bluuebunny/crossref_metadata_2025 huggingface dataset:
Virtual Gas Turbine: Pre-Processing and Numerical Simulations
Authors: Wang Feng , Carnevale Mauro , Lu Gan , di Mare Luca , Kulkarni Davendu
Published: September 2016

The design process of a gas turbine engine involves interrelated multi-disciplinary and multi-fidelity designs of engine components. Traditional component-based design process is not always able to capture the complicated physical phenomenon caused by component interactions. It is likely that such interactions are not resolved until hardware is built and tests are conducted. Component interactions can be captured by assembling all these components into one computational model. Nowadays, numerical solvers are fairly easy to use and the most time-consuming (in terms of man-hours) step for large scale gas turbine simulations is the preprocessing process. In this paper, a method is proposed to reduce its time-cost and make large scale gas turbine numerical simulations affordable in the design process. The method is based on a novel featured-based in-house geometry database. It allows the meshing modules to not only extract geometrical shapes of a computational model and additional attributes attached to the geometrical shapes as well, such as rotational frames, boundary types, materials, etc. This will considerably reduce the time-cost in setting up the boundary conditions for the models in a correct and consistent manner. Furthermore, since all the geometrical modules access to the same geometrical database, geometrical consistency is satisfied implicitly. This will remove the time-consuming process of checking possible mismatching in geometrical models when many components are present. The capability of the proposed method is demonstrated by meshing the whole gas path of a modern three-shaft engine and the Reynold’s Averaged Navier-Stokes (RANS) simulation of the whole gas path.
A Database of Optimal Airfoils for Axial Compressor Throughflow Design
Authors: Schnoes Markus , Nicke Eberhard
Published: September 2016

This text describes methods to organize a large set of optimized airfoils in a relational database and its application in throughflow design. Optimized airfoils are structured in five dimensions: inlet Mach number, blade stagger angle, pitch-chord ratio, maximum thickness-chord ratio and a parameter for aerodynamic loading. In this space, a high number of airfoil geometries is generated by means of numerical optimization. Each airfoil geometry is tailored to its specific requirements and optimized for a wide working range as well as low losses. During the optimization of each airfoil, performance in design and off-design conditions is evaluated with the blade-to-blade flow solver MISES. Together with airfoil geometry, the database stores automatically calibrated correlations which describe cascade performance in throughflow calculation.

Based on these methods, two subsonic stages of a 4.5-stage transonic research compressor are redesigned. Performance of baseline and updated geometries is evaluated with 3D CFD.

The overall approach offers accurate throughflow design incorporating optimized airfoil shapes and a fast transition from throughflow to 3D CFD design.
Prediction of Compressor Fouling Rate Under Time Varying Operating Conditions
Authors: Hanachi Houman , Liu Jie , Banerjee Avisekh , Chen Ying
Published: September 2016

Performance of the compressors deteriorates due to detrimental effects of fouling on the aerodynamic flow characteristic. The compressors need periodic clean up services to re-gain the designed performance. Apart from the operating time, the ambient and the operating conditions affect the fouling phenomenon making accurate scheduling for predictive maintenance very difficult. In this work, the symptoms of compressor fouling are captured through the evolution of the compressor map in terms of loss of isentropic efficiency and mass flow decrease. Compressor mass flow and the rate of humidity condensation at the inlet of the compressor are identified as the effective factors on the fouling rate. Humidity condensation has a competing effect on fouling rate; increment of the condensed humidity up to a certain level accelerates the fouling rate, while additional mist has an inverse effect. The complex effect of the condensed humidity along with the air mass flow is extracted through training an adaptive neuro-fuzzy inference system. The resulting model reveals how the efficiency and the mass flow of the compressor map vary as a result of fouling development, given the mass flow and the humidity condensation history. The methodology is verified using data from a similar compressor commissioned at a different period.
Blade Incipient Crack Determination for Centrifugal Compressor Based on Pressure Pulsation Signal Feature Extraction
Authors: Li Hongkun , He Changbo , Jiang Daren , Wang Xuejun
Published: September 2016

Centrifugal compressor is a piece of key equipment for factories. Among the components of a centrifugal compressor, impeller is a pivotal part as it is used to transform kinetic energy to pressure energy. The blades are exposed to centrifugal forces, gas pressure, and the friction force which usually lead to cracks.

Therefore, early crack feature extraction and pattern recognition are important to prevent it from failure. Although time series analysis for monitored signals can be used on feature extraction, it is not enough. So the incipient weak feature extraction method should be investigated. In this research, pressure pulsation sensors arranged close to crack area are used to monitor the blade crack signal and extract the feature information. As the different kinds of interference of flow, the pressure pulsation signals for a centrifugal compressor are full of nonlinear characteristics. Therefore, how to obtain the weak information from monitored signals effectively should be investigated. A method on blade crack classification is present by continuous wavelet transform (CWT) and envelope spectrum in this research. Simulation signal analysis and experimental investigation on blade crack classification are carried out to verify the effectiveness of this method. The results show that it is an effective tool for blade incipient crack classification for a centrifugal compressor.
Correlation-Based Riblet Model for Turbomachinery Applications
Authors: Koepplin Viktor , Herbst Florian , Seume Joerg R.
Published: September 2016

An empirical riblet model for manufactured V-shaped and trapezoidal riblets which is suitable for turbomachinery application is presented. The implementation of the riblet effect employs a correlation-based correction for the damping of the specific dissipation rate omega in the vicinity of the wall which has been previously presented by other researchers. In the current paper the correlations are extended into the drag-increasing regime and are extended to account for the effect of misalignment of the riblets relative to the flow and for the effect of adverse pressure gradients. In order to account for the latter in modern, massive parallel CFD-codes, a local Clauser-Parameter has been newly derived. The model is implemented in the 3D turbomachinery design code TRACE and validated with flat plate measurement data and a NACA6510 compressor cascade. The predictions of the experimental values are in very good agreement with the experimental data, showing the capability of the model for designing riblet structured turbomachinery blading.
Steady State Performance Simulation of Natural Gas Pipeline Driven by Compressor Stations
Authors: Suleiman S. M. , Li Y. G.
Published: September 2016

Natural gas pipeline plays an important role in transporting natural gas over a long distance. Its performance and operating behavior are affected by many factors, such as ambient conditions, natural gas flow rate, operation and control of compressor pumping stations, etc. Better understanding of the performance and behavior of an integrated pipeline-compressor system used for gas transmission will be beneficial to both design and operation of natural gas pipelines.

This paper introduces a novel steady-state thermodynamic performance simulation approach for natural gas pipelines based on fundamental thermodynamics with the inclusion of the coupling between a pipeline and compressor pumping stations. A pipeline resistance model, a compressor performance model characterized by an empirical compressor map and a pipeline control schedule for the operation of an integrated pipeline-compressor system are included in the simulation approach. The novel approach presented in this paper allows the analysis of the thermodynamic coupling between compressors and pipes and the off-design performance analysis of the integrated pipeline-compressor system.

The introduced simulation approach has been applied to the performance simulation of a typical model pipeline driven by multiple centrifugal compressor pumping stations. It is assumed in the pipeline control schedule that the total pressure at the inlet of compressor stations is kept constant when pipeline operating condition changes. Such pipeline operating conditions include varying ambient temperature and varying natural gas volumetric flow rate. The performance behavior of the pipeline corresponding to the change of operating conditions has been successfully simulated. The introduced pipeline performance simulation approach is generic and can be applied to different pipeline-compressor systems.
Reacting Pressurized Spray Combustor Dynamics: Part 2 — High Speed Planar Measurements
Authors: Chterev I. , Rock N. , Ek H. , Smith T. , Emerson B. , Noble D. R. , Mayhew E. , Lee T. , Jiang N. , Roy S. , Seitzman J. M. , Lieuwen T.
Published: September 2016

This paper describes stereo-PIV, OH-PLIF and fuel-PLIE (planar laser induced emission) measurements in a pressurized, liquid fueled, swirl combustor. Data were obtained at globally fuel lean conditions, combustor pressures of 2–5 bar, and an inlet air temperature of 450 K. The experiments were performed to characterize the flowfield, heat release and fuel spray distribution. Several challenges are associated with OH-PLIF in pressurized, liquid fuel systems at sustained high repetition rates. For example, in addition to the significantly lower pulse energies of high repetition rate systems relative to low repetition rate ones, the ultraviolet laser used to excite OH also causes the fuel to emit, with the brighter liquid fuel signal overlapping the OH fluorescence spectrum. To overcome these challenges, two intensified high-speed cameras were used to maximize signal separation during data collection and perform signal subtraction in post-processing. The first camera used narrow band spectral filtering, and the intensifier was gated to miss much of the slower decaying fuel signal. As a result, it satisfactorily captures the OH fluorescence along with some of the stronger fuel fluorescence signal. The second camera detected primarily fuel emission with the intensifier gate delayed to capture the tail of the longer-lived fuel phosphorescence, and a long-pass spectral filter capturing all the fuel emission. This paper presents illustrative results showing the instantaneous flow field, flame position as indicated by OH-PLIF, and spray distribution from the fuel PLIE. Multiple flame topologies are observed — specifically, flames stabilized in the outer shear layer occur for all the cases studied, but inner shear layer stabilized flames are also seen in the higher pressure cases.
Influence of Unsteady Wakes on the Secondary Flows in the Linear T106 Turbine Cascade
Authors: Kirik Ilker , Niehuis Reinhard
Published: September 2016

The present work extends previous investigations on the secondary flows around a steady and unsteady base flow to detailed time-averaged and time-resolved flow field measurements up- and downstream of the cascade.

As a representative of modern low pressure turbine rotors of moderate aerodynamic loading, the LPT cascade T106 with parallel sidewalls was chosen for these investigations. Previous investigations have shown that the intensity of secondary flows in the endwall region within a first test set-up was fairly low due to the thin endwall boundary layer at the inlet of the cascade which impeded to study the influence of periodically incoming wakes on the temporal development of the secondary flow field. For that reason a new test-up was built providing a thicker inlet boundary. Measurements have been performed in the High-Speed Cascade Wind Tunnel of the University of the Federal Armed Forces Munich under realistic Mach and Reynolds numbers. In order to simulate real turbomachinery situtations, a wake generator is installed generating temporally representative wakes in the inlet plane of the cascade by a moving bar system.

The inlet conditions were determined using a hot wire and a Pitot probe. Detailed measurements of the three-dimensional flow field were carried out downstream of the cascade with a triple hot wire probe, a conventional five hole pressure probe, and a dynamic pressure probe equipped with a single Kulite sensor. All measurements were performed with and without moving bars. Based on previous investigations, a pitch of the moving bars of 40 mm and a circumferential speed of 20 m/s was chosen as the configuration with the highest influence on the secondary flow field.

It is shown that the intended increase of the inlet boundary layer was achieved by putting plates on top of each other in the inlet plane endwalls. This leads to more pronounced secondary flow parameters in the spanwise distribution of the pitchwise averaged secondary flow angle (Δβ2,sec) and the secondary losses (ζ2,sec).
Influences of Target Surface Roughness on Impingement Jet Array Heat Transfer: Part 1 — Effects of Roughness Pattern, Roughness Height, and Reynolds Number
Authors: Buzzard W. , Ren Z. , Ligrani P. , Nakamata C. , Ueguchi S.
Published: September 2016

The present investigation considers the effects of special roughness patterns on impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement jet array cooling. This investigation utilizes various sizes, distributions, shapes, and patterns of surface roughness elements for impingement cooling augmentation. The surface roughness shape considered here is rectangle, in combination with larger rectangular pins. Combinations of small rectangle roughness and large pins are considered together, along with arrays of small rectangular roughness alone. Tests are performed at impingement jet Reynolds numbers of 900, 1500, 5000, and 11000. Local and overall impingement cooling performance depends upon the pattern, distribution, arrangement, and height of the roughness elements, as well as upon the jet Reynolds number. Depending upon the magnitude of jet Reynolds number, different behavior and trends are observed for the small rectangle roughness and large pins together, compared with arrays of small rectangular roughness alone. Overall, results demonstrate the remarkable ability of target surface roughness to produce increased surface heat transfer augmentation levels of impingement jet array cooling, relative to target surfaces which are smooth.
Reynolds Correction in Centrifugal Compressors: Theory and Experimental Validation of a Revised Correlation
Authors: Scarbolo Luca , Belardini Elisabetta , Bellobuono Ernani Fulvio , Rubino Dante Tommaso , Tapinassi Libero
Published: September 2016

Centrifugal Compressors are designed for customer specified (contractual) operating conditions but are often tested in similitude conditions at different pressures, different speeds and with different gases (i.e. ASME-PTC10 Type 2 Test). Test performances are scaled to contractual conditions adopting the fan-law that do not account for efficiency modifications due to Reynolds effects. In many cases these efficiency variations are not negligible and thus a correction is required. According to experimental results, the well-known and widely adopted ASME-PTC10 Reynolds correction has shown some limitations: despite having provided valuable results, its simplified models seem not accurate enough for the current quality requirements. In particular when applied to a dataset available within GE Oil & Gas the Reynolds correction underestimated the efficiency variation. In the recent years GE Oil&Gas has performed a wide experimental campaign for the assessment of the Reynolds effect for both single stage model test and full-size machines at low and intermediate pressures. Also the impact of different levels of surface finishing has been investigated for both rotating and stationary parts. Based on this activity and on the available specific literature a proprietary calibrated model, based on a revised formulation of the Simon et al. [1] and ICAAMC [2] correlation, is proposed. The accuracy of the approach is evaluated in comparison with the current ASME-PTC10 [3], the ICAAMC [2] correlation, and the Casey et al. [4] and Pelz et al. [5] approaches. In particular two applications are shown. First single stage centrifugal compressor model test have been tested at different Reynolds numbers and with different levels of roughness. Then the performances of a full-size compressor prototype (specifically instrumented for this scope) have been measured at various pressure levels. The proprietary correlation and the other available correlations are compared on the basis of these extensive results, yielding to a direct comparison of the methods accuracy on the prediction of actual industrial Centrifugal Compressors stages and full-size machine performances.
A Design Method for Globally Curvature-Smooth Centrifugal Compressor Blades
Authors: Bi Qingzhen , Chen Hua , Tong Ding , Lu Yaoan
Published: September 2016

Blade surface curvature has an important effect on the pressure distribution over the surface as well as the quality of airfoil machining. In a previous publication [1], the authors proposed a curvature smoothing method that can generate blade sections with smooth curvature. In this earlier work, however, the spanwise smoothing was not considered. In fact, smoothing of individual blade sections often results in a blade with unsmooth curvature in the spanwise direction. In this paper, the spanwise smoothing is tackled. The implications of curvature smoothness in the spanwise direction are examined first, and the difficulty in obtaining smooth curvature in both the streamwise and spanwise directions by direct, gradient based global optimisation is described. Two methods are put forward to overcome this difficulty. The first method prescribes two analytic functions for the blade pressure and suction surfaces respectively after the streamwise smoothing. The second method implements a bi-directional global optimisation technique. Both the methods are described and their applications to a turbocharger centrifugal compressor are presented. The results show that both the streamwise and spanwise curvature smoothness can be achieved by the two methods. CFD and FEA simulations further demonstrate the benefits of the bi-directional global optimisation technique.
Experimental Study of Heat Transfer in a Converging Duct With Ribs
Authors: Xu Wei-jiang , Zhang Pei-yao , Ma Xiao-fei , Zhu Hui-ren , Zhang Li
Published: September 2016

Heat transfer characteristics on the inner surface of a converging duct with ribs are investigated by conducting transient heat transfer experiments using thermochromic liquid crystals. In particular, features associated with the smooth duct are addressed as reference. The parameters studied are: the non-dimensional rib pitch (p/w = 10, 20, 50, p is the rib pitch, w is the rib width), the rib blockage ratio (e/H = 10%, 20%, e is the rib height, H is the channel height) and the inlet Reynolds number Re (Re = 6000∼20000). The results are presented on the top wall and its center line. Due to the converging shape of channel, the value of Nu/Nu0 increases downstream the channel, especially near the side wall. The effects of these parameters are: Firstly, the heat transfer improves with the increasing rib height whose influence decreases with the rise of Re number. Secondly, the value of Nu/Nu0 rises firstly, reaching its maximum at p/w = 20, and then declines with an increasing rib pitch. Thirdly, the value of Nu/Nu0 rises firstly and decreases afterwards with the Re number, as the Re number is within the range of Re≤12000.
Structural Deflection’s Impact in Turbine Stator Well Heat Transfer
Authors: Pohl Julien , Thompson Harvey , Guijarro Valencia Antonio , López Juste Gregorio , Fico Vincenzo , Clayton Gary A.
Published: September 2016

In the most evolved designs, it is common practice to expose engine components to main annulus air temperatures exceeding the thermal material limit in order to increase the overall performance and to minimise the engine specific fuel consumption (SFC). To prevent overheating of the materials and thus the reduction of the component life, an internal flow system is required to cool the critical engine parts and to protect them. This paper shows a practical application and extension of the methodology developed during the five year research programme MAGPI. Extensive use was made of FEA (solids) and CFD (fluid) modelling techniques to understand the thermo-mechanical behaviour of a dedicated turbine stator well cavity rig, due to the interaction of cooling air supply with the main annulus. Previous work based on the same rig showed difficulties in matching predictions to thermocouple measurements near the rim seal gap. In this investigation, two different types of turbine stator well geometries were analysed, where further use was made of existing measurements of hot running seal clearances in the rig. The structural deflections were applied to the existing models to evaluate the impact in flow interactions and heat transfer. Additionally to the already evaluated test cases without net ingestion, cases simulating engine deterioration with net ingestion were validated against the available test data, also taking into account cold and hot running seal clearances. 3D CFD simulations were conducted using the commercial solver FLUENT coupled to the in-house FEA tool SC03 to validate against available test data of the dedicated rig.
Impulse Mistuning of Blades and Vanes
Authors: Hartung Andreas , Retze Ulrich , Hackenberg Hans-Peter
Published: September 2016

Impulse mistuning is an alternative approach for the reduction of vibration stresses of blades and vanes. In contrast to most other approaches it is not a direct energy dissipation approach but a mistuning based one. However, the approach is not aimed at making use of the geometrical mistuning of the structure (e.g. a blade or a vane stage). Mistuners, specially designed small bodies are placed at specific locations inside of the component e.g. of a blade or of a vane. They do not directly dissipate enough energy to cause relevant damping like a friction or friction-impact damper, because of the small mass involved, but rather mistune the eigen frequencies of the structure using impulses (impacts). As a result, the structure absorbs less energy at the original resonance and hence answers with lower vibration amplitude. In fact, impulse mistuning is a special case of absorption — the so called Targeted Energy Transfer (TET) with “Vibro-Impact Nonlinear Energy Sinks” (VI-NES) — with very small impact mass involved and thus a negligible role of dissipation while experiencing a significant amount of absorption. The energy will be transferred (or “pumped”) to other resonances, sometimes outside of the primary resonance crossing and partially dissipated. We use the names “impulse mistuning” or “mistuners” instead of TET or VI-NES because (in our opinion) it better describes the physics of this special kind of absorption. In the paper, the design and validation of two impulse mistuning systems, for a blade stage and a vane cluster of a lower power turbine, are presented.
Selection and Development of the World’s Most Power-Dense Gas Turbine Module for the New Korean Frigate
Authors: Lim Sangpil , Harvey Adam
Published: September 2016

The MT30 marine gas turbine has been developed specifically for 21st century naval propulsion using modern techniques and methods. Design and development of the MT30 began in 1999 and has since been qualified for naval service following extensive testing. Since then the engine has rapidly been adopted by progressive navies, in both its mechanical and electrical power generation configuration.

The Lockheed Martin Littoral Combat Ship (LCS) is one of a new class of United States Navy (USN) fast combatants which has been at sea for more than six years and is powered by the MT30. A combined MT30-driven generator was selected for the new USN DDG1000 Zumwalt class of destroyer and has also been successfully installed into the Royal Navy’s Queen Elizabeth Class aircraft carrier. Most recently, the MT30 Compact Package has been selected to power the Royal Navy’s Type 26 Global Combat Ship which will be built by BAE Systems.

The MT30 Compact Package has been designed with the aim of powering modern warship programmes, with the result that it is currently the World’s most power dense in-service marine gas turbine. This is an important factor in naval propulsion where delivering a high power output in a compact space is essential.

In addition to the programmes stated above, the MT30 Compact Package was selected for the new Republic of Korea Navy’s (RoKN) frigate programme with a single-GT CODLOG hybrid arrangement consisting of propulsion motors and a Diesel-electric system.

As a result, Rolls Royce was selected by the RoKN to deliver the MT30 Gas Turbine Unit and, from a preliminary Rolls-Royce compact package design, the engine and machinery division of Hyundai Heavy Industry (HHI-EMD) has developed the Compact Package for the New Korea Frigate. The MT30 GT was delivered to the HHI-EMD facility in 2014 with the surrounding Compact Package built at HHI-EMD before onward delivery to Daewoo Shipbuilding and Marine Engineering (DSME) where construction of the first frigate will take place.

This paper provides the rationale for selection of the MT30 Compact Package for the New Korea Frigate Programme and also describes the development of the MT30 Compact Package; aspects of the design process, construction of the Compact Package and the factory acceptance test conducted at the HHI-EMD facility.
Effects of Turbulent Boundary Conditions on the Prediction of the Secondary Flow Field in a Linear Compressor Cascade
Authors: Busse Peter , Krug Andreas , Lange Martin , Vogeler Konrad , Mailach Ronald
Published: September 2016

For most technical applications, simulations of the Reynolds-Averaged-Navier-Stokes equations has become a standard analysis tool, since it brings a good compromise between computational accuracy and costs. However, turbulence models have to be implemented to close the system of differential equations. To study the effects of turbulent boundary conditions on the prediction of the secondary flow field in a linear compressor cascade with tip clearance, the state of the art RANS solver TRACE in conjunction with Wilcox’ k-ω-turbulence model is used. Besides a stagnation point anomaly prevention, no turbomachinery specific modifications of the turbulence model are applied. Transition is not considered. The current investigations focus on the influence of the imposed turbulent inlet quantities (k0, ω0) on the development of the wall-bounded flow in the cascade. The turbulent kinetic energy k is basically described as a function of the turbulence intensity level measured in an equivalent experimental setup. For the reconstruction of turbulent fluctuations beyond measuring accessibility in the vicinity of the wall, an analytical approach is proposed and validated with DNS data of turbulent flat plate and fully developed channel flows. To identify the influence of different dissipation rates ω on the characteristics of the secondary flow, the free stream turbulent length scale LtFS is varied in four steps ranging from 0.2 up to 5 millimeters. Additionally, the effects of different span-wise length scale distributions across the inlet flow boundary layer are considered.
Impact of Swirling Flow Structure on Shear Layer Vorticity Fluctuation Mechanisms
Authors: Mathews Benjamin , Hansford Samuel , O’Connor Jacqueline
Published: September 2016

Vorticity fluctuations have been identified as an important coupling mechanism during velocity-coupled combustion instability in swirl-stabilized flames. Acoustic oscillations in the combustor can cause all components of vorticity to oscillate, particularly the cross-stream, or azimuthal, vorticity that is excited in shear layer roll-up, and streamwise, or axial, vorticity that is excited during swirl fluctuations. These fluctuations can be induced by longitudinal acoustic fluctuations that oscillate across the swirler and dump plane upstream of the flame. While these fluctuations have been identified in a number of configurations, the sensitivity of this mechanism to flow configuration and boundary conditions has not been studied parametrically. In this study, we investigate the impact of time-averaged swirl level, confinement, and forcing frequency and amplitude on vorticity fluctuation dynamics in the azimuthal direction of a non-reacting swirling jet. The goal of this work is to better understand the dependence of vorticity fluctuations on these parameters as well as the vorticity conversion processes that occur in the flow. We have shown that vorticity fluctuation levels vary with time-averaged swirl number, particularly in the presence of a self-excited precessing vortex core, which dampens most acoustically-driven motion. Additionally, variations in forcing frequency excite flow response in different portions of the flow, particularly for different swirl numbers. Finally, confinement drastically changes the flow topology and unforced dynamics, resulting in significantly different response to forcing and generation of vortical fluctuations.
Thermo-Economic Analysis of a Photovoltaic-Fuel Cell Hybrid System With Energy Storage for CHP Production in Household Sector
Authors: Ancona M. A. , Bianchi M. , De Pascale A. , Melino F. , Peretto A. , Branchini L.
Published: September 2016

The penetration of renewable sources, particularly wind and solar, into the grid has been increasing in recent years. As a consequence, there have been serious concerns over reliable and safety operation of power systems. One possible solution, to improve grid integrity, is to integrate energy storage devices into power system network: storing energy produced in periods of low demand to later use, ensuring full exploitation of intermittent available sources. Focusing on photovoltaic energy system, energy storage is needed with the purpose of ensuring continuous power flow to minimize or to neglect electrical grid supply. A comprehensive study on a hybrid micro-CHP system based on photovoltaic panels using hydrogen as energy storage technologies has been performed. This study examines the feasibility of replacing electricity provided by the grid with a hybrid system to meet household demand. This paper is a part of an experimental and a theoretical study which is currently under development at University of Bologna where a test facility is under construction for the experimental characterization of a small scale cogenerative power system. This paper presents the theoretical results of a hybrid system performance simulations made of a photovoltaic array an electrolyzer with a H2 tank and a Proton Exchange Membrane fuel cell stack designed to satisfy typical household electrical demand. The performance of this system have been evaluated by the use of a calculation code, in-house developed by the University of Bologna. Results of the carried out parametric investigations identify photovoltaic and fuel cell systems’ optimal size in order to minimize the purchasing of electrical energy from the grid. Future activities will be the tuning of the software with the experimental results, in order to realize a code able to define the correct size of each sub-system, once the load profile of the utility is known or estimated.
Design of an Intermediate Turbine Duct Downstream of a High Pressure Turbine
Authors: Hou Chaoshan , Wu Hu
Published: September 2016

The flow leaving the high pressure turbine should be guided to the low pressure turbine by an annular diffuser, which is called as the intermediate turbine duct. Flow separation, which would result in secondary flow and cause great flow loss, is easily induced by the negative pressure gradient inside the duct. And such non-uniform flow field would also affect the inlet conditions of the low pressure turbine, resulting in efficiency reduction of low pressure turbine. Highly efficient intermediate turbine duct cannot be designed without considering the effects of the rotating row of the high pressure turbine.

A typical turbine model is simulated by commercial computational fluid dynamics method. This model is used to validate the accuracy and reliability of the selected numerical method by comparing the numerical results with the experimental results. An intermediate turbine duct with eight struts has been designed initially downstream of an existing high pressure turbine. On the basis of the original design, the main purpose of this paper is to reduce the net aerodynamic load on the strut surface and thus minimize the overall duct loss. Full three-dimensional inverse method is applied to the redesign of the struts. It is revealed that the duct with new struts after inverse design has an improved performance as compared with the original one.
Design of Dynamic Tracking Filter for Model Based Diagnosis of Gas Turbine Engine
Authors: Liu Yongwen , Liu Yunsheng
Published: September 2016

There exist many approaches for gas turbine engine condition monitoring and fault diagnosis. Among them, gas path analysis depends on the relations between deviations of performance parameters and deviations of measurements, such as pressure, temperature, at some positions in the flow path. In the first author’s previous study, a dynamic tracking filter is combined with a nonlinear gas turbine model to form a fault diagnosis system. The dynamic tracking filter is composed with multiple negative feedback control loops in which the residuals between model outputs and measurements are driven to zero by adjusting the performance parameters. In the present study, an interaction analysis technique, named the Relative Gain Analysis (RGA), is introduced to design more convincing and formal tracking filter for a heavy-duty gas turbine diagnostic problem. The basic concept of the RGA method is introduced in this paper with a simple blending example. Then a gas turbine model built using the Simscape language and environment from the MathWorks Co. is presented. The effects of secondary air system on the performance of compressor and turbine are considered in this gas turbine model. The linear influence coefficient matrix for four performance parameters and four measurement parameters is obtained from the steady state simulation with proper disturbance of performance parameters. Then the relative gain matrix (RGM) is obtained from matrix operation. To evaluate the pairing rule proposed in the RGA method, four tracking loops are built up to form a tracking filter for the four performance parameters selected. Deviations of performance parameters are implanted into the gas turbine model by adjusting the scaling factors of performance maps; and then simulation results are taken as measurements needed for the tracking filter to run. Tracking results of performance parameters in different cases are given to show the tracking capability for isolated performance deviations and concurrent performance deviations.
Numerical Analysis of an Alternate Stall in a Radial Vaned Diffuser
Authors: Benichou E. , Trébinjac I.
Published: September 2016

The flow structure in the radial diffuser of a centrifugal compressor is analyzed from steady and unsteady Reynolds-Averaged Navier Stokes (RANS) simulations performed at one rotation speed for which two stable operating ranges separated by an unstable zone have been experimentally experienced.

Below a given mass flow rate, close to the peak efficiency point, phase-lagged single-passage simulations do not converge properly anymore. A low frequency appears in the CFD, which cannot be associated with any physical phenomenon. The computational domain is then extended, so that several passages of both the impeller and the diffuser are taken into account. At intermediate mass flow rates, an unstable operating range exists and simulations cannot converge properly either. Nevertheless, if the compressor is further throttled, another stable operating range is obtained at low mass flow rates. The flow structure in that stable operating range is rather unusual: an internal periodicity emerges inside the radial diffuser, involving a two-channel flow pattern.

This two-channel flow pattern is found to be stable and fixed in time. Moreover, the phase shift between two adjacent channel pairs happens to be constant. This indicates that a new space – time periodicity is established at low mass flow rates, which involves groups of two passages in the radial diffuser. It is confirmed thanks to a new phase-lagged simulation including one impeller passage and two diffuser passages which shows a good convergence and which gives the same results, both in terms of performance and flow physics.
Experimental and Numerical Investigation of Unsteady Structures Within the Rim Seal Cavity in the Presence of Purge Mass Flow
Authors: Town Jason , Averbach Michael , Camci Cengiz
Published: September 2016

Flow within the space between the rotor and stator of a turbine disk, an area referred to as the rim seal cavity, develops azimuthal velocity component from the rotor disk. The fluid within develops unsteady structures that move at a fraction of the rotor speed. A measurement strategy is developed to measure the number of unsteady structures and the rotational speed at which they are moving in the rim seal cavity of an experimental turbine research rig. Data manipulation was developed to extract the speed and the numbers of structures present using two fast response aerodynamic probes measuring static pressure on the surface of the stator side rim seal cavity. A computational study is completed to compare measured results to a transient Unsteady Reynolds Averaged Navier-Stokes (URANS). The computational simulation domain consists of 8 vanes and 10 blades (the full test facility consisted of 29 vanes and 36 blades), carefully picked to reduce error caused by blade vane pitch mismatch and to allow for the structures to develop correctly, and the rim seal cavity to measure the speed and number of the structures. The experimental results found 15 structures moving at 77.5% of the rotor speed, computational results are based on the size of the domain and guidance from the experimental results found 14.5 structures are moving at 81.7% rotor speed. The agreement represents the first known test of its kind and the first known agreement between computational and experimental work performed in the large scale and rotating turbine research facility AFTRF at the Pennsylvania State University.
Heat Transfer and Pressure Loss Measurements in Additively Manufactured Wavy Microchannels
Authors: Kirsch Kathryn L. , Thole Karen A.
Published: September 2016

The role of additive manufacturing for the hot section components of gas turbine engines grows ever larger as progress in the industry continues. The opportunity for the heat transfer community is to exploit the use of additive manufacturing in developing nontraditional cooling schemes to be built directly into components. This study investigates the heat transfer and pressure loss performance of additively manufactured wavy channels. Three coupons, each containing channels of a specified wavelength (length of one wave period), were manufactured via Direct Metal Laser Sintering and tested at a range of Reynolds numbers. Results show that short wavelength channels yield high pressure losses, without corresponding increases in heat transfer, due to the flow structure promoted by the waves. Longer wavelength channels offer less of a penalty in pressure drop with good heat transfer performance.
Development of a Fatigue Life Assessment and Prediction Framework for a Bimetallic-Welded Thick-Wall Component of a Steam Turbine
Authors: Shen M.-H. Herman , Akanda Sajedur , Liu Xia , Wang Peng
Published: September 2016

In this investigation, we have applied an integrated experimental-analytical framework for fatigue life assessment and prediction of a thick-wall component of a high-pressure (HP) steam turbine. Emphasis is placed on the development of an effective experimental and analytical procedure for life characterization on the basis of low cycle and high cycle fatigue (LCF/HCF) in order to improve the safety, reliability, and affordability of real world steam turbine operations. Stress-control constant amplitude fully reversed fatigue tests were performed in room temperature and 500°C to serve two purposes: (a) to obtain experimental stress-life (S-N) curves and (b) to assess the values of the parameters of the energy-based framework to predict the fatigue life. The experimental and the predicted S-N curves are compared with each other in case of both the room and the elevated temperature to examine the soundness of the present energy-based model to predict fatigue life. The present lifing model was found to be able to predict both the room and elevated temperature LCF/HCF life of the thick-wall component with excellent accuracy. Furthermore, the elevated temperature fatigue life is found to be lower than the room temperature fatigue life due to the lower fatigue toughness at elevated temperature.
Effects of Double Wall Cooling Configuration and Conditions on Performance of Full Coverage Effusion Cooling
Authors: Rogers Nathan , Ren Zhong , Buzzard Warren , Sweeney Brian , Tinker Nathan , Ligrani Phil , Hollingsworth Keith , Liberatore Fred , Patel Rajeshriben , Moon Hee-Koo
Published: September 2016

Experimental results are presented for a double wall cooling arrangement which simulates a portion of a combustor liner of a gas turbine engine. The results are collected using a new experimental facility designed to test full coverage film cooling and impingement cooling effectiveness using either cross flow, impingement, or a combination of both to supply the film cooling flow. The present experiment primarily deals with cross flow supplied full coverage film cooling for a sparse film cooling hole array that has not been previously tested. Data are provided for turbulent film cooling, contraction ratio of 1, blowing ratios ranging from 2.7 to 7.5, coolant Reynolds numbers based on film cooling hole diameter of about 5,000–20,000, and mainstream temperature step during transient tests of 14 °C. The film cooling hole array consists of a film cooling hole diameter of 6.4 mm with non-dimensional streamwise (X/de) and spanwise (Y/de) film cooling hole spacing of 15 and 4, respectively. The film cooling holes are streamwise inclined at an angle of 25 degrees with respect to the test plate surface and have adjacent streamwise rows staggered with respect to each other. Data illustrating the effects of blowing ratio on adiabatic film cooling effectiveness and heat transfer coefficient are presented. For the arrangement and conditions considered, heat transfer coefficients generally increase with streamwise development, and increase with increasing blowing ratio. The adiabatic film cooling effectiveness is determined from measurements of adiabatic wall temperature, coolant stagnation temperature, and mainstream recovery temperature. The adiabatic wall temperature and adiabatic film cooling effectiveness generally decrease and increase, respectively, with streamwise position, and generally decrease and increase, respectively, as blowing ratio becomes larger.
Formation Process of Water Film and Performance Effect on Compressor Stage
Authors: Zhang Hai , Tian Xiaojiang , Pan Xiaojun , Zhou Jie , Zheng Qun
Published: September 2016

In process of wet compression, gas turbine engine will ingest a certain amount of water, which can influence the overall performance of the engine. This phenomenon is particularly significant in the cleaning process of industrial gas turbine and water injection of aero-engine. When the quantity of water ingestion is quite large, the performance of gas turbine will appear deterioration and may lead to flameout, power reduce or even shutdown of the engine, causing accidents. Water droplets will be accumulated on the blade surface where water films could be formed on pressure surface in the wet compression process. The effects of water film on gas turbine engines are aerodynamic, thermodynamic and mechanical. The above-mentioned effects occur simultaneously and be affected by each other. Considering the above effects and the fact that they are time dependent, there are few gas turbine performance researches, which take into account the water film phenomenon.

This study is a new research of investigating theoretically the water film effects on a gas turbine performance. It focuses on the aerodynamic and thermodynamic effects of the phenomenon on the compressor stage. The computation of water film thickness, which frequently be formed on the surface of compressor blade, its movement and extra torque demand, are provided by a simulation model of the code. Considering the change in blade’s profile and the thickness feature of the water film, the compressor stage’s performance deterioration is analyzed. In addition to this, movement and the formation of the water film on a compressor stage are simulated and analyzed by using unsteady numerical methods under different water injecting conditions in this paper. The movement characteristics of water droplets in compressor passage are investigated to understand the flow mechanisms responsible for water film formation process. The forming and the tearing process of water film on blade surface are analyzed at different injection conditions. For simulating the real situation, The maximum quantity of injected water can reach 12%.

The results indicate that continuity and region of the water film on the blade surface will be developed with the increment of droplet size and injection rate. It is also found that the flow losses near blade surface increases with the tearing process of water film due to the increment of surface roughness.