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Showing papers on "Axial compressor published in 2005"


Journal ArticleDOI
TL;DR: In this paper, a computational study to define the phenomena that lead to the onset of short length-scale (spike) rotating stall disturbances has been carried out based on unsteady simulations.
Abstract: A computational study to define the phenomena that lead to the onset of short length-scale (spike) rotating stall disturbances has been carried out. Based on unsteady simulations, we hypothesize there are two conditions necessary for the formation of spike disturbances, both of which are linked to the tip clearance flow. One is that the interface between the tip clearance and oncoming flows becomes parallel to the leading-edge plane. The second is the initiation of backflow, stemming from the fluid in adjacent passages, at the trailing-edge plane. The two criteria also imply a circumferential length scale for spike disturbances. The hypothesis and scenario developed are consistent with numerical simulations and experimental observations of axial compressor stall inception. A comparison of calculations for multiple blades with those for single passages also allows statements to be made about the utility of single passage computations as a descriptor of compressor stall.

393 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe a novel way of prescribing computational fluid dynamics (CFD) boundary conditions for axial-flow compressors based on extending the standard single passage computational domain by adding an intake upstream and a variable nozzle downstream.
Abstract: This paper describes a novel way of prescribing computational fluid dynamics (CFD) boundary conditions for axial-flow compressors. The approach is based on extending the standard single passage computational domain by adding an intake upstream and a variable nozzle downstream. Such a route allows us to consider any point on a given speed characteristic by simply modifying the nozzle area, the actual boundary conditions being set to atmospheric ones in all cases. Using a fan blade, it is shown that the method not only allows going past the stall point but also captures the typical hysteresis loop behavior of compressors.

85 citations


Journal ArticleDOI
TL;DR: In this paper, an advanced version of a three-equation eddy-viscosity model is proposed to resolve boundary layer transition in both steady and unsteady compressor aerosimulations.
Abstract: Recent experimental work has documented the importance of wake passing on the behavior of transitional boundary layers on the suction surface of axial compressor blades. This paper documents computational fluid dynamics (CFD) simulations using a commercially available general-purpose CFD solver, performed on a representative case with unsteady transitional behavior. The study implements an advanced version of a three-equation eddy-viscosity model previously developed and documented by the authors, which is capable of resolving boundary layer transition. It is applied to the test cases of steady and unsteady boundary layer transition on a two-dimensional flat plate geometry with a freestream velocity distribution representative of the suction side of a compressor airfoil. The CFD results are analyzed and compared to a similar experimental test case from the open literature. Results with the model show a dramatic improvement over more typical Reynolds-averaged Navier-Stokes (RANS)-based modeling approaches, and highlight the importance of resolving transition in both steady and unsteady compressor aerosimulations.

82 citations


Proceedings ArticleDOI
TL;DR: In this article, the axial compressor of a General Electric J85-13 jet engine was degraded by spraying atomized droplets of saltwater into the engine intake, and the results of laboratory analysis of the salt deposits are presented, providing insight into the increased surface roughness and the deposit thickness and distribution.
Abstract: Gas turbine performance deterioration can be a major economic factor. An example is within offshore installations where a degradation of gas turbine performance can mean a reduction of oil and gas production. This paper describes the test results from a series of accelerated deterioration tests on a General Electric J85-13 jet engine. The axial compressor was deteriorated by spraying atomized droplets of saltwater into the engine intake. The paper presents the overall engine performance deterioration as well as deteriorated stage characteristics. The results of laboratory analysis of the salt deposits are presented, providing insight into the increased surface roughness and the deposit thickness and distribution. The test data show good agreement with published stage characteristics and give valuable information regarding stage-by-stage performance deterioration.

76 citations


Journal ArticleDOI
TL;DR: In this paper, the aerodynamic characteristics of full and partial-length squealer rims in a turbine stage were investigated separately on the pressure side and on the suction side in the Axial Flow Turbine Research Facility (AFTRF) of the Pennsylvania State University.
Abstract: This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the Axial Flow Turbine Research Facility (AFTRF) of the Pennsylvania State University. The streamwise length of these partial squealer tips and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new channel arrangement diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of partial squealer rims in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers are aerodynamically superior to the pressure side squealers and the channel arrangement. The suction side partial squealers are capable of reducing the stage exit total pressure defect associated with the tip leakage flow to a significant degree.

76 citations


Journal ArticleDOI
TL;DR: In this paper, a rectangular channel containing a cylindrical rod has been simulated numerically by solving the unsteady Reynolds-averaged Navier-Stokes equations with a Reynolds stress model.
Abstract: Axial flow in a rectangular channel containing a cylindrical rod has been simulated numerically by solving the unsteady Reynolds-averaged Navier-Stokes equations with a Reynolds stress model. The study further documents the formation of quasi-periodic coherent structures in the form of vortex pairs and the important role that they play in transporting fluid across the gap region.

70 citations


Journal ArticleDOI
TL;DR: In this article, the authors performed numerical analysis of a waterjet propulsion system to provide detail understanding of complicated three-dimensional viscous flow phenomena including interactions of intake duct, rotor, stator, and contracted discharge nozzle.

64 citations


Patent
29 Mar 2005
TL;DR: In this article, a system and method for actively controlling compressor clearances in a turbine engine by passing a thermal fluid in heat exchanging relation through a compressor vane carrier is described.
Abstract: Aspects of the invention relate to a system and method for actively controlling compressor clearances in a turbine engine by passing a thermal fluid in heat exchanging relation through a compressor vane carrier. During some operational conditions, such as hot restart or spin cool, it may be desirable to heat the vane carrier to enlarge or at least prevent a decrease in compressor clearances. In such cases, a heated thermal fluid can be provided by reclaiming residual exhaust energy from a heat recovery steam generator. At any condition where improved performance is desired, such as at base load operation, the vane carrier can be cooled to minimize compressor clearances. A cooled thermal fluid can be bleed air from an upstream portion of the compressor, water-cooled high pressure bleed air from a downstream portion of the compressor, or feed water from the bottoming cycle in a combined cycle engine.

54 citations


Journal ArticleDOI
TL;DR: This study examines the influence of the diffuser on the overall LEV-VAD performance and concludes that the acceptable results of the computational simulations and experimental testing encourage final prototype manufacturing for acute and chronic animal studies.
Abstract: Thousands of adult cardiac failure patients may benefit from the availability of an effective, long-term ventricular assist device (VAD). We have developed a fully implantable, axial flow VAD (LEV-VAD) with a magnetically levitated impeller as a viable option for these patients. This pump's streamlined and unobstructed blood flow path provides its unique design and facilitates continuous washing of all surfaces contacting blood. One internal fluid contacting region, the diffuser, is extremely important to the pump's ability to produce adequate pressure but is challenging to manufacture, depending on the complex blade geometries. This study examines the influence of the diffuser on the overall LEV-VAD performance. A combination of theoretical analyses, computational fluid (CFD) simulations, and experimental testing was performed for three different diffuser models: six-bladed, three-bladed, and no-blade configuration. The diffuser configurations were computationally and experimentally investigated for flow rates of 2-10 L/min at rotational speeds of 5000-8000 rpm. For these operating conditions, CFD simulations predicted the LEV-VAD to deliver physiologic pressures with hydraulic efficiencies of 15-32%. These numerical performance results generally agreed within 10% of the experimental measurements over the entire range of rotational speeds tested. Maximum scalar stress levels were estimated to be 450 Pa for 6 L/min at 8000 rpm along the blade tip surface of the impeller. Streakline analysis demonstrated maximum fluid residence times of 200 ms with a majority of particles exiting the pump in 80 ms. Axial fluid forces remained well within counter force generation capabilities of the magnetic suspension design. The no-bladed configuration generated an unacceptable hydraulic performance. The six-diffuser-blade model produced a flow rate of 6 L/min against 100 mm Hg for 6000 rpm rotational speed, while the three-diffuser-blade model produced the same flow rate and pressure rise for a rotational speed of 6500 rpm. The three-bladed diffuser configuration was selected over the six-bladed, requiring only an incremental adjustment in revolution per minute to compensate for and ease manufacturing constraints. The acceptable results of the computational simulations and experimental testing encourage final prototype manufacturing for acute and chronic animal studies.

51 citations


Journal ArticleDOI
TL;DR: In this article, a state-variable model was developed for the analysis of fluid-induced vibration of composite pipeline systems, including simply supported, clamped and clamped-simply supported pipelines.

47 citations


Journal ArticleDOI
01 Dec 2005
TL;DR: In this paper, the shape optimization of a stator blade in a single-stage transonic axial compressor is described, and the blade optimization has been performed using response surface method and three-dimensional Navier-Stokes analysis.
Abstract: This article describes the shape optimization of a stator blade in a single-stage transonic axial compressor. The blade optimization has been performed using response surface method and three-dimensional Navier - Stokes analysis. Thin-layer approximation is introduced to the Navier - Stokes equations, and an explicit Runge - Kutta scheme is used to solve the gov- erning equations. Two geometric design variables of the stator blade, which are used to define a stacking line, are introduced to increase an adiabatic efficiency. D-optimal design is employed to reduce the number of evaluation points for response surface. With the optimization of the stator blade, the adiabatic efficiency is successfully improved when compared with that of the reference shape of the stator with straight stacking line. Positive stacking line, which bends on blade pressure side, effectively suppresses the flow separation on the blade suction surface of the stator.

Journal ArticleDOI
TL;DR: In this article, a water injection scroll compressor is used to supply clean compressed air to an automotive fuel cell system, where the water is used as both the lubricant and coolant in the compressor.

Journal ArticleDOI
TL;DR: In this article, the first known 3D digital particle image velocimetry (DPIV) measurements of the tip region of a low speed compressor rotor have been acquired to characterize the behavior of the rotor tip clearance flow.
Abstract: The accurate characterization and simulation of rotor tip clearance flows has received much attention in recent years due to their impact on compressor performance and stability. At NASA Glenn the first known three dimensional digital particle image velocimetry (DPIV) measurements of the tip region of a low speed compressor rotor have been acquired to characterize the behavior of the rotor tip clearance flow. The measurements were acquired phase-locked to the rotor position so that changes in the tip clearance vortex position relative to the rotor blade can be seen. The DPIV technique allows the magnitude and relative contributions of both the asynchronous motions of a coherent structure and the temporal unsteadiness to be evaluated. Comparison of measurements taken at the peak efficiency and at near stall operating conditions characterizes the mean position of the clearance vortex and the changes in the unsteady behavior of the vortex with blade loading. Comparisons of the 3-D DPIV measurements at the compressor design point to a 3D steady N-S solution are also done to assess the fidelity of steady, single-passage simulations to model an unsteady flow field.

Journal ArticleDOI
TL;DR: In this paper, the authors used the TURBO solver to calculate the aero performance of a 2 1/2-stage axial compressor with a phase lag boundary condition.
Abstract: The time-accurate, multi-stage, Navier-Stokes, turbomachinery solver TURBO was used to calculate the aero performance of a 2 1/2 stage, highly-loaded, high-speed, axial compressor. The goals of the research project were to demonstrate completion times for multi-stage, time-accurate simulations that are consistent with inclusion in the design process, and to assess the influence of differing approaches to modeling the effects of blade row interactions on aero performance estimates. Three different simulation setups were used to model blade row interactions: 1.) single passage per blade row with phase lag boundaries, 2.) multiple passages per blade row with phase lag boundaries, and 3.) a periodic sector (1/2 annulus sector). The simulations used identical inlet and exit boundary conditions and identical meshes. To add more blade passages to the domain, the single passage meshes were copied and rotated. This removed any issues of differing mesh topology or mesh density from the following results. The 1/2 annulus simulation utilizing periodic boundary conditions required an order of magnitude less iterations to converge when all three simulations were converged to the same level as assessed by monitoring changes in overall adiabatic efficiency. When using phase lag boundary conditions the need to converge the time history information necessitates more iterations to obtain the same convergence level. In addition to convergence differences, the three simulations gave different overall performance estimates where the 1/2 annulus case was 1.0 point lower in adiabatic efficiency than the single passage phase lag case. The interaction between blade rows in the same frame of reference set up spatial variations of properties in the circumferential direction which are stationary in that reference frame. The phase lag boundary condition formulation will not capture this effect because the blade rows are not moving relative to each other. Thus for simulations of more than two blade rows and strong interactions, a periodic simulation is necessary to estimate the correct aero performance. [Keywords: blade row interaction, numerical modeling, multi-stage compressor]

Journal ArticleDOI
TL;DR: In this article, the effects of water ingestion on the performance of an axial flow compressor were investigated. But this work is restricted to a single rotor and does not consider the effect of water on other rotor blades.
Abstract: New experimental work is reported on the effects of water ingestion on the performance of an axial flow compressor. The background to the work is the effect which heavy rain has on an aero-engine compressor when operating in ‘descent idle’ mode, i.e. when the compressor is operating at part-speed and when the aero-mechanical effects of water ingestion are likely to be more important than the thermodynamic effects. Most of our existing knowledge in this field comes from whole engine tests. The current work provides the first known results from direct measurements on a stand-alone compressor. The influence of droplet size on path trajectory is considered both computationally and experimentally to show that most rain droplets will collide with the first row of rotor blades. The water on the blades is then centrifuged towards the casing where the normal air flow patterns in the vicinity of the rotor tips are disrupted. The result of this disruption is a reduction in the delivery pressure and an increase the torque required to drive the compressor. Both effects reduce the efficiency of the machine. The behaviour of the water in the blade rows is examined in detail, and simple models are proposed to explain the loss of pressure rise and the increase in torque. The measurement were obtained in a low speed compressor making it possible to study the mechanical (increase in torque) and aerodynamic (reduction in pressure rise) effects of water ingestion without the added complication of thermodynamic effects.Copyright © 2005 by ASME

Proceedings ArticleDOI
TL;DR: In this paper, the benefit of endwall boundary layer removal from critical regions of highly loaded axial compressor blade rows is explored, showing substantial benefits of relatively small bleed rates to the local flow field and to the performance of the two blade rows.
Abstract: This paper presents results of numerical investigations carried out to explore the benefit of endwall boundary layer removal from critical regions of highly-loaded axial compressor blade rows. At the loading level of modern aero-engine compressors the performance is primarily determined by three-dimensional flow phenomena occuring in the endwall regions. 3DNS simulations were conducted on both a rotor and a stator test case in order to evaluate basic effects and the practical value of bleeding air from specific locations at the casing endwall. The results of the numerical survey demonstrated substantial benefits of relatively small bleed rates to the local flow field and to the performance of the two blade rows. On the rotor, boundary layer fluid was removed from the main flow path through an axisymmetric slot in the casing over the rotor tip. This proved to give some control over the tip leakage vortex flow and the associated loss generation. On the stator, boundary layer fluid was taken from the flow path through a single bleed hole within the passage. Two alternative off-take configurations were evaluated, revealing a large impact of the bleed hole shape and location on the cross-passage flow and the suction side corner separation. On both blade rows investigated, rotor and stator, boundary layer removal resulted in a reduction of local reverse flow, blockage and losses in the respective near-casing region. This paper gives insight into changes occuring in the 3D passage flow field near the casing and summarises the effects on the radial matching and pitchwise-averaged performance parameters, namely loss and deviation of the rotor and stator when suction is active. Primary focus is put on the aerodynamics in the blade rows in the main flow path; details of the internal flow structure within the bleed off-take cavities/ports are not discussed here.Copyright © 2005 by ASME

Patent
22 Dec 2005
TL;DR: In this article, a compressor for a power system is described, and the compressor has a rotatable wheel and a compressor housing at least partially enclosing the compressor wheel, and a first volute and a second volute are configured to direct an exhaust gas and air radially outward from the wheel.
Abstract: A compressor (24) for a power system (5) is disclosed. The compressor has a compressor (24) wheel (55) rotatable to compress a fluid, and a compressor housing (56) at least partially enclosing the compressor wheel (55). The compressor housing (56) has a first volute (60) and a second volute (62). The first volute (60) is configured to direct an exhaust gas radially inward to the compressor wheel (55). The second volute (62) is configured to direct a mixture of the exhaust gas and air radially outward from the compressor wheel (55).

DOI
01 Jan 2005
TL;DR: In this article, the performance of a single-stage centrifugal compressor operating under wet gas conditions is evaluated at an oil and gas operator's test facility and was executed at full-load and full-pressure conditions using a mixture of hydrocarbon gas and hydrocarbon condensate.
Abstract: This paper presents the results of performance testing of a single-stage centrifugal compressor operating under wet gas conditions. The test was performed at an oil and gas operator’s test facility and was executed at full-load and full-pressure conditions using a mixture of hydrocarbon gas and hydrocarbon condensate. The effect of liquid was investigated by changing the gas-volume fraction between 1.0 and 0.97, which covers the range encountered by the operator during regular gas/condensate field production in the North Sea. Other parameters that were evaluated include the 111 PERFORMANCE EVALUATION OF A CENTRIFUGAL COMPRESSOR OPERATING UNDER WET GAS CONDITIONS by Lars Brenne Staff Engineer Tor Bjorge Staff Engineer Statoil ASA Trondheim, Norway Jose L. Gilarranz Senior Aero/Thermodynamics Engineer Jay M. Koch Staff Engineer, Aero/Thermodynamics and Harry Miller Product Manager, Marketing Dresser-Rand Company Olean, New York compressor test speed, the suction pressure, and two different liquid injection patterns. During the tests, the machine flowrate was varied from near surge to choke conditions; hence, the evaluation covered the entire operating range of the machine. Although the test was primarily intended to evaluate the effects of the wet gas on the thermodynamic performance of the machine, the mechanical performance was also investigated by measuring the machine vibration levels and noise signature during the baseline dry gas tests as well as during the tests with liquid injection. INTRODUCTION Centrifugal compressor packages utilized for upstream gas processing often must operate under wet gas conditions in which the fluid handled by the compression package contains a mixture of liquid and gaseous phases. Typically, the liquid components of the mixture are separated from the gas stream before they enter the compressor by the use of scrubbers and separators located upstream of the compressor inlet. These devices are very large and heavy, requiring a large “footprint” (amount of floor space) as compared to the gas compression package. A compressor with the ability to directly handle wet gas without the need for separation equipment is very attractive from an economic standpoint, as it would drastically reduce the size, weight, and cost of the gas compression package. For the case of future subsea compression systems, this capability is even more attractive because of the high costs of deploying a compressor train and all of its associated equipment under water. Wet gas compression (WGC) technology represents new opportunities for enhanced, cost-effective production from existing and future gas/condensate fields. Many oil and gas operators face future challenges in tail-end production, unmanned operation, and improved recovery from topside and subsea wells. This emphasizes the need to develop more robust compression systems, which can be designed for remote operation in unmanned topside installations, or could be designed for subsea operation for reinjection and/or transport boosting. The use of this technology for subsea boosting represents a new and exciting application for rotating equipment, which will allow new gas/condensate field production opportunities as well as enhanced recovery of existing gas/condensate fields and cost-effective production from marginal gas fields. As mentioned above, these wet gas compression systems could be based on the use of a liquid tolerant dry gas compressor, which could boost a coarsely separated (via a scrubber) well-stream, however, an even more attractive solution would be the development of compression systems that can boost the well-stream directly. Many research projects and product qualification programs are currently underway to develop such a system either by modifying existing multiphase pump technology or by the adaptation of currently available gas compression technologies (Scott, 2004). Regardless of the choice of concept, the compressor solution should be able to tolerate liquid ingestion for an extended time without failure. For the case of subsea applications, the high cost associated with the retrieval of the compressor from the sea floor accentuates the importance of a reliable design. The work presented herein served as an initial test to verify the multiphase boosting capabilities of a centrifugal compressor as well as to provide an oil and gas operator with data to compare the performance of this technology with other available wet gas compression concepts. It is important to state that the test compressor used for this investigation was not originally designed for wet gas boosting, nonetheless it provided an economically viable test bed for centrifugal compressor technology. DESCRIPTION OF TEST VEHICLE The test vehicle used for this work was a barrel-type, singlestage compressor, manufactured by the coauthors’ company. Said compressor was equipped with a high-head impeller, with a diameter of 0.384 m (1.26 ft), and a design flow coefficient of 0.02380. The compressor was originally designed to handle an inlet flow of 4332 Kg/min [2167 Am3/hr (76,526.88 ft3/hr)] of dry hydrocarbon gas (molecular weight of 18.49), with an inlet pressure of 130.2 bar (1888.4 psi)and a discharge pressure of 161.8 bar (2346.7 psi). Figure 1 shows a cross-section of the test compressor; the inlet and discharge nozzles are located at a 45 degree angle with respect to the top dead center of the machine. The original design of this machine, which dates to 1986, was not intended for wet gas service, and hence the internal geometry was not optimal. Nevertheless, in order to increase the reliability of the machine, the original rotor design was modified to accommodate an electron-beam welded and vacuum furnace brazed impeller with a shrink fit to the shaft. The rest of the machine remained the same (i.e., casing and stationary components). This compressor was equipped with a vaneless diffuser configuration. Figure 1. Cross-Section of the Test Compressor. The compressor was driven by a 2.8 MW synchronous electric motor, through a speed increasing gearbox, with a gear ratio of 6.607. A variable speed drive permitted the operation of the compressor within its speed range of 6000 to 13,000 rpm. The test compressor is utilized in the coauthor’s closed loop test facility, and was equipped to simulate the conditions expected for a centrifugal compressor operating under wet gas conditions. Figure 2 shows a schematic diagram of the test loop that was used for the evaluations. The major components of the test loop included a scrubber, the test compressor, a pump, a cooler, and a liquid injection module (mixer). The scrubber, here called guard separator, was used to separate the dry gas (saturated hydrocarbon mixture) from the liquid (hydrocarbon condensate) in order to permit accurate measurement of the massflow of each stream (liquid and gas). The liquid stream was measured with a Coriolis flowmeter while the gas stream was measured with a calibrated orifice plate. Figure 2. Schematic Diagram of the Wet Gas Test Loop. PROCEEDINGS OF THE THIRTY-FOURTH TURBOMACHINERY SYMPOSIUM • 2005 112 Variable Speed Electric Motor (MW) Gas Flow 2 Phase Flow Condensate

Patent
Stephane Baralon1
31 May 2005
TL;DR: In this article, the authors proposed a gas turbine compression system consisting of a gas channel (5), a low pressure compressor section (8), and a high pressure compressor Section (9) for compression of the gas in the channel and a compressor structure (14) arranged between the low pressure compressors and the high compressors.
Abstract: The invention relates to a gas turbine compression system (1) comprising a gas channel (5), a low pressure compressor section (8) and a high pressure compressor section (9) for compression of the gas in the channel and a compressor structure (14) arranged between the low pressure compressor section (8) and the high pressure compressor section (9). The compressor structure (14) being designed to conduct a gas flow in the gas channel and comprises a plurality of radial struts (15, 16, 21, 24, 25) for transmission of load, wherein at least one of said struts (15, 16, 21, 24, 25) is hollow for housing service components. The compressor structure (14) is arranged directly downstream a last rotor (10) in the low pressure compressor section (8) and designed for substantially turning a swirling gas flow from said rotor (10) by a plurality of said struts (15, 16, 21, 24, 25) having a cambered shape.

Patent
15 Jun 2005
TL;DR: The axial injection minimizes or eliminates energy losses due to cross flow injection within the axial air stream while continuing to cool the lintern as discussed by the authors. But, the air changes direction for flow through apertures into and generally coaxially with the free air stream.
Abstract: A combustor has a flow sleeve and a flow liner defining a generally axial flow direction of compressor discharge air toward combustor burners. A casing is secured to the forward end of the flow sleeve defining an annular plenum along the interior of the flow sleeve. Openings through the flow sleeve supply compressor discharge air into the plenum where the air changes direction for flow through apertures into and generally coaxially with the free air stream. The axial injection minimizes or eliminates energy losses due to cross flow injection within the axial air stream while continuing to cool the liner.

Journal ArticleDOI
TL;DR: In this paper, the flow characteristics in the blade passage and in the wake region of a low-speed axial flow fan have been investigated by experimental analysis using a rotating hotwire sensor and a five-hole probe for design and off-design operating conditions.
Abstract: The flow characteristics in the blade passage and in the wake region of a low-speed axial flow fan have been investigated by experimental analysis using a rotating hot-wire sensor and a five-hole probe for design and off-design operating conditions. The results show that the tip leakage vortex is moved upstream when the flow rate is decreased, thus disturbing the formation of wake flow near the rotor tip. That is, the tip leakage vortex interfaces with the blade suction surface and results in high velocity fluctuation near the blade suction surface. From axial velocity distributions downstream of the fan rotor, large axial velocity decay near the rotor tip is observed at near-stall condition, which results in a large blockage compared to that at the design condition. Finally, the wake flow downstream of the rotor blade is clearly measured at the design and off-design conditions. However, the trough of the high velocity fluctuation due to Karmann vortex street in the wake flow is observed at a higher flow condition than the design flow rate.

Journal ArticleDOI
TL;DR: In this article, the authors used the oil film interferometry skin friction technique to measure local skin friction coefficients and shear stress directions on the endwall of a large scale cascade of high pressure turbine airfoils.
Abstract: The complex three-dimensional fluid flow on the endwall in an axial flow turbine blade or vane passage has been extensively investigated and reported on in turbomachinery literature. The aerodynamic loss producing mechanisms associated with the endwall flow are still not fully understood or quantitatively predictable. To better quantify wall friction contributions to endwall aerodynamic loss, low Mach number wind tunnel measurement of skin friction coefficients have been made on one endwall of a large scale cascade of high pressure turbine airfoils, at engine operating Reynolds numbers. Concurrently, predictive calculations of the endwall flow shear stress have been made using a computational fluid dynamics (CFD) code. Use of the oil film interferometry skin friction technique is described and applied to the endwall, to measure local skin friction coefficients and shear stress directions on the endwall. These are correlated with previously reported measured local endwall pressure gradients. The experimental results are discussed and compared to the CFD calculations, to answer questions concerning endwall aerodynamic loss predictive ability.Copyright © 2005 by ASME

Journal ArticleDOI
TL;DR: In this paper, a model single-stage turbine rig using two different vaneblade configurations was used to investigate the cause-effect relationship in the ingestion of gas into axial-flow turbine disk cavities.
Abstract: It has been suggested by researchers that ingestion, through rim seals, of mainstream gas into axial-flow turbine disk cavities is a consequence of the prevailing unsteady three-dimensional flow field. The cause-effect relationship is complex-to help understand it, experiments were performed in a model single-stage turbine rig using two different vaneblade configurations. Selected measurements from one of the configurations were reported earlier (1999-2001). The second configuration is new, featuring smaller numbers of vanes and blades and a larger vane turning angle. Selected measurements are presented and compared to those from the first configuration. The measurements include unsteady and rotor revolution time-average static pressure spatial distributions, and spatial distribution, in the rotor-stator cavity, of time-average ingestion. The parameters in the experiments were the main airflow rate, the purge/seal airflow rate, and the rotor speed. Unsteady three-dimensional CFD simulation may be helpful in identifying the roles of the many intertwined phenomena in the ingestion process.

Journal ArticleDOI
01 Jun 2005
TL;DR: The degradation of compressor blades due to operation in particulate environments is a serious problem for the manufacturers and users of industrial and aeronautical gas turbines, because of drasti...
Abstract: Erosion of compressor blades due to operation in particulate environments is a serious problem for the manufacturers and users of industrial and aeronautical gas turbines, because of drasti...

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effects of operating conditions, tip clearance sizes and external unsteady excitations on the flow of an isolated axial compressor rotor by 3D Navier-Stokes simulations.
Abstract: The paper investigates effects of operating conditions, tip clearance sizes and external unsteady excitations on the unsteady tip clearance flow in an isolated axial compressor rotor by unsteady 3D Navier-Stokes simulations. The results show that the unsteady tip clearance vortex takes a periodic flow behavior in the rotor tip region. With the decrease of the flow coefficient, the unsteady tip clearance vortex is enhanced and its frequency becomes lower. A larger tip clearance size can cause bigger unsteady fluctuation amplitude and a lower fluctuation frequency of the tip clearance vortex at the near stall operating condition. The unsteady excitation with the natural frequency of the tip clearance vortex can enhance the unsteadiness of the tip clearance vortex and improve the overall rotor performance. The frequency of the unsteady tip clearance vortex is independent of external unsteady excitations with different frequencies.

Patent
21 Nov 2005
TL;DR: A turbomachine includes a high-pressure spool, an axial compressor of axis X mounted on a rotor and including a casing and at least one rear bearing disposed between the casing and the rotor of the compressor as discussed by the authors.
Abstract: A turbomachine includes a high-pressure spool, an axial compressor of axis X mounted on a rotor and including a casing and at least one rear bearing disposed between the casing and the rotor of the compressor. The turbomachine further includes an electricity generator coaxial with the spool and including a primary magnetic circuit that is constrained to rotate with the rotor of the compressor and a secondary magnetic circuit that is secured to the casing. The electricity generator is disposed upstream from the rear bearing and includes at least a first cooling circuit surrounding the secondary magnetic circuit and extended by a nozzle for lubricating the rear bearing.

Journal ArticleDOI
TL;DR: In this article, the elliptic instability of a Rankine vortex with axial flow subject to a weak strain field perpendicular to its axis is analyzed by asymptotic methods in the limit of small strain rate.
Abstract: The elliptic instability of a Rankine vortex with axial flow subject to a weak strain field perpendicular to its axis is analyzed by asymptotic methods in the limit of small strain rate. General unstable modes associated with resonant Kelvin modes of arbitrary azimuthal wavenumbers are considered. Both the effects of axial flow and viscosity are analyzed in details.

Journal ArticleDOI
01 Aug 2005
TL;DR: In this article, the authors present numerical simulations for a high-speed transonic compressor rotor, NASA Rotor 37, applying a state-of-the-art design for the blade tip injection.
Abstract: The casing treatment and flow injection upstream of the rotor tip are two effective approaches in suppressing instabilities or recovering from a fully developed stall. This paper presents numerical simulations for a high-speed transonic compressor rotor, NASA Rotor 37, applying a state-of-the-art design for the blade tip injection. This is characterized by introducing a jet flow directly into the casing treatment machined into the shroud. The casing treatment is positioned over the blade tip region and exceeds the impeller axially by ∼30 per cent of the tip chord both in the upstream and in the downstream directions. To numerically solve the governing equations, the three-dimensional finite element based finite volume method CFD solver CFX-TASCflow (version 2.12.1) is employed. For a compressible flow with varying density, Reynolds-averaging leads to appearance of complicated correlations. To avoid this, the mass-weighted or Favre-averaging is applied. Using an injected mass flow of 2.4 per cent o...

Journal ArticleDOI
01 Sep 2005
TL;DR: In this article, the authors used high-response total pressure probes to determine the cause of aerodynamic excitation from traverses of the unsteady pressure field at three planes in the last stage.
Abstract: Experimental investigations on two different three-stage low-pressure (LP) model turbines operated on steam during windage are presented. At very low flows, strain gauges identified that the two turbines exhibit different dynamic stress characteristics of the last-stage rotor blades. The first turbine experienced the highest vibrations from aerodynamic excitations at the resonant frequency of the second mode in a narrow operating range around 13 per cent of the design flow, whereas the second turbine experienced no resonance up to the fourth mode and has the highest dynamic loading at zero flow. Specially developed high-response total pressure probes have been used to determine the cause of the aerodynamic excitation from traverses of the unsteady pressure field at three planes in the last stage. The experimental data for both turbines show that unsteady pressure disturbances steadily grow when the flow is reduced below 25 per cent of design flow and that the excitations are strongest in the axial gap between the guide vane and the rotor of the last stage near the outer casing. Detailed analysis shows that high-amplitude disturbances occur at distinct frequencies and that these rotate in the circumferential direction at a fraction of the rotor speed. Comparison of the pressure signals measured at two circumferential locations on the casing of the second turbine confirmed the characteristic frequency pattern to be a so called 'rotating instability'. This unsteady phenomenon arising from the tip leakage flow has previously been observed in axial flow fans and compressors and is demonstrated for the first time here in a turbine operating at very low flow rates.

Journal ArticleDOI
TL;DR: In this article, the effect of the rotor tip on the casing heat load of a transonic axial flow turbine was investigated and it was shown that an increased stagnation temperature in the tip gap dominates casing heat transfer.
Abstract: This paper considers the effect of the rotor tip on the casing heat load of a transonic axial flow turbine. The aim of the research is to understand the dominant causes of casing heat transfer. Experimental measurements were conducted at engine-representative Mach number, Reynolds number, and stage inlet to casing wall temperature ratio. Time-resolved heat-transfer coefficient and gas recovery temperature on the casing were measured using an array of heat-transfer gauges. Time-resolved static pressure on the casing wall was measured using Kulite pressure transducers. Time-resolved numerical simulations were undertaken to aid understanding of the mechanism responsible for casing heat load. The results show that between 35% and 60% axial chord the rotor tip-leakage flow is responsible for more than 50% of casing heat transfer. The effects of both gas recovery temperature and heat transfer coefficient were investigated separately and it is shown that an increased stagnation temperature in the rotor tip gap dominates casing heat transfer. In the tip gap the stagnation temperature is shown to rise above that found at stage inlet (combustor exit) by as much as 35% of stage total temperature drop. The rise in stagnation temperature is caused by an isentropic work input to the tip-leakage fluid by the rotor. The size of this mechanism is investigated by computationally tracking fluid path lines through the rotor tip gap to understand the unsteady work processes that occur.