bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Verification Tests of Titanium 50-Inch and 60-Inch Last Stage Blades for Steam Turbines
Authors: Senoo Shigeki , Kudo Takeshi , Fukushima Hisataka , Segawa Kiyoshi , Sakakibara Kazuya 
Published: November 2019

Abstract
Increasing the annulus area of the last stage in steam turbines provides an effective way of increasing power output and improving the efficiency by reducing the amount of lost kinetic energy. The 50-inch and 60-inch last stage blades, which provide some of the world’s largest exhaust annulus areas, have been developed for 3600 rpm and 3000 rpm units respectively. The blades are designed to suppress the increase in losses caused by the supersonic inflow, and to ensure reliability. This paper describes the verification of the aerodynamic performance through four-stage model steam turbine tests. In addition, the unsteady flow phenomena caused by shock wave interactions near the tip between the last stage stator and rotor are clarified by unsteady flow measurements and calculations.
The characteristic of total-to-static efficiencies and flow distributions measured with pneumatic five-hole probes are obtained as designed. Static pressure recovery is also confirmed by static pressure measurement on the exhaust hood walls and three-dimensional turbulent flow analysis.
Regarding the unsteady stator-rotor interactions, the flow fluctuations such as static pressures and flow angles become relatively larger, when the travelling bow shock waves emanating from upstream of the rotor leading edge impinge near the stator trailing edge, because the axial distance between the emanating and impinging position of the shock wave is smaller. The static pressure on the suction surface of the rotor blade becomes locally large when it comes to the same circumferential portion as the stator trailing edge. However, the mass flow rate and loss variations caused by the unsteadiness are small, because the inlet relative Mach number is as small as 1.25, so that the strength of the shock wave is small.
Investigation on the Internal Cooling of Two-Passage Channels With Parallel Ribs and Guide Vanes
Authors: Amano Ryoichi S. , Saravani Mandana S. , DiPasquale Nicholas 
Published: November 2019

Abstract
The present work investigates the effects of various guide vane designs on the heat transfer enhancement of rotating U-Duct configuration with parallel 45-deg ribs. The ribs were installed on the bottom wall of the channel which has a constant heat flux boundary condition. The channel has a square cross-section with a 5.08 cm (2 in) hydraulic diameter. The first and second passes are 514 mm and 460 mm, respectively. The range of Reynolds number for turbulent flow is up to 35,000. The channel rotates in various speed up to 600 rpm which brings the maximum rotation number of 0.75. Several computational fluid dynamics simulations are carried out for this study to understand the effect of guide vanes on flow and heat transfer in serpentine channels under various operating conditions.
Aerodynamic Excitation Analysis of a Radial Turbine Featuring a Multi-Channel Casing Design
Authors: Hassan Ahmed Farid , Blackburne Jennifer , Kovachev Nikola , Schatz Markus , Vogt Damian M. 
Published: November 2019

Abstract
Partial admission using Multi-channel Casing (MC) is a technique under investigation for controlling the operation of radial inflow turbines. The MC has different admission configurations according to the number of open channels which control the relation between the mass flow and expansion ratio at different operating speeds in order to provide the advantage of operational controllability. These different casing configurations will excite the structure in different manners and may cause high cycle fatigue on the rotor. Consequently, the source of excitation for a multi-channel casing is not only the casing asymmetries but also the different admission configurations.
The current study investigates the effect of different MC admission configurations on the aerodynamic excitation mechanisms of the turbine rotor blades. The Generalized Pressure (GP) and Generalized Force (GF) approach is used to compare the aerodynamic forcing field acting on the rotor blade for different admission arrangements. First, a 3D unsteady numerical simulation of a radial turbine featuring four channel casing is performed for different admission configurations to provide the raw unsteady pressure. In conjunction with this, a finite element modal analysis is applied to the turbine rotor to calculate the natural frequency and the mode shapes. Finally, the results from the unsteady simulation and the modal analysis are superimposed to calculate and compare the GP and GF.
It is found that using different MC admission configurations has a significant effect on the aerodynamic forces acting on the radial turbine featuring MC. One of the applied configurations increases the generalized force by up to 2.6 times compared to the full admission configuration, MC 4, at engine order 8. While another configuration reduces it by a factor of 0.7 compared with the same base case.
Experimental Film Cooling Effectiveness of Multi-Row Patterns on Flat and Step-Down Surfaces
Authors: Baldino Filippo , Taslim Mohammad E. 
Published: November 2019

Abstract
Multiple rows of film cooling holes have been widely used for the protection of gas turbine airfoils and other hot sections. In the common approach, however, the streamwise surfaces between the film holes may not receive enough protection. The objective of this research was to overcome this issue by introducing a new layout of film cooling, the step-down surfaces. Pressure-sensitive paint technique was used to test three pairs of geometries. Each pair consists of a flat and a step-down surface for back to back comparisons, under otherwise identical conditions. Two rows of 30° angled cylindrical holes of 3.175 mm diameter, exiting at the step bottom corner, introduced the coolant to the surface. Two spanwise pitch-to-diameter ratios of 2 and 4, two row distance to hole diameter of 4 and 8, four blowing ratios of 0.25, 0.5, 0.75 and 1, all at a constant density ratio of 1 were tested. Adding a step-down of the order of 0.8 hole-diameter proved to significantly increase the overall film cooling effectiveness. Two major improvements compared to a flat surfaces were observed: (a) longer streamwise film cooling effectiveness (b) more uniform spanwise distribution of coolant. The main reason of all the improvements is the aerodynamic phenomenon governing the flow evolution, the Coanda effect. The latter, indeed, enhances the flow attachment to the airfoil surface downstream the step.
Effect of Non-Axisymmetric Endwall Profiling on Heat Transfer and Film Cooling Effectiveness of a Transonic Rotor Blade
Authors: Li Jinjin , Yan Xin , He Kun 
Published: November 2019

Abstract
Effects of non-axisymmetric endwall profiling on total pressure loss, heat transfer and film cooling effectiveness of a transonic rotor blade were numerically investigated. The numerical methods, including the turbulence model and grid sensitivity, were validated with the existing experimental data. To reduce thermal load on endwall, non-axisymmetric endwall profiling near leading edge and at pressure-side corner area were performed with a range of contour amplitudes. Heat transfer and flow fields near the profiled endwalls were analyzed and also compared to the plain endwall configuration. On the profiled endwall, three kinds of cooling-holes, i.e. cylindrical holes, rounded-rectangular holes and elliptical holes, were arranged, and film cooling effect was investigated at three blowing ratios. Results indicate that, with endwall profiling, the area-averaged Stanton number on endwall is reduced by 7.71% and total pressure loss in cascade is reduced by 11.07%. Among three kinds of cooling holes, arrangement of elliptical hole performs the best film cooling effect on profiled endwall. Compared with plain endwall, non-axisymmetric endwall with elliptical cooling holes improves film cooling coverage by 10.87%, reduces the Stanton number by 8.88% and increases the net heat flux reduction performance by 4% at M = 0.7.
Investigation and Prediction Models of the Axial Thrust in Centrifugal Compressors
Authors: Younsi Mohand , Hypolite Eric 
Published: November 2019

Abstract
The purpose of this paper is to provide an overview of the prediction methods used to accurately determine the axial rotor thrust in centrifugal compressors. Thus, semi-empirical models were developed to estimate the aerodynamic forces acting on each side of the rotating impeller. In addition to this, a numerical approach based on Computational Fluid Dynamics (CFD) technique was carried out to simulate the 3D steady flow in the centrifugal compressor. The numerical simulations consider the entire geometry details. The resulting axial thrust, estimated by the semi-empirical approach and the CFD calculations, were compared to experimental data. The application of these approaches was extended and discussed at different operating conditions. Furthermore, the effect of the expeller vanes (pump-out-vanes) on the axial thrust was highlighted.
Ignition Delay Times of Syngas and Methane in sCO2 Diluted Mixtures for Direct-Fired Cycles
Authors: Barak Samuel , Pryor Owen , Ninnemann Erik , Neupane Sneha , Lu Xijia , Forrest Brock , Vasu Subith 
Published: November 2019

Abstract
In this study, a shock tube is used to investigate combustion tendencies of several fuel mixtures under high carbon dioxide dilution and high fuel loading. Individual mixtures of oxy-syngas and oxy-methane fuels were added to CO2 bath gas environments and ignition delay time data was recorded. Reflected shock pressures maxed around 100 atm, which is above the critical pressure of carbon dioxide in to the supercritical regime. In total, five mixtures were investigated within a temperature range of 1050–1350K. Ignition delay times of all mixtures were compared with predictions of two leading chemical kinetic computer mechanisms for accuracy. The mixtures included four oxy-syngas and one oxy-methane combinations. The experimental data tended to show good agreement with the predictions of literature models for the methane mixture. For all syngas mixtures though the models performed reasonably well at some conditions, predictions were not able to accurately capture the overall behavior. For this reason, there is a need to further investigate the discrepancies in predictions. Additionally, more data must be collected at high pressures to fully understand the chemical kinetic behavior of these mixtures to enable the supercritical CO2 power cycle development.
Large-Eddy Simulation of Shaped Hole Film Cooling With the Influence of Cross Flow
Authors: Wang Qingsong , Li Yifei , Bian Xiutao , Su Xinrong , Yuan Xin 
Published: November 2019

Abstract
In the modern highly-loaded gas turbine, due to the large pressure difference between the suction side and the pressure side of the turbine blade, strong cross flow is formed and it strongly affects the aerodynamic and cooling performances in the end-wall region. The film cooling behavior in the environment of strong cross flow is different from the straight channel environment widely studied in the literature. In this research, the effect of cross flow on film cooling is investigated by Large Eddy Simulation (LES) using subgrid-scale (SGS) model. Numerical simulation is carried out in a curved passage to simulate the turbine blade passage. Shaped cooling hole with blowing ratio 1 is studied. The time-averaged friction line results are compared with existing experimental ink trace results. The vortex structures, both time-averaged and instantaneous, are analyzed to study the effect of cross flow on film cooling. At the exit of the cooling hole, the hanging vortices with negative y-vorticity are more flat in shape and closer to the wall in position in contrast to hanging vortex with positive y-vorticity, which is caused by cross flow and results in the asymmetry of hairpin vortices downstream as well as the asymmetry of the distribution of coolant. It has been shown that the vortices from mainstream have a significant impact on the field near the exit of the cooling hole. Those vortices interact with the hairpin vortices from the cooling hole and directly lead to the asymmetry of the hairpin vortices. Proper Orthogonal Decomposition (POD) analysis is further conducted to extract the dominant flow structures and the physical mechanisms of primary POD modes are given to explain the distribution of film cooling effectiveness affected by cross flow. Based on the specific situation in this work, a fast incremental POD (iPOD) approach is adopted since the rank of the field matrix is far less than the rows, which is caused by the tall and thin character of the matrix, which makes the analysis less costly and more effective. This research helps to understand the cooling performance in the real turbine blade passage and to explain the coolant mixing process based on the instantaneous flow field obtained using high precision LES simulation and powerful iPOD.
Laser Thermal Gradient Test of a Thermal Barrier Coating and Failure Analysis
Authors: Wu Yingsang , Wang Yao , Hsu Pei-feng , McCay Mary Helen , Croy Ed , Moreno David , He Lei , Wang Chao , Zhang Hongqi 
Published: November 2019

Abstract
Thermal barrier coatings (TBC) are used to protect the hot components of gas turbine engines to enhance thermal efficiency and component service life. It is critical for TBC development that a testing method be used to understand the potential and limitation of coating’s durability and integrity under the gas turbine engine operation conditions. In this paper, laser high heat flux testing with an applied temperature gradient across TBC coated buttons is presented. The ceramic coating is ZrO2-8 wt.% Y2O3 applied via the air plasma spraying process on top of a NiCoCrAlY bond coating and an Inconel alloy substrate button of 25.4 mm diameter. The coated button is subject to precisely-controlled laser heating on the top side (1150°C) and temperature gradient of 63.9°C/mm through the button overall thickness. The TBC button lasts 160.9 hr or 570 cycles of laser heating. Analysis of void fraction change before and after the test, thermal conductivity change during the laser test, and failure assessment are presented. After the test, the top coating has cracks in vertical or oblique directions and significant horizontal cracks near the top coating and bond coating interface. Significant horizontal top coating cracks close to the interface between the top coating and bond coating appear near the button center. Although the coating delamination has not occurred yet, at the end of the laser testing the button is close to delamination. Based on the horizontal cracks and the thermally grown oxide layer geometry, a finite element analysis is conducted to calculate the residual stress and the strain energy release rate. A possible approach to combine laser rig test result and finite element computation for developing a TBC service life model is discussed.
Improving Accuracy and Comparability of Turbocharger Performance Measurements
Authors: Schinnerl Mario , Bogner Mathias , Ehrhard Jan 
Published: November 2019

Abstract
The reduction of fuel consumption and emissions is the most dominant challenge in powertrain development. Therefore, engine and turbocharger have to be matched with high accuracy to achieve optimum powertrain efficiencies.
With respect to relevant engine operating points, compressor maps can be measured in full operating range on a standard hot gas test bench. Even though there is no need for extrapolation of the operating range, they have to be corrected for the impact of heat transfer to represent the adiabatic performance of the compressor stage.
The common approach to evaluate the turbine efficiency is to apply the energy balance of the entire turbocharger where the turbine power is the sum of the compressor power and the friction losses of the radial and axial journal bearings. The adiabatic compressor power in combination with the calculation of the friction losses by using validated run-up simulations enables the evaluation of the isentropic turbine efficiency and the comparability to CFD simulations of the turbine stage.
For reasons of comparability to CFD simulations, which can predict a wide operating range of the turbine stage, the limited measureable turbine operating range is enhanced by a so-called compressor closed loop unit (CCLU). This additional test device enables to vary the demand of compressor power for the same operating points as in the standard mapping and therefore to enlarge the measureable turbine operating range. In combination with proper extrapolation methods, the isentropic turbine efficiency can now be compared to CFD simulations.
Autoignition Study of “Gas-to-Liquid” Fischer-Tropsch Jet Fuels
Authors: Alturaifi Sulaiman A. , Atherley Tatyana , Mathieu Olivier , Guo Bing , Petersen Eric L. 
Published: November 2019

Abstract
In recent years, there has been an interest in finding a jet fuel alternative to the crude oil-based kerosene. Gas-to-liquid (GtL) fuel is being derived via Fischer-Tropsch synthesis processes by converting natural gas to longer-chain hydrocarbons which form the basis for jet fuel. In this study, new experimental ignition delay time measurements of GtL jet fuels have been determined at elevated pressures and temperatures. The measurements were conducted in a heated, high-pressure shock-tube facility capable of initial temperatures up to 200°C. Two GtL jet fuels were investigated, Shell GTL and Syntroleum S-8, which can be used in aviation applications at concentrations up to 50% blended with conventional oil-based kerosene. The ignition delay time measurements were conducted behind reflected shock waves for gaseous-phase fuel in air at a pressure around 10 atm and over a temperature range of 966 to 1266 K for two equivalence ratios, fuel lean (ϕ = 0.5) and stoichiometric (ϕ = 1.0). Ignition delay time was determined by observing the pressure and electronically excited OH chemiluminescence around 307 nm at the endwall location. Similar ignition delay times were observed for the two fuels at the fuel lean condition, while Syntroleum S-8 showed shorter ignition delay times at the stoichiometric condition. Comparisons are made with ignition delay time measurements for Jet-A previously conducted in the same facility and showed reasonable agreement over the tested conditions. The predictions from the available literature for GtL fuel surrogate kinetics models were obtained and compared with the experimental measurements.
Economy and Emission Analysis of the Effects of Different Diluents in Syngas for Gas Turbine Using Low Heating Value Syngas Through Numerical Model
Authors: Mu Yanfei , Shi Shaoping , Qin Ye , Zhang Bo , Yan Shu , Liu Xin , Chen Xinming 
Published: November 2019

Abstract
Integrated Gasification Combined Cycle (IGCC) combines gasifier, gas turbine, and steam turbine to increase the electricity production efficiency while having lower emissions compared to conventional coal fired power plants. The syngas produced from coal gasification differs from natural gas in terms of composition, heating value, as well as combustion characteristics. Typically, syngas has much lower heating value than natural gas, thus the flow rates of the syngas are higher than that of natural gas for a similar size gas turbine. In addition, the hydrogen in the syngas may lead to more rapid combustion and higher flame temperature compared to natural gas, which may result it more NOx emission. Thus, to address these issues, syngas could be diluted with nitrogen, steam or carbon dioxides to lower the flame speed and temperature. The effects of different diluents on the fuel economy and emissions are investigated by a combined thermodynamic and computational fluid dynamics (CFD) model. The thermodynamic model was first established and validated by the industrial operational data. More power output and better fuel economy can be achieved using N2 and CO2 as diluent instead of steam from calculation with the thermodynamic model. A numerical case study was done to estimate the profit using nitrogen instead of the steam considering in industrial operation conditions as well as all other costs. Next, the CFD model was employed to further examine the combustion stability and NOx emissions. The results show that changing diluent from steam to nitrogen will not impact the combustion stability and may lead to slightly lower NOx emissions. Finally, the partial replacement of steam by nitrogen as diluent has been realized and the industrial operational performance has also been reported.
The Influence of Non-Axisymmetric End Wall in a High-Load Compressor Stage With Tandem Stator
Authors: Li Xiangjun , Chu Wuli 
Published: November 2019

Abstract
The application of tandem blade in compressors has been study for decades. According to the open literature, using tandem blade can effectively extend the working range of the compressor under high incidence. Many earlier researches focused on the two-dimensional influence of tandem blade, and revealed that a proper arrangement on the positions of the front and the rear blade would allow the boundary layer on the suction side to develop in a more favourable way to control the two-dimensional separation. However, because of the serious corner separation and higher loss in the end wall region of high-load compressors. Some recent researches started to focus on the three-dimensional flow for further understanding the effect of the tandem setup.
As an effective way to influence the end wall flow, the profiled end wall can be applied to both turbines and compressors to reduce the end wall loss. However, the co-work of tandem blade and profiled end wall was seldom reported. In this paper, a numerical research was carried out based on a single-stage high-load compressor with a tandem stator. After a numerical study for the hub separation. A series of optimization design were carried out for the hub end wall of the rotor, stator and the stage to improve the overall efficiency. The discussion revealed the positive effects of the optimum profiled end wall on the tandem stator were on one hand to limit the extension of the recirculation region of the front passage and on another hand to suppress the suction side corner separation in the rear passage. The efficiency of the upstream rotor was also reduced in small value because the variation of the through flow. After that, the indirect influence of the rotor profiled end wall on the stator and the stage profiling case were also analysed. The optimum stage hub profiling did not equal to the simple combination of the optimum stator and the rotor hub end wall. It is found that in the stage profiling case, the variation of loss in stator and rotor are very well adjusted and balanced by the optimization algorithm. The improvement of efficiency therefore achieved the highest value.