bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer Performance of a New Fan-Shaped Pin-Fin in Internal Cooling Channel
Authors: Moon Mi-Ae , Kim Kwang-Yong
Published: November 2013

Prediction of convective heat transfer around a pin-fin of novel fan-shape has been performed with Reynolds-averaged Navier-Stokes (RANS) analysis in comparison with a circular pin-fin. The low-Reynolds number shear stress transport (SST) model has been selected as the turbulence closure model by comparing the performance with those of the standard k-ε and k-ω models. The fan-shaped pin-fin has shown remarkably improved heat transfer performance compared to the circular pin-fin over the whole range of Reynolds number (Re = 5,000–100,000). A parametric study with two geometric parameters of the fan-shaped pin-fin, the lateral reduction angle of the fan-shaped pin-fin and radius of rear part of pin-fin has been performed to find their effects on heat transfer and friction loss.
An Experimental and Numerical Investigation on Endwall Film Cooling
Authors: Wang Jianhua , Wang Xiaochun , Zhao Lianjin , He Fei , Ma Shiyan , Hao Changming
Published: November 2013

This paper presents an experimental and numerical investigation on the cooling performances of a flat endwall, which is made of super-alloy. The endwall passage is configured by two semi-profiled vanes. In the flat endwall, there are 34 cylindrical film holes located at the leading edge region, near the pressure side and upstream inlet, respectively. The experiments were carried out in the hot wind tunnel at the University of Science and Technology of China. Cooling characteristics were captured at different blowing ratios and mainstream temperatures by an infrared thermal image system. The experiments exhibited an interesting phenomenon, i.e. one can get a similar temperature contour at different mainstream and coolant temperatures but the same other conditions if using the maximal and minimal temperatures as the limit values in the contour scale. The experimental data were used to validate the numerical strategy. To demonstrate this similar phenomenon at the real condition of gas turbine operations, numerical simulations were conducted. The numerical results indicated that at the same blowing ratio and mainstream Reynolds number, when mainstream temperature varies from 1700K to 1950K but cooling air temperature keeps at 850K, or the cooling air temperature changes from 750K to 950K but the mainstream temperature keeps at 1700K, the temperature contours generated by the scale of nature maximal and minimal temperatures are very similar. Using linear relationships to fit these maximal and minimal temperatures in the contour scales, the maximal fitting error is less than 0.1%. Using the similar phenomenon and linear relationships, one can easily predict any cooling effect at the condition between two experimental states or two simulation conditions. Therefore this similarity is very useful for the experimental investigations into endwall cooling performances and the design of film cooling configurations.
Flow-Field and Conjugate Heat Transfer of an Internally Air-Cooled Nozzle Guide Vane and Shrouds
Authors: Jiang Leiyong
Published: November 2013

In order to assess the life of gas turbine critical components, it is essential to adequately specify their aero-thermodynamic working environments. Steady-state analyses of the flow field and conjugate heat transfer of an internally air-cooled nozzle guide vane (NGV) and shrouds of a gas turbine engine at the baseline operating conditions are numerically investigated. A high-fidelity CFD model is generated and the simulations are carried out with properly defined boundary conditions. The features of the complicated flow and temperature fields are revealed. In general, the Mach number is lower and the temperature is higher on the NGV pressure side than those on the suction side. There are two high temperature spots on the pressure side, and the temperature across the NGV middle section is relatively low. These findings are closely related to the locations of the holes and outlets of the cooling flow passage, and consistent with the field observation of damaged NGVs. The obtained results provide essential information for the structural, material and life analyses of the NGV/shrouds assembly, and improvement of the cooling flow arrangement.
Numerical Simulation of Flow and Heat Transfer in Rotating Cooling Passage With Turning Vane in Hub Region
Authors: Chu Hung-Chieh , Chen Hamn-Ching , Han Je-Chin
Published: November 2013

Numerical simulation of three-dimensional turbulent flow and heat transfer was performed in a multi-pass rectangular (AR = 2:1) rotating cooling channel with and without turning vane in the hub region under various flow conditions, with two different Reynolds numbers of 10000 and 25000, two different channel orientations of 45-deg and 90-deg., and the rotation number varies from 0 to 0.2. The present study provides detailed explanation on the dramatic flow change due to the turning vane. The numerical results show that the addition of vane in hub portion does not cause much impact to the flow before the turn. However, it greatly affects flow behaviors and heat transfer characteristics in the turning region and the third passage after the hub turn. Compared to the cases without turning vane, the vane clearly changes local flow pattern, divides the main flow into two separate streams, and alters the flow reattachment location and vortex distribution. The local heat transfer is influenced by this complex flow field and its effects last from the turn portion to the third passage.
Measurements of a Trailing Edge Slot Film Cooling Geometry Designed for Reduced Coolant Flowrate and High Surface Effectiveness
Authors: Ling Julia , Elkins Christopher J. , Benson Michael J. , Yapa Sayuri D. , Eaton John K.
Published: November 2013

A trailing edge slot film cooling configuration designed for enhanced surface effectiveness at a decreased coolant flowrate is proposed. Magnetic resonance imaging (MRI) techniques were used to obtain measurements of the mean 3D velocity and concentration fields. These measurements are compared to previously reported results on two other trailing edge configurations. The surface effectiveness of the proposed slot film cooling configuration is higher than that of the baseline configuration, even at a 25% lower coolant flowrate. The mean fields are used to calculate an isotropic, spatially-varying turbulent diffusivity for each of these trailing edge configurations. These diffusivities are compared to offer insight into the effect of land shape on turbulence properties.
The History of Marine Gas Turbine Development in China
Authors: Wen Xueyou , Lin Feng , Zou Jiguo
Published: November 2013

This paper presents a short glance at the early development (1958–1990) of the China’s marine gas turbine. In chronological order, the development of China’s marine gas turbine is divided into three stages, e.g. (1) Imitation, (2) Independent Development, and (3) Aero-derivative development stages. This paper describes the typical engines of each stage. The technical specifications, development process, finally, the experiences and lessons of each engine are also given.
Design Philosophy and Methodology of a Low Pressure Exhaust Hood for a Large Power Steam Turbine
Authors: Mizumi Shunsuke , Ishibashi Kouji
Published: November 2013

The efficiency of a steam turbine is significantly influenced by pressure recovery performance of its low-pressure exhaust hood; hence it is important to specify the cause of loss generation and to devise improved structures. The performance of the exhaust hood is greatly influenced by many structural factors such as the size of its outer casing, design of the diffuser parts and arrangement of internal supports.

Ideally, it would be preferable to take all those influential factors into consideration in designing an exhaust hood. However, it is neither cost-effective nor practicable to take everything into consideration at the same time, while it is mandatory to obtain a better shape in performance within reasonable time. For this reason, it is necessary to reach a compromise to some extent between the ideal and the realistic design methods.

In the present study, we propose the efficient design method of the downstream type low-pressure exhaust hood for large-scale steam turbines, utilizing the performance charts based on the extensive CFD parameter surveys.
Gas Turbines and Uncertainty Quantification: Impact of PDF Tails on UQ Predictions, the Black Swan
Authors: Montomoli Francesco , Massini Michela
Published: November 2013

In the last five years Uncertainty Quantification (UQ) techniques became popular to predict gas turbine performances. Taking into account the uncertainties in the input parameters it is possible to evaluate the impact of random variations and to overcome the limitations of deterministic studies. These methods, that only recently have been widely used in computational fluid dynamics, have some limitations that must be considered.

One of the most important limitations is that these models cannot predict a “Black Swan” (BS) event. In probability a Black Swan is an event rare, possible and with serious consequences. A reliable design requires a correct evaluation of the probabilities of occurrence of the Black Swan that could strongly affect the life of the turbine. Black Swans are generated by the variability of the input parameters in the “tail” of the statistical distributions. Being far from the mean value design geometry/condition, these events have a low probability of occurrence. In this paper is shown that the use of the Gaussian distribution for the input parameters could strongly underestimate the probability of occurrence of a Black Swan event. Despite that most of the models used in UQ for aerodesign are neglecting the problem.

As an example of Black Swan, the hot gas ingestion across a stator is analysed. The gaps have been assumed to be affected by uncertainty with a variation of +/-50% of the nominal value. By using a Monte Carlo simulation with 108 realizations and a Gauss distribution as input, the configuration is initially considered reliable. The six sigma criterion is also satisfied and the probability to have a failure is only 2.54 10−4%. However if a “fat tail” for the input distribution is used instead, the probability to have hot gas ingestion becomes 2.33%, 104 times higher.

Most of the methods used in literature aim to have an accurate reproduction of the PDF moments such as mean, standard deviation, skew and kurtosis. However the “tail” of the distribution affects the gas turbine life and must be considered. In particular “fat tails”, the mathematical origin of Black Swans events, can have serious consequences, but in modern stochastic models used for computational fluid dynamics they are not accounted for.
Characteristics of Flame Modes for a Conical Bluff Body Burner With a Central Fuel Jet
Authors: Tang Haojie , Yang Dong , Zhang Tongfeng , Zhu Min
Published: November 2013

Bluff body stabilised non-premixed flames are usually used as pilot flames in lean-premixed combustors. Experiments are conducted to investigate the characteristics of the flame. Typical flame modes are investigated in both stable and unstable conditions. The flow structures, the reaction zone, and the dynamics of unstable flames are measured with PIV, ICCD and a high speed camera, respectively, based on which the inherent mechanisms that influence the configuration and stabilisation of the flame are analysed. Stable flames are apparently influenced by the mixing characteristics in the recirculation zone. Flame detachment, a typical phenomenon of stable flames in a turbulent air flow, can be explained by the distribution of fuel concentration in the recirculation zone. The Reynolds number of air has different effects on different parts of the flame, which results in three unstable flame modes at different Reynolds numbers of air. These results could be helpful for the design of stable burners in practice.
Experimental Investigation Into Thermal Behavior of Steam Turbine Components: Part 3 — Startup and the Impact on LCF Life
Authors: Marinescu Gabriel , Sell Michael , Ehrsam Andreas , Brunner Philipp B.
Published: November 2013

Steam turbine start-up has a significant impact on the cyclic fatigue life. Modern steam turbines are operated at high temperatures for optimal efficiency, which results in high temperature differences relative to the condition before start-up. To achieve the fastest possible start-up time without reducing the lifetime of the turbine components due to excessive thermal stress, the start-up procedure of cyclic turbines is optimized to follow the specific material low cycle fatigue limit. For such optimization and to ensure reliable operation, it is essential to fully understand the thermal behavior of the components during start-up. This is especially challenging in low flow conditions, i.e. during pre-warming and early loading phase. A two-dimensional numerical procedure is described for the assessment of the thermal regime during start-up. The calculation procedure includes the rotor, casings, valves and main pipes. The concept of the start-up calculation is to replace the convective effect of the steam in the turbine cavity by an equivalent fluid over-conductivity that gives the same thermal effect on metallic parts. This approach allows simulating accurately the effect of steam ingestion during pre-warming phase. The fluid equivalent over-conductivity is calibrated with experimental data. At the end of the paper the impact of ingested steam temperature and mass-flow on the rotor cyclic lifetime is demonstrated. This paper is a continuation of papers [1] and [2].
Numerical Simulations of a Premixed Turbulent Confined Jet Flame Using the Flamelet Generated Manifold Approach With Heat Loss Inclusion
Authors: Donini A. , Martin S. M. , Bastiaans R. J. M. , van Oijen J. A. , de Goey L. P. H.
Published: November 2013

In the present paper a computational analysis of a confined premixed turbulent methane/air jet flame is presented. In this scope, chemistry is reduced by the use of the Flamelet Generated Manifold (FGM) method [1, 2], and the fluid flow is modeled in a RANS context. In the FGM technique the reaction progress of the flame is generally described by a few control variables, for which a transport equation is solved during runtime. The flamelet system is computed in a pre-processing stage, and a manifold with all the information about combustion is stored in a tabulated form. In the present implementation the reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the turbulence effect on the reaction is represented by the progress variable variance. The turbulence-chemistry interaction is considered through the use of a presumed pdf approach.

A generic lab scale burner for high-velocity preheated jets is used for validation [3, 4]. It consists of a rectangular confinement, and an off-center positioning of the jet nozzle enables flame stabilization by recirculation of hot combustion products. The inlet speed is appropriately high, in order to be close to the blow out limit. Flame structures were visualized by OH* chemiluminescence imaging and planar laser-induced fluorescence of the OH radical. Laser Raman scattering was used to determine concentrations of the major species and the temperature. Velocity fields were measured with particle image velocimetry.

The important effect of conductive heat loss to the walls is included in the FGM chemistry reduction method in a RANS context, in order to predict the evolution and description of a turbulent jet flame in high Reynolds number flow conditions. Comparisons of various mean fields (velocities, temperatures) with RANS results are shown. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable computational effort.
Evaluation of a Piloted Lean Injection System in Terms of Emission Performance and Flame Structure at Elevated Pressure
Authors: Harth Stefan , Zarzalis Nikolaos , Bauer Hans-Jörg , Turrini F.
Published: November 2013

A new compact injection system design for piloted lean combustion has been developed to reduce the pollutant emissions in aero engines. The system includes an integrated premixing zone to achieve a homogenous fuel distribution, so that peak temperatures in the combustor are avoided. This leads to low NOx emissions at lean conditions. The risks of flame flashback and auto ignition have been considered in the design and neither of them has been detected by the performed tests. To avoid the formation of a recirculation zone within the mixing zone an axial air jet has been introduced. This axial jet also works as an air assisted pilot fuel atomizer, which is a major innovation as compared to other lean injection systems using pressure-swirl atomizers for the pilot fuel like e.g. the PERM (Partial Evaporation and Rapid Mixing) concept developed in a previous research program [1], [2]. The main fuel injection of the current configuration is performed by four circumferentially arranged pressure swirl atomizers, which is also an alternative approach compared to previous concepts. The emission performance of the injection system using kerosene Jet A-1 has been investigated in a tubular combustor with air inlet temperatures up to 733 K and combustor pressures up to 10 bar. The dependencies of pilot fuel split, air to fuel ratio, combustor pressure and air inlet temperature on emissions have been determined. Over a wide range of operating conditions a low amount of pollutant emissions are achieved and the stability range is broadened by the pilot fuel injection. The flame structure has been analyzed by OH* chemiluminescence measurements. The Abel transformation technique has been applied to the images to generate the radial distribution. The main flame is lifted and its shape remains similar for different combustor pressures. The lift off height with only pilot fuel injection decreases with increasing combustor pressure and the flame shape is changing. This behavior is explained based on the effects of combustor pressure on fuel atomization, droplet traces and the distribution of evaporated fuel. The development and testing have been conducted in cooperation of AVIO and Karlsruhe Institute of Technology in the frame of the European Commission co-financed research project TECC-AE (Technology Enhancement for Clean Combustion in Aero Engines).
Numerical Investigations on the Cooling Performance of the Internal Bypass Cooling System of the Ultra-Supercritical Steam Turbines Using CFD and Conjugate Heat Transfer Method
Authors: Huo Wenhao , Li Jun , Yang Jiandao , Shi Liqun , Feng Zhenping
Published: November 2013

The cooling effect of the internal bypass cooling system in high pressure cylinder of an ultra-supercritical steam turbine using the conjugation of the flow calculation and heat transfer method was numerically studied in this paper. Three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions and k–ε turbulent model with scalable wall function were used to analyze the cooling performance based on the CFD software ANSYS-CFX. The details of the flow pattern of the fluid domains and temperature distributions of the solid domains in the system were illustrated. The temperature field of the high pressure cylinder was compared between the steam cooling case and the non-cooling case without consideration of the steam cooling of the internal bypass cooling system. The main conclusion that can be drawn out of this research work is that the high pressure inner casing and the large part of axial thrust balance piston can be effectively cooled by the internal bypass cooling system. In addition, the resulting temperature distributions of the inner casing are uniformed compared to the non-cooling case. The temperature of the outer casing of the high pressure cylinder increases a little compared to the non-cooling case.
Siemens SGT-300 Twin-Shaft DLE Engine Combustion System From Design to Engine Validation
Authors: Lam Kam-Kei , Liu Kexin , Jayatunga Charith , Helas Darrell
Published: November 2013

This paper presents the extension and optimization of the Siemens Industrial Turbomachinery Ltd Dry Low Emission combustion system from the existing SGT-300 Single-Shaft turbine to the new SGT-300 Twin-Shaft engine. The SGT-300 Twin-Shaft combustion development follows the Siemens Product Development Process and the new engine is now validated for introduction to the market.

Different designs are tested and optimized at full engine pressure and temperature conditions in Lincoln, UK Siemens combustion high pressure rig facility. Optimized combustion design is installed to the new design SGT-300 Twin-Shaft engine to validate in the Siemens gas turbine test bed in Lincoln, UK.

Blocker bars have been designed and applied to the combustion rig to capture the acoustic signature of the nozzle guide vane. Traverse is performed in the high pressure rig to identity the combustor exit hot gas temperature map.

Emission turndown to 50% load with NOx < 9 ppm and CO < 10 ppm capability is one of the major Key Performance Indicators. The SGT-300 Twin-Shaft combustion system is optimized for excellent emission behavior in this load range. Additionally, some of the compressor delivery air is bypassed around the combustor to exhaust through the air bleed system at part load.
A Numerical Model for Casing Treatment Applications in Axial Flow Compressors
Authors: Wolfrum Nina , Brignole Giovanni , Engel Karl
Published: November 2013

A numerical model has been developed to reproduce the effects of complex casing treatments (CT) in steady RANS simulations of multistage compressors. While some CTs, such as circumferential grooves, can be described by a rotation surface and can thus easily be included in conventional steady simulations, the CFD analysis of other casing treatments like axial slot or recessed vanes, currently requires a time-resolving analysis of the interaction between such structures and rotating parts. At present unsteady simulations are still too time consuming to be used in the early phase of a compressor design. In the presented study a numerical model was developed for casing treatment applications, to introduce the unsteady effects caused by such casing treatments into steady CFD-simulations. With the help of the model, non-axisymmetric elements can be eliminated from the geometry allowing a steady simulation to be used. The flow acceleration and redirection caused by these geometrical elements is replaced with adequate source terms introduced into the three-dimensional Navier-Stokes equations. These source terms, derived from a consecutive time- and circumferential averaging of the three-dimensional unsteady Reynolds-averaged Navier-Stokes-equations, arise from the momentum and energy equations. Using these additional terms, the CT-model simulates both the pressure forces that the walls of the real casing treatment exert on the flow, and the effects of the mean blockage induced by the omitted geometry. Furthermore, the deterministic stresses, caused by a circumferentially inhomogeneous flow within the CT-structure, are modeled. The source terms consist of geometrical data that can be derived directly from the real geometry of the casing treatment as well as physical quantities of the time-averaged flow in the real casing treatment. The latter terms can be obtained from a reference unsteady simulation. In the presented case one unsteady simulation was sufficient to set up the model for a complete speed line. The model was implemented into the three-dimensional Navier-Stokes-code TRACE [5][12]. By using steady instead of unsteady CFD simulations, the time required for a speedline computation was reduced by a factor of 10. At the same time, the numerical results of the CT-model showed good alignment with the reference data. The model was evaluated for several different styles of compressors. In this paper various results are presented, including speedlines as well as radial inflow- and outflow-profiles.
Investigation of a Premixed Gas Turbine Combustor Central Body Burner Using OH Planar Laser Induced Fluorescence at Elevated Pressures
Authors: Whiddon Ronald , Collin Robert , Alden Marcus , Sigfrid Ivan , Klingmann Jens
Published: November 2013

Experiments were performed on the central body rich-pilot-lean (RPL) burner of a Siemens Industrial Turbomachinary 4th generation DLE combustor to observe the combustion changes that may occur when using fuels other than natural gas. Measurements were taken of temperatures at multiple points along the RPL body while hydroxyl (OH) radical distribution extending from the dump plane of the burner was imaged by planar laser induced fluorescence (PLIF). The RPL burner was run using four fuels; methane, a generic syngas (67.5% H2, 22.5% CO and 10% CH4) and dilutions of these with nitrogen to a Wobbe index of 15 MJ/m3. Each of the fuels was operated at several equivalence ratios ranging from ϕ = 0.80 to ϕ = 1.80, for combustion pressures of 3, 6 and 9 bar. It was found that the flame position in the RPL, determined from temperature measurement at the thermocouple positions, was dependent on the fuel, equivalence ratio and to a lesser extent pressure. A link was established between the OH distribution in the post burner region and RPL temperature profiles based on the expected flame behavior inside the RPL. For all measurement points some combustion occurred within the burner volume, indicated by thermocouples at the burner exit.
Flow Investigations in the Tip Gap of Rotor Blade Tips With Squealer Cavity
Authors: Fischer Andreas , König Jörg , Czarske Jürgen , Rakenius Clemens , Schmid Gregor , Schiffer Heinz-Peter
Published: November 2013

The tip leakage flow in turbines is considered to be responsible/or significant machine losses. An efficient reduction of these losses by e. g. squealer cavities at rotor blade tips requires a detailed physical and quantitative understanding of the tip leakage flow. For this purpose, numerical flow simulations are a valuable tool, but they have to be validated by measurements. However, non-intrusive, optical flow measurements in a rotating machine are challenging due to the small tip gap dimensions.

Using an optimized optical setup, all three velocity components of the tip gap flow field were resolved while the turbine (1.5 stage low Mach number turbine test rig) was running with 930Hz blade passing frequency at the design point. The measurement results are in good qualitative agreement with numerical flow simulations. The gap flow above the squealer cavity is not homogeneous, but has several flow gradients, which mainly result from the blade tip geometry and the continuity of the flow. Furthermore, the flow structure between two successive rotor blades was resolved yielding the size and shape of the tip leakage vortex downstream at the suction side of the rotor blade in the measurement plane. Consequently, the capabilities of the applied measurement approach opens promising perspectives toward the development of optimum blade tip designs with minimized tip leakage.
A Preliminary Turbine Design for an Organic Rankine Cycle
Authors: Efstathiadis T. , Rivarolo M. , Kalfas A. I. , Traverso A. , Seferlis P.
Published: November 2013

An increasing trend in exploiting low enthalpy content energy sources, has led to a renewed interest in small-scale turbines for Organic Rankine Cycle applications. The design concept for such turbines can be quite different from either standard gas or steam turbine designs.

The limited enthalpic content of many energy sources enforces the use of organic working media, with unusual properties for the turbine. A versatile cycle design and optimization requires the parameterization of the prime turbine design. In order to address the major challenges involved in this process, the present study discusses the preliminary design of an electricity-producing turbine, in the range of 100 kWel, for a low enthalpy organic Rankine cycle. There are many potential applications of this power generating turbine including geothermal and solar thermal fields or waste heat of PEM type fuel cells.

An integrated model of equations has been developed, accordingly. The model aims to assess the performance of an organic cycle for various working fluids, including NH3, R600a and R-134a. The most appropriate working fluid has been chosen, taking into consideration its influence on both cycle efficiency and the specific volume ratio. The influence of this choice is of particular importance at turbine extreme operating conditions, which are strongly related to the turbine size. In order to assess the influence of various design parameters, a turbine design tool has been developed and applied to preliminarily define the blading geometry.

Finally, a couple of competitive turbine designs have been developed. In one approach, the turbine speed is restricted to subsonic domain, while in the other approach the turbine speed is transonic, resulting to choked flow at the turbine throat. The two approaches have been evaluated in terms of turbine compactness and machine modularity. Results show that keeping the crucial parameters of the geometrical formation of the blade constant, turbine size could become significantly smaller decreasing up to 90% compared its original value.
An Investigation of Conjugate Heat Transfer Simulations Based on Discontinuous Galerkin Methods on Unstructured Grids
Authors: Hao Zengrong , Ren Xiaodong , Song Yin , Gu Chunwei
Published: November 2013

A framework for the simulations of conjugate heat transfer (CHT) problems using discontinuous Galerkin (DG) methods on unstructured grids is presented. The compressible fluid dynamic equations and solid heat conduction equations are discretized into the explicit DG formulations simultaneously. The Bassi-Rebay method is used in the gradients computation inside both fluid and solid domains. Fully coupled strategy based on the data exchange process via the numerical flux of interface quadrature points is devised. Various turbulence models and the local-variable-based transition model γ -Reθ are assimilated into the unified algorithm framework. The feasibility of the methodology is validated by some test cases. The work can be viewed as a primary attempt towards further investigations of DG and other high-accuracy methods applications in the engineering CHT problems.
Enhanced Film Cooling Effectiveness With Surface Trenches
Authors: Vighneswara Rao K. , Liu Jong S. , Crites Daniel C. , Tapia Luis A. , Malak Malak F. , Sujatha G. , Balamurugan S.
Published: November 2013

In this study, cylindrical and fan shaped film cooling holes are evaluated on the blade surface numerically, using the Computational Fluid Dynamics (CFD) tool ANSYS-CFX, with the objective of improving cooling effectiveness by understanding the flow pattern at the cooling hole exit. The coolant flow rates are adjusted for blowing ratios of 0.5, 1.0 & 1.5 (momentum flux ratios of 0.125, 0.5 & 1.125 respectively). The density ratio is maintained at 2.0. New shaped holes viz. straight, concave and convex trench holes are introduced and are evaluated under similar operating conditions. Results are presented in terms of surface temperatures and adiabatic effectiveness at three different blowing ratios for the different film cooling hole shapes analyzed. Comparison is made with reference to the fan shaped film cooling hole to bring out relative merits of different shapes. The new trench holes improved the film cooling effectiveness by allowing more residence time for coolant to spread laterally while directing smoothly onto the airfoil surface. While convex trench improved the centre-line effectiveness, straight trench improved the laterally-averaged and overall effectiveness at all blowing ratios. Concave trench improved the effectiveness at blowing ratios 0.5 and 1.0.
Numerical Investigations of Wake and Shock Wave Effects on Film Cooling Performance in a Transonic Turbine Stage: Part 2 — Unsteadiness Effect in a 2D Rotating Passage
Authors: Xu Huazhao , Wang Jianhua , Wang Ting
Published: November 2013

Using the validated CFD model and realizable k-ε turbulence model from Part 1, the unsteadiness effects of shock waves and wake flow on the pressure coefficient and film cooling performance in a 2-D, rotating passage is studied in Part 2. Both time-dependent and time-averaged cooling effectiveness distributions on the rotor under the influence of shock waves and unsteady wake flows are presented with blowing ratios of 0.5, 1.0, and 1.5. The results show that (a) the unsteady wake passing caused by the blade rotation significantly influences the time-dependent pressure coefficients, especially in the forward region downstream of the stagnation point on both the suction and pressure sides on the rotor. This effect can be evidenced by the “wrapping behavior” of a strong vorticity field wrapping around the blade leading edge after the wake hit the blade (b) On the suction side, over the crown area of the rotor, the wake-induced pressure fluctuations are augmented by the weak shock wave emanating from the stator’s trailing edge, appearing as a primary peak followed by a secondary peak. The weak oblique shock wave can be evidenced by the dense Mach contour curves. The effect of the wake (rotational) is distinguished from that of the shock (inviscid and non-rotational) by comparing the pressure gradient field with the vorticity field. (c) Similar effects of passing wakes and shock waves on the surface pressure on a rotor are observed on the film cooling effectiveness, except that these effects are of the same magnitude. (d) The effect of the blowing ratio on the static pressure distribution at the rotor wall is not significant, whereas its effect on the film cooling effectiveness is more pronounced.
Numerical and Experimental Study of Ethanol Combustion in an Industrial Gas Turbine
Authors: Sallevelt Joost L. H. P. , Pozarlik Artur K. , Brem Gerrit , Beran Martin , Axelsson Lars-Uno
Published: November 2013

The application of ethanol as a biomass-derived fuel in OPRA’s 2 MWe class OP16 radial gas turbine has been studied both numerically and experimentally. The main purpose of this work is to validate the numerical model for future work on biofuel combustion.

For the experimental investigation a modified OP16 gas turbine combustor has been used. This reverse-flow tubular combustor is a diffusion type combustor that has been adjusted to be suitable for numerical validation. Two series of ethanol burning experiments have been conducted at atmospheric pressure with a thermal input ranging from 16 to 72 kW. Exhaust gas temperature and emissions (CO, CO2, O2, NOx) were measured at various fuel flow rates while keeping the air flow rate and air temperature constant. In addition, the temperature profile of the combustor liner has been determined by applying thermochromic paint.

CFD simulations have been performed in Ansys Fluent for four different operating conditions considered in the experiments. The simulations are based on a 3D RANS code. Fuel droplets representing the fuel spray are tracked throughout the domain while they interact with the gas phase. A temperature profile based on measurements has been prescribed on the liner to account for heat transfer through the flame tube wall. Detailed combustion chemistry is included by using the steady laminar flamelet model.

The predicted levels of CO2 and O2 in the exhaust gas are in good agreement with the experimental results. The calculated and measured exhaust gas temperatures show a close match for the low power condition, but more significant deviations are observed in the higher load cases. Also, the comparison pointed out that the CFD model needs to be improved regarding the prediction of the pollutants CO and NOx.

Chemiluminescence of CH radicals in the flame front indicated that the flame extends up to the liner, suggesting the presence of fuel near the surface. However, this result was not confirmed by liner temperature measurements using thermochromic paint.
Experimental Study on a Double-Swirled Non-Premixed Humid Air/Syngas Burner
Authors: Ge Bing , Zang Shu-sheng , Tian Yinsheng , Zhang Dong-fang , Cui Yao-xin , Xie Yue-sheng
Published: November 2013

The development of integrated gasification combined cycle (IGCC) systems provides cost-effective and environmentally sound options for meeting future coal-utilizing power generation needs in the world. The combustion of gasified coal fuel significantly influences overall performance of IGCC power generation. Experimental measurements are carried out on a non-premixed model combustor, equipped with a double-swirled syngas burner. Planar laser-induced fluorescence (PLIF) of OH radical measurement is adopted to identify main reaction zones and burnt gas regions as well. Together with the temperature and emission measurements during the exhaust section, some important characteristics of the syngas flame are investigated overall. In this paper, the effects of the CO/H2 molar ratio consisting of syngas fuel are investigated under different humidity. With the increase of CO/H2 ratios, the concentration field of OH radicals is gradually away from the nozzle exit, and the nozzle exit almost no existence of OH radicals, forming a typical lifted flame. In addition, fluorescent signal strength of OH radicals pronounced weakening, the flame gradually appeared W type distribution and more and more obvious with the increased of humidification amount. At the same time the average exhaust temperature of combustor CO and NOx missions almost no change. The study can provide a reliable database for high moisture gas turbine combustor design and combustion numerical simulation.
Investigation of Factors That Contribute to Deposition Formation on Turbine Components in a High-Pressure Combustion Facility
Authors: Murphy Robert G. , Nix Andrew C. , Lawson Seth A. , Straub Douglas , Beer Stephen K.
Published: November 2013

Researchers at West Virginia University worked with the U.S. Department of Energy, National Energy Technology Laboratory (NETL) to study particulate deposition in a high-pressure and high-temperature environment. To simulate deposition of particulate from combustion of coal synthesis gas on the pressure side of an Integrated Gasification Combined Cycle (IGCC) turbine first stage vane, angled film-cooled thermal barrier coated (TBC) test articles scaled to turbine flow conditions using Reynolds similarity were subjected to accelerated deposition at a pressure of approximately 4 bar and a gas temperature ranging from 1373–1560K. The effects on deposition rates of five different factors were examined; free stream temperature, impaction angle, blowing ratio, particulate loading, and TBC vs. non-TBC coated surface. As the freestream temperature increased the results showed that the deposition also increased. The amount of deposition increased as the impaction angle increased from 10° to 20°. The effect of blowing ratio (M, mass flux ratio) was examined at M = 0.0, 0.25 and 1.0. As the blowing ratio increased the amount of deposition decreased. The particulate loading was varied from 100 ppmw to 200 ppmw. The amount of deposition increased with the higher particulate loading case; however, coverage on the test article face did not increase significantly. Finally, a comparison test was performed between a TBC coated test article and a bare metal test article. This test showed that more deposition formed on the TBC coated article than the bare metal article. During testing, the deposition that formed on the TBC coated test articles demonstrated a resistance to adhering to the surface once the mainstream temperature was reduced during facility shut down. The results of this work will aid gas turbine manufacturers to better understand and develop mitigations for the five factors studied that cause deposit formations in IGCC engines. This work will also give insight to researchers studying deposition on the methods developed and issues encountered in simulating particulate matter into a high-pressure combustion facility.
Influence of Purge Flow Injection Angle on the Aero-Thermal Performance of a Rotor Blade Cascade
Authors: Barigozzi G. , Franchini G. , Perdichizzi A. , Maritano M. , Abram R.
Published: November 2013

This paper is focused on the influence of stator-rotor purge flow injection angle on the aerodynamic and thermal performance of a rotor blade cascade. Tests were performed in a seven-blade cascade of a high-pressure gas turbine rotor at low Mach number (Ma2is = 0.3) under different blowing conditions. A number of fins were installed inside the upstream slot to simulate the effect of rotation on the seal flow exiting the gap in a linear cascade environment. The resulting coolant flow is ejected with the correct angle in the tangential direction. Purge flow injection angle and blowing conditions were changed in order to identify the best configuration in terms of end wall thermal protection and secondary flows reduction. The 3D flow field was surveyed by traversing a 5-hole miniaturized pressure probe in a downstream plane. Secondary flow velocities, loss coefficient and vorticity distributions are presented for the most significant test conditions. Film cooling effectiveness distributions on the platform were obtained by Thermochromic Liquid Crystals technique. Results show that purge flow injection angle has an impact on secondary flows development and thus on the end wall thermal protection, especially at high injection rates. Passage vortex is enhanced by a negative injection angle, which simulates the real counter rotating purge flow direction.
Evaluation of RANS Predictions on a Linear Nozzle Vane Cascade With Trailing Edge Cutback Film Cooling
Authors: Ravelli S. , Barigozzi G.
Published: November 2013

The present study concentrates on the numerical investigation of a cooled trailing edge in a linear nozzle vane cascade typical of a high-pressure turbine. The trailing edge cooling features a pressure side cutback with film cooling slots, stiffened by evenly spaced ribs in an inline configuration. Cooling air is also ejected through two rows of cooling holes placed on the pressure side, upstream of the cutback. The main goal is to evaluate the reliability of RANS predictions in such a complex cooling system. Different coolant-to-mainstream mass flow ratio values up to MFR = 2.8% were simulated at exit Mach number of M2is = 0.2. The computed performance of the trailing edge cooling scheme was compared to available measurements of: holes and cutback exit velocity and discharge behavior; boundary layer along traverses located on the pressure side, downstream of each row of cooling holes and approaching the trailing edge; adiabatic film cooling effectiveness. Special emphasis was dedicated to coolant-mainstream interaction and film cooling effectiveness over the pressure surface of the vane. Despite the steady approach, the simulations provided a reliable overview of coolant and mainstream aerodynamic features. The limitations in predicting the measured drop in cooling effectiveness toward the trailing edge were highlighted as well.
Flow Characteristics of Axial Compressor Tandem Cascades at Large Off-Design Incidence Angles
Authors: Schneider Tim , Kožulović Dragan
Published: November 2013

In a number of recent and former publications, compressor tandem blade configurations show potential to outperform single blade configurations in terms of turning, loss and operating range at high aerodynamic loading levels. However, very little insight is given into the mechanisms of flow breakdown when comparing tandem blades to single blades at large off-design incidence angles.

Single blade cascades tend to fail as a result of either pressure side flow separation for high negative incidence or suction side flow separation for high positive incidence, the latter being mostly accompanied by significant increase of underturning. Tandem blade cascades are expected to show a different behavior due to the aerodynamic interaction in the blade overlapping region.

Two different tandem blade configurations are examined together with their respective reference single blades, one being a recently designed and optimized tandem blade for high subsonic inlet Mach numbers, which has also been investigated in cascade wind tunnel testing. The other one is a more generic tandem blade based on NACA65 family, designed for medium inlet Mach numbers using current state-of-the-art understanding of tandem design.

The mechanisms of flow breakdown are examined using quasi two-dimensional RANS simulations which are validated with test data for one of the aforementioned tandem configurations. A detailed analysis of the flow structure at heavy off-design conditions gives insight into the characteristics of tandem flow breakdown. In particular, the ability of the tandem configuration to extend the operating range to larger positive incidence is described. The shortcomings of the tandem cascade at large negative incidence are also commented. These and further conclusions can be used to improve tandem blade performance at moderate off-design conditions.
Further Investigations of Unsteady Forces on a Steam Turbine Stage
Authors: Patel Kush , Chen Tie , Millington Peter
Published: November 2013

Previous work has shown combined effects of blade count ratio (BCR) and gap ratios (GR) have produced profound unsteady flow behaviour on an Impulse stage. As a continuation of this work, investigations are extended into a Reaction stage and an additional Impulse stage using a different stator profile. On the original Impulse stage, sensitivity of key design parameters are investigated, such as radial position, rotational speed, solidity and stagger angle. Furthermore, the effects on the stimulus from both upstream and downstream stationary rotors are investigated. Results have shown that stimulus is strongly related to rotational speed, profile, stagger angle and solidity. Stimulus due to downstream stator is much lower than that due to upstream stator. A resonance is observed at BCR = ∼0.7 for both Impulse stages which is caused by the aft-loading feature, but not for Reaction stage. A low stimulus is observed for the Reaction stage, which generally reduces with BCR.
The Concept of Adiabatic Heat Transfer Coefficient and its Application to Turbomachinery
Authors: Gomes Reinaldo A. , Niehuis Reinhard
Published: November 2013

Typical turbomachinery flows are too complex to be predicted by analytical solutions alone. Therefore numerous correlations and test data are used in conjunction with numerical tools in order to design thermally critical components. This approach can be problematic because these correlations and data are not fully independent of the boundary conditions applied. The heat transfer coefficients obtained are not only dependent on the aerodynamics of the flow but also on the thermal boundary layer created along the surface. The adiabatic heat transfer coefficient is the only one which is independent of the thermal boundary conditions, as long as the energy equation can be considered linear with respect to the temperature. However, a proper prediction of the surface temperature cannot be obtained with the adiabatic heat transfer coefficient alone.

This paper first reviews the concept of adiabatic heat transfer coefficient and its application to turbomachinery flows. Later, a concept is introduced to allow interchanging between different definitions of heat transfer coefficient and boundary conditions, i.e. constant heat flux or constant wall temperature. Finally, a typical configuration for measuring the adiabatic heat transfer coefficient on a turbine blade and the conversion to other definitions of heat transfer coefficient is presented and evaluated. It is shown that with the technique presented here even small deficiencies of some experiments can be compensated for.