bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive Mesh Refinement for DDES Simulation on Transonic Compressor Cascade With Unstructured Mesh
Authors: Gou Jinlan , Su Xinrong , Yuan Xin
Published: September 2016

There are local flow phenomena like shock wave/boundary interaction and tip leakage flow which strongly influence the compressor performance and stability. AMR (Adaptive Mesh Refinement) strategy shows attractive property for automatically refining local mesh and predicting higher local phenomenon details. This paper develops the AMR strategy for turbomachinery with unstructured mesh. Curved surface boundary matching is focused in AMR process for achieving high level simulation accuracy. The developed AMR strategy is used to improve shock wave prediction in this paper. Firstly two dimensional RANS simulation of compressor cascade L030-4 is conducted to test the AMR strategy. Refined mesh shows better shock wave details compared with the almost none shock wave structure of baseline mesh. Then quasi-3D DDES (Delayed Detached Eddy Simulation) simulation of this compressor cascade is conducted. Shock wave oscillation phenomenon is clearly shown for this cascade. Local mesh of shock wave oscillation region is automatically refined by AMR. The refined mesh predicts better shock wave details and better turbulence motion comparing to the baseline mesh.
The Effect of Thermochemical Non-Equilibrium on the Aerodynamics of Osculating-Cone Waverider
Authors: Liu Zhen , Jun Liu , Feng Ding , Zhixun Xia
Published: September 2016

The influence of thermochemical non-equilibrium effect towards the aerodynamic performances of an osculating-cone waverider is analyzed in this paper, and the osculating-cone waverider is typical configuration of near space vehicles. Two different gas models, namely thermochemical non-equilibrium and perfect gas models are employed. The obtained results show that the thermochemical non-equilibrium effect is significant near the windward boundary layer at the tail of the waverider, and the non-equilibrium effect makes the pressure center of the osculating-cone waverider move forward by about 1.33% of the whole craft’s length at the altitude of 55km, and this must be taken into consideration in the balance design of aircraft.
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°.
Effect of In-Hole Roughness on Film Cooling From a Shaped Hole
Authors: Schroeder Robert P. , Thole Karen A.
Published: September 2016

While much is known about how macro-geometry of shaped holes affects their ability to successfully cool gas turbine components, little is known about the influence of surface roughness on cooling hole interior walls. For this study a baseline shaped hole was tested with various configurations of in-hole roughness. Adiabatic effectiveness measurements at blowing ratios up to three showed that in-hole roughness caused decreased adiabatic effectiveness relative to smooth holes. Decreases in area-averaged effectiveness grew more severe with larger roughness size and with higher blowing ratios for a given roughness. Decreases of more than 60% were measured at a blowing ratio of three for the largest roughness values. Thermal field and flowfield measurements showed that in-hole roughness caused increased velocity of core flow through the hole, which increased the jet penetration height and turbulence intensity resulting in increased mixing between coolant and the mainstream. Effectiveness reductions due to roughness were also observed when roughness was isolated to only the diffused outlet of holes, and when the mainstream was highly turbulent.
High Temperature Deformation of Inconel 718Plus™
Authors: Ozturk Utkudeniz , Cabrera Jose Maria , Calvo Jessica
Published: September 2016

Since its introduction in 2003, alloy 718Plus™ spurred a lot of interest owing to its increased maximum service temperature over conventional Inconel 718 (704°C vs 650°C), good formability and weldability together with its moderate cost. Understanding the high temperature deformation characteristics and microstructural evolution is still of interest to many. It is known that the service performance and hot-flow behavior of this alloy is a strong function of the microstructure, particularly the grain size. To develop precise microstructure evolution models and foresee the final microstructure, it is important to understand how and under which forming conditions softening and precipitation processes occur concurrently. In this work, the softening behavior, its mechanisms and the precipitation characteristics of 718Plus™ were investigated in two parallel studies. While cylindrical compression tests were employed to observe the hot-flow behavior, the precipitation behavior and other microstructural phenomena such as particle coarsening were tracked via hardness measurements. A PTT diagram was reported and modeling of the flow curves via hyperbolic sine model were discussed in the light of the PTT behavior. Both “apparent” approach and “physically based” approach are implemented and two different sets of parameters were reported for the latter. Finally, recovery and recrystallization kinetics are described via Estrin-Mecking and Bergstrom, and Avrami kinetics, respectively.
Integration of Modern F, G, H and J Class in Combined Cycle Applications: An EPC Contractor Perspective
Authors: Zachary Justin , Kallianpur Vinod , So Byungsik
Published: September 2016

The traditional approach for developing new and upgrade model large frame industrial gas turbines is changing rather dramatically. Large industrial gas turbine design evolutions have typically been built around a basic core design concept that remained unchanged. The departure from tradition has been, in some cases, sparked by the merger between erstwhile competitors. Thus the models that follow a merger benefit from leveraging the best of available knowledge from both companies: specialized design methods, manufacturing practices, materials, combustion, etc. Another recent trend in GT development is to transfer select portions of design concepts and related experience, and integrate that knowledge into a new model. Both these trajectories of development involve some changes to the core design reference architecture: e.g. number of rows in turbine section, rotor design architecture, flow path shape, blade locking approach, exhaust diffuser, inlet scroll, etc., and needing more attention to detail by the EPC for being able to meet the customer expectations for life cycle costs, performance degradation, reliability and availability. The expanded technical capability of the OEMs to accelerate new technical innovations for propelling the next economic growth engine is indeed a very exciting prospect for EPC contractors. Already, modern “H” and “J” class gas turbines are commercially available for over 60 per cent net efficiency in combined cycle power plant application. This paper shares an EPC contractor’s experience in developing Combined Cycle Power Plants with two advanced commercially available gas turbine models in Korea (Mitsubishi’s M501J model) and Malaysia (Siemens SGT. 5-8000H model).
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.
Random Behavior of Kerosene Spray Autoignition in Crossflow
Authors: Zhao Yongsheng , Zhang Chi , Lin Yuzhen
Published: September 2016

Based on the flow reactor with rectangle cross-section, this paper studies the spray autoignition characteristics of liquid kerosene injected into air crossflow under high temperature and high pressure conditions. Millisecond-level kerosene injection, millisecond-level photoelectric detection, and high speed photography record experiment techniques are adopted in this research. The operating conditions of this research are as follows: 2.3MPa inlet pressure, 917K inlet temperature, fuel/ air momentum ratio of 52, and Weber number of 355. Photoelectric sensor and photomultiplier equipped with CH filter are used to get the autoignition delay time (ADT). A total of 320 experiments are conducted under the same operating conditions in order to obtain the random ADT probability distribution. The high speed photography is utilized to observe and record the developing process of spray autoignition of kerosene. The results show that the ADT varies from 2.5–5.5millisecond (ms) in the above operating conditions, and confirm the existence of the random behavior of kerosene spray autoignition in the crossflow. These random behaviors of ADT can be correlated well with Gauss distribution. The primary analysis shows that the random behavior stems from the random distributions in the diameter and dispersion due to intrinsic turbulence breakup and transportation which dominate the characteristics of spray autoignition.
Effect of the Diffuser on the Inlet Acoustic Boundary in Combustion-Acoustic Coupled Oscillation
Authors: Han Xiao , Hui Xin , Qin Hao , Lin Yuzhen , Zhang Man , Sung Chih-Jen
Published: September 2016

Combustion instability is one of the major challenges in Lean Premixed Pre-vaporized (LPP) combustion technology. The effect of inlet conditions on combustion instability has been widely studied. But the diffuser, located between the compressor outlet and combustor inlet, has received little attention regarding its effect on combustion instability. This paper experimentally investigated the combustion instability in a single sector LPP combustor with and without a diffuser. Pressure data has been recorded and used to indicate the oscillation of the system. The results show that with the diffuser the combustor showed no prominent oscillation, and strong thermoacoustic oscillation at around 400 Hz was observed without the diffuser. Further analysis has been conducted by using acoustic net model. The resonant mode frequency of the entire combustor system and each section separately were calculated. It was found that in the case of the diffuser, the resonant frequency shifted from 400 Hz to 453 Hz, which avoiding interacting with heat release within the flame tube, thus help to stabilize the combustor system.
Numerical Investigation of the Effect of Diffuser and Volute Design Parameters on the Performance of a Centrifugal Compressor Stage
Authors: Yu Lei , Cousins William T. , Shen Feng , Kalitzin Georgi , Sishtla Vishnu , Sharma Om
Published: September 2016

In this effort, 3D CFD simulations are carried out for real gas flow in a refrigeration centrifugal compressor. Both commercial and the in-house CFD codes are used for steady and unsteady simulations, respectively. The impact on the compressor performance with various volute designs and diffuser modifications are investigated with steady simulations and the analysis is focused on both the diffuser and the volute loss, in addition to the flow distortion at impeller exit. The influence of the tongue, scroll diffusion ratio, diffuser length, and cross sectional area distribution is examined to determine the impact on size and performance. The comparisons of total pressure loss, static pressure recovery, through flow velocity, and the secondary flow patterns for different volute designs show that the performance of the centrifugal compressor depends upon how well the scroll portion of the volute collects the flow from the impeller and achieves the required pressure rise with minimum flow losses in the overall diffusion process. Finally, the best design is selected based on compressor stage pressure rise and peak efficiency improvement. An unsteady simulation of the full wheel compressor stage was carried out to further examine the interaction of impeller, diffuser and the volute. The unsteady flow interactions are shown to have a major impact on the performance of the centrifugal stage.
Numerical Simulation of Pollutant Emission of a Turbojet Engine With Water Injection
Authors: Sun Lanxin , Sun Tao , Wang Yanmin , Yang Wen
Published: September 2016

Numerical simulation of a turbojet engine with water injection from the compressor inlet has been executed to evaluate the effect of wet compression on the pollutant emission in this paper. Water injection technique has shown the advantage of reducing the compression work and increasing the power output, and can also reduce the gas temperature in the combustion chamber and turbine which can help to reduce the thermal fatigue of the hot parts and extend their service life. Previous studies have indicated that there is a great relationship between pollutant emission of NOx and the combustion temperature, so the decrease of combustion temperature can reduce the amount of pollutant production of aircrafts especially near the airport because of the takeoff and landing of the aircrafts. And this potential of meeting the increasingly stringent pollutant emission target of water injection technique has aroused great interest of the world major engine manufacturers and research institutions. Compared with cases of no water injection, the results of this study show that the inlet temperature of combustion chamber drops obviously because of water injection, the average NO concentration in combustion chamber decreases greatly, but the concentration of CO increases significantly. Analysis of the results shows that based on fuel consumption of per unit mass the relation between the NO production in combustion chamber and the mass water evaporation varies according to the exponential law and CO production in water injection cases is similar to the cases without water injection.
Aerodynamic Performance and Acoustic Characteristics of Bionic Airfoil Inspired by Three-Dimensional Long-Eared Owl Wing Under Low Reynolds Number
Authors: Li Dian , Liu Xiaomin
Published: September 2016

The aerodynamic performance and noise of the blade are two important aspects which people pay much attention nowadays in the design of turbine machinery such as centrifugal fan and axial flow fan. In this paper, the three-dimensional model of the long-eared owl wing is established based on the section theory and fitting formula firstly. And then, unsteady aerodynamic and acoustic characteristics of the bionic blade are numerically investigated using Large-Eddy Simulation (LES) and the Ffowcs Williams-Hawkings (FW-H) equation based on Lighthill’s acoustic theory. The results indicate that the deeply concaved lower surface near the wing root plays a significant role in improving the lift-to-drag ratio. The lift coefficient and drag coefficient of the bionic blade is analyzed by comparing two-dimensional and three-dimensional results. The cross section profiles near the wing root possess the larger lift coefficients and the lesser drag coefficients, even than the three-dimensional long-eared owl wing. The size of the separation bubble grows at increasing angle of attack. The 40% cross-section profile of the long-eared owl wing could increase the distance between the corresponding vortex centers with wall surface thus reducing the range of the vortex shedding near the wall effectively. The iso-Q surfaces show that the location of the vortex shedding and the movement of separation bubble. When the angle of attack α is 5°, the aerodynamic noise generated by the bionic blade is lower than in other angle of attack condition. The minimum value of the sound pressure level (SPL) is even 17.9dB on the y-direction. In the range of 5°–15°, the strength and size of the vortex motion increase with the increase of the angle of attack. The far-field noise suggests the directivities of dipole noise. The range of the separation bubbles act as the most influence of the noise generation. The sound pressure level (SPL) of bionic blade at α = 5° is less than other conditions and the minimum value is even 17.9dB. The thin airfoil near the wingtip could decrease the pressure fluctuation from the blade surface that can reduce the unsteady aerodynamic noise. It means the unique structure of the long-eared owl wing can suppresses the unsteady pressure fluctuation on the surface which could decrease the noise generated by the wing surface.
Efficiency Improvements in an Industrial Steam Turbine Stage: Part 2
Authors: Deshpande Srikanth , Thern Marcus , Genrup Magnus
Published: September 2016

Improvement in isentropic total to total efficiency of a low reaction turbine stage by airfoil redesign was considered in first part of the paper. Further, modifications in the flow path of the baseline stage is considered in second part of the paper. Flow path of the baseline stage incorporates axisymmetric meridional endwall contour (commonly called Russian kink). For a stage comprising of high aspect ratio blades, assessment of performance with endwall contour is performed. Alternatives, if required for endwall contour had to be explored and numerically verified. Endeavor in the present paper is in this direction. Static pressure distribution at the stator exit is considered as the main objective. Along with flow path modification, stator modifications like vortexing and lean are attempted to obtain stator exit static pressure distribution similar to baseline case. Straight lean on stator provides good results in terms of reducing stator exit pressure gradient as well as reducing gradient of rotor inlet swirl. Since the pressure distribution at stator exit also drives the tip leakage flow, effect of flowpath and stator modifications on tip leakage flow is studied. Performance numbers are reported for cases with and without tip shroud.
Numerical Investigation of the Flow Field and Aerodynamic Load on Impellers in Centrifugal Compressor With Different Radial Inlets
Authors: Xin Jianchi , Wang Xiaofang , Zhou Lusheng , Ye Zhong , Liu Haitao
Published: September 2016

Based on Computational fluid dynamics (CFD) simulation, this study investigates the interior flow in a radial inlet, and helps to figure out the flow phenomenon in radial inlet and the aerodynamic load on the downstream impellers. Three different radial inlets, i.e., original model without guide vanes (OGV), with evenly distributed guide vanes (EGV) and with unevenly distributed of guide vanes (UGV) are considered. The results indicate that the performance of the compressor with UGV outperforms the others, which increases the polytropic efficiency of the centrifugal compressor by 2.3% and provides better flow parameter distribution. The inlet distortion created by the radial inlet affects the aerodynamic load distribution on the downstream impeller. Running unsteady simulations, the aerodynamic load on the impeller’s leading edge is obtained for the three radial inlets. The dominant frequency and pulse amplitude obtained by Fast Fourier transforms (FFT), reveal that the main frequencies of the aerodynamic load present different distributions under three radial inlets. The UGV model provides the minimal amplitude value at machine rotating frequency when compared with the other two models, and the harmonics of the impeller passing frequency appear obviously, which is similar to that under the axial flow inlet condition.
Virtual Sensing for Rotordynamics
Authors: Moschini Simona , Gryllias Konstantinos , Desmet Wim , Pluymers Bert
Published: September 2016

During last decades the scientific community focused its attention on energy efficiency solutions. Materials have been developed or improved to avoid energy dispersions and new strategies have been developed in order to exploit at best renewable and non renewable energy sources. Other paths are currently followed to pursue the same goal, for instance, the introduction of innovative monitoring system and techniques. In this framework, the concept of virtual sensing reveals itself as one of the most powerful tools. Several physical quantities are relevant to define the health status of the system. Unfortunately, many of these quantities cannot be directly measured in many practical applications due to lack of specific sensor or to the environment in which the system is operating. As a consequence, state estimation techniques come out as an extremely helpful tool. These techniques allow combining the world of measurements with the one of numerical modeling leading to the estimation of the desired unmeasurable system quantities. In the current research a Kalman Filter based algorithm is applied to investigate and assess the health condition of a rotor system. The system under investigation is a classical example in rotordynamics. The attention is focused on the estimation of one of the most common malfunction in rotating machinery: the unbalance.
Overall Cooling Effectiveness on a Flat Plate With Both Film Cooling and Impingement Cooling in Hot Gas Condition
Authors: Shi Bo , Li Jia , Li Mingfei , Ren Jing , Jiang Hongde
Published: September 2016

This paper presents experimental results of temperature distribution on a flat plate with both film cooling and impingement cooling configurations. The film plate consists of 4 rows of round holes injected at an angle of 30°. The impingement plate has a 6×6 jet array. Mainstream temperature is 100°C, and coolant temperature is around 30°C, which results in a density ratio of 1.2. To acquire a similar heat transfer condition with real engine, Bi number is matched by choosing MACOR as the plate material, which has a proper thermal conductivity of 1.7 W/m·K. A series of experiments were conducted, with blowing ratio ranges from 0.7 to 2.2. Infrared camera was used to measure the outer surface temperature. Overall cooling effectiveness was found to reach its maximum when blowing ratio is around 1.0. When the coolant continue to increase, the overall cooling effectiveness decreases and the cooling uniformity is also decreasing.
Sensitivity Analysis and Experimental Validation of Transient Performance Predictions for a Short-Range Turbofan
Authors: Culmone Maria V. , Garcia-Rosa Nicolás , Carbonneau Xavier
Published: September 2016

Transient effects are important features of engine performance calculations. The aim of this paper is to analyze a new, fully transient model implemented using the PRopulsion Object Oriented Simulation Software (PROOSIS) for a civil, short range turbofan engine. A transient turbofan model, including the mechanical inertia effect has been developed in PROOSIS. Specific physical effects such as heat soakage, mass storage, blade tip clearance and combustion delay have been implemented in the relevant components of PROOSIS to obtain a fully transient model. Since a large number of components are concerned by all the transient effects, an influence study is presented to determine which are the most critical effects, and in which components. Inertia represents the relevant phenomenon, followed by thermal effects, combustion delay and finally mass storage. The comparison with experimental data will provide a first validation of the model. Finally a sensitivity study is reported to assess the impact of uncertain knowledge of key input parameters in the response time prediction accuracy.
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.
Flame Stabilization and Emission Characteristics of a Prototype Gas Turbine Burner at Atmospheric Conditions
Authors: Kundu Atanu , Klingmann Jens , Subash Arman Ahamed , Collin Robert
Published: September 2016

In the present work, a downscaled prototype 4th generation Dry Low Emission gas turbine (SGT-750) burner (designed and manufactured by Siemens Industrial Turbomachinery AB, Sweden) was investigated using an atmospheric experimental facility. The primary purpose of the research is to analyze flame stability and emission capability of the burner. OH Planar Laser-Induced Fluorescence (OH-PLIF), and chemiluminescence imaging were performed to characterize the flame structure and location. From the OH-PLIF images, the reaction zone and post flame region could be identified clearly. The chemiluminescence images provide an estimation of the overall heat release from the secondary combustion zone inside the Quarl. Emission was measured using a water-cooled emission probe, placed at the exit of the combustor to sample NOx and CO concentrations. The global equivalence ratio (Φ) was varied from rich to lean limit (flame temperature change from 1950 K to 1570 K) for understanding the stable and instable reaction zones inside the Quarl. Total thermal power was varied from 70 kW to 140 kW by changing global Φ and burner throat velocity (60 to 80 m/s). Near the lean blowout (LBO) event (at global Φ ∼ 0.4), instability of reaction zone is revealed from the flame images. Incorrect modulation of Pilot and RPL fuel splits show instable flame. Flame instability mitigation was possible using higher amount of RPL and Pilot fuel (trade-off with emission performance). The main flame LBO margin was extended by applying higher Pilot fuel and using higher preheat air temperature. Numerical analysis was carried out using Fluent to understand the scalar and vector fields. A basic chemical reactor network model was developed to predict the NOx and CO emission with experimental results. NOx emission prediction showed good agreement with experiment; whereas the model is failed to capture accurate CO emission in the lean operating points.
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.
Comparing Spray and Flame Behavior in a Swirl Liquid Fueled Lean Burner With Single and Multipoint Injections
Authors: De Giorgi M. G. , Sciolti Aldebara , Campilongo S. , Ficarella A.
Published: September 2016

Recent advances in gas turbine combustor design aimed at achieving low NOx emissions have focused on locally leaner combustion by rapid mixing of fuel and air. Multipoint injection leads to a fast and efficient mixing with the control of the spatial fuel distribution. In the present work, an experimental study on combustion phenomena in a liquid fuel burner, which operates in non-premixed (single point injection) and partially-premixed regimes (multipoint injections), was carried out in order to investigate the effect of the injection mode. In both the cases the lean combustion behavior was investigated in proximity of the blow-out limit. An intensified high rate CCD was used for flame imaging in the ultraviolet spectral range. It was equipped with different optical filters to selectively record single species chemiluminescence emissions (e.g. OH*, CH*). Analogous filters were also used in association with photomultiplier (PMT) tubes. Finally the NOx emissions were monitored. Furthermore, preliminary computational fluid dynamic (CFD) simulations were also performed under the typical combustor operation conditions to provide insight into the mixing of the air and the fuel under the different injection modes and the related flame pattern.
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.
The Effect of Particle Loading, Size, and Temperature on Deposition in a Vane Leading Edge Impingement Cooling Geometry
Authors: Whitaker Steven M. , Peterson Blair , Miller Alex F. , Bons Jeffrey P.
Published: September 2016

Experiments have been performed to assess the effects of particle loading, size, and temperature on flow blockage development in a geometry representative of a gas turbine nozzle guide vane leading edge. Tests with Arizona Road Dust in 0–5, 0–10, and 0–20 micron nominal size distributions showed that particle loading rates had no substantial impact on flow blockage development over the 700–866 K temperature range. Tests with the 0–10 micron dust at various flow temperatures indicated a first order effect of temperature on blockage development, particularly for temperatures above 700 K. Testing with 5–10 and 10–20 micron size distributions revealed a clear distinction between the effects of different particle sizes. Evaluation of the experimental data and particle size distributions indicated that particles smaller than 3.25 microns were primarily responsible for blockage development, a result which was further corroborated using a physics-based deposition model. Particles larger than 5 microns were shown to produce a removal mechanism, both for deposits that are in the process of growing and for those which are already established. Overall, the experiments indicate that comparisons between laboratory scale deposition studies and data from field serviced engine hardware can be reliably made in spite of large variations in the rate of particle loading. However, parameters such as flow temperature and particle size should be closely matched when performing experiments, as these have a first order effect on blockage development.
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.
Noise-Induced Dynamics in the Subthreshold Region in Thermoacoustic Systems
Authors: Saurabh Aditya , Kabiraj Lipika , Steinert Richard , Paschereit Christian Oliver
Published: September 2016

This article is a report of experiments conducted in order to investigate the role of noise on thermoacoustic systems. In contrast to most studies in this direction, in the present work, the role of noise in the subthreshold region, prior to the (subcritical) Hopf bifurcation and the associated saddle-node bifurcation is considered. Although, in this regime, a thermoacoustic system is stable and does not undergo transition to self-excited thermoacoustic oscillations, the system can feature dynamics that arise due to the proximity of the system to the approaching Hopf bifurcation in response to noise. Experiments were performed on a model thermoacoustic system featuring a laminar flat flame. Noise was introduced in a controlled manner and the effect of increasing levels of noise intensity was studied. Results presented here show that noise addition induces coherent oscillations. The induced coherence can be quite significant, and is dependent on the noise amplitude and proximity to the Hopf bifurcation. Furthermore, this noise-induced behavior is characterized by a well-defined ‘resonance-like’ response of the system: An optimum level of coherence is induced for an intermediate level of noise. For practical thermoacoustic systems (e.g. combustors), which are inherently noisy due to factors such as flow turbulence and combustion noise, these results can have important implications.
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.
Fast High Order Large Eddy Simulations on Many Core Computing Systems for Turbomachinery
Authors: Lu Yi , Liu Kai , Dawes W. N.
Published: September 2016

The overall aim of our research is to enable overnight high fidelity LES for realistic industry problems on affordable computing resource. We have adopted a “3E” approach: high spatial discretization Efficiency on general unstructured meshes, high Efficiency accurate time integration and high computing Efficiency on modern low cost HPC hardware. Our approach is centered on high order Flux Reconstruction with local time stepping — the STEFR algorithm [1]. In this paper, an offload-mode version of this code is described targeted at a heterogeneous many-core computing system based on low cost commodity hardware — Intel PHI cards. Three key techniques are introduced to achieve high FLOP rates — and optimal usage of non-equilibrium memory of both CPU and the many core coprocessor — with three levels of parallelization, multi-level nonequilibrium mesh partition and an asynchronous computing structure. A series of high order LES runs for a high lift low pressure turbine blade and a transonic turbine blade, with different order of accuracy, both fully wall-resolved and wall-modelled, were performed, analyzed and presented. This work demonstrates that the high order STEFR method has the potential to support over-night LES for realistic industrial problems on affordable computing resource.