bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of S-Shaped Intake on Aeromechanical Characteristics of a Transonic Fan
Authors: Zheng Yun , Xu Kang , Yang Hui , Gao Qingzhe , Jin Xiubo 
Published: January 2021

Abstract
S-shaped intakes are widely used in aero-engines of modern fighters because of the demand for reducing radar cross-section. Besides, boundary layer ingestion (BLI) configurations are proposed in civil engines recently due to the high propulsion efficiency and low fuel consumption. And S-shaped ducts are usually used as transition sections of diffusers in BLI intakes. Compared with normal straight intakes, it is inevitable to bring in the influence of inlet distortion and acoustic reflection for S-shaped intakes. Meanwhile, composite fan blades, shorter intakes and integrated blisks are common in engine designs. So, fan blades are prone to serious vibrations such as flutter and forced response, which may lead to high-cycle fatigue, and further cause structural failure.
The aeromechanical characteristics of a transonic fan (NASA rotor67) in presence of a s-shaped intake are predicted by an in-house integrated time-domain aeroelasticity code. The three dimensional, time-accurate, unsteady Reynolds-Averaged Navier-Stokes equations are solved in fluid domain, and the structural dynamic equations of blade vibration are solved with a modal superimposition method.
Mode shapes and natural frequencies of rotor blade are obtained with a commercial Finite Element code, and the Campbell diagram is presented. Full-annulus aeroelastic calculations are conducted to obtain the transient response and the aerodynamic damping of fan blades. Different techniques for interface between the intake and the rotor are used for comparison to demonstrate the influence of upstream interaction. A mixing-plane model is used at the interface to model the blade vibration without interactions with the distortion, while a sliding-plane model is used at the same condition to include the flow distortion and acoustic effects on the fan blade motion. S-shaped intakes with two different axial length are investigated for the forced response and flutter stability. This study indicates that the forced response level is attenuated due to the decrease of distortion level as the length increases, while the flutter stability is determined by the phase difference between the upstream and the reflective acoustic wave.
Numerical Simulation of a Particle in Air Flow Around a Turbine Blade
Authors: Oshima Ippei , Furuichi Mikito 
Published: January 2021

Abstract
The Steam turbine is widely used for generating electricity, in the thermal, nuclear and geothermal power generation systems. A wet loss is known as one of the degrading factors of the performance. To reduce the amount of liquid phase generated by condensation and atomization from nozzles, the prediction of the distribution of liquid mass flow rate inside the turbine is important. However, the quantitative understanding and the prediction method of the liquid flow inside the turbine remain unclear because physics inside a turbine is consisting of complex multiscale and multiphase events. In the present study, we proposed a theoretical model predicting the motion of droplet particles in gas flow based on Stokes number whose model does not require numerical simulation. We also conducted the numerical validation test using three-dimensional Eulerian-Lagrangian simulation for the problem with turbine blade T106. The numerical simulation shows that the particle motion is characterized by the Stokes number, that is consistent with the assumption of the theoretical model and previous studies. When Stokes number is smaller than one, the particle trajectory just follows the gas flow streamline and avoids the impacts on the surface of T106. With increasing Stokes number, the particles begin to deviate from the gas flow. As a result, many particles collide with the surface of T106 when the Stokes number is approximately one. When the Stokes number is extremely larger than one, particles move straight regardless of the background gas flow. The good agreements between the theoretical predictions and numerical experiment results justify the use of our proposed theoretical model for the prediction of the particle flow around the turbine blade.
Aerodynamics and Heat Transfer Inside a Gas Turbine Mid-Passage Gap
Authors: Shaikh Faisal , Rosic Budimir 
Published: January 2021

Abstract
Gas turbine blades and vanes are typically manufactured with small clearances between adjacent vane and blade platforms, termed the midpassage gap. The midpassage gap reduces turbine efficiency and causes additional heat load into the vane platform, as well as changing the distribution of endwall heat transfer and film cooling. This paper presents a low-order analytical analysis to quantify the effects of the midpassage gap on aerodynamics and heat transfer, verified against an experimental campaign and CFD.
Using this model, the effects of the gap can be quantified, for a generic turbine stage, based only on geometric features and the passage static pressure field. It is found that at present there are significant losses and a large proportion of heat load caused by the gap, but that with modified design this could be reduced to negligible levels.
Cooling flows into the gap to prevent ingression are investigated analytically and with CFD. Recommendations are given for targets that turbine designers should work toward in reducing the adverse effects of the midpassage gap. A method to estimate the effect of gap flow is presented, so that for any machine the significance of the gap may be assessed.
Numerical Study of Erosion due to Online Water Washing in Axial Flow Compressors
Authors: Di Gruttola Francesca , Agati Giuliano , Venturini Paolo , Borello Domenico , Rispoli Franco , Gabriele Serena , Simone Domenico 
Published: January 2021

Abstract
Recent year witnessed an increasing interest in online water washing technique since it allows to minimize compressor performance losses in the time interval between two off-line washing. However, the washing capability and the related erosion risk depend on several parameters such as the injection duration, the droplet size, the spray angle, the water mass flow rate and the injector positions. The influence of such parameters on the washing capability and erosion rate is analysed. Results are discussed with reference to number of impacts, wetted surface, capture efficiency, accumulated energy and erosion. The numerical simulation is performed with ANSYS Fluent in which a new water droplet erosion model, introduced in previous papers, is here included as a User Defined Function. The discussion provides useful information for prescribing the injector characteristics and the water washing procedure with the aim of minimizing the erosion risk.
Effects of Cooling Configurations on the Aerothermal Performance of a Turbine Endwall With Jet Impingement and Film Cooling
Authors: Bu Hongyan , Guo Zhendong , Song Liming , Li Jun 
Published: January 2021

Abstract
With the rapid increase of turbine inlet temperature and the application of premixed combustion, turbine components, particularly the turbine endwall, works in extremely harsh environment and must be effectively cooled to ensure the component durability. Recently, new cooling schemes that employ both external film cooling and internal jet impingement cooling have drawn much attention due to their extraordinary performance. In this study, a numerical model of turbine endwall with jet impingement and film cooling was established and validated against the experimental results. To investigate the effects of geometric parameters related with this cooling scheme, four parameters including impingement hole-to-hole pitch Pi, impingement hole diameter Di, impingement channel height H, film hole diamete Df, were selected to adjust within a reasonable range. The uniform design method was used to collect a database that represented the design space formed by the four parameters. Performance criterions including area-averaged overall cooling effectiveness, standard deviation of overall cooling effectiveness, total pressure drop coefficient of the cooling system were evaluated through CFD calculations. To explore and exploit the design space as much as possible, a Kriging surrogate model was built from the database. Analysis of variance (ANOVA) was conducted based upon the surrogate model to investigate the main effect of each parameter and the correlation between parameters. Finally, based upon the knowledge obtained from ANOVA, typical designs were selected from the database which yielded either best or poorest performances. Through detailed analysis of flow and heat transfer mechanisms of these typical designs, the influence of each parameter was illustrated clearly and suggestions for the design of similar cooling schemes were drawn.
Analysis of Failed Startup Sequence of a Single Spool Turbojet Engine
Authors: Sekar T. Chandra , Sundararaj Ramraj H. , Arora Rajat , Kushari Abhijit 
Published: January 2021

Abstract
During the static testing of a single spool turbojet engine (400 N Titan Engine) running on Jet A-1 as fuel, the starting sequence was unsuccessful, however, upon substituting the fuel with Diesel the engine started successfully. Till that point, the engine operation/performance was normal, and a series of tests were conducted for a total time of 5 hours. These 5 hours of testing spanned over five months during which ambient temperature varied from 5 °C to 37 °C, and relative humidity varied from 40% to 90%. The starting sequence was unsuccessful at the maximum ambient temperature (37 °C) and moderate relative humidity condition (50%). During the test, various parameters including pressure, temperature, rotor speed and mass flow rate were measured and recorded using a computer based data acquisition. For the failed start-up case, during the starting sequence, a sudden decrease in rotor speed was observed as the rotor reached ∼80% of the calibration value followed by flameout in combustion chamber. This sudden drop in rotor speed occurred due to mild-surge in compressor which continued up to flameout. The cause of mild-surge is attributed to the momentary blockage at the exit of the compressor caused by the combustion process. These pressure fluctuations propagated downstream leading to flame out. The combination of high ambient temperature (35 °C) and moderate humidity (∼50%) resulted in higher combustion chamber temperature which resulted in the momentary blockage at compressor exit during the transient operation. The substitution of Diesel as fuel resulted in lower combustion chamber temperature, and resolved the issue. It is important to note that, the mild-surge observed in this case is caused by downstream condition, and would occur only at some special situations (inlet conditions). Hence, it may be concluded, that the compressor surge in a jet engine may be caused by downstream components (under some special conditions), and design modifications to these downstream components may resolve the issue in those cases.
Experimental and Numerical Study of an Open Impeller Centrifugal Compressor Stage Utilising 3D Diffuser End Wall Contouring for Operating Range Extension
Authors: Hermann Daniel , Wirsum Manfred , Robinson Douglas , Jenny Philipp 
Published: January 2021

Abstract
Highly efficient and concurrent flexible operation are heavy demands on today’s centrifugal compressor units. Diffuser end wall contouring is a measure to delay the incipience of instability and therefore to extend the compressor’s operating range while maintaining efficient performance. In the presented paper, a hubside wall contouring, applied in the vaneless space upstream the diffuser’s leading edge and within the diffuser passage of a state-of-the-art centrifugal compressor with an open impeller is examined. CFD computations are performed for both a baseline diffuser design with parallel channel walls and the hub-side wall contoured diffuser design. Comparisons of characteristic and diffuser stability decisive flow variables are made in perpendicular sections along an extrapolated camber line of the diffuser vane for full span, near shroud and near hub wall. In operating points near the stability limit at two different stage Mach numbers, the stabilizing effect of the hub-side wall contouring on the diffuser flow is clearly shown. In a scale-model test rig, experimental data including pneumatic 5-hole probe data for a full diffuser blade-to-blade passage, static wall pressures at various planes as well as total temperature was measured. The experimental data is utilized for validation of the presented numerical calculations. The flow stabilizing effect of the hub-wall contouring is clearly visible in the measurements, which showed 8% range extension at highest stage Mach number Mu2 = 1.16 and a range extension of 2% at design stage Mach number Mu2 = 1.0.
Large-Eddy Simulation of Film Cooling Performance Enhancement Using Vortex Generator and Semi-Sphere
Authors: Wang Wen , Cui Jiahuan , Qu Shaoxing 
Published: January 2021

Abstract
Film cooling is an essential cooling method to prevent high-pressure turbine blade from melting down due to the high inlet temperature. In order to improve the film cooling efficiency, several flow control methods have been proposed. In this paper, large-eddy simulations are performed to study the effectiveness of a vortex generator (VG) and a semi-sphere installed downstream of the cooling jet. Before the detailed analyses, the numerical framework is validated against the available experimental data. Both the laminar and turbulent approaching boundary layers are considered. The turbulent boundary layer is generated by a numerical plasma actuator. After validation, the influence of VG and semi-sphere on the film cooling efficiency at various blowing ratios are analyzed. It is found that a counter-rotating vortex pair (CVP) is formed downstream and its strength increases with the blowing ratio in the configuration without VG/semi-sphere. When the VG is installed, it produces another vortex pair that rotates in the reverse direction of the CVP, which reduces the CVP strength and increases the lateral diffusion of the coolant. As a result, the film cooling efficiency is greatly improved, especially at a higher blowing ratio. For the case with a semi-sphere, the film cooling efficiency is also improved, especially at low–medium blowing ratios. However, it is not as effective as the VG in terms of enhancing cooling efficiency. In addition, the total pressure loss is calculated to examine the aerodynamic penalty associated with the VG and semi-sphere. It is found that the total pressure loss increased by only 1% due to the VG or semi-sphere, within the range of blowing ratio investigated in the current study. Considering the overall performance and the feasibility of being applied in practice, a semi-sphere installed downstream of the cooling hole is a promising method to improve the cooling efficiency.
Analysis of Design, Off-Design and Annual Performance of Supercritical CO2 Cycles for CSP Applications
Authors: Thanganadar Dhinesh , Fornarelli Francesco , Camporeale Sergio , Asfand Faisal , Patchigolla Kumar 
Published: January 2021

Abstract
Supercritical carbon dioxide (sCO2) cycles are studied as the next-generation power cycles in order to reduce the cost of Concentrating Solar Power (CSP) plants. The design performance of numerous cycles has been investigated, nevertheless, the off-design and annual performance of these cycles are seldom studied. This plays a critical role in selecting an optimal cycle for CSP application, as an efficient power cycle influences the solar field size, consequently affecting the Levelised cost of electricity (LCOE). In this study, the design, off-design and annual performance of three sCO2 cycles; simple recuperative, recompression and partial-cooling cycles are studied. Multi-objective optimisation was performed and the off-design Pareto fronts were compared for the changes in the power cycle boundary conditions. Annual performance simulation was carried out, and the performance of the three cycles was compared when the power cycle is operated in maximum efficiency mode, which facilitates selecting the optimal cycle. The LCOE of the simple recuperated cycle was higher by roughly 1.7¢/kWh than recompression cycle when maximising the power cycle efficiency and the partial cooling cycle is higher by 0.2¢/kWh. However, operating the power cycle in the maximum efficiency mode significantly lowers the plant capacity factor (around 10–20%).
Application of Uncertainty Quantification Methods to the Prediction of Effusion Cooled Combustor Liner Temperature
Authors: Gamannossi Andrea , Amerini Alberto , Poggiali Matteo , Elmi Carlo Alberto , Mazzei Lorenzo , Andreini Antonio 
Published: January 2021

Abstract
As far as the preliminary thermal design of gas turbine components is concerned, 1-D codes are still widely used in standard industrial practice. Among the different components, the combustor is one of the most critical ones and its thermal design still greatly affects the reliability and life of the entire engine. During the initial phases of the design process, parameters are often roughly known. For this preliminary phase, a low-order approach is preferred instead of a high-fidelity simulation: the exploration of the whole space is extremely important to better understand the behavior of the system and to focus on the design objectives. Uncertainty quantification (UQ) methods, mainly developed in recent years and applied in many fields, are useful tools for the preliminary design phase and provide support during the whole design process. The objective of this work is to estimate the main sources of uncertainties in the design phase of an aeroengine effusion cooled combustor. The test case is based on a full annular lean-burn combustor, tested during the LEMCOTEC (Low EMissions COre-engine TEChnologies) European project. Among the test points investigated in the experimental campaign, the Approach condition is here analyzed. The inner liner is taken into consideration to investigate the metal temperature. Therm-1D, a 1-D in-house simulation code, is used to model the combustor and the open-source tool DAKOTA is adopted for the uncertainty quantification analysis. The baseline case of the combustor is studied and several uncertainty analyses are investigated. They are divided into 3 main groups: geometrical, tuning modelling parameters and thermal loads. For each group, the most relevant parameters are considered as a source of input uncertainty. In particular, a classical Monte Carlo approach is compared with four innovative polynomial-chaos approaches for each group: Gauss quadrature, total order with LHS sampling, stochastic collocation, and Smolyak. The analyses proved how the last two methods give the best results with a sensible lower amount of simulation (depending on the number of input variables). Lastly, results are compared with experimental data to achieve a better understanding of the most relevant input parameters and the propagation of their uncertainty on the results.
A Friction-Enhanced Tuned Ring Damper for Bladed Disks
Authors: Lupini Andrea , Epureanu Bogdan I. 
Published: January 2021

Abstract
This paper introduces a new type of damper for turbomachinery blisks. The major pitfalls of the damper concepts currently employed are two: the low level of relative motion that is available at the damper attachment location, and the inability to control the preload at the frictional interface. To address these issues, the proposed damper is designed as a tuned vibration absorber, which allows energy transfer from the blades to the damper provided that the natural frequency of the damper is close to that of the host structure. Thanks to the enhanced energy transfer, the damper can experience increased relative motion. Frictional contacts are then included to dissipate the energy transferred to the damper. The control of the contact preload is also important, as the centrifugal loads acting on the damper are extremely large and could result in the damper being stuck in its groove and not dissipating energy. These two requirements result in competing priorities. The damper structure must be stiff enough to withstand centrifugal loading without affecting the preload too much. However, it also must be compliant to make sure that its natural frequencies can match the ones of the host structure. For this reason, the proposed damper involves a complex geometry that is stiff in the radial direction and softer in the circumferential direction, which is the direction of the relative motion. A model of the damper is created to damp the vibration of a realistic blisk based on the NASA Rotor 67. The effectiveness of the damper is investigated using high fidelity finite element models. Due to the nonlinear nature of the contact, the equations of motion are solved using harmonic balance, and the size of the (linear part of the) system is reduced using Craig-Bampton component mode synthesis. The frequency response of the system is obtained to analyze the effectiveness of the proposed design. Preliminary results show the potential of this technology for structures with such low damping.
Implementation of Hole-Pair in Ramp to Improve Film Cooling Effectiveness on a Plain Surface
Authors: Hussain Sadam , Yan Xin 
Published: January 2021

Abstract
Film cooling is one of the most critical technologies in modern gas turbine engine to protect the high temperature components from erosion. It allows gas turbines to operate above the thermal limits of blade materials by providing the protective cooling film layer on outer surfaces of blade against hot gases. To get a higher film cooling effect on plain surface, current study proposes a novel strategy with the implementation of hole-pair into ramp. To gain the film cooling effectiveness on the plain surface, RANS equations combined with k-ω turbulence model were solved with the commercial CFD solver ANSYS CFX11.0. In the numerical simulations, the density ratio (DR) is fixed at 1.6, and the film cooling effect on plain surface with different configurations (i.e. with only cooling hole, with only ramp, and with hole-pair in ramp) were numerically investigated at three blowing ratios M = 0.25, 0.5, and 0.75. The results show that the configuration with Hole-Pair in Ramp (HPR) upstream the cooling hole has a positive effect on film cooling enhancement on plain surface, especially along the spanwise direction. Compared with the baseline configuration, i.e. plain surface with cylindrical hole, the laterally-averaged film cooling effectiveness on plain surface with HPR is increased by 18%, while the laterally-averaged film cooling effectiveness on plain surface with only ramp is increased by 8% at M = 0.5. As the blowing ratio M increases from 0.25 to 0.75, the laterally-averaged film cooling effectiveness on plain surface with HPR is kept on increasing. At higher blowing ratio M = 0.75, film cooling effectiveness on plain surface with HPR is about 19% higher than the configuration with only ramp.