bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and functional responses in sun spurge (Euphorbia helioscopia L.) against post‐emergence herbicides in wheat (Triticum aestivum L.)
Authors: Iftikhar Mishal , Ahmad Iftikhar , Hameed Mansoor , Fatima Sana , Ahmad Farooq , Ashraf Muhammad , Nazish Zoya , Ahmad Muhammad Sajid Aqeel , Muneeb Ahmad 
Published: January 2021

AbstractWe investigated changes in plant morphology, anatomy and physiology in a commonly occurring weed, Euphorbia helioscopia L. due to exposure to post‐emergence herbicides. Weed plants were sprayed with one of the following herbicides: pyrimidinyl sulphonylharnstoffe (PS), tribenuron‐methyl (TM), fluroxypyr‐methyl tribenuron‐methyl (FMTM) and bromoxynil (Br). The PS treatment significantly decreased plant height, promoted initiation of side branches and induced a prostrate habit. A specific response of root anatomy to PS and Br treatments was the high proportion of storage parenchyma. The Br‐treated plants showed thickest roots with a significantly large storage parenchyma, not only in the central portion of roots, but also in the cortical parenchyma outside the vascular tissue. A high proportion of xylem in the central portion of roots in the TM or FMTM‐treated plants provides a strong survival response in E. helioscopia. Disintegration of stem cortical parenchyma is the most prominent response of E. helioscopia when treated with a herbicide like PS or FMTM. Survival against these herbicides relates to a complete ring of vascular bundles and intact cortical parenchyma outside the vascular tissue. Increased leaf thickness was recorded in most of the cases except in the FMTM‐treated plants. The PS‐treated plants showed midrib thickness with two distinct vascular bundles. The cortical region, however, was found to be damaged by tissue collapse forming a large lysigenous aerenchyma. Euphorbia helioscopia had altered morphology, anatomy and physiology in response to herbicide application, which changed its growth in the field. To achieve control of this weed species, alternative strategies or higher doses of herbicide should be applied. Further research is required to determine the interaction of surviving weed plants with the crop.
Heat Transfer Due to Thermoelastic Wave Propagation in a Porous Rod
Authors: Singh Baljeet 
Published: January 2021

Abstract
This paper investigates the propagation of thermoelastic waves in a homogeneous, linear, and isotropic porous solid. For physical and mathematical simplicity, one-dimensional wave propagation in a porous solid rod is considered to explain the concept of heat transfer caused by motion. The solutions of governing equations show that the transfer of heat in a porous rod is not only due to the conduction but also produced by the local particle displacement phenomenon. It is observed that the time-averaged transfer of heat depends on the circular frequency, porosity, thermal conductivity, thermal relaxation, specific heat, and other material coefficients.
Modeling of Residual Stresses After Shot Peening and the Effect of Accounting Their Influence on the Stress State of Turbine Blade Fir Tree Roots
Authors: Vasilyev Boris , Zhukov Nikita , Kiselev Igor , Selivanov Alexander 
Published: January 2021

Abstract
Numerical modeling approaches have been developed for simulating shot peening processes and consideration of compressive residual stresses when performing strength calculations of turbine wheel joints.
A three-stage method is presented to combine strength analyses of turbine blade with the output of LS-DYNA simulations (RS diagrams) of multiple impacts. Predictions of RS distributions obtained using the suggested approach are compared with experimental data and good correlation was achieved. The effect of the RS diagrams obtained using various SP parameters on the stress-strain state of the turbine blade root and the values of its cyclic durability are estimated.
Blade Damping Mechanisms and Some Recent Failures
Authors: Gowreesan Vamadevan , Guzman Armando , Greaves Wayne 
Published: January 2021

Abstract
The rotating blades of a steam turbine perform the important task of converting the thermal energy of the steam into rotating mechanical work or torque. Hence, these blades have to be very robust and they need to be installed properly in the discs of the turbine. Damping mechanisms are used to improve the stiffness of the blades and to minimize the vibrations of the blades. Different types of blade damping mechanisms are used in steam turbines. Shroud bands, lashing or damping wires, pins, tie-bolts and lashing stubs/ snubbers are the most common types of damping mechanisms used in steam turbines. Several factors such as stress distribution, additional centrifugal stresses due to the added weight of the damping mechanisms, aerodynamic effects, resulting harmful mode shapes and critical vibration frequencies etc., need to be considered in the selection and the design of the damping mechanisms.
Due to the various types of operating conditions and stresses, the damping mechanisms can experience failure in service. Metallurgical evaluations of some of the recent failures of damping mechanisms are discussed here. Failures of shroud bands, blade tenons, tie-bolts and damping wires are the particular examples presented. SCC (stress corrosion cracking), fatigue and overload were found to be the main modes of failures in these examples. The purpose of discussing these examples is to make the designers, the manufacturers and the users aware of these potential issues so that corrective actions can be taken.
On the Probabilistic Endurance Prediction Approach for Turbomachinery Blades and Vanes
Authors: Kulkarni Davendu Y. , Peng Caetano 
Published: January 2021

Abstract
The design and aeromechanical assessment of turbomachinery blades and vanes comprises a wide range of complex processes that tend to be based on conventional deterministic methods. These processes often provide a ‘snapshot’ evaluation of the new component designs at the nominal operating conditions. While the deterministic methods can predict the high cycle fatigue (HCF) endurance with reasonable accuracy; they assume that the conservative safety factors applied to cover for the parametric variations, uncertainties and unknowns will not change during the product life cycle. This approach is intended to be conservative and in some cases may overlook the lack of robustness.
The present paper proposes a robust design analysis approach based on probabilistic methodology for the aeromechanical assessment of rotor blades and stator vanes of turbomachinery. The robust design approach can account explicitly for the effects of design and manufacturing variability. This methodology can reduce the levels of conservatism in the deterministic approach and can provide a more thorough risk assessment.
This paper offers a generalised aeromechanical analysis formulation based on probabilistic methods to evaluate the HCF capability of turbomachinery components. Herein, this methodology is demonstrated by using a typical stator vane of an aero engine compressor and it is based on Monte-Carlo and DOE simulations. The methodology consists of parametric sensitivity studies and identification of the most influential parameters that control the HCF endurance. Future ideas and roadmap of the aeromechanical probabilistic analysis capability development are also discussed.
New Numerical Analysis Method for Creep Lifetime of Gas Turbine Materials by Using the Discrete Cosine Transform
Authors: Hiraguchi Hideo 
Published: January 2021

Abstract
Recently the Discrete Cosine Transform[1], [2], [3] which is a modified Fourier Transform has begun to be used to express coefficients of creep equations using the power law or the exponential law such as Bailey-Norton law[4], [5] and θ Projection[6], [7], [8], [9], [10]. In addition, the Discrete Cosine Transform has begun to be used to express a creep equation itself. We have already found that the Discrete Cosine Transform can express the temperature and stress dependence property of the coefficients of the creep equations at the same time by the two-dimensional Discrete Cosine Transform using 8 × 8 discrete signals[11]. Furthermore, we have already found that the Discrete Cosine Transform can fit measured creep strain values very well from the primary creep region to the tertiary creep region using 8 discrete signals and it can estimate creep strain values between the measured points by interpolation very well[12]. However it has not been known if the Discrete Cosine Transform can predict the long term creep curve by using the short term creep data yet. Therefore, as a next stage, we tried to estimate the long term creep curve from the short term creep data of gas turbine materials by extrapolation using the Discrete Cosine Transform. As a result, we were able to obtain a useful numerical analysis method by utilizing the Discrete Cosine Transform Coefficients and others as a new extrapolation method. It is found that this new numerical method would be able to predict the configuration of 150,000-hour creep curve by using 500-hour to 13,000-hour short term creep data.
Heat Transfer of Impinging Jet-Row Onto Trapezoidal Channel With Different Effusion and Discharge Conditions
Authors: Chang Shyy Woei , Chiang Pei-An , Cai Wei Ling 
Published: January 2021

Abstract
The heat transfer performances of the trapezoidal channel with the impinging row jets normal to the channel apex wall with no effusion and three effusion conditions from one, two and three rows of bleeding holes along the channel apex, or, and, channel sidewalls were studied. At each effusion condition, the airflow extraction from the channel tip were regulated as full open conditions, and 0% (full close), 5%, 10% of the total airflow rate fed into the trapezoidal channel via the impinging row jets. For each effusion and discharge condition, the full-field heat transfer data over the channel apex and sidewalls were measured at channel Reynolds numbers of 5000, 7500, 10000, 12500 and 15000 using the steady-state infrared thermography method. The corresponding axial distributions of the jet mass flow rate at each effusion and discharge condition were measured at all the Reynolds numbers tested. While the crossflow and channel flow confinement significantly affected the axial distribution of the jet flow rate for the channel without effusion, the impact of effusion and discharge conditions on the distribution of the airflow rate through the row jet was negligible for the effusion channels. Without effusion, the strong crossflow effects acted with the weakened jet momentums near the sealed channel hub to substantially reduce the regional heat transfer rates. With effusion, the flow confinement formulated by the cavity-like channel hub and the crossflow developed along the test channel were significantly suppressed, leading to the even distribution of jet flow and the recovered impinging-jet heat transfer properties over the channel hub region. The preferential heat transfer performances among the present test channels with and without effusion gave rise to the channel with three rows of effusion holes. Relative to the heat transfer impacts caused by varying the row number of the effusion holes, the impacts of tip extraction were less evident; but the overall heat transfer performance was improved by reducing tip discharge. With leading-edge cooling applications to a gas turbine blade, three sets of heat transfer correlations that evaluated the regionally averaged Nusselt numbers over the channel apex and side walls with and without effusions at various tip extractions were devised.
LM9000 Passive Clearance Control (PCC)
Authors: Marchetti Simone , Nappini Duccio , De Prosperis Roberto , Di Sisto Paolo 
Published: January 2021

Abstract
This paper describes the design of the Free Power Turbine (FPT) of the LM9000, in particularly the design of its Passive Clearance Control (PCC) system.
The LM9000 is the aero-derivative version of the GE90-115B jet engine. Its core engine has many common parts with the GE90; what differs is the booster (low pressure compressor) and the lower pressure turbine (LPT).
The booster of the LM9000 is without fan because the engine is not used to provide thrust but torque only, subsequently it has a new flow path [5].
The LPT has instead been replaced by an intermediate pressure turbine (IPT) and by the FPT. The IPT drives the booster, while the FPT is a free low-pressure turbine designed for both power generation and mechanical drive industrial applications, including LNG production plants.
Due to its different application, the LM9000 FPT flow path differs sensibly from the GE90 LPT, however as the GE90 it is provided of a clearance control system that cools the casing in order to reduce its radial deflection.
It is not the first time that a clearance control system has been used in industrial applications; in GE aero-derivative power turbines is already present in the LM6000 and LMS100.
Design constraints, system complexity, high environment variability because the PCC is located outside the GT, harsh environments and long periods of usage still make the design of this component challenging.
The design of the PCC has been supported by extensive heat transfer and mechanical simulations. Each PCC component has been addressed with a dedicated life calculation and all the blade and seal clearances have been estimated for all the operating conditions of the engine. Simulations have been validated by an extensive test campaign performed on the first engine.
Effects of Inlet Guide Vanes on the Performance and Stability of an Aeronautical Centrifugal Compressor
Authors: Poujol Nicolas , Trébinjac Isabelle , Duquesne Pierre 
Published: January 2021

Abstract
A research centrifugal compressor stage designed and built by Safran Helicopter Engines is tested at 3 IGV (Inlet Guide Vanes) stagger angles. The compressor stage includes 4 blade rows: axial inlet guide vanes, a backswept splittered impeller, a splittered vaned radial diffuser and axial outlet guide vanes. The methodology for calculating the performance is detailed, including the consideration of humidity in order to minimize errors related in particular to operating atmospheric conditions.
The shift of the surge line towards lower mass flow rate as the IGV stagger angle increases highly depends on the rotation speed. The surge line shift is very small at low rotation speeds whereas it significantly increases at high rotation speeds. A firstorder stability analysis of the impeller and diffuser subcomponents shows that the diffuser (resp. impeller) is the first unstable component at low (resp. high) rotation speeds. This situation is unaltered by increasing the IGV stagger angle.
At low rotation speeds below a given mass flow rate, rotating instabilities at the impeller inlet are detected at zero IGV stagger angle. Their occurrence is conditioned by the relative flow angle at the tip of the leading edge of the impeller. As the IGV stagger angle increases, the mass flow decreases to maintain a given inlet flow angle. Therefore, the onset of the rotating instabilities is delayed towards lower mass flow rates.
At high rotation speeds, the absolute flow angle at the diffuser inlet near surge decreases as the IGV stagger angle increases. As a result, the flow is highly alternate over two adjacent channels of the radial diffuser beyond the surge line at IGV stagger angle of 0°.
On the Leakage and Dynamic Force Coefficients of a Novel Stepped Shaft Pocket Damper Seal: Experimental and Numerical Verification
Authors: Yang Jing , San Andrés Luis , Lu Xueliang 
Published: January 2021

Abstract
High performance turbomachinery favors annular seals with a large damping coefficient to ensure rotor system stability. Pocket damper seals (PDSs), a variation of labyrinth seals with axial blades (ribs) and adding circumferential partition walls (ridges), produce a favorable damping performance. To further enhance the damping characteristic and reduce leakage, a novel stepped shaft PDS is hereby introduced. The invention has a unique arrangement of steps on the rotor surface, each facing an upstream rib in a pocket row. Thus, the step and a blade tip form a tight clearance (c1), while the rotor surface and the downstream blade tip make a larger clearance (c2). The convergence-divergence variation of cross-section areas along the flow direction increases the PDS damping coefficient. To validate the performance of the novel design, a stepped shaft PDS (c1/c2 = 0.5) with four axial ribs and eight circumferential pockets is built and tested. A comprehensive investigation, experimental and computational, produces the seal leakage and dynamic force coefficients for the stepped shaft PDS, as well as similar performance characteristics for an identical PDS with a smooth rotor surface (c1/c2 = 1, i.e., a uniform clearance PDS). The stepped shaft PDS operates with air at supply pressure (PS) ranging from 1.1 bar to 3.2 bar. The measured leakage for the stepped shaft PDS is 50% of that for the uniform clearance PDS. Computational fluid dynamics (CFD) and bulk flow model (BFM) predictions of leakage agree well with the test data. For PS = 2.3 bar, the test damping coefficient (C) for the stepped shaft PDS is ∼ 1.5 times greater than the one for the uniform clearance PDS. With an increase in PS to 3.2 bar, the stepped shaft PDS shows a two and one half increase in damping coefficient. In comparison to the test data, a CFD model over estimates C by 29% for operation at PS = 3.2 bar, though capturing the variation trend versus whirl frequency. The BFM largely under predicts C for the stepped shaft PDS and is abandoned for future work. Both the test data and CFD predictions demonstrate the superior damping performance of the stepped shaft PDS, thus providing a novel alternative seal configuration for turbomachinery usage.
High Pressure Optical Measurements of Temperature at Turbine Rotor Inlet Conditions
Authors: Egbert Scott C. , Zeltner Darrel , Rezasoltani Mohsen , Tree Dale R. 
Published: January 2021

Abstract
The measurement of combustion product gas temperature is valuable for the development and control of many combustion systems. In gas turbine engines, measurement of the rotor inlet temperature remains particularly challenging because of harsh operating conditions and limited access. The Integrated Spectral Band Ratio (ISBR) method is a non-intrusive optical emission gas temperature measurement technique suitable for this application. Optical fibers made of sapphire were used to transmit the radiative signal from the post combustion zone to a Fourier Transform Infrared (FTIR) spectrometer without the need for probe cooling. The ratio of spectral bands of H2O, nominally 100 cm−1 wide between 4600 and 6200 cm−1 were used to infer temperature. ISBR and thermocouple measurements were obtained during two temperature sweeps; one at high load and one at low load (pressures of 1.2 and 0.7MPa, respectively). The average of three thermocouples 76 mm downstream of the ISBR measurements were consistently on the order of 200 K lower, consistent with a radiative correction and the heat loss between the two measurements. The change in ISBR temperature (95 K) during the sweep was similar to the change in average thermocouple temperature (89 K). Repeatability of the optical measurement at a given operating condition was on the order of ± 15 K and the absolute uncertainty of a single ISBR temperature measurement was estimated to be ± 61 K. A linear correlation with an R-squared value of 0.97 was also found between raw optical signal and thermocouple measurements suggesting that once a calibrated measurement is obtained, changes in gas temperature can be determined using a correlation of the raw signal to produce the temperature.
Experimental Investigation of the Performance of H-Darrieus Wind Turbines With Tubercle Leading Edge Blades
Authors: Du Longhuan , Dominy Robert G. , Ingram Grant 
Published: January 2021

Abstract
The most significant challenge associated with employing small-scale H-Darrieus wind turbines is to ensure that they self-start without compromising their efficiency at the design operating condition. One of the key and straightforward methods to improve the turbine performance is to choose an optimized blade profile. It has been shown that by creating rounded protuberances (tubercles) around the blade leading edge, not only do the blades demonstrate a more gradual stall characteristic but also that the tubercles significantly increase the blade lift performance in the post-stall regime at the expense of slightly degraded lift performance in the pre-stall regime. This effect might be beneficial for the H-Darrieus turbine application where the blades experience extreme incidence range during the turbine start-up period. Therefore, in this study the performance of standard NACA0021 blades is compared experimentally to a modified set of blades which have a sinusoidal tubercle configuration along the original NACA0021 blade leading edge (0 ≤ x ≤ 0.3c). Time-accurate, self-starting data were recorded from wind tunnel tests under different flow conditions and the power coefficient (Cp) versus tip speed ratio (λ) curve was calculated. It is demonstrated conclusively that blades with an appropriate configuration of tubercle leading edges can considerably improve turbine self-starting capability. To the best of the authors’ knowledge, this study provides the first experimental data of H-Darrieus wind turbine performance with tubercle leading edge blades and the data are valuable for future designs and for the validation of simulation models.
Wall-Resolved Large-Eddy Simulation of the LS89 Cascade Using an Explicit Local Time-Stepping Method
Authors: Martin Benjamin , Duchaine Florent , Gicquel Laurent , Odier Nicolas , Dombard Jérôme 
Published: January 2021

Abstract
In most turbomachinery CFD simulations, a large heterogenity of mesh refinement exists because specific flow regions are known to require small cell sizes for proper prediction. This leads to large cell volume ratios between the smallest and largest cells. In the context of explicit solvers where the timestep is imposed by stability constraints and smallest cell size, large difference in cell sizes may directly lead to a waste of CPU time since this timestep is much smaller than required in the majority of cells. The introduction of a Local Time-Stepping (LTS) is a potential solution to such an observation. The computational domain is divided in multiple sub-domains and each sub-domain will meet its local stability constraints, relaxing the limit of maximal allowed timesteps. In the following, this technique is applied to a wall-resolved Large-Eddy Simulation (LES) of the LS89 turbine vane cascade dividing the domain in two parts: one part containing the near-wall region of the blade (with prism layers at the blade surface leading to a small timestep) and a second part composed of the remaining volume. To evaluate the strategy, a standard wall-resolved simulation and its LTS counterpart are compared to experimental data. Overall, for the LS89 configuration that is known as challenging, there is an excellent agreement between simulations and experiment. More importantly, a 31% speedup is achieved on this configuration while giving identical results when comparing the single domain and the LTS cases despite the significant simulation cost reduction for the latter.