bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the Structure of Flow Deflector on Ignition and Flame Shape of The Centrally Staged Combustor
Authors: Ma Jinglong , Hui Xin , Han Xiao , Han Meng 
Published: September 2023

Abstract
Centrally staged premixed is a practical method to reduce NOx emission in aero-engines. Previous research has demonstrated that the flow inside the combustor has a significant effect on the ignition performance and flame shape. In this paper, the local flow field in a model combustor is changed by mounting a flow deflector at the main stage channel outlet. The effect of the length and central angle of the flow deflector on the ignition performance is investigated experimentally. The time scale of each phase of a successful ignition event is extracted using Otsu’s threshold segmentation method. It is found that the flow deflector significantly improves the ignition performance of the centrally-staged combustor and extends the ignition boundary. Based on this, the shape of the flame at different flow deflector lengths and central angles is also captured by a high-speed camera. The spatial patterns of the flame dynamic are identified using the proper orthogonal decomposition (POD) method. Additionally, the first few order modes, whose energy proportions are relatively larger, dominate the flame dynamics. The results indicate that as the length of the flow deflector increases, the flame primarily presents the vortex shedding mode, while as the central angle of the flow deflector decreases, the circumferential rotation mode dominates. There is a greater fluctuation in the zone where the chemiluminescence of the flame is stronger.
Manufacturing and Hydro Testing of a 10 MWe sCO2 Axial Turbine
Authors: Klaerner John D. , Moore J. Jeffrey , Robinson Kyle , Wade Jonathan L. , McClung Aaron 
Published: September 2023

Abstract
Supercritical CO2 [sCO2] power cycles designed for thermodynamic efficiencies above 50% push component designs into pressure and temperature combinations that approach the limits of American Society of Mechanical Engineers [ASME] Boiler and Pressure Vessel Code and ASME Piping Design Codes with Turbine inlet conditions near 250 bar and 715°C. These design conditions which limit available materials to high nickel alloys are compounded by the high fluid densities of sCO2 at these conditions which result in very compact machinery at the 10 MWe class which are currently being developed for the DOE Supercritical Transformational Electric Power [STEP] program1.
Design of the STEP Turbine is complete with integrated lessons learned from a previous 1 MWth sub-scale demonstration of a high temperature 10 MWe Turbine designed under the DOE SunShot Program2. Fabrication of the STEP Turbine is nearing completion with all housings and pressure containing components in hand. This paper provides a detailed look at design intentions and limitations for the pressurized sections of the main pressure casing and the fabrication of key turbine components. Additional discussion is provided regarding post-fabrication inspection and acceptance of the casing for use after issues with casing welds were identified late in the fabrication process.
The Effects of Channel Supplies on Overall Film-Cooling Effectiveness
Authors: Veley Emma M. , Thole Karen A. , Bogard David G. 
Published: September 2023

Abstract
Cooling components in the hot section of a gas turbine is essential to component durability. Common methods of cooling include rib turbulators in internal passages and film cooling on external surfaces. The holes that produce the film cooling are fed from the internal channels often containing ribs. Consequently, there is an interdependence of internal heat transfer and external film cooling. The purpose of this study was to obtain a better understanding of the interaction of ribs and film cooling. To quantify the cooling performance the surface temperatures were measured from which overall effectiveness was calculated. For the experiments, additively manufactured test coupons were made of Inconel 718 to match engine Biot numbers. These test coupons had internal feed channels with and without ribs and had both cylindrical holes and meter diffuser shaped holes with 15° lateral expansion angles and a 1° forward expansion angle. A single rectangular channel was one type of feed channel. The other type of feed channels was individual circular channels with each circular channel supplying an individual film-cooling hole.
The experimental results showed that the circular individual channels have 80% higher baseline overall effectiveness than the single rectangular channel without any film cooling. Ribbed turbulators without film cooling also increased the overall effectiveness by 21% for single rectangular channel and by 29% for the circular individual channels compared to the respective non-ribbed channels. While the film cooling increased the overall effectiveness of all geometries, the single rectangular channels had increased overall effectiveness levels by up to twice that of the no film-cooling case. On average the single rectangular channels had an 80% improvement from film cooling, whereas the individual channel feeds on average had only a 50% improvement given their high baseline effectiveness levels.
Impact of sCO2 Waste Heat Recovery System Air Cooler Integration on Aircraft Engine Thrust Performance
Authors: Bury Claire-Phonie , Vesely Ladislav , Stoia Michael , Fernandez Erik , Kapat Jayanta 
Published: September 2023

Abstract
The aviation industry has established a goal to reduce net carbon emissions by 50 % relative to 2005 levels by 2050. Carbon emissions can be reduced through direct or indirect methods. Direct approaches include alternative fuels, while indirect approaches can include waste heat recovery (WHR) from engine exhaust using a supercritical CO2 (sCO2) Brayton power cycle. Power cycle component design, particularly the heat sink heat exchanger (i.e., Cooler), are strongly influenced by changes in engine operating conditions. The present work focuses on integration of a sCO2 power system into an aircraft propulsion system and evaluation of its performance. The first part addresses the operation of the WHR unit under different operating conditions for an aircraft engine with a nominal thrust of 30 kN. The second part addresses the impacts of operating the sCO2 cycle near the critical point, Cooler heat addition and pressure drop in the engine bypass flow path, and Cooler design under different engine operating conditions. Analysis results show that the sCO2 WHR system can generate approximately 492 kW of electrical power with a cycle efficiency between 24 % and 28 % across different aircraft operating regimes.
Bayesian Information Fusion for Gas Turbines Diagnostics and Prognostics
Authors: Zaccaria Valentina , Fentaye Amare D. , Kyprianidis Konstantinos 
Published: September 2023

Abstract
Prognosis, or the forecasting of remaining operational life of a component, is a fundamental step for predictive maintenance of turbomachines. While diagnostics gives important information on the current conditions of the engine, it is through prognostics that a suitable maintenance interval can be determined, which is critical to minimize costs. However, mature prognostic models are still lacking in industry, which still heavily relies on human experience or generic statistical quantifications. Predicting future conditions is very challenging due to many factors that introduce significant uncertainty, including unknown future machine operations, interaction between multiple faults, and inherent errors in diagnostic and prognostic models. Given the importance to quantify this uncertainty and its impact on operational decisions, this work presents an information fusion approach for gas turbine prognostics. Condition monitoring performed by a Bayesian network is fused with a particle filter for prognosis of gas turbine degradation, and the effect of diagnostic models uncertainty on the prognosis are estimated through probabilistic analysis. Gradual and rapid degradation are simulated on a gas turbine performance model and the impact of sensor noise and initial conditions for the particle filter estimation are assessed. This work demonstrates that the combination of Bayesian networks and particle filters can give good results for short-term prognosis.
Simultaneous Damping and Mistuning Identification Using Nonlinear Optimization of Blade Tip Timing Data
Authors: Kurstak Eric , D’Souza Kiran 
Published: September 2023

Abstract
Empirically characterizing the dynamical properties of systems plays a crucial role in helping develop more accurate computational models of turbomachinery. Since computational models are only approximations of the physical system, there is an active need to constantly tune models to better mimic the real system. Extracting valuable information from test data can be challenging, especially for under-sampled data sets generated from blade tip timing systems. The use of tip timing systems is becoming more common due to the ease of use and the fact that systems maintain the original dynamics. Two commonly computed quantities from tip timing data are the system damping values and blade mistuning information. In this work, a method is proposed that simultaneously calculates the blade damping and mistuning values of a bladed disk using blade tip timing data from a synchronous vibration resonance crossing. The proposed method modifies an existing mistuning identification approach from the literature by increasing the applicability of the method for directly calculating mis-tuning values. A key benefit of the proposed approach is that blade-to-blade coupling effects are included in the parameter estimations. The blade responses between the experimental runs and computational simulations were compared to show agreement and that the computational model can accurately predict the motion of the blades when subjected to specific forcing conditions.
A Novel Axial Energy-Imparting Turbomachine for High-Enthalpy Gas Heating: Robustness of the Aerodynamic Design
Authors: Karefyllidis Nikolas , Rubini Dylan , Rosic Budimir , Xu Liping , Purola Veli-Matti 
Published: September 2023

Abstract
Hard-to-abate industrial processes, such as petrochemicals and cement production, have long been considered technically challenging to decarbonize. In response to the urgent demand to eliminate industrial CO2 emissions, a new class of energy-imparting turbomachines has been developed. These devices aim to convert mechanical into internal energy instead of pressurizing the gas, which enables high-temperature gas heating (up to 1700 °C) for a variety of applications. This paper is organized into three parts. First, the paper aims to demonstrate the capabilities of the novel, high-capacity, customizable, repeating-stage axial turbo-heater architecture for a hydrocarbon cracking example application. The study presents the new design requirements and working principles of this energy-imparting concept. The radically different objectives compared to a compressor enable ultra-high loading stage designs by avoiding the stability and efficiency constraints imposed on compressors. Within this new design space, the turbo-heater is able to achieve a loading coefficient ψ ≥ 4.0. Second, detailed numerical simulations of a multistage axial turbo-reactor with various vaneless space lengths are conducted. This work conclusively demonstrates the robustness and flexibility of the aerodynamic design despite employing a uniform blade design. It is emphasized that the concept is tolerant to unsteady interstage turbulent disturbances, enabling nominal work-input conditions to be achieved even for the most compact arrangements. Finally, having confirmed that the aerothermal restrictions on the vaneless space length can be removed, the designer is free to tailor the design to optimize the chemical reaction by (1) tailoring the residence time distribution to improve the yield and coking rate (2) homogenizing reaction progress by mixing-out concentration gradients and (3) adjusting the rotational speed to account for variations in the reaction dynamics for different feedstocks.
An Experimental Investigation of Heat Transfer for Supercritical Carbon Dioxide Cooling in a Staggered Pin Fin Array
Authors: Wardell Ryan J. , Richardson John , Otto Marcel , Smith Matthew , Fernandez Erik , Kapat Jayanta 
Published: September 2023

Abstract
Pin fin geometry in the trailing edge as turbulators in turbine blades has been a subject thoroughly researched for the past several decades. To improve the efficiency of turbomachinery, higher turbine inlet temperatures are necessary, introducing the need for internal cooling channel features, such as pin fin arrays. These solutions are necessary to avoid material failure at higher operating conditions by enhancing the heat transfer of the blade. Over the past decade, a shift toward applying supercritical carbon dioxide or sCO2 cycles has shown increased potential compared to the industry standard air cycles. Promising higher cycle efficiency, smaller footprints, and zero greenhouse gas emissions, sCO2 has become an attractive alternative to well-established air cycles. This alternative cycle introduces the need to re-visit the heat transfer capabilities of internal cooling geometries within this novel operating fluid environment. The first objective of this paper is to experimentally demonstrate the heat transfer characteristics of sCO2 as the secondary internal cooling fluid environment through testing a pin fin array in a closed loop at 200 bar and 400 Celsius inlet conditions, which stands well within the supercritical region of sCO2. Secondly, the experimental process aims to validate numerical simulation methodology for studying sCO2 environments for internal cooling of turbine blades in a matching pin fin geometry.
Damping and Fatigue Performance of Additive Manufactured Particle Damper Infused Instrumentation Rake
Authors: Celli Dino A. , Janczewski Timothy , Sheridan Luke , Scott-Emuakpor Onome , Warner Justin , Smith Lucas , Hollkamp John , Napper Lorean , George Tommy 
Published: September 2023

Abstract
Recently, laser powder bed fusion (LPBF) has been implemented as an enabling technology to create intentional large cavities during the print process to leave behind sections with embedded metal powder to act as particle dampers within the component. This novel application of particle damping has been applied to beam specimens with the additive manufactured (AM) particle damper technology and shown to attenuate resonant excitation and therefore stress in the component by up to 90% when compared to fully fused parts subjected to the same base excitation. More recently however, the AM damping technology has been applied to turbine engine relevant blade and hardware geometries. In this work, the damping and fatigue performance of a representative aerodynamic instrumentation rake are investigated. Four successful builds of the rakes were performed with and without internal pockets as well as with 0- and 45-degree printing orientations. Four internal configurations of the rakes are printed to include a 0.254mm, 0.381mm, 0.508mm, “fully fused” or 0mm pocket thicknesses. Each specimen is first scanned and three dimensionally reconstructed and analyzed to compare the nominal CAD drawing to as-printed and received geometry using blue light and CT scanning. Vibrational tests for the rake specimens are performed on a 20,000lb Unholtz-Dickie shaker and a OFV-505 single-point laser vibrometer and strain gages are utilized to measure the velocity and strain response respectively of the rake specimens. Sine wave down-chirp sweeps are conducted to excite the specimen in a 2nd bend mode to collect amplification and Q factor, or quality factors, to evaluate the damping performance amongst the rakes. Finally, vibration fatigue tests are performed, in the 2nd bend mode, to validate the improved fatigue performance of inherently damped rake components compared to the fully fused control group and demonstrate the novel additive damping technology to a commonly used experimental instrumentation fixture.
The Influence of Surface Roughness on Flow Transition by Well-Resolved Large Eddy Simulations
Authors: Jain Ishita , Wajih Issam , Sarkar Subrata 
Published: September 2023

Abstract
The transition of a spatially developing boundary layer is studied through highly resolved Large Eddy Simulations (LES) when subjected to external disturbances in the presence of surface roughness. Three rough wall conditions are considered in the present analysis, where roughness elements are homogeneous in the spanwise direction with cross-sectional shapes taken as triangle, square and semi-circle. The aspect ratio (s/k) considered here is 3, where k is the roughness height, and s is the spacing between the consecutive rows of roughness elements in the streamwise direction. The inlet flow Reynolds number based on the momentum thickness and freestream velocity (Reθ) is 360, while the freestream turbulence (fst) is 2.5%. The transition mechanisms are observed to change significantly with roughness shapes. Attributing to the sharp tip of the triangular shape, the shear layer trips to transition from laminar to turbulent flow via Kelvin-Helmholtz (K-H) instability. Whereas Λ-vortices and longitudinal streaks are the geneses for the boundary layer transition in square and semi-circular elements, respectively. Further, the influence of roughness on transition onset is explored by analyzing the turbulence statistics such as rms quantities, shear stress and spectral response.
Assessment of Airborne Contaminant Encountered During a Flight Mission
Authors: Suman Alessio , Zanini Nicola , Pinelli Michele 
Published: September 2023

Abstract
Flight missions are usually scheduled and managed on safety, cost, and commercial requirements. Depending on the aircraft or helicopter duties, the mission path, in terms of spatial coordinates and altitude, is guided by conditions that consider the scheduled mission’s scope and aim. For example, commercial aircraft transport passengers from two specific airports in a predetermined timetable. Conversely, helicopters for rescue or firefighting operations are employed in harsh conditions without a predetermined timeframe and schedule. In both cases, aircraft interact with the environment, usually contaminated by airborne particles, commonly known as soil and soot. These contaminants are due to the flight route, cruise altitude, take-off, and landing; therefore, they are specific for each aircraft mission. In the present work, the assessment of the airborne contaminant encountered by an aircraft has been proposed. A representative scheduled flight and a life-saving helicopter mission have been taken to propose a methodology for estimating the contamination that occurred to the engine based on the encountered contaminants. The contamination data was inferred by the Cloud-aerosol lidar and infrared pathfinder satellite observations while the flight data from the onboard aircraft transponder. Based on an open database, the methodology shows how contamination occurs over subsequent missions depending on the mutual interaction between route and environment conditions. The assessment of the engine contamination has been proposed in terms of equivalent dose, which is recognized as a helpful parameter to estimate the margin between safe-flight and dangerous-flight regimes.
On the Modelling of the Overspeed Performance of a Single Stage Turbine
Authors: Eryilmaz Ibrahim 
Published: September 2023

Abstract
This manuscript is on the aerodynamic characterization of a turbine particularly when the turbine loses its load permanently such as after a shaft or transmission failure. These conditions cause excessive acceleration of the turbine stage or stages. If not mitigated, a disk burst may lead to hazardous conditions threatening the passenger and the flight safety. Modelling brings the possibility of controlling the event and provides design flexibility for a lightweight and fail-safe system design.
Additional to the control system action through fuel shut-off, there are variety of conditions which affect the acceleration. Friction and blade damage in unlocated failures are examples of these. The aerodynamic performance is another important aspect as the turbine operates at far off-design conditions.
NASA E3 single stage high pressure turbine has fewer airfoils than the base two stage version and operate at a higher loading. Single stage turbine RANS CFD model has been prepared and the turbine is characterized at overspeed conditions up to 200% speed. Later, the tip clearance of the stage was increased up to 15% of the blade height to assess the performance deterioration. Finally, two more damage scenarios were introduced through truncating the blade tips from leading edge only and trailing edge only. Study shows that significant efficiency decrease occurs, which can be considered as a parameter in safety calculations and flight certification.
Windage Torque Reduction in Low-Pressure Turbine Cavities - Part 1: Concept Design and Numerical Investigations
Authors: Li Zhihui , Christodoulou Loizos , Jefferson-Loveday Richard , Ambrose Stephen , Jackson Richard , Lock Gary D. , Sangan Carl M. , Scobie James A. 
Published: September 2023

Abstract
The windage torque on rotational walls has negative effect on the performance of the low pressure turbine. In this paper, three novel flow control concepts (FCCs) were proposed to reduce the windage torque within a turbine stator well, with upstream and downstream cavities connected by an interstage labyrinth seal. The swirl and flow pattern inside a reference turbine cavity was first investigated and the potential locations for the FCCs were identified using numerical simulations. FCC1 was a circumferential row of leaned deflectors downstream of the labyrinth seal. FCC2 was a set of deflector vanes and platform to optimize the ingress swirl at high radius in the upstream cavity. FCC3 combined the two flow concepts and the superposition resulted in a stator well windage torque reduction of 70% when compared to the baseline design. The FCCs also showed performance benefits at off-design conditions and over a range of secondary flow rates to the cavity. In Part 2 [1], the numerical analysis and performance of the FCCs are validated in an experimental rig, using additively-manufactured components.