bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Investigation of Periodically Unsteady Wake Impact on the Secondary Flow in a 1.5 Stage Full Annular LPT Cascade With Modified T106 Blading
Authors: Sinkwitz Martin , Engelmann David , Mailach Ronald 
Published: August 2017

This paper transfers findings from linear cascade studies to the annular system. Experimental studies have been conducted on the newly designed 1.5 stage full annular rotating axial turbine rig at Chair of Thermal Turbomachinery, Ruhr-Universität Bochum. Therefore, an existing large scale low speed test rig was retrofitted with newly designed T106RUB low pressure turbine (LPT) blading, state-of-the-art measurement technologies and multi-dimensional traversing devices to allow for highly resolved measurements of unsteady wake stator flow interaction in both space and time. Incoming wakes are generated by a variable-speed driven rotor disk equipped with cylindrical bars.
The measuring concept for an in-depth analysis of unsteady flow phenomena is presented and results from highly resolved time-averaged and time-resolved flow field traverses are discussed and compared. In detail the time-dependent interaction of periodically passing bar wakes with the boundary layers and secondary flow structures of the T106RUB stator row is investigated. Special emphasis is put on time-varying dilatation and location of individual components of the vortex system and on potential flow separation along the blade suction surface. It is evaluated how these factors can contribute to a time-dependent homogenization of stator exit flow and a consequent loss reduction in the present configuration.
Computational Study of a Customised Shallow-Sump Aero-Engine Bearing Chamber With Inserts to Improve Oil Residence Volume
Authors: Adeniyi Akinola A. , Chandra Budi , Simmons Kathy 
Published: August 2017

An aero-engine bearing chamber is a structure that is used to contain and collect oil used in lubricating and cooling the bearings supporting the high-speed engine shafts. There are various bearings in an aero-engine. Within the bearing chambers, there are typically the bearings, rotating shafts, seals and gears (in some designs). The walls of the bearing chamber are stationary and there are vents and sumps to take out the oil, via an offtake pipe, and the sealing air. The oil collected via the sump and vents is recycled and used again in the loop. To prevent oil degradation and reduce chance of coking in the chamber, it is desired that all of the oil goes through the recycling loop, with no oil staying longer than necessary in the chamber. The sealing air is used to maintain a positive pressure to keep the oil within the chamber. The flow inside a bearing chamber is highly turbulent and consists of a rotating mixture of oil and air.
A smaller amount of the oil, mostly as oil-droplets, exits at the vents and is separated from the air using de-aerators [1]. It is expected that by gravity, most of the oil collects at the sump and can be easily scavenged. This is provided the sump can be large enough. The geometry of a bearing chamber is, however, complex largely because of space limitations. It is very important that oil is not resident longer than necessary to prevent over-heating and therefore deterioration or coking. Experimental observations by Chandra & Simmons [2], have shown that bearing chambers with deep sumps perform better that those with shallow sumps.
Since shallow sumps are inevitable, a number of innovative studies have been done to improve bearing chamber designs. The presence of air in the oil (e.g. as bubbles) reduces the efficiency of the scavenging pump. Other factors such as oil momentum and windage can take oil away from the off-take pipe potentially increasing oil residence volume. Chandra & Simmons [2] placed inserts such as grille cover, perforated plate, etc, on a side of the bearing wall and improvements in the residence volume were seen. In this work, we are looking at a detailed computational fluid dynamics (CFD) simulation of one of the inserts that performed well. This will aid understanding of the flow characteristics of using an insert to improve oil residence in a bearing chamber.
Performance of Adaptive Lubricants in a Hybrid Journal Bearing Operating Under Fully Saturated Conditions
Authors: Chien Ssu-Ying , Cramer Mark , Fu Gen , Untaroiu Alexandrina 
Published: August 2017

Adaptive lubricants involve binary mixture of synthetic oil and dissolved carbon dioxide (CO2). Unlike conventional lubricant oils, the lubricant viscosity not only varies with the temperature within the bearing, but also can be directly adjusted through the CO2 concentration in the system. In this study, we investigated the performance of adaptive lubricants in a hybrid journal bearing considering the synthetic oil to be fully saturated by CO2. The adaptive lubricant analyzed for this study was the polyalkylene glycol (PAG) oils with low concentration of CO2 (< 30%). A three-dimensional computational fluid dynamic (CFD) model of the bearing was developed and validated against the experimental data. The mixture composition and the resultant mixture viscosity were calculated as a function of pressure and temperature using empirical equations.
The simulation results revealed that the viscosity distribution within the PAG/CO2-lubricated bearing is determined primarily by the pressure at the low operating speed. When the speed becomes higher, it is the temperature effect that dominates the viscosity distribution within the bearing. Moreover, the PAG/CO2-lubricated bearing can reduce up to 12.8% power loss than the PAG-lubricated bearing due to the low viscosity of PAG/CO2 mixture. Most importantly, we have found the PAG/CO2 can enhance the load capacity up to 19.6% when the bearing is operating at the high speed conditions.
A Novel Test Rig for Assessing Advanced Rotor Blade Cooling Concepts, Measurement Technique and First Results
Authors: Elfner Maximilian , Schulz Achmed , Bauer Hans-Jörg , Lehmann Knut 
Published: August 2017

This paper presents a new approach for assessing rotor blade cooling concepts. A new test rig has been designed, built and commissioned, allowing fast comparison of different cooling schemes as well as absolute surface temperature measurements for different cooling concepts. By scaling the test specimen, full aerothermal similarity was achieved at high measurement accuracy and resolution. This similarity however poses high demand on the employed measurement techniques.
Surface temperature (and thus cooling effectiveness) is measured using high resolution, high dynamic range infrared thermography with an improved calibration method for in-situ radiation correction. Furthermore, an improved image evaluation algorithm is presented, allowing angle-of-view dependent emissivity correction and full 3D-evaluation of image data. Those improvements enable the measurement on strongly cooled and strongly curved surfaces, and thus the use of scaled rotor blades with true geometry. First results are presented comparing total cooling effectiveness of a conventionally cooled blade with internal ribs to the effectiveness of an internal swirl design blade. They show the feasibility of the measurements and the importance of the presented correction method.
High Momentum Jet Flames at Elevated Pressure: B — Detailed Investigation of Flame Stabilization With Simultaneous PIV and OH-LIF
Authors: Severin Michael , Lammel Oliver , Ax Holger , Lückerath Rainer , Meier Wolfgang , Aigner Manfred , Heinze Johannes 
Published: August 2017

A model FLOX® combustor, featuring a single high momentum premixed jet flame, has been investigated using laser diagnostics in an optically accessible combustion chamber at a pressure of 8 bar. The model combustor was designed as a large single eccentric nozzle main burner (Ø 40 mm) together with an adjoining pilot burner and was operated with natural gas.
To gain insight into the flame stabilization mechanisms with and without piloting, simultaneous Particle Image Velocimetry (PIV) and OH Laser Induced Fluorescence (LIF) measurements have been performed at numerous two-dimensional sections of the flame. Additional OH-LIF measurements without PIV-particles were analyzed quantitatively resulting in absolute OH concentrations and temperature fields.
The flow field looks rather similar for both the unpiloted and the piloted case, featuring a large recirculation zone next to the high momentum jet. However, flame shape and position change drastically. For the unpiloted case, the flame is lifted, widely distributed and isolated flame kernels are found at the flame root in the vicinity of small scale vortices. For the piloted flame, on the other hand, both pilot and main flame are attached to the burner base plate, and flame stabilization seems to take place on much smaller spatial scales with a connected flame front and no isolated flame kernels.
The single shot analysis gives rise to the assumption that for the unpiloted case small scale vortices act like the pilot burner flow in the opposed case and constantly impinge and ignite the high momentum jet at its root.
A Study of Source Term Model for Full Coverage Film Cooling Simulation
Authors: Zhang Yufang , Wang Ke 
Published: August 2017

Full-coverage film cooling, based on use of closely spaced inclined small diameter cylindrical holes, is considered as a very efficient cooling approach for modern combustion chambers. However, a CFD-based thermal analysis of such components is very expensive if mesh is generated in numerous cooling holes. In order to reduce the computational cost, several models have been developed by researchers. Among them, source term model is one of the most potential models. In this model, a film cooling hole is replaced by a mass source and a mass sink in the fluid domain, and an energy sink is used to simulate the convective cooling inside hole.
In this paper, the source term model was used for RANS simulation of a multi-perforated plate case, and the effect of grid setup was analyzed. It has been concluded that the height of first prism layer has an important effect on the numerical results, whereas effect of maximum grid size on coupled walls is relatively small. Then, the source term model was used for numerical simulations of a single dome combustor case. Numerical results of flow split and pressure losses in non-reacting case agreed well with experimental results. In reacting case, a good agreement between numerical and experimental results, including liner temperature and pressure loss, was also obtained.
Economic Viability of On-Line Compressor Washing for Different Rated Capacity
Authors: Musa Gali , Igie Uyioghosa , Pilidis Pericles , Gowon Sule 
Published: August 2017

On-line compressor washing has shown to relatively improve engine performance by decelerating the rate of engine degradation due to fouling during operation. There is a number of influencing parameters that determine the economic benefit, some of which includes the frequency of washing, the effectiveness of washing liquid and the size of the engine or power output produced.
This study, unlike others, explores the cost-benefit analysis, focusing on the viability of compressor washing for various gas turbine engines or rated capacities, ranging from a 5MW single machine to a 300MW unit. Fouling degradation trend obtained from actual machine operation have been implemented and the application of different washing frequencies and recoveries of lost power shows the significantly higher return on investment for the larger engines in comparison to the smaller engines. This is partly due to the fact that the washing equipment cost, though increases with engine size, does not increase proportionally. Another contributing factor is the cost penalty per MW when the same level of degradation is implemented for all the engines.
Some of the key aspects captured in this study are the capital and maintenance cost used, that relates to the different engine sizes, therefore ensuring a more indicative basis for comparing the viability of the different engines. This also includes the estimation of washing liquid utilised based on their respective typical mass flows.
When the number of engines increases to 4 for a given operations, the return on investment increases by a factor of 3.5. This is possible as one wash unit can be applied to more than one engine within proximity. Higher return on investment is achieved when more than one relatively small engine is used to obtain a higher total power output. This is about 1.7 times higher for four 63MW engines versus one 255MW, as relatively cheaper washing equipment is implemented for the same total operational capacity. The study also shows that on-line washing is not always viable for electric power generation. This is observed for smaller light-duty engines, especially in situations when the level of fouling is relatively low.
Direct Fired Oxy-Fuel Combustor for sCO2 Power Cycles: 1MW Scale Design and Preliminary Bench Top Testing
Authors: Delimont Jacob , McClung Aaron , Portnoff Marc 
Published: August 2017

Direct fired oxy-fuel combustion as a heat source for supercritical carbon dioxide (sCO2) power cycles is a promising method for providing the needed thermal energy input. The method of combustion has the potential to provide efficient power generation with integrated carbon capture at up to 99% of generated CO2. One of the highest efficiency power cycles being considered for sCO2 cycles in the recompression cycle. In the recompression sCO2 power cycle, the amount of energy recovered from the recuperation is roughly five times the energy added via the combustor. Because of this high degree of recuperation in sCO2 power cycles, the inlet temperature of the combustor is much higher than a more traditional combustor design. This elevated combustor temperature leads to some unique design challenges and approaches which are quite different from a traditional combustion system. A combustor designed for these conditions has never been built, and thus the design of the combustor discussed in this paper started from a clean slate.
This necessitates a large degree of fundamental research which might not be necessary for a more well understood traditional combustor design process. Building on previous thermodynamic and chemical kinetics studies, a reduced order reaction kinetics model was used with ANSYS CFX software to explore various auto-ignition type combustor geometries. A discussion of some geometries and the modelling techniques used is presented. Various injector configurations were examined and metrics were used to compare the various configurations. By utilizing the CFD flow field results, a preliminary design for a 1MW-class oxy-fuel combustor was developed.
In the past, little experimental research has been conducted on combustion within carbon dioxide at pressures above 200 bar. In order to confirm the validity of the auto-ignition style combustor a small bench top test rig was constructed to test the oxy-fuel combustion at the full pressure and temperature. This system was designed to validate some of the fundamental properties of the combustion. This includes a gas sampling system and a measurement of auto-ignition delay. Preliminary, data from a bench top scale, sCO2 oxy-fuel combustor experiment will be presented.
The results from this work will enable future development of sCO2 power cycles which enable 99% carbon capture, while maintaining overall cycle efficiency which is competitive with natural gas combined cycle power plants.
LPC Blade and Non-Axisymmetric Hub Profiling Optimization Using Multi-Fidelity Non-Intrusive POD Surrogates
Authors: Benamara Tariq , Breitkopf Piotr , Lepot Ingrid , Sainvitu Caroline 
Published: August 2017

The present contribution proposes a Reduced Order Model based multi-fidelity optimization methodology for the design of highly loaded blades in low pressure compressors. Environmental, as well as, economical limitations applied to engine manufacturers make the design of modern turbofans an extremely complex task. A smart compromise has to be found to guarantee both a high efficiency and a high average stage loading imposed for mass reduction constraints, while satisfying stability requirements.
The design of compressor blades, usually involves at the same time a dedicated parametrization set-up in highdimensional space and high-fidelity simulations capturing, at least, efficiency and stability as most impacting phenomena. Despite recent advances in the high-performance computing area, introducing high-fidelity simulations into automated optimization, or even surrogate assisted optimization, loops still stands as a endeavor for engineers. In this framework, the proposed methodology is based on multi-fidelity surrogate models capable of representing the physics at hand in reduced spaces inferred from both precise, albeit costly, high-fidelity simulations and abundant, yet less accurate lower-fidelity data. Finally, we investigate the coupling of the proposed hierarchised multi-fidelity non-intrusive Proper Orthogonal Decomposition based surrogates with an evolutionary algorithm to reduce the number of high-fidelity simulation calls towards the targeted optimum.
Real Time Conditioning Monitoring for Failure Prediction
Authors: Franco-Piña J. Alejandro , Contreras Luis , Jauregui Juan C. 
Published: August 2017

Nowadays, the growth in the diameter of the rotors and the power capacity of the machinery require the application of constant monitoring to predict failures and reduce maintenance activities. These activities prevent emergency stops and failures that require the replacement of components; however, these operations involve a high cost.
The system presented in this paper integrates a fast data processing method that can analyze monitoring signals in real-time. The overall system includes a set of sensors for the measurement of acceleration, angular velocity, temperature, voltage, electrical current, and oil quality. The system presented is able to produce a frequency spectrum with a length of 8192 points. The FFT module was implemented in a FPGA (Field Programmable Gate Array) and it generates in real time, the frequency spectrum. This system adjusts the dominant frequencies to the wind turbine velocity.
The Effect of External Casing Impingement Cooling Manifold Standoff Distance on Casing Contraction for Thermal Control of Blade Tip Clearance
Authors: Choi Myeonggeun , Gillespie David R. H. , Lewis Leo V. 
Published: August 2017

Thermal closure of the engine casing is widely used to minimize undesirable blade tip leakage flows thus improving jet engine performance. This may be achieved using an impingement cooling scheme on the external casing wall, provided by manifolds attached to the outside of the engine. The assembly tolerance of these components leads to variation in the standoff distance between the manifold and the casing and its effects on casing contraction must be understood to allow build tolerance to be specified.
For cooling arrangements with promising performance, the variation in closure with standoff distance of z/d = 1–6 were investigated. A cooling manifold, typical of that adopted by several engine companies, incorporating three different arrays of short cooling holes (chosen from previous study by Choi et al. (2016)) and thermal control dummy flanges were considered. A series of heat transfer tests using a transient liquid crystal technique were undertaken to measure spatially resolved heat transfer coefficient of a baseline sparse jet array. The experimental heat transfer results validated the extensive numerical predictions using RANS realizable k-epsilon turbulence model. The associated casing contraction was inferred from a finite element analysis using these distributions as the external casing thermal boundary condition. The flow in the system can be modulated to match the closure at different engine operating conditions, the relationship between thermal closure and coolant mass flow rates, inferred from the averaged jet Reynolds numbers assuming uniform distribution between cooling holes was predicted. Typical contractions of 0.5–2.2mm are achieved from the 0.02–0.35kg/s of the current casing cooling flows.
The variation in heat transfer coefficient observed with standoff distance is much lower for the sparse array investigated compared to a previous designs employing arrays typical of blade cooling configurations. The reason for this is explained through interrogation of the local flow field and resultant heat transfer coefficient. This implies acceptable control of the circumferential uniformity of case cooling can be achieved with relatively large assembly tolerance of the manifold relative to the casing.
The Increasing Complexity of Hot Corrosion
Authors: Shifler David A. 
Published: August 2017

It has been conjectured that if sulfur in fuel is removed, engine materials will cease to experience attack from hot corrosion, since this sulfur has been viewed as the primary cause of hot corrosion and sulfidation. Historically, hot corrosion has been defined as an accelerated degradation process that generally involves deposition of corrosive species (e.g., sulfates) from the surrounding environment (e.g., combustion gas) onto the surface of hot components, resulting in destruction of the protective oxide scale. Most papers in the literature, since the 1970s, consider sodium sulfate salt as the single specie contributing to hot corrosion.
Recent Navy standards for Navy F-76 and similar fuels have dropped the sulfur content down to 15 parts per million (ppm). Most observers believe that the removal of sulfur will end hot corrosion events in the Fleet. However, the deposit chemistry influencing hot corrosion is known to be much more complex consisting of multiple sulfates and silicates. Sulfur species may still enter the combustion chamber via ship’s air intake, which may include seawater entrained in the air. In addition to sodium sulfate, seawater contains magnesium, calcium and potassium salts, and atmospheric contaminants that may contribute to hot corrosion. This paper will cover some of the revised understanding of hot corrosion and consider other possible contaminants that could further complicate a full understanding of hot corrosion.
Collaborative environmental governance: Achieving collective action in social-ecological systems
Authors: Bodin Örjan 
Published: August 2017

Collaborative governance
By its nature, environmental governance requires collaboration. However, studies have shown that various types of stakeholders often lack the willingness to deliberate and contribute to jointly negotiated solutions to common environmental problems. Bodin reviews studies and cases that elucidate when, if, and how collaboration can be effective and what kind of environmental problems are most fruitfully addressed in this way. The piece provides general conclusions about the benefits and constraints of collaborative approaches to environmental management and governance and points out that there remain substantial knowledge gaps and key areas where more research is needed.

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