bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Re-Design Study Based on a High Pressure Cyclonic Combustor Operated With Liquid Fuel
Authors: Grimm Felix , Enderle Benedict , Kislat Oliver , Izadi Saeed , Zanger Jan , Kutne Peter , Aigner Manfred 
Published: November 2019

Abstract
Computational Fluid Dynamics are widely used as a design tool for a variety of thermo-fluid systems. Advantages of those numerical approaches are clearly the fairly detailed degree of valuable data at low computational costs, when RANS (Reynolds Averaged Navier Stokes) methods are used in the system design process.
In this work, a combustion system operated at elevated pressure conditions is re-designed with CFD RANS methods. The combustor is operated with liquid fuel and is positioned between an upstream recuperation and a downstream turbine section. System design is carried out on the basis of a commercially available C30 configuration from the Capstone® Turbine Corporation. The micro turbine produces 30kW of electrical power and is therefore highly suited for micro gas turbine related applications.
In the design process, as presented in the paper, several modifications are carried out. The system recuperation is changed, thus inflow modifications are given. Recuperation was explicitly simulated and is used as a combustor inflow boundary condition. The system is then analyzed and modified in terms of air splits in order to achieve certain combustion characteristics. Optimization is carried out for combustor air splits and turbine inlet temperature profile conditions are significantly improved. Reacting multi-phase simulations are used in order to characterize flow field and combustion. Further on, conjugated heat transfer is taken into account in order to characterize temperature distribution in the combustor. Additionally, combustor residence times are determined. It is demonstrated that the pursued methods and procedures are computationally cheap but at the same time highly suited and sufficient for thorough combustion system development.
Experimental and Numerical Investigation on the Influence of Thermally Induced Stress Gradients on Fatigue Life of the Nickel-Base Alloy Mar-M247
Authors: Thiele Marcus , Eckmann Stefan , Huang Min , Gampe Uwe , Fischer Kathrin A. , Schlesinger Michael 
Published: November 2019

Abstract
Today’s and future parameters of stationary gas turbines and aircraft engines require intensive and highly efficient cooling of hot gas path components. High temperature and thermally induced stress gradients with impact on fatigue life are the consequence. Thermally induced stress gradients differ from geometrically induced stress gradients with respect to stress mechanics by the independence from external loads and material mechanics by the influence of temperature on material properties and strength. Regarding the contribution and evaluation on damage, the latter characteristic feature in turbomachinery is currently not fully understood.
Therefore, a test facility has been designed, set up, and reported in GT2018-76519 for the investigation of the influence of stationary temperature, and thus thermally induced stress gradients, on the damage evolution of cooled high-temperature components. To achieve high temperature and thermally induced stress gradients, large heat fluxes are required. A unique radiation heating has been developed allowing very high heat fluxes of q̇ ≥ 1.5 MW/m2 for testing of hollow cylindrical specimens.
The conventional cast nickel-base alloy Mar-M247 has been chosen to study the influence of thermally induced stress gradients on fatigue life. The low-cycle fatigue testing of the hollow cylindrical specimens has been conducted both with and without superimposed stationary temperature gradients. In addition, Complex Low-Cycle Fatigue (CLCF) tests with symmetric and nonsymmetric loading conditions have been performed to provide the necessary database for the adaptation of a viscoplastic deformation model. To calculate the local stress-strain field and service life of the test specimens, linear elastic and viscoplastic finite element studies have been performed and were assessed by means of a fracture mechanics-based lifetime model.
The test results show the considerable influence of the temperature gradient on the low-cycle fatigue life for the investigated material. Both the radial temperature variation over the specimen wall with a hot outer surface and a cooled inner surface as well as the thermally induced stresses are stated to be the main drivers for the change in low-cycle fatigue life. The test results enhance the understanding of fatigue-damage mechanisms under local unsteady conditions and can be used as a basis for improved service life predictions.
Combined Experimental and Numerical Investigation of the Aero-Thermal Performance of a Rotor Blade Cascade With Platform Cooling
Authors: Barigozzi G. , Perdichizzi A. , Pestelli L. , Abram R. 
Published: November 2019

Abstract
This paper reports the results of a combined experimental and numerical investigation carried out to support the design of a film cooling system for a rotor blade platform. A 7 blade cascade of a high-pressure-rotor stage of a heavy-duty gas turbine has been tested in a low speed wind tunnel. Tests have been carried out at a low Mach number (Ma2is = 0.27) with a relatively high inlet turbulence intensity level of about 7.6% at the leading edge plane. The same cascade model was also numerically tested by means of a 3D RANS approach. Cascade flow and heat transfer behavior was first experimentally assessed without coolant injection and used to validate the numerical approach. These data were also used to design the platform cooling scheme based on shaped holes that was then tested for variable injection rates. The thermal behavior was measured by using the Binary PSP technique, so to obtain film cooling effectiveness distributions over the passage. RANS 3D CFD simulations were also run on the same cooled model and testing conditions, allowing to critically assess the prediction capability of the selected numerical approach and of the design process.
An Enhanced Gas Turbine Engine Laboratory: A Learning Platform Supporting an Undergraduate Engineering Curriculum
Authors: Bellocchio Andrew T. , Benson Michael J. , Van Poppel Bret P. , Norberg Seth A. , Benz Ryan 
Published: November 2019

Abstract
A gas turbine engine has supported the U.S. Military Academy’s mechanical engineering program for nearly three decades. Recent, substantial enhancements to the engine, controls, and data acquisition systems greatly increased the student experience by leveraging its broad capabilities beyond the original laboratory learning objectives. In this way, the laboratory served as a learning platform for more than just instruction on gas turbine fundamentals and the Brayton cycle.
The engine is a refurbished auxiliary power unit from Pratt & Whitney Aeropower, installed in the Embrauer 120 and similar to a unit installed on a U.S. Army helicopter. Whereas the original laboratory experience permitted students to test the engine at three different loads applied by a water brake dynamometer, the revised experience allowed for a broader range of test conditions. The original laboratory included single point measurements of three temperatures and two pressures, along with the fuel flow rate, dynamometer torque, and engine speed. The revised laboratory allowed the user to vary bleed air and engine loads across an operational envelope at a user-specified acquisition rate. The improved data acquisition system used LabVIEW™ and included multiple state sensors for pressure, temperature, fuel flow, bleed air, and dynamometer performance, thereby enabling a more complete analysis by accounting for the energy transported by bleed airflow and absorbed by the water brake. Students then quantified the uncertainty in their measurements and analysis. The new emphasis on uncertainty quantification, part of a program-level initiative, challenged students’ notion of “substitute and solve” while also familiarizing them with large, experimental data sets.
The re-envisioned laboratory raised the students’ level in the cognitive domain and served as their premier engine experience. Rather than merely observing engine adjustments across a small range of conditions, students designed their own laboratory experience. With the updated approach, students viewed a graphic of the turbine’s laboratory operating range and chose the key variables of interest — selecting data points within the laboratory operating range — and then justified their selections. The enhanced experience added analysis of flow exergy and exergetic efficiency. The exercise also challenged students to hypothesize why actual turbine performance was less than predicted and determine sources of error and uncertainty. Moreover, the new laboratory offers opportunities to expand the turbine engine’s utility from supporting a single thermal-fluids course to a multidisciplinary learning platform. Concluding remarks address concepts for augmenting course instruction in other courses within the curriculum, including heat transfer, mechanical vibrations, and dynamic modeling and controls.
Experimental Study of the Precessing Vortex Core Impact on the Liquid Fuel Spray in a Gas Turbine Model Combustor
Authors: Renaud Antoine , Ducruix Sébastien , Zimmer Laurent 
Published: November 2019

Abstract
Despite being good candidates for the reduction of pollutant emissions from gas turbines, burners operating in Lean Premixed Prevaporized regimes often face stability issues and can be sensitive to perturbations. The swirling flow used to aero-dynamically stabilize the flame can also lead to the appearance of a large-scale coherent flow structure known as the Precessing Vortex Core (PVC). In the present study, a swirl-stabilized combustor fed with liquid dodecane is studied at a globally lean operating condition with the help of high-speed diagnostics and Dynamic Mode Decomposition (DMD) as the main post-processing method. It is shown that the trace of a PVC originating inside the injector is still present in the fuel spray at the entrance of the chamber even though the aerodynamical structure itself is not detectable anymore. The perturbation of the fuel spray is then transmitted to the flame through local equivalence ratio fluctuations. It is observed that the PVC trace on the spray and thus on the flame can be suppressed by air flow modulations generated by a siren device. The suppression of this trace is shown to come from a decay of the aerodynamical structure itself rather than by a change in fuel mixing or vaporization. Analysis of the characteristic frequency of the PVC shows a frequency spread indicating a loss of coherence of the structure with the high amplitude air flow rate fluctuations.
Semiconductor Nano and Micro Membrane Based Pressure Sensors for Wide Bandwidth Measurements
Authors: Kang Y. , Sibold R. , Homer M. , Gladwin L. , Claus R. , Ng W. , Ruan H. 
Published: November 2019

Abstract
Semiconductor nano&micro membranes (NMMs) are gaining acceptance in the semiconductor industry as the benefits they provide become key enablers in scaling and performance enhancements of electronic devices. These tailored-modulus conformal NMM sensor skins with integrated interconnect elements and electronic devices can be applied to new or existing wind tunnel models for full spectrum pressure monitoring. The material is resistant to normal fluids and solvents, can potentially operate over a wide temperature range, and is capable of withstanding erosion. Experimental data presented in this paper demonstrates that: 1) silicon NMMs may be used as single pressure sensor transducers and elements in sensor arrays, and 2) the arrays may be instrumented to map pressure over the surfaces of test articles over a range of Reynolds numbers, temperature and other environmental conditions. Of most importance, we have 1) shown that the small-feature-size sensor elements are highly sensitive to pressure (frequency response from DC up to 5MHz), 2) developed several types of sensor packages for the demonstration of pressure sensing with a miniature probe tip, and 3) confirmed operation in wind tunnel and shock tube tests over 100 times up to Mach 4.2 on several test articles.
Visualization of Supercritical Carbon Dioxide Flow Through a Converging-Diverging Nozzle
Authors: Lim Chang Hyeon , Pathikonda Gokul , Pidaparti Sandeep , Ranjan Devesh 
Published: November 2019

Abstract
Supercritical carbon dioxide (sCO2) power cycles have the potential to offer a higher plant efficiency than the traditional Rankine superheated/supercritical steam cycle or Helium Brayton cycles. The most attractive characteristic of sCO2 is that the fluid density is high near the critical point, allowing compressors to consume less power than conventional gas Brayton cycles and maintain a smaller turbomachinery size. Despite these advantages, there still exist unsolved challenges in design and operation of sCO2 compressors near the critical point. Drastic changes in fluid properties near the critical point and the high compressibility of the fluid pose several challenges. Operating a sCO2 compressor near the critical point has potential to produce two phase flow, which can be detrimental to turbomachinery performance. To mimic the expanding regions of compressor blades, flow through a converging-diverging nozzle is investigated. Pressure profiles along the nozzle are recorded and presented for operating conditions near the critical point. Using high speed shadowgraph images, onset and growth of condensation is captured along the nozzle. Pressure profiles were calculated using a one-dimensional homogeneous equilibrium model and compared with experimental data.
Sweeping Jet Film Cooling at High Blowing Ratio on a Turbine Vane
Authors: Hossain Mohammad A. , Ameri Ali , Gregory James W. , Bons Jeffrey P. 
Published: November 2019

Abstract
Experimental and numerical investigations were conducted to study the effects of high blowing ratios and high freestream turbulence on sweeping jet film cooling. Experiments were conducted on a nozzle guide vane suction surface in a low-speed linear cascade. Experiments were performed at blowing ratios of 0.5–3.5 and freestream turbulence of 0.6% and 14.3%. Infrared thermography was used to estimate the adiabatic cooling effectiveness. Thermal field and boundary layer measurement were conducted at a cross-plane (x/D = 12) downstream of the hole exit. Results were compared with a baseline 777-shaped hole and showed that sweeping jet hole has a better cooling performance at high blowing ratios. The Thermal field data revealed that the coolant separates from the surface at high blowing ratios for the 777-shaped hole while the coolant remains attached for the sweeping jet hole. Boundary layer measurement further confirmed that due to the sweeping action of the jet, the jet momentum of the sweeping jet hole is much lower than that of a 777-shaped hole. Thus the coolant remains closer to the wall even at high blowing ratios. Large Eddy Simulations (LES) were performed for both sweeping jet and the 777-shaped hole to evaluate the interaction between the coolant and the freestream at the near hole regions. Results showed that 777-shaped hole has a strong jetting action at high blowing ratio that originates inside the hole breakout edges thus causing the jet to blow off from the surface. In contrast, the sweeping jet hole does not show this behavior due to its internal geometry and the sweeping action of the jet.
A Modular Transonic Turbine Cascade for Cooled Rotor Metal Effectiveness Investigations
Authors: Parker James A. , Romero Ed , Povey Thomas 
Published: November 2019

Abstract
The Metal Effectiveness Rotor Cooling (MERC) facility at the University of Oxford is a new blow-down linear cascade tunnel developed for aerothermal research of turbine rotor blade and rotor platform cooling systems. A high level of engine similarity is achieved with matched Mach numbers, Reynolds numbers, coolant-to-mainstream pressure ratios, and Biot number (using DMLS components of appropriate conductivity). The modular working section includes five blade passages, including platform and fir tree root geometries, and engine representative hub seals. The facility is designed to allow high accuracy IR camera measurement of the blade and platform surfaces (for metal effectiveness measurements) and downstream area traverse measurements. Detailed traverse measurements are possible in a single run, because of the long run time of the facility (up to 5 minutes).
The facility is being used for development and optimisation research of novel blade and platform cooling systems, with an emphasis on overall thermal performance of parts (metal effectiveness). Modular cassettes allow the blade components to be rapidly interchanged, and for variations to the designs of the front and rear hub seals. The engine representative seals and coolant feed paths allow for all engine leakage flows to be replicated in the experiment. This is important, because they are influential in determining the platform cooling flow structure (character and extent of secondary flow) and overall metal effectiveness result. Coolant supplied to each of the hub seals, and blade shank pocket can be independently varied to achieve required mass flows and pressure ratios. Rotor blades are typically manufactured using DMLS, allowing fast development and optimisation of fully-featured cooling systems at significantly reduced cost compared to traditional casting techniques.
To demonstrate the capability of the new facility, we present full-surface metal-effectiveness measurements of the rotor blade platforms (post-processed using high-accuracy infrared thermography techniques separately developed at the University of Oxford.)
The purpose of this paper is to outline the capabilities of the facility, describe the prior work and research context which led to its development, and to demonstrate the accuracy of the measurement techniques employed by presenting typical measured data. An argument is made for the importance of including realistic hub seal leakage paths in experiments investigating platform cooling flows by illustrating their significant impact on overall cooling performance. The MERC facility is a response to the need to develop more advanced rotor platform cooling schemes for future engines.
Numerical Investigation of Circumferential Groove Casing Treatment on a Low Speed Contra-Rotating Fan
Authors: Heinrich Martin , Khaleghi Hossein , Friebe Christian 
Published: November 2019

Abstract
This study is aimed at understanding the effects of circumferential groove casing treatment on the performance of a low speed contra-rotating fan. Three dimensional, transient simulations are carried out using the open source CFD library Open-FOAM. The numerical results are validated with experiments for the smooth casing, which show a good agreement. Three treated casing configurations are investigated: 1) grooves at the top of the first rotor, 2) grooves at the top of the second rotor, and 3) grooves at the top of both rotors. Two operating points are simulated for all configurations. Flow inside the grooves is highly dominated by the main and blade passage flows. Grooves increase fan performance at near-stall flow conditions by up to 3 % and reduce pressure fluctuations significantly. Furthermore, they have a larger impact on fan performance when placed on top of the first rotor compared to placing them on top of the second rotor.
Aerodynamic and Structural Design of a Centrifugal Fan for an Air Cushion Vehicle
Authors: Cameron B. H. , Grald E. W. , Conboy T. M. , Passow C. H. , Kattamis N. T. , George Daniel , Bray Joseph , Cole Robert E. 
Published: November 2019

Abstract
A methodology is presented for the re-design of a large centrifugal impeller used for the lift fan on an air cushion vehicle. The design is driven by stringent requirements for aerodynamic and structural performance. It is also desired to minimize the fan’s life cycle cost, by reducing both the manufacturing cost and on-going maintenance burden. Improving the fan efficiency will increase the vehicle’s endurance and range, and minimizing life cycle cost will reduce the overall operational expenses. The lift fan assembly has a double-inlet impeller and an offset double-discharge volute. The new impeller design provides increased air flow with similar aerodynamic efficiency when compared to the prior design. To reduce the manufacturing cost, the new fan blade design can be produced by an aluminum extrusion process. The manufacturing process dictates that the blade cross-section be two-dimensional across the entire span, which poses structural challenges for attachment of the blades to the shroud and center disk. Analysis of the aerodynamic and structural performance of the lift fan was carried out using computational fluid dynamics (CFD) and structural finite element analysis (FEA) models. The fabrication of full-scale lift fan components is described. Plans for final assembly and for conducting full-scale, full-power aerodynamic testing will also be explained.
Design Considerations for Ceramic Matrix Composite High Pressure Turbine Blades
Authors: Boyle Robert J. , Parikh Ankur H. , Nagpal Vinod K. 
Published: November 2019

Abstract
Issues associated with using SiC/SiC Ceramic Matrix Composite (CMC) materials for High Pressure Turbine (HPT) rotor blades are explored. SiC/SiC materials have higher temperature capability than current HPT superalloys. The strength versus temperature characteristics of SiC/SiC CMCs differs from that of superalloys. Stress analyses were done for a NASA specified notional single aisle aircraft engine blade to be available in the N+3 time frame, (beyond 2030). Stacking, the relative position of hub and tip sections, depends on both pressure and centrifugal forces, and material density. The effect of blade stacking on blade stresses is examined. The change in stresses as the rotation rate varies is examined. The change in engine weight, and thus fuel consumption, due to changes in engine size as the rpm changes is discussed. SiC/SiC CMC materials are generally not isotropic. The effect on stresses and strains of a directional variation in Young’s modulus is examined. Shrouding metallic HPT rotor blades is not common. Shrouding SiC/SiC CMC rotor blades may be feasible due to the lower density, and thus lower centrifugal loads, of SiC/SiC blades. The increase in stresses due to shrouding a SiC/SiC blade is discussed.
Analyzing the Potential for Erosion in a Supercritical CO2 Turbine Nozzle With Large Eddy Simulation
Authors: Finn Justin R. , Doğan Ömer N. 
Published: November 2019

Abstract
Large eddy simulation of supercritical CO2 flow carrying solid oxide particles through a radial turbine nozzle has been conducted at a Reynolds number of 0.5 × 106. The three-dimensional geometry corresponds to the nozzle where erosion damage was observed by Fleming and Kruizenga [1]. The turbulent flow through the passage was approximated as incompressible, and the spatially filtered Navier-Stokes equations were solved on an unstructured grid. One way coupled, porous, oxide particles (30μm diameter, 2500 kg ṁ m−3) were continuously injected upstream of the passage and tracked in a Lagrangian manner as they were carried through the domain by the turbulent flow. Statistics of mean particle concentration and particle-nozzle impacts were collected to identify regions along the passage prone to erosion damage. For this condition, the particles became highly concentrated as they passed along the pressure side of the nozzle. High impact velocities and oblique collision angles near the trailing edge led to relatively high predicted rates of erosion, near the location where damage was observed in the laboratory. Extrapolation of simulation results to proposed operational Reynolds numbers suggests that very small particles, with diameter < 10μm, could cause high velocity impacts and eventual degradation.