bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of a SOFC/MGT Hybrid Power Plant Test Rig: Impact and Characterization of Coupling Elements
Authors: Hohloch Martina , Huber Andreas , Aigner Manfred
Published: September 2014

The main topic of the paper is the discussion of the operational behavior of the solid oxide fuel cell (SOFC)/micro gas turbine (MGT) hybrid power plant test rig with the pressure vessels of the SOFC emulator. In the first part a brief introduction to the test rig and its components is given. In the arrangement of the test rig the MGT is connected via an interface to the tubing system. Here, the preheated air after the recuperator can be led either to the emulator or via a bypass tube directly to the MGT. Furthermore, there is a direct connection between the compressor outlet and emulator for the startup and shutdown procedure. The facility is equipped with detailed instrumentation, including mass flow meters, thermocouples and pressure probes. In the second part of the paper the characterization of the hybrid power plant test rig is shown. To analyze the thermodynamic and fluid dynamic impact of the coupling elements various studies were carried out. Hereby, the influence of the coupling elements on the operational behavior, system stability and system performance of the micro gas turbine is shown for stationary load points, as well as during transient maneuvers like startup, load-change and shutdown. To avoid critical operating conditions limitations were defined and emergency maneuvers were developed and tested. Out of these investigations an operating concept for the hybrid power plant test rig can be derived.
Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates
Authors: Louw Francois G. , von Backström Theodor W. , van der Spuy Sybrand J.
Published: September 2014

Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-ε turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.
Development of a New Design Method for High Efficiency Swept Low Pressure Axial Fans With Small Hub/Tip Ratio
Authors: Lindemann Thore Bastian , Friedrichs Jens , Stark Udo
Published: September 2014

For a competitive low pressure axial fan design low noise emission is as important as high efficiency. In this paper a new design method for low pressure fans with a small hub to tip ratio including blade sweep is introduced and discussed based on experimental investigations. Basis is an empirical axial and tangential velocity distribution at the rotor outlet combined with a distinctive sweep angle distribution along the stacking line. Several fans were designed, built and tested in order to analyze the aerodynamic as well as the aeroacoustic behavior.

For the aerodynamic performance particular attention was paid to compensate the influence of reduced pressure rise and efficiency due to increasing blade sweep. This was achieved by a method of increasing the blade chord depending on the local sweep angle which is based on single airfoil data. The tested fans without this compensation revealed a significant noise reduction effect of up to approx. 6 dB(A) for a tip sweep angle of 64° which was accompanied by an unsatisfactory effect of reduced overall aerodynamic performance.

The second group of fans did not only confirm the method of the aerodynamic compensation by a nearly unchanged pressure rise and efficiency characteristic but also revealed an increased aeroacoustic benefit of in average 9.5 dB(A) compared to the unswept version. Beside the overall characteristics the individual differences between the designs are also discussed using results of wall pressure measurements which show some significant changes of the blade tip flow structure.
Upgrading the Undergraduate Gas Turbine Lab
Authors: Lee Zachary , Lowe Shane , Van Poppel Bret P. , Benson Michael J. , St. Leger Aaron
Published: September 2014

A study of gas turbine engines is an important component of an integrated thermodynamics and fluid mechanics two-course sequence at the United States Military Academy (USMA). Owing to the ubiquity of gas turbines in military use, graduating cadets will encounter a variety of these engines throughout their military careers. Especially for this unique population, it is important for engineering students to be familiar with the operation and applications of gas turbines. Experimental analysis of a functional auxiliary power unit (APU) from an Army utility helicopter has been a key component of this block of instruction for several decades. As with all laboratory equipment, the APU has experienced intermittent maintenance issues, which occasionally render it unusable for the gas turbine laboratory in the course. Because of this, a very basic virtual laboratory was implemented which integrated video of the physical laboratory with key parameters and behind-the-screen data collection for use in engine analysis.

A revitalized version of both the physical and virtual gas turbine laboratory experiences offered in the thermal-fluids course will include substantial improvements over the existing setup. The physical laboratory, which is centered on a refurbished APU from a medium-sized commercial aircraft, will continue to incorporate measurements of temperature and pressure throughout the combustion process, as well as fuel flow rate. In an improvement over the original laboratory setup, an orifice plate will be used to measure the flow rate of bleed air exiting the turbine, which had not previously been open during engine testing. Additionally, the air flow through the anti-surge valve was not metered in the original version of the physical laboratory. However, the anti-surge air flow can account for nearly 25% of the total air flow, and performance calculations in the physical laboratory will now account for this loss. The turbine output shaft will run a water-brake dynamometer. All instrumentation will be converted to digital signals and projected on a large screen outside the test area through a LabVIEW front panel. The virtual laboratory will include the same metering options as the operational APU. In addition, the virtual laboratory will include the option to alter engine operating parameters, such as inlet temperature and pressure or exhaust temperatures, and students may conduct broad parameter sweeps across ranges of possible inputs or desired outputs. These improvements will enable students to gain a deeper understanding of gas turbine operation and capabilities in practical applications. The improved laboratory will be implemented in Spring, 2014.
Three Dimensional Flow Field in a Highly Loaded Compressor Cascade
Authors: Beselt Christian , Eck Mario , Peitsch Dieter
Published: September 2014

Within the present paper a detailed experimental investigation is presented. The influence of blade loading on the development and interaction of secondary flow structures within an annular compressor stator cascade is examined. Experimental results at 3% chord hub clearance were obtained at four different blade loadings. Included are blade and endwall flow visualization, time resolved measurements of the static pressure on the endwall and radial-circumferential hot-wire traverse measurements within the passage as well as five-hole probe traverse measurements at the inlet and the outlet of the passage. The experimentally obtained results give detailed insight on the effect of the incidence on the development and interaction of the clearance vortex, horse-shoe vortex and the passage vortex. Furthermore it will be shown that a vortex breakdown of the clearance vortex occurs at higher loadings.
Evaluation of Superposition Predictions for Showerhead Film Cooling on a Vane
Authors: Anderson Joshua B. , Winka James R. , Bogard David G. , Crawford Michael E.
Published: September 2014

The leading edge of a turbine vane is subject to some of the highest temperature loading within an engine, and an accurate understanding of leading edge film coolant behavior is essential for modern engine design. Although there have been many investigations of the adiabatic effectiveness for showerhead film cooling of a vane leading edge region, there have been no previous studies in which individual rows of the showerhead were tested with the explicit intent of validating superposition models. For the current investigation, a series of adiabatic effectiveness experiments were performed with a five-row and three-row showerhead. The experiments were repeated separately with each individual row of holes active. This allowed evaluation of superposition methods on both the suction side of the vane, which was moderately convex, and the pressure side of the vane, which was mildly concave. Superposition was found to accurately predict performance on the suction side of the vane at lower momentum flux ratios, but not at higher momentum flux ratios. On the pressure side of the vane the superposition predictions were consistently lower than measured values, with significant errors occurring at the higher momentum flux ratios. Reasons for the under-prediction by superposition analysis are presented.
Film Cooling From Novel Sister Shaped Single-Holes
Authors: Khajehhasani Siavash , Jubran Bassam
Published: September 2014

A numerical investigation of the film cooling performance from novel sister shaped single-holes (SSSH) is presented in this paper and the obtained results are compared with a single cylindrical hole, a forward diffused shaped hole, as well as discrete sister holes. Three types of the novel sister shaped single-hole schemes namely downstream, upstream and up/downstream SSSH, are designed based on merging the discrete sister holes to the primary hole in order to reduce the jet lift-off effect and increase the lateral spreading of the coolant on the blade surface as well as a reduction in the amount of coolant in comparison with discrete sister holes. The simulations are performed using three-dimensional Reynolds-Averaged Navier Stokes analysis with the realizable k–ε model combined with the standard wall function. The upstream SSSH demonstrates similar film cooling performance to that of the forward diffused shaped hole for the low blowing ratio of 0.5. While it performs more efficiently at M = 1, where the centerline and laterally averaged effectiveness results improved by 70% and 17%, respectively. On the other hand, the downstream and up/downstream SSSH schemes show a considerable improvement in film cooling performance in terms of obtaining higher film cooling effectiveness and less jet lift-off effect as compared with the single cylindrical and forward diffused shaped holes for both blowing ratios of M = 0.5 and 1. For example, the laterally averaged effectiveness for the downstream SSSH configuration shows an improvement of approximately 57% and 110% on average as compared to the forward diffused shaped hole for blowing ratios of 0.5 and 1, respectively.
Quantification of Foreign Object Damage (FOD) and Electrical Resistivity for CMCs and Tensile Residual Strength Prediction
Authors: Abdi Frank , Xue Yibin , Morscher Gregory N. , Choi Sung
Published: September 2014

SiC-based ceramic matrix composites (CMC) in turbine engine applications must sustain certain foreign object impacts that might occur in services. Experiments and nondestructive evaluation (NDE) have illustrated good correlations between impact energy and foreign object damage (FOD) assessed using electrical resistivity (ER), acoustic emission (AE), and microscopy. In this paper, a progressive failure dynamic analysis (PFDA) method is explored in understanding and predicting the damage states, electrical resistivity, and residual strength after impact of CMCs. In general, CMCs are modeled using effective fiber, matrix, and interface constitutive behaviors, from which the lamina stiffness and strengths can be derived. Similarly, the electrical resistivity of a lamina is homogenized based on the percolation theory for inclusion/discontinuities dispersion in a matrix for voids and Si particles, as well as fibers, and damages after impact. To accurately correlate the damage state with ER, the PFA tool has been improved to incorporate the physical damage mechanisms in CMCs, which are matrix microcrack density due to both longitudinal and transverse tensile loads and the fiber breakage due to probabilistic fiber strength distribution. The predicted damage states and ER are correlated with the measurement of FOD and validated with tension after impact tests using high temperature ER. The PFDA tool has demonstrated a great potential for CMCs’ FOD and residual strength predictions.
Coupled Lateral and Torsional Nonlinear Transient Solver With Application to Flexible Rotor-Bearing System
Authors: Cao Jianming , Dimond Tim , Allaire Paul
Published: September 2014

This paper provides a time transient method for solving coupled lateral and torsional analysis of a flexible rotor-bearing system including gyroscopic effects, nonlinear short journal bearings, nonlinear short squeeze film dampers, and external nonlinear forces/torques. The rotor is modeled as linear, and the supporting components, including bearings and dampers, are modeled as nonlinear. An implicit Runge-Kutta method is developed to solve the nonlinear equations of motion with non-constant operating speed since the unbalance force and the gyroscopic effect are related to both the rotational speed and the acceleration. The developed method is compared with previous torsional analysis first to verify the nonlinear transient solver. Then the coupled lateral and torsional analysis of a flexible 3-disk rotor with nonlinear bearings and nonlinear dampers driven by a synchronous motor is approached. The acceleration effects on lateral and torsional amplitudes is presented in the analysis. The developed method can be used to study the rotor motion with non-constant rotational speed, such as during startup, shutdown, going through critical speeds, blade loss force, or other sudden loading.
On the Recessed Blade Tip With and Without a Porous Material in an Axial Compressor
Authors: Jung Young-Jin , Kim Tae-Gon , Choi Minsuk
Published: September 2014

This paper addresses the effect of the recessed blade tip with and without a porous material on the performance of a transonic axial compressor. A commercial flow solver was employed to analyze the performance and the internal flow of the axial compressor with three different tip configurations: reference tip, recessed tip and recessed tip filled with a porous material. It was confirmed that the recessed blade tip is an effective method to increase the stall margin in an axial compressor. It was also found in the present study that the strong vortex formed in the recess cavity on the tip pushed the tip leakage flow backward and weakened the tip leakage flow itself, consequently increasing the stall margin without any penalty of the efficiency in comparison to the reference tip. The recessed blade tip filled with a porous material was suggested with hope to obtain the larger stall margin and the higher efficiency. However, it was found that a porous material in the recess cavity is unfavorable to the performance in both the stall margin and the efficiency. An attempt has been made to explain the effect of the recess cavity with and without a porous material on the flow in an axial compressor.
Thermodynamics Cycle Analysis, Pressure Loss and Heat Transfer Assessment of a Recuperative System for Aero Engines
Authors: Goulas A. , Donnerhack S. , Flouros M. , Misirlis D. , Vlahostergios Z. , Yakinthos K.
Published: September 2014

Aiming in the direction of designing more efficient aero engines, various concepts have been developed in recent years, among which is the concept of an intercooled and recuperative aero engine. Particularly in the area of recuperation, MTU Aero Engines has been driving research activities in the last decade. This concept is based on the use of a system of heat exchangers mounted inside the hot-gas exhaust nozzle (recuperator). Through the operation of the system of heat exchangers, the heat from the exhaust gas, downstream the LP turbine of the jet engine is driven back to the combustion chamber. Thus, the preheated air enters the engine combustion chamber with increased enthalpy, providing improved combustion and by consequence, increased fuel economy and low-level emissions. If additionally an intercooler is placed between the compressor stages of the aero engine, the compressed air is then cooled by the intercooler thus, less compression work is required to reach the compressor target pressure.

In this paper an overall assessment of the system is presented with particular focus on the recuperative system and the heat exchangers mounted into the aero engine’s exhaust nozzle. The herein presented results were based on the combined use of CFD computations, experimental measurements and thermodynamic cycle analysis. They focus on the effects of total pressure losses and heat exchanger efficiency on the aero engine performance especially the engine’s overall efficiency and the specific fuel consumption. More specifically, two different hot-gas exhaust nozzle configurations incorporating modifications in the system of heat exchangers are examined. The results show that significant improvements can be achieved in overall efficiency and specific fuel consumption hence contributing into the reduction of CO2 and NOx emissions.

The design of a more sophisticated recuperation system can lead to further improvements in the aero engine efficiency in the reduction of fuel consumption.

This work is part of the European funded research program LEMCOTEC (Low Emissions Core engine Technologies).
An Accelerated Medial Object Transformation for Whole Engine Optimisation
Authors: Wang Leran , Toal David J. J. , Keane Andy J. , Stanley Felix
Published: September 2014

The following paper proposes an accelerated medial object transformation for the tip clearance optimisation of whole engine assemblies. A considerable reduction in medial object generation time has been achieved through two different mechanisms. Faces leading to unnecessary branches in the medial mesh are removed from the model and parallelisation of the medial object generation is improved through the subdivision of the original 3D CAD model. The time savings offered by these schemes are presented with respect to the generation of the medial objects of two complex gas turbine engine components. It is also demonstrated that the utilization of these techniques within a design optimisation may result in a considerable reduction in wall time.
Intermittency in the Dynamics of Turbulent Combustors
Authors: Nair Vineeth , Sujith R. I.
Published: September 2014

The dynamic transitions preceding combustion instability and lean blowout were investigated experimentally in a laboratory scale turbulent combustor by systematically varying the flow Reynolds number. We observe that the onset of combustion-driven oscillations is always presaged by intermittent bursts of high-amplitude periodic oscillations that appear in a near random fashion amidst regions of aperiodic, low-amplitude fluctuations. The onset of high-amplitude, combustion-driven oscillations in turbulent combustors thus corresponds to a transition in dynamics from chaos to limit cycle oscillations through a state characterized as intermittency in dynamical systems theory. These excursions to periodic oscillations become last longer in time as operating conditions approach instability and finally the system transitions completely into periodic oscillations. Such intermittent oscillations emerge through the establishment of homoclinic orbits in the phase space of the global system which is composed of hydrodynamic and acoustic subsystems that operate over different time scales. Such intermittent burst oscillations are also observed in the combustor on increasing the Reynolds number further past conditions of combustion instability towards the lean blowout limit. High-speed flame images reveal that the intermittent states observed prior to lean blowout correspond to aperiodic detachment of the flame from the bluff-body lip. These intermittent oscillations are thus of prognostic value and can be utilized to provide early warning signals to combustion instability as well as lean blowout.
Engine Testing Using Highly Reactive Fuels on Siemens Industrial Gas Turbines
Authors: Bonaldo Alessio , Andersson Mats , Larsson Anders
Published: September 2014

Siemens Industrial Turbomachinery AB (SIT) Finspong is increasingly asked by customers to consider if a wider range of gas compositions may be operated in its gas turbines. A large part of these fuel compositions contain high concentrations of highly reactive components like hydrogen and ethane. Such fuel compositions are characterized by higher flame speeds than the standard natural gas which introduce increased risk for flashback and premature combustor and/or fuel nozzle distress.

The SIT approach for fuel flexibility testing, Experimental Burner In Test engine (EBIT) uses a separate feed for testing a selected fuel composition in one burner in a standard gas turbine installation where the other burners use fuel from the standard fuel system. The separate feed is operated as a slave to engine governor heat demand, but can also be controlled independently.

This paper describes how EBIT was used to test the capability of the SIT 3rd generation DLE burner to satisfactorily operate using highly reactive fuel components such as ethane and hydrogen. Combustion monitoring techniques and measurements to check flame behavior and assess flashback potentials of the tested fuel compositions are described. Results from testing show that the SIT 3rd generation DLE burner allows extending the levels of reactive fuel components accepted for operation on the SGT-700 33MW engine and SGT-800 50MW engine.
Film Cooling Jet Injection Effect in Heat Transfer Coefficient Augmentation for the Pressure Side Cooling of Turbine Vane
Authors: Najafabadi Hossein Nadali , Karlsson Matts , Kinell Mats , Utriainen Esa
Published: September 2014

Improving film cooling performance of turbine vanes and blades is often achieved through application of multiple arrays of cooling holes on the suction side, the showerhead region and the pressure side. This study investigates the pressure side cooling under the influence of single and multiple rows of cooling in the presence of a showerhead from a heat transfer coefficient augmentation perspective. Experiments are conducted on a prototype turbine vane working at engine representative conditions. Transient IR thermography is used to measure time-resolved surface temperature and the semi-infinite method is utilized to calculate the heat transfer coefficient on a low conductive material. Investigations are performed for cylindrical and fan-shaped holes covering blowing ratio 0.6 and 1.8 at density ratio of about unity. The freestream turbulence is approximately 5% close to the leading edge.

The resulting heat transfer coefficient enhancement, the ratio of HTC with to that without film cooling, from different case scenarios have been compared to showerhead cooling only. Findings of the study highlight the importance of showerhead cooling to be used with additional row of cooling on the pressure side in order to reduce heat transfer coefficient enhancement. In addition, it is shown that extra rows of cooling will not significantly influence heat transfer augmentation, regardless of the cooling hole shape.
Materials Corrosion Concerns for Supercritical Carbon Dioxide Heat Exchangers
Authors: Kruizenga Alan , Fleming Darryn
Published: September 2014

Supercritical Carbon Dioxide (S-CO2) is an efficient and flexible working fluid for power production. Research to interface S-CO2 systems with nuclear, thermal solar, and fossil energy sources are currently underway. To proceed, we must address concerns regarding high temperature compatibility of materials and compatibility between significantly different heat transfer fluids.

Dry, pure S-CO2 is thought to be relatively inert [1], while ppm levels of water and oxygen result in formation of a protective chromia layer and iron oxide [2]. Thin oxides are favorable as diffusion barriers, and for their minimal impact on heat transfer. Chromia, however, is soluble in molten salt systems (nitrate, chloride, and fluoride based salts) [3–8]. Fluoride anion based systems required the development of the alloy INOR-8 (Hastelloy N, base nickel, 17%Mo) [9] to ensure that chromium diffusion is minimized, thereby maximizing the life of containment vessels.

This paper reviews the thermodynamic and kinetic considerations for promising, industrially available materials for both salt and S-CO2 systems.
Enhanced CFD Modelling and LDA Measurements for the Air-Flow in an Aero-Engine Front Bearing Chamber: Part II
Authors: Aidarinis J. , Goulas A.
Published: September 2014

A detailed computational study of the air-flow through the outer gap of the front bearing of an aero-engine is presented. The reason to carry out this study was to understand the flow through the bearing as a function of the operational parameters of the engine, which was necessary for the modeling of the flow in the whole bearing chamber. The complex geometry and the size of the bearing gap relative to the overall dimensions of the bearing chamber and the need for very precise and detailed information of the effect on the flow within the chamber of the bearing operational parameters, prohibited the solution of the flow through the gap together with the rest of the bearing chamber. A 3-D modeling of the flow through the outer bearing gap, which included a section of the ball bearing, was performed. Functions relating the pressure drop of the air coming through the bearing gap and the tangential component of velocity of the air exiting the bearing region, to the mass of air through the gap of the ball bearing and the rotational speed of the shaft were developed. The effect of the lubrication oil within the bearing was modeled as an anisotropic porous medium with a predefined law. In order to acquire in a mathematical form the above relationships a series of computational runs were performed. These relationships, in the form of second order curves, were subsequently introduced to the model of the bearing chamber as described in [1]. The constants of the relationships were derived through comparisons of the calculations with the experimental data. From the analysis it was concluded that the pressure drop across the bearing increases with the square of the rotational speed of the shaft with the mass flow of air through the ball bearing as a parameter and vice versa. For this particular ball bearing there is a region where, for any combination of rotational speed of the shaft and pressure drop through the bearing, there is no flow of air through the bearing.

In this paper the detailed modeling methodology, the computational flow field, the boundary conditions and finally the results are presented and discussed.
Numerical Investigations of History Temperature Field and Stress Field of Main Steam Valve
Authors: Xu Sihua , Hu Zhiqiang , He Jin , Xiao Lei , Jiang Puning
Published: September 2014

The flexible start up stop, quick start have been considered as essential functional requirements in the development of new steam turbines. To develop a steam turbine with 566 °C live steam temperature, not only the flexible start up and stop, quick start function, but also the reasonable working life of units influenced by the transient thermal stress are going to be considered. The design of above factors faces challenge. On the other hand, benefited from improved computing technique and ability, it is possible to calculate history temperature field and thermal stress more accurate for each project-specific component.

In this paper, certain supercritical unit inlet valve will be investigated. The valve has been operated for more than 6 years in certain power plant. Thermocouples are equipped in both stop valve chamber and control valve chamber at 100% wall depth to obtain actual operation data. According to the characteristics of different heat transfer stages, numerical analysis is performed to obtain accurate history temperature field and stress field using varied boundary conditions from the cold start at room temperature until the unit at full load.
On Meshing Guidelines for Large Eddy Simulations of Gas Turbine Combustors
Authors: Agarwal Krishna Kant , Konakalla Srinivasa Rao , Selvan Senthamil
Published: September 2014

Large Eddy Simulations (LES) is increasingly becoming a feasible tool for industrial design purposes on account of ongoing advancements in computational power. It is a promising arena in the field of computational fluid dynamics where more details of flow-turbulence are explicitly captured and lesser are modeled as compared to the traditional Reynolds-average (RANS) approaches. For the gas turbine combustors particularly, it is a promising tool for better predictions of reactants mixing and hence the combustion, flame shape and temperature profiles. Also, as inherent unsteady nature of the flow is captured, it can predict combustion dynamics due to heat-release (and hence pressure) fluctuations. The main factor for performing a successful and reliable LES is to find an appropriate filter size for different regions of the CFD domain. This filter size is typically same as the CFD mesh size and turbulent scales larger than this are explicitly solved in LES. In industrial gas turbine combustors, due to complex geometry and numerous small cooling flow passages, unnecessary mesh refinement may make the mesh size prohibitive for a time-marching LES simulation. Hence, judicious selection of important flow features and geometry is important. Still not much experience is available on the quantification of LES meshing requirements for practical gas turbine combustors. In this study, two different LES meshing approaches, namely one based on Taylor length scales and other based on theoretical turbulence energy spectrum are compared for various medium scale gas turbine combustors. While the former approach requires a prior RANS simulation and provides a spatial distribution of the grid size, the latter just requires mean flow properties and global length scale at various inlets but produces only a global mesh value. It is found for all combustor designs under study that the two approaches agree well with each other for predicting mesh size requirements for LES where 85–90% of turbulent length scales are captured. This helps towards standardizing LES meshing procedure in industrial scenarios and helps a user to choose meshing option based on the level of details needed and time-resource constraints.
Development of Steam Chest With Valve for Steam Extraction in Cogeneration
Authors: Hao Zhenzhen , Jiang Puning , Ye Xingzhu , Chen Gang , Hu Yifeng , Zhang Junhui
Published: September 2014

Cogeneration has been identified as a key technical solution to improve environment, by reducing the impact of global climate change and reducing local emissions, such as particulates, sulphur and nitrogen oxides. In cogeneration, a certain pressure of steam has to be extracted from steam turbine. A mechanical device shall be used to maintain the pressure of the extracted steam. In this paper a new steam chest with valve used for cogeneration which is installed in the steam flow is introduced. Different amount of steam extractions need different valve openings. In order to obtain these several valve openings in typical operating conditions, CFD-program is used to simulate the flow path in the steam chest. The pressure distribution on the surface of valve disc can be calculated through CFD method, and corresponding steady aerodynamic forces and torques can be calculated by integral. Pulsatile flow will change the forces and moments acting on the valve discs with time constantly. Frequency spectrograms of the aerodynamic forces are obtained by using the fast Fourier transforms and compared to the characteristic frequencies of the valve disc obtained by mode analysis.

For the purpose of validating the accuracy of CFD model, a test with test model scale of 1:5 has been designed. In the test, the pressure distribution on the valve disc surface and the flow field in the steam chest are acquired respectively by the method PSP (Pressure-Sensitive Paint) and PIV (Particle Image Velocimetry). CFD calculations and experimental results have been compared and it is shown that CFD calculations using K-ε turbulence model has satisfactory precision to calculate the pressure distribution, flow field and the torques.
Effect of Tip Clearance Size on the Ram-Rotor Performance
Authors: Han Ji-ang , Zhong Jing-jun , Pan Zhen-sheng , Yang Ling , Guan Jian
Published: September 2014

The ram-rotor presented by Ramgen Power Systems, Inc. is a new kind of compression system based on shock wave compression technology commonly used in supersonic intakes. Compared to conventional axial and centrifugal compressors, it has a simple and compact configuration, and also has advantages of the higher single stage pressure ratio, small volume and light weight. However, its efficiency should be further improved. Based on its inherent advantages, the ram-rotor can be widely used in small aero-engine, medium and small shipping power system, micro gas turbine employed by distributed energy system and power plant in the future. In this paper, the flow field and performance of a ram-rotor with different tip clearance sizes are simulated numerically by adopting the three dimensional Reynolds-averaged Navier-Stokes equations and the Spalart-Allmaras turbulent model at the design condition. The purpose of numerical simulation is to investigate the flow details and performance parameters of the ram-rotor under different tip clearance sizes, including the structure of the shock wave, the size and location of flow separation zone, radial distribution of flow parameters at the outlet of the ram-rotor, the characteristics of tip clearance leakage flow, and so on. It has been found that the performance of the ram-rotor is very sensitive to the tip clearance size. The overall performance parameters of the ram-rotor decrease greatly with the increase of the tip clearance size. So, the selection of suitable tip clearance size is one of the key issues in obtaining a high performance of the ram-rotor in the design process. For the ram-rotor with tip clearance, the reflection structure of the shock wave will be destroyed. The flow loss of tip region will be increased with the increase of the tip clearance size. For the ram-rotor with and without tip clearance, the flow parameters distribution trend along the radial direction at the outlet is different.
Successful Power Limit Increase Testing of SGT5/6-2000E Gas Turbines on the Basis of Si3D Turbine Blading
Authors: Stapper Martin G. , Kliesch Simon I. , Holzapfel David P.
Published: September 2014

One of the most innovative solutions for making SGTx-2000E gas turbines more competitive and more cost-effective is the Si3D upgrade product. The profile of the Si3D turbine blades and vanes is aerodynamically optimized. Based on this new Si3D design optimization, a Power Limit Increase (PLI) upgrade was developed in close cooperation with customers. The Power Limit Increase upgrade is a change of the engines rating which allows operating the engine at a higher maximum electrical power output. The PLI not only shows a much higher power output of up to 16 % but also a significant increase in efficiency at low ambient temperatures — especially for district heating power plants.

In 2011/2012 at a Finnish SGT5-2000E an opportunity arose to carry out an extensive program of measurements for testing and validating how the power limit can be increased in parallel with the blading upgrade (no compressor modification). The essential feature of this campaign was a non-intrusive stress measurement of blade vibration by means of optical probes. The campaign was successfully completed, and the Finnish customer is able to take advantage of optimized winter operation. The main benefit is operation of the engine at base load, especially at very low ambient temperatures with a higher power output and efficiency potential. On the basis of these encouraging results, Siemens prepared a fleet release for a power limit increase of all SGT5-2000E gas turbines with Si3D airfoils in stages 1 to 4 from 173 MW to 186 MW (with compressor mass flow increase) or even up to 196.5 MW.

In addition, a second opportunity arose 2013 to execute the similar test campaign in the USA for the 60 Hz Si3D turbine blading with a compressor mass flow increase. Thereby not only the same test equipment was used, but several additional investigations had to be done prior to the test campaign.

This publication describes details of the technical evaluation and conversions required to perform these tests and accomplish an increase of the power limit of the SGTx-2000E fleet.
Enhancing the Economic Competitiveness of Concentrating Solar Power Plants Through an Innovative Integrated Solar-Combined Cycle With Thermal Energy Storage
Authors: Guédez Rafael , Spelling James , Laumert Björn
Published: September 2014

The present work deals with the thermoeconomic analysis of an innovative combined power cycle consisting of a molten-salt solar tower power plant with storage supported by additional heat provided from the exhaust of a topping gas-turbine unit. A detailed dynamic model has been elaborated using an in house simulation tool that simultaneously encompasses meteorological, demand and price data. A wide range of possible designs are evaluated in order to show the trade-offs between the objectives of achieving sustainable and economically competitive designs. Results show that optimal designs of the novel concept are a promising cost-effective hybrid option that can successfully fulfill both the roles of a gas peaker plant and a baseload solar power plant in a more effective manner. Moreover, designs are also compared against conventional combined cycle gas turbine power plants and it is shown that, under specific peaking operating strategies, the innovative concept can not only perform better from an environmental standpoint but also economically.
Performance Characterization of the Effect of Axial Positioning of Bend Skewed Casing Treatment Retrofitted to a Transonic Axial Flow Compressor
Authors: Alone Dilipkumar B. , Kumar Subramani Satish , Thimmaiah Shobhavathy , Mudipalli Janaki Rami Reddy , Pradeep A. M. , Ramamurthy Srinivasan , Iyengar Venkat S.
Published: September 2014

The performance of an aero-engines to a large extend depends on the performance behavior of axial flow compressors and is restricted by the compressor instabilities like rotating stall and surge. In the present study, attempts have been made to design and develop the bend skewed casing treatment geometries with lower porosities to improve the stable operating range of single stage axial flow compressor. Experimental investigations were undertaken to study the impact of axial position of one of the casing treatment geometry on the single stage transonic axial flow compressor. The transonic compressor used for the current experimental studies has a stage total to total pressure ratio of 1.35, corrected mass flow rate of 22 kg/s at an operating speed of 12930 rpm. The compressor stage steady and unsteady state response for 20%, 40%, 60% and 100% axial chord coverage relative to the rotor tip chord of the bend skewed casing treatment with a porosity of 33% was studied experimentally. The objective was to identify the optimum axial location; which will give maximum improvement in the stall margin with minimal loss of compressor stage efficiency. Through an experimental study it was observed that the axial location of bend skewed casing treatment plays a very crucial role in governing the performance of the transonic compressor. For all the investigated axial coverages, compressor stall margin increases but the optimum performance in terms of stall margin improvement and efficiency gains were observed at 20% and 40% of the rotor chord. This trend shows good agreement with existing published literature. An improvement of 31.7% in the stall margin with an increase in the stage efficiency was obtained at one of the axial coverage. Maximum improvement of 37% in the stall margin above the solid casing was noticed at 60% axial coverage. The stalling characteristics of the compressor stage also changes with the axial positions. In the presence of solid casing the nature of stall was abrupt and stalls cells travels at half the rotor speed. The blade element performance also studied at the rotor exit using pre-calibrated aerodynamic probe.
Experimental Investigation on the Effect of Porosity of Bend Skewed Casing Treatment on a Single Stage Transonic Axial Flow Compressor
Authors: Alone Dilipkumar B. , Kumar Subramani Satish , Thimmaiah Shobhavathy , Mudipalli Janaki Rami Reddy , Pradeep A. M. , Ramamurthy Srinivasan , Iyengar Venkat S.
Published: September 2014

A bend skewed casing treatment was designed, to study the influence of one of its geometrical parameter porosity on the stable performance of single stage transonic axial flow compressor. The compressor was designed for the stage total-to-total pressure ratio of 1.35, corrected mass flow rate of 22 kg/s at corrected design speed of 12930 RPM. Bend skewed casing treatment has an axial inlet segment till 50% of the total length and rear segment that is skewed by 45° in the direction of the rotor tip section stagger. Both the sections were oriented at a skew angle of 45° to the radial plane such that the flow exiting the slot is in counter-clockwise direction to that of the rotor direction. The casing treatment slot width was equal to the maximum thickness of the rotor blades. Three casing treatment configurations were identified for the current experimental investigation. All the treatment geometries considered for the experimental research have lower porosities than reported in the open literatures. The effect of the porosity parameter on the performance of transonic compressor stage was evaluated at two axial coverages of 20% and 40% relative to the rotor tip axial chord. Performance maps were obtained for the solid casing and casing treatment with three different porosities. Comparative studies were carried out and experimental results showed a maximum of 65% improvement in the stable operating range of the compressor for one of the treatment configurations. It was also observed that the stable operating range of the compressor increases with an increase in the casing treatment porosity. All the casing treatment configurations showed that the compressor stall occurs at lower mass flows as compared to the solid casing. Compressor stage peak efficiency shows significant degradations with increase in the porosity as compared to solid casing. Detailed blade element performances were also obtained using calibrated multi-hole aerodynamic probe. Comparative variations of flow parameters like absolute flow angle, Mach number were studied at full flow and near stall conditions for the solid casing and casing treatment configurations. Hot wire measurements show very high fluctuation in the inlet axial velocity in the presence of solid casing as compared to casing treatments. Experimental investigation revealed that the porosity of the casing treatments has strong influence on the transonic compressor stage performance.
High Resolution Heat Transfer Measurements on the Stator Endwall of an Axial Turbine
Authors: Laveau Benoit , Abhari Reza S. , Crawford Michael E. , Lutum Ewald
Published: September 2014

In order to continue increasing the efficiency of gas turbines, an important effort is made on the thermal management of the turbine stage. In particular understanding and accurately estimating the thermal loads in a vane passage is of primary interest to engine designers looking to optimize the cooling requirements and ensure the integrity of the components. This paper focuses on the measurement of endwall heat transfer in a vane passage with a 3D airfoil shape and cylindrical endwalls. It also presents a comparison with predictions performed using an in-house developed RANS solver featuring a specific treatment of the numerical smoothing using a flow adaptive scheme. The measurements have been performed in a steady state axial turbine facility on a novel platform developed for heat transfer measurements and integrated to the nozzle guide vane row of the turbine. A quasi-isothermal boundary condition is used to obtain both the heat transfer coefficient and the adiabatic wall temperature within a single measurement day. The surface temperature is measured using infrared thermography through small view ports. The infrared camera is mounted on a robot-arm with six degrees of freedom to provide high resolution surface temperature and a full coverage of the vane passage. The paper presents results from experiments with two different flow conditions obtained by varying the mass flow through the turbine: measurements at the design point (ReCax = 7,2.105) and at a reduced mass flow rate (ReCax = 5,2.105). The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are derived from measurements at 14 different isothermal temperatures. The experimental data are supplemented with numerical predictions that are deduced from a set of adiabatic and diabatic simulations. In addition, the predicted flow field in the passage is used to highlight the link between the heat transfer patterns measured and the vortical structures present in the passage.
Coupling of Compressible Turbomachinery and Incompressible Combustor Flow Solvers for Aerothermal Applications
Authors: Kannan K. V. , Page G. J.
Published: September 2014

An approach is presented to simulate the flow in turbomachinery and combustor components using their own specialized software interacting with each other through a coupling procedure. This method allows the prediction of interactions between different components of a gas turbine. Two separate flow solvers, one for the turbomachinery, and one for the combustor are used. The flow solvers are executed simultaneously, each computing a section of the flow and constantly exchanging flow information at the interfaces. The effectiveness of the coupling process is studied for the Outlet Guide Vane simulated using the turbomachinery code and the prediffuser simulated using the combustor code with results compared to experiment. Finally, a coupled simulation is presented for a fully annular isothermal combustor rig section containing one injector head.