bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improving Characteristics of a Cooled Transonic Vane of Low Pressure Turbine Under Nonuniform Inlet Conditions
Authors: Granovskiy A. V. , Afanasiev I. V. , Kostege V. K. , Marchukov E. Yu. 
Published: January 2021

Abstract
Vanes of low-pressure turbines (LPT) run under inlet conditions generated by a preceding high-pressure turbine (HPT). HP stages are generally cooled and transonic as well due to the large pressure ratio necessary to reduce the gas temperature upstream of the downstream stages. Therefore radial distributions of inlet flow angle, total pressure and total temperature at the boundary upstream of the LPT are highly non–uniform. Such non-uniform inlet conditions can result in enhanced level of the total losses including the secondary losses. Moreover, vanes of LPT have meridional openings along inner and outer boundaries of the flow path, which causes intensification of the secondary flows leading to an increase in secondary losses. In this case the special meridional contouring of the vanes’ outer and inner surfaces allows a decrease in the flare angle namely meridional opening in the rear part of the vane. In this work, in order to compensate the negative effect of non-uniform inlet conditions, meridional opening and low aspect ratio, 3D profiling of the vane row is used as a way of reducing secondary losses. Some variants of LPT vanes with various complex 3D shapes are investigated. In particular, vane variants with a “reversed bow”, a “bowed” and a “lean” in the circumferential direction have been examined. Significant modification of the vane row is limited by cooling system design, which has to incorporate a deflector in the inner hollow of the vane to improve cooling effectiveness. A compromise between aerodynamic quality and cooling limitations has been achieved.
Benefit and Critical Factors for the Performance of the Boundary Layer Ingesting Propulsion
Authors: Lee B. J. , Liou May-Fun , Celestina Mark , To Waiming 
Published: January 2021

Abstract
The benefit of the boundary layer ingestion (BLI) is described in the perspective of the propulsion and engine development. A power saving map of the BLI engines is derived based on the correlation of the wake velocity ratio of the ingested boundary layer profile and the propulsive efficiency. The ratio of the mass flow rate between BLI and non-BLI propulsors is introduced to quantify the power saving of the BLI engine relative to a clean inlet flow engine which generates same amount of thrust. The wake recovery factor from the jet flow out of the BLI engine is employed to find an adequate sizing of the BLI engine for the given design requirement. The effects of the fan pressure ratio on the power saving are also investigated to explore the feasible range of the BLI engine design. The derived correlation is validated with CFD analyses. A numerical experiment is carried out by varying the wake velocity ratio through different BLI engines sized with respect to an influencing body. Consequently, the propulsor efficiency is quantified and presented by the saving in the actual shaft power. The efficiency penalty, pressure ratio of the BLI fan stage are correlated with the power saving and the correlation is validated through BLI2DTF and R4 fan stage CFD analyses based on rig test data.
Experimental Study of Vaneless Diffuser Rotating Stall Development and Cell Merging Phenomena
Authors: Grapow Filip , Olasek Krzysztof , Liśkiewicz Grzegorz , Magiera Radomir , Kryłłowicz Władysław 
Published: January 2021

Abstract
This paper describes the vaneless diffuser rotating stall (VDRS) development and cell merging phenomena. A centrifugal compressor’s lifespan may be limited by flow instabilities occurring in off-design operation. One such instability is the VDRS, which generates oscillating, asymmetrical flow fields in the diffuser and, thus, undesired forces acting on the rotor. Understanding and prevention of VDRS behavior is crucial for achieving safe and undisturbed compressor operation.
Experimental measurements of centrifugal compressors operating under the influence of VDRS have been presented. Two different approaches were used for the identification of VDRS: pressure measurements and 2D PIV. Frequency analysis based on spectral maps and cell development processes were investigated.
The presented results showed that mass flow rate has an impact on the rotating frequency of both the entire structure and single cells. Additionally, it affects radial cell size, which grows with compressor throttling and ultimately reaches the length of the diffuser. During the experiments, the cell merging phenomenon was observed which has not been widely described in the literature.
The results presented in this paper allow better understanding of vaneless diffuser rotating stall behavior. The phenomenon of the change of cell size and frequency could be very important for machine fatigue. Cell merging could also have an impact on the machine’s vibrations and flow stability. Since it is believed that VDRS is one of the factors inducing surge, its understanding and prevention may have positive influence on surge margins.
Fatigue of an Advanced SiC/SiC Ceramic Matrix Composite With an Environmental Barrier Coating at Elevated Temperature in Air and in Steam
Authors: Williams T. M. , Ruggles-Wrenn M. B. 
Published: January 2021

Abstract
Uniaxial tension-tension fatigue performance of a SiC/SiC composite with an ytterbium-disilicate environmental barrier coating (EBC) was investigated at 1200°C in laboratory air and in steam. The composite is reinforced with Hi-Nicalon™ SiC fibers and has a melt-infiltrated matrix processed by chemical vapor infiltration of SiC followed by infiltration with SiC particulate slurry and molten Si. The EBC consists of a Si bond coat and an ytterbium disilicate (Yb2Si2O7) top coat applied via air plasma spraying (APS). Basic tensile properties of the EBC/SiC/SiC composite were evaluated at 1200°C. Tension-tension fatigue was examined for maximum stresses of 110–140 MPa in air and in steam. To assess the efficacy of the EBC, experimental results obtained for the coated composite are compared to those obtained for a control composite without the EBC. Surface grit-blasting inherent in the EBC application process degrades tensile strength of the composite. However, the EBC effectively protects the composite from oxidation embrittlement during cyclic loading in air or in steam. Fatigue runout defined as survival of 200,000 cycles (55.6 h at a frequency of 1.0 Hz) was achieved at 110 MPa in air and in steam. The retained properties of pre-fatigued specimens were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated. Damage and failure of the EBC/SiC/SiC composite are attributed to growth of cracks originating from numerous processing defects (voids) present in the composite interior.
Correlation Between Engine and Aircraft Loadings for Several Mission Types
Authors: Templalexis Ioannis , Lionis Ioannis , Kitinos Sotiris 
Published: January 2021

Abstract
Fighter aircraft constitutes a well-defined class of aircraft. Their extensive use on a daily basis by operators stands as a strong motive behind studies that concern their rate of “exhaustion ”. For an aircraft operator either civil or military, it is very important at any point in time to have a clear view of the engines’ and the aircrafts’ operating condition. This is valuable information in order to foresee undesired incidences and in order to schedule missions in accordance to the actual and anticipated maintenance needs. For the latter, the operator would also need to know the rate of the engine and the aircraft life consumption per mission.
The current study concerns the F-16 Block 52M aircraft, powered by the Pratt and Whitney F100-PW-229 engine. Aircraft is continuously subjected to crack growth mechanisms while flying. On the other hand, engines also go through Low Cycle Fatigue (LCF) cycles and creep prominent conditions while being in operation. The engine and the aircraft structural condition are continuously monitored, based on real time data recordings. To the extent of the authors’ knowledge, that is a common practice for most F-16 users. However, what was found to be missing from the international literature was a study to quantify any potential correlation between the aircraft loading and the engine loading for all typical mission types an aircraft of this type undertakes. For users that have already installed an aircraft loading monitoring system like “Aircraft Structural Integrity Program” (ASIP) it would be very useful to set a “rule of thumb” aside regarding the degree of correlation between aircraft and engine loading.
Engine life consumption rate was estimated based on the creep and LCF failure mechanisms applied on the most critical engine section, the turbine. Engine recordings were picked from an arbitrary sample of 200 flights of a certain aircraft, wherein most typical mission types could be found. Turbine and subsequently blade temperature as well as blade stress were calculated using a very narrow time step. These data along with blade material data were fed in the Larson Miller model, to set an algorithm for estimating life consumption due to creep. Engine Total Accumulated Cycles (TACs) which account for LCF loading, are directly measured by the engine recorder, based on an embedded algorithm.
Aircraft loading is calculated based on the accelerations the aircraft structures encounter during flight. These are also recorded under a very narrow time step.
Last step was the correlation of the engine life consumption against the aircrafts’ loading for typical mission types. Scatter diagrams and statistical measures were used, in order to define the degree of correlation between them.
The Influence of Turbulence and Reynolds Number on Multiple Slot Film Cooling Over the Suction Surface
Authors: Soma L. W. , Ames F. E. , Acharya S. 
Published: January 2021

Abstract
Developing robust film cooling protection on the suction surface of a vane is critical to managing the high heat loads which exist there. Suction surface film cooling often produces high levels of film cooling but can be influenced by secondary flows and some dissipation due to free-stream turbulence. Directly downstream from suction surface film cooling, heat loads are often significantly mitigated and internal cooling levels can be modest. One thermodynamically efficient way to cool the suction surface of a vane is with a counter cooling scheme. This combined internal/external cooling method moves cooling air in a direction opposite to the external flow through an internal convection array. The coolant is then discharged upstream where the high level of film cooling can offset the reduced cooling potential of the spent cooling air.
The present suction surface film cooling arrangement combines a slot film cooling discharge on the near suction surface from an incremental impingement cooling method with a second from a counter cooling section. A second counter cooling section is added further downstream on the suction surface. The internal cooling plenums replicate the geometry of the cooling methods to ensure the fluid dynamics of the flow discharging from the slots are representative of the actual internal cooling geometry. These film cooling flows have been tested at blowing ratios of 0.5 and 1.0 for the initial slot and blowing ratios of 0.15 and 0.3 for the two downstream slots. The measurements have been taken at exit chord Reynolds numbers of 500,000, 1,000,000, and 2,000,000 with inlet turbulence levels ranging from 0.7% to 12.6%. Film cooling effectiveness measurements were acquired using both thermocouples and infrared thermography. The infrared thermography shows the influence of secondary flows on film cooling coverage near the suction surface endwall junction. The film cooling effectiveness results at varied blowing ratios, turbulence levels and Reynolds numbers document the impact of these major variables on suction surface slot film cooling. The results provide a consistent picture of the slot film cooling for the present three slot arrangement on the suction surface and they support the development of an advanced double wall cooling method.
Recuperator Performance Assessment in Humidified Micro Gas Turbine Applications Using Experimental Data Extended With Preliminary Support Vector Regression Model Analysis
Authors: De Paepe Ward , Pappa Alessio , Coppitters Diederik , Montero Carrerro Marina , Tsirikoglou Panagiotis , Contino Francesco 
Published: January 2021

Abstract
Cycle humidification applied to micro Gas Turbines (mGTs) offers a solution to overcome their limited operational flexibility in terms of variable electrical and thermal power production when used in a Combined Heat and Power (CHP) application. Although the positive impact of this cycle humidification on the performance has already been proven numerically and experimentally, very detailed modeling of the system performance remains challenging, especially the determination of the recuperator effectiveness, which has the highest impact on the final cycle performance. Indeed, the recuperator performance depends strongly on the mass flow rate of the air stream and its humidification level, two parameters that are difficult to measure accurately. Accurate modeling of the recuperator performance under both dry and humidified conditions is thus essential for correct assessment of the potential of humidified mGT cycles in Decentralized Energy Systems (DES).
In this paper, we present a detailed analysis of the recuperator performance under humidified conditions using averaged experimental data, extended with the application of a Support Vector Regression (SVR) on a time series to improve noise-modeling of the output signal, and thus enhance the accuracy of the monitoring process. In a first step, the missing experimental parameters, air mass flow rate and humidity level, were obtained indirectly, using rotational speed, fuel flow rate, exhaust gas composition and pressure level measurements in combination with the compressor map. Despite the low accuracy, some general trends regarding the recuperator performance could be observed based on these experimental data, indicating that the recuperator, despite having an increased total exchanged heat flux, is actually too small to exploit the full potential of the humidification. In a second step, by means of the SVR model, a first attempt was made to improve the accuracy and reduce the scatter on the recuperator performance determination. The predicted results with the SVR indicated indeed a reduced scatter on the determinations of the air mass flow rate and the amount of introduced water, opening a pathway towards online recuperator performance prediction.
Matching of Synchronous Motors and Centrifugal Compressors: Oil and Gas Industry Practice
Authors: Taher Matt , Ristanovic Dragan , Meher-Homji Cyrus , Pillai Pradeep 
Published: January 2021

Abstract
Synchronous motor driven centrifugal compressors are widely used in the oil and gas industry. In evaluating the optimum selection of synchronous motor drivers for centrifugal compressors, it is important to understand the factors influencing a proper match for a centrifugal compressor and its synchronous motor driver. The buyer should specify process requirements and define possible operating scenarios for the entire life of the motor driven centrifugal compressor train. The compressor designer will use the buyer-specified process conditions to model the aerothermodynamic behavior of the compressor and characterize its performance. Performance, controllability, starting capabilities as well as the optimum power margin required for a future-oriented design must also be considered. This paper reviews the criteria for evaluating the optimal combination of a centrifugal compressor and its synchronous motor driver as an integral package. It also addresses API standard requirements on synchronous motor driven centrifugal compressors. Design considerations for optimal selection and proper sizing of compressor drivers include large starting torque requirements to enable compressor start from settle-out conditions and to prevent flaring are addressed. Start-up capabilities of the motor driver can significantly impact the reliability and operability of the compressor train. API 617 on centrifugal compressors refers to API 546 for synchronous motor drivers. In this paper, requirements of API 617 and 546 are reviewed and several important design and sizing requirements are presented. In the effort to optimize plant design, and maintain the performance requirements, the paper discusses optimization options, such as direct on-line starting method to explore the motor rating limits, and the use of synchronous motors for power factor correction to eliminate or reduce the need for reactive power compensation by capacitor banks. This paper presents a novel approach to show constant reactive power lines on traditional V curves. It also complements capability curves of synchronous motors with lines of constant efficiency. The paper discusses variable frequency drive options currently used for synchronous motors in compressor applications. The paper addresses the available variable frequency drive types, their impact on the electrical grid, and motor design considerations with a view to summarizing factors important to the selection of variable frequency drives.
Dynamic Model Based Identification of Cavitation Compliance and Mass Flow Gain Factor in Rocket Engine Turbopump Inducers
Authors: Wan Y. , Manfredi M. , Pasini A. , Spakovszky Z. 
Published: January 2021

Abstract
Cavitation dynamics continue to pose a significant risk in the development and operation of launch vehicle (LV) propulsion systems. In addition to generating unsteady loads that can directly damage turbopump hardware, cavitation dynamics often couple with LV fluid feed systems, producing system wide POGO instability that can cause catastrophic failures. Despite its importance, the current understanding of cavitation dynamics, and especially pump transfer matrices, is limited. Given the relatively sparse amount of inducer transfer matrix data available, there is a critical need for more in-depth characterization of the cavitation dynamics in turbopump inducers to avoid POGO instability. This paper defines and validates a new reduced-order approach to infer key parameters such as cavitation compliance, K, and mass flow gain factor, M, from simple, single sensor unsteady pressure measurements during inducer inlet pressure ramps. The utility of this approach is demonstrated for a range of inducer geometries reported in the literature. The results are in agreement with experimental data and the paper provides a new capability supporting the assessment of launch vehicle POGO instability.
A Novel Controlled-Motion Test Rig to Evaluate Effect of Synchronous and Subsynchronous Lateral Vibration on Reliability and Performance of Mechanical Seals in Pumps
Authors: Norrbin Clay S. , Delgado Adolfo 
Published: January 2021

Abstract
Mechanical seals are commonly used in rotating machinery to contain liquid leakage past a rotating shaft. Pumps vibration often exhibit both synchronous and sub-synchronous whirling, which may lead to premature failure of mechanical seals. A test rig was developed to simulate a running pump environment for the mechanical seal. The controlled-motion test rig comprises a flexibly-mounted-rotor connected to a pair of electrohydraulic shakers. This configuration allows imposing whirl orbits to a flexibly-mounted-rotor (FMR) mechanical seal at any prescribed frequency independent of rotor speed. A 6-axis load cell provides direct measurements of the reaction forces at the mechanical seal stationary component. Five Eddy current sensors and capacity probes track the 5 DOFs of the mechanical seal dynamic face. The flow loop is a modified plan 54 with an external pump capable of delivering 32 lpm at 14 bar using VG 2 mineral oil, and an external heat exchanger to regulate oil temperature. Tests were performed on a 3-inch (76.2 mm) FMR seal. Input rotor whirl vibration was increased to 10 mils pk-pk (254 microns), while cooling flow (VG2 mineral oil) was set to 8 lpm and pressure was varied from 1.7–6.9 lpm. The measurements include steady state values of temperature, power loss, clearance and leakage; and dynamic measurements of seal face wobble, wobble-imposed torque, relative lateral movement and fluid film shear.
Partial Premixing Effects on the Reacting Jet of a High Pressure Axially Staged Combustor
Authors: Genova Tommy , Otero Michelle , Reyes Jonathan , Ahmed Kareem , Martin Scott 
Published: January 2021

Abstract
The effects of partial premixing on a reacting jet-in-crossflow is investigated in a five atmosphere axially staged combustor at stationary gas turbine relevant conditions. The facility consists of a dump style headend burner that provides a crossflow with a quasi-uniform velocity and temperature profile to the axial stage to isolate the effects of the jet-in-crossflow. The headend burner is run with methane and air at a lean equivalence ratio to match industry emissions standards. For the current work,, the total air to the headend and axial stage is kept constant, and fuel is split between the headend and axial stage to represent different gas turbine loading conditions. For the cases analyzed, the fuel split to the axial stage went up to 25%. The axial stage consists of an optically accessible test section with a coaxial injector that provides variability to how long the methane and air can mix before entering the facility. Three different premixed levels are studied: fully premixed, non-premixed, and partially premixed. The flow-field characteristics of the reacting jet-in-crossflow are analyzed using particle image velocimetry (PIV), and flame behavior is quantified by employing CH* chemiluminescence. NO measurements are made at the exit of the facility using a Horiba emissions analyzer. Two different flames are observed: flames that burn in the leeward recirculation region and flames that burn at the core of the jet.
The Influence of Wake Chopping on Wet-Steam Turbine Modelling
Authors: Vasilj Andrej , Schuster Sebastian , White Alexander 
Published: January 2021

Abstract
The formation of water droplets within condensing steam turbines is a complex process that occurs at supersaturated, non-equilibrium conditions and is influenced by the unsteady segmentation of blade wakes by successive blade rows. This is often referred to as ‘wake chopping’, and its effect on the condensation process is the subject of this paper. The practical significance is that thermodynamic ‘wetness losses’ (which constitute a major fraction of the overall loss) are strongly affected by droplet size. Likewise, droplet deposition and the various ensuing two-phase phenomena (such as film migration and coarse-water formation) also depend on the spectrum of droplet sizes in the primary fog.
The majority of wake-chopping models presented in the literature adopt a stochastic approach, whereby large numbers of fluid particles are tracked through (some representation of) the turbine flowfield, assigning a random number at each successive blade row to represent the particle’s pitchwise location, and hence its level of dissipation. This study contributes to the existing literature by adding: (a) a comprehensive study of the sensitivity to key model parameters (e.g., blade wake shape and wake decay rate); (b) an assessment of the impact of circumferential pressure variations; (c) a study of the implications for wetness losses and (d) a study of the implications for deposition rates.