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1
Winkler, Dieter, Weiqun Geng, Geoffrey Engelbrecht, Peter Stuber, Klaus Knapp, and Timothy Griffin. "Staged combustion concept for gas turbines." Journal of the Global Power and Propulsion Society 1 (September 27, 2017): CVLCX0. http://dx.doi.org/10.22261/cvlcx0.
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AbstractGas turbine power plants with high load flexibility are particularly suitable to compensate power fluctuations of wind and solar plants. Conventional gas turbines suffer from higher emissions at low load operation. With the objective of improving this situation a staged combustion system has been investigated. At low gas turbine load an upstream stage (first stage) provides stable combustion at low emissions while at higher loads the downstream stage (second stage) is started to supplement the power. Three injection geometries have been studied by means of computational fluid dynamics (CFD) simulations and atmospheric tests. The investigated geometries were a simple annular gap, a jet-in-cross-flow configuration and a lobe mixer. With CFD simulations the quality of mixing of second stage fresh gas with first stage exhaust gas was assessed. The lobe mixer showed the best mixing quality and hence was expected to also be the best variant in terms of combustion. However atmospheric combustion tests showed lower emissions for the jet-in-cross-flow configuration. Comparing flame photos in the visible and ultraviolet (UV) range suggest that the flame might be lifted off for the lobe mixer, leading to insufficient time for carbon monoxide (CO) burnout. CFD analysis of turbulent flame speed, turbulence and strain rates support the hypotheses of lifted off flame. Overall the staged concept was found to show very promising results not only with natural gas but also with natural gas enriched with propane or hydrogen. The investigations showed that apart from having an efficient and compact mixing of the two stages it is also very important to design the flow field such that the second flame can be anchored properly in order to achieve compact flames with sufficient time for CO burnout.
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Rusanov, Andrii V., Viktor L. Shvetsov, Anna I. Kosianova, et al. "The Gas-Dynamic Efficiency Increase of the K-300 Series Steam Turbine Control Compartment." Journal of Mechanical Engineering 23, no. 4 (2020): 6–13. http://dx.doi.org/10.15407/pmach2020.04.006.
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The paper proposes ways to increase the efficiency of nozzle control for steam power turbines of the K-300 series, that, along with the K-200 series turbines, form the basis of thermal energy in Ukraine. The object of study is considered to be the control compartment (CC) of the high-pressure cylinder (HPC) of the K-325-23.5 steam turbine. In the paper, the calculation and design of the control compartment of the steam turbine was performed using the complex methodology developed in IPMach NAS of Ukraine, that includes methods of different levels of complexity, from one-dimensional to models for calculation of spatial viscous flows, as well as analytical methods for spatial geometries of flow parts description based on limited number of parameterized values. The complex design methodology is implemented in the IPMFlow software package, which is a development of the FlowER and FlowER–U software packages. A model of a viscous turbulent flow is based on the numerical integration of an averaged system of Navier-Stokes equations, for the closure of which the two-term Tamman equation of state is used. Turbulent phenomena were taken into account using a SST Menter two-parameter differential turbulence model. The research was conducted for six operation modes in the calculation area, which consisted of more than 3 million cells (elementary volumes), taking into account the interdiscand diaphragm leakage. According to the results of numerical studies of the original control compartment of the K-325-23.5 steam turbine, it is shown that the efficiency in the flow part is quite low in all operation modes, including the nominal one (100% power mode), due to large losses of kinetic energy in the equalization chamber, as well as inflated load on the first stage. On the basis of the performed analysis of gas-dynamic processes, the directions of a control compartment flow part modernization are formed and themodernization itself is executed. In the new flow part, compared to the original one, there is a favorable picture of the flow in all operation modes, which ensures its high gas-dynamic efficiency. Depending on the mode, the efficiency of the control compartment increased by 4.9–7.3%, and the capacity increased by 1–2 MW. In the nominal mode (100% mode) the efficiency of the new control compartment, taking into account the interdisc and overbandage leakage, is 91%.
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Jones, W. P., M. N. Sodha, and J. J. McGuirk. "Calculation of the Flow in a Sector of an Annular Combustor." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power Engineering 203, no. 3 (1989): 187–93. http://dx.doi.org/10.1243/pime_proc_1989_203_026_02.
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Calculations have been made of the isothermal flow field within a sector of an annular combustion chamber representative of the type to be found in small gas turbines. The complex combustor geometry is described using a Cartesian finite difference mesh within which the physical domain boundaries are represented in a piecewise linear fashion. The k-s turbulence model is used to describe turbulent transport. Overall the calculated and measured flow fields are found to be in reasonable agreement and in the primary zone measured velocity profiles are reproduced to within an acceptable accuracy.
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Kvasha, Yu A. "Calculation of a 3D turbulent flow in aircraft gas turbine engine ducts." Technical mechanics 2020, no. 4 (2020): 65–71. http://dx.doi.org/10.15407/itm2020.04.065.
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This work is devoted to the development of approaches to the numerical simulation of 3D turbulent gas flows in different ducts of aircraft gas turbine engines, in particular in inlet device ducts. Inlet devices must provide large values of the total pressure recovery factor and flow uniformity at the engine compressor inlet. The aim of this work is the verification of the operability of a technique developed earlier for the calculation of the parameters of a 3D turbulent flow in complex-shape ducts. The basic approach is a numerical simulation of 3D turbulent gas flows on the basis of the complete averaged Navier¬–Stokes equations and a two-parameter turbulence model. The proposed technique of numerical simulation of a 3D gas flow was tested by calculating a 3D laminar flow in a square pipe bent at a right angle. The calculated flow pattern is in satisfactory agreement with the experimental data on the flow structure in a pipe elbow reported in the literature. Based on a numerical simulation of a 3D turbulent flow in the air duct of one of the air intake configurations for an aircraft turboprop engine, the efficiency of that configuration is assessed. The calculated flow parameter nonuniformity at the air intake outlet, i. e., at the compressor inlet, is compared with that obtained earlier for another air intake configuration for the same engine. It is pointed out that the air intake configuration considered earlier provides a much more uniform flow parameter distribution at the engine compressor inlet. On the whole, this work shows that the quality of subsonic air intakes for aircraft gas turbine engines can be assessed using the proposed numerical technique of 3D gas flow simulation. The results obtained may be used in the aerodynamic improvement of inlet devices for aircraft engines of different types.
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Radomsky, R. W., and K. A. Thole. "Measurements and Predictions of a Highly Turbulent Flowfield in a Turbine Vane Passage." Journal of Fluids Engineering 122, no. 4 (2000): 666–76. http://dx.doi.org/10.1115/1.1313244.
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As highly turbulent flow passes through downstream airfoil passages in a gas turbine engine, it is subjected to a complex geometry designed to accelerate and turn the flow. This acceleration and streamline curvature subject the turbulent flow to high mean flow strains. This paper presents both experimental measurements and computational predictions for highly turbulent flow as it progresses through a passage of a gas turbine stator vane. Three-component velocity fields at the vane midspan were measured for inlet turbulence levels of 0.6%, 10%, and 19.5%. The turbulent kinetic energy increased through the passage by 130% for the 10% inlet turbulence and, because the dissipation rate was higher for the 19.5% inlet turbulence, the turbulent kinetic energy increased by only 31%. With a mean flow acceleration of five through the passage, the exiting local turbulence levels were 3% and 6% for the respective 10% and 19.5% inlet turbulence levels. Computational RANS predictions were compared with the measurements using four different turbulence models including the k-ε, Renormalization Group (RNG) k-ε, realizable k-ε, and Reynolds stress model. The results indicate that the predictions using the Reynolds stress model most closely agreed with the measurements as compared with the other turbulence models with better agreement for the 10% case than the 19.5% case. [S0098-2202(00)00804-X]
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Gerendas, M., and S. Wittig. "Experimental and Numerical Investigation on the Evaporation of Shear-Driven Multicomponent Liquid Wall Films." Journal of Engineering for Gas Turbines and Power 123, no. 3 (2001): 580–88. http://dx.doi.org/10.1115/1.1362663.
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The presented work is concerned with two-phase flows similar to those in prefilming airblast atomizers and combustors employing film vaporization. Correlations for the multicomponent mixture properties and models for the calculations of the multicomponent evaporation were implemented in a well tested elliptic finite-volume code GAP-2D (S. Wittig et al., 1992, “Motion and Evaporation of Shear-Driven Liquid Films in Turbulent Gas,” ASME J. Eng. Gas Turbines Power 114, pp. 395–400) utilizing time-averaged quantities, k,ε turbulence model, wall functions, and curve-linear coordinates in the gas phase, adiabatic or diabatic conditions at the film plate, partially turbulent velocity profile, uniform temperature, and a rapid mixing approach in the wavy film. This new code GAP-2K was tested for stability, precision, and grid independence of the results by applying it to a turbulent hot air flow over a two-component liquid film, a mixture of water and ethanol in different concentrations. Both simulations and experiments were carried out over a wide range of inlet conditions, such as inlet pressure (1–2.6 bar), inlet temperature (298–573 K), inlet air velocity (30–120 m/s), initial liquid flow rate (0.3–1.2 cm2/s), and initial ethanol concentration (20–75 percent mass). Profiles of temperature, gas velocity, and concentration of the evaporating component normal to the film, and the development of the film temperature, the static pressure, the liquid flow rate, and the liquid compound along the film plate have been measured and compared with the simulation, showing a good match.
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Lock, Gary D., Michael Wilson, and J. Michael Owen. "Influence of Fluid Dynamics on Heat Transfer in a Preswirl Rotating-Disk System." Journal of Engineering for Gas Turbines and Power 127, no. 4 (2004): 791–97. http://dx.doi.org/10.1115/1.1924721.
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Modern gas turbines are cooled using air diverted from the compressor. In a “direct-transfer” preswirl system, this cooling air flows axially across the wheel space from stationary preswirl nozzles to receiver holes located in the rotating turbine disk. The distribution of the local Nusselt number Nu on the rotating disk is governed by three nondimensional fluid-dynamic parameters: preswirl ratio βp, rotational Reynolds number Reϕ, and turbulent flow parameter λT. This paper describes heat transfer measurements obtained from a scaled model of a gas turbine rotor-stator cavity, where the flow structure is representative of that found in the engine. The experiments reveal that Nu on the rotating disk is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations have been measured. At the higher coolant flow rates studied, there is a peak in heat transfer at the radius of the preswirl nozzles associated with the impinging jets from the preswirl nozzles. At lower coolant flow rates, the heat transfer is dominated by viscous effects. The Nusselt number is observed to increase as either Reϕ or λT increases.
8
Golomb, Richard, Vivek Sahai, and Dah Yu Cheng. "A New Tailpipe Design for GE Frame-Type Gas Turbines to Substantially Lower Pressure Losses." Journal of Turbomachinery 125, no. 1 (2003): 128–32. http://dx.doi.org/10.1115/1.1515335.
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Many GE frame gas turbines have a unique 90-deg tailpipe exhaust system that contains struts, diffusers, and turning vanes. As confirmed in a recent report by GE and other authors, it is known in the industry that this tailpipe design has large pressure losses. In this recent report a pressure loss as high as 60 in. of water (0.15 kgs/sqcm) was cited. Due to the flow separations they create, the report indicates that the struts can cause very high-pressure losses in the turbine. The report also states that these pressure losses can vary with different turbine load conditions. Cheng Fluid Systems and Cheng Power Systems have conducted a study aimed at substantially reducing these pressure losses. Flow control technology introduced to the refinery industry, i.e., the Cheng Rotation Vane (CRV) and the Large Angle Diffuser (LAD) can be used to mitigate the flow separation and turbulence that occurs in turns, bends, and large sudden expansions. Specifically the CRV addresses the flow separations in pipe turns, and the LAD addresses the flow problems that occur with large sudden expansion areas. The paper will introduce the past experience of the CRV and LAD, and will then use computer simulations to show the flow characteristics around a new design. First, the study meticulously goes through the entire GE exhaust system, starting with the redesign of the airfoil shape surrounding the struts. This new design has a larger angle of attack and minimizes the flow separations over a much wider operating range. Second, the pros and cons of the concentric turning vanes are studied and it is shown that they are more flow restrictive, rather than flow enhancing. Third, it is shown that the highly turbulent rectangular box-type exhaust ducting design, substantially contributes to high noise levels and pressure losses. In this paper a completed design will be shown that incorporates a new airfoil shape for the struts, and by using CRV flow technology in combination with the LAD flow technology, the pressure recovery can be enhanced. If the pressure losses could be reduced by 40 inches of water (0.10 kgs/sqcm), the turbine efficiency could be increased by 5%, and the power output could be increased by 6%.
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Bohn, D., and J. Gier. "The Effect of Turbulence on the Heat Transfer in Closed Gas-Filled Rotating Annuli." Journal of Turbomachinery 120, no. 4 (1998): 824–30. http://dx.doi.org/10.1115/1.2841795.
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Higher turbine inlet temperatures are a common measure for increasing the thermal efficiency of modern gas turbines. This development leads not only to the need for more efficient turbine blade cooling but also to the requirement for a more profound knowledge of the mechanically and thermally stressed parts of the rotor. For determining thermal stresses from the temperature distribution in the rotor of a gas turbine, one has to encounter the convective transfer in rotor cavities. In the special case of an entirely closed gas-filled rotating annulus, the convective flow is governed by a strong natural convection. Owen and other researchers have found that the presence of turbulence and its inclusion in the modeling of the flow causes significant differences in the flow development in rotating annuli with throughflow, e.g., different vortex structures. However, in closed rotating annuli there is still a lack of knowledge concerning the influence of turbulence. Based on previous work, in this paper the influence of turbulence on the flow structure and on the heat transfer is investigated. The flow is investigated numerically with a three-dimensional Navier–Stokes solver, based on a pressure correction scheme. To account for the turbulence, a low-Reynolds-number k–ε model is employed. The results are compared with experiments performed at the Institute of Steam and Gas Turbines. The computations demonstrate that turbulence has a considerable influence on the overall heat transfer as well as on the local heat transfer distribution. Three-dimensional effects are discussed by comparing the three-dimensional calculation with a two-dimensional calculation of the same configuration and are found to have some impact.
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MERAD, Asmae BOUANANI, and Mama BOUCHAOUR. "MODELING AND SIMULATION OF THE VERTICAL AXIS WIND TURBINE BY QBLADE SOFTWARE." Algerian Journal of Renewable Energy and Sustainable Development 2, no. 02 (2020): 181–88. http://dx.doi.org/10.46657/ajresd.2020.2.2.11.
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The use of wind energy has no harmful effects on the environment. This makes it a clean energy that is a real alternative to the problem of nuclear waste management and greenhouse gas emissions. Vertical axis wind turbines have prospective advantages in the field of domestic applications, because they have proven effectual in urban areas where wind flow conditions are intermittent, omnidirectional, unsteady and turbulent. The wind cannot ensure a regular energy supply without optimising the aerodynamics of the blades. This article presents a reminder about wind energy and wind turbines, especially the VAWT type wind turbines and also gives a presentation on the aerodynamic side of VAWT by studying the geometry and aerodynamic characteristics of the blade profiles with the acting forces and also the explanation of the DMS multiple flow tube model. This work also gives the different simulation methods to optimize the behaviour of the blades from the selected NACA profiles; the analysis first goes through the design of the blades by the design and simulation software Qblade which is used to calculate also the forces on the blade and the coefficients of lift, drag and fineness. At the end of this article we have the DMS simulation of the VAWT turbines, by determining the power coefficient and the power collected by the turbine to select the wind turbine adapted to a well characterized site.
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Volino, R. J., and T. W. Simon. "Boundary Layer Transition Under High Free-Stream Turbulence and Strong Acceleration Conditions: Part 2—Turbulent Transport Results." Journal of Heat Transfer 119, no. 3 (1997): 427–32. http://dx.doi.org/10.1115/1.2824115.
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Measurements from heated boundary layers along a concave-curved test wall subject to high (initially 8 percent) free-stream turbulence intensity and strong (K = (ν/U∞2 dU∞/dx, as high as 9 × 10−6) acceleration are presented and discussed. Conditions for the experiments were chosen to simulate those present on the downstream half of the pressure side of a gas turbine airfoil. Turbulence statistics, including the turbulent shear stress, the turbulent heat flux, and the turbulent Prandtl number are presented. The transition zone is of extended length in spite of the high free-stream turbulence level. Turbulence quantities are strongly suppressed below values in unaccelerated turbulent boundary layers. Turbulent transport quantities rise with the intermittency, as the boundary layer proceeds through transition. Octant analysis shows a similar eddy structure in the present flow as was observed in transitional flows under low free-stream turbulence conditions. To the authors’ knowledge, this is the first detailed documentation of a high-free-stream-turbulence boundary layer flow in such a strong acceleration field.
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Tafti, Danesh K., Long He, and K. Nagendra. "Large eddy simulation for predicting turbulent heat transfer in gas turbines." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2022 (2014): 20130322. http://dx.doi.org/10.1098/rsta.2013.0322.
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Blade cooling technology will play a critical role in the next generation of propulsion and power generation gas turbines. Accurate prediction of blade metal temperature can avoid the use of excessive compressed bypass air and allow higher turbine inlet temperature, increasing fuel efficiency and decreasing emissions. Large eddy simulation (LES) has been established to predict heat transfer coefficients with good accuracy under various non-canonical flows, but is still limited to relatively simple geometries and low Reynolds numbers. It is envisioned that the projected increase in computational power combined with a drop in price-to-performance ratio will make system-level simulations using LES in complex blade geometries at engine conditions accessible to the design process in the coming one to two decades. In making this possible, two key challenges are addressed in this paper: working with complex intricate blade geometries and simulating high-Reynolds-number ( Re ) flows. It is proposed to use the immersed boundary method (IBM) combined with LES wall functions. A ribbed duct at Re =20 000 is simulated using the IBM, and a two-pass ribbed duct is simulated at Re =100 000 with and without rotation (rotation number Ro =0.2) using LES with wall functions. The results validate that the IBM is a viable alternative to body-conforming grids and that LES with wall functions reproduces experimental results at a much lower computational cost.
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El-Batsh, Hesham M., and Magdy Bassily Hanna. "An Investigation on the Effect of Endwall Movement on the Tip Clearance Loss Using Annular Turbine Cascade." International Journal of Rotating Machinery 2011 (2011): 1–11. http://dx.doi.org/10.1155/2011/489150.
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The aerodynamic losses in gas turbines are mainly caused by profile loss secondary flow, and tip leakage loss. This study focuses on tip leakage flow of high-pressure turbine stages. An annular turbine cascade was constructed with fixed blades on the casing, and the distance between blade tip and the hub was considered as tip clearance gap. The effect of endwall movement on loss mechanism was investigated by using experimental and numerical techniques. The measurements were obtained while the hub was fixed but the numerical calculations were carried out for both stationary and moving cascades. Upstream and downstream flows were measured by using a calibrated five-hole pressure probe. The steady incompressible turbulent flow was obtained by solving Reynolds averaged Navier-Stokes equations and by employing shear stress transport (SST)k-ωturbulence model. The total pressure loss coefficient obtained from the numerical technique was compared with the experimental measurements, and the comparison showed good agreement. Tip clearance vortices were observed in the tip clearance gap. It was found through this study that end-wall movement reduces tip leakage loss through the cascade.
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Motheau, Emmanuel, Franck Nicoud, and Thierry Poinsot. "Mixed acoustic–entropy combustion instabilities in gas turbines." Journal of Fluid Mechanics 749 (May 16, 2014): 542–76. http://dx.doi.org/10.1017/jfm.2014.245.
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AbstractA combustion instability in a combustor terminated by a nozzle is analysed and modelled based on a low-order Helmholtz solver. A large eddy simulation (LES) of the corresponding turbulent, compressible and reacting flow is first performed and analysed based on dynamic mode decomposition (DMD). The mode with the highest amplitude shares the same frequency of oscillation as the experiment (approximately 320 Hz) and shows the presence of large entropy spots generated within the combustion chamber and convected down to the exit nozzle. The lowest purely acoustic mode being in the range 700–750 Hz, it is postulated that the instability observed around 320 Hz stems from a mixed entropy–acoustic mode, where the acoustic generation associated with entropy spots being convected throughout the choked nozzle plays a key role. The DMD analysis allows one to extract from the LES results a low-order model that confirms that the mechanism of the low-frequency combustion instability indeed involves both acoustic and convected entropy waves. The delayed entropy coupled boundary condition (DECBC) (Motheau, Selle & Nicoud, J. Sound Vib., vol. 333, 2014, pp. 246–262) is implemented into a numerical Helmholtz solver where the baseline flow is assumed at rest. When fed with appropriate transfer functions to model the entropy generation and convection from the flame to the exit, the Helmholtz/DECBC solver predicts the presence of an unstable mode around 320 Hz, in agreement with both LES and experiments.
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Han, Je-Chin. "Recent Studies in Turbine Blade Cooling." International Journal of Rotating Machinery 10, no. 6 (2004): 443–57. http://dx.doi.org/10.1155/s1023621x04000442.
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Gas turbines are used extensively for aircraft propulsion, land-based power generation, and industrial applications. Developments in turbine cooling technology play a critical role in increasing the thermal efficiency and power output of advanced gas turbines. Gas turbine blades are cooled internally by passing the coolant through several rib-enhanced serpentine passages to remove heat conducted from the outside surface. External cooling of turbine blades by film cooling is achieved by injecting relatively cooler air from the internal coolant passages out of the blade surface in order to form a protective layer between the blade surface and hot gas-path flow. For internal cooling, this presentation focuses on the effect of rotation on rotor blade coolant passage heat transfer with rib turbulators and impinging jets. The computational flow and heat transfer results are also presented and compared to experimental data using the RANS method with various turbulence models such as k-ε, and second-moment closure models. This presentation includes unsteady high free-stream turbulence effects on film cooling performance with a discussion of detailed heat transfer coef- ficient and film-cooling effectiveness distributions for standard and shaped film-hole geometry using the newly developed transient liquid crystal image method.
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Lewis, K. L. "Spanwise Transport in Axial-Flow Turbines: Part 1—The Multistage Environment." Journal of Turbomachinery 116, no. 2 (1994): 179–86. http://dx.doi.org/10.1115/1.2928351.
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Selected experimental results, obtained from a detailed investigation into the flow fields within two low-speed multistage turbines, are presented. A repeating stage condition occurred typically after two stages, with the secondary flows an important factor in the low aspect ratio geometry. A tracer gas technique was employed to identify the dominant mechanisms of spanwise transport and their relative significance. In the first stages of both machines, tracer transport was more intense near the endwalls than at midspan, while in the multistage environment the transport was approximately constant across the whole span. The convective influence of classical secondary flow, shroud leakage, and wake passage through a downstream blade was identified and shown to be as significant as turbulent diffusion in effecting cross-passage and spanwise transport. The data show that spanwise transport should be included within any throughflow model and are used to calibrate two scaling models. These models are presented in Part 2, where the influence of incorporating spanwise transport into a throughflow model is investigated.
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Barringer, M. D., O. T. Richard, J. P. Walter, S. M. Stitzel, and K. A. Thole. "Flow Field Simulations of a Gas Turbine Combustor." Journal of Turbomachinery 124, no. 3 (2002): 508–16. http://dx.doi.org/10.1115/1.1475742.
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The flow field exiting the combustor in a gas turbine engine is quite complex considering the presence of large dilution jets and complicated cooling schemes for the combustor liner. For the most part, however, there has been a disconnect between the combustor and turbine when simulating the flow field that enters the nozzle guide vanes. To determine the effects of a representative combustor flow field on the nozzle guide vane, a large-scale wind tunnel section has been developed to simulate the flow conditions of a prototypical combustor. This paper presents experimental results of a combustor simulation with no downstream turbine section as a baseline for comparison to the case with a turbine vane. Results indicate that the dilution jets generate turbulence levels of 15–18% at the exit of the combustor with a length scale that closely matches that of the dilution hole diameter. The total pressure exiting the combustor in the near-wall region neither resembles a turbulent boundary layer nor is it completely uniform putting both of these commonly made assumptions into question.
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Williams, M., W. C. Chen, G. Bache´, and A. Eastland. "An Analysis Methodology for Internal Swirling Flow Systems With a Rotating Wall." Journal of Turbomachinery 113, no. 1 (1991): 83–90. http://dx.doi.org/10.1115/1.2927741.
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This paper presents an analysis methodology for the calculation of the flow through internal flow components with a rotating wall such as annular seals, impeller cavities, and enclosed rotating disks. These flow systems are standard components in gas turbines and cryogenic engines and are characterized by subsonic viscous flow and elliptic pressure effects. The Reynolds-averaged Navier-Stokes equations for turbulent flow are used to model swirling axisymmetric flow. Bulk-flow or velocity profile assumptions aren’t required. Turbulence transport is assumed to be governed by the standard two-equation high Reynolds number turbulence model. A low Reynolds number turbulence model is also used for comparison purposes. The high Reynolds number turbulence model is found to be more practical. A novel treatment of the radial/swirl equation source terms is developed and used to provide enhanced convergence. Homogeneous wall roughness effects are accounted for. To verify the analysis methodology, the flow through Yamada seals, an enclosed rotating disk, and a rotating disk in a housing with throughflow are calculated. The calculation results are compared to experimental data. The calculated results show good agreement with the experimental results.
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Siswantara, Ahmad Indra, Budiarso та Steven Darmawan. "Investigation of Inverse-Turbulent-Prandtl Number with Four RNG k-ε Turbulence Models on Compressor Discharge Pipe of Bioenergy Micro Gas Turbine". Applied Mechanics and Materials 819 (січень 2016): 392–400. http://dx.doi.org/10.4028/www.scientific.net/amm.819.392.
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Inverse-Turbulent Prandtl number (α) is an important parameter in RNG k-ε turbulence models since it affects the ratio of molecular viscosity and turbulent viscosity. In curved pipe, this highly affects the model prediction to a large range eddy-scale flow. According to Yakhot & Orzag, the α range from 1-1.3929 has not been investigated in detail in curved pipe flow (Yakhot & Orszag, 1986) and specific Re. This paper varied inverse-turbulent Prandtl number α to 1-1.3 in RNG k-ε turbulence model on cylindrical curved pipe in order to obtain the optimum value of α to predict unfully-developed flow in the curve with curve ratio R/D of 1.607. Analysis was conducted numericaly with inlet specified Re of 40900 which was generated from the experiment at α 1, 1.1, 1.2, 1.3. Wall surface roughness is not considered in this paper. With assumption that thermal diffusivity is always dominant to turbulent viscosity, higher Inverse-turbulent Prandtl number represent domination of turbulent viscosity to molecular viscosity of the flow and predict to have more interaction between large scale eddy to small scale eddy as well. The results show the use of α = 1.3 has increased the turbulent kinetic energy by 7% and the turbulent dissipation by 5% compared to general inverse-turbulent Prandtl number of 1. The value difference shows that the use of higher α on RNG turbulence model described more interaction between eddies in secondary and swirling flow at pipe curve at Re = 40900.
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Wang, Jin, Milan Vujanovic, and Bengt Sunden. "A review of multiphase flow and deposition effects in film-cooled gas turbines." Thermal Science 22, no. 5 (2018): 1905–21. http://dx.doi.org/10.2298/tsci180108258w.
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This paper presents a review of particle deposition research in film-cooled gas turbines based on the recent open literature. Factors affecting deposition capture efficiency and film cooling effectiveness are analyzed. Experimental studies are summarized into two discussions in actual and virtual deposition environments. For investigation in virtual deposition environments, available and reasonable results are obtained by comparison of the Stokes numbers. Recent advances in particle deposition modeling for computational fluid dynamics are also reviewed. Various turbulence models for numerical simulations are investigated, and solutions for treatment of the particle sticking probability are described. In addition, analysis of injecting mist into the coolant flow is conducted to investigate gas-liquid two-phase flow in gas turbines. The conclusion remains that considerable re-search is yet necessary to fully understand the roles of both deposition and multi-phase flow in gas turbines.
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Lenzi, Tommaso, Alessio Picchi, Tommaso Bacci, Antonio Andreini, and Bruno Facchini. "Unsteady Flow Field Characterization of Effusion Cooling Systems with Swirling Main Flow: Comparison Between Cylindrical and Shaped Holes." Energies 13, no. 19 (2020): 4993. http://dx.doi.org/10.3390/en13194993.
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The presence of injectors with strongly swirled flows, used to promote flame stability in the combustion chambers of gas turbines, influences the behaviour of the effusion cooling jets and consequently of the liner’s cooling capabilities. For this reason, unsteady behaviour of the jets in the presence of swirling flow requires a characterization by means of experimental flow field analyses. The experimental setup of this work consists of a non-reactive single-sector linear combustor test rig, scaled up with respect to the real engine geometry to increase spatial resolution and to reduce the frequencies of the unsteadiness. It is equipped with a radial swirler and multi-perforated effusion plates to simulate the liner cooling system. Two effusion plates were tested and compared: with cylindrical and with laid-back fan-shaped 7-7-7 holes in staggered arrangement. Time resolved Particle Image Velocimetry has been carried out: the unsteady characteristics of the jets, promoted by the intermittent interactions with the turbulent mainstream, have been investigated as their vortex structures and turbulent decay. The results demonstrate how an unsteady analysis is necessary to provide a complete characterization of the coolant behaviour and of its turbulent mixing with mainflow, which affect, in turn, the film cooling capability and liner’s lifetime.
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Caetano, G. K., J. F. T. de Carvalho, and J. S. Rosa. "COLD FLOW NUMERICAL ANALYSIS OF GAS MICROTURBINE COMBUSTION CHAMBER THROUGH CFD TOOL." Revista de Engenharia Térmica 18, no. 1 (2019): 29. http://dx.doi.org/10.5380/reterm.v18i1.67044.
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Gas turbines are equipment used mainly in the generation of electric energy. They have as one of their main components the combustion chamber. Therefore, it is relevant to study the characteristics of this component, in order to reach a satisfactory operation. In this context, this paper presents an analysis of a combustion chamber applied to a gas turbine with a cold flow approach using the numerical theoretical method, through the computational fluid dynamics technique. In this experiment, the software Abaqus CFD (computational fluid dynamics) – present in the 3DExperience platform – and the finite volume method are used. The objective was to evaluate the flow, pressure and velocity profiles during the single-phase flow. The gas turbine prototype is configured using a combustion chamber of reverse flow type in order to decrease flow velocity and increase the combustion efficiency. Based on input data obtained from practical experiments, the calculation of the number and Reynolds confirmed – according to the literature of fluid mechanics – the occurrence of a flow classified as turbulent, with chaotic and random motion, what allows defining the ideal point of injection from analysis of velocity plots with stream lines. In addition, a Mach number smaller than 0.3 confirms the theory of having an incompressible flow, in which compressibility effects can be disregarded. The analysis of mass flow rates of the combustion zones made it possible to evaluate maximum differences of 3% between the design data and the one found in the study. To determine the inherent error of the mesh in the CFD study was calculated through the grid conference method, the value found was around 2.68%.
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Perpignan, André A. V., Stella Grazia Tomasello, and Arvind Gangoli Rao. "Evolution of Emission Species in an Aero-Engine Turbine Stator." Aerospace 8, no. 1 (2021): 11. http://dx.doi.org/10.3390/aerospace8010011.
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Future energy and transport scenarios will still rely on gas turbines for energy conversion and propulsion. Gas turbines will play a major role in energy transition and therefore gas turbine performance should be improved, and their pollutant emissions decreased. Consequently, designers must have accurate performance and emission prediction tools. Usually, pollutant emission prediction is limited to the combustion chamber as the composition at its outlet is considered to be “chemically frozen”. However, this assumption is not necessarily valid, especially with the increasing turbine inlet temperatures and operating pressures that benefit engine performance. In this work, Computational Fluid Dynamics (CFD) and Chemical Reactor Network (CRN) simulations were performed to analyse the progress of NOx and CO species through the high-pressure turbine stator. Simulations considering turbulence-chemistry interaction were performed and compared with the finite-rate chemistry approach. The results show that progression of some relevant reactions continues to take place within the turbine stator. For an estimated cruise condition, both NO and CO concentrations are predicted to increase along the stator, while for the take-off condition, NO increases and CO decreases within the stator vanes. Reaction rates and concentrations are correlated with the flow structure for the cruise condition, especially in the near-wall flow field and the blade wakes. However, at the higher operating pressure and temperature encountered during take-off, reactions seem to be dependent on the residence time rather than on the flow structures. The inclusion of turbulence-chemistry interaction significantly changes the results, while heat transfer on the blade walls is shown to have minor effects.
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Pietrzyk, J. R., D. G. Bogard, and M. E. Crawford. "Hydrodynamic Measurements of Jets in Crossflow for Gas Turbine Film Cooling Applications." Journal of Turbomachinery 111, no. 2 (1989): 139–45. http://dx.doi.org/10.1115/1.3262248.
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This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow. Laser-Doppler anemometry was used to measure the vertical and streamwise components of velocity for three jet-to-mainstream velocity ratios: 0.25, 0.5, and 1.0. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and mainstream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer. The data indicate the existence of a separation region in the hole from which the jet issues, causing high levels of turbulence and a relatively uniform mean velocity profile at the jet exit.
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Kestoras, M. D., and T. W. Simon. "Effects of Free-Stream Turbulence Intensity on a Boundary Layer Recovering From Concave Curvature Effects." Journal of Turbomachinery 117, no. 2 (1995): 240–47. http://dx.doi.org/10.1115/1.2835652.
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Experiments are conducted on a flat recovery wall downstream of sustained concave curvature in the presence of high free-stream turbulence (TI ∼ 8%). This flow simulates some of the features of the flow on the latter parts of the pressure surface of a gas turbine airfoil. The combined effects of concave curvature and TI, both present in the flow over a turbine airfoil, have so far been little studied. Computation of such flows with standard turbulence closure models has not been particularly successful. This experiment attempts to characterize the turbulence characteristics of this flow. In the present study, a turbulent boundary layer grows from the leading edge of a concave wall, then passes onto a downstream flat wall. Results show that turbulence intensities increase profoundly in the outer region of the boundary layer over the recovery wall. Near-wall turbulent eddies appear to lift off the recovery wall and a “stabilized” region forms near the wall. In contrast to a low-free-stream turbulence intensity flow, turbulent eddies penetrate the outer parts of the “stabilized” region where sharp velocity and temperature gradients exist. These eddies can more readily transfer momentum and heat. As a result, skin friction coefficients and Stanton numbers on the recovery wall are 20 and 10 percent, respectively, above their values in the low-free-stream turbulence intensity case. Stanton numbers do not undershoot flat-wall expectations at the same Reδ2 values as seen in the low-TI case. Remarkably, the velocity distribution in the core of the flow over the recovery wall exhibits a negative gradient normal to the wall under high-free-stream turbulence intensity conditions. This velocity distribution appears to be the result of two effects: (1) cross transport of kinetic energy by boundary work in the upstream curved flow and (2) readjustment of static pressure profiles in response to the removal of concave curvature.
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Dmitrenko, Artur. "Determination of Critical Reynolds Number for the Flow Near a Rotating Disk on the Basis of the Theory of Stochastic Equations and Equivalence of Measures." Fluids 6, no. 1 (2020): 5. http://dx.doi.org/10.3390/fluids6010005.
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The determination of the flow regime of liquid and gas in power plants is the most important design task. Performing the calculations based on modern calculation methods requires a priori knowledge of the initial and boundary conditions, which significantly affect the final results. The purpose of the article is to present the solution for the critical Reynolds number for the flow near a rotating disk on the basis of the theory of stochastic equations of continuum laws and equivalence of measures between random and deterministic motions. The determination of the analytical dependence for the critical Reynolds number is essential for the study of flow regimes and the thermal state of disks and blades in the design of gas and steam turbines. The result of the calculation with using the new formula shows that for the flow near a wall of rotating disk, the critical Reynolds number is 325,000, when the turbulent Reynolds is 5 ÷ 10 and the degree of turbulence is 0.01 ÷ 0.02. Therefore, the result of solution shows a satisfactory correspondence of the obtained analytical dependence for the critical Reynolds number with the experimental data.
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Lewis, Paul, Mike Wilson, Gary Lock, and J. Michael Owen. "Physical Interpretation of Flow and Heat Transfer in Preswirl Systems." Journal of Engineering for Gas Turbines and Power 129, no. 3 (2006): 769–77. http://dx.doi.org/10.1115/1.2436572.
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This paper compares heat transfer measurements from a preswirl rotor–stator experiment with three-dimensional (3D) steady-state results from a commercial computational fluid dynamics (CFD) code. The measured distribution of Nusselt number on the rotor surface was obtained from a scaled model of a gas turbine rotor–stator system, where the flow structure is representative of that found in an engine. Computations were carried out using a coupled multigrid Reynolds-averaged Navier-Stokes (RANS) solver with a high Reynolds number k-ε∕k-ω turbulence model. Previous work has identified three parameters governing heat transfer: rotational Reynolds number (Reϕ), preswirl ratio (βp), and the turbulent flow parameter (λT). For this study rotational Reynolds numbers are in the range 0.8×106<Reϕ<1.2×106. The turbulent flow parameter and preswirl ratios varied between 0.12<λT<0.38 and 0.5<βp<1.5, which are comparable to values that occur in industrial gas turbines. Two performance parameters have been calculated: the adiabatic effectiveness for the system, Θb,ad, and the discharge coefficient for the receiver holes, CD. The computations show that, although Θb,ad increases monotonically as βp increases, there is a critical value of βp at which CD is a maximum. At high coolant flow rates, computations have predicted peaks in heat transfer at the radius of the preswirl nozzles. These were discovered during earlier experiments and are associated with the impingement of the preswirl flow on the rotor disk. At lower flow rates, the heat transfer is controlled by boundary-layer effects. The Nusselt number on the rotating disk increases as either Reϕ or λT increases, and is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations are observed. The computed velocity field is used to explain the heat transfer distributions observed in the experiments. The regions of peak heat transfer around the receiver holes are a consequence of the route taken by the flow. Two routes have been identified: “direct,” whereby flow forms a stream tube between the inlet and outlet; and “indirect,” whereby flow mixes with the rotating core of fluid.
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Rodi, W., and G. Scheuerer. "Calculation of Heat Transfer to Convection-Cooled Gas Turbine Blades." Journal of Engineering for Gas Turbines and Power 107, no. 3 (1985): 620–27. http://dx.doi.org/10.1115/1.3239781.
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A mathematical model is presented for calculating the external heat transfer coefficients around gas turbine blades. The model is based on a finite-difference procedure for solving the boundary-layer equations which describe the flow and temperature field around the blades. The effects of turbulence are simulated by a low-Reynolds number version of the k-ε turbulence model. This allows calculation of laminar and transitional zones and also the onset of transition. Applications of the calculation method are presented to turbine-blade situations which have recently been investigated experimentally. Predicted and measured heat transfer coefficients are compared and good agreement with the data is observed. This is true especially for the pressure-surface boundary layer which is of a rather complex nature because it remains in a transitional state over the full blade length. The influence of various flow phenomena like laminar-turbulent transition and of the boundary conditions (pressure gradient, free-stream turbulence) on the predicted heat transfer rates is discussed.
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Wang, Guoliang, Ning Ge, and Dongdong Zhong. "Numerical Investigation of the Wake Vortex-Related Flow Mechanisms in Transonic Turbines." International Journal of Aerospace Engineering 2020 (August 1, 2020): 1–18. http://dx.doi.org/10.1155/2020/8825542.
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As the core equipment of the power generation system, a gas turbine is an indispensable energy-converting device in the national industry. The flow inside a high-pressure turbine (HPT) is highly unsteady, which has a great influence on the aerothermal performance and structural strength. To better clarify the flow mechanism and guide the advanced design, the basic flow characteristics of transonic turbines are investigated in the paper by a modified scale-adaptive simulation (SAS) model based on the shear stress transport (SST) turbulence model. The numerical results reveal the formation and development of the secondary flow structures such as wake vortex, pressure wave, shock wave, and the interactions among them. The length and frequency characteristics of wake are in good agreement with the large eddy simulation (LES) and the experimental data. Based on the detailed flow information, the local loss analysis is performed using the entropy generation rate. In summary, the wake vortex-related flow is the main origin of unsteadiness and entropy loss in high-pressure turbine cascade.
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Relation, H. L., J. L. Battaglioli, and W. F. Ng. "Numerical Simulations of Nonreacting Flows for Industrial Gas Turbine Combustor Geometries." Journal of Engineering for Gas Turbines and Power 120, no. 3 (1998): 460–67. http://dx.doi.org/10.1115/1.2818167.
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This study evaluates the application of the computational fluid dynamics (CFD) to calculate the flowfields in industrial combustors. Two-burner test cases, which contain the elemental flow characteristics of an industrial gas turbine combustor, are studied. Comparisons were made between the standard k-epsilon turbulence model and a modified version of the k-epsilon turbulence model. The modification was based on the work of Chen and Kim in which a second time scale was added to the turbulent dissipation equation. Results from the CFD calculations were compared to experimental data. For the two-burner test cases under study, the standard k-epsilon model diffuses the swirl and axial momentum, which results in the inconsistent prediction of the location of the recirculation zone for both burner test cases. However, the modified k-epsilon model shows an improved prediction of the location, shape, and size of the primary centerline recirculation zone for both cases. The large swirl and axial velocity gradients, which are diffused by the standard k-epsilon; model, are preserved by the modified model, and good agreements were obtained between the calculated and measured axial and swirl velocities. The overprediction of turbulent eddy viscosity in regions of high shear, which is characteristic of the standard k-epsilon model, is controlled by the modified turbulence model.
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Fureby, C. "Large eddy simulation modelling of combustion for propulsion applications." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, no. 1899 (2009): 2957–69. http://dx.doi.org/10.1098/rsta.2008.0271.
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Predictive modelling of turbulent combustion is important for the development of air-breathing engines, internal combustion engines, furnaces and for power generation. Significant advances in modelling non-reactive turbulent flows are now possible with the development of large eddy simulation (LES), in which the large energetic scales of the flow are resolved on the grid while modelling the effects of the small scales. Here, we discuss the use of combustion LES in predictive modelling of propulsion applications such as gas turbine, ramjet and scramjet engines. The LES models used are described in some detail and are validated against laboratory data—of which results from two cases are presented. These validated LES models are then applied to an annular multi-burner gas turbine combustor and a simplified scramjet combustor, for which some additional experimental data are available. For these cases, good agreement with the available reference data is obtained, and the LES predictions are used to elucidate the flow physics in such devices to further enhance our knowledge of these propulsion systems. Particular attention is focused on the influence of the combustion chemistry, turbulence–chemistry interaction, self-ignition, flame holding burner-to-burner interactions and combustion oscillations.
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Kumar, Ujjal, Chamely Khatun, Md Sakinul Islam, et al. "Effect of Drum Pressure on Flow Accelerated Corrosion in Gas Fired Combined Cycle Power Plant: A Case Study and Literature Review." Research Communication in Engineering Science & Technology 2 (December 5, 2019): 17–27. http://dx.doi.org/10.22597/rcest.v2.59.
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The dissolution of ferrous ions from the protective oxide layer and/or base metal by corrosion with the assistance of turbulent flow is called flow accelerated corrosion (FAC). Flow accelerated corrosion is the most common and continuous corrosion reaction in combined cycle power plants (CCPP). Heat recovery steam generator (HRSG) drum pressure fluctuation and/or turbulent drum water greatly influences the FAC of drum and economizer. This kind of FAC was investigated in the low-pressure drum (LPD) and low-pressure economizer (LPE) of a 210 MW gas-fired combined cycle power plant (Four-unit HRSG & GT) with an air-cooled condenser (ACC). Severe FAC was observed due to the fluctuation of pressure in the LPD with respect to time. As a result, huge amounts of soluble iron (Fe2+) and insoluble (Fe3+) was found in all running HRSG’s LPD water. Due to pressure fluctuations in the LPD, a protective oxide layer (mostly magnetite), as well as the base metal, were corroded from the LPD and LPE even after carefully maintaining recently developed water cycle chemistry in this CCPP. Severe leakage was found in the LPE due to corrosion. The actual reason for the problem was found to be a malfunctioning steam-control valve in the turbine unit’s LP system. This valve was malfunctioning by suddenly opening to 100% and then closing to around 10% continuously. This malfunction creates enormous pressure drops in both the LPD and LPE units. It is understood that water turbulence is the main cause of FAC affecting the LDP and LPE. This assessment is based on chemical laboratory analysis and physical inspection. There was no non-destructive testing (NDT) performed in this study. The severe FAC happened in four days and for this reason, HRSG and steam turbines were shut down. Maintenance work on the control valve and flushing of the LPD and LPE successfully resolved the FAC problem. One week later, LPE leakage was found on the unit-3 HRSG and as reported in this study this was also found to be the result of FAC. From this case study, it is concluded that not only water quality but also water turbulence can create severe FAC problem.
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Fořt, Ivan, Vladimír Rogalewicz, and Miroslav Richter. "Simulation of mechanically stirred two-phase liquid-gas flow." Collection of Czechoslovak Chemical Communications 51, no. 5 (1986): 1001–15. http://dx.doi.org/10.1135/cccc19861001.
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The study describes simulation of the motion of bubbles in gas, dispersed by a mechanical impeller in a turbulent low-viscosity liquid flow. The model employs the Monte Carlo method and it is based both on the knowledge of the mean velocity field of mixed liquid (mean motion) and of the spatial distribution of turbulence intensity ( fluctuating motion) in the investigated system - a cylindrical tank with radial baffles at the wall and with a standard (Rushton) turbine impeller in the vessel axis. Motion of the liquid is then superimposed with that of the bubbles in a still environment (ascending motion). The computation of the simulation includes determination of the spatial distribution of the gas holds-up (volumetric concentrations) in the agitated charge as well as of the total gas hold-up system depending on the impeller size and its frequency of revolutions, on the volumetric gas flow rate and the physical properties of gas and liquid. As model parameters, both liquid velocity field and normal gas bubbles distribution characteristics are considered, assuming that the bubbles in the system do not coalesce.
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Su, Gao, G. Y. Zhou, and Fei Du. "Numercial Simulation on Three-Dimensional Unsteady Flow in a Supercharged Boiler Gas Turbine." Applied Mechanics and Materials 271-272 (December 2012): 1039–43. http://dx.doi.org/10.4028/www.scientific.net/amm.271-272.1039.
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To the unsteady characteristic of three-dimensional flow in the gas turbine blade cascades, based on sliding mesh and a standard turbulent flow model, Fluent software was employed to solve the Reynolds averaged N-S equation. The numberical result of unsteady flow field is obtained in gas turbine cascade for supercharged marine boiler. This paper shows the axial distribution of Ma in the position of β=0 in a calculational period time, and the effect of trails to flow field characteristics. The result can provide guidelines for aerodynamic optimization design of gas turbine stage cascade.
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Georgiou, D. P., and J. F. Louis. "The Transpired Turbulent Boundary Layer in Various Pressure Gradients and the Blow-Off Condition." Journal of Engineering for Gas Turbines and Power 107, no. 3 (1985): 636–41. http://dx.doi.org/10.1115/1.3239783.
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An experimental study of the reduction in heat transfer to a transpiration-cooled flat surface subjected to pressure gradients (zero, negative, and positive) is presented for flow conditions similar to those encountered in gas turbines. The investigation is carried out for high injection rates and determines the blow-off conditions under which the boundary layer is lifted away from the wall by the transpired coolant. The study was conducted in a hot blow-down wind tunnel facility. The transient nature of the facility ensures that the wall remains isothermal. The Reynolds number, the ratio of the gas to wall temperatures, and the pressure gradient parameters K are chosen to be representative of the conditions found in advanced gas turbines. The effect of the pressure gradient was found to be small. However, a local strong acceleration can reduce the cooling effectiveness. The heat transfer rates or Stanton numbers on a solid surface downstream of a transpiration cooled wall are found to be sensitive to the upstream injection ratio (b) and to the pressure gradient parameter. The data indicate that the ratio of Stanton numbers with and without cooling is nonzero for values of the injection parameters larger than values obtained theoretically by Kutateladze. The predicted value of the critical injection ratio (bcr) determined from this study agrees well with the experimental data of Liepmann and Laufer for a free mixing layer, which is similar to a transpired boundary layer near blow-off as pointed out by Coles.
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Arthur, Robert S., Jeffrey D. Mirocha, Nikola Marjanovic, et al. "Multi-Scale Simulation of Wind Farm Performance during a Frontal Passage." Atmosphere 11, no. 3 (2020): 245. http://dx.doi.org/10.3390/atmos11030245.
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Predicting the response of wind farms to changing flow conditions is necessary for optimal design and operation. In this work, simulation and analysis of a frontal passage through a utility scale wind farm is achieved for the first time using a seamless multi-scale modeling approach. A generalized actuator disk (GAD) wind turbine model is used to represent turbine–flow interaction, and results are compared to novel radar observations during the frontal passage. The Weather Research and Forecasting (WRF) model is employed with a nested grid setup that allows for coupling between multi-scale atmospheric conditions and turbine response. Starting with mesoscale forcing, the atmosphere is dynamically downscaled to the region of interest, where the interaction between turbulent flows and individual wind turbines is simulated with 10 m grid spacing. Several improvements are made to the GAD model to mimic realistic turbine operation, including a yawing capability and a power output calculation. Ultimately, the model is able to capture both the dynamics of the frontal passage and the turbine response; predictions show good agreement with observed background velocity, turbine wake structure, and power output after accounting for a phase shift in the mesoscale forcing. This study demonstrates the utility of the WRF-GAD model framework for simulating wind farm performance under complex atmospheric conditions.
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Kálal, Zbyněk, Milan Jahoda, and Ivan Fořt. "CFD Prediction of Gas-Liquid Flow in an Aerated Stirred Vessel Using the Population Balance Model." Chemical and Process Engineering 35, no. 1 (2014): 55–73. http://dx.doi.org/10.2478/cpe-2014-0005.
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Abstract The main topic of this study is the experimental measurement and mathematical modelling of global gas hold-up and bubble size distribution in an aerated stirred vessel using the population balance method. The air-water system consisted of a mixing tank of diameter T = 0.29 m, which was equipped with a six-bladed Rushton turbine. Calculations were performed with CFD software CFX 14.5. Turbulent quantities were predicted using the standard k-ε turbulence model. Coalescence and breakup of bubbles were modelled using the homogeneous MUSIG method with 24 bubble size groups. To achieve a better prediction of the turbulent quantities, simulations were performed with much finer meshes than those that have been adopted so far for bubble size distribution modelling. Several different drag coefficient correlations were implemented in the solver, and their influence on the results was studied. Turbulent drag correction to reduce the bubble slip velocity proved to be essential to achieve agreement of the simulated gas distribution with experiments. To model the disintegration of bubbles, the widely adopted breakup model by Luo & Svendsen was used. However, its applicability was questioned.
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Biswas, D., та Y. Fukuyama. "Calculation of Transitional Boundary Layers With an Improved Low-Reynolds-Number Version of the k–ε Turbulence Model". Journal of Turbomachinery 116, № 4 (1994): 765–73. http://dx.doi.org/10.1115/1.2929471.
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Several well-known low-Reynolds-number versions of the k–ε models are analyzed critically for laminar to turbulent transitional flows as well as near-wall turbulent flows from a theoretical and numerical standpoint. After examining apparent problems associated with the modeling of low-Reynolds-number wall damping functions used in these models, an improved version of the k–ε model is proposed by defining the wall damping factors as a function of some quantity (turbulence Reynolds number Ret) that is only a rather general indicator of the degree of turbulent activity at any location in the flow rather than a specific function of the location itself, and by considering the wall limiting behavior, the free-stream asymptotic behavior, and the balance between production and destruction of turbulence. This new model is applied to the prediction of (1) transitional boundary layers influenced by the free-stream turbulence, pressure gradient, and heat transfer; (2) external heat transfer distribution on the gas turbine rotor and stator blade under different inlet Reynolds number and free-stream turbulence conditions. It is demonstrated that the present model yields improved predictions.
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Colban, W. F., A. T. Lethander, K. A. Thole, and G. Zess. "Combustor Turbine Interface Studies—Part 2: Flow and Thermal Field Measurements." Journal of Turbomachinery 125, no. 2 (2003): 203–9. http://dx.doi.org/10.1115/1.1561812.
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Most turbine inlet flows resulting from the combustor exit are nonuniform in the near-platform region as a result of cooling methods used for the combustor liner. These cooling methods include injection through film-cooling holes and injection through a slot that connects the combustor and turbine. This paper presents thermal and flow field measurements in the turbine vane passage for a combustor exit flow representative of what occurs in a gas turbine engine. The experiments were performed in a large-scale wind tunnel facility that incorporates combustor and turbine vane models. The measured results for the thermal and flow fields indicate a secondary flow pattern in the vane passage that can be explained by the total pressure profile exiting the combustor. This secondary flow field is quite different than that presented for past studies with an approaching flat plate turbulent boundary layer along the upstream platform. A counter-rotating vortex that is positioned above the passage vortex was identified from the measurements. Highly turbulent and highly unsteady flow velocities occur at flow impingement locations along the stagnation line.
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Bai, Xue-Song, and Laszlo Fuchs. "Sensitivity study of turbulent reacting flow modeling in gas turbine combustors." AIAA Journal 33, no. 10 (1995): 1857–64. http://dx.doi.org/10.2514/3.12738.
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Contini, Daniele, Marco Ruggiero, and Giampaolo Manfrida. "Turbulent flow field measurements in a model gas turbine combustion chamber." Revue Générale de Thermique 37, no. 10 (1998): 843–52. http://dx.doi.org/10.1016/s0035-3159(98)80009-3.
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MANDAI, Shigemi, and Hiroyuki NISHIDA. "Application of Turbulent Reacting Flow Analysis in Gas Turbine Combustor Development." JSME International Journal Series B 47, no. 1 (2004): 108–14. http://dx.doi.org/10.1299/jsmeb.47.108.
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MANDAI, Shigemi, and Hiroyuki NISHIDA. "Application of Turbulent Reacting Flow Analysis for Gas Turbine Combustor Development." Transactions of the Japan Society of Mechanical Engineers Series B 68, no. 676 (2002): 3481–86. http://dx.doi.org/10.1299/kikaib.68.3481.
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Lock, Gary D., Youyou Yan, Paul J. Newton, Michael Wilson, and J. Michael Owen. "Heat Transfer Measurements Using Liquid Crystals in a Preswirl Rotating-Disk System." Journal of Engineering for Gas Turbines and Power 127, no. 2 (2005): 375–82. http://dx.doi.org/10.1115/1.1787509.
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Preswirl nozzles are often used in gas turbines to deliver the cooling air to the turbine blades through receiver holes in a rotating disk. The distribution of the local Nusselt number, Nu, on the rotating disk is governed by three nondimensional fluid-dynamic parameters: preswirl ratio, βp, rotational Reynolds number, Reϕ, and turbulent flow parameter, λT. A scaled model of a gas turbine rotor–stator cavity, based on the geometry of current engine designs, has been used to create appropriate flow conditions. This paper describes how a thermochromic liquid crystal, in conjunction with a stroboscopic light and digital camera, is used in a transient experiment to obtain contour maps of Nu on the rotating disk. The thermal boundary conditions for the transient technique are such that an exponential-series solution to Fourier’s one-dimensional conduction equation is necessary. A method to assess the uncertainty in the measurements is discussed and these uncertainties are quantified. The experiments reveal that Nu on the rotating disk is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations have been measured. At the higher coolant flow rates studied, there is a peak in heat transfer at the radius of the preswirl nozzles. The heat transfer is governed by two flow regimes: one dominated by inertial effects associated with the impinging jets from the preswirl nozzles, and another dominated by viscous effects at lower flow rates. The Nusselt number is observed to increase as either Reϕ or λT increases.
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Tolpadi, A. K. "Calculation of Two-Phase Flow in Gas Turbine Combustors." Journal of Engineering for Gas Turbines and Power 117, no. 4 (1995): 695–703. http://dx.doi.org/10.1115/1.2815455.
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A method is presented for computing steady two-phase turbulent combusting flow in a gas turbine combustor. The gas phase equations are solved in an Eulerian frame of reference. The two-phase calculations are performed by using a liquid droplet spray combustion model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of reference. The numerical algorithm employs nonorthogonal curvilinear coordinates, a multigrid iterative solution procedure, the standard k-ε turbulence model, and a combustion model comprising an assumed shape probability density function and the conserved scalar formulation. The trajectory computation of the fuel provides the source terms for all the gas phase equations. This two-phase model was applied to a real piece of combustion hardware in the form of a modern GE/SNECMA single annular CFM56 turbofan engine combustor. For the purposes of comparison, calculations were also performed by treating the fuel as a single gaseous phase. The effect on the solution of two extreme situations of the fuel as a gas and initially as a liquid was examined. The distribution of the velocity field and the conserved scalar within the combustor, as well as the distribution of the temperature field in the reaction zone and in the exhaust, were all predicted with the combustor operating both at high-power and low-power (ground idle) conditions. The calculated exit gas temperature was compared with test rig measurements. Under both low and high-power conditions, the temperature appeared to show an improved agreement with the measured data when the calculations were performed with the spray model as compared to a single-phase calculation.
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Hossain, Mohammad A., Ahsan Choudhuri, and Norman Love. "Design of an optically accessible turbulent combustion system." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 1 (2018): 336–49. http://dx.doi.org/10.1177/0954406218757565.
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In order to design the next generation of gas turbine combustors and rocket engines, understanding the flame structure at high-intensity turbulent flows is necessary. Many experimental studies have focused on flame structures at relatively low Reynolds and Damköhler numbers, which are useful but do not help to provide a deep understanding of flame behavior at gas turbine and rocket engine operating conditions. The current work is focused on the presentation of the design and development of a high-intensity (Tu = 15–30%) turbulent combustion system, which is operated at compressible flow regime from Mach numbers of 0.3 to 0.5, preheated temperatures up to 500 K, and premixed conditions in order to investigate the flame structure at high Reynolds and Damköhler numbers in the so-called thickened flame regime. The design of an optically accessible backward-facing step stabilized combustor was designed for a maximum operating pressure of 0.6 MPa. Turbulence generator grid was introduced with different blockage ratios from 54 to 67% to generate turbulence inside the combustor. Optical access was provided via quartz windows on three sides of the combustion chamber. Extensive finite element analysis was performed to verify the structural integrity of the combustor at rated conditions. In order to increase the inlet temperature of the air, a heating section is designed and presented in this paper. Separate cooling subsystem designs are also presented. A 10 kHz time-resolved particle image velocimetry system and a 3 kHz planer laser-induced fluorescence system are integrated with the system to diagnose the flow field and the flame, respectively. The combustor utilizes a UNS 316 stainless steel with a minimum wall thickness of 12.5 mm. Quartz windows were designed with a maximum thickness of 25.4 mm resulting in an overall factor of safety of 3.5.
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Polanka, Marc D., J. Michael Cutbirth, and David G. Bogard. "Three Component Velocity Field Measurements in the Stagnation Region of a Film Cooled Turbine Vane." Journal of Turbomachinery 124, no. 3 (2002): 445–52. http://dx.doi.org/10.1115/1.1459733.
Full textAbstract:
The showerhead region of a film-cooled turbine vane in a gas turbine engine involves a complex interaction between mainstream flow and coolant jets. This flow field was studied using three component laser Doppler velocimeter measurements in a simulated turbine vane test facility. Measurements were focused around the stagnation row of holes. Low and high mainstream turbulence conditions were used. The spanwise orientation of the coolant jets, typical for showerhead coolant holes, had a dominating effect. Very high levels of turbulence were generated by the mainstream interaction with the coolant jets. Furthermore, this turbulence was highly anisotropic, with the spanwise component of the turbulent fluctuations being twice as large as the other components. Finally, there was an interaction of the high mainstream turbulence with the coolant injection resulting in increased turbulence levels for the spanwise velocity component, but had little effect on the other velocity components.
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James, S., M. S. Anand, M. K. Razdan, and S. B. Pope. "In Situ Detailed Chemistry Calculations in Combustor Flow Analyses." Journal of Engineering for Gas Turbines and Power 123, no. 4 (1999): 747–56. http://dx.doi.org/10.1115/1.1384878.
Full textAbstract:
In the numerical simulation of turbulent reacting flows, the high computational cost of integrating the reaction equations precludes the inclusion of detailed chemistry schemes, therefore reduced reaction mechanisms have been the more popular route for describing combustion chemistry, albeit at the loss of generality. The in situ adaptive tabulation scheme (ISAT) has significantly alleviated this problem by facilitating the efficient integration of the reaction equations via a unique combination of direct integration and dynamic creation of a look-up table, thus allowing for the implementation of detailed chemistry schemes in turbulent reacting flow calculations. In the present paper, the probability density function (PDF) method for turbulent combustion modeling is combined with the ISAT in a combustor design system, and calculations of a piloted jet diffusion flame and a low-emissions premixed gas turbine combustor are performed. It is demonstrated that the results are in good agreement with experimental data and computations of practical turbulent reacting flows with detailed chemistry schemes are affordable.
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Mayle, R. E., K. Dullenkopf, and A. Schulz. "1997 Best Paper Award—Heat Transfer Committee: The Turbulence That Matters." Journal of Turbomachinery 120, no. 3 (1998): 402–9. http://dx.doi.org/10.1115/1.2841731.
Full textAbstract:
A unified expression for the spectrum of turbulence is developed by asymptotically matching known expressions for small and large wave numbers, and a formula for the one-dimensional spectral function, which depends on the turbulence Reynolds number Reλ, is provided. In addition, formulas relating all the length scales of turbulence are provided. These relations also depend on Reynolds number. The effects of free-stream turbulence on laminar heat transfer and pretransitional flow in gas turbines are re-examined in light of these new expressions using our recent thoughts on an “effective” frequency of turbulence and an “effective” turbulence level. The results of this are that the frequency most effective for laminar heat transfer is about 1.3 U/2πLe, where U is the free-stream velocity and Le is the length scale of the eddies containing the most turbulent energy, and the most effective frequency for producing pretransitional boundary layer fluctuations is about 0.3 U/2πη, where η is Kolmogorov’s length scale. In addition, the role of turbulence Reynolds number on stagnation heat transfer and transition is discussed, and new expressions to account for its effect are provided.
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Baskharone, E. A. "Finite-Element Analysis of Turbulent Flow in Annular Exhaust Diffusers of Gas Turbine Engines." Journal of Fluids Engineering 113, no. 1 (1991): 104–10. http://dx.doi.org/10.1115/1.2926479.
Full textAbstract:
A finite-element model of the turbulent flow field in the annular exhaust diffuser of a gas turbine engine is developed. The analysis is based on a modified version of the Petrov-Galerkin weighted residual method, coupled with a highly accurate biquadratic finite element of the Lagrangian type. The elemental weight functions in the finite-element formulation are so defined to ensure upwinding of the convection terms in the flow-governing equations while reverting to the conventional Galerkin’s definition for all other terms. This approach is equivalent to altering the integration algorithm as the convection terms in the element equations are derived, with the exception that the latter technique is tailored for low-order elements of the linear and bilinear types. Numerical results of the current analysis indicate that spurious pressure modes associated with this type of inertia-dominated flow are alleviated while the false numerical diffusion in the finite-element equations is simultaneously minimized. Turbulence of the flow field is modeled using the two-layer algebraic turbulence closure of Baldwin and Lomax, and the eddy viscosity calculations are performed at variably spaced points which are different from those in the finite-element discretization model. This enhances the accuracy in computing the wall shear stress and the inner/outer layer interface location. The computational model is verified using a set of experimental data at design and off-design operation modes of the exhaust diffuser in a commercial gas turbine engine. Assessment of the results in this case is favorable and, as such, provides evidence of the model capability as an accurate predictive tool in the diffuser detailed design phase.