bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Strategy of Reactant Mixing in Methane Direct-Fired sCO2 Combustors
Authors: Manikantachari K. R. V. , Martin Scott , Vesely Ladislav , Bobren-Diaz Jose O. , Vasu Subith , Kapat Jayanta 
Published: August 2018

The sCO2 power cycle concept is identified as a potentially efficient, economical, and pollutant free power generation technique for future power generation. Recent work in the literature provides some strategies and best operating conditions for direct-fired sCO2 combustors based on zero-dimensional reactor modeling analysis, however there is a need for a detailed investigation using accurate combustion chemical kinetics and thermophysical models. Here, the sCO2 combustor is modelled by coupling perfectly stirred reactor (PSR) and plug flow reactor (PFR) models. The real gas effects are incorporated using the Soave-Redlich-Kwong (SRK) equation of state. Also, the detailed Aramco 2.0 kinetic mechanism is used for the combustion kinetic rates.
It is found that the primary zone must be diluted either with thirty or forty-five percent of the total CO2 in the cycle to have a feasible combustor design. However, the forty-five percent dilution level at 950 K and 1000 K yielded a better consumption of CO, O2 and CH4. Also, the cross-sectional area of the sCO2 combustor can be scaled-down to 10 to 20 times smaller than a traditional combustor with the same power output. Further, from this investigation, it is also recommended to have a gradually increasing secondary dilution in the dilution zone, by using progressively larger diameter holes. This design would help retain relatively high temperature in the initial portion of the dilution zone and would help consume fuel species such as, CO and CH4.
It appears that, for sCO2 combustors “lean burn” is the better strategy over stoichiometric burning to eliminate CO build up at the combustor exit. The lean burn condition at equivalence ratio (ϕ) equal to 0.9 is recommended for sCO2 combustor operation. Also, the length of the dilution zone can be scaled-down to 50% by lean burn operation of the combustor. It is also observed that the lean burn increases the net turbine power. Current work provides crucial design considerations for the development of advanced sCO2 combustors to be used with direct-fired power cycles.
Alternative Aviation Fuels Evaluated for Lean-Flame NOx and Blowout, and Rich-Flame Soot Threshold
Authors: Hoseyni Chime Arshiya , Kalia Aman , Kramlich John , Novosselov Igor , Malte Philip C. , Vijlee Shazib 
Published: August 2018

Alternative aviation fuels are evaluated for lean-flame NOx formation, lean-flame blowout (LFBO), and rich-flame soot threshold. The alternative aviation fuels evaluated are: hydro-processed renewable jet (HRJ) made from camelina and tallow, Fischer-Tropsch (FT) jet made from coal and natural gas, and alcohol-based jet. Chromatographic analysis (from another lab) shows that these fuels are composed mainly of iso-alkanes. These fuels are burned as received and with 10–20% aromatic added. For comparison, petroleum-based jet fuels are burned: JP5, JP8, Jet-A, and an aromatic blend. Additionally, we burn several pure fuels: n-hexane, cyclo-hexane, n-octane, iso-octane, n-dodecane, 1-3-5 tri-methyl benzene (TMB), and toluene. The NOx and blowout experiments are performed in a jet-stirred reactor (JSR), and the soot threshold experiments are performed on a Meker burner. The fuels are burned pre-vaporized, premixed, and preheated.
NOx is measured by probe sampling and chemiluminescent analysis at a fixed temperature for each fuel. Soot tendency is measured as the fuel-air equivalence ratio (phi) for the first appearance of yellow tips in the flame. This is termed the soot threshold. LFBO is examined by measuring the JSR temperature immediately prior to blowout.
Relatively small changes in NOx, LFBO, and soot threshold are measured for the petroleum-based and alternative jet fuels examined. HRJ-tallow is the cleanest burning jet fuel tested with respect to NOx and soot measurements. It exhibits the lowest NOx and the highest soot threshold among alternative fuels tested.
A possible correlation between decreasing NOx and increasing soot threshold is explored. The impact of adding aromatic content to the alternative jet fuels is also examined. With 20% aromatic content added to the alternative jet fuels, the soot threshold decreases, though the HRJ-tallow with 20% aromatic added continues to maintain a higher soot threshold than petroleum-based jet fuels. The addition of 20% aromatic does not show a clear trend in NOx. Over the four alternative jet fuels tested, the 20% aromatic addition causes a maximum change in the NOx emission of ± 13% (relative); the average change is close to zero.
Gas Turbine Fouling Offshore: Air Intake Filtration Optimization
Authors: Madsen Stian , Watvedt Jørn , Bakken Lars E. 
Published: August 2018

Optimized operation of gas turbines is discussed for a fleet of eleven LM2500PE engines at a Statoil North Sea offshore field in Norway. Three engines are generator drivers while eight engines are compressor drivers. Several of the compressor drive engines run at peak load (T5.4 control), hence production rate is limited by the available power from these engines. The majority of the engines discussed run continuously without redundancy, hence gas turbine uptime is critical for the field’s production and economy. The performance and operational experience with upgraded inlet air filter systems, as well as successful operation at longer maintenance intervals and higher average engine performance are described.
For North Sea operation, a key property of the filter system is the ability to handle high humidity and high salt-content, typical of the harsh environment in these waters. The upgraded filter system analyzed in this paper is a 2-stage system (vane separator stage upstream of the high-efficiency filter stage), which is a simplified design versus the old traditional 3-stage systems (louvre upstream and vane separator downstream of the filter stage). These 2-stage systems rely on an efficient upstream vane separator to remove the vast majority of water from the airflow before it reaches the high-efficiency filters. The high-efficiency filters are specially designed to withstand moisture. The effectiveness and contribution of each component in the filtration system are described. Extensive testing of both new and used filter elements, of different filter grade and operated at different intervals, has been performed in a filter test rig facility onshore. Extensive testing of used filters has also been performed at the filter OEM, where filter efficiency is measured as well as destructive testing and analysis of the filter layers.
The effect of an optimized air intake filter system for the subject engines, is longer operating intervals, higher power availability and lower engine deterioration. The operating intervals are now extended to six months (4,000 hours), from initially two months (1,500 hours, early 1990s) then four months (3,000 hours, mid 2000s). The HPC efficiency deterioration is reduced by some 3% related to intake filter system, of a total of over 6% in efficiency deterioration over each 6-month operating period.
Impact of Upstream Boundary Conditions on Fuel Injector Performance in a Low TRL Reacting Flow Experimental Facility
Authors: Williams M. A. , Carrotte J. F. , Moran A. J. , Walker A. D. 
Published: August 2018

It has been known for a sometime that the compressor exit profile can have a significant effect on the overall performance of the fuel injector. This effect has been increased recently with the advent of larger leaner injection systems. With a modern gas turbine combustion system the fuel injectors are presented with a non-uniform feed generated by the upstream compressor and OGV/pre-diffuser assembly. For generic lean burn combustion systems previous experimental and numerical work highlighted a complex interaction between the compressor efflux and the upstream diffuser. Circumferential non-uniformities in the flow presented to the fuel injector can amount up to ±10% of the mean velocity. Previous investigations examined only the isothermal flow field and the effects of this level of non-uniformity on reacting performance are not known. There are potential impacts on local fuel atomisation, air/fuel mixing and hence emissions performance.
The main aim of this paper is to observe and assess the effect of these upstream conditions using a reacting flow test facility. In the initial design phases reacting flow experiments are generally conducted in simple, single sector plenum fed test facilities. Since this does not capture the effects of non-uniformities modifications were made to the facility to produce an aerodynamically representative feed. CFD was used in the design process to ensure that the aerodynamic features present in engine geometries would be faithfully reproduced by the test rig modifications. The CFD also highlighted changes in the downstream isothermal flow field. This included differences in the overall effective area of the fuel injector and, importantly, a redistribution of mass flow between the various fuel injector passages. Additionally, the cone angle, and the flow structure downstream was observed to change.
Back-to-back tests were then conducted in a reacting flow test facility for various pilot-mains fuel flow splits and air-to-fuel ratios. Visualisation of the flame showed notable qualitative differences in the structure and stability of the flame. Quantitative measurements indicated that, compared to a plenum feed, a representative feed produced changes in the production of carbon monoxide, unburned hydrocarbons and oxides of nitrogen. Emission results were used to calculate the extent of the mass flow redistribution between passages. From this a correction was applied to the estimated AFRs. This correction did not fully collapse the emissions data, suggesting that while the mass flow redistribution contributes to the change in emissions it is not fully responsible. Covered in this paper are initial observations. However, further work is required to fully understand how the changes to the aerodynamic flow field alter the emissions performance, but it is clear that having a representative fuel injector feed is important in low TRL testing.
Using Robust Design Methods for the Fir-Tree Optimization Problem
Authors: Vasilyev Boris , Salnikov Anton , Semenov Artem 
Published: August 2018

The difficulty of providing the required strength characteristics of wheel locking joints is due to a complex stress state, the presence of stress concentrators, differences in contacting-part materials’ characteristics, and possible deviations in sizes from nominal values [1]. Providing stable strength characteristics and a low mass are important requirements. This paper suggests an approach to the strength-mass optimization of a disc and fir-tree joint of a high-pressure turbine and considers the scattering of dimensions within tolerances.
The main stages of optimization are shown, criteria for evaluating the robustness of the structure are proposed, and recommendations for the practical robust optimization of a real design are given. The results of various optimization approaches and strength-parameter dispersions of various configurations’ locking joints are compared. It is shown that decreasing the number of teeth increases the stability of the strength parameters.
Adjoint Method to Calculate the Shape Gradients of Failure Probabilities for Turbomachinery Components
Authors: Gottschalk Hanno , Saadi Mohamed , Doganay Onur Tanil , Klamroth Kathrin , Schmitz Sebastian 
Published: August 2018

In the optimization of turbomachinery components, shape sensitivities for fluid dynamical objective functions have been used for a long time. As peak stress is not a differential functional of the shape, such highly efficient procedures so far have been missing for objective functionals that stem from mechanical integrity. This changes, if deterministic lifing criteria are replaced by probabilistic criteria, which have been introduced recently to the field of low cycle fatigue (LCF).
Here we present a finite element (FEA) based first discretize, then adjoin approach to the calculation of shape gradients (sensitivities) for the failure probability with regard to probabilistic LCF and apply it to simple and complex geometries, as e.g. a blisk geometry.
We review the computation of failure probabilities with a FEA postprocessor and sketch the computation of the relevant quantities for the adjoint method. We demonstrate high accuracy and computational efficiency of the adjoint method compared to finite difference schemes. We discuss implementation details for rotating components with cyclic boundary conditions. Finally, we shortly comment on future development steps and on potential applications in multi criteria optimization.
Detection of Strain and Damage Distribution in SiCf/SiC Mechanical Test Coupons
Authors: Newton Christopher D. , Jones J. Paul , Gale Louise , Bache Martin R. 
Published: August 2018

The complex structural architecture and inherent processing artefacts within ceramic matrix composites combine to induce inhomogeneous deformation and damage prior to ultimate failure. Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in ceramic matrix composites. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states.
Bulk measurements of strain via extensometry or even localised strain gauging will fail to characterise such inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research project has, therefore, applied digital image correlation (DIC), electrical resistance monitoring and acoustic emission techniques to the room and high temperature assessment of a SiCf/SiC composite under axial fatigue loading.
Data from these separate monitoring techniques plus ancillary use of X-Ray computed tomography and optical inspection were correlated to monitor the onset and progression of damage during cyclic loading.
Experimental and Numerical Study of Critical Flow Model Development for Supercritical CO2 Power Cycle Application
Authors: Kim Min Seok , Oh Bong Seong , Jung Hwa-Young , Bae Seong Jun , Lee Jeong Ik 
Published: August 2018

Supercritical CO2 (S-CO2) has the potential to be used as the working fluid in a power cycle since S-CO2 shows a density value high as its liquid phase while the viscosity value remains closer to its gaseous phase. Thus, it requires much less work to compress due to its low compressibility as well as relatively small flow resistance. However, the S-CO2 leakage flow from turbo-machinery via seal becomes one of the important issues since not only it influences the cycle efficiency due to parasitic loss but also it is important for evaluating the system safety under various operating conditions.
In the previous turbo expo paper, the effect of the tooth length on the critical flow and comparing the results to the existing two phase system analysis code calculation were presented. In this paper, the gap effect, which is simulated by changing the diameter of a orifice and the number of tooth effect in a labyrinth seal geometry nozzle are presented by using the same experimental facility described in the previous paper. In addition, this paper includes the experimental results under various conditions including not only single phase flow such as supercritical, and gaseous state only but also two phase flow condition.
The Influence of Geometry Deformation on a Multistage Compressor
Authors: Teng Xin , Chu WuLi , Zhang HaoGuang , Liu Kai , Li JinGe 
Published: August 2018

Over the service time, the rotating parts of turbine engine vary in their geometry. When aircraft take off or fly through a volcanic ash cloud, the particles are sucked into the engine, impinge the blade and gradually erode the surface. The impinging between particles and blades is responsible for the increase of the surface roughness. Also, during the long-time operation, the function of the blade’s stacking law combined with the centrifugal force could cause deviation of the stagger angle. Moreover, blade tip clearance could vary because of the casing deformation. All the deformation of geometry could severely reduce the engine performance and thus engine life.
The work presented in this paper focused on the influence of geometry deformation in a real low-pressure compressor. The investigation is more difficult than most of the previously published researches with a total of five stages being considered. Due to the irregularities in geometry, it is difficult to numerically assess the performance of the compressor. The aim of this study is to give an analysis method that allows an efficient and accurate estimation of the performance for multistage compressor with geometry deformation. In the first step, the geometry models with different deviation in tip clearance, roughness and stagger angle were established respectively. A CFD study was then applied to the compressor with RANS method to calculate the flow field with different types of deformation. The variation of overall performance due to the deformation was finally analyzed to identify the dominant factor on influencing the performance of the compressor among different types of geometry deformation. A method based on polytropic efficiency analysis and flow field analysis was also established to specifically analyze which stage is most sensitive to the geometry deformation.
The results show a significant influence of geometric deformation on the efficiency, total pressure rise and flow range of the multistage compressor. The conclusions of this study would provide an important guidance for engine overhaul in the factory.
Advanced Film Cooling Performance of a Y-Shaped Hole With Inner Crossflow
Authors: Luo Jianxia , Liu Cunliang , Zhu Huiren 
Published: August 2018

Film cooling performances of three film holes have been numerical researched in this paper, including a lateral inclined cylindrical hole, a fan-shaped hole and a y-shaped hole. The simulation is computed by the commercial software Fluent based on Reynolds Averaged Navier-Stokes (RANS) equations and realizable k-ε turbulence model with enhanced wall treatment.
The y-shaped hole is a novel film hole developed from the lateral inclined cylindrical hole. With inner crossflow, the jet of the lateral inclined cylindrical hole performs to be two streams as a result of the helical motion in the hole. Accordingly, the hole exit was optimized with two expansions: one is expanded along the lateral inclined direction and the other is expanded along the mainstream flow direction. The lateral inclined cylindrical hole with two expansions at the exit is named the y-shaped hole. Compared to the fundamental lateral inclined cylindrical hole, the y-shaped hole has different counter-rotating vortices and much better film coverage.
Experiments have been conducted to test the film cooling performance of the y-shaped hole. Compared to the lateral inclined cylindrical hole, much higher film cooling effectiveness has been measured in the y-shaped hole as a result of the enhanced lateral film coverage and the weakened film dissipation in the streamwise direction. The film performance of the y-shaped hole rises with the increase of the blowing ratio. At M = 2.0, the film of the y-shaped hole keeps close to the wall while the film of the lateral inclined cylindrical hole is completely lifted up, resulting in the increase of the area average film cooling effectiveness up to 128.7%.
Numerical Investigations to Assess the Impact of Shaft Speed on the Performance of Scoop Devices
Authors: Prabhakar Arun , Abakr Yousif Abdalla , Simmons Kathy 
Published: August 2018

The demand for continuous and efficient lubrication in aeroengine bearing assemblies has encouraged the development of scoop based lubrication systems. Using a scooped rotor in conjunction with axial passages within the shaft, a scoop system can provide lubrication to bearings and other components at a different axial location to the oil supply jet, optimizing the use of space.
The capture efficiency of a scoop system is the percentage of oil from the jet that is delivered to the desired end location. It is dependent on a number of factors such as shaft rotational speed, oil jet speed and other geometrical features. In this paper the impact of shaft speed on the capture efficiency of a scoop system is predicted numerically using Computational Fluid Dynamics (CFD). An analytical study has been also carried out to aid the understanding of the system’s behaviour. A simplified 2D geometry is used for the computational domain in the numerical simulations. The Volume of Fluid (VOF) multiphase model has been implemented to simulate the flow of oil and air. The effects of turbulence are modelled using the RNG K-ε turbulence model. Results obtained using CFD are compared to experimental results obtained from tests conducted on the same geometry.
It is evident from CFD and experiments that for a fixed oil jet velocity there is an optimum shaft speed at which maximum capture efficiency is obtained. This is somewhat higher than the threshold value identified by the analytical study at which 100% capture becomes theoretically possible. Maximum capture efficiencies of around 80% are predicted. Some oil is uncaptured because it forms a plume ahead of the scoop tip and deflects outwards and some is initially captured but leaves the scoop through centrifugal effects.
The analytical model suggests that the point of jet strike on the scoop may affect/control losses due to centrifugal effects with more oil being lost when the point of strike is closer to the scoop tip. Pluming losses become more significant at higher shaft speeds because the angle over which oil is captured decreases.
Predicted scoop capture efficiencies obtained using CFD are within 5.5% of experimentally obtained results for the configuration investigated here. Trends in behavior are the same experimentally and computationally highlighting the usefulness of a 2D CFD modelling approach.