bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Third Substances at the Particle/Surface Interface in Compressor Fouling
Authors: Aldi Nicola , Casari Nicola , Dainese Devid , Morini Mirko , Pinelli Michele , Spina Pier Ruggero , Suman Alessio 
Published: August 2017

Since the beginning of the 1950s, manufacturers and operators have struggled to understand, reduce and eliminate compressor fouling and its effects on gas turbine operation. Several devices (inertial separators, barriers, filters, etc.) and strategies (on-line and off-line washing, manual cleaning, etc.) have been adopted in order to limit and/or eliminate the foulants which stick to the compressor blade and vane surfaces.
The state of the power plant design and installation and environmental conditions determine the rate of fouling and, in turn, gas turbine performance losses. The types of contaminant (organic or inorganic), their concentration and their ability to stick are variable depending on the weather conditions. Desert, tropical, rural, and off-shore conditions are characterized by different foulants with different characteristics which determine compressor fouling.
In this paper, an analysis of the influence of third substances at the particle/surface interface is presented. The analysis is carried out on two different compressor rotors, transonic and subsonic. Firstly, a sensitivity analysis is proposed related to the particle diameter and foulant mixture in order to highlight the influence of air humidity due to environmental conditions or the pressure drop after the filtration stages. The effects of a water electrolytic solution (generated by the presence of inorganic matter) and a water surfactant solution (used in the case of washing) are also considered. In this case, the properties of the mixture substance (solid particles bound by a liquid film) are considered. Secondly, using previous numerical analyses (particle-laden flow with a Eulerian-Lagrangian approach) as a starting point, the variation in particle sticking ability is evaluated against the presence of third substances (water solutions and oily substances) and the particle kinematic characteristics using a sticking model based on an energy balance equation.
The results show the influence of the third substance on particle sticking capability using a susceptibility-to-fouling criterion. Particularly in the presence of humid conditions, sticking capability increases with respect to dry conditions, even though the major effects are due to the mixture viscosity and not only to the presence of liquid water. The sticking capability of the mixture varies according to particle diameter as a function of the particle normal velocity. The results are presented in order to easily quantify the effects of the presence of a third substance at the particle/surface interface according to the type of liquid phase involved in the sticking process.
A Study of Spontaneous Transition in Swirl-Stabilized Flames
Authors: Boxx Isaac , Carter Campbell D. , Geigle Klaus Peter , Meier Wolfgang , Akih-Kumgeh Benjamin , Lewalle Jacques 
Published: August 2017

The goal of this study was to select and test some analysis tools to identify and characterize precursors to the onset of thermo-acoustic pulsation in a gas turbine combustor. The target flame was a turbulent, swirl-stability ethylene-air flame operated at ϕ = 0.91, and 5 bars pressure. 3-component stereo-particle image velocimetry (PIV) measurements, acquired at 9.3 kHz over periods of approximately 4 seconds were used to characterize the flow-field near the exit plane of the combustor. Acoustic measurements and OH*-chemiluminescence images were acquired synchronously, with OH* images acquired at every third cycle of the PIV measurement system.
Analysis revealed the presence of two characteristic frequencies in the data for the stable flame; a 475 Hz oscillation associated with the shear-layer dynamics and a weak thermo-acoustic oscillation 610 Hz. In the excited state, a 720 Hz self-excited thermo-acoustic oscillation dominated combustor dynamics. A possible precursor event was identified in the form of a 635 Hz oscillation that appeared in the data 0.15s prior to transition. Bandpass filtering of the velocity data at this frequency showed this oscillation originates in the outer recirculation zone of the combustor.
Influence of Detailing on Aerodynamic Forcing of a Transonic Axial Turbine Stage and Forced-Response Prediction for Low-Engine-Order (LEO) Excitation
Authors: Müller Tobias R. , Vogt Damian M. , Vogel Klemens , Phillipsen Bent A. , Hönisch Peter 
Published: August 2017

The effects of detailing on the prediction of forced-response in a transonic axial turbine stage, featuring a parted stator design, asymmetric inlet and outlet casings as well as rotor cavities, is investigated. Ensuring the mechanical integrity of components is of paramount importance for the safe and reliable operation of turbomachines. Among others, flow induced resonance excitation can lead to high-cycle fatigue (HCF) and potentially to damage of components unless properly damped. This numerical study is assessing the necessary degree of detailing in terms of spatial and temporal discretization, boundary conditions of the pre-stressed rotor geometry as well as geometrical detailing for the reliable prediction of the aerodynamic excitation of the structure. In this context, the sensitivity of the aerodynamic forcing is analyzed by means of the generalized force criterion, showing a significant influence for some of the investigated variations of the numerical model.
Moreover, the origin and further progression of several low-engine-orders (LEO) within the flow field, as well as their interaction with different geometric details has been analyzed based on the numerical results obtained from a full 360° CFD-calculation of the investigated turbine stage. The predicted flow induced vibration of the structure has been validated by means of a full forced-response analysis, where a good agreement with tip-timing data has been found.
Design of a Single Stage Variable Pitch Axial Fan
Authors: Bonanni Tommaso , Corsini Alessandro , Delibra Giovanni , Volponi David , Sheard Anthony G. , Bublitz Mark 
Published: August 2017

The European Union imposed minimum industrial fan efficiency levels in 2013 and then increased them in 2015. In the USA, the Department of Energy (DoE) is also developing regulations aimed at eliminating inefficient industrial fans from the market by 2023. A consequence of this regulatory activity is a need to apply design methods originally developed within the aerospace community to the design of high efficiency industrial fans.
In this paper, we present a process used to design, numerically verify and experimentally test a high-pressure single-stage axial fan. The goal was a fan design capable of working over a range of blade angles in combination with a single fixed cambered plate stator. We present the process used when selecting blade airfoil sections and the vortex distribution along the blade span. The selected methodology is based on a coupling between the aerodynamic response of each blade profile and the chosen vortex distribution, creating a direct link between the load distribution and the aerodynamic capability of the blade profile section. This link is used to develop radial distributions of blade twist and chord for the selected blade profiles that result in the required radial work distribution.
The design method has been enhanced through intermediate verifications using two different numerical methodologies. The methodologies are based on different approaches, in so doing providing confidence in the verification process. The final blade design has been analyzed using a three-dimensional computational fluid dynamic (CFD) code. Results of the CFD analysis indicate that performance of the final blade design is consistent with the design specifications.
The paper concludes with a comparison between predicted and experimentally measured performance. The need is clarified for balance between computational and empirical approaches. When used together the development effort results in a lower cost and higher efficiency design than would have been possible using either approach in isolation.
Development of Direct-Driven and Geared Fan Stages With Reduced Tip Speeds
Authors: Pankov S. V. , Mileshin V. I. , Orekhov I. K. , Fateev V. A. 
Published: August 2017

This work presents the latest results of aeromechanical design of two large-scale fan model stages (Dr = 700 mm) for low-noise high-performance single-stage fan prototypes designed for advanced civil aircraft geared and direct-driven turbofans with reduced and ultra-low rotor tip speeds, high specific capacity, and high bypass ratios. They are designed with account of all features of blades made of polymer composite materials (PCM) or titanium alloy. Metal and composite blades have a similar shape in hot state at the design point. The stages are intended for tests in the anechoic chamber of the CIAM’s C-3A special acoustic test facility with the aim of verification new optimal design methods for similar fans to achieve maximum performance.
Performances of the fans and parameters of viscous steady flows are calculated. The calculations show that both fan models can provide a high specific capacity along with a high efficiency and sufficient stall margins. For example, calculated max. efficiency level of the bypass duct in the geared model fan with ultra-low tip speed (Ucor. = 313.4 m/s) is equal to 94%.
Data measured by tests of an ungeared bypass fan model with solid metal rotor blades developed earlier by the authors are used for the mathematical model verification. Tip speed of rotor blades at the design point is Ucor. = 400m/s, bypass ratio — m = 8.4. Four booster stages are installed in the core duct. From first test results it is clear that required values of key parameters are achieved. Comparison of measured and calculated data gives evidence of their good agreement. At present, detailed tests of this fan and a similar fan with 3 booster stages are under way in the anechoic chamber of the CIAM’s C-3A acoustic test facility.
The new direct-driven fan model described in this paper has quite different design values of parameters, geometry of the meridian contours, and shapes of outer and inner ducts. Tip speed of its rotor blades is reduced by 30 m/s, the hub diameter is decreased, and bypass ratio is higher (m = 11).
In the near future, these two new models of non-geared and geared fans can be manufactured and tested.
Optimization of Operating Parameters of a Recompression sCO2 Cycle for Maximum Efficiency
Authors: Sathish Sharath , Kumar Pramod , Namburi Adi Narayana , Gopi Pramod Chandra , Carlson Matthew D. , Ho Clifford K. 
Published: August 2017

Supercritical CO2 power systems offer significant power density advantages along with high efficiencies, compared to traditional Rankine or Brayton cycles. Of the several viable configurations, the recompression cycle has higher efficiency compared to the simple recuperated cycle for source temperatures above 500°C. It also provides a good trade-off between efficiency and plant complexity. This paper explores the dependence of critical operational parameters on source and sink-temperature, which is then used as a means to generate guidelines for developing recompression sCO2 power plants. The maximum source temperature in the analysis is restricted to 565°C to take advantage of the existing materials and technologies associated with industrial steam turbines. However, the methodology described herein is applicable for any other source temperature range.
An important source of thermal efficiency degradation in power plants is attributable to heat exchangers. Analysis presented in this work directly relates the optimum operational parameters of the recompression cycle to the operation of the low temperature recuperator. Thermodynamic analysis confirms that a recompression fraction of 0.25 and pressure ratio of 2.5 is as an optimum design point for the recompression cycle. The penalty in efficiency and power while operating the plant in off-design conditions for a fixed recompression fraction and pressure ratio is highlighted.
Numerical Simulation of a Particle-Laden Impinging Jet: Effect of Wall Curvature on Particle Deposition
Authors: Agati Giuliano , Borello Domenico , Rispoli Franco , Salvagni Alessandro , Venturini Paolo 
Published: August 2017

Jet impingement against surfaces is uses in several industrial applications, including the internal cooling of turbine blades. Coolant used for blade cooling is air bleed from a compressor and is laden with particles.
A numerical simulation of a particle-laden impinging jet is here proposed, aiming at studying and analysing the effect of surface curvature on flow field, particle motion and deposit formation. To this aim, an impinging jet on a flat and a curved walls is considered. Flow motion is be solved using Direct Numerical Simulation, thus no additional model is needed for turbulence effect on particle motion.
Results show that the deposit patterns follow some secondary flow structures, showing a series of peaks forming according to those structures. The peaks are present in both the main orthogonal direction of the jet, but they are not symmetrical due to surface curvature.
Modelling of Hot Surface Ignition Within Gas Turbines Subject to Flammable Gas in the Intake
Authors: Pedersen Lea Duedahl , Nielsen Kenny Krogh , Yin Chungen , Sørensen Henrik , Fossan Ingar 
Published: August 2017

Controlling risks associated with fires and explosions from leaks of flammable fluids at oil and gas facilities is paramount to ensuring safe operations. The gas turbine is a significant potential source of ignition; however, the residual risk is still not adequately understood.
A model has been successfully developed and implemented in the commercial Computational Fluid Dynamics (CFD) code ANSYS CFX. This model is based on a combination of standard models, User Defined Functions (UDFs) and the CFX Expression Language (CEL). Prediction of ignition is based on a set of criteria to be fulfilled while complex kinetics is handled computationally easy by means of a reaction progress variable.
The simulation results show a good agreement with the trends experimentally observed in other studies. It is found that the hot surface ignition temperature (HSIT) increases with increase in velocity and turbulence but decreases with increase in initial mixture temperature and pressure.
The model shows a great potential in reliable prediction of the risk of hot surface ignition within gas turbines in the oil and gas industry. In the future, a dedicated experimental study will be performed not only to improve the understanding of the risk of hot surface ignition but also to collect experimental data under well-defined conditions to further validate or refine the model.
Effect of Active Modulation of Through-Casing Coolant Injection on Turbine Efficiency
Authors: Tang Brian M. T. , Bacic Marko , Ireland Peter T. 
Published: August 2017

This paper presents a computational investigation into the impact of cooling air injected through the stationary over-tip turbine casing on overall turbine efficiency. The high work axial flow turbine is representative of the high pressure turbine of a civil aviation turbofan engine. The effect of active modulation of the cooling air is assessed, as well as that of the injection locations. The influence of the through-casing coolant injection on the turbine blade over-tip leakage flow and the associated secondary flow features are examined. Transient (unsteady) sliding mesh simulations of a one turbine stage rotor-stator domain are performed using periodic boundary conditions. Cooling air configurations with a constant total pressure air supply, constant mass flow rate and actively controlled total pressure supply are assessed for a single geometric arrangement of cooling holes. The effects of both the mass flow rate of cooling air and the location of its injection relative to the turbine rotor blade are examined.
The results show that all of the assessed cooling configurations provided a benefit to turbine row efficiency of between 0.2 and 0.4 percentage points. The passive and constant mass flow rate configurations reduced the over-tip leakage flow, but did so in an inefficient manner, with decreasing efficiency observed with increasing injection mass flow rate beyond 0.6% of the mainstream flow, despite the over-tip leakage mass flow rate continuing to reduce.
By contrast, the active total pressure controlled injection provided a more efficient manner of controlling this leakage flow, as it permitted a redistribution of cooling air, allowing it to be applied in the regions close to the suction side of the blade tip which more directly reduced over-tip leakage flow rates and hence improved efficiency. Cooling air injected close to the pressure side of the rotor blade was less effective at controlling the leakage flow, and was associated with increased aerodynamic loss in the passage vortex.
Case for Exploring Compressor Water Injection for Airport Emission Reduction
Authors: Block Novelo David Alejandro , Igie Uyioghosa 
Published: August 2017

The increasing world population, higher accessibility to air transportation, coupled with new low-cost airline models has resulted in an unprecedented increase in demand for civil aviation. The industry is currently experiencing a global increase of operational civil aircraft at a rate of 5–6% annually. This growth suggests a vibrant future for the industry, however, the environmental implications and the footprint is worth considerable attention given the expected scale of growth in the industry and the possible side effects to human health. The stakeholders involved, some of which include: airports and airline operators, jet engine and airframe manufacturers and various government bodies, are introducing measures in order to mitigate the increase in certain emissions and hence their impact.
This study focuses on one of the many existing approaches targeting the reduction in gaseous emissions, predominantly nitrogen oxides (NOx). This is through compressor water injection that is estimated to reduce NOx emissions by almost half under certain ambient conditions and water-to-air ratio. Apart from reviewing this technology, the study, more importantly, presents the ideas in relation to other major existing approaches/concepts.
It would be observed that compressor water injection can be more readily applied to the existing infrastructure when compared to other approaches. This technique is one of the most promising methods for reducing NOx emissions, an area of particular importance given that modern engines, though more thermally efficient, operate at higher pressure ratios and flame temperature, both of which enhance nitrogen oxides formation.
One of the main contributions of this paper is the categorisation of existing approaches focused on reducing aircraft-borne airport emissions. Different technologies and operational changes are classified according to the key pollutants that they target with respect to the landing and takeoff cycle based on 11 different engine types. These gaseous-emissions mitigating approaches are analyzed based on their individual merits, limitations and feasibilities. Compressor water injection is re-introduced here as a more readily applicable solution despite its technological challenges, many of which can be better resolved with today’s knowledge.
Variable Inlet Guide Vane Losses and Their Effect on Downstream Impeller and Diffuser in Wet Gas Flow
Authors: Vigdal Levi André B. , Bakken Lars E. 
Published: August 2017

Adopting the innovative technology found in a compressor able to compress a mixture of natural gas and condensate has great potential for meeting future challenges in subsea oil and gas production. Benefits include reduced size, complexity and cost, enhanced well output, longer producing life and increased profits, which in turn offer opportunities for exploiting smaller oil and gas discoveries or extending the commercial life of existing fields.
Introducing liquid into a centrifugal compressor creates several thermodynamic and fluid-mechanical challenges. The paper reviews some of the drive mechanisms involved in wet gas compression and views them in the context of the test results presented. An inlet guide vane (IGV) assembly has been installed in a test facility for wet gas compressors and the effect of wet gas on IGV performance documented. The impact of changes in IGV performance on impeller and diffuser has also been documented. The results have been discussed and correction methods compared.
Limit Cycles of Spinning Thermoacoustic Modes in Annular Combustors: A Bloch-Wave and Adjoint-Perturbation Approach
Authors: Mensah Georg A. , Moeck Jonas P. 
Published: August 2017

The most straightforward way to assess the thermoacoustic stability of a combustion system is based on modal approaches. The modes are typically computed from linearized equations in the frequency domain, such as the Helmholtz equation. Due to the linear character, nonlinear saturation effects cannot be computed with such models. Flame describing functions have been suggested to fill this gap. They describe the flame response in an amplitude-dependent manner and have been successfully used in recent work for the prediction of limit-cycle amplitudes in single-burner systems and annular combustors.
This paper presents a more efficient approach of computing limit-cycle amplitudes of spinning thermoacoustic modes in an annular combustion chamber. As one important feature, adjoint perturbation theory is utilized for the solution of the thermoacoustic Helmholtz equation associated with a flame describing function. This avoids iterations over different amplitude levels to find the limit cycle amplitude, i.e., the amplitude level at which the modal growth rate is zero, as required in previous approaches. Moreover, based on the discrete rotational symmetry of the system, the computation is also accelerated by means of Bloch-wave theory, which reduces computations for annular combustors to a single burner/flame segment.
Results for a generic model and a laboratory-scale annular combustion system are presented and discussed.