bluuebunny/crossref_metadata_2025 huggingface dataset:
Wind Power Plant and Power-to-Gas System Coupled With Natural Gas Grid Infrastructure: Techno-Economic Optimization of Operation
Authors: Guandalini Giulio , Campanari Stefano
Published: August 2015

In this work, the coupled operation of a wind park and a hydrogen power-to-gas (P2G) technology is addressed in order to improve dispatchability and profitability of the wind resource. Among many available storage technologies currently under development, the P2G was chosen because of its large storage capacity and fast response. In particular, oppositely to traditional storage approaches, the solution that considers the direct injection of hydrogen in the natural gas grid infrastructure could reduce investment costs and improve the renewable fraction of fuels. Economic optimal operation and installed P2G power are calculated solving a mixed-integer linear programming (MILP) problem. Performances of the main component (electrolysis unit) are modeled, including additional costs for start-up and partial load operation losses. Technical limits on both electric and natural gas grids are also included. Some assumptions on the economic rules governing the electric grid unbalance are made, according to possible evolutions of the regulation framework focused on EU and Italian system. The simulation is performed on hourly basis, assuming realistic forecasted and real power production profiles from an actual mid-size (30 MW) wind power plant, together with prices of electricity markets and gas production. A sensitivity analysis is also performed varying both economic and technical parameters. Whereas in some scenarios the technology is profitable with the current investment costs, a reduction of electrolyzer costs down to expected mid-term targets would lead to a stronger competitiveness in each scenario. The study aims at identifying the influence of main technical and economic parameters on the effectiveness of the power-to-gas technology. Results show how the proposed solution allows better exploiting the wind resource, although the net electricity production can decrease due to the production of hydrogen, suggesting the possibility to substantially oversize the wind park in order to cover the same electric load.
Performance Testing of the 100 kW Shell-and-Tube Heat Exchanger Using Low-Finned Tubes With Supercritical Carbon Dioxide on the Shell Side and Water on the Tube Side
Authors: Fourspring Patrick M. , Nehrbauer Joseph P.
Published: August 2015

BMPC completed thermal-hydraulic testing of a shell-and-tube heat exchanger with low-finned tubes for transferring heat from supercritical carbon dioxide (S-CO2) on the shell side to water on the tube side.

The measured performance of the shell-and-tube heat exchanger using low-finned tubes on the shell side showed that it achieved the specified thermal-hydraulic performance.

The analytical approach to determine the performance of a shell-and-tube heat exchanger with low-finned tubes and S-CO2 on the shell side compares well with the measured performance of the heat exchanger.

The additional heat transfer area provided by the low-finned tubes remained fully effective — even with reduced flow velocity and the supercritical fluid near its critical point or a pseudo-critical temperature1. Over a range of limiting flow conditions of the supercritical fluid, the thickness of the thermal boundary layer remained sufficiently thin to allow the low-finned tubes to remain fully effective. This result supports (but is not sufficient to prove) the general guidance to limit the estimated thickness of the thermal boundary layer to the fin height and twice the fin spacing to ensure the additional heat transfer area provided by the low-finned tubes remains effective.
Aerodynamic Characterization of Conical Diffusers for Radial Turboexpanders Under Realistic Inlet Conditions
Authors: Insinna Massimiliano , Salvadori Simone , Cagnarini Claudia , Mariotti Gabriele
Published: August 2015

Radial inflow expander units are increasingly employed in both oil and gas upstream and downstream markets for energy saving purposes. While prominent attention is given to the performance of the expansion wheel, the downstream diffuser is scarcely covered in literature. In modern expanders, the gas entering the diffuser is typically high-speed, non-uniformly distributed from hub to shroud. Recovery factor and pressure loss coefficient are then affected by both the inlet gas conditions and the geometry of the system, including shaft end and divergence angle of the diffuser.

In the present work, the application of computational methodologies to expander diffusers is initially assessed. A sensitivity analysis is then performed with respect to the inlet flow conditions and the diffuser shape. Trends of variation of recovery factor and loss coefficient are provided as a function of selected geometrical parameters and boundary conditions. It is shown that, starting from a non-optimized diffuser, an overall machine efficiency gain can be achieved. That performance improvement can be appreciated by the current market of expanders as a non-negligible competitive advantage.
The Influence the Number of Holes on Effusion Cooling Effectiveness for an X/D of 4.7
Authors: Oguntade H. I. , Andrews G. E. , Burns A. D. , Ingham D. B. , Pourkashanian M.
Published: August 2015

Conjugate heat transfer CFD predictions were made, using ANSYS FLUENT, of the effects of the number of holes per square metre of surface area, N, on effusion overall cooling effectiveness for square array holes with a pitch to diameter ratio, X/D, or 4.7. Nimonic 75 effusion walls 6.35mm thick were modelled at 770K crossflow at 27 m/s with 300K coolant. The computational procedures include the use of a gas tracer to predict the adiabatic film cooling, which was not measured in the hot wall experimental results, as well as the overall cooling effectiveness. The computational results of the overall cooling effectiveness differed from the experimental data by 2–12%, depending on N and G. The results showed that increasing N reduced the amount of coolant air mass flow, necessary to achieve a target overall cooling effectiveness of 0.7, by 50% for 26,910/m2 compared with 9688/m2. With a very low G of 0.18 kg/sm2 the highest N of 26,910/m2 was predicted to have an overall cooling effectiveness of 0.7 compared with 0.55 kg/sm2 for the lowest number of holes, 4306/m2. This is one of the lowest published coolant air mass flows for the design overall cooling effectiveness of 0.7, which gives acceptable metal temperatures under engine combustor conditions.
CHT/CFD Predictions of Impingement Cooling With Four Sided Flow Exit
Authors: El-Jummah Abubakar M. , Andrews Gordon E. , Staggs John E. J.
Published: August 2015

Impingement/effusion cooling has no cross-flow in the impingement gap if all the coolant flow through the impingement wall passes through the effusion wall. In this investigation, the impingement part of the impingement/effusion cooling was investigated by minimising the cross-flow using a four sided exit impingement cooling geometry. The impingement geometry investigated was a square array of 10 by 10 impingement holes with a pitch to diameter, X/D, of 11, hole density, n, of 4306m−2, and gap to diameter ratio, Z/D, of 7.25 for coolant mass flux G of 0.2–1.1 kg/sm2bar. The impingement target and jet walls were modelled as Nimonic-75 as used in the experimental work used for validation of the computational methods. Conjugate heat transfer (CHT) computational fluid dynamics (CFD) was used with ANSYS Fluent code. The measured impingement target wall pressure loss ΔP/P% and target wall surface averaged heat transfer coefficient together with the heat transfer to the impingement jet wall were all predicted in agreement with the measurements, within the measured error bars. The predicted surface distributions of Nu and turbulent kinetic energy (TKE) were compared with predictions for impingement single sided exit flow and the impingement/effusion approach (target) walls. This showed that the reduced crossflow with the four sided exit gave higher surface averaged heat transfer. However, comparison with the impingement/effusion wall heat transfer, for the same impingement wall geometry, showed that the removal of coolant through the effusion wall reduced the recirculating flow in the impingement gap and this reduced the heat transfer to the impingement jet wall, but increased it to the target effusion wall.
Process Integration for Large Front-Stage Blades Mechanical Integrity Design
Authors: Hecker Philipp , Cerutti Stefano , Lötzerich Michael
Published: August 2015

The mechanical integrity design of front stages for heavy duty gas turbines is by definition a challenging task. Several design criteria need to be fulfilled, reaching from static stress requirements over sufficient cyclic lifetime to a defined dynamic behavior of the component. This design task becomes even more challenging in case the size of the engine increases.

To satisfy the need for designing larger front stage blades, an automated and integrated design tool suite for Mechanical Integrity analysis tasks has been developed. This paper introduces the specific steps of the mechanical assessment in the early concept phase of new designs. The overall process relies on advanced numerical methods, namely Design of Experiments, numerical optimization and probabilistic techniques, which are combined into a single package. The delineated procedure represents an incremental approach, which contrasts to the integrated and partially multi-disciplinary optimization processes which are typically described in literature.

The benefits of the incremental method can be identified with regard to computational time, enhancement of interfaces and feedback loops with neighboring disciplines. By applying the process outlined in this paper, a new generation of frontstage blades could be developed with further improved mechanical properties and reduced development efforts.
An Experimental and Numerical Assessment of Airfoil Polars for Use in Darrieus Wind Turbines: Part 1 — Flow Curvature Effects
Authors: Bianchini Alessandro , Balduzzi Francesco , Rainbird John M. , Peiro Joaquim , Graham J. Michael R. , Ferrara Giovanni , Ferrari Lorenzo
Published: August 2015

A better comprehension of the aerodynamic behavior of rotating airfoils in Darrieus Vertical-axis wind turbines (VAWTs) is crucial both for the further development of these machines and for improvement of conventional design tools based on zero or one-dimensional models (e.g. BEM models).

When smaller rotors are designed with high chord-to-radius (c/R) ratios so as not to limit the blade Reynolds number, the performance of turbine blades has been suggested to be heavily impacted by a virtual camber effect imparted on the blades by the curvilinear flow they experience.

To assess the impact of this virtual camber effect on blade and turbine performance, a standard NACA0018 airfoil and a NACA0018 conformally transformed such that the airfoil’s chord line follows the arc of a circle, where the ratio of the airfoil’s chord to the circle’s radius is 0.25 were considered. For both airfoils, wind tunnel tests were carried out to assess their aerodynamic lift and drag coefficients for Reynolds numbers of interest for Darrieus VAWTs.

Unsteady CFD calculations have been then carried out to obtain curvilinear flow performance data for the same airfoils mounted on a Darrieus rotor with a c/R of 0.25. The blade incidence and lift and drag forces were extracted from the CFD output using a novel incidence angle deduction technique.

According to virtual camber theory, the transformed airfoil in this curvilinear flow should be equivalent to the NACA0018 in rectilinear flow, while the NACA0018 should be equivalent to the inverted transformed airfoil in rectilinear flow.

Comparisons were made between these airfoil pairings using the CFD output and the rectilinear performance data obtained from the wind tunnel tests and XFoil output in the form of pressure distributions and lift and drag polars.

Blade torque coefficients and turbine power coefficient are also presented for the CFD VAWT using both blade profiles.
Organic Rankine Cycle System for Effective Energy Recovery in Offshore Applications: A Parametric Investigation With Different Power Rating Gas Turbines
Authors: Bhargava R. K. , Bianchi M. , Branchini L. , De Pascale A. , Orlandini V.
Published: August 2015

A comprehensive and systematic evaluation of the bottoming Organic Rankine Cycle based energy recovery system, considering a wide spectrum of gas turbines with power ratings commonly used in the offshore applications, has been conducted in this paper to demonstrate the potential benefits of this technology. In this study, emphasis is given on the thermodynamic performance of the energy system by evaluating incremental electric power recovery, thermal energy recovery and carbon emissions savings. Effects of an intermediate heat transfer fluid and the utilization of a recuperator for waste energy recovery in the Organic Rankine Cycle on the key performance indicators of the energy system are evaluated. In addition to discussing advantages and limitations of the considered configurations of the bottoming Organic Rankine cycle, it is shown that by using the proposed configurations, a significant amount of additional electric power can be produced which could be used to prevent part-load operations of gas turbines resulting in fuel savings, increased gas turbine’s components life, reduced maintenance cost, and reduced CO2 emissions — a win-win proposition for the offshore projects.
Robust Optimal Design of a Gas Turbine Cogeneration Plant Under Uncertain Energy Demands and Costs
Authors: Yokoyama Ryohei , Ohkura Masashi , Wakui Tetsuya
Published: August 2015

In designing energy supply systems, designers should consider that energy demands and costs as parameters have some uncertainties, evaluate the robustness in system performances against the uncertainties, and design the systems rationally to heighten the robustness. A robust optimal design method of energy supply systems under only uncertain energy demands was revised so that it can be applied to systems with complex configurations and large numbers of periods for variations in energy demands. In addition, a method of comparing performances of two energy supply systems under only uncertain energy demands was proposed by utilizing a part of the revised robust optimal design method. In this paper, the revised robust optimal design method as well as the proposed performance comparison method are extended so that they can be applied to the robust optimal design and the performance comparison of energy supply systems under not only uncertain energy demands but also uncertain energy costs. Through a case study on a gas turbine cogeneration system for district energy supply, the validity and effectiveness of the extended optimal design method and features of the robust optimal design are clarified. In addition, the gas turbine cogeneration system is compared with a conventional energy supply system using the extended performance comparison method.
An Experimental Investigation of the Performance Impact of Swirl on a Turbine Exhaust Diffuser/Collector for a Series of Diffuser Strut Geometries
Authors: Xue Song , Guillot Stephen , Ng Wing F. , Fleming Jon , Lowe K. Todd , Samal Nihar , Stang Ulrich E.
Published: August 2015

A comprehensive experimental investigation was initiated to evaluate the aerodynamic performance of a gas turbine exhaust diffuser/collector for various strut geometries over a range of inlet angle. The test was conducted on a 1/12th scale rig developed for rapid and accurate evaluation of multiple test configurations. The facility was designed to run continuously at an inlet Mach number of 0.40 and an inlet hydraulic diameter-based Reynolds number of 3.4×105. Multi-hole pneumatic pressure probes and surface oil flow visualization were deployed to ascertain the effects of inlet flow angle and strut geometry. Initial baseline diffuser-only tests with struts omitted showed a weakly increasing trend in pressure recovery with increasing swirl, peaking at 14° before rapidly dropping. Tests on profiled struts showed a similar trend with reduced recovery across the range of swirl and increased recovery drop beyond the peak.

Subsequent tests for a full diffuser/collector configuration with profiled struts revealed a rising trend at lower swirl when compared to diffuser-only results, albeit with a reduction in recovery. When tested without struts, the addition of the collector to the diffuser not only reduced the pressure recovery at all angles but also resulted in a shift of the overall characteristic to a peak recovery at a lower value of swirl. The increased operation range associated with the implementation of struts in the full configuration is attributed to the de-swirling effects of the profiled struts. In this case the decreased swirl reduces the flow asymmetry responsible for the reduction in pressure recovery attributed to the formation of a localized reverse-flow vortex near the bottom of the collector. This research indicates that strut setting angle and, to a lesser extent, strut shape can be optimized to provide peak engine performance over a wide range of operation.
Theoretical Model to Determine Effect of Ingress on Turbine Discs
Authors: Mear L. Isobel , Owen J. Michael , Lock Gary D.
Published: August 2015

Sealing air is used in gas turbines to reduce the amount of hot gas that is ingested through the rim seals into the wheel-space between the turbine disc and its adjacent stationary casing. The sealing air attaches itself to the rotor, creating a buffering effect that reduces the amount of ingested fluid that can reach the surface of the rotor. In this paper, a theoretical model is developed, and this shows that the maximum buffering effect occurs at a critical flow rate of sealing air, the value of which depends on the seal geometry. The model, which requires two empirical constants, is validated using experimental data, obtained from infra-red (IR) temperature measurements, which are presented in a separate paper. There is good agreement between the adiabatic effectiveness of the rotor estimated from the model and that obtained from the IR measurements. Of particular interest to designers is that significant ingress can enter the wheel-space before its effect is sensed by the rotor.
Design of an Improved Turbine Rim-Seal
Authors: Scobie James A. , Teuber Roy , Li Yan Sheng , Sangan Carl M. , Wilson Michael , Lock Gary D.
Published: August 2015

Rim seals are fitted in gas turbines at the periphery of the wheel-space formed between rotor discs and their adjacent casings. These seals, also called platform overlap seals, reduce the ingress of hot gases which can limit the life of highly-stressed components in the engine. This paper describes the development of a new, patented rim-seal concept showing improved performance relative to a reference engine design, using URANS computations of a turbine stage at engine conditions. The CFD study was limited to a small number of purge-flow rates due to computational time and cost, and the computations were validated experimentally at a lower rotational Reynolds number and in conditions under incompressible flow. The new rim seal features a stator-side angel wing and two buffer cavities between outer and inner seals: the angel-wing promotes a counter-rotating vortex to reduce the effect of the ingress on the stator; the two buffer cavities are shown to attenuate the circumferential pressure asymmetries of the fluid ingested from the mainstream annulus. Rotor disc pumping is exploited to reduce the sealing flow rate required to prevent ingress, with the rotor boundary layer also providing protective cooling. Measurements of gas concentration and swirl ratio, determined from static and total pressure, were used to assess the performance of the new seal concept relative to a bench-mark generic seal. The radial variation of concentration through the seal was measured in the experiments and these data captured the improvements due to the intermediate buffer cavities predicted by the CFD. This successful design approach is a potent combination of insight provided by computation, and the flexibility and expedience provided by experiment.
Development of an Advanced Automated Knowledge Based Combustor Preliminary Design Process Suitable for Low NOx Combustion Systems Optimization
Authors: Gessel Maxim , Pfitzner Michael , Eggels Ruud
Published: August 2015

Within the current combustor design process, the combustor performance and sizing is mainly estimated using Prelim Design Tools, which are based on empirical correlations. In order to investigate these preliminary designs in more detail, the application of CFD within the preliminary combustor design process has steadily increased. However, the generation of CFD solutions is a time consuming process, since it requires adapted CAD models and the generation of meshes before the actual CFD computations can be performed. Moreover, it has to be assured that the meshes are suitable for the computational code, which may require several iterations within the grid generation process. Next the manual setting of the boundary conditions for CFD is also prone to errors and the post-processing of the CFD results is generally time consuming. Therefore, an advanced approach of an automated preliminary combustor design process has been developed within the 7th framework of the European research project IMPACT-AE, based on the knowledge obtained in the 6th framework of the European research project INTELLECT D.M. The processes developed are based on improved and robust knowledge-based-engineering tools for modern low NOx combustor geometries.

The advanced approach comprises a KBE preliminary design tool with improved Rolls-Royce in-house design rules for modern low NOx high efficiency combustors. It is based on fully featured 3-D parametric combustor models, including the pre-diffuser, the injector, the flame tube and the casing parts. An unstructured automatable meshing-tool CFS BOXERMesh is used to generate high quality meshes. Subsequent CFD analyses are performed using an unstructured Rolls-Royce in-house combustion CFD code PRECISE-UNS and the post-processing is performed using the open source tool ParaView. The choice of these tools is based on their ability to be fully automated using appropriate scripts and information. To create a strong linkage between these tools a KBE interface-tool and a database were implemented. These tools manage the individual processes fully automatically, including e.g. the transfer of geometry parameters to the CAD models; the gathering of the combustion chamber dependent boundary conditions and numerical parameters for the CFD analysis; or the generation of tool-internal automation scripts, using interface-tool input and database information.

Several grid refinement studies were performed to define an automated mesh refinement strategy, using scaled cell sizes for each combustor feature. Furthermore, a mixing port diameter scaling and a detailed post-processing procedure are described.
Design of a High-Speed Rotating Test Rig for Adaptive Seal Systems
Authors: Beermann Laura S. , Höfler Corina , Bauer Hans-Jörg
Published: August 2015

Gas turbine engines are subject to increased performance and improved efficiency, which leads to rising core temperatures with additional cooling needs. Reducing the parasitic leakage in the secondary flow system is important to meet the challenging requirements. New seal designs have to be tested and optimized at engine like conditions, like high pressure of up to 9 bar and surface speed of up to 280 m/s as well as an adjusted flow field. Flexible seal designs are an innovative approach to reduce leakage mass flows significantly. Axial and radial movements during transient operating conditions can be compensated easily, thus allowing a smaller gap width and minimizing rub and heat load.

This paper describes the design and construction of a new rotating test rig facility. To the knowledge of the authors, this is the only test rig with an adjustable gap width and flow field in a high pressure and speed range. The facility is capable of up to 8 bar differential pressure across the seal and up to 4 bar back pressure. The high revolution engine facilitates a surface speed of up to 280 m/s. A traversable casing allows a quick change of the gap width during operation and simulates radial and axial rotor/stator movements in the engine. The seal movement as well as the resulting gap width are measured during operation to fully understand the seal behavior.

An important feature of the new test rig is the continuously adjustable pre-swirl system. It has been designed to cover the different flow conditions in the real engine. Therefore, a RANS parameter study of the pre-swirl chamber has been conducted, which shows the adjustability of different pre-swirl ratios for constant and changing inlet mass flows.
1D Adaptive Measurement Grid for Improved Pneumatic Probe Measurements
Authors: Bartsch Christian , Hölle Magnus , Jeschke Peter , Metzler Timo
Published: August 2015

The subject of this paper is a flow-adaptive measurement grid developed for pneumatic probe measurements in turbomachinery flows. The performance of the algorithm is demonstrated by a circumferential traverse at a constant radial position with a pneumatic 5-hole probe in an annular cascade wind tunnel. Compared to a conventional equidistant measurement grid, the algorithm automatically computes the amount of measurement points needed for a high resolution of the pressure distribution in steady flow fields. The algorithm is fully automated and approximates the pressure distribution of a preliminary transient measurement very accurately. Even though the spacing of the computed measurement points differs significantly from an equidistant grid, post-processing corrections related to the probe head geometry can still be applied. Accompanying a redistribution of the measurement points is a reduction in the overall points needed for the measurement. The commonly encountered problem of data oversampling is therefore avoided. Compared to a conventional equidistant measurement grid, the adaptive grid showed a significant reduction in the overall measurement points and a reduction in the duration of the measurement — while maintaining the accuracy in the computation of flow parameters.

The purpose of this paper is to demonstrate the performance of an automatic detection of measurement points so that valuable measurement time can be saved without a loss in quality of the obtained data.
Unsteady Wet-Steam Flows Through Low Pressure Turbine Final Three Stages Considering Blade Number
Authors: Miyake Satoshi , Miyazawa Hironori , Yamamoto Satoru , Sasao Yasuhiro , Momma Kazuhiro , Ooyama Hiroharu , Miyawaki Toshihiro
Published: August 2015

Unsteady three-dimensional wet-steam flows through stator–rotor blade rows in the final three stages of a low-pressure steam turbine, taking the blade number into consideration, are numerically investigated. In ASME Turbo Expo 2014, we presented the numerical results of the unsteady flow assuming the same blade number. Here, this previous study is extended to flow simulations using the real blade number. The flows under three flow conditions, with and without condensation and considering the same and real blade numbers are simulated, and the numerical results are compared with each other and with the experimental results. Finally, the effect of the blade number on unsteady wet-steam flows in real low-pressure steam turbines is discussed.
Thermodynamics and Fluid Mechanics of a Closed Blade Cascade Wind Tunnel for Organic Vapors
Authors: Reinker Felix , Hasselmann Karsten , aus der Wiesche Stefan , Kenig Eugeny Y.
Published: August 2015

The Organic Rankine Cycle (ORC) offers great potential for waste heat recovery and use of low-temperature sources for power generation. However, the ORC thermal efficiency is limited by the relatively low temperature level, and it is, therefore, of major importance to design ORC components with high efficiencies and minimized losses. The use of organic fluids creates new challenges for turbine design, due to dense gas behavior and the low speed of sound. The design and performance predictions for steam and gas turbines have been initially based on measurements and numerical simulations of flow through two-dimensional cascades of blades. In case of ORC turbines and related fluids, such an approach requires the use of a specially designed closed cascade wind tunnel. In this contribution the design and process engineering of a continuous running wind tunnel for organic vapors is presented. The wind tunnel can be operated with heavy weight organic working fluids within a broad range of pressure and temperature levels. For this reason, the use of classical design rules for atmospheric wind tunnels is limited. The thermodynamic cycle process in the closed wind tunnel is modeled and simulated by means of a professional power plant analysis tool, including a database for the ORC fluid properties under consideration. The wind tunnel is designed as a pressure vessel system and this leads to significant challenges particular for the employed wide angle diffuser, settling chamber, and nozzle. Detailed computational fluid dynamics analyses (CFD) were performed in order to optimize the important wind tunnel sections.
On the Numerical Evaluation of Tone Noise Emissions Generated by a Turbine Stage: An In-Depth Comparison Among Different Computational Methods
Authors: Pinelli Lorenzo , Poli Francesco , Arnone Andrea , Guérin Sébastien , Holewa Axel , Fernández Aparicio José Ramón , Puente Ricardo , Torzo Davide , Favre Christophe , Gaetani Paolo , Persico Giacomo
Published: August 2015

Within the European research project RECORD (Research on Core Noise Reduction) the tone noise emissions of a high-pressure turbine stage have been numerically evaluated by six different academic and industrial partners. The turbine stage geometry and operating conditions match an HPT test rig located at Politecnico di Milano (Italy).

Since the constant demand for quieter and greener propulsion systems has led to the development of several numerical aeroacoustic codes, this common benchmark represents an important chance to compare the performance of each approach.

In this paper, the tone noise results of three distinct categories of numerical solvers (unsteady RANS, harmonic balance and time-linearized approaches) are compared. For the tone noise simulations, all the partners used non-reflecting boundary conditions at the domain inlet and outlet in order to avoid spurious reflections.

Moreover, the acoustic modeshapes in the turbine duct were evaluated with different level of complexity by the various partners and different post-processing techniques were employed to extract the acoustic waves from the unsteady solutions.

The result comparisons for the blade passing frequency have shown a good agreement (within 4 dB) among the partners in terms of PWL values. Also the acoustic eigenmodes (radial shapes of the pressure waves) and the eigenvalues (axial wave numbers) agree well among the different simulations. A wide range of acoustic results are presented and discussed in the paper.
Efficient Combustion Noise Simulation of a Gas Turbine Model Combustor Based on Stochastic Sound Sources
Authors: Grimm Felix , Ewert Roland , Dierke Jürgen , Reichling Gilles , Noll Berthold , Aigner Manfred
Published: August 2015

A gas turbine model combustor is simulated with a hybrid, stochastic and particle-based method for combustion noise prediction with full 3D sound source modeling and sound propagation. Alongside, an incompressible LES simulation of the burner is considered for the investigation of the performance of the hybrid approach. The highly efficient time-domain method consists of a stochastic sound source reconstruction algorithm, the Fast Random Particle Method (FRPM) and sound wave propagation via Linearized Euler Equations (LEEs). In the context of this work, the method is adapted and tested for Combustion Noise (CN) prediction. Monopole sound sources are reconstructed by using an estimation of turbulence statistics from reacting CFD-RANS simulations. First, steady state and unsteady CFD calculations of flow field and combustion of the model combustor are evaluated and compared to experimental results. Two equation modeling for turbulence and the EDM (Eddy Dissipation Model) with FRC (Finite Rate Chemistry) for combustion are employed. In a second step, the acoustics simulation setup for the model combustor is introduced. Selected results are presented and FRPM-CN pressure spectra are compared to experimental levels.
Comparison of Conjugate Heat Transfer Analysis of Flat Plate Film Cooling Arrays Against Experimental Data
Authors: Humber William , Ni Ron-Ho , Johnson Jamie , Clark John , King Paul
Published: August 2015

Conjugate heat transfer (CHT) simulations were conducted for five film-cooled flat plates designed to model the pressure side of the High Impact Technologies Research Turbine First Vane (HIT RT1V). The numerical results of the CHT analysis were compared against experimental data. The five test cases consist of one baseline geometry and four different cooling hole geometries applied to a film-cooling hole arrangement that was optimized to achieve a more uniform cooling effectiveness. This optimized film-cooling hole configuration was designed by coupling a genetic algorithm with a Navier-Stokes fluid solver, using source terms to model film holes, starting from a baseline cooling configuration. All five plates were manufactured, and surface temperature measurements were taken using infrared thermography while the plates were exposed to flow conditions similar to the pressure side of the HIT RT1V. CHT simulations were carried out using unstructured meshes for both fluid and solid with all film holes fully resolved. Comparison of experimental data and simulations shows a consistent trend between the optimized configurations as well as correct predictions of the flow characteristics of each hole geometry although the absolute temperatures are underpredicted by the CHT. Both experimental measurements and CHT predictions show the optimized geometry with mini-trenched-shaped holes to give the best cooling effectiveness.
Assessment of the Indirect Combustion Noise Generated in a Transonic High-Pressure Turbine Stage
Authors: Papadogiannis Dimitrios , Duchaine Florent , Gicquel Laurent , Wang Gaofeng , Moreau Stéphane , Nicoud Franck
Published: August 2015

Indirect combustion noise, generated by the acceleration and distortion of entropy waves through the turbine stages, has been shown to be the dominant noise source of gas turbines at low-frequencies and to impact the thermoacoustic behavior of the combustor. In the present work, indirect combustion noise generation is evaluated in the realistic, fully 3D transonic high-pressure turbine stage MT1 using Large-Eddy Simulations (LES). An analysis of the basic flow and the different turbine noise generation mechanisms is performed for two configurations: one with a steady inflow and a second with a pulsed inlet, where a plane entropy wave train at a given frequency is injected before propagating across the stage generating indirect noise. The noise is evaluated through the Dynamic Mode Decomposition of the flow field. It is compared with previous 2D simulations of a similar stator/rotor configuration, as well as with the compact theory of Cumpsty and Marble. Results show that the upstream propagating entropy noise is reduced due to the choked turbine nozzle guide vane. Downstream acoustic waves are found to be of similar strength to the 2D case, highlighting the potential impact of indirect combustion noise on the overall noise signature of the engine.
Novel Gas Turbine Blade Leading Edge Cooling Configuration Using Advanced Double Swirl Chambers
Authors: Kusterer Karsten , Lin Gang , Sugimoto Takao , Bohn Dieter , Tanaka Ryozo , Kazari Masahide
Published: August 2015

The Double Swirl Chambers (DSC) cooling technology, which has been introduced and developed by the authors, has the potential to be a promising cooling technology for further increase of gas turbine inlet temperature and thus improvement of the thermal efficiency. The DSC cooling technology establishes a significant enhancement of the local internal heat transfer due to the generation of two anti-rotating swirls. The reattachment of the swirl flows with the maximum velocity at the center of the chamber leads to a linear impingement effect on the internal surface of the blade leading edge nearby the stagnation line of gas turbine blade. Due to the existence of two swirls both the suction side and the pressure side of the blade near the leading edge can be very well cooled. In this work, several advanced DSC cooling configurations with a row of cooling air inlet holes have been investigated. Compared with the standard DSC cooling configuration the advanced ones have more suitable cross section profiles, which enables better accordance with the real blade leading edge profile. At the same time these configurations are also easier to be manufactured in a real blade. These new cooling configurations have been numerically compared with the state of the art leading edge impingement cooling configuration. With the same configuration of cooling air supply and boundary conditions the advanced DSC cooling presents 22–26% improvement of overall heat transfer and 3–4% lower total pressure drop. Along the stagnation line the new cooling configuration can generate twice the heat flux than the standard impingement cooling channel. The influence of spent flow in the impinging position and impingement heat transfer value is in the new cooling configurations much smaller, which leads to a much more uniform heat transfer distribution along the chamber axial direction.
Unsteady Aerodynamic Interaction in a Closely-Coupled Turbine Consistent With Contra-Rotation
Authors: Ooten Michael K. , Anthony Richard J. , Lethander Andrew T. , Clark John P.
Published: August 2015

The focus of the study presented here was to investigate the interaction between the blade and downstream vane of the stage-and-one-half transonic turbine via CFD analysis and experimental data. A Reynolds-Averaged Navier-Stokes (RANS) flow solver with the two-equation Wilcox 1998 k-ω turbulence model was used as the numerical analysis tool for comparison for all of the experiments conducted. The rigor and fidelity of both the experimental tests and numerical analysis methods were built through two- and three-dimensional steady-state comparisons, leading to three-dimensional time-accurate comparisons. This was accomplished by first testing the midspan and quarter-tip two-dimensional geometries of the blade in a linear transonic cascade. The effects of varying the incidence angle and pressure ratio on the pressure distribution were captured both numerically and experimentally. This was used during the stage-and-one-half post-test analysis to confirm that the target corrected speed and pressure ratio were achieved. Then, in a full annulus facility, the first vane itself was tested in order to characterize the flowfield exiting the vane that would be provided to the blade row during the rotating experiments. Finally, the full stage-and-one-half transonic turbine was tested in the full annulus cascade with a data resolution not seen in any studies to date. A rigorous convergence study was conducted in order to sufficiently model the flow physics of the transonic turbine. The surface pressure traces and the Discrete Fourier Transforms thereof were compared to the numerical analysis. Shock trajectories were tracked through the use of two-point space-time correlation coefficients. Very good agreement was seen when comparing the numerical analysis to the experimental data. The unsteady interaction between the blade and downstream vane was well captured in the numerical analysis.
Experimental Study on the Friction Contact Between a Labyrinth Seal Fin and a Honeycomb Stator
Authors: Pychynski Tim , Höfler Corina , Bauer Hans-Jörg
Published: August 2015

This paper presents results from an extensive experimental study on the rubbing behavior of labyrinth seal fins and a honeycomb liner. The objective of the present work is to improve the understanding of the rub behavior of labyrinth seals by quantifying the effects and interactions of sliding speed, incursion rate, seal geometry and seal fin rub position on the honeycomb liner. In order to reduce the complexity of the friction system studied, this work focuses on the contact between a single seal fin and a single metal foil. The metal foil is positioned in parallel to the seal fin to represent contact between the seal fin and the honeycomb double foil section. A special test rig was set up enabling the radial incursion of a metal foil into a rotating labyrinth seal fin at a defined incursion rate of up to 0.65 mm/s and friction velocities up to 165 m/s. Contact forces, friction temperatures and wear were measured during or after the rub event. In total, 88 rub tests including several repetitions of each rub scenario have been conducted to obtain a solid data base.

The results show that rub forces are mainly a function of the rub parameters incursion rate and friction velocity. Overall, the results demonstrate a strong interaction between contact forces, friction temperature and wear behavior of the rub system. The presented tests confirm basic qualitative observations regarding blade rubbing provided in literature.
The Low Reduced Frequency Limit of Vibrating Airfoils: Part II — Numerical Experiments
Authors: Vega Almudena , Corral Roque
Published: August 2015

This paper studies the unsteady aerodynamics of vibrating airfoils in the low reduced frequency regime with special emphasis in its impact on the scaling of the work per cycle curves using an asymptotic approach (Part I) and numerical simulations. A perturbation analysis of the linearized Navier-Stokes equations at low reduced frequency is presented and some conclusions are drawn (Part I of the corresponding paper). The first important result is that the loading of the airfoil plays an essential role in the trends of the phase and modulus of the unsteady pressure field caused by the vibration of the airfoil. For lightly loaded airfoils the unsteady pressure and the influence coefficients scale linearly with the reduced frequency whereas the phase departs from π/2 and changes linearly with the reduced frequency. As a consequence the work-per-cycle is proportional to the reduced frequency for any inter-blade phase angle and it is independent of its sign. For highly loaded airfoils the unsteady pressure modulus is fairly constant exhibiting only a small correction with the reduced frequency, while the phase departs from zero varies linearly with it. In this case only the mean value of the work-per-cycle scales linearly with the reduced frequency. This behavior is independent of the geometry of the airfoil and in first approximation of the mode-shape. For symmetric cascades the work-per-cycle scales linearly with the reduced frequency irrespectively of whether the airfoil is loaded or not. Simulations using a frequency domain linearized Navier-Stokes solver have been carried out on a low-pressure turbine airfoil section, the NACA0012 and NACA65 profiles and a flat plate operating at different flow conditions to show the generality and correctness of the analytical conclusions. Both the traveling-wave and influence coefficient formulations of the problem are used in combination to increase the understanding and explore the nature of the unsteady pressure perturbations.
Cross Wind Influence on Noise Emission and Computed Vibrational Noise of an Axial Fan
Authors: Heinemann Till , Münsterjohann Sven , Zenger Florian , Becker Stefan
Published: August 2015

The total noise emissions of two commercial axial fans were measured in a semi-anechoic fan test rig in comparison. The total sound pressure levels and the respective spectra were found to change with the fans’ operating points. Increasing fan flow rates lowered the total acoustic pressure, with a broadband shift towards higher frequencies, keeping perceived (A-weighted) sound pressure levels approximately constant over a wide range of operating points. In a second step, Laser Scanning Vibrometry measurements of the fan blades’ axial motion were conducted in comparison inside a wind tunnel fan test rig. Rotating blade surface vibration data was used as sole input to a Ffowcs Williams and Hawkings algorithm, to estimate noise emission from vibration. The computed noise from surface vibration was found to be hardly affected by the change of fan flow rate.

In the application of an axial fan subject to natural wind or induced cross flow at its inlet, the flow field and possible noise emission of the fan changes. Microphone measurements of the cross flow influence inside a semi-anechoic wind tunnel revealed increasing broadband noise with ambient flow field velocity, and an amplification of the sound at the blade passing frequency harmonics. Similar excitations of the blade passing frequency harmonics under cross flow influence were also found in sound pressure spectra computations based on the Laser Scanning Vibrometry measurement data captured in the wind tunnel fan test rig. Blade vibration is considered to contribute to the low frequency tonal noise emission of axial fans operating under cross flow conditions.
A Method for Axial Compressor Start-Up Assessment
Authors: Astrua Pio , Puppo Enrico , Cecchi Stefano , Silingardi Andrea
Published: August 2015

This paper presents a method to assess compressor mass flow, pressure line and stability, including blow-off lines behavior, during a heavy duty gas turbine (GT) start up. A Company proprietary compressor mean line analysis 1-dimensional code (C1D) has been calibrated on 3D RANS calculations and matched with a 1D Fanno model to simulate the compressor behavior during GT start-up; discharge compressor pressure and secondary air system boundary conditions are provided by filed test data. C1D is based on correlations tuned with available CFD and experimental data; within the present work the code has been validated with experimental data at low mechanical speed too, so that it can be used in such applications where conventional CFD analyses are most likely to fail. In this paper C1D is used to analyze the compressor start-up characteristic from idle to full speed no load operation. Pressure rise along the compressor and blow-off line mass flow are compared and validated throughout a field test campaign. Finally the method developed is applied to an evolutionary compressor in order to analyze how the stage-wise load distribution varies with mechanical speed and blow-off mass flow.