bluuebunny/crossref_metadata_2025_split huggingface dataset:
Active Flow Control on a Highly Loaded Compressor Stator Cascade With Synthetic Jets
Authors: Qin Yong , Wang Ruoyu , Song Yanping , Chen Fu , Liu Huaping 
Published: September 2016

Numerical investigations on the control effects of synthetic jets are conducted upon a highly loaded compressor stator cascade. The influence of forcing parameters including actuation frequency, jet amplitude and slot location are analyzed in detail with the single-slit synthetic jet. Besides, a new slot arrangement is put forward for the purpose of effectively controlling flow separation.
Simulation results validate the remarkable effectiveness of the single-slit synthetic jet on controlling flow separation. Owing to the coupling effect between the jet and the main flow, the actuation appears to be most efficient under the characteristic frequency of the main flow passing through the airfoil. Additionally, with the increase of jet momentum coefficient, the control effect is enhanced at first and then decreased, depending on the two aspects: the improvements of aerodynamic performance by momentum injection and the additional flow losses caused by the jet. Compared to other actuator configurations, the segment synthetic jet with three sections can more effectively deflect the end-wall cross flow and thus impede the development of corner vortex, which helps to restrain the accumulation of low momentum fluid towards the corner, emphasizing the importance of slot arrangement. Accordingly, under the optimum condition, the total pressure loss coefficient gains a 15.8% reductions and the static pressure rise coefficient is increased by 5.01%.
Loss Mechanisms of Inter-Platform Steps in a 1.5 Stage Axial Flow Turbine
Authors: Kluxen Robert , Behre Stephan , Jeschke Peter , Guendogdu Yavuz 
Published: September 2016

In this paper detailed steady and unsteady numerical investigations of a 1.5 stage axial flow turbine are conducted to determine the specific influence of inter-platform steps in the first stator — as caused by deviations in manufacturing or assembly. A basic first stator design and a design consisting of a bow and endwall contours are compared. Apart from step height, the position and geometry of the inter-platform border are varied for the basic design. To create the steps, every third stator vane was elevated, together with its platforms at hub and shroud — such that the flow capacity is only little affected.
The results show that the effects of steps on the platform borders in front and aft of the first stator can be decoupled from those occurring on the inter-platform steps. For the latter — being the main contributor to the additional loss — the intensity of recirculation zones and losses increase substantially when the platform border is located close to the suction side. Using a relative step height of 1.82 % span, the entropy production doubles when compared to a position close to the pressure side, which can be explained by differences in local flow velocity level. Regarding a circular-arc shape platform, the losses can be more than halved — mainly due to lower included angles between step and endwall flow streamlines.
The findings can be explained by a non-dimensional relation of the local entropy production using local values for step height and characteristic flow quantities. Furthermore, a reduction in step height leads to an attenuation of the otherwise linear relationship between step height and entropy production, which is mainly due to lower local ratio of step height and boundary layer thickness. In the case of laminar or transitional flow regions on the endwall — typical for turbine rigs with low inlet turbulence and low-pressure turbines under cruise conditions — steps lead to immediate local flow transition and thus substantially different results.
A Criterion for the Preliminary Design of High-Efficiency Tube-Axial Fans
Authors: Masi Massimo , Castegnaro Stefano , Lazzaretto Andrea 
Published: September 2016

Tube-axial fans are widely used in industrial applications because of their compactness, simplicity, and low cost. However, the achievable fan pressure rise is generally penalised by the absence of a straightener and diffuser, and the consequent waste of tangential and axial dynamic pressures at the fan outlet. The corresponding fan efficiency drop might not comply with stringent regulations like the European Directive for energy-related products. Thus, operation ranges of high efficiency need to be clearly defined in the preliminary design phase, especially when constraints on maximum size and/or rotational speed are imposed.
This paper proposes analytical formulas and charts to evaluate the efficiency of the tube-axial fan configuration (with or without tail-cone diffuser) when constraints on fan size and/or speed are additional design requirements. The analytical formulas and charts have been validated against experimental data.
On this basis, a preliminary design criterion is suggested for high-efficiency tube-axial fans featuring arbitrary vortex design blades of constant swirl type. The criterion is used to design a 315 mm low-to-medium pressure tube-axial fan that is able to operate at a constant aeraulic efficiency peak of approximately 0.6 for blade positioning angles in the range 20° to 30°.
On Generation of Entropy Waves by a Premixed Flame
Authors: Strobio Chen Lin , Steinbacher Thomas , Silva Camilo , Polifke Wolfgang 
Published: September 2016

It is understood that so-called “entropy waves” can contribute to combustion noise and play a role in thermoacoustic instabilities in combustion chambers. The prevalent description of entropy waves generation regards the flame front as a source of heat at rest. Such a model leads — in its simplest form — to an entropy source term that depends exclusively on the unsteady response of the heat release rate and upstream velocity perturbations. However, in the case of a perfectly premixed flame, which has a constant and homogeneous fuel / air ratio and thus constant temperature of combustion products, generation of entropy waves (i.e. temperature inhomogeneities) across the flame is not expected. The present study analyzes and resolves this inconsistency, and proposes a modified version of the quasi 1-D jump relations, which regards the flame as a moving discontinuity, instead of a source at rest. It is shown that by giving up the hypothesis of a flame at rest, the entropy source term is related upto leading order in Mach number to changes in equivalence ratio only.
To supplement the analytical results, numerical simulations of a Bunsen-type 2D premixed flame are analysed, with a focus on the correlations between surface area, heat release and position of the flame on the one hand, and entropy fluctuations downstream of the flame on the other. Both perfectly premixed as well as flames with fluctuating equivalence ratio are considered.
MHPS F Class Gas Turbine Upgrade Verification Results
Authors: Sakagami Naoki , Fujii Keita , Ueda Osamu 
Published: September 2016

Recently the dispatch priority of renewable energy sources is getting higher due to CO2 reduction policies [2]. This reduces operating time and revenue for Gas Turbine Combined Cycle (GTCC) plants. Upgrade programs for GTCC give a financial benefit and global CO2 reduction by the effective use of renewables [1].
The knowledge of Original Equipment Manufacturers (OEMs) can improve the performance and reliability according to user requirements. Mitsubishi Hitachi Power System (MHPS) developed upgrade programs utilizing advanced technology to improve performance for existing F class GTCC units.
The F4 technology performance upgrade is a program to increase performance by turbine cooling air reduction. It can be applied to both 50 Hz and 60 Hz engines under the scale design rule.
The upgrade development was completed with verification at commercial plants. The expected performance enhancement was achieved successfully. This paper describes our approach and verification results for user’s asset value enhancement.
A Shape Memory Alloy-Based Morphing Axial Fan Blade: Functional Characterization and Fluid Dynamic Performance
Authors: Suman Alessio , Fortini Annalisa , Aldi Nicola , Merlin Mattia , Pinelli Michele 
Published: September 2016

In a traditional automotive cooling system, energy optimization could be achieved by controlling the engine temperature by means of several sensors placed inside the cooling circuit. Nevertheless, in some cases the increasing use of a great number of sensor devices makes the control system too bulky, expensive and not sufficiently robust for the intended application. This paper presents the development of a heavy-duty automotive cooling axial fan with morphing blades activated by Shape Memory Alloy (SMA) strips that work as actuator elements in the polymeric blade structure. The application of smart materials to compact, high-energy density devices as well as the development of modeling and control systems has been of great interest during the last decade. SMAs are frequently combined within monolithic or composite host materials to produce adaptive structures whose properties could be tuned in response to external stimuli.
The blade was designed to achieve the activation of the strips (purposely thermo-mechanically treated) by means of an air stream flow. With the aim of studying the morphing capability of the adaptive structure together with the recovery behavior of the NiTi strips, four different polymeric compounds have been compared in a specifically-designed wind tunnel.
Digital image analysis techniques have been performed to quantitatively analyze the blade deflections and to evaluate the most suitable polymeric matrix for the intended application. As the airstream flow increases in temperature, the strips recover the memorized bent shape, leading to a camber variation. To study the possibility of employing SMA strips as actuator elements, a comparison with common viscous clutch behavior is proposed. The time range actuator response indicates that the SMA strips provide a lower frequency control that fits well with the engine coolant thermal requirement. The experimental results demonstrate the capability of SMA materials to accommodate the lower power actuators in the automotive field. Finally, the blade tip airfoils, reconstructed using a CAD procedure, were used to study the fluid dynamic behavior of the blade tip airfoil. A CFD numerical simulation was carried out in order to highlight the differences in the airfoil performance due to the different shapes of the blade. The analyses showed that the activated blade tip airfoil led to an increase in the lift coefficient according to the stiffness provided by the polymeric compound.
This innovative passive control system results from the selection of (i) the memorized shape of the SMA strips and (ii) the polymeric compound used for the blade structure.
Filtering Mixing Planes for Low Reduced Frequency Analysis of Turbomachines
Authors: Pullan G. , Adamczyk J. J. 
Published: September 2016

A class of problems in turbomachinery is characterised by unsteady interactions at low reduced frequencies. These interactions are often the result of perturbations with length-scale on the order of the machine circumference and examples include axial compressors operating with inlet distortion, fans with downstream pylons, and turbine rotors downstream of mid-frame struts. Typically, this unsteadiness is accompanied by higher frequency fluctuations caused by perturbations with a length-scale on the order of a blade pitch. Conventional numerical analysis of this class of problem requires computations with a time step governed by the high frequency content but a greatly reduced run time could be achieved if the time step were dictated solely by the low reduced frequency, long length-scale, interaction of interest.
In this paper, a filtering mixing plane technique is proposed that removes unwanted short length-scale perturbations at the interfaces between blade rows. This approach gives the user control over the amount of mixing that occurs at these interfaces with the limits being fully mixed-out to pitchwise uniformity (conventional mixing plane) or no mixing (conventional sliding plane). By choosing to retain only enough harmonics to resolve the low reduced frequency interaction of interest, an order of magnitude reduction in run time can be achieved.
ISO 19859: Gas Turbine Applications — Requirements for Power Generation and How Standards Can Reduce Procurement Cost
Authors: Macdonald John 
Published: September 2016

Procurement of turbo-machinery requires definition of a functional requirements and this is a complex set of specifications including performance, reliability, lifetime, operational envelope, maintainability, compliance with regulations, quality assurance, project management, documentation, installation and commissioning.
For various market and historical reasons there is a variation in the range of content, complexity and depth of the procurement documents produced by both purchasers and suppliers and this provides a challenge for both parties as a detailed and lengthy document exchange is typically required to overcome the initial disparity. The supplier needs clear project requirements and the purchaser needs to verify specification compliance and to complete a detailed and robust financial analysis. The issue for both is the time and resources expended to manage the necessary information flow which represents a substantial cost in the early phase of procurement and ties up limited resources.
Standardisation provides both parties with a pre-agreed definition of functional requirement, management of interfaces and crucially a pre-agreed management of information supply. For the purchaser this should reduce the need for an in-house technical specification. The supplier can standardise documents and expect a reduction in the variability of content and quality of tenders supplied by purchasers.
ISO 19859 is a new standard devised by both purchasers and suppliers to provide enlightened standardisation and deliver the above goals. It is estimated, based upon the author’s role both in this power plant project and the creation of the new standard that the use of the new standard would have reduced the purchaser time spent on GT engineering by between 50–60%. It is anticipated that the supplier would save time on each project, excluding the initial investment in documentation. ISO 15859 has been approved at final draft and is planned for issue at the end of March 2016.
Gaseous Fuel Flame Stabilization in a Modular Swirled Burner
Authors: Zubrilin Roman A. , Zubrilin Ivan A. , Matveev Sergey S. , Matveev Sergey G. 
Published: September 2016

Stable combustion is one of the main requirements for combustion chambers of gas turbine engines. Therefore, the prediction of combustor stable operation limits during the design stage is an important task. The stable operation limits with a sufficient degree of accuracy can be determined by experiments or using computational fluid dynamics.
The present paper describes a numerical and experimental investigation of swirled premixed flame stabilization in a modular swirled burner (MSB). The burner has a vane swirler and a diffuser with a cylindrical tube downstream of the swirler. This design has several advantages. First, the cylindrical tube protects the flame from external disturbances and acts as the pre-chamber in which combustion efficiency can reach high values. Secondly, the swirled flow of the fresh mixture passes along the walls of the tube and prevents them from overheating.
The influence of the swirler vanes angle on MSB lean blow out (LBO) was experimentally and numerically investigated. The results of the experiments were also used to validate the simulation results. All studies were conducted under atmospheric conditions in an open-space laboratory environment. Three-dimensional modeling was carried out using the large eddy simulation (LES) with a Smagorinsky–Lilly subgrid model. Combustion was described within the Flamelet Generated Manifold model. Initially, the influence of the size and shape of outlet boundary, the mesh resolution and turbulent-chemistry interaction models was investigated. As a result the configuration of the model was received, which allows simulating LBO with sufficient accuracy. Stable operation limits for several types of MSB geometries and different fuels (methane and propane) were subsequently established. It was found that in the case of swirler vane angle equal to 45 degrees the range of stable operation limits is wider than in the case of 60 degrees. The influence of pre-chamber length on LBO was studied only numerically. It was discovered that with increasing pre-chamber length, the LBO limits become wider, but the possibility of the tube walls overheating becomes higher too.
Reheat Burner Front Panel Produced by Additive Manufacturing Challenges: Strategies and Engine Validation
Authors: Maurer Michael , Sierra Patricia , Meng Patrik 
Published: September 2016

Additive manufacturing radically changes the design process giving unprecedented freedom of design and enabling a step change in part performance.
The general idea of selecting appropriate candidates within the Alstom hot gas parts portfolio is described in this paper. The strategy as used in the selection process is to identify parts with either a high (internal) complexity or to choose parts with a high number of sub-parts and the necessary high number of assembly steps, which are needed with the current manufacturing methods (e.g. precision casting or weld assemblies).
The current reheat burner front panel of the heavy duty gas turbine is today produced from three metal layers. The layer facing the hot gas contains the complex near-wall cooling channel system. The metal sheet facing the cold side features the acoustic damping volumes. An intermediate metal sheet separated the two systems. Brazing is used to assemble the sup parts into the final front panel. With the identified strategy to use additive manufacturing, the design is adapted to allow the production of a single component that includes all the functionality and avoids heavy machining and assembly steps.
The paper focuses on the design changes and challenges that were required and observed during the adaption of the GT26 (Rating 2011 onwards) reheat burner front panel. Also the necessary adaptions of the qualification process and the lifetime assessments are described in detail.
Finally, the additive manufacturing version of the reheat burner front panel was subjected to a heavy duty test program. Engine tests were completed. The disassembled SLM component was found in excellent condition. Subsequent material investigations have confirmed the good part condition from a metallurgical point of view.
High-Pressure Turbine Rim Seal Design for Increased Efficiency
Authors: Chilla M. , Hodson H. P. , Pullan G. , Newman D. 
Published: September 2016

In high-pressure turbines, compressor air is used to purge the disc space in an effort to protect the blade roots and the turbine disc from overheating and failure. The purge air exits the disc space through a rim seal at the hub of the main annulus and is subsequently entrained in the rotor hub endwall flows. The introduction of the purge air into the turbine main stream causes additional losses and therefore reduced turbine efficiency. For a given rim sealing mass flow rate, the rim seal geometry has to be designed in a way that reduces the detrimental impact of the sealing flow on turbine performance.
In this study, the rim seal of a generic high-pressure turbine, representative of modern large civil aero-engines, is redesigned under consideration of the pressure field upstream of the rotor. Unsteady numerical simulations of the turbine stage are used to compare the aerodynamic impact of three different rim seal designs. The numerical simulations predict an increase in the time-averaged turbine stage efficiency of over 0.2% for the stage configuration with the final redesigned rim seal compared to the configuration with the original baseline rim seal geometry at the nominal sealing mass flow rate.
Fouling Detection in Low Speed Fan Using Near-Field DIY Sound Pressure Sensors
Authors: Corsini Alessandro , Tortora Cecilia 
Published: September 2016

This work investigates the dynamics of rotating stall of a low speed axial fan in presence of fouling on the blades. Rotating stall is an aerodynamic issue of recognized importance in turbomachinery. The combination of rotating stall and presence of particles of dust and dirt from the surrounding environment, may lead to further issues in terms of performance, stall limit and blades life.
In this paper the identification of the rotating stall pattern is carried out using time-resolved sound measurements in the far field region by means of a condenser microphone. The experimental tests are carried out with various geometries of fouling in order to evaluate the system ability to detect acoustically fouling and rotating stall.
The results have been validated against state of the art techniques described in the literature. The acquired signals have been analysed using frequency domain analysis, and time domain analysis using a phase space reconstruction inspired technique. Both of the approaches demonstrate a modification of the stall dynamics in the low speed fan and allow the identification of diverse stall precursors and fouling presence.
Experimental Investigation on the Time-Space Evolution of a Laminar Separation Bubble by POD and DMD
Authors: Lengani D. , Simoni D. , Ubaldi M. , Zunino P. , Bertini F. 
Published: September 2016

A time resolved Particle Image Velocimetry (TR-PIV) system has been employed to investigate a laminar separation bubble which is induced by a strong adverse pressure gradient typical of Ultra-High-Lift lo pressure turbine blades. Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) are described and applied within the paper. These techniques allow reducing the degrees of freedom of complex systems producing a low order model ranked by the energy content (POD) or by the modal contribution to the dynamics of the system itself (DMD), useful to highlight the dominant dynamics.
The time-space evolution of the laminar separation bubble is characterized by rollup vortices shed in the surround of the bubble maximum displacement as a consequence of the Kelvin-Helmholtz instability process as well as by a low frequency motion of the separated shear layer. The decomposition techniques proposed allow the identification of these coherent structures and the characterization of their modal properties (e.g. temporal frequency, spatial wavelength and growth rate).
The POD separates the different dynamics that induce velocity fluctuations at different frequencies and wavelength looking at their contribution to the overall kinetic energy. The DMD provides complementary information: the unstable spatial frequencies are identified with their growth (or decay) rates. DMD modes associated with the Kelvin-Helmholtz instability and the corresponding vortex shedding phenomenon clearly dominate the unsteady behavior of the laminar separation bubble, being characterized by the highest growth rate. Modes with longer wavelength describe the low frequency motion of the laminar separation bubble and are neutrally stable. Results reported in the paper prove the ability of the present methods in extracting the dominant dynamics from a large dataset, providing robust and rapid tools for the in dept analysis of transition and separation processes.