bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation on the Flow Characteristics in a Cover-Plate Pre-Swirl System
Authors: Jian Menghua , Yang Xuesen , Dong Wei 
Published: September 2021

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.