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1
Zaki, Mina Adel. "Physics based modeling of axial compressor stall." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31683.
Full textAbstract:
Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2010.Committee Chair: Dr. Lakshmi N. Sankar; Committee Member: Dr. Alex Stein; Committee Member: Dr. J.V. R. Prasad; Committee Member: Dr. Richard Gaeta; Committee Member: Dr. Suresh Menon. Part of the SMARTech Electronic Thesis and Dissertation Collection.
2
DiPietro, Anthony Louis. "Effects of temperature transients on the stall and stall recovery aerodynamics of a multi-stage axial flow compressor." Diss., This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-10052007-143638/.
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3
Rivera-Cedeno, Carlos J. "Numerical simulation of dynamic stall phenomena in axial flow compressor blade rows." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12405.
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4
Nowinski, Matthew C. "A two-dimensional model to predict rotating stall in axial-flow compressors." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-08042009-040420/.
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5
Cousins, William T. "The Dynamics of Stall and Surge Behavior in Axial-Centrifugal Compressors." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29794.
Full textAbstract:
The phenomena of stall and surge in axial-centrifugal compressors is investigated through high-response measurements of both the pressure field and the flowfield throughout the surge cycle. A unique high-response forward-facing and aft-facing probe provides flow information. Several axial-centrifugal compressors are examined, both in compressor rigs and engines. Extensive discussion is presented on the differences in axial and centrifugal rotors and their effect on the system response characteristics. The loading parameters of both are examined and data is presented that shows the increased tolerance of the centrifugal stage to instability. The dynamics of the compressor blade response are shown to be related to the transport time of a fluid particle moving through a blade passage. The data presented provides new insight into the dynamic interactions that occur prior to and during stall and surge. In addition, the inception of rotating stall and the inception of surge are shown to be the same phenomena . An analytical dynamic model (DYNTECC) is applied to one of the compression systems and the results are compared to data. The results show that the model can capture the global effects of rotating stall and surge. The data presented, along with the analytical results, provide useful information for the design of active and passive stall control systems.Ph. D.
6
Akhlaghi, Mohammad. "Application of a vane-recessed tubular-passage casing treatment to a multistage axial-flow compressor." Thesis, Cranfield University, 2001. http://dspace.lib.cranfield.ac.uk/handle/1826/11401.
Full textAbstract:
The current study investigates a range of issues relating to the use of a vane-recessed tubular-passage casing treatment as a passive stall control technique in a multistage axial-flow compressor. The focus of the research was to determine whether such a treatment could delay the initiation of stall at lower mass flow rates as well as providing the most beneficial improvement in flow characteristics without sacrificing compressor efficiencies. Specific objectives of this study were to examine possible improvements or deterioration in the flow characteristics including stall margin, peak pressure rise coefficients and maximum efficiency in a multistage axial flow compressor. A casing treatment in addition to several spacer rings was developed from two initial designs and tested on the first stage of a low speed three-stage axial-flow compressor with a (0.7) hub to tip diameter ratio. The treatment configuration consisted of three parts: an outer casing ring, with a tubular shaped passage on the inside diameter, a set of 120 evenly spaced curved vanes, and a shroud or inner ring. The casing treatment was positioned following the inlet guide vanes upstream and partly covering the tip of the rotor blades. The main parts of the casing treatment including the recessed vanes in addition to some of the spacer rings were manufactured from high quality acrylic. Eight additional spacer rings of various shapes and geometry were added. The first ring held and partly covered the IGVs, in front of the casing treatment. The rotor tip exposure ratio was thought to have a significant impact on the effectiveness of the casing treatment. Therefore the other seven rings were used to provide the desired uncovered region of the rotor tip axial chord of about 10% in order to provide a range of exposures of (23.2%, 33.3%, 43.4%, 53.5%, 63.6%, 73.7%, and 83.8%). The results showed significant improvements in stall margin in all treated casing configurations along with insignificant efficiency sacrifices in some compressor builds. About (28.56%) of stall margin improvement in terms of corrected mass flow rate was achieved using a casing treatment with a (33.3%) rotor tip exposure. The compressor build with (0.535) rotor exposure ratios was the best configuration in terms of efficiency gain and loss characteristics. This build was able to provide the highest values of the maximum efficiencies in comparison with the performance achieved from the solid casing. An improvement of (1.81%) in the maximum efficiency in terms of the overall total-total pressure ratio, in association with a (22.54%) stall margin improvement in terms of the corrected mass flow rates were achieved by the application of this treatment configuration. The improvement in the peak pressure rise coefficients in terms of the overall total-total pressure ratio, obtained from this build was (2.33%). The compressor configuration using a casing treatment with a (0.636) rotor exposure ratio was the best build in terms of the pressure rise coefficients. This configuration was able to provide highest value of the peak pressure rise in comparison with the characteristics achieved from the datum build. An improvement of (2.65%) in the peak pressure rise coefficient in terms of the overall total-total pressure ratio, in association with a (22.49%) improvement in stall margin in terms of the corrected mass flow rates was achieved from this casing treatment build. The improvement in maximum efficiency in terms of the overall total-total pressure ratio, obtained from this build was (1.03%). The results suggest that the vane-recessed tubular-passage casing treatment designed as part of this investigation achieved the objectives, which were established for the research. In the majority of instances it not only produced gains in flow range, pressure rise coefficients and efficiencies, but also enabled the rotating stall, which developed at much lower mass flow rates in the compressor, to become progressive rather than abrupt.
7
Fourie, Neil. "Simulating the effect of wind on the performance of axial flow fans in air-cooled steam condenser systems." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95977.
Full textAbstract:
Thesis (MEng) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: The use of air-cooled steam condensers (ACSCs) is the preferred cooling method in the chemical and power industry due to stringent environmental and water use regulations. The performance of ACSCs is however highly dependent on the influence of windy conditions. Research has shown that the presence of wind reduces the performance of ACSCs. It has been found that cross-winds (wind perpendicular to the longest side of the ACSC) cause distorted inlet flow conditions, particularly at the upstream peripheral fans near the symmetry plane of the ACSC. These fans are subjected to what is referred to as '2-D' wind conditions, which are characterised by flow separation on the upstream edge of the fan inlets. Experimental investigations into inlet flow distortion have simulated these conditions by varying the fan platform height. Low platform heights resulted in higher levels of inlet flow distortion, as also found to exist with high cross-wind speeds. This investigation determines the performance of various fan configurations (representative of configurations used in the South- African power industry) subjected to distorted inlet flow conditions through experimental and numerical investigations. The similarity between platform height and cross-wind effects is also investigated and a correlation between system volumetric effectiveness, platform height and cross-wind velocity is found.
AFRIKAANSE OPSOMMING: Die gebruik van lugverkoelde stoom kondensors (LVSK's) word verkies as 'n verkoelingsmetode in die chemiese- en kragvoorsieningsindustrie as gevolg van streng omgewings- en waterverbruiksregulasies. Die werkverrigting van LVSK's word egter grootliks beïnvloed deur die teenwoordigheid van wind. Navorsing het gewys dat die teenwoordigheid van wind die werkverrigting van LVSK's verminder. Daar was gevind dat kruiswinde (wind loodreg tot die langste sy van die LVSK) versteurde inlaat vloeitoestande veroorsaak, veral by waaiers wat aan die stroomop kant van die LVSK naby die simmetrievlak geleë is. Hierdie waaiers word blootgestel aan na wat verwys word as '2-D' windtoestande wat gekenmerk word deur vloeiwegbreking wat plaasvind by die stroomop rand van die waaierinlate. Eksperimentele ondersoeke van inlaat vloeiversteurings het hierdie toestande gesimuleer deur die waaier platformhoogte te verstel. Lae platform hoogtes het gelei tot hoër vlakke van inlaat vloeiversteuring, soortgelyk aan wat gevind word met hoë kruiswindsnelhede. Hierdie ondersoek gebruik numeriese en eksperimentele metodes om die werkverrigting van verskeie waaierkon gurasies (verteenwoordigend van kon- gurasies wat gebruik word in die Suid-Afrikaanse kragvoorsieningsindustrie) wat blootgestel word aan versteurde inlaat vloeitoestande te bepaal. Die ooreenkoms tussen platformhoogte en kruiswind e ekte word ook ondersoek en 'n korrelasie tussen die sisteem volumetriese e ektiwiteit, platformhoogte en kruiswindsnelheid word bepaal.
8
Grimshaw, Samuel David. "Bleed in axial compressors." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707970.
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9
Power, Bronwyn. "Aspirated compressors." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648363.
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10
Li, Yan Sheng. "Mixing in axial compressors." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334235.
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11
Butler, Bradley D. "AXIAL COMPRESSOR FLOW BEHAVIOR NEAR THE AERODYNAMIC STABILITY LIMIT." UKnowledge, 2014. http://uknowledge.uky.edu/me_etds/34.
Full textAbstract:
In this investigation, casing mounted high frequency response pressure transducers are used to characterize the flow behavior near the aerodynamic stability limit of a low speed single stage axial flow compressor. Time variant pressure measurements are acquired at discrete operating points up to the stall inception point and during the transition to rotating stall, for a length of time no shorter than 900 rotor revolutions. The experimental data is analyzed using multiple techniques in the time and frequency domains.
Experimental results have shown an increase in the breakdown of flow periodicity as the flow coefficient is reduced. Below a flow coefficient of 0.40 a two node rotating disturbance develops with a propagation velocity of approximately 23% rotor speed in the direction of rotation. During rotating stall, a single stall cell is present with a propagation velocity of approximately 35% rotor speed. The stall inception events present are indicative of a modal stall inception.
12
Seitz, Peter Alexander. "Casing treatment for axial flow compressors." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/251677.
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13
Storer, John Andrew. "Tip clearance flow in axial compressors." Thesis, University of Cambridge, 1991. https://www.repository.cam.ac.uk/handle/1810/251503.
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14
McDougall, Neil Malcolm. "Stall inception in axial compressors." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237803.
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15
Schmidt, M. J. P. "Blade tip clearance effects on an axial flow compressor rotor." Thesis, Cranfield University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354277.
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16
Wilson, Alexander George. "Stall and surge in axial flow compressors." Thesis, Cranfield University, 1996. http://dspace.lib.cranfield.ac.uk/handle/1826/10432.
Full textAbstract:
The objective of the work described in this thesis is twofold; to elucidate the nature of
stall and
surge in an axial flow aeroengine compressor, and to improve on current
computational stall modelling techniques. Particular attention is paid to
the initial stages of the stall/surge transient, and to the possibility of using active control
techniques to prevent or delay the onset of stall/surge.
A detailed
analysis is presented of measurements of the stalling behaviour of a Rolls-
Royce VIPER jet engine, showing a wide variety of stall inception and post-stall
behaviour. Stall transients are traced from disturbances through to stable
rotating stall or axisymmetic surge. The stall inception pattern at nearly all speeds is
shown to conform to the short circumferential length scale pattern described by Day
[1993a].
A multiple compressors in parallel stall model is developed using conventional stall
modelling techniques, but extended to include the
effects of the jet engine environment
The model is shown to
give a good representation of the overall stalling behaviour of
the
engine, although the details of the stall inception period are not accurately
predicted. A system identification technique is applied to the results of the model in
order to
develop a method of active control of stall/surge.
A new stall model is introduced and
developed, based on a time-accurate three
dimensional (but pitchwise averaged) solution of the viscous flow equations, with
bladerow performance represented by body forces. The flow in the annulus boundary
layers is calculated directly, and hence this new method is sufficiently complex to
model the initial localised disturbances that lead to
stall/surge. At the same time the
computational power required is compatible with application to long multistage
compressors.
17
Pantelidis, Konstantinos. "Reynolds number effects on the aerodynamics of compact axial compressors." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/284940.
Full textAbstract:
An axial compressor for a domestic appliance can be designed to be smaller than an equivalent centrifugal compressor. However, the performance of such a compact axial compression system is limited by increased viscous losses and reduced flow turning at low Reynolds numbers ($Re$). In domestic appliance compressors, $Re$ is typically in the range $10^4$ - $10^5$. Although the aerodynamics of isolated aerofoils operating at these $Re$ have been studied extensively, the flow fields within low $Re$ axial compressors have not been investigated in detail. This dissertation aims to develop an improved understanding of loss variation at low $Re$ and to explore how the losses can be reduced through design changes. Experiments on a 5 times scaled-up single stage axial compressor have been conducted across a range of $Re$ of $10^4$ - $10^5$. The flow field has been characterised using detailed area traverses with a miniaturised five-hole probe at the rotor inlet, rotor exit and stator exit and a miniature hot-wire at the rotor exit. The probe was specifically designed and calibrated for the scale of the experiments and methods to improve the accuracy of the measurements have been applied including a probe geometry correction. The traverse experiments were performed at the design operating condition ($\phi=0.55$ and $Re= 6\times10^4$) and at a condition close to stall for a datum stage design, a stage with an improved stator design and two stators with compound lean. It was found that losses in the rotor were greater than the stator losses across the whole range of $Re$. As expected, the loss decreased with increasing $Re$ for both the stator and rotor. The losses were also increased by three-dimensional flow, with typical loss coefficients at the hub and tip of the blade rows in the range of $20-30\%$. A major contributor to the rotor loss was an unexpected hub separation that increased in size as $Re$ was reduced. At higher $Re$, the major loss sources were the rotor tip leakage, the stator wake and the stator hub separation. The results indicate that an improved stator design that accounts for the actual, measured, rotor exit flow field at low $Re$ could reduce the $Re$ at which blade row losses start to rise dramatically as well as reduce the loss across all $Re$. The improved stator design was better matched to the radial distribution of rotor exit flow angle, which led to a decrease in stator loss across all $Re$. For all stator designs, however, the measured stage stall margin was identical at all $Re$. This, along with the increase in velocity deficit in the rotor tip region at off-design indicates that stall occurred in the rotor and was neither $Re$ nor stator design dependent. The introduction of compound lean to the the stator design had the expected result of decreasing the endwall corner separation loss and increasing midspan losses. The experiments have shown that there was a loss increase in both the midspan and casing region much greater than the corresponding decrease in the stator hub. Also the mass flow redistribution in the experiments was larger that the redistribution predicted by the CFD. Three-dimensional RANS computations at low $Re$ of the same designs as experimentally studied were also conducted in order to investigate the predictive accuracy of industry standard CFD. The simulation results predicted the overall loss distribution but overestimated the end-wall losses and failed to capture the drop in stage performance at low $Re$. The differences with the experiments were caused by the inherent limitations of a fully turbulent solver that cannot reproduce transitional flow-features. Similarly to the experiments, there was no stall margin dependency on $Re$ in the simulations. This thesis has shown that with axial compressors designed specifically for low $Re$, the $Re$ at which the losses start increasing exponentially can be shifted from $10\times10^4$ to $ 4\times10^4$. The loss increase is predominantly caused by the rotor hub corner separation.
18
Thomas, Keegan Darrall. "Blade row and blockage modelling in an axial compressor throughflow code /." Link to the online version, 2005. http://hdl.handle.net/10019/1239.
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19
Gallimore, Simon John. "Spanwise mixing in multi-stage axial compressors." Thesis, University of Cambridge, 1986. https://www.repository.cam.ac.uk/handle/1810/250879.
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20
Meehan, Anthony. "Steady state response of an axial compression system to a constant heat input." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15975.
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21
Li, Yan-Ling. "Numerical simulations of rotating stall in axial flow compressors." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/47428/.
Full textAbstract:
Gas turbine compressor performance may encounter deterioration during service for various reasons such as damage by debris from the casing or foreign objects impacting on the blades, typically near the rotor's tip. Moreover, mal-schedule of Variable Stator Vanes (VSVs) during start-up may also result in performance deterioration and reduction in the surge margin. Ability to assess the effect of compressor deterioration using Computational Fluid Dynamics (CFD) is important at both design stage and in service. Compressor blade damage breaks the cyclic symmetry and the VSVs mal-schecule creates mis-match between stages together with geometric variations, thus computations are desirable to be performed using full annulus assemblies. Furthermore, downstream boundary conditions are also unknown during rotating stall or surge and simulations become difficult. This research presents unsteady time-accurate CFD analyses of compressor performance with tip curl blade damage in a single stage axial flow compressor and VSVs mal-schedule in a 3.5 stage axial flow compressor. Computations were per- formed near stall boundary to predict rotating stall characteristics. The primary objectives are to characterise the overall compressor performance and analyse the detailed flow behaviour. Computations for the nominal blade configurations were also performed for comparison purposes for both compressors. All unsteady simulations were performed at part speeds with a variable nozzle downstream representing an experimental throttle. For the blade damage study, two different degrees of damage for one blade and multiple damaged blades were investigated and compared with the results from the undamaged case. For the VSVs mal-schedule study, the first two stators were assumed to be variable and were used to create mal-schedule vane settings for the investigation. The effects of blade damage and VSVs mal-schedule on the aerodynamics performance and rotating stall characteristics for both compressor assemblies were investigated respectively and discussed in detail.
22
Bae, Jinwoo W. "Active control of tip clearance flow in axial compressors." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8705.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001.Includes bibliographical references.
Control of compressor tip clearance flows is explored in a linear cascade using three types of fluidic actuators; Normal Synthetic Jet (NSJ; unsteady jet normal to the mean flow with zero net mass flux), Directed Synthetic Jet (DSJ; injection roughly aligned with the mean flow), and Steady Directed Jet (SDJ), mounted on the casing wall. The objective is to affect the following measures: (1) reduction of tip leakage flow rate, (2) mixing enhancement between tip leakage and core flow, and (3) increase in streamwise momentum of the flow in the endwall region. The measurements show that the NSJ provides mixing enhancement only, or both mixing enhancement and leakage flow reduction, depending on its pitchwise location. The DSJ and SDJ actuators provide streamwise momentum enhancement with a consequent reduction of clearance-related blockage. The blockage reduction associated with the use of NSJ is sensitive to actuator frequency, whereas that with the use of DSJ is not. For a given actuation amplitude, DSJ and SDJ are about twice as effective as NSJ in reducing clearance-related blockage. Further the DSJ and SDJ can eliminate clearance-related blockage with a time-averaged momentum flux roughly 16% of the momentum flux of the leakage flow.
(cont.) However, achieving overall gain in efficiency appears to be hard; the decrease in loss is only about 30% of the expended flow power from the present SDJ actuator, which is the best among the actuators considered. Guidelines for improving the efficiency of the directed jet actuation are presented. Time-resolved measurements show periodic unsteadiness of the tip clearance vortex with the peak frequency corresponding to the optimum condition for blockage reduction with the NSJ. A physical explanation of the source of the observed periodic unsteadiness is suggested based on trailing vortex instability theory. Observations of the time scale for the unsteadiness from different compressor geometries and flow conditions are shown to scale with a reduced frequency based on convective time through the blade passage.
by Jinwoo Bae.
Ph.D.
23
White, N. M. "Optimising stator vane settings in multistage axial flow compressors." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/10756.
Full textAbstract:
There is a common
requirement in the process, oil and gas turbine industries for high
performance axial flow compressors operating over a wide range of mass flow rate and
rotational
speed at high efficiency. The trends have been for higher blade loadings
(greater pressure rise per stage) and higher efficiency which are increasingly achieved
through sophisticated Computational Fluid Dynamics designs. These trends, however,
tend to
mitigate against stable operating flow range (reduced surge margin), which can
often lead to
performance compromises. The objective of this work is to investigate the
possibility of using alternative means to gain ow range by better use of variable
geometry, which may permit design objectives to be better achieved. Variable
geometry of the type envisaged is already often employed to overcome part-speed
operating problems, but it proposed here that there may be additional benefits from their
more
intelligent control.
The
operation of axial compressors with a wide operating range is limited by
instabilities, which cause a full breakdown of the flow, which is surge. These
instabilities, which are caused by high incidence and subsequent stalling of stages occur
due to different
phenomena at part and full speed operation. The problem at part-speed
is that the front
stages are often heavily stalled and rear stages choked, whereas at high
speeds, the front stages are operating close to choke and the rear stages tend to be
stalling. Optimisation of the design to full load conditions can often provide part-speed
problems and to achieve the acceptable performance, variable geometry over the front
region of the compressor is sometimes used to modify the flow angles and avoid stage
stall and
subsequent surge. To-date, such variable settings follow some schedule
established
by analysis and experiment whereas this work presents a methodology of
setting blade rows using an optimisation procedure and investigates the likelihood of
performance benefits being obtained by a control technique which reacts° to these
changing conditions.
The construction of the numerical method
presented in this thesis was done with an
emphasis upon its intended contribution towards a eventual online control application.
Therefore, a practical approach has been employed in the development of the
compressor modelling techniques used in the work. Specifically, a highly empirical
one-dimensional
performance prediction code was constructed, employing successful
correlations taken from the literature. This was
coupled to a surge prediction method
that has been shown in the
past to function more than satisfactorily in a multistage
environment.
Finally, the predicted stage and overall performance (including the surge
point) characteristics were passed to a optimisation program, which allowed these
simulated conditions to be
investigated.
It is
hoped that the work presented has illustrated the potential (from a aerodynamic
performance point of view) of such a control technique to offer additional freedom in
the
operation of a multistage axial flow compressor. Moreover, the numerical
modelling techniques have been developed enough to envisage (at least in part) their
simple integration within a practical system. Clearly, some further investigations are
required to take this work forward and the next logical step would be to improve the
empirical rules with which the blade performance is predicted. A experimental
programme would also be of great advantage, for example in the study of how the
deviation
angle for a given blade row varies over time (operating hours) in a real
machine due to
ageing and fouling. This would allow better estimates of the stage work
during long term operation so that the optimiser could adapt to the slowly degrading
performance of the blades. Finally, it is important to verify the simulated results with
measured data, taken at the same optimal stator vane settings as given by the program.
This must be carried out before it can be
applied to a real application, although a limited
study of this nature is presented in chapter 6.
24
White, Nicholas M. "Optimising stator vane settings in multistage axial flow compressors." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/10756.
Full textAbstract:
There is a common requirement in the process, oil and gas turbine industries for high performance axial flow compressors operating over a wide range of mass flow rate and rotational speed at high efficiency. The trends have been for higher blade loadings (greater pressure rise per stage) and higher efficiency which are increasingly achieved through sophisticated Computational Fluid Dynamics designs. These trends, however, tend to mitigate against stable operating flow range (reduced surge margin), which can often lead to performance compromises. The objective of this work is to investigate the possibility of using alternative means to gain ow range by better use of variable geometry, which may permit design objectives to be better achieved. Variable geometry of the type envisaged is already often employed to overcome part-speed operating problems, but it proposed here that there may be additional benefits from their more intelligent control. The operation of axial compressors with a wide operating range is limited by instabilities, which cause a full breakdown of the flow, which is surge. These instabilities, which are caused by high incidence and subsequent stalling of stages occur due to different phenomena at part and full speed operation. The problem at part-speed is that the front stages are often heavily stalled and rear stages choked, whereas at high speeds, the front stages are operating close to choke and the rear stages tend to be stalling. Optimisation of the design to full load conditions can often provide part-speed problems and to achieve the acceptable performance, variable geometry over the front region of the compressor is sometimes used to modify the flow angles and avoid stage stall and subsequent surge. To-date, such variable settings follow some schedule established by analysis and experiment whereas this work presents a methodology of setting blade rows using an optimisation procedure and investigates the likelihood of performance benefits being obtained by a control technique which reacts° to these changing conditions. The construction of the numerical method presented in this thesis was done with an emphasis upon its intended contribution towards a eventual online control application. Therefore, a practical approach has been employed in the development of the compressor modelling techniques used in the work. Specifically, a highly empirical one-dimensional performance prediction code was constructed, employing successful correlations taken from the literature. This was coupled to a surge prediction method that has been shown in the past to function more than satisfactorily in a multistage environment. Finally, the predicted stage and overall performance (including the surge point) characteristics were passed to a optimisation program, which allowed these simulated conditions to be investigated. It is hoped that the work presented has illustrated the potential (from a aerodynamic performance point of view) of such a control technique to offer additional freedom in the operation of a multistage axial flow compressor. Moreover, the numerical modelling techniques have been developed enough to envisage (at least in part) their simple integration within a practical system. Clearly, some further investigations are required to take this work forward and the next logical step would be to improve the empirical rules with which the blade performance is predicted. A experimental programme would also be of great advantage, for example in the study of how the deviation angle for a given blade row varies over time (operating hours) in a real machine due to ageing and fouling. This would allow better estimates of the stage work during long term operation so that the optimiser could adapt to the slowly degrading performance of the blades. Finally, it is important to verify the simulated results with measured data, taken at the same optimal stator vane settings as given by the program. This must be carried out before it can be applied to a real application, although a limited study of this nature is presented in chapter 6.
25
Li, Yiguang. "Three-Dimensional Flow and Performance Simulation of Multistage Axial Flow Compressors." Thesis, Cranfield University, 2000. http://dspace.lib.cranfield.ac.uk/handle/1826/4591.
Full textAbstract:
\Yith the current develop111ent in computer technology and Computational
Fluid D)"n<'tlllics techniques, t.he si11utlation within axial flow compressors becomes
1110re and 1110re pract.ical and beneficial to the compressor designs. Due to the
insufficient capabilit)" of today's COll1put.ers for three-dimensional unsteady flow
1110delling of 111Ult i~Llg(' axial flow compressors, sophisticated models of steady
state flow and perfor111ance 1110delling of the C0111prcssors deserve to be thoroughly
investigated.
In l1utltistage C0111pressor sinlulations with steady state methods, frame of reference
is fixed on blades and the c0111putational domains for rotors and stators
haye relati\"e rotation. One of the difficulties in such simulations is how to pass
information across the interfaces between blade rows without losing continuity.
Two 111ajor stead)" state modelling approaches, a mixing plane approach based
on Denton's circu111ferentially non-uniform mixing plane model and a deterministic
stress approach based on Adamczyk's average passage model, are investigated
and compared with each other through the flow predictions of the third stage of
Cranfield Low Speed Research Compressor at peak efficiency operating condition.
In the deterministic stress approach, overlapped solution domains are introduced
to calculate deterministic stresses in order to "close" the time-averaged
governing equation system and the influence of the downstream blade row of the
blade row under investigation has to be imposed through the simulation of bodyforce
and blade blockage effect of the downstream blade row. An effective method
of simulating bodyforce and blade blockage effect has been developed and proven
to be simple in programming.
ConYentionally, boundary conditions are specified in CFD calculations based
on experimental data or other empirical calculations. By taking advantage of the
special flow features in rear stages of multistage axial flow compressors where each
rear stage behaves like a repeating stage of its neighbouring stages in terms of
flow pattern at the inlet and the exit of these stages, a repeating stage model has
been developed aiming at significantly simplifying the boundary conditions when
simulating rear stages of a multistage axial flow compressor with only mass flow
rate and stage exit average static pressure required as global input.
A computer simulation system 1'/ STurbo3D has been developed to investigate
a11d assess different steady state simulation models within multistage compressor
environment. It has been proven that with the mixing plane model M STurbo3D is
able to predict flows in multistage low speed axial flow compressors with acceptable
accuracy. Application of the repeating stage model to the third stage of LS RC
shows that the prediction with this model has equivalent accuracy to the prediction
with the conventional boundary setting, and proves that the repeating stage
model is an effective alternative to the expensive complete compressor simulation.
The deterministic stress model provides more information of rotor-stator interaction
and slightly better performance prediction than the mixing plane model, but
the benefits of the model is not significant when applied to low speed axial flow
compressors.
26
Bloch, Gregory S. "A wide-range axial-flow compressor stage performance model." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08182009-040326/.
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Robinson, Christopher J. "End-wall flows and blading design for axial flow compressors." Thesis, Cranfield University, 1991. http://dspace.lib.cranfield.ac.uk/handle/1826/6929.
Full textAbstract:
The flow in multistage axial flow compressors is
particularly complex in nature because of the proximity of
moving bladerows, the growth of end-wall boundary layers and
the presence of tip and seal leakages and secondary flow.
The problems associated with these phenomena are at their
most acute in the latter, subsonic stages of the core
compressor, where Reynolds numbers are modest and the
blading has low aspect ratio. Indeed, much of the
inefficiency of axial stages is believed to be associated
with the interaction between blading and end-wall flows.
The fact that the end-wall flow phenomena result in
conditions local to the blade which are quite different
from those over the major part of the annulus was
appreciated by many of the earliest workers in the axial
turbomachinery field. However, experiments on blading
designs aimed specifically at attacking the end-loss have
been sparse.
This thesis includes results from tests of conventional
and end-bent blading in a four-stage, low-speed, axial
compressor, built specifically for the task, at a scale
where high spatial measurement resolution could be readily
achieved within the flowpath. Two basic design styles are
considered: a zero a0 stage with DCA aerofoils and a
low-reaction controlled-diffusion design with cantilevered
stators.
The data gives insight into the flow phenomena present in
'buried' stages and has resulted in a much clearer
understanding of the behaviour of end-bent blading. A
3D Navier-Stokes solver was calibrated on the two
low-reaction stators and was found to give good agreement
with most aspects of the experimental results. An improved
design procedure is suggested based on the incorporation
of end-bends into the throughflow and iterative use of the
3D Navier-Stokes solver.
28
Gill, Andrew. "A comparison between stall prediction models for axial flow compressors." Thesis, Stellenbosch : Stellenbosch University, 2006. http://hdl.handle.net/10019.1/18702.
Full textAbstract:
Thesis (MScEng)--Stellenbosch University, 2006.ENGLISH ABSTRACT: The Stellenbosch University Compressor Code (SUCC) has been developed for the purpose of predicting the performance of axial flow compressors by means of axisymmetric inviscid throughflow methods with boundary layer blockage and empirical blade row loss models. This thesis describes the process of the implementation and verification of a number of stall prediction criteria in the SUCC. In addition, it was considered desirable to determine how certain factors influence the accuracy of the stall prediction criteria, namely the nature of the computational grid, the choice of throughflow method used, and the use of a boundary layer blockage model and a radial mixing model. The stall prediction criteria implemented were the di®usion factor limit criterion, de Haller's criterion, Aungier's blade row criterion, Aungier's boundary layer separation criterion, Dunham's, Aungier's and the static-to-static stability criteria. The compressors used as test cases were the Rofanco 3-stage low speed compressor, the NACA 10-stage subsonic compressor, and the NACA 5-stage and 8-stage transonic compressors. Accurate boundary layer blockage modelling was found to be of great importance in the prediction of the onset of stall, and that the matrix throughflow Method provided slightly better accuracy than the streamline curvature method as implemented in the SUCC by the author. The ideal computational grid was found to have many streamlines and a small number of quasi-orthogonals which do not occur inside blade rows. Radial mixing modelling improved the stability of both the matrix throughflow and streamline curvature methods without significantly affecting the accuracy of the stall prediction criteria. De Haller's criterion was over-conservative in estimating the stall line for transonic conditions, but more useful in subsonic conditions. Aungier's blade row criterion provided accurate results on all but the Rofanco compressor. The diffusion factor criterion provided over- optimistic predictions on all machines, but was less inaccurate than de Haller's criterion on the NACA 5-stage transsonic machine near design conditions. The stability methods performed uniformly and equally badly, supporting the claims of other researchers that they are of limited usefulness with throughflow simulations. Aungier's boundary layer separation method failed to predict stall entirely, although this could reflect a shortcoming of the boundary layer blockage model.
AFRIKAANSE OPSOMMING: Die Stellenbosch University Compressor Code (SUCC) is ontwikkel om die prestasie van aksiaalvloei kompressors te voorspel met behulp van aksisimmetriese nie-viskeuse deurvloeimetodes met grenslaagblokkasie en empiriese modelle vir die verliese binne lemrye. Hierdie tesis beskryf die proses waarmee sekere staakvoorspellingsmetodes in die SUCC geïmplementeer en geverifieer is. Dit was ook nodig om die effek van sekere faktore, naamlik die vorm van die berekeningsrooster, die keuse van deurvloeimetode en die gebruik van `n grenslaagblokkasiemodel en radiale vloeivermengingsmodel op die akuraatheid van die staakvoorspellingsmetodes te bepaal. Die staakvoorspellingsmetodes wat geïmplementeer is, is die diffusie faktor beperking metode, de Haller se metode, Aungier se lemrymetode, Aungier se grenslaagmetode en die Dunham, Aungier en die statiese-tot-statiese stabiliteitsmetodes. Die kompressors wat gebruik is om die metodes te toets is die Rofanco 3-stadium lae-spoed kompressor, die NACA 10-stadium subsoniese kompressor en die NACA 5- en 8-stadium transsoniese kompressors. Daar is vasgestel dat akkurate grenslaagblokkasie modelle van groot belang was om `n akkurate aanduiding van die begin van staking te voorspel, en dat, vir die SUCC, die Matriks Deurvloei Metode oor die algemeen 'n bietjie meer akkuraat as die Stroomlyn Kromming Metode is. Daar is ook vasgestel dat die beste berekeningsrooster een is wat baie stroomlyne, en die kleinste moontlike getal quasi-ortogonale het, wat nie binne lemrye geplaas mag word nie. Die numeriese stabiliteit van beide die Matriks Deurvloei en die Stroomlyn Kromming Metode verbeter deur gebruik te maak van radiale vloeivermengingsmodelle, sonder om die akkuraatheid van voorspellings te benadeel. De Haller se metode was oorkonserwatief waar dit gebruik is om die staak-lyn vir transsoniese vloei toestande, maar meer nuttig in die subsoniese vloei gebied. Aungier se lemrymetode het akkurate resultate gelewer vir alle kompressors getoets, behalwe die Rofanco. Die diffusie faktor metode was oor die algemeen minder akuraat as Aungier se metode, maar meer akkuraat as de Haller se metode vir transsoniese toestande. Die stabiliteitsmetodes het almal ewe swak gevaar. Dit stem ooreen met die bevindings van vorige navorsing, wat bewys het dat hierdie metodes nie toepaslik is vir simulasies wat deurvloeimetodes gebruik nie. Aungier se grenslaagmetode het ook baie swak gevaar. Waarskynlik is dit as gevolg van tekortkomings in die grenslaagblokkasiemodel.
29
Camp, Timothy Richard. "Aspects of the off-design performance of axial flow compressors." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387517.
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30
Lavrich, Philip Lewis. "Time resolved measurements of rotating stall in axial flow compressors." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14567.
Full text
31
Kang, Chang. "Vaned recess anti-stall for axial-flow fans and compressors." Thesis, Cranfield University, 1996. http://dspace.lib.cranfield.ac.uk/handle/1826/9991.
Full textAbstract:
The study of anti-stall techniques for fans and compressors has never been more significant, since the potential applications were recognised in gas turbines, tunnel ventilation (jet fans) and industrial process where fans/compressors would benefit from the devices. This thesis will discuss the techniques achieving competitiveness by modifying the conventional casing design of the fan and compressor, which is referred to as casing treatments, taking into account the change of maximum efficiency and flow range. An experimental investigation to examine the influence of the vaned recess casing treatment on stall margin, operating efficiency and flow field of a low speed axial flow fan with aerospace type blade loading is presented. Different geometrical designs of the vaned passages were examined and more than 65% of stall margin improvements and over twice pressure rise with insignificant peak efficiency change were obtained. Experiments to examine the effect of casing treatments on the flow field were carried out using the same fan rig with a tip clearance of 1.2% of the blade height. A high frequency data acquisition system including both hardware and software was developed and the 3-D flow measurements with a slanted hot-wire were undertaken. The first detailed results of flow measurements associated with the vaned recess casing treatment are presented, including both time-averaged and ensemble-averaged measurement results. The flow features in both the solid casing and treated casing builds are captured and comparison between the builds presented. The results revealed that the stall margin improvement due to the casing treatment was not achieved by reducing the incidence nor by increasing the total pressure in the tip region. It appeared that the combined functions of elimination of the whirling flow, the removal of the randomness of the inlet flow and modification of the tip clearance flow are salient features associated with the mechanism of the treatment. The steady flow field of the test fan with various tip clearances has also been simulated in the rotating frame with computational fluid dynamics (CFD) to investigate the clearance effect on the end-wall flow development and to elucidate the behaviour of the tip leakage flow, and hopefully shed more light onto the flow phenomena involved.
32
Azimian, A. R. "Application of recess vaned casing treatment to axial flow compressors." Thesis, Cranfield University, 1987. http://dspace.lib.cranfield.ac.uk/handle/1826/10738.
Full textAbstract:
In axial flow compressors
and fans, the stable working range is
restricted by the so called stall line where operation may become
unstable and
simultaneously a short fall in compressor performance
appears.
Stall margin improvement has been a major task and experimental
observations over the last two decades have shown that modifying the
shape of the outer annulus wall, above the tips of rotor blades, is
effective in delaying the onset of stall to lower mass flow rates.
A wide variety of wall modifications or casing treatments have been
tried with a range of stall flow improvement which can amount to about
20% .(of the stalled flow)
An alternative technique for stall margin improvement in a single
stage axial flow machine has been studied and results will be
described in the present thesis. The technique for delaying stall
involves a large scale treatment to the outer casing of the compressor
which extends partly over and mainly upstream of the rotor.
The operating principle appears to be that as the flow is reduced
towards the stall point some radially unbalanced cells are transported
from the blade tips where they are collected in the treatment , turned
by the treatment vanes , and re-introduced to the main flow upstream
of the rotor.
A rotor with and without outlet stators has been tested ( and also
with and without casing treatment) over a range of speeds and flow
conditions.
Also the flow condition inside the recessed casing has been simulated
by means of an existing computer code known as PHOENICS.
33
Sun, J. "Modelling variable stator vane setting in multistage axial flow compressors." Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/11396.
Full textAbstract:
A numerical approach for modelling variable stator stagger in multistage stage
axial flow compressors is presented. The development of such an approach has been
motivated by the requirements of an optimisation methodology for stator vane setting
and active control of instability using controlled stator vane setting. The optimisation
methodology has been further developed but active control approaches are discussed
as future considerations.
Varying upstream stator vane stagger
.
changes the incident flow angle on
.
the
downstream rotor thus affecting the entire flow distribution within the compression
systems. The approach therefore begins by investigating the effect of a change in
stator stagger setting on stage performance. A meanline method was used for nu-
merical prediction of stage characteristics as it can simulate the effect of a change in
stagger settings and ( or) in rotational speeds. Overall compressor performance was
obtained by stacking the (experimental or predicted) stage characteristics and the
surge conditions predicted using a stage-by-stage dynamic compression model where
the compressibility was considered explicitly. This approach for variable stagger set-
ting was incorporated into a FORTRAN code and validated using the data from the
12-stage HP SPEY jTAY variable geometry compressor.
To optimise the setting, a direct search method incorporating a Sequential Weight
Increasing Factor Technique (SWIFT) algorithm was incorporated into the variable
stagger model. The objective function in this optimisation is penalised externally
11
with an
updated factor which helped to accelerate convergence. The methodology has
been incorporated into a FORTRAN program and its validations were conducted
using the data from the 7-stage LP OLYMPUS and the 12-stage HP SPEY /TAY
compressors. Results have demonstrated that variable stagger setting is a powerful
method to rematch stages and which can be used to improve the desired overall
performance, and that the potential benefits of introducing additional rows of variable
setting vanes can be achieved.
Future work arising from the present study has been discussed and highlighted,
which involves the enhancement of the model capacity and development of active
control approaches.
In addition the thesis involves several reviews focusing on different topics. Most
reviews contain considerable information and it is expected that the information can
be of help for the interested readers to trace more relevant references. These reviews
consist of a general review in chapter 1; a brief review on stage characteristics modelling in chapter 2; a comparative review on incompressible and compressible surge
models in chapter 3; a review of various optimisation methods for practical problems,
especially for constrained non-smooth problems, in chapter 4; and a review of the
state-of-the-art active approaches in chapter 7. The suitability of various approaches
has been highlighted. Steinke's meanline method is suitable for investigating the in-
influence of stagger resetting on stage performance. To predict the surge conditions for
a (high-speed) multistage environment, the stage-by-stage compressible models are
III
more promising. For constrained non-smoothed optimisation, the SWIFT algorithm
can be an alternative. The controlled stator vane regulated through nonlinear control
law will permit the robust control of compressor instabilities.
34
Sun, Jinju. "Modelling variable stator vane setting in multistage axial flow compressors." Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/11396.
Full textAbstract:
A numerical approach for modelling variable stator stagger in multistage stage axial flow compressors is presented. The development of such an approach has been motivated by the requirements of an optimisation methodology for stator vane setting and active control of instability using controlled stator vane setting. The optimisation methodology has been further developed but active control approaches are discussed as future considerations. Varying upstream stator vane stagger . changes the incident flow angle on . the downstream rotor thus affecting the entire flow distribution within the compression systems. The approach therefore begins by investigating the effect of a change in stator stagger setting on stage performance. A meanline method was used for nu- merical prediction of stage characteristics as it can simulate the effect of a change in stagger settings and ( or) in rotational speeds. Overall compressor performance was obtained by stacking the (experimental or predicted) stage characteristics and the surge conditions predicted using a stage-by-stage dynamic compression model where the compressibility was considered explicitly. This approach for variable stagger set- ting was incorporated into a FORTRAN code and validated using the data from the 12-stage HP SPEY jTAY variable geometry compressor. To optimise the setting, a direct search method incorporating a Sequential Weight Increasing Factor Technique (SWIFT) algorithm was incorporated into the variable stagger model. The objective function in this optimisation is penalised externally 11 with an updated factor which helped to accelerate convergence. The methodology has been incorporated into a FORTRAN program and its validations were conducted using the data from the 7-stage LP OLYMPUS and the 12-stage HP SPEY /TAY compressors. Results have demonstrated that variable stagger setting is a powerful method to rematch stages and which can be used to improve the desired overall performance, and that the potential benefits of introducing additional rows of variable setting vanes can be achieved. Future work arising from the present study has been discussed and highlighted, which involves the enhancement of the model capacity and development of active control approaches. In addition the thesis involves several reviews focusing on different topics. Most reviews contain considerable information and it is expected that the information can be of help for the interested readers to trace more relevant references. These reviews consist of a general review in chapter 1; a brief review on stage characteristics modelling in chapter 2; a comparative review on incompressible and compressible surge models in chapter 3; a review of various optimisation methods for practical problems, especially for constrained non-smooth problems, in chapter 4; and a review of the state-of-the-art active approaches in chapter 7. The suitability of various approaches has been highlighted. Steinke's meanline method is suitable for investigating the in- influence of stagger resetting on stage performance. To predict the surge conditions for a (high-speed) multistage environment, the stage-by-stage compressible models are III more promising. For constrained non-smoothed optimisation, the SWIFT algorithm can be an alternative. The controlled stator vane regulated through nonlinear control law will permit the robust control of compressor instabilities.
35
Krichene, Assaad. "Active identification and control of aerodynamic instabilities in axial and centrifugal compressors." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12062.
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36
Ozturk, Harun Kemal. "A computational study of flow and heat transfer in gas turbine axial compressor stator-wells." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388675.
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37
Russler, Patrick M. "An investigation of the surge behavior of a high-speed ten-stage axial flow compressor." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09192009-040554/.
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38
Muir, David E. (David Emerson) Carleton University Dissertation Engineering Mechanical. "Axial flow compressor modelling for engine health monitoring studies." Ottawa, 1988.
Find full text
39
Gorrell, Steven Ernest. "An experimental study of exit flow patterns in a multistage compressor in rotating stall." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-06102009-063018/.
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40
Lei, Vai-Man. "A simple criterion for three-dimensional flow separation in axial compressors." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37567.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.Includes bibliographical references (p. 104-106).
Most modem blade designs in axial-flow compressors diffuse the flow efficiently over 20% to 80% of blade span and it is the endwall regions that set the limits in compressor performance. This thesis addresses the estimation, control and mitigation of three-dimensional separation near the hub corner in axial- flow compressors. A simple method to estimate the onset of hub comer separation in compressor blade passages has been developed. A parameter is defined to quantify the combined effect of adverse pressure gradient and secondary flow which are the two main mechanisms contributing to the formation of three-dimensional flow separation. There is a critical value of the parameter at which the onset of three-dimensional flow separation occurs. Data from existing research and production compressors show the generality of the separation criterion. The new parameter captures the alleviating effect of boundary layer skew on three-dimensional flow separation. Using this concept, a flow control scheme has been developed to mitigate hub comer separation by injecting spanwise momentum from the blade suction surface. A proof of concept flow control experiment demonstrates a reduction in stagnation pressure loss coefficient of 8% with an injection flow of 0.8% of the cascade mass flow.
by Vai-Man Lei.
Ph.D.
41
Heinlein, Gregory S. "Aerodynamic Behavior of Axial Flow Turbomachinery Operating in Transient Transonic Flow Regimes." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1573149943024303.
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42
Van, Antwerpen Werner. "Multi-quadrant performance simulation for subsonic axial flow compressors / Werner van Antwerpen." Thesis, North-West University, 2007. http://hdl.handle.net/10394/1271.
Full textAbstract:
The emergence of closed-loop Brayton cycle power plants, such as the PBMR, resulted in the
need to simulate start-up transients for industrial multi-stage axial flow compressors operating at
subsonic conditions. This implies that the delivery pressure and power requirements must be
predicted for different mass flow rates and rotational speeds while operating in the first and fourth
quadrants on the compressor performance charts.
Therefore, an analytical performance prediction model for subsonic multi-stage axial flow
compressors had to be developed that can be integrated into a generic network analysis software
code such as Flownex. For this purpose, performance calculations based on one-dimensional
mean-line analysis demonstrated good accuracy, provided that the correct models for losses,
incidence and deviation are used. Such a model is therefore the focus of this study.
A preliminary analytical performance prediction code, with the capability of interchanging between
different deviation and loss models is presented. Reasonably complex loss models are
integrated in association with the correct incidence and deviation models in a software package
called "Engineering Equation Solver" (EES). The total pressure loss calculations are based on a
superposition of theoretically separable loss components that include the following: blade profile
losses, secondary losses and annulus losses. The fundamental conservation equations for
mass, momentum and energy for compressible "rotating pipe" flow were implemented into the
performance prediction code. Performance prediction models were validated against
experimental data and evaluated according to their ease of implementation. Verification was
done by comparing simulation results with experimental work done by Von Backstrom. This
includes a calculation to determine the uncertainty in the experimental results.
Furthermore, since the conventional definition of isentropic efficiency breaks down at the
boundaries of quadrants on the performance charts, a new non-dimensional power formulation is
presented that allows for the calculation of the compressor power in all of the relevant quadrants.
Good comparison was found between simulation results and measurements in the first and fourth
quadrant of operation.Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2007.
43
Gysling, Daniel Lawrence. "Dynamic control of rotating stall in axial flow compressors using aeromechanical feedback." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12455.
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44
Tomita, Jesuino Takachi. "Three-dimensional flow calculations of axial compressors and turbines using CFD techniques." Instituto Tecnológico de Aeronáutica, 2009. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=753.
Full textAbstract:
With the advent of powerful computer hardware, Computational Fluid Dynamics (CFD) has been vastly used by researches and scientists to investigate flow behavior and its properties. The cost of CFD simulation is very small compared to the experimental arsenal as test facilities and wind-tunnels. In the last years many CFD commercial packages were developed and some of them possess prominence in industry and academia. However, some specific CFD calculations are particular cases and sometimes need special attention due to the complexity of the flow. In these cases, meticulous research becomes necessary. This is the case of turbomachinery flow calculations. The development of CFD codes applied to turbomachinery flow simulations and its implementation issues are not available. A few institutions have this type of knowledge. Each CFD code has its particularities. Developing a CFD code is very interest subject in academia. In this work, a computational code, written in FORTRAN, was developed to calculate internal flows in turbomachines using CFD techniques. The solver is capable of calculating the three-dimensional flows not only for turbomachines. For instance, internal and external flows of nozzles and airfoils can be calculated. The approach used allows the use of unstructured meshes of hexahedral elements. Euler, Navier-Stokes and turbulent equations can be calculated depending on the user settings. Diferent numerical schemes were implemented for time and space integration. Numerical tools to improve the stability and to increase the time-step (local time-step and implicit residual smoothing) were also implemented and all details are described in this work. The origin of this solver is to simulate flows in compressors and turbines. Therefore, both rotating and nonrotating frames of reference are calculated simultaneously. Hence, the verification and validation processes were run for both inertial and non-inertial systems. A step-by-step design procedure is presented in this work. It is very important to mention that to have a complete understanding of the flow physics in compressors and turbines the designer must have a solid knowledge of the operation of gas turbine components.
45
Ando, Victor Fujii. "Genetic algorithm for preliminary design optimisation of high-performance axial-flow compressors." Instituto Tecnológico de Aeronáutica, 2011. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=1969.
Full textAbstract:
This work presents an approach to optimise the preliminary design of high-performance axial-flow compressors. The preliminary design within the Gas Turbine Group at ITA, is carried on with an in-house computational program based upon the streamline curvature method, using correlations from the literature to assess the losses. The choice of many parameters of the thermodynamic cycle and of geometries relies upon the expertise from the members of the Group. Nevertheless, it is still a laborious and time-consuming task, requiring successive trial and errors. Therefore, to support the compressor designer in the choice of some parameters, an optimisation program, named REMOGA, was written in FORTRAN language, allowing an easy integration with the programs developed by the Gas Turbine Group. The program is based upon a multi-objective genetic algorithm, with real codification and elitism. Then the REMOGA and the preliminary design program were integrated to design a 5-stage axial-flow compressor. Therefore, the stator air outlet angles, the temperature distribution and the hub-tip ratio were varied aiming at higher efficiencies and higher pressure ratios, but controlling the de Haller number and the camber angle. Thanks to the REMOGA, thousands of designs could be quickly evaluated. Finally, using a choice criterion, four solutions were selected for further analysis, revealing that the developed program was successful in finding more efficient and feasible compressor designs.
46
Piatt, Donald R. "Development of a geometric model for the study of propagating stall inception based on flow visualization in a linear cascade." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/76198.
Full textAbstract:
Flow visualization movies of flow through a cascade of compressor blades showed propagating stall at stagger angles of 36.5 and 45 degrees for angles of attack of 20 degrees and higher. At a stagger angle of 25 degrees, the development of a steady, separated boundary layer occurred with no propagation. The observed propagating stall process was the development of a vortex in the boundary layer and its subsequent shedding. The shedding mechanism was observed to be the interference by the reverse flow from the previously stalled passage with the vortex flow in the stalled passage. This dissipated the vortex in the blade passage and the incoming flow then flushed the stagnated vortex out of the passage.
Measurements of propagation speeds showed that the propagation speed is related to the blockage of the passage, that stagger angle has an insignificant effect on propagation speed, and that propagation speed is proportional to the relative velocity.
Based on the observations, a geometric model was developed to predict the onset of propagating stall. This model showed that increased solidity, decreased stagger angles, and operation at low angles of attack make a cascade more resistant to propagating stall inception. The model shows the relation of the operating point of a compressor to the stall inception point. When expanded to include all significant aspects of blade geometry, the model may provide a basis for controlling propagating, and hence, rotating, stall inception based on the blade row·geometry.Master of Science
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Escuret, Jean-Francois. "The prediction and active control of surge in multi-stage axial-flow compressors." Thesis, Cranfield University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333133.
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48
Stein, Alexander. "Computational analysis of stall and separation control in centrifugal compressors." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/11884.
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49
Olsen, Timothy L. "Experimental investigation of unsteady fan flow interaction with downstream struts." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/104523.
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50
Thomas, Keegan D. "Blade row and blockage modelling in an axial compressor throughflow code." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/1870.
Full textAbstract:
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2005.The objective of the thesis is to improve the performance prediction of axial compressors, using a streamline throughflow method (STFM) code by modelling the hub and casing wall boundary layers, and additional flow mechanisms that occur within a blade row passage. Blade row total pressure loss and deviation correlations are reviewed. The effect of Mach number and the blade tip clearance gap are also reviewed as additional loss sources. An entrainment integral method is introduced to model the hub and casing wall boundary layers. Various 1-dimensional test cases are performed before implementing the integral boundary layer method into the STFM. The boundary layers represent an area blockage throughout the compressor, similar to a displacement thickness, but affects two velocity components. This effectively reduces the compressor flow area by altering the hub and casing radial positions at all stations. The results from the final STFM code with the integral boundary layer model, Mach number model and tip clearance model is compared against high pressure ratio compressor test cases. The blockage results, individual blade row and overall performance results are compared with published data. The deviation angle curve fits developed by Roos and Aungier are compared. There is good agreement for all parameters, except for the slope of deviation angle with incidence angle for low solidity. For the three compressors modelled, there is good agreement between the blockage prediction obtained and the blockage prediction of Aungier. The NACA 5-stage transonic compressor overall performance shows good agreement at all speeds, except for 90% of design speed. The NACA 10-stage subsonic compressor shows good agreement for low and medium speeds, but needs improvement at 90% and 100% of design speeds. The NACA 8-stage transonic compressor results compared well only at low speeds.