bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Numerical Investigation on the Effect of Pressure On Micromix Hydrogen Combustion
Authors: Kroniger Daniel , Horikawa Atsushi , Funke Harald H.-W. , Pfaeffle Franziska , Kishimoto Tsuyoshi , Okada Koichi
Published: September 2021

The micromix (MMX) combustion concept is a DLN gas turbine combustion technology designed for high hydrogen content fuels. Multiple non-premixed miniaturized flames based on jet in cross-flow (JICF) are inherently safe against flashback and ensure a stable operation in various operative conditions.

The objective of this paper is to investigate the influence of pressure on the micromix flame with focus on the flame initiation point and the NOx emissions. A numerical model based on a steady RANS approach and the Complex Chemistry model with relevant reactions of the GRI 3.0 mechanism is used to predict the reactive flow and NOx emissions at various pressure conditions. Regarding the turbulence-chemical interaction, the Laminar Flame Concept (LFC) and the Eddy Dissipation Concept (EDC) are compared. The numerical results are validated against experimental results that have been acquired at a high pressure test facility for industrial can-type gas turbine combustors with regard to flame initiation and NOx emissions.

The numerical approach is adequate to predict the flame initiation point and NOx emission trends. Interestingly, the flame shifts its initiation point during the pressure increase in upstream direction, whereby the flame attachment shifts from anchoring behind a downstream located bluff body towards anchoring directly at the hydrogen jet. The LFC predicts this change and the NOx emissions more accurately than the EDC. The resulting NOx correlation regarding the pressure is similar to a non-premixed type combustion configuration.
Design and Testing of an Internally-Cooled Radial Turbine With High Tip Speed
Authors: Musgrove Grant O. , Smith January , Smith Ellen , White Steve
Published: September 2021

Radial impellers are not internally-cooled because of the manufacturing challenge. The conventional manufacturing method for internally-cooled components is an investment cast process using a ceramic core to create internal passages. This approach has been developed for axial gas turbines for the past few decades and is a low-risk manufacturing approach for single blade castings. However, conventional manufacturing methods are difficult to apply to a radial impeller in a cost-effective manner. For example, the entire impeller (blades and the hub) are typically manufactured from a single piece of material. Therefore, if one blade is poorly cast, the entire impeller must be thrown away.

To overcome the complexity and reduce production risk, additive manufacturing can be used to build internally-cooled radial impellers. Additive manufacturing is a growing area and gaining operational experience is required to confidently build complex parts, such as a radial impeller with small, internal passages. In this paper, additive manufacturing is used to avoid the challenges of conventionally manufacturing. Multiple iterations of the internal cooling design are examined to illustrate lessons learned. Flow and heat transfer tests are used to verify the impeller cooling design. Material properties are discussed to verify that the impeller can withstand high rotational stresses.
Accurate Interpolation of the Dependency of Modal Properties on the Rotation Speed for the Transient Response Analysis of Bladed Disks
Authors: Tong Jing , Zang Chaoping , Petrov E. P.
Published: September 2021

During fast gas-turbine engine acceleration and deceleration the transient vibration effects in bladed disk vibration become significant and the transient response has to be calculated.

In this paper an effective method is developed for efficient calculations of the transient vibration response for mistuned bladed disks under varying rotation speeds. The method uses the large-scale finite element modelling of the bladed disks allowing the accurate description of the dynamic properties of the mistuned bladed disks.

The effects of the varying rotation speed on the natural frequencies and mode shapes of a mistuned bladed disk and its effects on the amplitude and the spectral composition of the loading are considered. The dependency of the modal characteristics on the rotation speed are based on the evaluation of these characteristics at reference points followed by the interpolation to obtain values at any rotation speed from the operating range.

A new method has been developed for the interpolation of mode shapes while preserving the orthogonality and mass-normalization of the mode shapes. The method of mode shape interpolation is elaborated for tuned and mistuned bladed disks. The accuracy and efficiency of the method is demonstrated on test examples and on analysis of transient forced response of realistic bladed discs.
A Design of Experiments Based Investigation of the Influence of Hot Cross-Flow Gas on a FLOX®-Based Single-Nozzle Liquid Burner
Authors: Izadi Saeed , Zanger Jan , Kislat Oliver , Enderle Benedict , Grimm Felix , Kutne Peter , Aigner Manfred , Kraus Cedric
Published: September 2021

Increased global demand for cleaner energy production and growing concern about using fossil fuels have urged many researchers to focus their work on developing more efficient and flexible combustion processes. In this regard, a FLOX®-based liquid fuel single-nozzle burner is investigated for use in a Capstone C30 micro gas turbine (MGT). The main advantages of FLOX®-based combustor systems are their decreased NOx emissions and increased fuel flexibility. An atmospheric test rig is set up to investigate the behavior of the FLOX®-based liquid fuel burner under the influence of the hot gas. The circulating gas in the C30 annular combustion chamber is emulated by hot cross-flow gas generated by a 20-nozzle FLOX®-based natural gas burner operated on a separate horizontal test rig. The variation and combination of the process parameters of both burners are done systematically according to Design of Experiments (DOE) as a statistical design methodology. DOE methodology is adopted rather than the conventional one-factor-at-a-time (OFAT) strategy, as DOE considers any possible interaction between the factors and reduces the number of experiments. Employing statistical design of experiments allows determining which input variables are responsible for the observed changes in the response, developing a model relating the response to the important input variables, and using this model for improving the combustor system. The results are subsequently run through the Analysis of Variance (ANOVA) in order to allow for an objective conclusion about the effect of the factors on the selected responses, which include mass flow rate (·fuel) and global air equivalence ratio (λ) of both of the liquid and natural gas burners. The hot gas cross-flow interaction with the liquid fuel burner is assessed through analyzing exhaust gas emissions and averaged flame OH*-chemiluminescence images. The models developed by the DOE method can be used to estimate the emissions and the flame geometrical properties of any other operating points that are not explicitly tested.
GT26 2006 Turbine Stage 1 Blade Reconditioning Development and Qualification at Ansaldo Repair Centre
Authors: Mela Elisa , Fignino Federico , Gabrielli Alessio , Guarnone Paola , Porro Emanuele , Kellerer Rudolf , Staempfli Matthias
Published: September 2021

The evolution of industrial gas turbines towards increased efficiency and performance requires even higher operating temperatures for the engines. In order to remain competitive in the market, OEM companies continuously need to develop maintenance programs and repair technologies able to extend the life of these components as much as possible.

The repair technology improvement is fundamental to reduce scrap rates and maintenance costs to be competitive on the market.

The Ansaldo Repair Centre answers to this market demand by providing advanced and competitive repair techniques and an increasing broad repair portfolio to its customers.

This paper describes the steps and approach to determine the repair process of GT26 LPT Blade 1 in order to allow the component to run another service interval. The base material status and the indication found after service was used as the foundation for a development of a dedicated repair sequence from stripping, to suitable heat treatments, to enhanced repair technique to recoating of the blade.

Particular attention was paid to the most damaged area, for which a particular welding procedure including an optimized filler material has been applied for the rebuilding of the tip and platform zones as well as for the restoration of the unique tip closing features.
Jet Impingement Heat Transfer Enhancement With Different Crossflow Diverter Shapes
Authors: He Juan , Deng Qinghua , Feng Zhenping
Published: September 2021

Impingement cooling is an effective cooling structure in gas turbine blades, but the downstream heat transfer will be reduced seriously by crossflow. It has been proven that equipping a crossflow diverter in impingement channel can make jet free from crossflow and enhance the downstream heat transfer. In this paper, in order to obtain a kind of crossflow diverter with advantageous heat transfer performance, the flow and heat transfer characteristics of four crossflow diverters (Semi-Circular (SC), Semi-Rectangular (SR), Semi-Diamond (SD) and Semi-Four-pointed Star (SFS)) are compared in detail. To this end, a Baseline impingement cooling configuration is considered, in which the pitches on the streamwise and spanwise directions of impingement jets are all 6D and the distance from jet to target surface is 2D. Through detailed numerical verification, SST k-ω turbulence model is finally selected, and all simulations are performed under Reynolds number ranging from 3,500 to 14,000. It is found that the crossflow diverter can change the local jet Reynolds number distribution and effectively reduce the local mass velocity ratio of crossflow to jet. Results reveal that the crossflow diverter increases the heat transfer and inevitably increases the friction loss, but all of them can improve the comprehensive heat transfer performance over the simulated flow range. When the Reynolds number is 14,000, the best heat transfer performance can be achieved, and the comprehensive heat transfer performance parameters of SC, SR, SD and SFS cases can increase by up to 11.0%, 14.3%, 12.2% and 14.7% respectively. After determining SFS-shaped crossflow diverter with the best comprehensive heat transfer performance, the influence of its streamwise position on heat transfer and friction loss is also studied. The SFS-shaped diverter is placed at 2D, 2.5D, 3D, 3.5D and 4D from the center of adjacent upstream jet, respectively. Results show that the heat transfer and friction loss change a little when the distance increases from 2D to 3D, but the heat transfer decreases sharply and friction loss increases seriously when the distance increases from 3D to 4D.
Considerations for the Evaluation of Fouling Resistant Coatings for Centrifugal Compressors
Authors: Laney Scot
Published: September 2021

For over forty years, coatings have been used as a means to prevent the build-up of foulants on the flow passages of centrifugal compressors. In general, this has been a “One Size Fits All” solution, with most OEMs and applicators offering nearly identical coating systems, despite the fact that there are distinct differences in the types of foulant that occurs in different services. To develop new coatings, there are two options, test “on the job” or test in a laboratory setting. This paper looks at various test methods to evaluate coatings by isolating the important aspects that a good fouling resistant coating should possess, namely fouling, erosion, and corrosion resistance. Each of these will be investigated separately in a battery of easy to perform tests. To the extent possible, the tests for each aspect attempt to replicate the complex conditions that occur in a centrifugal compressor that impact that specific aspect. The fouling and corrosion tests were performed with considerations for two different types of service. To illustrate the ability of the test to evaluate various coatings, the results from three different coatings will be discussed. These test methods will also be compared to other test methods used in literature.
Preliminary Evaluation of the 24 Ft. Diameter Fan Performance In the MinWaterCSP Large Cooling Systems Test Facility
Authors: van der Spuy S. J. , Els D. N. J. , Tieghi L. , Delibra G. , Corsini A. , Louw F. G. , Zapke A. , Meyer C. J.
Published: September 2021

The MinWaterCSP project was defined with the aim of reducing the cooling system water consumption and auxiliary power consumption of concentrating solar power (CSP) plants. A full-scale, 24 ft (7.315 m) diameter model of the M-fan was subsequently installed in the Min WaterCSP cooling system test facility, located at Stellenbosch University. The test facility was equipped with an in-line torque arm and speed transducer to measure the power transferred to the fan rotor, as well as a set of rotating vane anemometers upstream of the fan rotor to measure the air volume flow rate passing through the fan. The measured results were compared to those obtained on the 1.542 m diameter ISO 5801 test facility using the fan scaling laws. The comparison showed that the fan power values correlated within +/− 7% to those of the small-scale fan, but at a 1° higher blade setting angle for the full-scale fan. To correlate the expected fan static pressure rise, a CFD analysis of the 24 ft (7.315 m) diameter fan installation was performed. The predicted fan static pressure rise values from the CFD analysis were compared to those measured on the 1.542 m ISO test facility, for the same fan. The simulation made use of an actuator disc model to represent the effect of the fan. The results showed that the predicted results for fan static pressure rise of the installed 24 ft (7.315 m) diameter fan correlated closely (smaller than 1% difference) to those of the 1.542 m diameter fan at its design flowrate but, once again, at approximately 1° higher blade setting angle.
Experimental and Numerical Study for Improved Understanding of Mixed-Convection Type of Flows in Turbine Casing Cavities During Shut-Down Regimes
Authors: Murat Oguzhan , Rosic Budimir , Tanimoto Koichi , Egami Ryo
Published: September 2021

Due to increase in the power generation from renewable sources, steam and gas turbines will be required to adapt for more flexible operations with frequent start-ups and shut-downs to provide load levelling capacity. During shut-down regimes, mixed convection takes place with natural convection dominance depending on the operating conditions in turbine cavities. Buoyant flows inside the turbine that are responsible for non-uniform cooling leading to thermal stresses and compromise clearances directly limits the operational flexibility. Computational fluid dynamics (CFD) tools are required to predict the flow field during these regimes since direct measurements are extremely difficult to conduct due to the harsh operating conditions. Natural convection with the presence of cross-flow -mixed convection has not been extensively studied to provide detailed measurements. Since the literature lacks of research on such flows with real engine representative operating conditions for CFD validation, the confidence in numerical predictions is rather inadequate.

This paper presents a novel experimental facility that has been designed and commissioned to perform very accurate unsteady temperature and flow field measurements in a simplified turbine casing geometry. The facility is capable of reproducing a wide range of Richardson, Grashof and Reynolds numbers which are representative of engine realistic operating conditions. In addition, high fidelity, wall resolved LES with dynamic Smagorinsky subgrid scale model has been performed. The flow field as well as heat transfer characteristics have been accurately captured with LES. Lastly, inadequacy of RANS for mixed type of flows has been highlighted.
DDES Numerical Investigations on Coherent Structures in Trailing-Edge Film Cooling Combined With Pressure-Side Film Hole
Authors: Xiao Xiangtao , Wang Pei , Du Qiang , Xu Qingzong , Liu Jun
Published: September 2021

The pressure-side cutback is used to design the trailing-edge film cooling. Previous studies have demonstrated the strong unsteady film mixing between the mainstream gas and the slot coolant, resulting in rapid deterioration of the film cooling effectiveness on cutback surface. The shedding vortexes formed by the clockwise and counter-clockwise structures induced by the mainstream and slot coolant shear-layer account for the strong blending. The RANS/LES hybrid turbulence model (DDES) has been proved to capture the locally unstable flows well. The flowfields and temperature of the cutback under eight blowing ratios Mslot = 0.3 ∼ 1.2 are simulated. With the increasing of blowing ratios, the counter-clockwise structures induced by the slot coolant shear-layer are strengthened to dominate the shedding vortexes gradually, which is corresponding to three kinds of coherent structures. Under low Mslot = 0.3 ∼ 0.5 dominated by clockwise structures of the mainstream, the effectiveness increases. Under middle Mslot = 0.5∼0.75 dominated by both clockwise structures of the mainstream and counter-clockwise structures of the slot coolant, the effectiveness decreases. Under high Mslot = 0.75∼1.2 dominated by counter-clockwise structures of the slot coolant, the effectiveness increases again. To weaken the blending at cutback, the pressure-side film hole with Mhole = 0.4 is arranged close to the cutback to rebuild the mainstream shear-layer. The weakened mainstream shear-layer and the assistant hitting of the hairpin vortexes from the hole injection can weaken the strength of the shedding vortexes at cutback, contributing to the improvement of the effectiveness on cutback surface under low Mslot = 0.5 and middle Mslot = 0.75. Under high Mslot = 1.0, the less influence of the hole injection on the shedding vortexes dominated by the slot coolant counter-clockwise structures accounts for slight improvement. Finally, FFT analysis is obtained for two configurations.
Numerical Investigation on the Flow Characteristics in a Cover-Plate Pre-Swirl System
Authors: Jian Menghua , Yang Xuesen , Dong Wei
Published: September 2021

This paper presents a numerical investigation on the flow characteristics in a cover-plate pre-swirl system. The Reynolds-averaged Navier-Stokes equations, coupled with the standard k-ε turbulent model, are adopted and solved. With the inlet total pressure and total temperature being constant, the influences of the temperature reduction and flow resistance by changing pressure ratios and rotational Reynolds numbers were conducted. Flow features in the pre-swirl nozzle, pre-swirl cavity, receiver hole and cover-plate cavity were summarized. The results obtained in this study indicate that the pressure ratio and rotational Reynolds number have a significant influence on the vortex structure of the pre-swirl system. As the air is accelerated by the pre-swirl nozzle, the difference of circumferential velocity between the air and the rotational domain would be reduced, and the static temperature of the air would be decreased. The pressure drop in the pre-swirl system mainly occurs in the pre-swirl nozzle and the pre-swirl cavity. In addition, with the increase of the pressure ratio, the air mass flow rate and the circumferential velocity of the air out of the nozzle increased, thereby leading to an increment in temperature reduction. Moreover, with the increasing of the rotational Reynolds number, the dimensionless mass flow rate and temperature reduction of the pre-swirl system, which are mainly determined by the flow incidence angle of cooling air at the receiver hole, will first increase to a maximum and then decrease.
Design and Testing of a Static Rig for Tesla Turbine Flow Visualization
Authors: Ferrando Marco , Caminale Michael , Reggio Federico , Silvestri Paolo
Published: September 2021

The aim of this work is to describe the design and the use of an innovative test rig for investigating the expansion of subcooled fluids inside a converging nozzle and the evolution of two-phase flows in Tesla-type turbines. The flow exiting the nozzle enters tangentially into a thin flat circular chamber and it finally is discharged in the center through a duct perpendicular to it. The experimental test rig has two nozzles placed in diametric position. This peculiar shape reproduces the geometry of a single gap between two discs of a Tesla turbine, a machine that potentially could replace the throttling valve in chillers and heat pumps to increase their COP. The study of a simple and static geometry is necessary in order to calibrate the CFD modeling of the phase change in nozzle and rotor chamber. The rig was designed and assembled by TPG of the University of Genoa in the framework of the Pump-Heat H2020 project.

Here it is used subcooled water and, in order to fully characterize the expansion conditions, the rig has been equipped with pressure sensors at the nozzle inlet and at the rig outlet. A Coriolis mass flow meter and a temperature sensor were also placed at nozzle inlet. High-resolution cameras provided and managed by Ansaldo Energia were used to look at the position and shape of the front of the fluid phase change along and around the nozzle as a function of varying pressure and temperature conditions. The tests were performed in the 2.1–5.1barG pressure range and in the 132–155°C temperature range, feeding either one or both nozzles.

Future work involves the use of different nozzle profiles, such as a convergent/divergent in order to test both subsonic and supersonic flows, and experimental analysis of pressures in the rotor chamber, aimed to optimize the geometry of nozzles and Tesla turbines in two-phase applications.
Autonomous Large Eddy Simulations Setup for Cooling Hole Shape Optimization
Authors: Agarwal Shubham , Gicquel Laurent , Duchaine Florent , Odier Nicolas , Dombard Jérôme , Bonneau Damien , Slusarz Michel
Published: September 2021

Film cooling is a common technique to manage turbine blade thermal environment. The geometry of the holes which are used to generate the cooling film is known to play a very important role on thermal performances and finding the most optimized shape involves rigorous experimental as well as numerical investigations to probe the many parameters at play. For the current study an automatic optimization tool is developed and then probed with the capability of performing hole shape optimization based on Large Eddy Simulation (LES) predictions. To do so, the particular geometry called shaped cooling hole is chosen as a baseline geometry for this optimization process. Relying on the response surface evaluation based on a reduced model approach, the use of a Design of Experiments (DOE) method allows probing a discrete set of values from the parameter space used to define the present shaped cooling hole. At first only two parameters are chosen out of the seven parameters defining the hole shape. This is followed by the automatic generation of the hole geometry, the corresponding computational domain and the associated meshes. Once the geometries and meshes are created, the numerical setup is autonomously completed for each of the cases including a first guess of the flow field to increase convergence of the simulation towards an exploitable solution. To finish, the LES fluid flow prediction is used to evaluate the discrete value of the problem response function which can then participate in the reduced model construction from which the optimization is derived.
A New Turbomachine for Clean and Sustainable Hydrocarbon Cracking
Authors: Rubini Dylan , Xu Liping , Rosic Budimir , Johannesdahl Harri
Published: September 2021

Decarbonising highly energy-intensive industrial processes is imperative if nations are to comply with anthropogenic greenhouse gas emissions targets by 2050. This is a significant challenge for high-temperature industrial processes, such as hydrocarbon cracking, and there have been limited developments thus far. The novel concept presented in this study aims to replace the radiant section of a hydrocarbon cracking plant with a novel turbo-reactor. This is one of the first major and potentially successful attempts at decarbonising the petrochemical industry. Rather than using heat from the combustion of natural gas, the novel turbo-reactor can be driven by an electric motor powered by renewable electricity. Switching the fundamental energy transfer mechanism from surface heat exchange to mechanical energy transfer significantly increases the exergy efficiency of the process. Theoretical analysis and numerical simulations show that the ultra-high aerodynamic loading rotor is able to impart substantial mechanical energy into the feedstock without excess temperature difference and temperature magnitude. A complex shockwave system then transforms the kinetic energy into internal energy over an extremely short distance. The version of the turbo-reactor developed and presented in this study uses a single rotor row, in which a multi-stage configuration is achieved regeneratively by guiding the flow through a toroidal-shaped vaneless space. This configuration leads to a reduction in reactor volume by more than two orders of magnitude compared with a conventional furnace. A significantly lower wall surface temperature, supersonic gas velocities and a shorter primary gas path enable a controlled reduction in the residence time for chemical reactions, which optimises the yield. For the same reasons, the conditions for coke deposition on the turbo-reactor surfaces are unfavourable, leading to an increase in plant availability. This study demonstrates that the mechanical work input into the feedstock can be dissipated through an intense turbulent mixing process which maintains an ideal and controlled pressure level for cracking. Numerical calculations show that the turbulence intensity increases by nearly an order of magnitude relative to that in a industrial radiant reaction tube, which can be favourable for accelerating the chemical kinetics.
Tolerance-Based Optimization of Sinking EDM for Industrial Seal Slot Manufacture
Authors: Petersen Timm , Zeis Markus , Bergs Thomas
Published: September 2021

Seal plates for turbine vanes significantly reduce gap losses and thus play a major role in increasing the efficiency of turbines. The industrial production of seal slots, which position the seal plates in the turbine vanes, is driven by the need for high productivity in combination with a reliable processing of necessary geometrical and surface integrity features. A machining technology that is able to machine hard-to-cut materials such as nickel-based alloys is electrical discharge machining. Due to its electro-thermal working principle it is able to machine materials independently from their mechanical properties even at high aspect ratios. Achievable removal and wear rates as well as the resulting surface properties strongly depend on the discharge energy. Furthermore, the discharge energy affects the working gap sizes and therefore flushing efficiencies when machining high aspect ratio cavities. This relationship is investigated taking into account various contemporary generator technologies and graphite grades from both published literature and own experimental investigations. Their effect on machining performance focusing on productivity, recast layer thickness and crack formation is quantified. Based on this data a novel empirical model for tolerance-based optimization is developed. The model is used to perform an optimization on an existing serial production and implementation has been proven successful.
Uncertainty Analysis of Film Cooling of Fan-Shaped Holes on a Stator Vane Under Realistic Inlet Conditions
Authors: Wang Hai , Wang Chun-hua , Zhu Xing-dan , Pu Jian , Lu Hai-ying , Liu Ming-hou , Wang Jian-hua
Published: September 2021

Uncertainty due to operating conditions in gas turbines can have a significant impact on film cooling performance, or even the life of hot-section components. In this study, uncertainty quantification technique is applied to investigate the influences of inlet flow parameters on film cooling of fan-shaped holes on a stator vane under realistic engine conditions. The input parameters of uncertainty models include mainstream pressure, mainstream temperature, coolant pressure and coolant temperature, and it is assumed that these parameters conform to normal distributions. Surrogate model for film cooling is established by radial basis function neural network, and the statistical characteristics of outputs are determined by Monte Carlo simulation. The quantitative analysis results show that, on pressure surface, a maximum value of 61.6% uncertainty degree of laterally averaged adiabatic cooling effectiveness (ηad,lat) locates at about 4.0 diameters of hole downstream of the coolant exit; however, the maximum uncertainty degree of ηad,lat is only 4.5% on suction surface. Furthermore, the probability density function of area-averaged cooling effectiveness is of highly left-skewed distribution on pressure surface. By sensitivity analysis, the variation of mainstream pressure has the most pronounced effect on film cooling, while the effect of mainstream temperature is unobvious.
Influence of Blade Profile Change on Gas Path Performance and Their Ontology-Based Fault Knowledge Expression
Authors: Li Yuanfu , Xi Yueyun , Chen Jinwei , Zhang Huisheng
Published: September 2021

During the operation of the gas turbine engine, the blades are prone to gas path faults such as fouling, corrosion, and erosion, or even fracture. Current research usually ignores the impact of different changes in blade profile on the gas path performance. Due to the lack of a unified description between the faulty blade and the gas path performance, it is difficult to implement the knowledge expression for the blade faults. This paper proposed the following framework to fill this gap. (1) Establish a corresponding relationship between blade profile change and gas path performance degradation based on numerical simulation. (2) Combined with ontology, case-based reasoning in knowledge expression of blade faults is investigated. The knowledge base for blade faults is constructed with ontology using the simulation results. The integration, traceability, and reuse of the simulation results are realized. (3) A case is used to verify the effectiveness of the ontology knowledge base for the faulty blade and realize the knowledge expression of blade faults. This will support the real-time diagnosis of blade faults and health management for the gas turbine engine.
Correlating Cavity Sealing Effectiveness to Time-Resolved Rim Seal Events in the Presence of Vane Trailing Edge Flow
Authors: Siroka Shawn , Monge-Concepción Iván , Berdanier Reid A. , Barringer Michael D. , Thole Karen A. , Robak Christopher
Published: September 2021

The cavity region between the rotor and stator relies on hardware seals and purge flow to discourage hot gas path air from being ingested into the unprotected wheel space. However, ingestion can occur due to a combination of disk pumping, periodic vane-blade interactions, and three-dimensional seal geometry effects. These mechanisms create flow instabilities that are detrimental to cavity seal performance under certain conditions. In this paper, a one-stage turbine operating at engine representative conditions was utilized to study the effect of steady and time-resolved under-platform cavity temperatures and pressures across a range of coolant flow rates in the presence of vane trailing edge (VTE) flow. This study correlates time-resolved pressure with time-resolved temperature to identify primary frequencies driving ingestion. At certain flow rates, the time-resolved pressures are out of phase with the temperatures, indicating ingestion. These same flow rates were found to correlate to an inflection region in the cooling effectiveness curve where the maximum amplitude of the time-varying behavior coincides with the cooling effectiveness inflection point. Using a time-accurate computational model, simulations near this inflection region illustrate ingestion of high-swirl VTE flow into the cavity region which creates a buffer in the rim seal between swirled main gas path flow and axially injected purge coolant helping to suppress the amplitude of time-resolved behavior.
Supersonic Aerodynamic Instability Characteristics of Bidirectional Porous Functionally Graded Panel
Authors: Rajidi Shashidhar Reddy , Gupta Abhay , Panda Satyajit
Published: September 2021

The objective to alleviate the detrimental effects of supersonic flutter of aerospace structures necessitates the development of advanced composite materials. Porous functionally graded materials are viable alternatives to replace the metal/alloys used for critical components. The present work investigates the supersonic flutter characteristics of hinged-hinged panel for the porosity grading across the thickness and/or along the streamwise direction. Also, the possibility to alleviate the detrimental effects is investigated through the study of influence of streamwise and spanwise curvatures. A geometrically nonlinear finite element model of panel is derived using first-order shear deformation theory while the aerodynamic pressure on panel is accounted using the first-order piston theory. The results revealed that symmetric distribution of porosity with minimum porosity at the midspan and maximum porosity at core displays the better performance. Porosity and streamwise curvature reduces critical aerodynamic pressure and enhances flutter amplitude. For higher streamwise curvatures/porosity, panel undergoes snap-through buckling resulting in complex vibrations. Whereas the spanwise curvature substantially enhance the critical dynamic pressure thereby eliminates complex oscillations and snap-through. But moderately increases the flutter amplitude and frequency beyond its critical aerodynamic pressure. At higher spanwise curvatures, the effectiveness of bidirectional grading decreases making its through-thickness grading as dominant.
Full-Scale Vibration Testing of Nozzle Guide Vanes
Authors: Macoretta Giuseppe , Monelli Bernardo Disma , Neri Paolo , Bucciarelli Federico , Checcacci Damaso , Giusti Enrico
Published: September 2021

An increasing number of turboexpanders are equipped with Nozzle Guide Vane (NGV) as the first stator stage. By varying the throat area of the first stator vane the NGV enables an additional control methodology to the line-up power output allowing higher operational flexibility and higher efficiency at partial load and partial speed. The design of this component might become critical for enabling high expander availability considering its exposure to high temperature, thermal loading, and fluid induced vibrations. This is especially true also considering that the vibration frequencies of this sub-assembly are influenced by internal clearances and by the value of the friction coefficient, which leaves a relevant margin of error when using numerical methods (such as FEM) for predicting the actual structural behavior of this component. In this paper, the design of a full-scale test bench for the determination of both friction coefficients and modal behavior of a nozzle guide vane geometry is described. The bench enables us to simulate the pre-load due to aerodynamic forces on the NGV airfoil simulating the actual working conditions of bushes and bearings.
Improving Combined Cycle Part Load Performance by Using Exhaust Gas Recirculation Through an Ejector
Authors: Sammak Majed , Ho Chi , Dawood Alaaeldin , Khalidi Abdurrahman
Published: September 2021

The gas turbine inlet air heating system has been used for improving the combined cycle heat rate at part load operation, which has a positive impact on the combined cycle profitability and fuel consumption. The paper objective was to introduce a new gas turbine inlet air heating system.

The inlet air heating system studied in this paper was exhaust gas recirculation into inlet air compressor through an ejector. The ejector motive flow was defined as the compressor bleed air from the compressor discharge section while the ejector entrainment flow was defined as the recirculated exhaust gases from the gas turbine exhaust duct.

This study was performed on generic gas turbine and combined cycle model. The selected combined cycle model was 1-on-1 (one gas turbine, one heat recovery steam generator and one steam turbine train). The heat recovery steam generator was a 3-pressure level with reheat.

The combined cycle heat rate improvement at different ejector entrainment ratio varying from 0.5 to 5 with 0.5 intervals was studied. The selected ejector area ratio was set to 25 which together with the motive to suction pressure ratio gave an entrainment ratio of 2.5. The selected ejector entrainment ratio of 2.5 was aligned with the common practice design of the ejectors. The ejector motive flow was limited to 1% of compressor inlet air flow.

Furthermore, the combined cycle heat rate improvement at different combined cycle loads were analysed. The analysis was performed on combined cycle loads from 90% to 40% load with a 10% interval and at the ambient temperatures 7°C, 15°C and 35°C.

At the ambient temperatures 7°C, 15°C and 35°C, the combined cycle heat rate improvement was measured at loads below 80%. The combined cycle heat rate improvements proved greater at lower combined cycle loads and lower ambient temperatures. The combined cycle heat rate improvement was 0.67% at the ambient temperature 15°C and 60% combined cycle load. On the other hand, the combined cycle heat rate improvement was 1.4% at 40% combined cycle load and ambient temperature 7°C.
Influence of Coolant Density on Turbine Blade Film Cooling at Transonic Cascade Flow Conditions Using the Pressure Sensitive Paint Technique
Authors: Ullah Izhar , Alsaleem Sulaiman M. , Wright Lesley M. , Shiau Chao-Cheng , Han Je-Chin
Published: September 2021

This work is an experimental study of film cooling effectiveness on a blade tip in a stationary, linear cascade. The cascade is mounted in a blowdown facility with controlled inlet and exit Mach numbers of 0.29 and 0.75, respectively. The free stream turbulence intensity is measured to be 13.5 % upstream of the blade’s leading edge. A flat tip design is studied, having a tip gap of 1.6%. The blade tip is designed to have 15 shaped film cooling holes along the near-tip pressure side (PS) surface. Fifteen vertical film cooling holes are placed on the tip near the pressure side. The cooling holes are divided into a 2-zone plenum to locally maintain the desired blowing ratios based on the external pressure field. Two coolant injection scenarios are considered by injecting coolant through the tip holes only and both tip and PS surface holes together. The blowing ratio (M) and density ratio (DR) effects are studied by testing at blowing ratios of 0.5, 1.0, and 1.5 and three density ratios of 1.0, 1.5, and 2.0. Three different foreign gases are used to create density ratio effect. Over-tip flow leakage is also studied by measuring the static pressure distributions on the blade tip using the pressure sensitive paint (PSP) measurement technique. In addition, detailed film cooling effectiveness is acquired to quantify the parametric effect of blowing ratio and density ratio on a plane tip design. Increasing the blowing ratio and density ratio resulted in increased film cooling effectiveness at all injection scenarios. Injecting coolant on the PS and the tip surface also resulted in reduced leakage over the tip. The conclusions from this study will provide the gas turbine designer with additional insight on controlling different parameters and strategically placing the holes during the design process.
Quantifying Model Uncertainties and Sensitivities in Parallel Compressor Models
Authors: Voigt Jonas , Jurke Keith-Noah , Schultz Julius , Römer Ulrich , Friedrichs Jens
Published: September 2021

In this work, we consider a parallel compressor model (PCM), which decomposes a compressor encountering non-uniform inflow into a distorted and an undistorted subcompressor, respectively, to determine its overall operating point. The main advantage of PCM modeling is a significantly reduced computational workload. At the same time, modeling errors are introduced, which need to be quantified together with model input uncertainties. Therefore, we introduce a probabilistic setting where unknown parameters are modeled as random variables. We carry out a global sensitivity analysis, which allows to reduce the complexity of the probabilistic model, by setting unimportant input parameters to their nominal values. This analysis attributes portions of the model output variance (the fan efficiency for instance) to particular input parameters or input parameter combinations, through so-called Sobol coefficients. We further include a parameter describing the PCM inflow averaging process into the analysis, which allows to determine the influence of specific modeling choices onto the predicted efficiency. Efficient sampling methods are needed to estimate the sensitivity coefficients with a reasonable computational effort. A key advantage of the global approach is that nonlinear effects are fully taken into account, the necessity of which will be demonstrated by our numerical examples. The model is also compared to CFD reference simulations to quantify structural model errors. This comparison is based on area validation metrics comparing the stochastic distribution functions of the probabilistic PCM model and the reference data.
Revolutionary Vertical Lift Technology (RVLT) Side-by-Side Hybrid Concept Vehicle Powertrain Dynamic Model
Authors: Bianco Santino J. , Chevalier Christine T. , Litt Jonathan S. , Smith Joshua K. , Chapman Jeffryes W. , Kratz Jonathan L.
Published: September 2021

The Side-by-Side (SBS) Hybrid is one of several Revolutionary Vertical Lift Technology (RVLT) concept aircraft identified by NASA to investigate Urban Air Mobility (UAM) requirements. This paper presents a dynamic model of the SBS Hybrid powertrain built using the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS) and the Electrical Modeling and Thermal Analysis Toolbox (EMTAT). The model consists of the rotors, electrical power system, and turboshaft engines connected through freewheeling clutches, gearboxes, and multiple shafts. This research effort models the complex behavior of the powertrain, including the operation of the freewheeling clutches and electrical power system at the simulation time scale of the shaft dynamics. Several simulations highlight the key features present in the model and demonstrate its operation.
Reduced-Order Models for Effusion Modelling in Gas Turbine Combustors
Authors: Paccati S. , Mazzei L. , Andreini A. , Facchini B.
Published: September 2021

Effusion cooling represents the state-of-the-art for liner cooling technology in modern combustion chambers, combining a more uniform film protection of the wall and a significant heat sink effect by forced convection through a huge number of small holes. From a numerical point of view, a high computational cost is required in a conjugate CFD analysis of an entire combustor for a proper discretization of effusion holes in order to obtain accurate results in terms of liner temperature and effectiveness distributions. Consequently, simplified CFD approaches to model the various phenomena associated are required, especially during the design process.

For this purpose, 2D boundary sources models are attractive, replacing the effusion hole with an inlet (hot side) and an outlet (cold side) patches to consider the related coolant injection. However, proper velocity profiles at the inlet patch together with the correct mass flow rate is mandatory to accurately predict the interaction and the mixing between coolant air and hot gases as well as temperature and effectiveness distributions on the liners. In this sense, reduced-order models techniques from the Machine Learning framework can be employed to derive a Surrogate Model (SM) for the prediction of these velocity profiles with a reduced computational cost, starting from a limited number of CFD simulations of a single effusion hole at different operating conditions.

In this work, an application of these approaches will be presented to model the effusion system of a non-reactive single-sector linear combustor simulator equipped with a swirler and a multi-perforated plate, combining ANSYS Fluent with a MATLAB code. The employed Surrogate Model has been constructed on a training set of CFD simulations of the single effusion hole with operating conditions sampled in the model parameter space and subsequently assessed on a different validation set.
Predicting EBC Temperature Limits for Industrial Gas Turbines
Authors: Pint Bruce A. , Stack Padraig , Kane Kenneth A.
Published: September 2021

Higher turbine inlet temperatures may require the use of ceramic matrix composites (CMC) such as SiC/SIC, which require environmental barrier coatings (EBCs) to protect them against the detrimental effect of water vapor. The goal of this project is to determine the maximum bond coating temperature for EBCs for land-based turbines, where the minimum coating lifetime is 25,000 h. If the temperature exceeds the 1414°C melting point of the Si bond coating, then coatings without a bond coating also need to be evaluated. Thus, current Yb2Si2O7 EBCs with a Si bond coating and next-generation EBCs without a Si bond coating are being evaluated in laboratory testing using 1-h cycles in air+90%H2O. For this initial work, coatings were deposited on CVD SiC coupons. Reaction kinetics at 1250°, 1300° and 1350°C have been evaluated by measuring the thickness of the thermally grown silica scale after 100–500 h exposures. For comparison, scale growth rates for uncoated SiC and Si specimens in dry and wet environments were included as minimum and maximum values, respectively. Based on a critical scale thickness failure criteria, estimated maximum temperatures were calculated for both EBC systems using this initial data.
Effect of Rotation on Heat Transfer in AR = 2:1 and AR = 4:1 Channels Connected by a Series of Crossover Jets
Authors: Madhavan Srivatsan , Singh Prashant , Ekkad Srinath V.
Published: September 2021

Detailed heat transfer measurements using transient liquid crystal thermography were performed on a novel cooling design covering the mid-chord and trailing edge region of a typical gas turbine blade under stationary and rotating conditions. The test section comprised of two channels with aspect ratio (AR) of 2:1 (mid-chord) and 4:1 (trailing edge), where the coolant was fed into the AR = 2:1 channel from the root. Rib turbulators with a pitch-to-rib height ratio (p/e) of 10 and rib height-to-channel hydraulic diameter ratio (e/Dh) of 0.075 were placed in the AR = 2:1 channel at an angle of 60° relative to the direction of flow. The coolant after entering this section was routed to the AR = 4:1 section through a set of crossover jets. The purpose of the crossover jets was to induce sideways impingement onto the pin fins that were placed in the 4:1 section to enhance heat transfer. The 4:1 section had a realistic trapezoidal shape that mimics the trailing edge of an actual gas turbine blade. The pin fins were arranged in a staggered array with a center-to-center spacing of 2.5 times the pin diameter in both spanwise and streamwise directions. The trailing edge section consisted of both radial and cutback exit holes for flow exit. Experiments were performed for a Reynolds number (ReDh(AR = 2:1)) of 20,000 at Rotation numbers (RoDh(AR = 2:1)) of 0, 0.1 and 0.14. The channel averaged heat transfer coefficient on trailing side was ∼28% (AR = 2:1) and ∼7.6% (AR = 4:1) higher than the leading side for Rotation number (Ro) of 0.1. It is shown that the combination of crossover jets and pin-fins can be an effective method for cooling wedge shaped trailing edge channels over axial cooling flow designs.