bluuebunny/crossref_metadata_2025_split huggingface dataset:
Film Cooling Effectiveness Enhancement Using Multi-Longitudinal Vortex Generated by Alternating Elliptical Film Holes
Authors: Xiao Kun , He Juan , Feng Zhenping 
Published: September 2021

Abstract
This paper proposed an alternating elliptical film hole for gas turbine blade to restrain kidney vortex and enhance film cooling effectiveness, based on the multi-longitudinal vortexes generated in alternating elliptical tube. The detailed flow structures in film hole delivering tube and out of the film hole, adiabatic film cooling effectiveness distributions as well as the total pressure loss coefficient were investigated. The delivering tube of alternating elliptical film hole consists of two straight sections and a transition section. In the straight sections, the cross section of the film hole is elliptical, and in the transition section, along flow direction, the major axis gradually shortened into the minor axis, and the minor axis gradually expanded to the major axis. But, the cross-section area of the film hole kept constant.
Numerical simulations were performed by using 3D steady flow solver of Reynolds-averaged Navier-Stokes equations (RANS) with the SST k-ω turbulence model. To reveal the mechanism of kidney vortex suppression and film cooling effectiveness enhancement, the simulation results were compared with the cylindrical film hole set as the baseline at different mass flow ratios (MFR). Besides, the aerodynamic characteristics of these two kinds of film holes were also investigated. The results showed that obvious jet effect could be found in the cylindrical film hole, and the coolant mainly flowed along the upper wind wall, then interacted with the main flow, forming a strong kidney vortex after flowing out, which made the coolant to lift away from the wall surface and reduced the cooling effectiveness. The alternating elliptical film hole had a good inhibition impact on the jet effect in the hole due to the longitudinal vortices, which made the film adhere to the wall surface better after the coolant flowed out. The longitudinal vortices generated by alternating elliptical film hole have the opposite rotation direction to the vorticity of the kidney vortices, thus the kidney vortices were restrained to a certain extent. The height of kidney vortices is lower, and the size of kidney vortices is also smaller. As a result, the film cooling effectiveness of alternating elliptical film hole is distinctly higher than that of the cylindrical film hole, and the enhancement effect is more significant at higher mass flow ratio. In addition, the total pressure loss coefficient of alternating elliptical film hole is only slightly higher than the cylindrical film hole at the mass flow ratio of 1%, 2% and 3%, and is even lower at the mass flow ratio of 4%, thus inducing an excellent comprehensive performance.
Simultaneous Optimization of Mistuned Bladed Disks for Forced and Self-Excited Vibration Considering Amount of Unbalance
Authors: Kaneko Yasutomo , Watanabe Toshio , Furukawa Tatsuya 
Published: September 2021

Abstract
Actual bladed disks with small variations are called mistuned systems. Many researchers suggest that mistuning, although negatively affecting the forced response, has a beneficial (stabilizing) effect on blade flutter (self-excited vibration). Therefore, in blade design, a bladed disk must be optimized for forced vibration and blade flutter. We proposed a simultaneous optimization method of bladed disks for forced and self-excited vibration, considering the amount of unbalance that causes rotor vibration. This method uses alternate mistuning to suppress the blade flutter. We measured the natural frequency and weight of all the blades of a disk, as in the traditional development process. Then, we assembled a mistuned system retaining the alternate mistuning, and generated analysis models based on the measured natural frequencies and weights of the blades. Finally, we analyzed the resonant stress and the amount of unbalance in the mistuned system repeatedly, sorting the blades and retaining the alternate mistuning of the disk. The simultaneous optimal solution was explored by MCS or DDE (Genetic algorithm). To reduce the computational time, we used the reduced order model FMM to calculate the resonant stress and the stability of the mistuned bladed disks. Further, we verified the validity of the proposed method by applying it to a mistuned bladed disk of a steam turbine.
A Discrete Element Methods-Based Model for Particulate Deposition and Rebound in Gas Turbines
Authors: Gaskell Jack G. , McGilvray Matthew , Gillespie David R. H. 
Published: September 2021

Abstract
The secondary air system and cooling passages of gas turbine components are prone to blockage from sand and dust. Prediction of deposition requires accurate models of particle transport and thermo-mechanical interaction with walls. Bounce stick models predict whether a particle will bounce, stick, or shatter upon impact and calculate rebound trajectories if applicable. This paper proposes an explicit bounce stick model that uses analytical solutions of adhesion, plastic deformation and viscoelasticity to time-resolve collision physics. The Discrete-Element Methods (DEM) model shows good agreement when compared to experimental studies of micron and millimetre-scale particle collisions, requiring minimal parametric fitting. Non-physical values mechanical properties, artifices of previous models, are thus eliminated. Further comparison is made to the best resolved and industry standard semi-empirical models available in literature. In addition to coefficients of restitution, other variables crucial to accurately model rebound, for example angular velocity, are predicted. The time-stepping explicit approach allows full coupling between internal processes during contact, and shows that particle deformation and hence viscoelasticity play a significant role in adhesion. Modelling time-dependent internal variables such as wall-normal force create functionality for future modelling of arbitrarily shaped particles, the physics of which has been shown by previous work to differ significantly from that of spheres. To date these effects have not been captured well using by higher-level energy-based models.
A Reduced Order Modeling Approach to Probabilistic Creep-Damage Predictions in Finite Element Analysis
Authors: Hossain Md Abir , Cottingham Jacqueline R. , Stewart Calvin M. 
Published: September 2021

Abstract
This paper introduces a computationally efficient Reduced Order Modeling (ROM) approach for the probabilistic prediction of creep-damage failure. Component-level probabilistic simulations are needed to assess the reliability and safety of high-temperature components. Full-scale probabilistic creep-damage modeling in finite element (FE) approach is computationally expensive requiring many hundreds of simulations to replicate the uncertainty of component failure. To that end, ROM is proposed to minimize the elevated computational cost while controlling the loss of accuracy. It is proposed that full-scale probabilistic simulations can be completed in 1D at a reduced cost, the extremum conditions extracted, and those conditions applied for lower cost 2D/3D probabilistic simulations of components that capture the mean and uncertainty of failure. The probabilistic Sine-hyperbolic (Sinh) model is selected which in previous work was calibrated to alloy 304 stainless steel. The Sinh model includes probability density functions (pdfs) for test condition (stress and temperature), initial damage (i.e., microstructure), and material properties uncertainty. The Sinh model is programmed into ANSYS finite element software using the USERCREEP.F material subroutine. First, the Sinh model and FE code are subject to verification and validation to affirm the accuracy of the simulations. Numerous Monte Carlo simulations are executed in a 1D model to generate probabilistic creep deformation, damage, and rupture data. This data is analyzed and the probabilistic parameters corresponding to extreme creep response are extracted. The ROM concept is applied where only the extreme conditions are applied in the 2D probabilistic prediction of a component. The probabilistic predictions between the 1D and 2D model is compared to assess ROM for creep. The accuracy of the probabilistic prediction employing the ROM approach will potentially reduce the time and cost of simulating complex engineering systems. Future studies will introduce multi-stage Sinh, stochasticity, and spatial uncertainty for improved prediction.
Influence of Hole-to-Hole Interaction on the Acoustic Behavior of Multi-Orifice Perforated Plates
Authors: Javareshkian Alireza , Dancelme Alexis , Chen Hongyu , Sattelmayer Thomas 
Published: September 2021

Abstract
A key factor for developing low-emission combustion systems in modern gas turbines and aero-engines is the acoustic liner’s optimized design. Several models are available in the literature for the acoustic impedance of perforated acoustic liners. Most of these impedance models neglect the interaction effect between the orifices. In practice, the orifices are generally closely distributed such that the interactions between acoustic radiation from neighboring orifices can affect their acoustical behavior. The hole-to-hole interaction effect may change the resonance frequency of the resonator due to the nonplanar wave propagation in the cavity, the orifices in the perforated plate, and the near-wall region in the combustor. Considering this effect may help to predict the resonance frequency of the resonator accurately. In this work, a three-dimensional (3D) analytical approach is developed to account for the nonplanar wave propagation in the cavity and orifices on the perforated plate. The present study employs the proposed 3D analytical method to determine the hole-to-hole interaction end-correction of multi-orifice perforated plates.
Additionally, the hole-to-hole interaction end-correction from a series of perforated plates with different orifice radii and spacings is obtained via the Finite Element Method (FEM). Perforated plate specimens with different center-to-center hole spacing are tested using an impedance tube. Experimental results show that the resonance frequency is shifted towards a lower frequency with decreasing holes’ spacing. The resulting model is compared with the experiments and the end-correction models available in the literature. The comparison shows that the available end-correction models cannot capture the hole-to-hole interaction effect, which is observed in experiments.
In contrast, the proposed model can reproduce measurements with high quality. The resulting model demonstrates that the acoustic end-correction length for orifices is closely related to the perforated plate’s porosity ratio and orifice radius. The proposed model is readily applicable in the design of multi-orifice perforated plates.
Static Performance of Smooth Liquid Annular Seals in the Transition and Turbulent Regimes
Authors: Childs Dara W. , Bullock Joshua 
Published: September 2021

Abstract
Static test results are presented for smooth annular seals with a length-to-diameter ratio of 0.50, radius R = 51.00 mm, at the nominal radial clearance Cr = 0.2032 mm. Tests were conducted for angular shaft speeds; ω = 2, 4, 6, 8 krpm, axial pressure drops; ΔP = 2.1, 4.13, 6.21, 8.27 bars, and eccentricity ratios ϵ0 = e0/Cr = 0.00, 0.27, 0.53, 0.8 where e0 is the static eccentricity. Three pre-swirl inserts were used to target zero, medium, and high (0., 0.4, and 0.8) pre-swirl ratios for a set of pre-determined operating conditions with ISO VG 2 oil at 46.1°C.
Pitot tubes measured the circumferential velocity at separate upstream and downstream seal locations and were used to calculate pre-swirl ratio, PSR = vinlet/Rω, and outlet-swirl ratio, OSR = voutlet/Rω. For all tested pre-swirl inserts, PSR tended to converge to 0.4∼0.5 as ω increased. PSR and OSR were poorly correlated.
Volumetric leakage rate Q ˙ versus pressure differential ΔP was measured. The measured vector Reynolds number Re, combining the axial and circumferential Reynolds numbers ranged from ∼1000 to ∼3500. Based on Zirkelback and San Andrés 1996 publication, almost all of the flow regime is predicted to lie in the transition regime, with fewer points in the turbulent regime.
Generally, the seals’ static centering properties were obtained by applying a static load Fs and measuring the resulting displacement vector e0. At many low-speed, low-ΔP test conditions, the seal would not remain in the desired centered or near-centered position and had to be forced into place with a centering force Fs. The authors believe that the observed de-centering effects resulted from test operations in the transition flow regime where the friction factor λ does not drop with increasing ΔP and increasing Re. A positive centering Lomakin effect requires that λ drop with increasing axial Reynolds number.
The seals had positive centering effects over a large portion of the predicted transition flow regime, supporting the view that the shift from transition-to-turbulent flow regularly occurred at lower Re values than the Re = 3000 boundary used by Zirkleback and San Andrés.
Loss Characterization of Advanced VIGV Configurations With Adjustable Blade Geometry
Authors: Frank Roman G. , Wacker Christian , Niehuis Reinhard 
Published: September 2021

Abstract
Variable inlet guide vanes (VIGV) are the main control element to adjust the flow rate of industrial centrifugal compressors by customized pre-swirl in the inlet plane of the impeller. The efficient working range of VIGVs is however restricted due to open flow separation occurring at critical stagger angles. In order to overcome the narrow limitations of current blade geometries and to enhance the operating range of the compressor, split blades consisting of a separate front and tail blade segment proved to be particularly promising in previous linear-cascade measurements. Each blade segment is thereby individually staggered. This enables a gradual flow deflection along the chord length. Secondary flow losses, however, were not considered in the previous investigations with linear-cascades.
To highlight the potential of the split blade concept under more application-oriented conditions including all relevant flow effects, highly resolved field measurements were conducted in the wake of annular VIGVs. Four different blade configurations, a customary reference case and three variations of the split blade with full, partial and missing sealing in the gap between the segments, were assessed using five-hole probe measurements. By investigating a wide range of stagger angles, the coverage of the full low-loss working range of the VIGV could be ensured. Especially, the fully sealed split blade configuration proved its capacity to extend the efficient operational range significantly.
Sweep Effects on Fan-Intake Aerodynamics at High Angle of Attack
Authors: Mohankumar Ben , Hall Cesare A. , Wilson Mark J. 
Published: September 2021

Abstract
Sweep in a transonic fan is conventionally used to reduce design point losses by inclining the passage shock relative to the incoming flow. However, future low pressure ratio fans operate to lower Mach numbers meaning the role of sweep at cruise is diminished. Instead, sweep might be repurposed to improve the performance of critical high Mach number off-design conditions such as high angle of attack (AOA). In this paper, we use unsteady computational fluid dynamics to compare two transonic low pressure ratio fans, one radially stacked and one highly swept, coupled to a short intake design, at the high AOA flight condition. The AOA considered is 35°, which is sufficient to separate the intake bottom lip.
The midspan of the swept fan was shifted upstream to add positive sweep to the outer span. Based on previous design experience, it was hypothesised the swept fan would reduce transonic losses when operating at high AOA. However, it was found the swept fan increased the rotor loss by 24% relative to the radial fan. Loss was increased through two key mechanisms. i) Rotor choking: flow is redistributed around the intake separation and enters the rotor midspan with high Mach numbers. Sweeping the fan upstream reduced the effective intake length, which increased the inlet relative Mach number and amplified choking losses. ii): Rotor-separation interaction (RSI): the rotor tip experiences low mass flow inside the separation, which increases the pressure rise across the casing to a point where the boundary layer separates. The swept fan diffused the casing streamtube, causing the casing separation to increase in size and persist in the passage for longer. High RSI loss indicated the swept fan was operating closer to the rotating stall point.
Cryogenic Fuel Storage Modelling and Optimisation for Aircraft Applications
Authors: Rompokos Pavlos , Rolt Andrew , Nalianda Devaiah , Sibilli Thierry , Benson Claire 
Published: September 2021

Abstract
Designing commercial aircraft to use liquid hydrogen (LH2) is one way to substantially reduce their life-cycle CO2 emissions. The merits of hydrogen as an aviation fuel have long been recognized, however, the handling of a cryogenic fuel adds complexity to aircraft and engine systems, operations, maintenance and storage. The fuel tanks could account for 8–10% of an aircraft’s operating empty weight, so designing them for the least added weight is of high significance.
This paper describes the heat transfer model developed in the EU Horizon 2020 project that is used to predict heat ingress to a cylindrical tank with hemispherical end caps with external foam insulation. It accounts for heat transfer according to the state of the tank contents, the insulation material properties, the environment, and the dimensions of the tank. The model also estimates the rate of pressure change according to the state of the fuel and the rate at which fuel is withdrawn from the tank. In addition, a methodology is presented, that allows for tank sizing taking into consideration the requirements of a design flight mission, the maximum pressure developed, and the fuel evaporated.
Finally, the study demonstrates how to select optimal insulation material and thickness to provide the lightest design for the cases where no gaseous hydrogen is extracted, and where some hydrogen gas is extracted during cruise, the latter giving gravimetric efficiencies as high as 74%.
CFD Analysis of the Influence of Gas Content on the Rotordynamic Force Coefficients for a Circumferentially Grooved Annular Seal for Multiple Phase Pumps
Authors: Wu Tingcheng , San Andrés Luis , Lu Xueliang 
Published: September 2021

Abstract
Pumping efficiency and rotordynamic stability are paramount to subsea multiphase pump operation since, during the life of a well, the process fluid transitions from a pure liquid to a mixture of gas in liquid to just gas. Circumferentially grooved seals commonly serve as balance pistons in pumps while also restricting secondary flow. Prior experimental results obtained with a grooved seal operating with a mixture of air and mineral oil show the seal rotordynamic force coefficients vary significantly with the gas volume fraction (GVF). This paper, complementing an exhaustive experimental program, presents a computational fluid dynamics (CFD) analysis to predict the leakage, drag power, and dynamic force coefficients of a circumferentially grooved seal supplied with air in oil mixture with a GVF varying from 0 to 0.7. The test seal has fourteen grooves, an overall axial length of 43.6 mm and a radial clearance of 0.211 mm. The 127 mm diameter rotor spins at constant angular speed (Ω = 3,500 rpm). The mixture enters the seal at a supply pressure (Pin) of 2.9 bar(a), and the seal exit pressure (Pout) is 1 bar(a). The CFD two-phase flow simulations utilize the Euler-Euler multiphase model to predict the mass flow rate and the pressure field as a function of the operating conditions. Using a multi-frequency shaft orbit motion method, the CFD simulations deliver the variations of reaction force on the rotor with respect to the excitation frequency. For a pure liquid condition (GVF = 0), both the CFD and experimental results produce constant stiffness, damping and added mass coefficients. The experimental and CFD results demonstrate the seal rotordynamic force coefficients are quite sensitive to the gas volume fraction (GVF). When introducing a small amount of air into the oil (GVF = 0.1), the direct damping coefficient increases by approximately 10%. For operation with a mixture with inlet GVF &gt; 0.1, the cross-coupled stiffness coefficients develop strong frequency dependent characteristics. In contrast, the direct damping coefficient has a negligible variation with excitation frequency. The CFD predictions, as well as the experimental results, evidence that air injection in a liquid stream can significantly change the seal rotordynamic characteristics, and thus can affect the rotordynamic stability of a pump. An accurate CFD analysis thus enables engineers to design reliable grooved seals operating under two-phase flow conditions.
Assessment of Engine Operability and Overall Performance for Parallel Hybrid Electric Propulsion Systems for a Single-Aisle Aircraft
Authors: Kang Sangkeun , Roumeliotis Ioannis , Zhang Jinning , Pachidis Vassilios , Broca Olivier 
Published: September 2021

Abstract
This paper aims to assess the gas turbine operability and overall hybrid electric propulsion system performance for a parallel configuration applied to a 150 passenger single-aisle aircraft. Two arrangements are considered: one where the low pressure shaft is boosted and one where the high pressure shaft is boosted. For identifying limits in the hybridization strategy steady state and transient operation are considered and the hybridization effect on compressor operability is determined.
Having established the electric power on-take limits with respect to gas turbine operation the systems performance at aircraft level is quantified for the relevant cases. Different power management strategies are applied for the two arrangements and for different power degrees of hybridization.
The results indicate that despite the fact that pollutant emission and fuel consumption may improved for hybrid propulsion, this comes at the cost of reduced payload and operability margins. Boosting the low pressure shaft may give the highest engine performance benefits but with a significant weight penalty, while the low pressure compressor system operability is negatively affected. On the other hand boosting the high pressure shaft provides lower engine performance benefits but with smaller weight penalty and with less operability concerns.