bluuebunny/crossref_metadata_2025_split huggingface dataset:
Considerations for the Extension of Gas Path Analysis To Electrified Aircraft Propulsion Systems
Authors: Simon Donald L. , Thomas Randy , Dunlap Kyle M. 
Published: September 2021

Abstract
Aircraft operators rely on gas path analysis techniques for monitoring the performance and health of their gas turbine engine assets. This is accomplished by analyzing discernable shifts in measurement parameters acquired from the engine. This paper reviews the founding mathematical principles of gas path analysis, including conventional approaches applied for estimating engine performance deterioration. Considerations for extending the application of gas path analysis techniques to Electrified Aircraft Propulsion (EAP) systems is also discussed, and simulated results from their application to an EAP concept comprised of turbomachinery and electrical system hardware is provided. Results are provided comparing the parameter estimation accuracy offered by taking a whole-system approach towards the problem setup versus that offered by analyzing each subsystem individually. For the latter, the importance of having accurate direct or inferred measurements of external mechanical torque loads placed upon turbomachinery shafts is emphasized.
Importance of Non-Equilibrium Modelling for Compressors
Authors: Spencer Robert , Przytarski Pawel , Adami Paolo , Grothe Patrick , Wheeler Andrew 
Published: September 2021

Abstract
This paper investigates the importance of non-equilibrium boundary layer modelling for three compressor blade geometries, using RANS and high fidelity simulations. We find that capturing non-equilibrium effects in RANS is crucial to capturing the correct boundary-layer loss. This is because the production of turbulence within the non-equilibrium region affects both the loss generation in the non-equilibrium region, but also the final equilibrium state. We show that capturing the correct non-equilibrium behaviour is possible by adapting industry standard models (in this case the k-omega SST model). We show that for the range of cases studied here, non-equilibrium effects can modify the trailing-edge momentum thickness by up to 40 percent, and can change the trailing-edge shape factor from 1.8 to 2.1.
Hydrogen Blending Into Ansaldo Energia AE94.3A Gas Turbine: High Pressure Tests, Field Experience and Modelling Considerations
Authors: Ciani A. , Tay-Wo-Chong L. , Amato A. , Bertolotto E. , Spataro G. 
Published: September 2021

Abstract
Fuel flexibility in gas turbine development has become increasingly important and modern engines need to cope with a broad variety of fuels. The target to operate power plants with hydrogen-based fuels and low emissions will be of paramount importance in a future focusing on electric power decarbonization.
Ansaldo Energia AE94.3A engine acquired broad experience with operation of various natural gas and hydrogen fuel blends, starting in 2006 in the Brindisi (Italy) power plant. Based on the exhaustive experience acquired in the field, this paper describes the latest advancements characterizing the operation of the AE94.3A burner with high pressure combustion tests adding hydrogen blends ranging from 0 to 40% in volume. The interpretation of the test results is supported by reactive and non-reactive simulations describing the effects of varying fuel reactivity on the flame structure as well as the impact of fuel / air momentum flux ratio on the fuel / air interaction and fuel distribution in the combustion chamber.
As expected, increasing amounts of hydrogen in the fuel are also associated with higher amounts of NOx production, however this effect could be countered by optimization of the fuel staging strategy, based on the mentioned CFD considerations and feedback from high pressure tests.
Analysis of LES and 1D Hot-Wire Data to Determine Actively Generated Main Flow Turbulence in a Film Cooling Test Rig
Authors: Fischer Lukas , Straußwald Michael , Pfitzner Michael 
Published: September 2021

Abstract
A vortex generator was incorporated into a wind tunnel to investigate more realistic inflow conditions for film cooling test rigs. The flow field signals are sampled numerically by probes in LES simulations and experimentally by using 1D hot-wire measurements to determine turbulence quantities. The LES shows that the turbulence is anisotropic which cannot be detected by the 1D hot-wire. Furthermore, the integral length scale which shall provide insight into the sizes of the turbulent eddies is determined using two approaches. The first uses the one probe at two times correlation method and could be evaluated from the numerical and experimental probes. The second correlation method exploits the spatial resolution in the LES domain by using the two probes at one time approach. Both methods show combustor-like turbulence length scales downstream of the vortex generator if the triple decomposition is applied onto the velocity signal.
Effects of Surface Waviness on Fan Blade Boundary Layer Transition and Profile Loss — Part I: Methodology and Computational Results
Authors: Lee Jinwook , Spakovszky Zoltán S. , Greitzer Edward M. , Drela Mark , Talbotec Jérôme 
Published: September 2021

Abstract
This two-part paper describes a new approach to determine the effect of surface waviness, arising from manufacture of composite fan blades, on transition onset location movement and hence fan profile losses. The approach includes analysis and computations of unsteady disturbances in boundary layers over a wavy surface, assessed and supported by wind tunnel measurements of these disturbances and the transition location. An integrated framework is developed for analysis of surface waviness effects on natural transition. The framework, referred to as the extended eN method, traces the evolution of disturbance energy transfer in flow over a wavy surface, from external acoustic noise through exponential growth of Tollmien-Schlichting (TS) waves, to the start and end of the transition process. The computational results show that surface waviness affects the transition onset location due to the interaction between the surface waviness and the TS boundary layer instability, and that the interaction is strongest when the geometric and TS wavelengths match. The condition at which this occurs, and the initial amplitude of the boundary layer disturbances that grow to create the transition onset is maximized, is called receptivity amplification. The results provide first-of-a-kind descriptions of the mechanism for the changes in transition onset location as well as quantitative calculations for the effects of surface waviness on fan performance due to changes in surface wavelength, surface wave amplitude, and the location at which the waviness is initiated on the fan blade.
Detection of Machinery Failure Signs From Big Time-Series Data Obtained by Flow Simulation of Intermediate-Pressure Steam Turbines
Authors: Komatsu Kazuhiko , Miyazawa Hironori , Yiran Cheng , Sato Masayuki , Furusawa Takashi , Yamamoto Satoru , Kobayashi Hiroaki 
Published: September 2021

Abstract
The periodic maintenance, repair, and overhaul (MRO) of turbine blades in thermal power plants are essential to maintain a stable power supply. During MRO, older and less-efficient power plants are put into operation, which results in wastage of additional fuels. Such a situation forces thermal power plants to work under off-design conditions. Moreover, such an operation accelerates blade deterioration, which may lead to sudden failure. Therefore, a method for avoiding unexpected failures needs to be developed. To detect the signs of machinery failures, the analysis of time-series data is required. However, data for various blade conditions must be collected from actual operating steam turbines. Further, obtaining abnormal or failure data is difficult. Thus, this paper proposes a classification approach to analyze big time-series data alternatively collected from numerical results. The time-series data from various normal and abnormal cases of actual intermediate-pressure steam-turbine operation were obtained through numerical simulation. Thereafter, useful features were extracted and classified using K-means clustering to judge whether the turbine is operating normally or abnormally. The experimental results indicate that the status of the blade can be appropriately classified. By checking data from real turbine blades using our classification results, the status of these blades can be estimated. Thus, this approach can help decide on the appropriate timing for MRO.
Spark Ignition of SPP Injector Under Sub-Atmospheric Conditions
Authors: Zhao Qianpeng , Mu Yong , Yang Jinhu , Wang Yulan , Xu Gang 
Published: September 2021

Abstract
The sub-atmospheric ignition performance of an SPP (Stratified Partially Premixed) injector and combustor is investigated experimentally on the high-altitude test facility. In order to explore the influence of sub-atmospheric pressure on reignition performance and flame propagation mode, experiments are conducted under different pressures ranging from 19 kPa to 101 kPa. The inlet temperature and pressure drop of the injector (ΔPsw/P3t) are kept constant at 303 K and 3% respectively. The transparent quartz window mounted on the sidewall of the model combustor provides optical access of flame signals. Ignition fuel-air ratio (FAR) under different inlet pressures are experimentally acquired. The spark ignition processes, including the formation of flame kernel, the flame development and stabilization are recorded by a high-speed camera at a rate of 5kHz. Experimental results indicate that the minimum ignition FAR grows rapidly as the inlet air pressure decreases. An algorithm is developed to track the trajectory of flame kernels within 25ms following the spark during its breakup and motion processes. Results show that the calculated trajectory provides a clear description of the flame evolution process. Under different inlet air pressures, the propagation trajectories of flame kernels share similarities in initial phase. It is pivotal for a successful ignition that the initial flame kernel keeps enough intensity and moves into CTRZ (Center-Toroidal Recirculation Zone) along radial direction. Finally, the time-averaged non-reacting flow field under inlet pressure of 54kPa and fuel mass flow of 8kg/h is simulated. The effects of flow structure and fuel spatial distribution on kernel propagation and flame evolution are analyzed.
Effect of Bladed Packets on Transient Vibration Localization Behaviors of Mistuned Whole Bladed Disk System
Authors: Kan Xuanen 
Published: September 2021

Abstract
The multi-packets whole bladed disks are usually used in the turbo-machineries. The most different characteristic of the multi-packets whole bladed disk is that some blades are connected by lacing forming a bladed packet, and several bladed packets are assembled to form a multi-packets whole bladed disk system. Mistuning of blades is an attractive vibration subject due to vibration localization problems that vibration energy focuses on some blades. The vibration localization characteristics of steady state of bladed disk are mainly discussed in previous studies, and few works focus on the transient vibration localization behaviors of the multi-packets whole mistuned bladed disk. Transient vibration characteristics of bladed disk are crucial during startup. Therefore, in this paper, transient vibration characteristics of the multi-packets whole bladed disk are studied. A developed mathematical model is used to calculate the transient vibration response of the multi-packets whole bladed disk. The number of bladed packets on the transient vibration localization of the multi-packets mistuned whole bladed disk is discussed. The results indicate that the bladed packets are able to reduce the transient vibration localization. The results suggest that the bladed packet is an alternative approach to reduce the vibration localization of bladed disk caused by mistuning. Moreover, the different number of bladed packets will produce various behaviors of transient vibration localization of multi-packets whole mistuned bladed disk system.
Study of CFD-Based Raised-Floor Data Center Cooling With Parametric CRAC Turbofan Blower Airflow Patterns
Authors: Song Zhihang , Chen Wan 
Published: September 2021

Abstract
Commonly encountered thermal management challenges of today’s rapidly changing power density, raised-floor hot/cold aisle data centers include typically uncontrollable tile flow non-uniformity along the above-floor cold aisle. For example, the operational cooling provision intensity near the Computer Room Airflow Conditioner (CRAC) unit can be far less than that on the other side (far away from the CRAC unit). This undesired trend leads to an unbalanced aisle-level air cooling and subsequent inefficient power consumption. In this study, the CRAC turbofan blower flow boundary conditions were thoroughly investigated. Computational Fluid Dynamics (CFD) based simulations were employed to describe and evaluate the differently configured CRAC turbofan blower flow conditions (i.e., normal, angled, and sheared CRAC flow patterns) as well as their impacts upon the air cooling performance. This work indicates that the considered turbofan blower boundary condition, together with their underlying transportation mechanism within the plenum, might contribute an essential influence to the flow structure adjacent to the tile perforations. In particular, it was found that the sheared CRAC turbofan blower airflow pattern is capable of giving rise to favorable tile flow straightening manners. This finding further promotes an improvement of the consequently obtained aisle-level air cooling effectiveness and efficiencies, contributing to more advanced data center thermal management in the future.
Structural Integrity of Serrated Leading Edge Guide Vane Blades for Noise Reduction
Authors: Cuciumita Cleopatra , Qin Ning , Stanley Felix , Shahpar Shahrokh 
Published: September 2021

Abstract
One of the major noise sources of high bypass ratios modern turbofan engines arises from the interaction between the turbulent rotor wake, the tip-leakage and the leading edge of the downstream outlet guide vanes. Recent research has confirmed that leading edge serrations are an effective passive control for reducing noise. However, for transferring serrated leading edges to modern, environmentally friendly aero engines, the bypass outlet guide vanes must fulfil both aerodynamic and structural requirements. The current study aims at characterizing the structural behaviour when adding serrations to the leading edge of bypass outlet guide vanes designed for a configuration without classical struts.
It was found that the structural performances deteriorate with increasing number of serrations, directly related to the serrations wavelength, and with their amplitude. The buckling loading factor decreases and the total deformation increases constantly with the increase of both parameters. The presence of the troughs of the serrations introduce stress concentrators. For large enough values of either the wave length or amplitude of the serrations, the maximum von Mises stress increases significantly, and can as much as double in value. At the same time, the location of the maximum stress on the vane moves from its original position, on the leading edge of the casing fillet, to the troughs of the serrations.
Progress in Using Liquid Bio-Fuels in DLE Industrial Gas Turbines
Authors: Saxena Priyank , Steele William C. , Cowell Luke H. 
Published: September 2021

Abstract
Decarbonization of electricity is paramount for the success of curbing growth of greenhouse gas emissions in the atmosphere. For many power generation applications there is a growing interest in using bio-fuels to replace fossils-based fuels, such as diesel and natural gas. Bio-fuels, being plant-based fuels, are classified as carbon neutral fuels. Several distributed power generation sites, such as universities, are interested in the feasibility of burning bio-fuels, such as biodiesel and alcohols, in stationary gas turbines to reduce their carbon-footprint as well as earn tax credits. In order to maintain its leadership in fuel-flexibility and to support its distributed power generation customers, Solar has qualified several of its gas turbine models using both the conventional and dry low emissions (DLE) combustion systems on various biodiesel blends. This paper presents results of the combustion rig tests with DLE combustion injectors using biodiesel blends and their comparison with those of No. 2 diesel and natural gas fuels. The emissions (NOx, CO, UHC) from B20 biodiesel blend were similar to that of ULSD, but higher than natural gas. The results are summarized in terms of gas turbines emissions and performance. Impacts of fuel properties on storage, handling and gas turbines operations are discussed. Finally, future development opportunities are also presented.
Comparison of Compressor Performance Map Predictions to Test Data for a Supercritical Carbon Dioxide Brayton Power System
Authors: Clementoni Eric 
Published: September 2021

Abstract
Supercritical carbon dioxide (sCO2) Brayton power cycles are typically designed to operate with compressor inlet conditions near the critical point to take advantage of the high density of the fluid at these conditions. While designing the cycle to operate here improves cycle efficiency, it also creates challenges for designing the compressor and predicting off-design compressor performance due to real gas fluid properties near the critical point. Multiple compressor performance map evaluation methodologies which incorporate real gas corrections have been proposed in literature with only limited evaluation of the accuracy of these methods compared to operational data from compressors designed for sCO2 power cycles. This paper evaluates compressor performance from the 100 kWe Integrated System Test (IST), which was operated at the Naval Nuclear Laboratory, over a range of compressor inlet conditions and rotational speeds relative to one real gas performance map correction methodology and assesses the impact of additional terms proposed in literature for improving the accuracy of off-design performance predictions.
A Computationally Efficient Method That Predicts Light-Around for Both Gas- and Liquid-Fueled Combustion
Authors: Meeks Ellen , Naik Chitralkumar V. , Litrico Giuliana , Rida Samir 
Published: September 2021

Abstract
Controlling light-around and re-light presents design challenges for gas-turbine manufacturers. Researchers have studied the detailed phenomena in laboratory experiments to elucidate controlling factors and modes of behavior. Several groups have reported high-fidelity simulations of the fluid dynamics, turbulent mixing and light-around phenomena using large eddy simulations (LES) on highly refined computational meshes. While such simulations can reproduce experimental observations, they are computationally expensive and tend to be impractical for routine design analyses. In this work, we present a less computationally intensive CFD approach, which has been tested against laboratory experiments using both gaseous-fuel injections and liquid-fuel injections. Results show that a consistent practice of mesh and model settings can be used for all the test cases considered. The simulations generate light-around sequences and total-ignition times that agree well with experimental measurements. Observed trends are predicted when varying burner spacing as well as the fuel and injection method.
Measurements to Quantify the Effect of a Reduced Flow Rate on the Performance of a Tilting Pad Journal Bearing (LBP) With Flooded Ends
Authors: San Andrés Luis , Toner Jonathan , Alcantar Andy 
Published: September 2021

Abstract
Operation of tilting pad journal bearings (TPJBs) with a reduced flow decreases pumping costs and oil sump storage. A low supplied oil flow improves system energy efficiency by reducing drag power losses, albeit the temperature rise in both the bearing pads and the lubricating oil become a concern. This paper presents measurements of the static and dynamic load performance of a flooded ends TPJB lubricated with an ISO VG 46 oil supplied at 60 °C, and with flowrate ranging from 150% to just ∼5% of a nominal supply condition. The flow range covers both over-flooded and starved flow conditions. The test bearing is a four-pad, 102 mm diameter, center pivot, with single orifice feeds, and configured with end seals to flood the bearing housing. The experiments include operation at two shaft speeds = 6 krpm and 12 krpm (= 64 m/s surface speed) and under three specific loads = 0.345 MPa, 1.03 MPa and 2.07 MPa applied in between pads (LBP). The measurements show the bearing drag power loss decreases by nearly 20% when the flow rate drops to 50% of nominal. However, halving the flow produces a raise in pad subsurface temperatures, ∼7 °C for operation at 12 krpm. Flow reduction below 50% does result in even more substantial power savings; however, it also produces too hot pad temperatures that approach 130 °C, a known limit for Babbitt material safe operation. The bearing static eccentricity (e) and direct stiffnesses Kxx &lt; Kyy (load direction) do not show a significant dependency on the supplied flow, either above or below the nominal condition. A minor stiffness hardening does occur for very low flow conditions, 5% or so of nominal. Damping coefficients (Cxx ∼ Cyy) decrease by ∼30% as the flow rate decreases from 150% to just a few % of nominal flow. The experimental results are first to quantify operation of a TPJB supplied with minute amounts of lubricant flow. A test with a very low flow rate at ∼2% of nominal and under a light load produced the emergence of a broadband subsynchronous vibration frequency, albeit with very small amplitude.
Influence of Disc Modes and Sideband Excitations on the Mistuned Forced Response Behaviour of an Embedded Compressor Rotor
Authors: Hegde Shreyas , Madden Andrew , Kielb Robert 
Published: September 2021

Abstract
This paper focusses on predicting the mistuned forced response behavior of an embedded compressor rotor blade row in a 3.5 stage axial compressor. The authors in previous papers studied the multi-row influence on the forcing function for multiple operating conditions. For these investigations CFX was utilized to predict the forcing However, in the mistuned predictions a consistent underprediction of the amplification factor was noted A previous investigation by the authors [32] considered an isolated mode family. The current work considers the same configuration but looks at a non-isolated mode family which is in a frequency “veering” region. Also, since the mistuning code was formulated on the lines of the fundamental mistuning model (FMM) the model only included a single DOF per ND and hence modes in the veering region were not modeled. The current paper addresses both these shortcomings and talks about the influence of sideband travelling wave excitations at the HL operating condition (the details of the mistuned predictions at the PE operating condition can be found in [32]). The paper also talks in detail about the effect of modelling the disc modes individually using the FMM model as well as together using the component mistuning model (CMM) as present in ANSYS Mechanical. Key conclusions are: 1) The mistuned response tends to be amplified by all cases including the sideband excitations, 2) The coupled influence of including a disc mode in the FMM model and sideband excitations is dependent on the proximity of the mode to the blade alone frequency, 3) Although the CMM model predicts the peak of the response accurately, it does not offer any substantial advantage over the FMM model given the computational cost required for the CMM prediction. Also, the prediction is highly sensitive to the frequency of the individual modes that can differ between codes.