bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat Transfer Measurements for Array Jet Impingement With Castellated Wall
Authors: Kim Taehyun , Jung Eui Yeop , Bang Minho , Lee Changyong , Moon Hee Koo , Cho Hyung Hee 
Published: September 2021

Abstract
Impingement cooling is one of the powerful cooling methods in high-temperature devices. For the gas turbine applications, impingement cooling is commonly applied in the transition piece of a combustor and in the leading edge, suction and pressure sides of a turbine blade/vane. In the suction side and pressure side, impingement cooling is applied as a form of an array jet. However, due to the small gap between the jet hole and target surface, the wall jet faces a crossflow inside of the gap. This crossflow has an adverse effect on the jets and deteriorates the heat/mass transfer performance. Therefore, several studies have been conducted to minimized the crossflow effect. The present study also investigated the effect of crossflow reduction in the gap by having a castellated hole plate. The heat/mass transfer was measured using the naphthalene sublimation method. Heat/mass transfer data are compared among three different cases. One is the baseline case which is simple array impinging jets. Others are the castellated cases with and without rib structures on the target wall. Jet-to-jet spacing (s/d) and jet-to-target spacing (z/d) are selected as geometrical variables. Also, the experiments were conducted for the Reynolds numbers (based on jet hole diameter) of 5,000, 15,000 and 30,000. The baseline case was named as B case, the castellated case without rib structure as C case and with rib structure as CR case. Both C and CR cases showed the crossflow reduction effect and resulted high and similar Nusselt number values.
Analytical Formulation-Based Soot Modelling in Ethylene Laminar Jet Diffusion Flames
Authors: Makhija Amit , Sesha Giri Krishna 
Published: September 2021

Abstract
Soot volume fraction predictions through simulations carried out on OpenFOAM® are reported in diffusion flames with ethylene fuel. A single-step global reaction mechanism for gas-phase species with an infinitely fast chemistry assumption is employed. Traditionally soot formation includes inception, nucleation, agglomeration, growth, and oxidation processes, and the individual rates are solved to determine soot levels. However, in the present work, the detailed model is replaced with the soot formation and oxidation rates, defined as analytical functions of mixture fraction and temperature, where the net soot formation rate can be defined as the sum of individual soot formation and oxidation rates. The soot formation/oxidation rates are modelled as surface area-independent processes. The flame is modelled by solving conservation equations for continuity, momentum, total energy, and species mass fractions. Additionally, separate conservation equations are solved to compute the mixture fraction and soot mass fraction consisting of source terms that are identical and account for the mixture fraction consumption/production due to soot. As a consequence, computational time can be reduced drastically. This is a quantitative approach that gives the principal soot formation regions depending on the combination of local mixture fraction and temperature. The implemented model is based on the smoke point height, an empirical method to predict the sooting propensity based on fuel stoichiometry. The model predicts better soot volume fraction in buoyant diffusion flames. It was also observed that the optimal fuel constants to evaluate soot formation rates for different fuels change with fuel stoichiometry. However, soot oxidation strictly occurs in a particular region in the flame; hence, they are independent of fuel. The numerical results are compared with the experimental measurements, showing an excellent agreement for the velocity and temperature. Qualitative agreements are observed for the soot volume fraction predictions. A close agreement was obtained in smoke point prediction for the overventilated flame. An established theory through simulations was also observed, which states that the amount of soot production is proportional to the fuel flow rate. Further validations underscore the predictive capabilities. Model improvements are also reported with better predictions of soot volume fractions through modifications to the model constants based on mixture fraction range.
Lean-Blow-Out Simulation of Natural Gas Fueled, Premixed Turbulent Jet Flame Arrays With LES and FGM-Modeling
Authors: Schwagerus Alexander , Habisreuther Peter , Zarzalis Nikolaos 
Published: September 2021

Abstract
To ensure compliance with stricter regulations on exhaust gas emissions, new industrial burner concepts are being investigated. One of these concepts is the matrix burner, consisting of an array of premixed, non-swirling jet flames. For the design of such burners, the prediction of fundamental burner properties is mandatory. One of these essential quantities is the lean blowout limit (LBO), which has already been investigated experimentally. This study investigates the possibility of numerical LBO prediction using a tabulated chemistry approach in combination with Large-Eddy-Simulation turbulence modeling. In contrast to conventional swirl burners, the numerical description of blowout events of multi jet flames has not yet been studied in detail. Lean blowout simulations have therefore been conducted for multiple nozzle variants, varying in their diameter and global dump ratio for a variety of operating conditions, showing their general applicability. A procedure to induce LBO is introduced where a stepwise increase in total mass flow is applied. LBO is determined based on the temporal progress of the mean reaction rate. A comparison with measurements shows good agreement and demonstrates that the procedure developed here is an efficient way to predict LBO values. Further investigations focused on the flame behavior when approaching LBO. The flame shape shows a drastic change from single jet flames (stable conditions) to a joint conical flame approaching LBO, which increases in length for increasing inlet velocity, showing the importance of jet interaction at LBO.
Experimental and Numerical Investigation of High-Temperature Multi-Axial Fatigue
Authors: Ramesh Babu Harish , Böcker Marco , Raddatz Mario , Henkel Sebastian , Biermann Horst , Gampe Uwe 
Published: September 2021

Abstract
Gas turbines and aircraft engines are dominated by cyclic operating modes with fatigue-related loads. This may result in the acceleration of damage development on the components. Critical components of turbine blades and discs are exposed to cyclic thermal and mechanical multi-axial fatigue. In the current work, planar-biaxial Low-Cycle-Fatigue (LCF) tests are conducted using cruciform specimens at different test temperatures. The influence on the deformation and lifetime behaviour of the nickel-base disk alloy Inconel 718 is investigated at selected cyclic proportional loading cases, namely shear and equi-biaxial. The calculation of the stress and strain distribution of the cruciform specimens from the experimental data is difficult to obtain due to complex geometry and temperature gradients. Therefore, there is a need for Finite Element (FE) Simulations. A viscoplastic material model is considered to simulate the material behaviour subjected to uniaxial and the selected planar-biaxial loading conditions. At first, uniaxial simulation results are compared with the uniaxial experiment results for both batches of IN718. Then, the same material parameters are used for simulating the biaxial loading cases. The prediction of FE simulation results is in good agreement with the experimental LCF test for both shear and equi-biaxial loadings. The equivalent stress amplitude results of the biaxial simulation are compared with the uniaxial results. Furthermore, the lifetime is calculated based on the stabilized cycle from the simulation and by using Crossland and Sines multi-axial stress-based approaches. The Crossland model predicts fatigue life significantly better than the Sines model. Finally, the simulated lifetime results are compared with the experimental lifetime.
Prediction of Dynamic Behavior of a Single Shaft Gas Turbine Using NARX Models
Authors: Asgari Hamid , Ory Emmanuel 
Published: September 2021

Abstract
Gas turbines are internal combustion engines widely used in industry as main source of power for aircrafts, turbo-generators, turbo-pumps and turbo-compressors. Modelling these engines can help to improve their design and manufacturing processes, as well as to facilitate their operability and maintenance. These eventually lead to manufacturing of gas turbines with lower costs and higher efficiency at the same time. The models may also be employed to unfold nonlinear dynamics of these systems.
The aim of this study is to predict the dynamic behavior of a single shaft gas turbine by using open-loop and closed-loop NARX models, which are subsets of artificial neural networks. To set up these models, datasets of significant variables of the gas turbine are used for training, test and validation processes. For this purpose, a comprehensive code is developed in MATLAB programming environment. In addition to the open-loop model, a closed-loop model is set up for multi-step prediction. The results of this study demonstrate the capability of the NARX models in reliable prediction of gas turbines’ dynamic behaviors over different operational ranges.
Analysis of Loading and Vibration Histories on Natural Frequencies and Modal Damping of Blades With Friction at Root Contact Interfaces
Authors: Chen Junjie , Zang Chaoping , Zhou Biao , Petrov E. P. 
Published: September 2021

Abstract
Gas turbine engines change the rotation speed during operation in a wide range from zero to the speed corresponding to the cruise flight and the history of the rotation speed variation is individual for each flight. During the engine operation the bladed disks pass different resonances frequencies and may experience significant vibration amplitudes. The vibrations can affect the interaction conditions at friction contact interfaces, including contact stresses distribution and their contact status. As a result, the contact conditions can differ from those that are established at the initial bladed disk assembling and these conditions are dependent on the history of the vibration that a bladed disk experiences during every engine operation cycle. The variation of the contact conditions at friction contact interfaces affects modal properties and modal damping characteristics of a bladed disk, and it is important to assess the possible variation of these properties during the engine exploitation.
In this paper, a transient analysis is performed to simulate blade vibration under different loading histories occurred in a flight mission. The analysis is performed for different histories of the blade vibration and a method is proposed for the analysis of modal damping in the blade root joints under the influence of different loading histories. The influence of different loading histories, friction contact parameters, the vibration excitation levels and resonating modes on modal characteristics and modal damping factors is studied, The pre-stress effects due to blade assembling are also explored.
On Small Scale LNG Concepts
Authors: Kurz Rainer , Ji Min , Beck Griffin , Allison Timothy C. 
Published: September 2021

Abstract
The different economics of small scale LNG plants put more emphasis on capital expenses over process efficiency, and thus favors simpler refrigeration cycles. We typically find reverse Brayton cycles, or SMR (Single mixed refrigerant) cycles. These cycles have specific requirements to the compression equipment, and typically have smaller drivers, either electric drives or gas turbines. The relationship between output, driver size, and process preferences is explained. The type of compressors, and expanders needed are discussed, together with thoughts and the driver preferences. This includes the different control methods that can be used, both for the cycle adaptation, as well as the related control of the compressors, expanders, valves and drivers. Equipment performance maps are created to highlight the required different operating conditions. This result allows for subsequent optimization discussions.
Additively Manufactured Porous Geometries for Hybrid Turbine Cooling
Authors: Fier Nathan D. , Bogard David G. 
Published: September 2021

Abstract
Discrete film cooling holes are limited by subtractive manufacturing techniques and experience depreciating performance when operating above critical velocity ratios. This study introduces an alternative method of bringing coolant to the surface of the blade via finite strips of porous material interlaced throughout the blade, made possible by advances in additive manufacturing (AM). Both experimental and computational studies were performed on the porous hybrid configuration to characterize downstream and off-wall performance, where experimental adiabatic effectiveness values were achieved using a plastic, fused deposition printed lattice structure. The method of bringing coolant onto the surface of the blade through an additively manufactured porous region experienced downstream adiabatic effectiveness values similar to slots while providing better structural stability. Additionally, the hybrid configuration outperformed shaped film cooling holes by injecting an ultra-thin layer of coolant that was evenly distributed span-wise across the blade. When operating at VRhybrid = 0.052 and L/d = 2 the hybrid configuration produced spatially averaged values 30% greater than the shaped holes while using equivalent coolant mass flow rate. Also, for an L/d = 10, the spatially averaged adiabatic effectiveness, for the hybrid configuration, is a factor of three greater than for shaped film cooling holes, while requiring a five times greater coolant mass flow rate. Finally, the RANS computational model accurately predicted downstream effectiveness values, at low velocity ratios, within experimental uncertainty but showed inaccuracies when predicting off wall effectiveness values and at higher velocity ratios.
Effect of Differential Tip Clearance on the Performance of a Tandem Rotor
Authors: Kumar Amit , Chhugani Hitesh , More Shubhali , Pradeep A. M. 
Published: September 2021

Abstract
Tandem blade is an interesting concept that promises a higher total pressure rise per stage. Owing to two separate tip leakage vortices and their interaction, losses are likely to increase particularly near the tip region. Although, rotors are designed with optimum tip clearance, the clearance changes during engine operation as well as during its service life. In the case of tandem rotors, the forward and the aft rotors can have different tip clearances. This will also impact the performance of the stage. Six different tip clearances have been investigated. ANSYS CFX is used for steady RANS computational analysis. The results suggest that the performance of the tandem rotor is highly sensitive to the forward rotor tip clearance. Higher tip clearance adversely affects the total pressure rise and operation stability of the tandem rotor. At design mass flow rate, the performance degradation for tandem configuration with the higher tip clearance (Case2, Case 3, Case 5, and Case 6), is attributed to the vortex breakdown of TLV1, which leads to the sudden expansion of the blockage region near the rotor tip. Vortex breakdown primarily depends upon the swirling strength of TLV1 and TLV2 as well as on the adverse pressure gradient. Near the stall point, the role of the adverse pressure gradient becomes more dominant in the vortex breakdown.
Investigations on the Aerothermal Performance Uncertainty Quantification of the Turbine Blade Squealer Tip
Authors: Huang Ming , Li Zhigang , Li Jun , Song Liming 
Published: September 2021

Abstract
The first-stage rotor squealer tip is a key area in the gas turbine for both aerodynamic performance and heat transfer characteristics, which should be carefully designed. However, harsh operating conditions near the rotor squealer tip can cause the geometry of the squealer tip to degrade, and manufacturing inaccuracies can also cause the squealer tip geometry to deviate from the ideal design. In this work, an uncertainty quantification (UQ) method is proposed using the non-intrusive polynomial chaos expansion method and Smolyak sparse grids. Then coupled with three dimensional (3D) Reynolds-Averaged Navier-Stokes (RANS) solutions, an uncertainty quantification procedure is carried out for aerodynamic and heat transfer performance of GE-E3 rotor blade squealer tip. A parameter sensitivity analysis using the Sobol Indice method is carried out to identify the key parameters for aerothermal performance of the squealer tip. Wherein, the inlet total temperature and the blowing ratio are considered as flow condition uncertainty parameters and tip clearance is considered as geometrical uncertainty parameters.
The uncertainty analysis results show that under the influence of the uncertain geometry and operating conditions, the heat flux of squealer tip basically conforms to the normal distribution and the statistical mean value of it increased by 13.56% relative to the design value and the probability of it deviating from the design value by 10% is as high as 65.68% The statistical average of the squealer tip film cooling effectiveness is reduced by 29.52% compared to the design value, and the probability of it deviating from the design value by 10% is as high as 91.83%. The result of sensitivity analysis reveals that the uncertainty of the aerodynamic characteristics of the squealer tip is almost entirely caused by the tip clearance which accounts for 88.02% of the variance of the leakage flow rate. The inlet total temperature has almost no effect on the uncertainty of the aerodynamic performance. However, it is the dominant variable for the uncertainty of the heat transfer performance considering that its variance indexes for tip heat flux QTip and film cooling effectiveness η are 84.87% and 24.87% respectively. Compared with the main effects, the influence of the interaction effects among the variables on the squealer tip aerothermal performance is almost negligible.
Numerical Investigations on the Aerothermal Performance and Film Cooling Effectiveness of Turbine Vane Endwall at Inlet Swirl Conditions
Authors: Li Zhiyu , Zhang Kaiyuan , Li Zhigang , Li Jun 
Published: September 2021

Abstract
Lean burn premix technology of gas turbines results in that the turbine combustor outlet has strong swirl flow characteristics which directly influences the inlet flow condition of the first turbine vane downstream from combustor and raise the thermal load of endwall. The aerothermal performance and film cooling effectiveness of first turbine vane endwall at different inlet swirl conditions is numerically investigated in this paper. The flow pattern, Nusselt number distribution and film cooling effectiveness of turbine vane endwall at the uniform and three kinds of swirl numbers (0.6, 0.8, 1.0) inflow conditions with clockwise and anticlockwise swirl orientations are analyzed using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and SST k-ω turbulence model solutions. The obtained results show that the flow field is apparently influenced by inlet swirl conditions. The separation in passage is clearly suppressed at clockwise swirl inflow conditions but anticlockwise make the flow pattern more complex. Inlet swirl can increase the overall Nu on the endwall. Especially in the area upstream of leading edge and area between the first and second row of film holes whose Nu are increased by 4 and 1.5 times compared with uniform inflow, respectively. Not only swirl number but also orientation can affect the film cooling effectiveness distribution of the vane endwall. The better film cooling effectiveness distribution and higher film cooling effectiveness downstream of each film hole row can be achieved at the clockwise swirl inflow conditions by weakening the accumulation of coolant near the suction side of the turbine vane endwall. Compared with uniform inflow, average film cooling effectiveness of endwall between the second row and third row is increased from 0.21 to 0.27 at clockwise SN = 1.0 for the maximum increase. The detailed flow field and aerothermal performance of the turbine vane endwall at different swirl inflow conditions is also discussed and illustrated.
Modelling of Turbulent Premixed CH4/H2/Air Flames Including the Influence of Stretch and Heat Losses
Authors: Kutkan Halit , Amato Alberto , Campa Giovanni , Ghirardo Giulio , Tay Wo Chong Luis , Æsøy Eirik 
Published: September 2021

Abstract
This paper presents a RANS turbulent combustion model for CH4/H2/air mixtures which includes the effect of heat losses and flame stretch. This approach extends a previous model concept designed for methane/air mixtures and improves the prediction of flame stabilization when hydrogen is added to the fuel. Heat loss and stretch effects are modelled by tabulating the consumption speed of laminar counter flow flames in a fresh-to-burnt configuration with detailed chemistry at various heat loss and flame stretch values. These computed values are then introduced in the turbulent combustion model by means of a turbulent flame speed expression which is derived as a function of flame stretch, heat loss and H2 addition. The model proposed in this paper is compared to existing models on experimental data of spherical expanding turbulent flame speeds. The performance of the model is further validated by comparing CFD predictions to experimental data of an atmospheric turbulent premixed bluff-body stabilized flame fed with CH4/H2/air mixtures ranging from pure methane to pure hydrogen.
Center Body Burner for Sequential Combustion: Superior Performance at Lower Emissions
Authors: Ciani A. , Wood J. P. , Maurer M. , Bunkute B. , Pennell D. , Riazantsev S. , Früchtel G. 
Published: September 2021

Abstract
Modern gas turbines call for an ultra-high firing temperature and fuel flexibility while keeping emissions at very low levels. Sequential combustion has demonstrated its advantages toward such ambitious targets.
A sequential combustion system, as deployed in the GT26 and GT36 engines, consists of two burners in series, the first one optimized to provide the optimum boundary condition for the second one, the sequential burner. This is the key component for the achievement of the required combustor performance dictated by F and H class engines, including versatile and robust operation with hydrogen-based fuels.
This paper describes the key development considerations used to establish a new sequential burner surpassing state-of-the-art hardware in terms of emission reduction, fuel flexibility and load flexibility. A novel multi-point injector geometry was deployed based on combustion and fluid dynamic considerations to maximize fuel / air mixing quality at minimum pressure loss. Water channel experiments complemented by CFD describe the evolution of the fuel / air mixture fraction through the mixing section and combustion chamber to enable operation with major NOx reduction. Furthermore, Laser Doppler Anemometry and Laser Induced Fluorescence were used to best characterize the interaction between hot-air and fuel and the fuel / air mixing in the most critical regions of the system. To complete the overview of the key development steps, mechanical integrity and manufacturing considerations based on additive manufacturing are also presented. The outcome of 1D, CFD and fluid dynamic experimental findings were then validated through full-scale, full-pressure combustion tests. These demonstrate the novel Center Body Burner is enabling operation at lower emissions, both at part load and full load conditions. Furthermore, the validation of the burner was also extended to hydrogen-based fuels with a variety of hydrogen / natural gas blends.