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1
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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2
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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3
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.
4
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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5
McGlumphy, Jonathan. "Numerical Investigation of Subsonic Axial-Flow Tandem Airfoils for a Core Compressor Rotor." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26039.
Full textAbstract:
The tandem airfoil has potential to do more work as a compressor blade than a single airfoil without incurring significantly higher losses. Although tandem blades are sometimes employed as stators, they have not been used in any known commercial rotors. The goal of this work is to evaluate the aerodynamic feasibility of using a tandem rotor in the rear stages of a core compressor. As such, the results are constrained to shock-free, fully turbulent flow. The work is divided into 2-D and 3-D simulations. The 3-D results are subject to an additional constraint: thick endwall boundary layers at the inlet.
Existing literature data on tandem airfoils in 2-D rectilinear cascades have been compiled and presented in a Lieblein loss versus loading correlation. Large scatter in the data gave motivation to conduct an extensive 2-D CFD study evaluating the overall performance as a function of the relative positions of the forward and aft airfoils. CFD results were consistent with trends in the open literature, both of which indicate that a properly designed tandem airfoil can outperform a comparable single airfoil on- and off-design. The general agreement of the CFD and literature data serves as a validation for the computational approach.
A high hub-to-tip ratio 3-D blade geometry was developed based upon the best-case tandem airfoil configuration from the 2-D study. The 3-D tandem rotor was simulated in isolation in order to scrutinize the fluid mechanisms of the rotor, which had not previously been well documented. A geometrically similar single blade rotor was also simulated under the same conditions for a baseline comparison. The tandem rotor was found to outperform its single blade counterpart by attaining a higher work coefficient, polytropic efficiency and numerical stall margin. An examination of the tandem rotor fluid mechanics revealed that the forward blade acts in a similar manner to a conventional rotor. The aft blade is strongly dependent upon the flow it receives from the forward blade, and tends to be more three-dimensional and non-uniform than the forward blade.Ph. D.
6
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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7
Lyes, Peter A. "Low speed axial compressor design and evaluation : High speed representation and endwall flow control studies." Thesis, Cranfield University, 1999. http://hdl.handle.net/1826/4251.
Full textAbstract:
This Thesis reports the design, build and test of two sets of blading for the
Cranfield University low speed research compressor. The first of these was a datum low
speed design based on the fourth stage of the DERA high speed research compressor
C 147. The emphasis of this datum design was on the high-to-low speed transformation
process and the evaluation of such a process through comparing detailed flow
measurements from both compressors.
Area traverse measurements in both the stationary and rotating frame of reference
were taken at Cranfield along with overall performance, blade surface static pressure and
flow visualisation measurements. These compare favourably with traverse and
performance measurements taken on C147 before commencement of the PhD work.
They show that despite the compromises made during the transformation process, due to
both geometric and aerodynamic considerations, both the primary and secondary flow
features can be successfully reproduced in the low speed environment.
The aim of the second design was to improve on the performance of the datum
blading through the use of advanced '3D' design concepts such as lean and sweep. The
blading used nominally the same blade sections as the datum, and parametric studies
were conducted into various lean/sweep configurations to try to optimise the blade
performance. The final blade geometry also incorporated leading edge recambering
towards the fixed endwalls of both the rotor and stator. The '3D' blading demonstrated a
1.5% increase in efficiency (over the datum blading) at design flow rising to around 3%
at near stall along with an improvement in stall margin and pressure rise characteristic.
The design work was completed using the TRANSCode flow solver for both the
blade-to-blade solutions (used in the SI-S2 datum design calculation) and the fully 3D
solutions (for the advanced design and post datum design appraisal). The 3D solutions
gave a reasonable representation of the mid-span and main 3D flow features but failed to
model the corner and tip clearance flow accurately. An interesting feature of the low
speed flowfield was the circumferential variation in total pressure observed at exit from
all rotors for both designs. This was not present at high speed and represents one of the
main differences between the high and low speed flow. Unsteady modelling of mid-
height sections from the first stage indicate that part of this variation is due to the
potential interaction of the rotor with the downstream stator while the remainder is due
to the wake structure from the upstream stator convecting through the rotor passage.
Finally, the implications for a high speed design based on the success of the 3D low
speed design are considered.
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
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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10
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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11
Power, Bronwyn. "Aspirated compressors." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648363.
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12
Nucara, Pascal. "Design of gas turbine axial compressors for fuel flexibility." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/48905/.
Full textAbstract:
Current gas turbine technology for power generation is generally optimised for natural gas. On the basis of current instabilities in natural gas price and supply, the use of alternative fuels, such as syngas, has recently gained high interest. Due to the different thermodynamic properties of syngas compared to natural gas the behaviour of existing gas turbine components may significantly change. From practical and economic points of view, it is generally considered that in order to meet the new fuel properties, the main effort should be put on the adaptation of conventional gas turbines in integrated gasification combined cycle (IGCC) plants rather than producing a new generation of gas turbine designs from scratch. In addition to the requirement of new combustion technologies, main critical issues are represented by the reduction of compressor surge margin and turbine blade overheating. Solutions might include thermodynamic cycle as well as turbine geometry modifications. The latter would be preferred in terms of power plant performance. The main aim of this thesis is to explore suitable solutions to be applied to gas turbine compressors in order to accommodate syngas combustion. Among others, the use of variable stator vanes (VSVs) and blade radial stacking line modifications are considered. These are investigated on reference geometries available in the public domain. A baseline compressor geometry representative of a conventional heavy-duty gas turbine fueled with natural gas is generated and modified according to the understating gained during this study. The re-designed machine is a result of the application of stator vanes re-staggering in the front stages and blade sweep in the rear stages in order to cope with compressor air supply control and critical flow separation regions respectively. The obtained results show that efficient and stable operation during power modulation can be achieved, while reducing the need of other modifications to the combined cycle plant. It was therefore concluded that the proposed option can be considered a viable option to satisfy some important technical and economic constraints imposed by the integration of an existing gas turbine within an IGCC plant.
13
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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14
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.
15
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.
16
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.
17
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.
18
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.
19
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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20
Baker, Jonathan D. "Analysis of the sensitivity of multi-stage axial compressors to fouling at various stages." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Sep%5FBaker.pdf.
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21
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.
22
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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23
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.
24
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.
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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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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.
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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.
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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.
29
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.
30
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.
31
Muir, David E. (David Emerson) Carleton University Dissertation Engineering Mechanical. "Axial flow compressor modelling for engine health monitoring studies." Ottawa, 1988.
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32
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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Khan, Jobaidur Rahman. "Fog Cooling, Wet Compression and Droplet Dynamics In Gas Turbine Compressors." ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/908.
Full textAbstract:
During hot days, gas turbine power output deteriorates significantly. Among various means to augment gas turbine output, inlet air fog cooling is considered as the simplest and most costeffective method. During fog cooling, water is atomized to micro-scaled droplets and introduced into the inlet airflow. In addition to cooling the inlet air, overspray can further enhance output power by intercooling the compressor. However, there are concerns that the water droplets might damage the compressor blades and increased mass might cause potential compressor operation instability due to reduced safety margin. Furthermore, the two-phase flow thermodynamics during wet compression in a rotating system has not been fully established, so continued research and development in wet compression theory and prediction model are required. The objective of this research is to improve existing wet compression theory and associated models to accurately predict the compressor and the entire gas turbine system performance for the application of gas turbine inlet fog cooling. The following achievements have been accomplished: (a) At the system level, a global gas turbine inlet fog cooling theory and algorithm have been developed and a system performance code, FogGT, has been written according to the developed theory. (b) At the component level, a stage-stacking wet compression theory in the compressor has been developed with known airfoil configurations. (c) Both equilibrium and non-equilibrium water droplet thermal-fluid dynamic models have been developed including droplet drag forces, evaporation rate, breakup and coalescence. A liquid erosion model has also been developed and incorporated. (d) Model for using computational fluid dynamics (CFD) code has been developed to simulate multiphase wet compression in the rotating compressor stage. In addition, with the continued increase in volatility of natural gas prices as well as concerns regarding national energy security, this research has also investigated employing inlet fogging to gas turbine system fired with alternative fuels such as low calorific value synthetic gases. The key results include discovering that the saturated fogging can reduce compressor power consumption, but overspray, against conventional intuition, actually increases compressor power. Nevertheless, inlet fogging does increase overall net power output.
34
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.
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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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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.
37
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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38
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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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.
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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.
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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.
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Ng, Sin Yuan. "Gas-liquid separation using axial flow cyclones." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419640.
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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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Gill, Andrew. "Four quadrant axial flow compressor performance." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20075.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The aims of this thesis are to identify all possible modes of operaton for a multi-stage axial flow compressor; then to characterise the performance, attempt to numerically model operation, and determine the main flow field features for each mode. Four quadrant axial flow compressor operation occurs when the direction of flow through the compressor or the sign of the pressure difference across the compressor reverses, or any combination of these. Depending on the direction of rotation of the compressor, six modes of operation are possible in the four quadrants of the performance map. The rotor rotates in the design direction for three modes, and in the opposite direction for the other three. The stationary-rotor pressure characteristic is S-shaped and passes through the second and fourth quadrants. A three-stage axial flow compressor operating in the incompressible flow regime was used for the experimental investigation. Flow through the compressor was reversed or augmented by means of an auxiliary axial flow fan. Compressor performance was measured by means of static pressure tappings, a turbine anemometer calibrated to measure forward and reversed volumetric flow and a load cell for torque measurement. The inter-blade row flow fields were measured with pneumatic probes and 50 μm cylindrical hot film probes. Three dimensional single blade-passage Navier-Stokes simulations were performed using the Numeca FineTurbo package. Steady state simulations used a mixing plane approach. A nonlinear harmonic approximation was used for time-unsteady simulations. Unstalled first quadrant operation was unremarkable, and good agreement was obtained between experimental and numerical data. A single stall cell was detected experimentally during stalled operation, which was not modelled numerically. In the fourth quadrant for positive rotation, (windmilling), the compressor acts as an inefficient turbine. Flow separates from the pressure surface of the blade, rendering the steady-state mixing plane approach unsuitable. The performance characteristic curves for second quadrant for positive rotation, are discontinuous with those of first quadrant operation. The temperature rise in the working fluid is significantly higher than at design point. Periodic flow structures occurring across two blade passages were detected at all flow coefficients investigated, invalidating numerical modelling assumptions. Better agreement was obtained between experimental and numerical data from a case found in literature. If the compressor operates as a compressor in reverse (third quadrant operation), significant separation occurs on the pressure surface of all blades, and flow conditions resemble severe first quadrant stall. Separation becomes less severe at larger flow rates, allowing numerical simulation, though this is sensitive to the initial flow field. In the the part of the second quadrant, where the compressor rotates in reverse, it operates as a turbine. The blade angles and the direction of curvature match the flow angles and turning well, leading to high turbine efficiencies. Numerical simulations yielded good agreement with measured results, but were again sensitive to the initial flow field. Fourth quadrant operation with negative rotation occurs when flow is forced through the compressor in the design direction. Large separation bubbles are attached to the pressure surfaces of rotor and stator blades, so virtually all throughflow occurs near the hub and casing
AFRIKAANSE OPSOMMING: Die doelwitte van hierdie tesis is om al die moontlike werkmodusse vir ’n bestaande multi-stadium aksiaalvloei kompressor uit te ken; om dan die gedrag te gekarakteriseer, ’n poging aan te wend om die werking numeries te modelleer, en die belangrikste vloeiveldkenmerke vir elke modus te bepaal. Vier-kwadrant aksiaalvloei kompressor werking vind plaas as die rigting van die vloei deur die kompressor, of die teken van die drukverskil oor die kompressor omkeer, of enige kombinasie daarvan. Afhangende van die rigting van rotasie van die kompressor is ses operasionele modusse moontlik in die vier kwadrante van die kompressorkaart. Die rotor draai in die ontwerprigting vir drie van die modes, en in die teenoorgestelde rigting vir die ander drie. Die stilstaande-rotor drukkarakteristiek is S-vormig gaan deur die tweede en vierde kwadrante. ’n Drie-stadium onsamedrukbare vloei aksiaalvloei kompressor is vir die eksperimentele ondersoek gebruik. Vloei deur die kompressor is omgekeer of aangehelp deur middel van ’n aksiaalvloei hulpwaaier. Kompressor werking is gemeet deur middel van statiese druk meetpunte in die omhulsel, ’n turbine anemometer wat gekalibreer is om vorentoe en omgekeerde volumetriese vloei te meet, en ’n lassel vir wringmoment meting. Interlemryvloeivelde is opgemeet met pneumatiese sensors en 50-μm silindriese warm film sensors. Drie-dimensionele Navier-Stokes simulasies is uitgevoer vir ’n enkele lem van elke lemry, met behulp van die Numeca FineTurbo sagtewarepakket. ’n Mengvlakbenadering is gebruik vir bestendige toestand simulasies, terwyl ’n nie-linere harmoniese benadering gebruik is vir die tyd-afhanklike simulasies. Ongestaakte eerste kwadrant werking was alledaags, en goeie ooreenkoms is gevind tussen die eksperimentele en numeriese data. ’n Enkele staak-sel is eksperimenteel ontdek tydens gestaakte werking. Gestaakte werking is nie numeries gemodelleer nie. In die vierde kwadrant vir positiewe rotasie, (”windmeulwerking”), werk die kompressor as ’n ondoeltreffende turbine. Vloei-wegbrekinging op die lem drukoppervlaktes maak die bestendige toestand mengvlakbenadering ongeskik. In die kenlyne vir tweede kwadrant positiewe rotasie, is daar ’n diskontinu¨ıteit in die prestasie karakteristiekkrommes vir die eerste en tweede kwadrant werking. Die temperatuurstyging in die werk- vloeistof is beduidend ho¨er as as by die ontwerppunt. Periodiese vloeistrukture wat oor twee lemme plaasvind is gevind by alle vloei ko¨effisi¨ente wat ondersoek is, en dit maak die numeriese modellering aannames ongeldig. Beter ooreenkoms tussen die eksperimentele en numeriese data iss verkry met ’n geval wat uit die literatuur gevind is. Indien die kompressor werk as ’n kompressor in omgekeerde (derde kwadrant weking), vind beduidende wegbreking op die drukoppervlak van al die lemme plaas, wat lyk soos ernstige gestaakte eerste kwadrant werking. Die vloeiskeiding raak minder ernstig by ’n groter vloeitempo, wat numeriese nabootsing toelaat, maar die nabootsings is sensitief vir die aanvanklike vloeiveld. In die tweede kwadrant, by omgekeerde rotasie, werk die kompressor as ’n turbine. Die lemhoeke en die rigting van lemkromming stem ooreen met die vloeihoeke en verwringing, wat lei tot ho¨er turbine doeltreffendheid. Numeriese nabootsings stem goed ooreen met gemete resultate, maar is weereens sensitief vir die keuse van die aanvanklike vloeiveld. Vierde kwadrant werking met negatiewe rotasie vind plaas wanneer die lug gedwing word om deur die kompressor in die ontwerprigting te vloei. Groot skeidingborrels sit vas aan die drukoppervlaktes van alle lemme, sodat meeste deurvloei naby die naaf en die omhulsel plaas vind.
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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.
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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.
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Alhajeri, Hamad. "Heat removal in axial flow high pressure gas turbine." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/11465.
Full textAbstract:
The demand for high power in aircraft gas turbine engines as well as
industrial gas turbine prime mover promotes increasing the turbine entry
temperature, the mass flow rate and the overall pressure ratio. High
turbine entry temperature is however the most convenient way to increase
the thrust without requiring a large change in the engine size.
This research is focused on improving the internal cooling of high pressure
turbine blade by investigating a range of solutions that can contribute to
the more effective removal of heat when compared with existing
configuration. The role played by the shape of the internal blade passages
is investigated with numerical methods. In addition, the application of mist
air as a means of enhanced heat removal is studied.
The research covers three main area of investigation. The first one is
concerned with the supply of mist on to the coolant flow as a mean to
enhancing heat transfer. The second area of investigation is the
manipulation of the secondary flow through cross-section variation as a
means to augment heat transfer. Lastly a combination of a number of
geometrical features in the passage is investigated.
A promising technique to significantly improve heat transfer is to inject
liquid droplets into the coolant flow. The droplets which will evaporate after
travelling a certain distance, act as a cooling sink which consequently
promote added heat removal. Due to the promising results of mist cooling
in the literature, this research investigated its effect on a roughened
cooling passage with five levels of mist mass percentages.
In order to validate the numerical model, two stages were carried out.
First, one single-phase flow case was validated against experimental
results available in the open literature. Analysing the effect of the rotational
force, on both flow physics and heat transfer, on the ribbed channel was
the main concern of this investigation. Furthermore, the computational results using mist injection were also validated against the experimental
results available in the literature.
Injection of mist in the coolant flow helped achieve up to a 300% increase
in the average flow temperature of the stream, therefore in extracting
significantly more heat from the wall. The Nusselt number increased by
97% for the rotating leading edge at 5% mist injection.
In the case of air only, the heat transfers decrease in the second passage,
while in the mist case, the heat transfer tends to increase in the second
passage. Heat transfer increases quasi linearly with the increase of the
mist percentage when there is no rotation. However, in the presence of
rotation, the heat transfers increase with an increase in mist content up to
4%, thereafter the heat transfer whilst still rising does so more gradually.
The second part of this research studies the effect of non-uniform cross-
section on the secondary flow and heat transfer in order to identify a
preferential design for the blade cooling internal passage. Four different
cross-sections were investigated. All cases start with square cross-section
which then change all the way until it reaches the 180 degree turn before it
changes back to square cross-section at the outlet. All cases were
simulated at four different speeds. At low speeds the rectangle and
trapezoidal cross-section achieved high heat transfer. At high speed the
pentagonal and rectangular cross-sections achieved high heat transfer.
Pressure loss is accounted for while making use of the thermal
performance factor parameter which accounts for both heat transfer and
pressure loss. The pentagonal cross-section showed high potential in
terms of the thermal performance factor with a value over 0.8 and higher
by 33% when compared to the rectangular case.
In the final section multiple enhancement techniques are combined in the
sudden expansion case, such as, ribs, slots and ribbed slot. The maximum
heat enhancement is achieved once all previous techniques are used
together. Under these circumstances the Nusselt number increased by
60% in the proposed new design.
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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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Baiense, Jr Joao C. "Vortex Generator Jet Flow Control in Highly Loaded Compressors." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-theses/916.
Full textAbstract:
"A flow control method for minimizing losses in a highly loaded compressor blade was analyzed. Passive and active flow control experiments with vortex generator jets were conducted on a seven blade linear compressor cascade to demonstrate the potential application of passive flow control on a highly loaded blade. Passive flow control vortex generator jets use the pressure distribution generated by air flow over the blade profile to drive jets from the pressure side to the suction side. Active flow control was analyzed by pressuring the blade plenum with an auxiliary compressor unit. Active flow control decreased profile losses by approximately 37 % while passive flow control had negligible impact on the profile loss of a highly loaded blade. Passive flow control was able to achieve a jet velocity ratio, jet velocity to upstream velocity, of 0.525. The success of active flow control with a velocity ratio of 0.9 suggests there is potential for passive flow control to be effective. The research presented in this thesis is motivated by the potential savings in the applications of passive flow control in gas turbine axial compressors by increasing the aerodynamic load of each stage. Increased stage loading that is properly controlled can reduce the number of stages required to achieve the desired pressure compression ratio."
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Dickson, Philip James. "Gas liquid separation within a novel axial flow cyclone separator." Thesis, Cranfield University, 1998. http://hdl.handle.net/1826/3999.
Full textAbstract:
Cyclone separators have been described in detail and, although substantial research has been
performed on solid / gas devices, the use of cyclones for gas / liquid separation has been
comparatively ignored; this is particularly true for higher concentrations of liquid and for
degassing applications. Consequently no generic models are available which will predict
separation efficiency or pressure drop for all designs of cyclone.
A novel design of axial flow cyclone called WELLSEP was examined for the purpose of
degassing. This design was not believed to be optimal and no design criteria or performance
prediction models were available for it. An experimental programme was therefore produced
and executed to investigate changes in geometry and the affect of fluid dynamics. Changes to
the length, vortex finder and swirl generator were examined first and then one design was
selected and tested over a number of liquid flow rates, Gas Void Fractions (GVFs) and liquid
extractions.
Data was collected from the experiments which assisted in the development of semi-empirical
models for the prediction of pressure drop and separation efficiency. These models could be
used in the design of WELLSEP.
Geometric and fluid dynamics changes have both been shown to influence the performance of
the tested cyclone. The principal conclusions that have been drawn from this research are:
" Of the tested designs, the design based upon a 30mm vortex finder diameter, settling
chamber length of three times the diameter of the cyclone and a four start helix gave the
optimum separation efficiency over the greatest range of conditions.
0 The separation efficiency is affected by the superficial liquid velocity and the liquid
extraction but not the GVF.
" The dimensionless pressure drop coefficient (Euler number) is a function of liquid
extraction and GVF. It may also be a function of the superficial liquid velocity but it is unproven by this research.