand the detailed flow physics. A baseline case simulation of a cascade was first conducted in order to validate the numerical procedure with experimental measurements. The effects of realistic tip clearance spacing, inlet conditions, and relative endwall motion were then sequentially simulated, while maintaining previously modified parameters. With each additional simulation, a detailed comparison of the leakage flow's direction, pressure gradient, and mass flow, as well as the leakage vortex and its roll-up, size, losses, location, and interaction with other flow features, was conducted. Part I of this two-part paper focuses on the effect of reduced tip clearance height on the leakage flow and vortex. Reduced tip clearance results in less mass flow through the gap, a smaller leakage vortex, and less aerothermal losses in both the gap and the vortex. The shearing of the leakage jet and passage flow to which leakage vortex roll-up is usually attributed to is not observed in any of the simulations. Alternative explanations of the leakage vortex's roll-up are presented. Additional secondary flows that are seen near the casing are also discussed.

90 citations


Proceedings ArticleDOI
Masahiro Inoue1, Motoo Kuroumaru1, T. Tanino1, S. Yoshida1, Masato Furukawa1 
TL;DR: In this paper, a low-speed compressor test rig at Kyushu University, multiple short-length-scale stall cells appeared under a mild stall condition and turned into a long length-scale cell under a deep stall condition.
Abstract: In a low-speed compressor test rig at Kyushu University, multiple short length-scale stall cells appeared under a mild stall condition and turned into a long length-scale cell under a deep stall condition. Then, for the both types of stall cell, the pressure distribution on the casing wall and the velocity distributions upstream and downstream of the rotor have been measured by high response pressure transducers and a slanted hot-wire, respectively. The time-dependent ensemble averages of these distributions have been obtained phase-locking to both of the rotor and the stall cell rotation by using a so-called ‘double phase-locked averaging technique’ developed by the authors.Structure of the two stall cells are compared with each other: The short length-scale stall cell is characterized by a concentrated vortex spanning from the casing wall ahead of the rotor to the blade suction surface. In the long length-scale stall cell, the separation vortices go upstream irregularly when blade separation develops in the front half of the cell, and reenter the rotor on the hub side in the rear half of it.The unsteady aerodynamic force and torsional moment acting on the blade tip section have been evaluated from the time-dependent ensemble averages of the casing wall pressure distribution. The force fluctuation due to the short length-scale cells is somewhat smaller than that for the long length-scale cell. The blade suffers two peaks of the force during a period of the short length-scale cells passing through it. The moment fluctuation for the short length-scale cells is considerably larger than that for the long length-scale cell.© 2000 ASME

88 citations


Patent
30 May 2000
TL;DR: In this paper, an integrated gas turbine and air separation process and system having an air separation unit integrated with a gas turbine-driven air compression system which operates using fuel as the primary energy source is presented.
Abstract: An integrated gas turbine and air separation process and system having an air separation unit integrated with a gas turbine-driven air compression system which operates using fuel as the primary energy source. Feed air for the air separation unit is provided by two separate compressors driven by the gas turbine expander wherein one compressor provides air to the air separation unit and to the gas turbine combustor, and the other compressor provides feed air to the air separation unit. The ability to control an integrated air separation/gas turbine process during off-design or turndown conditions is improved by the use of two air compressors in the present invention compared with the usual single compressor gas turbine system. In the design of the integrated gas turbine and air separation system, the power requirement for a given air compression duty can be matched more readily to the power output of an available expansion turbine when two air compressors are used rather than a single air compressor.

Journal ArticleDOI
TL;DR: The paper describes an advanced 3D blading concept for highly-loaded transonic compressor stators that takes advantage of the aerodynamic effects of sweep and dihedral and makes a contribution to the understanding of the endwall effect of both features with special emphasis put on sweep.
Abstract: The paper describes an advanced three-dimensional blading concept for highly loaded transonic compressor stators. The concept takes advantage of the aerodynamic effects of sweep and dihedral. To the knowledge of the authors this is the first approach reported in the open literature that combines those two basic types of lean in an engine-worthy aerofoil design. The paper makes a contribution to the understanding of the endwall effect of both features with special emphasis put on sweep. The advanced three-dimensional blading concept was applied to an Engine Section Stator (ESS) of an aero-engine fan. In order to demonstrate how three-dimensional flow can be controlled, numerical analysis of the flow structure in a conventional and an advanced stator configuration was performed using a three-dimensional Navier-Stokes solver. The numerical analysis showed the advanced blade improving both radial loading distribution and the three-dimensional endwall boundary layer development. In particular, a strong hub corner stall could be largely alleviated. High-speed rig testing of the advanced ESS confirmed the concept and showed good qualitative agreement between measurement and prediction. The work presented was closely linked to the development of the BR710 engine on which the advanced ESS is in service today.

Journal ArticleDOI
TL;DR: In this paper, the agitation of granular materials was studied in a horizontal cylindrical shell stirred by a single long flat blade located on radial arms fixed to a rotor shaft.
Abstract: Studies on the agitation of granular materials were conducted in a horizontal cylindrical shell stirred by a single long flat blade located on radial arms fixed to a rotor shaft. Positron emission particle tracking, a noninvasive method of investigating opaque systems, permitted the motion of a single particle to be followed. Axial flow patterns showed two loops of circulation inside each compartment defined by the radial arms of the rotating blades. Results revealed the presence at 20% of fill of a circulation zone in the cross-sectional plane directly beneath the rotating shaft where little agitation occurred. This zone decreased in size and moved toward the agitator shaft as fill increased from 20% to 60%. Velocity profiles and Fourier analysis of particle displacement showed that particle movement was controlled by the number of blade passes. Torque measurements on the agitator shaft were correlated with distribution of material in the cross section of the mixer and distribution of tangential velocity. This opens the prospect of relating torque to powder flow patterns. The information can now be incorporated into models for heat transfer, chemical reaction, or agglomeration.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effects of the tip clearance flow in an axial turbine rotor, including the distribution and the development of the pressure, the loss, the velocity, and the turbulence fields.
Abstract: This paper presents an experimental investigation of the effects of the tip clearance flow in an axial turbine rotor. The effects investigated include the distribution and the development of the pressure, the loss, the velocity, and the turbulence fields. These flow fields were measured using the techniques of static pressure taps, rapid response pressure probes, rotating five-hole probes, and Laser Doppler Velocimeter. Part I of this paper covers the loss development through the passage, and the pressure distribution within the passage, on the blade surfaces, on the blade tip, and on the casing wall. Regions with both the lowest pressure and the highest loss indicate the inception and the trace of the tip leakage vortex. The suction effect of the vortex slightly increases the blade loading near the tip clearance region. The relative motion between the turbine blades and the casing wall results in a complicated pressure field in the tip region. The fluid near the casing wall experiences a considerable pressure difference across the tip. The highest total pressure drop and the highest total pressure loss were both observed in the region of the tip leakage vortex, where the loss is nearly twice as high as that near the passage vortex region. However, the passage vortex produces more losses than the tip leakage vortex in total. The development of the loss in turbine rotor is similar to that observed in cascades. Part II of this paper covers the velocity and the turbulence fields.Copyright © 2000 by ASME

Proceedings ArticleDOI
08 May 2000
TL;DR: In this article, the authors investigated the effect of the breakdown of the tip leakage vortex in an axial compressor rotor at near-stall conditions and showed that the vortex breakdown causes significant changes in the nature of the leakage vortex, which result in the anomalous phenomena in the time-averaged flow fields near the tip at the nearstall conditions: no rolling-up of the leaky vortex downstream of the rotor, disappearance of the casing wall pressure trough corresponding to the leakage, large spread of the low-energy fluid accumulating on the pressure side, and large pressure fluctuation on
Abstract: The unsteady flow nature caused by the breakdown of the tip leakage vortex in an axial compressor rotor at near-stall conditions has been investigated by unsteady three-dimensional Navier-Stokes flow simulations. The simulations show that the spiral-type breakdown of the tip leakage vortex occurs inside the rotor passage at the near-stall conditions. Downstream of the breakdown onset, the tip leakage vortex twists and turns violently with time, thus interacting with the pressure surface of the adjacent blade. The motion of the vortex and its interaction with the pressure surface are cyclic. The vortex breakdown causes significant changes in the nature of the tip leakage vortex, which result in the anomalous phenomena in the time-averaged flow fields near the tip at the near-stall conditions: no rolling-up of the leakage vortex downstream of the rotor, disappearance of the casing wall pressure trough corresponding to the leakage vortex, large spread of the low-energy fluid accumulating on the pressure side, and large pressure fluctuation on the pressure side. As the flow rate is decreased, the movement of the tip leakage vortex due to its breakdown becomes so large that the leakage vortex interacts with the suction surface as well as the pressure one. The interaction with the suction surface gives rise to the three-dimensional separation of the suction surface boundary layer.© 2000 ASME

Journal ArticleDOI
TL;DR: In this paper, an analytical solution for the kinematic and stress variations across the radial gap of a concentric annular flow in fully developed conditions is given, where the ratio of pressure drop to flow rate drop is found to be a complex mathematical function of the radial position of zero shear stress and this, in turn, depends weakly on the elasticity.
Abstract: An analytical solution is given for the kinematic and stress variations across the radial gap of a concentric annular flow in fully developed conditions. The fluid is viscoelastic and obeys the non-linear rheological constitutive equation proposed by Phan-Thien and Tanner [1]. This constitutive model simulates well the material functions of many polymer melts and solutions and therefore, the present results are useful in a number of practical situations. The ratio of pressure drop to flow rate drop is found to be a complex mathematical function of the radial position of zero shear stress and this, in turn, depends weakly on the elasticity, based on the product of an elongational parameter by a Deborah number defined with an averaged velocity. There is thus a non-linear coupling which could not be solved in an explicit way for the inverse problem of an imposed flow rate, but an iterative procedure gives a ready result. For the direct problem of a given pressure drop the present results represent an exact explicit solution to the axial annular flow problem. Representative profiles of the solution are given and discussed. It is found that, for a given flow rate, the pressure drop scaled with the corresponding Newtonian value is independent of the diameter ratio. © 2000 Elsevier Science B.V. All rights reserved.

Proceedings ArticleDOI
TL;DR: In this paper, the authors describe the development and testing of a strategy to turn the fluid leaking over shrouded turbine rotor blade rows with the aim of reducing the aerodynamic losses associated with its re-injection into the mainstream flow.
Abstract: The losses generated by fluid leaking across the shrouds of turbine blade rows are known to form a significant proportion of the overall loss generated in low aspect ratio turbines. The use of shrouds to encase the tips of turbine blades has encouraged the development of many innovative sealing arrangements, all of which are intended to reduce the quantity of fluid (the leakage fraction) leaking across the shroud. Modern sealing arrangements have reduced leakage fractions considerably, meaning that further improvements can only be obtained by controlling the leakage flow in such a way so as to minimise the aerodynamic losses incurred by the extraction and re-injection of the leakage flow into the mainstream. There are few published experimental investigations on the interaction between mainstream and leakage flows to provide guidance on the best means of managing the leakage flows to do this. This paper describes the development and testing of a strategy to turn the fluid leaking over shrouded turbine rotor blade rows with the aim of reducing the aerodynamic losses associated with its re-injection into the mainstream flow. The intent was to extract work from the leakage flow in the process. A four stage research turbine was used to test in detail the sealing design resulting from this strategy. A reduction in brake efficiency of 3.5% was measured. Further investigation suggested that much of the increase in loss could be attributed to the presence of axial gaps upstream and downstream of the shroud cavity which facilitated the periodic ingress and egress of mainstream fluid into the shroud cavity under the influence of the rotor potential field. This process was exacerbated by reductions in the leakage fraction.Copyright © 2000 by ASME

Journal ArticleDOI
TL;DR: In this paper, a 3D Navier-Stokes CFD code was used to simulate the effects of turbine parameters on the tip leakage flow and vortex in a linear turbine cascade to understand the detailed flow physics.
Abstract: A pressure-correction based, 3D Navier-Stokes CFD code was used to simulate the effects of turbine parameters on the tip leakage flow and vortex in a linear turbine cascade to understand the detailed flow physics. A baseline case simulation of a cascade was first conducted in order to validate the numerical procedure with experimental measurements. The effects of realistic tip clearance spacing, inlet conditions, and relative endwall motion were then sequentially simulated, while maintaining previously modified parameters. With each additional simulation, a detailed comparison of the leakage flow's direction, pressure gradient, and mass flow, as well as the leakage vortex and its roll-up, size, losses, location, and interaction with other flow features, was conducted. Part II of this two-part paper series focuses on the effect of relative motion of the outer casing on the leakage flow and vortex development. Casing relative motion results in less mass flow through the gap and a smaller leakage vortex. The structure of the aerothermal losses in the passage change dramatically when the outer casing motion was incorporated, but the total losses in the passage remained very similar, Additional secondary flows that are seen near the casing are also discussed.

Journal ArticleDOI
TL;DR: In this article, a two-fluid Taylor Couette flow with countercurrent axial flow with axial dispersion was investigated and the mass transfer coefficient was found to be proportional to the strength of Taylor vortices.
Abstract: Flow instabilities occurring in rotating flows can be exploited as a new approach to liquid-liquid extraction. Two immiscible liquids are radially stratified by centrifugal force in the annulus between corotating coaxial cylinders. When the inner cylinder is rotated above a critical speed, Taylor vortices form in one or both of the fluids. Although the flow pattern yields a relatively small amount of interfacial surface area, the surface is highly active for interphase mass transfer due to the local vortex motion. By adding countercurrent axial flow, efficient continuous processing is also possible. This flow yields a viable extraction process, particularly for fluid pairs that are easily emulsifiable and therefore have limited processing options with the current equipment commercially available. This article demonstrates that two-fluid Taylor-Couette flow with countercurrent axial flow is achievable in practice and explores, experimentally and computationally, the mass-transfer characteristics of the flow. Experimentally, when the vortices first appear, axial dispersion decreases and the interphase mass transfer starts to increase. Upon further increase in differential rotation rate, the extraction performance continues to improve, with the mass-transfer coefficient proportional to the strength of Taylor vortices. This suggests that very high extraction efficiencies can be obtained with even larger relative rotation rates. Furthermore, mass-transfer boundary-layer theory, in combination with computational fluid dynamics, provides a reliable method for predicting the extraction performance.

Journal ArticleDOI
TL;DR: In this paper, the influence of inlet flow conditions on the pressure recovery and operating range of radial diffusers for centrifugal compressor stages has been investigated and the effect of different averaging methods for the inlet total pressure distributions, which are needed in the definition of diffuser pressure recovery coefficient for nonuniform diffuser inlet conditions, were also assessed.
Abstract: This is Part 1 of a two-part paper considering the performance of radial diffusers for use in a high-performance centrifugal compressor. Part 1 reports on discrete-passage diffusers (shown in Fig. 1) while Part 2 describes a test of a straight-channel diffuser designed for equivalent duty. Two builds of discrete-passage diffuser were tested, with 30 and 38 separate passages. Both the 30 and 38 passage diffusers investigated showed comparable range of unstalled operation and similar level of overall diffuser pressure recovery. The paper concentrates on the influence of inlet flow conditions on the pressure recovery and operating range of radial diffusers for centrifugal compressor stages. The flow conditions examined include diffuser inlet Mach number, flow angle, blockage, and axial flow nonuniformity. The investigation was carried out in a specially built test facility, designed to provide a controlled inlet flow field to the test diffusers. The facility can provide a wide range of diffuser inlet velocity profile distortion and skew with Mach numbers up to unity and flow angles of 63 to 75 deg from the radial direction. The consequences of different averaging methods for the inlet total pressure distributions, which are needed in the definition of diffuser pressure recovery coefficient for nonuniform diffuser inlet conditions, were also assessed. The overall diffuser pressure recovery coefficient, based on suitably averaged inlet total pressure, was found to correlate well with the momentum-averaged flow angle into the diffuser. Furthermore, the pressure recovery coefficient was found to be essentially independent of the axial distortion at diffuser inlet, and the Mach number, over the wide flow range (from maximum flow to the beginning of flow instabilities) investigated. It is thus shown that the generally accepted sensitivity of diffuser pressure recovery performance to inlet flow distortion and boundary layer blockage can be largely attributed to inappropriate quantification of the average dynamic pressure at diffuser inlet. Use of an inlet dynamic pressure based on availability or mass-averaging in combination with definition of inlet flow angle based on mass average of the radial and tangential velocity at diffuser inlet removes this sensitivity.

Journal ArticleDOI
TL;DR: In this article, numerical optimization techniques combined with a three-dimensional thin-layer NavierStokes solver are presented to find an optimum shape of a stator blade in an axial compressor through calculations of single stage rotor-stator flow.
Abstract: Numerical optimization techniques combined with a three-dimensional thin-layer NavierStokes solver are presented to find an optimum shape of a stator blade in an axial compressor through calculations of single stage rotor-stator flow, Governing differential equations are discretized using an explicit finite difference method and solved by a multi-stage Runge-Kutta scheme. Baldwin-Lomax model is chosen to describe turbulence. A spatially-varying time-step and an implicit residual smoothing are used to accelerate convergence. A steady mixing approach is used to pass information between stator and rotor blades. For numerical optimization, searching direction is found by the steepest decent and conjugate direction methods, and the golden section method is used to determine optimum moving distance along the searching direction. The object of present optimization is to maximize efficiency. An optimum stacking line is found to design a custom-tailored 3-dimensional blade for maximum efficiency with the other parameters fixed.

Proceedings ArticleDOI
08 May 2000
TL;DR: In this paper, the authors present the experimental and computational results from an investigation of the endwall cavity and gaspath flow interaction in a low-pressure turbine and compare the results with test data.
Abstract: Axial flow turbine designers are currently using Navier-Stokes flow solvers to reveal the details of the three dimensional flowfield inside individual bladerow passages. This new capability has allowed designers to focus on secondary flow reduction to improve turbine efficiency. These steady bladerow solvers include viscous and film cooling effects and show good agreement with test measurements in the midspan region. However, the difference between computational results and data at the endwalls is significant due to the exclusion of endwall cavity effects. A clear understanding of how the flow entering and exiting the cavity interacts with the gaspath aerodynamics, in conjunction with an accurate computational model, are needed to predict accurately the secondary flow patterns and endwall losses. This investigation confirms that endwall cavity flows have a significant influence on gaspath aerodynamics and that they need to be included in bladerow computations for accurate results.Part I presents the experimental and computational results from an investigation of the endwall cavity and gaspath flow interaction in a low pressure turbine. Detailed test measurements were obtained in a low speed research turbine using state of the art geometry and served as a benchmark for the computational model. Hot wire and total pressure measurements were taken at multiple planes between bladerows to establish the interaction between the hub cavity and gaspath flows. Ethylene tracer gas was also applied to evaluate secondary flow characteristics of the stator and the migration of the cavity flow through the downstream rotor.Steady and unsteady computational analyses were utilized to model different combinations of the cavity and bladerow geometries. This building block approached allowed for separation of the flow physics involved in the interaction and identified the geometry and flow features that were critical to producing the best agreement with test data.In Part II, the development of a source term model for a steady bladerow solver that simulates endwall cavity flows in a low pressure turbine is reviewed. The source term model adequately captured endwall cavity effects and accurately predicted secondary flow in the adjacent bladerow. This source term model gives designers the capability to investigate new ideas of reducing secondary flow in a timely manner, leading to improvements in overall turbine efficiency.Copyright © 2000 by ASME

Journal ArticleDOI
Li He1
01 Feb 2000
TL;DR: In this paper, a three-dimensional full Navier-Stokes method is developed and applied to calculations of unsteady flows through multiple blade rows in axial-flow turbomachinery.
Abstract: A three-dimensional full Navier-Stokes method is developed and applied to calculations of unsteady flows through multiple blade rows in axial-flow turbomachinery. The solver adopts the cellcentred finite volume discretization and the four-stage Runge-Kutta time-marching scheme. Unsteady calculations are effectively accelerated by using a time-consistent multi-grid technique, resulting in a speed-up by a factor of 10–20 with adequate temporal accuracy. The computational efficiency and validity of the present multi-grid technique are illustrated by comparisons with the results of the conventional dual time-stepping scheme. Calculated unsteady pressures on blade surfaces for a turbine stage performances at different stator-rotor axial gaps reveals a marked three-dimensional behaviour of the interaction between incoming wakes and rotor passage-vortex structures. The time-averaged losses from unsteady calculations show a noticeable spanwise redistribution compared with the steady results. Two dimension...

Journal ArticleDOI
TL;DR: In this paper, the straight-channel diffuser was compared with the discrete-passage diffuser in terms of inlet Mach number, flow angle, blockage, and axial flow nonuniformity.
Abstract: This is Part 2 of an examination of the influence of inlet flow conditions on the performance and operating range of centrifugal compressor vaned diffusers. The paper describes tests of a straight-channel type diffuser, sometimes called a wedge-vane diffuser, and compares the results with those from the discrete-passage diffusers described in Part 1. Effects of diffuser inlet Mach number, flow angle, blockage, and axial flow nonuniformity on diffuser pressure recovery and operating range are addressed. The straight-channel diffuser investigated has 30 vanes and was designed for the same aerodynamic duty as the discrete-passage diffuser described in Part 1. The ranges of the overall pressure recovery coefficients were 0.50-0.78 for the straight-channel diffuser and 0.50-0.70 for the discrete-passage diffuser, except when the diffuser was choked. In other words, the maximum pressure recovery of the straight-channel diffuser was found to be roughly 10 percent higher than that of the discrete-passage diffuser investigated. The two types of diffuser showed similar behavior regarding the dependence of pressure recovery on diffuser inlet flow angle and the insensitivity of the performance to inlet flow field axial distortion and Mach number. The operating range of the straight-channel diffuser, as for the discrete-passage diffusers, was limited by the onset of rotating stall at a fixed momentum-averaged flow angle into the diffuser, which was for the straight-channel diffuser, α crit = 70 ± 0.5 deg. The background, nomenclature, and description of the facility and method are all given in Part 1.

Journal ArticleDOI
TL;DR: In this paper, the results from the successful application of the particle imaging velocimetry (PIV) technique to both the blade passage region of a transonic axial compressor and the diffuser region of high speed centrifugal compressor are presented.
Abstract: Digital particle imaging velocimetry (DPIV) is a powerful measurement technique, which can be used as an alternative or complementary approach to laser doppler velocimetry (LDV) in a wide range of research applications. The instantaneous planar velocity measurements obtained with PIV make it an attractive technique for use in the study of the complex flow fields encountered in turbomachinery. The planar nature of the technique also significantly reduces the facility run time over point-based techniques. Techniques for optical access, light sheet delivery, CCD camera technology and particulate seeding are discussed. Results from the successful application of the PIV technique to both the blade passage region of a transonic axial compressor and the diffuser region of a high speed centrifugal compressor are presented. Both instantaneous and time-averaged flow fields were obtained. The averaged flow field measurements are used to estimate the flow turbulence intensity. The instantaneous velocity vector maps obtained during compressor surge provide previously unobtainable insight into the complex flow field characteristics occurring during short lived surge events. These flow field maps illustrate the true power of the DPIV technique.


Patent
01 Nov 2000
TL;DR: In this paper, a combined water-wash and wet-compression system for a gas turbine includes a compressor having an inlet defining a flow direction; and a plurality of manifolds arranged in proximity to the inlet and arranged transversely of the flow direction.
Abstract: A combined water-wash and wet-compression system for a gas turbine includes a compressor having an inlet defining a flow direction; and a plurality of manifolds arranged in proximity to the inlet and arranged transversely of the flow direction; a plurality of dual-function nozzles connected to the manifolds. Each dual-function nozzle is adapted to supply, selectively, either relatively small droplets for introduction into the compressor for intercooling, or relatively large droplets for impingement on components of the compressor for cleaning the components. A method of introducing a liquid into a compressor inlet for providing water wash for cleaning components of the compressor, and for providing wet compression for intercooling is also disclosed.

Journal ArticleDOI
TL;DR: In this article, an algorithm was developed to identify instability waves within the Tollmien-Schlichting (T-S) frequency range, combined with a turbulent intermittency detection routine to produce space-time diagrams showing the probability of instability wave occurrence prior to regions of turbulent flow.
Abstract: Data from a surface hot-film array on the outlet stator of a 1.5-stage axial compressor are analyzed to look for direct evidence of natural transition phenomena, An algorithm is developed to identify instability waves within the Tollmien-Schlichting (T-S) frequency range. The algorithm is combined with a turbulent intermittency detection routine to produce space-time diagrams showing the probability of instability wave occurrence prior to regions of turbulent flow. The paper compares these plots for a range of blade loading, with free-stream conditions corresponding to the maximum and minimum inflow disturbance periodicity produced by inlet guide vane clocking. Extensive regions of amplifying instability waves are identified in nearly all cases. The implications for transition prediction in decelerating flow regions on axial turbomachine blades are discussed.

Journal ArticleDOI
TL;DR: In this paper, the stator hub and blade flow in two different stators of a highly loaded single-stage axial-flow low-speed compressor were investigated, and the experimental results showed that stator K exhibits a much better hub performance than stator A.
Abstract: The paper describes an experimental investigation of the stator hub and blade flow in two different stators of a highly loaded single-stage axial-flow low-speed compressor. The first stator (A) is a conventional design with blades of rectangular planform. The second stator (K) is an unconventional, more advanced design with blades of a special planform, characterized by an aft-swept leading edge with increasing sweep angle towards hub and casing. The experimental results show that stator K exhibits a much better hub performance than stator A, finally leading to a better overall performance of stage K compared to stage A. The better hub performance of stator K is, primarily, the result of a planform effect of the newly introduced blades with an aft-swept leading edge and the aerodynamics of an aft-swept wing.Copyright © 2000 by ASME

Proceedings ArticleDOI
08 May 2000
TL;DR: In this article, an axisymmetric through-flow code coupled with a quasi-three-dimensional cascade plane code with inverse design capability was proposed to increase the pressure ratio of axial compressor stages by controlling the development of blade and endwall boundary layers.
Abstract: The pressure ratio of axial compressor stages can be significantly increased by controlling the development of blade and endwall boundary layers in regions of adverse pressure gradient by means of boundary layer suction. This concept is validated and demonstrated through the design and analysis of a unique aspirated compressor stage which achieves a total pressure ratio of 3.5 at a tip speed of 1500 ft/s. The aspirated stage was designed using an axisymmetric through-flow code coupled with a quasi three-dimensional cascade plane code with inverse design capability. Validation of the completed design was carried out with three-dimensional Navier-Stokes calculations. Spanwise slots were used on the rotor and stator suction surfaces to bleed the boundary layer with a total suction requirement of 4% of the inlet mass flow. Additional bleed of 3% was also required on the hub and shroud near shock impingement locations. A three-dimensional viscous evaluation of the design showed good agreement with the quasi three-dimensional design intent, except in the endwall regions. The three-dimensional viscous analysis predicted a mass averaged total pressure ratio of 3.7 at an isentropic efficiency of 93% for the rotor, and a mass averaged total pressure ratio of 3.4 at an isentropic efficiency of 86% for the stage.Copyright © 2000 by ASME