Academic literature on the topic 'Combustor-diffuser system'
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Journal articles on the topic "Combustor-diffuser system"
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Karki, K. C., V. L. Oechsle, and H. C. Mongia. "A Computational Procedure for Diffuser-Combustor Flow Interaction Analysis." Journal of Engineering for Gas Turbines and Power 114, no. 1 (January 1, 1992): 1–7. http://dx.doi.org/10.1115/1.2906301.
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This paper describes a diffuser-combustor flow interaction analysis procedure for gas turbine combustion systems. The method is based on the solution of the Navier–Stokes equations in a generalized nonorthogonal coordinate system. The turbulence effects are modeled via the standard two-equation (k-ε) model. The method has been applied to a practical gas turbine combustor-diffuser system that includes support struts and fuel nozzles. Results have been presented for a three-dimensional simulation, as well as for a simplified axisymmetric simulation. The flow exhibits significant three-dimensional behavior. The axisymmetric simulation is shown to predict the static pressure recovery and the total pressure losses reasonably well.
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Carrotte, J. F., D. W. Bailey, and C. W. Frodsham. "Detailed Measurements on a Modern Combustor Dump Diffuser System." Journal of Engineering for Gas Turbines and Power 117, no. 4 (October 1, 1995): 678–85. http://dx.doi.org/10.1115/1.2815453.
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An experimental investigation has been carried out to determine the flow characteristics and aerodynamic performance of a modern gas turbine combustor dump diffuser. The system comprised a straight walled prediffuser, of area ratio 1.35, which projected into a dump cavity where the flow divided to pass either into the flame tube or surrounding feed annuli. In addition, a limited amount of air was removed to simulate flow used for turbine cooling. The flame tube was relatively deep, having a radial depth 5.5 times that of the passage height at prediffuser inlet, and incorporated burner feed arms, cowl head porosity, cooling rings, and primary ports. Representative inlet conditions to the diffuser system were generated by a single-stage axial flow compressor. Results are presented for the datum configuration, and for a further three geometries in which the distance between prediffuser exit and the head of the flame tube (i.e., dump gap) was reduced. Relatively high values of stagnation pressure loss were indicated, with further significant increases occurring at smaller dump gaps. These high losses, which suggest a correlation with other published data, are due to the relatively deep flame tube and short diffuser length. Furthermore, the results also focus attention on how the presence of a small degree of diffuser inlet swirl, typical of that which may be found within a gas turbine engine, can result in large swirl angles being generated farther downstream around the flame tube. This is particularly true for flow passing to the inner annulus.
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Agrawal, A. K., J. S. Kapat, and T. T. Yang. "An Experimental/Computational Study of Airflow in the Combustor–Diffuser System of a Gas Turbine for Power Generation." Journal of Engineering for Gas Turbines and Power 120, no. 1 (January 1, 1998): 24–33. http://dx.doi.org/10.1115/1.2818084.
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This paper presents an experimental/computational study of cold flow in the combustor–diffuser system of industrial gas turbines employing can-annular combustors and impingement-cooled transition pieces. The primary objectives were to determine flow interactions between the prediffuser and dump chamber, to evaluate circumferential flow nonuniformities around transition pieces and combustors, and to identify the pressure loss mechanisms. Flow experiments were conducted in an approximately one-third geometric scale, 360-deg annular test model simulating practical details of the prototype including the support struts, transition pieces, impingement sleeves, and can-annular combustors. Wall static pressures and velocity profiles were measured at selected locations in the test model. A three-dimensional computational fluid dynamic analysis employing a multidomain procedure was performed to supplement the flow measurements. The complex geometric features of the test model were included in the analysis. The measured data correlated well with the computations. The results revealed strong interactions between the prediffuser and dump chamber flows. The prediffuser exit flow was distorted, indicating that the uniform exit conditions typically assumed in the diffuser design were violated. The pressure varied circumferentially around the combustor casing and impingement sleeve. The circumferential flow nonuniformities increased toward the inlet of the turbine expander. A venturi effect causing flow to accelerate and decelerate in the dump chamber was also identified. This venturi effect could adversely affect impingement cooling of the transition piece in the prototype. The dump chamber contained several recirculation regions contributing to the losses. Approximately 1.2 dynamic head at the prediffuser inlet was lost in the combustor–diffuser, much of it in the dump chamber where the fluid passed though narrow pathways. A realistic test model and three-dimensional analysis used in this study provided new insight into the flow characteristics of practical combustor–diffuser systems.
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Antas, Stanisław. "Exhaust System for Radial and Axial-Centrifugal Compressor with Pipe Diffuser." International Journal of Turbo & Jet-Engines 36, no. 3 (August 27, 2019): 297–304. http://dx.doi.org/10.1515/tjj-2016-0068.
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Abstract The application of radial and axial-centrifugal compressors in turboprop, turboshaft and turbofan engines may require the construction of small diameters diffuser in order to obtain lower weight and smaller frontal area. Conventional exhaust diffusers typically have large outlet diameters for exit Mach numbers lower than 0,2 and low swirl flow to the combustor, hence the design of channel of the low-diameter diffusers called controlled-contour, fishtail-shaped diffuser or diffusing trumpet is complex. The cross-sectional shape of these channels is varied from circular to oval to elliptic and to rectangular. The paper presents an original method for determining the flow parameters in the channel and at the outlet section of the downstream diffusing trumpet for a pipe diffuser, which constitutes the downstream duct of the radial or axial-centrifugal compressor with the pipe diffuser. It also illustrates a new method for determining the geometrical parameters of the diffuser. Mentioned methods (for conceptual design of a compressor with pipe diffuser) are based on Pythagorean theorem, properties of ellipse, equation of continuity, energy equation, first law of thermodynamics, Euler’s moment of momentum equation, gasdynamics functions and definitions used in theory of turbo-machines.
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Walker, A. Duncan, Paul A. Denman, and James J. McGuirk. "Experimental and Computational Study of Hybrid Diffusers for Gas Turbine Combustors." Journal of Engineering for Gas Turbines and Power 126, no. 4 (October 1, 2004): 717–25. http://dx.doi.org/10.1115/1.1772403.
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The increasing radial depth of modern combustors poses a particularly difficult aerodynamic challenge for the pre-diffuser. Conventional diffuser systems have a finite limit to the diffusion that can be achieved in a given length and it is, therefore, necessary for designers to consider more radical and unconventional diffuser configurations. This paper will report on one such unconventional diffuser; the hybrid diffuser which, under the action of bleed, has been shown to achieve high rates of diffusion in relatively short lengths. However, previous studies have not been conducted under representative conditions and have failed to provide a complete description of the relevant flow mechanisms making optimization difficult. Utilizing an isothermal representation of a modern gas turbine combustor an experimental investigation was undertaken to study the performance of a hybrid diffuser compared to that of a conventional, single-passage, dump diffuser system. The hybrid diffuser achieved a 53% increase in area ratio within the same axial length generating a 13% increase in the pre-diffuser static pressure recovery coefficient which, in turn, produced a 25% reduction in the combustor feed annulus total pressure loss coefficient. A computational investigation was also undertaken in order to investigate the governing flow mechanisms. A detailed examination of the flow field, including an analysis of the terms within the momentum equation, demonstrated that the controlling flow mechanisms were not simply a boundary layer bleed but involve a more complex interaction between the accelerating bleed flow and the diffusing mainstream flow. A greater understanding of these mechanisms enabled a more practical design of hybrid diffuser to be developed that not only simplified the geometry but also improved the quality of the bleed air making it more attractive for use in component cooling.
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Koutmos, P., and J. J. McGuirk. "Numerical Calculations of the Flow in Annular Combustor Dump Diffuser Geometries." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 203, no. 5 (September 1989): 319–31. http://dx.doi.org/10.1243/pime_proc_1989_203_121_02.
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A method for calculating the turbulent isothermal flow in axisymmetric annular dump diffuser geometries is described and appraised. The calculation method is based on the numerical solution of the time-averaged transport equations for momentum, continuity, turbulence kinetic energy and energy dissipation, using a finite difference formulation. A boundary-fitted curvilinear orthogonal grid obtained from a solution of the inverse Laplace equations is used to represent the curved combustor head accurately and reduce numerical diffusion errors due to better alignment of the flow streamlines with the grid lines. Comparison between predicted results and measurements indicates that variations in (a) the overall pressure recovery and (b) the loss coefficient performance of the dump diffuser system, with changes in diffuser design features (for example inner/outer annulus mass flow split or dump gap), can be predicted to within 7 per cent of the inlet dynamic head without adopting a more refined turbulence closure. The method is therefore demonstrated to be a useful design tool for dump diffuser geometries.
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Carrotte, J. F., P. A. Denman, A. P. Wray, and P. Fry. "Detailed Performance Comparison of a Dump and Short Faired Combustor Diffuser System." Journal of Engineering for Gas Turbines and Power 116, no. 3 (July 1, 1994): 517–26. http://dx.doi.org/10.1115/1.2906850.
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A rectangular model simulating four sectors of a combustion chamber was used to compare the performance of a standard dump diffuser, of overall length 180 mm, with that of a faired design 25.5 mm shorter. The performance of each system was assessed in terms of total pressure loss and static pressure recovery between prediffuser inlet and the annuli surrounding the flame tube. Since the program objective was to test design concepts only, no allowance was made for the presence of burner feed arms or flame tube support pins. In addition, tests were performed with relatively low levels of inlet turbulence and no wake mixing effects from upstream compressor blades. Relative to the dump design, the mass weighted total pressure loss to the outer and inner annuli was reduced by 30 and 40 percent, respectively, for the faired diffuser. Measurements around the flame tube head were used to identify regions of high loss within each system and account for the differences in performance. Within a dump diffuser the flow separates at prediffuser exit resulting in a free surface diffusion around the flame tube head and a recirculating flow in the dump cavity. This source of loss is eliminated in the faired system where the flow remains attached to the casings. Furthermore, the faired system exhibited similar velocity magnitudes and gradients around the combustor head despite its shorter length.
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Hendricks, R. C., D. T. Shouse, W. M. Roquemore, D. L. Burrus, B. S. Duncan, R. C. Ryder, A. Brankovic, N. S. Liu, J. R. Gallagher, and J. A. Hendricks. "Experimental and Computational Study of Trapped Vortex Combustor Sector Rig with High-Speed Diffuser Flow." International Journal of Rotating Machinery 7, no. 6 (2001): 375–85. http://dx.doi.org/10.1155/s1023621x0100032x.
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The Trapped Vortex Combustor (TVC) potentially offers numerous operational advantages over current production gas turbine engine combustors. These include lower weight, lower pollutant emissions, effective flame stabilization, high combustion efficiency, excellent high altitude relight capability, and operation in the lean burn or RQL modes of combustion. The present work describes the operational principles of the TVC, and extends diffuser velocities toward choked flow and provides system performance data. Performance data include EINOx results for various fuel-air ratios and combustor residence times, combustion efficiency as a function of combustor residence time, and combustor lean blow-out (LBO) performance. Computational fluid dynamics (CFD) simulations using liquid spray droplet evaporation and combustion modeling are performed and related to flow structures observed in photographs of the combustor. The CFD results are used to understand the aerodynamics and combustion features under different fueling conditions. Performance data acquired to date are favorable compared to conventional gas turbine combustors. Further testing over a wider range of fuel-air ratios, fuel flow splits, and pressure ratios is in progress to explore the TVC performance. In addition, alternate configurations for the upstream pressure feed, including bi-pass diffusion schemes, as well as variations on the fuel injection patterns, are currently in test and evaluation phases.
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Hubbard, S., and A. P. Dowling. "Acoustic Resonances of an Industrial Gas Turbine Combustion System." Journal of Engineering for Gas Turbines and Power 123, no. 4 (October 1, 2000): 766–73. http://dx.doi.org/10.1115/1.1370975.
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A theory is developed to describe low-frequency acoustic waves in the complicated diffuser/combustor geometry of a typical industrial gas turbine. This is applied to the RB211-DLE geometry to give predictions for the frequencies of the acoustic resonances at a range of operating conditions. The main resonant frequencies are to be found around 605 Hz (associated with the plenum) and around 461 Hz and 823 Hz (associated with the combustion chamber), as well as one at around 22 Hz (a bulk mode associated with the system as a whole). The stabilizing effects of a Helmholtz resonator, which models damping through nonlinear effects, are included, together with effects of coupled pressure waves in the fuel supply system.
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Hestermann, R., S. Kim, A. Ben Khaled, and S. Wittig. "Flow Field and Performance Characteristics of Combustor Diffusers: A Basic Study." Journal of Engineering for Gas Turbines and Power 117, no. 4 (October 1, 1995): 686–94. http://dx.doi.org/10.1115/1.2815454.
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Results of a detailed study concerning the influence of geometric as well as fluid mechanic parameters on the performance of a plane model combustor diffuser in cold flow are presented. For a qualitative insight into the complex flow field inside the prediffuser, the sudden expansion region, and the flow field around the flame tube dome, results of a flow visualization study with the hydrogen bubble method as well as with the ink jet method are presented for different opening angles of the prediffuser and for different flame tube distances. Also, quantitative data from detailed measurements with LDV and conventional pressure probes in a geometrically similar air-driven setup are presented. These data clearly demonstrate the effect of boundary layer thickness as well as the influence of different turbulence levels at the entry of the prediffuser on the performance characteristics of combustor diffusers. The possibility of getting an unseparated flow field inside the prediffuser even at large opening angles by appropriately matching the diffuser’s opening angle and the flame tube distance is demonstrated. Also, for flows with an increased turbulence level at the entrance—all other conditions held constant—an increased opening angle can be realized without experiencing flow separation. The comparison of the experimental data with predictions utilizing a finite-volume-code based on a body-fitted coordinate system for diffusers with an included total opening angle less than 18 deg demonstrates the capability of describing the flow field in combustor diffusers with reasonable accuracy.
Dissertations / Theses on the topic "Combustor-diffuser system"
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Dunn, Jason. "ON THE NATURE OF THE FLOW IN A SEPARATED ANNULAR DIFFUSER." Master's thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4101.
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The combustor-diffuser system remains one of the most studied sections of the turbomachine. Most of these investigations are due to the fact that quite a bit of flow diffusion is required in this section as the high speed flow exits the compressor and must be slowed down to enter the combustor. Like any diffusion process there is the chance for the development of an unfavorable adverse pressure gradient that can lead to flow separation; a cause of drastic losses within a turbine. There are two diffusion processes in the combustor-diffuser system: The flow first exits the compressor into a pre-diffuser, or compressor discharge diffuser. This diffuser is responsible for a majority of the pressure recovery. The flow then exits the pre-diffuser by a sudden expansion into the dump diffuser. The dump diffuser comprises the majority of the losses, but is necessary to reduce the fluid velocity within acceptable limits for combustion. The topic of active flow control is gaining interest in the industry because such a technique may be able to alleviate some of the requirements of the dump diffuser. If a wider angle pre-diffuser with separation control were used the fluid velocity would be slowed more within that region without significant losses. Experiments were performed on two annular diffusers to characterize the flow separation to create a foundation for future active flow control techniques. Both diffusers had the same fully developed inlet flow condition, however, the expansion of the two diffusers differed such that one diffuser replicated a typical compressor discharge diffuser found in a real machine while the other would create a naturally separated flow along the outer wall. Both diffusers were tested at two Reynolds numbers, 5x104 and 1x105, with and without a vertical wall downstream of the exit to replicate the dump diffuser that re-directs the flow from the pre-diffuser outlet to the combustor. Static pressure measurements were obtained along the OD and ID wall of the diffusers to determine the recovered pressure throughout the diffuser. In addition to these measurements, tufts were used to visualize the flow. A turbulent CFD model was also created to compare against experimental results. In the end, the results were validated against empirical data as well as the CFD model. It was shown that the location of the vertical wall was directly related to the amount of separation as well as the separation characteristics. These findings support previous work and help guide future work for active flow control in a separated annular diffuser both computationally and experimentally.M.S.A.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Aerospace Engineering MSAE
Conference papers on the topic "Combustor-diffuser system"
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SRINIVASAN, R., W. FREEMAN, S. MOZUMDAR, and J. GRAHMANN. "Measurements in an annular combustor-diffuser system." In 26th Joint Propulsion Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1990. http://dx.doi.org/10.2514/6.1990-2162.
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Carrotte, J. F., D. W. Bailey, and C. W. Frodsham. "Detailed Measurements on a Modern Combustor Dump Diffuser System." In ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/94-gt-299.
Full textAbstract:
An experimental investigation has been carried out to determine the flow characteristics and aerodynamic performance of a modern gas turbine combustor dump diffuser. The system comprised of a straight walled pre-diffuser, of area ratio 1.35, which projected into a dump cavity where the flow divided to pass either into the flame tube or surrounding feed annuli. In addition, a limited amount of air was removed to simulate flow used for turbine cooling. The flame tube was relatively deep, having a radial depth 5.5 times that of the passage height at pre-diffuser inlet, and incorporated burner feed arms, cowl head porosity, cooling rings and primary ports. Representative inlet conditions to the diffuser system were generated by a single stage axial flow compressor. Results are presented for the datum configuration, and for a further three geometries in which the distance between pre-diffuser exit and the head of the flame tube (ie. dump gap) was reduced. Relatively high values of stagnation pressure loss were indicated, with further significant increases occurring at smaller dump gaps. These high losses, which suggest a correlation with other published data, are due to the relatively deep flame tube and short diffuser length. Furthermore, the results also focus attention on how the presence of a small degree of diffuser inlet swirl, typical of that which may be found within a gas turbine engine, can result in large swirl angles being generated further downstream around the flame tube. This is particularly true for flow passing to the inner annulus.
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Barker, A. G., J. F. Carrotte, and C. W. Frodsham. "The Effect on Combustor Diffuser Performance of Structural OGV/Pre-Diffuser Systems." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-304.
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An experimental investigation has been carried out to assess the aerodynamic effects of locating radial struts within the pre-diffuser of a modern combustor dump diffuser system. Engine representative inlet conditions were generated by a single stage rotor, with the diffuser system incorporating various compressor outlet guide vane (OGV)/pre-diffuser assemblies and an annular flame tube with representative porosity. Stagnation and static pressure measurements were obtained at numerous locations and included assessment of the upstream pressure field, associated with the struts, which impacts on the rotor and OGV aerodynamics. Measurements were also obtained within the feed annuli, surrounding the flame tube, with attempts also being made to assess the stagnation pressure distributions presented to a simulated flame tube burner. Initial tests were performed with an OGV row attached to a conventional 1.45 area ratio pre-diffuser, this providing the datum to which all other systems were assessed. These included systems with thin or thick struts with the strut blockage, at pre-diffuser exit, being 5% and 11% of the gas passage area respectively. For the geometries tested it was shown that the method of adjusting each pre-diffuser passage area, to account for the strut blockage, was successful in providing similar levels of reduced kinetic energy at pre-diffuser exit. Despite this, however, the presence of strut wakes and their effect on the dump cavity flow produced increases in stagnation pressure loss. These loss variations were evaluated for both the feed annuli and burner flows, with the magnitudes depending on whether the struts were aligned or midway between burners. Also assessed was the impact of the increased circumferential flow non-uniformity that was observed for the flow within the inner feed annulus. A beneficial effect produced by the struts was the significant reductions in flow swirl, within the diffuser system, relative to the datum. This improved axial alignment of the flow, provided a more uniform pressure distribution to the burners and a more stable feed to the various flame tube features.
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Karki, K. C., V. L. Oechsle, and H. C. Mongia. "A Computational Procedure for Diffuser-Combustor Flow Interaction Analysis." In ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-035.
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This paper describes a diffuser-combustor flow interaction analysis procedure for gas turbine combustion systems. The method is based on the solution of the Navier-Stokes equations in a generalized non-orthogonal coordinate system. The turbulence effects are modeled via the standard two-equation (k-ε) model. The method has been applied to a practical gas turbine combustor-diffuser system that includes support struts and fuel nozzles. Results have been presented for a three-dimensional simulation, as well as for a simplified axisymmetric simulation. The flow exhibits significant three-dimensional behavior. The axisymmetric simulation is shown to predict the static pressure recovery and the total pressure losses reasonably well.
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Karuppannan, Srinivasan, Vaibhav Murlidhar Sondur, Gullapalli Sivaramakrishna, Raju D. Navindgi, and N. Muthuveerappan. "CFD Analyses of Combustor-Diffuser System of Marine Gas Turbine Engine." In ASME 2017 Gas Turbine India Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gtindia2017-4739.
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Reverse flow can annular combustor configuration becomes the inevitable option for industrial and marine gas turbine engine, due to its advantages over other configurations. The complexity associated with can annular configuration is optimum design of annular diffuser, as its flow field is dominated by downstream blockage created by transition duct geometry. In the present study, flow behavior in the annular diffuser has been analyzed by simulating realistic downstream combustor liner and transition duct geometry. Flow analysis has been carried out using ANSYS Fluent and turbulence has been modeled using Realizable k-ε model. The diffuser is designed based on G* method, for optimum pressure recovery. Six diffuser configurations have been analyzed by varying the inner wall profile. The effect of parameters on flow field within diffuser and dump region has been studied. Also, the static pressure recovery and total pressure loss coefficient of diffuser is calculated and compared. The results show that the profile of the inner wall and the dump region needs to be tailored to get optimum performance from diffuser.
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Agrawal, Ajay K., Jayanta S. Kapat, and Tah-teh Yang. "Flow Interactions in the Combustor-Diffuser System of Industrial Gas Turbines." In ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-454.
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This paper presents an experimental/computational study of cold flow in the combustor-diffuser system of industrial gas turbines to address issues relating to flow interactions and pressure losses in the pre- and dump diffuses. The present configuration with can annular combustors differs substantially from the aircraft engines which typically use a 360 degree annular combustor. Experiments were conducted in a one-third scale, annular 360-degree model using several can combustors equispaced around the turbine axis. A 3-D computational fluid dynamics analysis employing the multidomain procedure was performed to supplement the flow measurements. The measured data correlated well with the computations. The airflow in the dump diffuser adversely affected the prediffuser flow by causing it to accelerate in the outer region at the prediffuser exit. This phenomenon referred to as the sink-effect also caused a large fraction of the flow to bypass much of the dump diffuser and go directly from the prediffuser exit to the bypass air holes on the combustor casing, thereby, rendering the dump diffuser ineffective in diffusing the flow. The dump diffuser was occupied by a large recirculation region which dissipated the flow kinetic energy. Approximately 1.2 dynamic head at the prediffuser inlet was lost in the combustor-diffuser system; much of it in the dump diffuser where the fluid passed through the narrow gaps and pathways. Strong flow interactions in the combustor-diffuser system indicate the need for design modifications which could not be addressed by empirical correlations based on simple flow configurations.
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Schweiger, Tom, Richard M. Underhill, and Duncan W. Livingston. "Rolls Royce RB211-DLE Combustor Diffuser Design Optimisation." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-237.
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This paper presents a technique for optimising the performance of a diffuser in an industrial gas turbine using validated CFD modelling. The combustor module of the Rolls Royce RB211-DLE industrial engine was modelled from diffuser inlet to combustor inlet, using a hybrid meshing procedure. A CFD model of the current RB211-DLE diffuser and casing was validated against perspex single sector rig data, including pressure probe measurements, oil dot flow tests and a sensitivity analysis. A three-dimensional design process was then undertaken to determine how the shape of the diffuser affects the loss through the system, and hence which type of diffuser would provide the best opportunity for maximising the engine performance. The best two general diffuser designs were optimised using an iterative two-dimensional design process. The performance of these optimised designs was then confirmed by full three-dimensional modelling. This work suggests that a significant improvement in sfc (based on a constant turbine temperature) would be achieved if the optimum diffuser design is installed into the RB211-DLE engine.
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SRINIVASAN, R., W. FREEMAN, J. GRAHMANN, and E. COLEMAN. "Parametric evaluation of the aerodynamic performance of an annular combustor-diffuser system." In 26th Joint Propulsion Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1990. http://dx.doi.org/10.2514/6.1990-2163.
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Carrotte, J. F., P. A. Denman, A. P. Wray, and P. Fry. "Detailed Performance Comparison of a Dump and Short Faired Combustor Diffuser System." In ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/93-gt-331.
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A rectangular model simulating 4 sectors of a combustion chamber was used to compare the performance of a standard dump diffuser, of overall length 180mm, with that of a faired design 25.5mm shorter. The performance of each system was assessed in terms of total pressure loss and static pressure recovery between pre-diffuser inlet and the annuli surrounding the flame tube. Since the program objective was to test design concepts only, no allowance was made for the presence of burner feed arms or flame tube support pins. In addition, tests were performed with relatively low levels of inlet turbulence and no wake mixing effects from upstream compressor blades. Relative to the dump design, the mass weighted total pressure loss to the outer and inner annuli was reduced by 30% and 40% respectively for the faired diffuser. Measurements around the flame tube head were used to identify regions of high loss within each system and account for the differences in performance. Within a dump diffuser the flow separates at pre-diffuser exit resulting in a free surface diffusion around the flame tube head and a recirculating flow in the dump cavity. This source of loss is eliminated in the faired system where the flow remains attached to the inner casing. Furthermore, the faired system exhibited similar velocity magnitudes and gradients around the combustor head despite its shorter length.
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Shen, Shanping, Pei He, Mingtao Shang, and Ronghai Mao. "The Effects of Cowling Geometry, Area Ratio and Dump Gap on a Combustor Diffusion System." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-26652.
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This paper presents numerical simulation of a combustor diffusion system, mainly focusing on the effects of the cowling geometry, the area ratio of the pre-diffuser and the axial length of the dump gap. The diffusion system of a full-scale single annular combustor is analyzed, using commercial software Fluent. Six different geometries are designed and numerically analyzed. Case 1 is a baseline, for which low emission technology burning in a lean mode is adopted. Cases 2, 3, and 4 are simulated to study the influence of the cowling geometry, especially the area of cowl capture plane. The study of cowling geometry shows that the best layout is case 4, owing to its least spillage of the air from the dome region into the inner and outer annuli of combustor. The normalized total pressure loss over the combustor is 3.49%. The total pressure distribution at the inlet of the main stage is more uniform than the baseline case 1. Cases 4 and 5 are also analyzed to investigate the influences of area ratio of the pre-diffuser, which varies from 1.4 in case 4 to 1.5 in case 5. The normalized combustor total pressure loss decreased to 3.30%, whose total pressure loss of pre-diffuser decreased while the static pressure recovery coefficient of the pre-diffuser increased from 0.43 to 0.52. Cases 4 and 6 are examined for the axial length of the diffuser dump gap, which is increased by 20% from case 4 to case 6. The combustor total pressure loss increases slightly, with little impact on the pressure loss of the pre-diffuser and dump gap region.