bluuebunny/crossref_metadata_2025 huggingface dataset:
3-D Flow Structures Around and Fluid-Dynamic Forces Acting on a Rectangular Cylinder in Oscillatory Flow
Authors: Yasuda Takahiro , Okajima Atsushi , Moriyoshi Minoru
Published: February 2009

Three-dimensional flow structures around and fluiddynamic forces acting on a rectangular cylinder in oscillatory flow were investigated by numerical simulation using finite volume method. The computations were carried out for three kinds of cross-sections with width/height ratio (d/H) d/H = 0.6, 1.0 and 2.0 and for the amplitude of oscillating flow in the range of 2.5 ≤ the Keulegan-Carpenter number (KC) ≤ 25, the Stokes number (β) = 95. The calculated flow patterns and the drag and inertia force coefficients of Morison equation acting on the cylinder were compared with the experimental ones using a U-tube water tank. In this paper, we note how the KC number and the width/height ratio of the cylinders affect the unsteady and three-dimensional flow structures such as the “longitudinal vortices” and “transverse street” which formed in the case of a circular cylinder fixed in oscillatory flow, and how the CD and the CM values of Morison coefficients change corresponding to the change of the behavior of the flow patterns. Furthermore the relationship between spanwise correlation coefficient of the transverse force R(x3), where x3 is the spanwise position from the bottom of the cylinder, and three-dimensional vortex structures were investigated.
Simulation Results for Micro-Bubbles and Turbulent Drag Reduction (Keynote)
Authors: Maxey M. R. , Xu J. , Dong S. , Karniadakis G. E.
Published: February 2009

A series of numerical simulations of small bubbles seeded in a turbulent channel flow have been made at average void fractions up to 10%. Initial near-wall seeding in general leads to a transient reduction in drag while smaller bubbles are more effective in producing sustained drag reduction.
Microbubble Drag Reduction in Rough Walled Turbulent Boundary Layers
Authors: Deutsch Steven , Moeny Michael , Fontaine Arnold , Petrie Howard
Published: February 2009

Experiments were conducted in the 12-inch diameter tunnel at ARL/PSU using the tunnel wall boundary layer facility to determine the influence of surface roughness on microbubble drag reduction. To accomplish this, carbon dioxide was injected through a slot at rates of 0.001 m3/s to 0.011 m3/s, and the resulting skin friction drag measured on a 317.5 mm long by 152.4 mm span balance. In addition to the hydrodynamically smooth balance plate, additional plates were covered with roughly 75, 150 and 300 micron grit. Over the speed range tested of 7.6, 10.7 and 13.7 m/s, the roughness ranged from smooth to fully rough. Not only was microbubble drag reduction achieved over the rough surfaces, but the percentage drag reduction at a given gas flow rate was larger for larger roughness. A new scaling parameter that collapses all of the data is also introduced.
Experimental Study on the Drag Reduction by Injection of Microbubble and Polymer Solution in a Water Tunnel for Water-Borne Vehicles
Authors: Yoon Hyun-Se , Kim Dug-Soo , Kim Wu-Joan , Song Museok , Kim Hyoung-Tae , Van Suak-Ho
Published: February 2009

Experiments on the friction drag reduction by injecting microbubbles or polymer solutions have been carried out for both a flat wall and an axisymmetric body. In the first setup, the drag reduction on the flat ceiling of a water channel was measured for a fully developed turbulent channel flow by using a newly developed skin friction sensor of floating element type. The effects of key controlling parameters were investigated for higher drag reduction with varying the concentration and the injection rate of the additives. The integrated frictional drag has been reduced up to 25% with the microbubble injection and 50% with the polymer solution injection. The drag reduction for a slender axisymmetric body was also investigated in a cavitation tunnel based on the parameters obtained from the channel experiments.
Rheological Characterization of Drag-Reducing Cationic Surfactant Solution: Shear and Elongational Viscosities of Dilute Solutions
Authors: Kawaguchi Yasuo , Wei Jinjia , Yu Bo , Feng Ziping
Published: February 2009

Shear viscosities of one kind of turbulent drag-reducing cationic surfactant solution, Cetyltrimethyl ammonium chloride (CTAC)/Sodium salicylate (NaSal) aqueous solution, were experimentally investigated by use of a stress controlled Reometer. The concentration and temperature of the solution ranged from 50 to 200 ppm and 20 to 40°C, respectively. The Giesekus model was found to fit the measured shear viscosities well for different temperatures and concentrations of the surfactant solution and the model parameter values obtained by fitting were correlated with temperature at certain solution concentrations. The temperature was found to have a large influence on the viscoelasticity of the surfactant solution. By using the model parameters obtained from the correlations, 70 percent of the measured shear viscosities agreed with the prediction by the Giesekus model within ±27.3 percent. The elongational viscosities of CTAC/NaSal surfactant solution were also experimentally investigated by use of an oppositing jet Reometer. The measured data were lower than the prediction by the Giesekus model.
Multiphase Flow and Phase Change in Microgravity: Fundamental Research and Strategic Research for Exploration of Space
Authors: Singh Bhim S.
Published: February 2009

NASA is preparing to undertake science-driven exploration missions. The NASA Exploration Team’s vision is a cascade of stepping stones. The stepping-stone will build the technical capabilities needed for each step with multi-use technologies and capabilities. An Agency-wide technology investment and development program is necessary to implement the vision. The NASA Exploration Team has identified a number of areas where significant advances are needed to overcome all engineering and medical barriers to the expansion of human space exploration beyond low-Earth orbit. Closed-loop life support systems and advanced propulsion and power technologies are among the areas requiring significant advances from the current state-of-the-art. Studies conducted by the National Academy of Science’s National Research Council and Workshops organized by NASA have shown that multiphase flow and phase change play a crucial role in many of these advanced technology concepts. Lack of understanding of multiphase flow, phase change, and interfacial phenomena in the microgravity environment has been a major hurdle. An understanding of multiphase flow and phase change in microgravity is, therefore, critical to advancing many technologies needed. Recognizing this, the Office of Biological and Physical Research (OBPR) has initiated a strategic research thrust to augment the ongoing fundamental research in fluid physics and transport phenomena discipline with research especially aimed at understanding key multiphase flow related issues in propulsion, power, thermal control, and closed-loop advanced life support systems. A plan for integrated theoretical and experimental research that has the highest probability of providing data, predictive tools, and models needed by the systems developers to incorporate highly promising multiphase-based technologies is currently in preparation. This plan is being developed with inputs from scientific community, NASA mission planners and industry personnel. The fundamental research in multiphase flow and phase change in microgravity is aimed at developing better mechanistic understanding of pool boiling and ascertaining the effects of gravity on heat transfer and the critical heat flux. Space flight experiments conducted in space have shown that nucleate pool boiling can be sustained under certain conditions in the microgravity environment. New space flight experiments are being developed to provide more quantitative information on pool boiling in microgravity. Ground-based investigations are also being conducted to develop mechanistic models for flow and pool boiling. An overview of the research plan and roadmap for the strategic research in multiphase flow and phase change as well as research findings from the ongoing program will be presented.
Effect of Solids Loading, Reynolds Number, and Particle Size Distribution on Velocity Fluctuations in Gas-Particle Flows
Authors: Curtis Jennifer Sinclair
Published: February 2009

A variety of LDV experiments were conducted to assess the influence of solids loading, Reynolds number and particle size distribution on velocity fluctuations and flow behavior in gas-particle systems. This talk will summarize those experimental findings, as well as show comparisons of experimental results with multiphase CFD model predictions that utilize concepts from kinetic theory to describe particle velocity fluctuations. In order to probe solids loading effects, an axisymmetric particle-laden jet was investigated using LDV for 70 micron glass beads with solids loadings ranging from one to thirty. Dilute conditions are characterized by isotropic particle r.m.s. velocities and decreases in the magnitude of the r.m.s. velocities as the solids loading increases. Particle clustering is observed for dense conditions as well as anisotropy between axial and radial particle r.m.s. velocities. Under dense conditions, increases in the solids loading lead to increases in the axial particle r.m.s. velocity while the radial r.m.s. velocity remains at a constant level. Gas-solids flow models display good agreement between predictions and experimental measurements of mean velocities of the gas and solids as well as modulation of the gas turbulent kinetic energy by the presence of the particles. However, the gas-solid flow models based on kinetic theory concepts consistently overpredict the particle r.m.s. velocity for the range of solids loadings investigated. In addition, the same axisymmetric particle-laden jet consisting of 70-micron glass beads was investigated for a range of Reynolds numbers with a constant mass loading (m = 0.7). The presence of the solids dampens the gas turbulence intensity at the lowest value of Re investigated (8,300) compared with single-phase flow at the same Re. As the Reynolds number increases, the gas turbulence increases and for Re ≥ 15,200 the turbulence is enhanced compared with the single-phase flow at the same Re. The observed trend in turbulence modulation with Reynolds number is possibly due to the segregation of the solids and their effect on the gas mean velocity profiles. Finally, the particle-laden jet was investigated for binary mixtures of 25 and 70-micron glass beads. Specifically, the effect of a bimodal PSD on the modulation of gas-phase turbulence, the particle rms velocity, and particle segregation patterns was explored in detail. Measurements and model predictions indicate that increasing the mass fraction of the finer particles dampens the gas-phase turbulence. Changes in the random motion of the coarser particles are observed upon the addition of the finer material; clusters of fine particles arise for the largest solids loading investigated, and these clusters increase both the mean and fluctuating velocities of the coarse particles. The particles are also observed to segregate by size and volume fraction, with the coarse particles tending towards the center of the pipe.
Perforated Plate Pressure Losses With Improved Inlet and Outlet Flow Hole Features
Authors: Broach Kirkland D. , Conner Michael E. , Norrell Jeffery L. , Lunde Carter E.
Published: February 2009

This paper describes the tests and studies performed to better understand the geometric factors affecting pressure loss in a perforated plate. In this study, the impact of a specific perforated plate flow hole geometry on pressure drop was investigated. The methodology established in this paper to investigate this hole geometry can be extended to other components with orifice type perforated plates. To reduce the pressure drop of the perforated plate, various fundamental hole geometries, including edge chamfers and edge radii, were considered. Results from various edge treatments are provided in this study, including separate effects for inlet and outlet hole geometries. Specific trends, such as the effect of increasing edge geometries on the hydraulic losses, are presented. Additionally, a correlation between small-scale and full-scale pressure loss coefficients was found and is defined.
Calculation of Water That Flows in River in North District, Japan
Authors: Satoh Masashi , Sasaki Mikio , Takeuchi Takahiro
Published: February 2009

In this study, two models for snow and snowmelt were extended. Using those models, the calculation of water flowing in river was carried out. The results were compared with the observations. The outflow estimated by using the snow model in winter is in good agreement with the observations, and the snowmelt runoff predicted by using the snowmelt model in spring, April, May and June, is also at the good accuracy. The snowmelt runoff starts increasing from the early April, and it reaches the peak in the early May.
Dense Phase Flow Based on Multi-Scale Mechanics (Keynote)
Authors: Tsuji Yutaka
Published: February 2009

Numerical analysis of gas-particle flows is classified into micro, meso and macro scale approaches based on the concept of multi-scale mechanics. Further, cases are classified into collision-free flow, collision dominated flow and contact dominated flow.
Experimental Study of Turbulent Transport in Non-Isothermal Oscillating Grids Turbulence Using Particle Image Velocimetry
Authors: Eidelman Alexander , Elperin Tov , Kleeorin Nathan , Krein Alexander , Rogachevskii Igor , Buchholz Julia , Gru¨nefeld Gerd
Published: February 2009

An oscillating grids turbulence generator was constructed for studies of a new effect associated with turbulent transport of inertial particles — turbulent thermal diffusion. This phenomenon was predicted theoretically in Phys. Rev. Lett. 76, 224 (1996) and has been detected experimentally in oscillating grids turbulence with an imposed mean temperature gradient in air flow. This effect implies an additional mean flux of particles in the direction opposite to the mean temperature gradient and results in formation of large-scale inhomogeneities in the spatial distribution of particles. We used Particle Image Velocimetry to determine the turbulent velocity field and an Image Processing Technique to determine the spatial distribution of particles. Velocity distributions were measured in the flow generated with one and two grids in the Oscillating Grids Turbulence Generators at RWTH (Aachen) and BGU (Beer-Sheva). Analysis of the intensity of laser light Mie scattering by particles showed that they are accumulated in the vicinity of the minimum of the mean temperature of the surrounding fluid. The latter finding confirms the existence of the effect of turbulent thermal diffusion predicted theoretically.
Effect of Pressure Drop of Distributor on Flow Pattern in 2-D Fluidized Bed: DEM Simulation and Experiment
Authors: Kawaguchi Toshihiro , Mizushima Yunosuke , Tanaka Toshitsugu , Tsuji Yutaka
Published: February 2009

In the present study, effects of pressure drop across a distributor on particle motion in fluidized beds are studied numerically and empirically. The discrete element method (DEM) is employed to calculate the motion of individual particle. The predicted pressure drop across the distributor required to achieve uniform gas flows agreed well with previous empirical findings.
Modeling of Turbulence Modification Using Two-Time-Scale Dissipation Models and Accounting for the Particle Wake Effect
Authors: Yu Y. , Zhou L. X.
Published: February 2009

The presently developed two-phase turbulence models under-predict the gas turbulent fluctuation, because their turbulence modification models cannot totally reflect the effect of particles. In this paper, a two-time-scale dissipation model of turbulence modification, including a two-time-scale dissipation model for the two-phase velocity correlation and a two-time-scale dissipation model for the dissipation rate of gas turbulent kinetic energy, is proposed and used to simulate swirling gas-particle flows with a swirl number of 0.47. Besides, a gas turbulence augmentation model accounting for the finite-size particle wake effect in the gas Reynolds stress equation is proposed. The proposed turbulence modification models are used to simulate two-phase pipe flows. It can predict not only the turbulence reduction by small particles but also the turbulence enhancement by large particles.
Two Phase PIV Measurements at the Runner Outlet in a Francis Turbine
Authors: Iliescu Monica Sanda , Ciocan Gabriel Dan , Avellan Franc¸ois
Published: February 2009

Part load operation of hydro turbines with fixed pitch blades causes complex instable cavitation flow in the diffuser cone. Application of PIV systems provides the opportunity to investigate the flow velocity and turbulent fields in the case of development of cavitation vortex, the so-called turbine rope, at the outlet of a Francis turbine runner. The synchronization of the PIV flow survey with the rope precession allows to apply phase averaging techniques in order to extract both the periodic velocity components and the rope layout. The influence of the turbine setting level on the volume of the cavity rope and its center is investigated, providing a physical insight on the hydrodynamic complex phenomena involved in the development of the cavitation rope at Francis turbine operating regimes.
Modelling of Turbulent Transport in Laser Melt Pools
Authors: Chakraborty Nilanjan , Chakraborty Suman
Published: February 2009

In this paper, we present a modified k-ε model capable of addressing turbulent molten metal-pool convection in the presence of a continuously evolving phase-change interface during a laser melting process. The phase change aspects of the present problem are addressed using a modified enthalpy-porosity technique. The k-ε model is suitably modified to account for the morphology of the solid-liquid interface. A three-dimensional mathematical model is subsequently utilised to simulate a typical laser melting process with high power, where effects of turbulent transport can actually be realised. In order to investigate these effects on laser molten pool convection, simulations with laminar transport and turbulent transport are carried out for same problem parameters. Finally, results of the simulation using the present turbulence model are compared with the results of laminar simulation with same problem parameters. Significant effects of turbulent transport on penetration and the geometrical features of the molten pool are observed which is an outcome of the thermal history of the pool. The thermal history in turn determines the microstructure of the work piece, which finally governs the mechanical properties of the work piece.
Numerical Simulation of Flows in Electro-Chemical Machining for Compressor Blade
Authors: Kamijo Takuma , Toda Kazuyuki , Yamamoto Makoto , Enomoto Shunji , Mizuta Ikuhisa , Imanari Kuniyuki
Published: February 2009

Electro-Chemical Machining (ECM) is an advanced machining technology. It has been applied to highly specialized fields such as aerospace, aeronautics and medical industries. However, it still has some problems to be overcome. The efficient tool-design, electrolyte processing, and disposal of metal hydroxide sludge are the typical issues. To solve such problems, CFD is considered to be a powerful tool in the near future. However, the numerical method that can satisfactorily predict the flow has not been established because of the complex flow natures. In the present study, we develop a numerical code and simulate the three-dimensional flow in the ECM process of compressor blades. Visualizing the computed flow field, the characteristics of the flow between the tool and the blade are investigated. It is exhibited that the over-machining occurs due to the Joule’s heating and the flow deviation around the leading and trailing edges.
Rayleigh-Benard Convection With Second-Sound in a Viscoelastic Fluid-Filled High-Porosity Medium
Authors: Siddheshwar P. G. , Srikrishna C. V.
Published: February 2009

The linear stability of the Rayleigh-Benard situation in a viscoelastic fluid occupying a high-porosity medium is investigated. The viscoelastic correction to Brinkman momentum equation is effected by considering the modified form of Jeffrey constitutive equation. Further, the non-classical Maxwell-Cattaneo heat flux has been used in place of the classical Fourier heat flux law. The results of the study reveal that the non-classical theory predicts finite speeds of heat propagation. The eigen value is obtained for free-free, isothermal boundary combinations and it has been observed that the critical Rayleigh number is less than the corresponding value of the problem governed by the classical Fourier law. The study finds application in progressive solidification of polymeric melts and solutions, and also in the manufacture of composite materials.
A Flight Simulation Vision for Aeropropulsion Altitude Ground Test Facilities
Authors: Davis Milt , Montgomery Peter
Published: February 2009

Testing of a gas turbine engine for aircraft propulsion applications may be conducted in the actual aircraft or in a ground-test environment. Ground test facilities simulate flight conditions by providing airflow at pressures and temperatures experienced during flight. Flight-testing of the full aircraft system provides the best means of obtaining the exact environment that the propulsion system must operate in but must deal with limitations in the amount and type of instrumentation that can be put on-board the aircraft. Due to this limitation, engine performance may not be fully characterized. On the other hand, ground-test simulation provides the ability to enhance the instrumentation set such that engine performance can be fully quantified. However, the current ground-test methodology only simulates the flight environment thus placing limitations on obtaining system performance in the real environment. Generally, a combination of ground and flight tests is necessary to quantify the propulsion system performance over the entire envelop of aircraft operation. To alleviate some of the dependence on flight-testing to obtain engine performance during maneuvers or transients that are not currently done during ground testing, a planned enhancement to ground-test facilities was investigated and reported in this paper that will allow certain categories of flight maneuvers to be conducted. Ground-test facility performance is simulated via a numerical model that duplicates the current facility capabilities and with proper modifications represents planned improvements that allow certain aircraft maneuvers. The vision presented in this paper includes using an aircraft simulator that uses pilot inputs to maneuver the aircraft engine. The aircraft simulator then drives the facility to provide the correct engine environmental conditions represented by the flight maneuver.
Nonlinear Gas Turbine Modeling Using Feedforward Neural Networks
Authors: Chiras Neophytos , Evans Ceri , Rees David
Published: February 2009

In this paper a feedforward neural network is used to model the fuel flow to shaft speed relationship of a Spey gas turbine engine. The performance of the estimated model is validated against a range of small and large signal engine tests. It is shown that the performance of the estimated models is superior to that of the estimated linear models.
Application of Dynamic Simulation to CAES G/T Control System Development
Authors: Takahashi Katsuyuki , Yasuda Tomoshige , Endoh Makoto , Kurosaki Masahiro
Published: February 2009

This paper presents extensive use of dynamic simulation of Compressed Air Energy Storage Gas Turbine (CAES G/T) for control system design, control logic development and software validation which significantly reduced development time and cost of the control system and contributed to successful demonstration of a 2,000 kW pilot plant with technical risk mitigation. The CAES G/T is one of the electrical load leveling power plants. High-pressure air compressed by motor-driven compressors in nighttime and stored in underground reservoir is provided to the CAES G/T for power generation in day time. Based on extensive simulation, we finalized control system configuration and control component specification. Developed control logic was tested by comprehensive simulation tests covering almost all expected operations such as start, acceleration, load application and rejection, recuperator active/non-active mode transfer etc. Finally, we conducted hardware in the loop simulation test to assure Electronic Control Unit (ECU) function and performance. An actual ECU and a real time simulator with the CAES G/T model, sensor models and actuator models were used in this test. Tests at a 2,000 kW pilot plant started in January 2001. The full load rejection test showed 9.9% overspeed of the rotor, which is 1% less than the simulation predicted value and within the regulation limit. Only minor control parameter and logic adjustments were required during the tests. Regular operation of the plant started in June 2001.
Observations of Flame Behavior in a Laboratory-Scale Pre-Mixed Natural Gas/Air Gas Turbine Combustor From CARS Temperature Measurements
Authors: Hedman Paul O. , Flores Daniel V. , Fletcher Thomas H.
Published: February 2009

This objective of this study was to obtain instantaneous gas temperature measurements using a coherent anti-Stokes Raman spectrometer (CARS) in a laboratory-scale, gas-turbine combustor (LSGTC) with a pre-mixed, swirl-stabilized, natural gas flame. These measurements complement PLIF measurements of OH radical, and LDA measurements of velocity which are presented in companion papers [1,2]. Gas temperature measurements were obtained at each of four operating conditions (high swirl and medium swirl at fuel equivalence ratios of 0.80 and 0.65). Results of mean and standard deviation measurements are included in this paper for all four test cases. Additionally, example probably density functions (PDF) for the gas temperature at the 40 mm, 60 mm, and 80 mm axial locations are presented for the for the high swirl (HS) φ = 0.80 case (most stable flame) and the medium swirl (MS) φ = 0.65 case (least stable flame).
Integral Textile Ceramic Composites for Turbine Engine Combustors
Authors: Cox B. N. , Davis J. B. , Marshall D. B. , Yang Q. D.
Published: February 2009

Integrally formed ceramic matrix composite structures are being developed for a range of hot-structure applications involving active cooling. In this paper, some advantages of integral textile approaches are summarised and design possibilities for turbine engine combustors are suggested. Advantages of integral textile structures include: 1) joints between ceramic and other materials in hot zones can be avoided; 2) thin skins (< 1 mm) can be formed that are strong and tough, enabling tolerance of higher heat fluxes; 3) compliant structures can be designed, which can limit the development of thermal mismatch stresses; and 4) fabrication costs can be lowered by reducing part counts and steps in processing. This paper discusses some of the non-traditional design and fabrication challenges that must be met to exploit integral textile ceramic structures and offers a preliminary assessment of their viability for handling the thermomechanical loads of an advanced combustor.
Investigation of the Response of an Air Blast Atomiser Combustion Chamber Configuration on Forced Modulation of Air Feed at Realistic Operating Conditions
Authors: Hassa Christoph , Heinze Johannes , Stursberg Klaus
Published: February 2009

DLR investigated forced combustion oscillations of two liquid fuel burners in a research combustion chamber at elevated pressures simulating idle conditions of aircraft engine combustors. The work was performed in collaboration with MTU Munich. An existing combustion chamber with optical access, capable to operate up to 20 bar, was upgraded with an air flow pulsator, that bypasses air from the combustor plenum to the exhaust with a sinusoidal massflow variation up to 700 Hz. Pressure transducers in the plenum and the flame tube monitored the forced disturbances. A photomultiplier recorded the OH* chemiluminescence of the flame. For the agreed operating conditions frequency scans of these values were registered. Additionally images of the OH* chemiluminescence were taken at selected frequencies and evaluated in a statistical manner, to separate turbulent and periodic behaviour. From the analysis of the pressure data, it can be concluded, that serious thermo-acoustic feedback was not observed for both burners. However burner 2 with the flame detached from the wall exhibited a higher fluctuation level as burner 1 with the wall attached flame. A resonant behaviour was observed near the characteristic frequency of the sound room comprised of plenum, flame tube and burner nozzle as connecting passage. The chemiluminescence images show different modes of spatial fluctuation for the burners and for burner 2 they also vary with the operating condition.
Dynamic Analysis of Swirl Stabilized Turbulent Gaseous Flames
Authors: Khanna Vivek K. , Vandsburger Uri , Saunders William R. , Baumann William T.
Published: February 2009

With the advent of lean premixed gas turbine combustors, research in the area of thermo-acoustic instabilities and active combustion control came into the limelight. To be able to predict and control these instabilities, it is required that both the acoustics of the system, and a frequency-resolved response of the combustion process to velocity perturbations be understood. Experimental techniques developed by the Virginia Active Combustion Control Group at Virginia Tech, to obtain an open loop flame transfer function were applied to both fully and partially premixed swirl stabilized turbulent gaseous flames using commercial grade methane as fuel. A frequency-resolved fluctuating velocity was applied at the inlet of the combustor within the frequency range of 20–400 Hz, and the OH* chemiluminescence was used as a measure of the fluctuating heat release rate within the flame. Experiments were conducted at atmospheric pressure for two swirl numbers of 0.79 and 1.19, and three equivalence ratios of 0.55, 0.60 and 0.65. The flow rates studied resulted in Reynolds numbers of 14,866 and 19,821. The results show that for the linear range, the magnitude of the FRF is primarily dependent on the premixing quality and the mean energy content of the mixture, while the phase of the FRF is quite sensitive to Φ′ oscillations and to the variations in the species concentration across the cross-section of the flow.
Turbine Durability Impacts of High Fuel-Air Ratio Combustors: Part 1 — Potential for Intra-Turbine Oxidation of Partially Reacted Fuel
Authors: Lukachko Stephen P. , Kirk Daniel R. , Waitz Ian A.
Published: February 2009

Demand for greater engine efficiency and thrust-to-weight ratio has driven the production of aircraft engines with higher core temperatures and pressures. Such engines operate at higher fuel–air ratios, resulting in the potential for significant heat release through the turbine if energetic species emitted from the combustor are further oxidized. This paper outlines the magnitude and potential for turbine heat release for current and future engines. The analysis indicates that in the future, high fuel-air ratio designs may have to consider changes to cooling strategies to accommodate turbine heat release. A characteristic time methodology is developed to evaluate the chemical and fluid mechanical conditions that lead to combustion within the turbine. The local concentration of energetic emissions partly determines the potential for energy release. An energy release parameter, here defined as a maximum increase in total temperature (ΔTt), is used to specify an upper limit on the magnitude of impact. The likelihood of such impacts relies on the convective, mixing, and chemical processes that determine the fate and transport of energetic species through the turbine. Appropriately defined Damko¨hler numbers (Da)—the comparative ratio of a characteristic flow time (τflow) to a characteristic chemical time (τchem)—are employed to capture the macroscopic physical features controlling the flow-chemistry interactions that lead to heat release in the turbine.
Internal Traversing of Combustion Species Inside a Methane Fuelled DLE Combustor
Authors: Brundish K. D. , Miller M. N. , Wilson C. W. , Macquisten M. , Moran J.
Published: February 2009

This paper describes a test programme undertaken by Rolls-Royce plc and QinetiQ Ltd. where a series staged Dry Low Emissions (DLE) combustor was internally traversed in 3 dimensions. The primary motivation of the exercise was to generate gaseous composition data for Combustion CFD validation and to gain greater insight into the changes in the detail of chemical composition along the length of the combustor. The combustor was run at baseload conditions corrected for 10 bar. An RB211 DLE combustion system was modified so that it could be installed into the QinetiQ internal traversing facility. Within this facility a position-calibrated gas-sampling probe was traversed within the combustor. Measurements of gaseous concentrations were made of CO, CO2, NOx, NO2, HC and O2 for over 400 points in 6 axial planes in both primary and secondary zones. Data within this paper, however, is reported for the four axial locations of most interest. The combustion temperature, AFR and efficiency were calculated from the gas analysis. A selected summary of the traverse results in terms of the gaseous compositions (NO and NOx), efficiency and AFR is included. Combustor performance in terms of efficiency, mixing and emissions has also been evaluated. The results show that although the combustion contains a great deal of structure at the inlets to both the primary and secondary zones, efficiency is close to 100% by the exit of each zone. Peak NOx emissions identified in the primary zone reached acceptable values by the combustor exit plane. Although a large number of points were measured, recommendations include further work with different operating conditions and better coverage of each axial plane.
Low NOx Emission Technology for the Vx4.3A Gas Turbine Series in Fuel Oil Operation
Authors: Meisl Juergen , Lauer Gerald , Hoffmann Stefan
Published: February 2009

This contribution describes the systematic refinement of the hybrid burner used in Siemens Vx4.3A gas turbines for lean premix combustion of various liquid fuels such as Distillate fuel No. 2, Naphtha and Condensate. Additionally to the dry premix operation fuel/water emulsions are used in premix mode for a further reduction of NOx emissions or power augmentation. NOx emissions of less than 72 ppm are already achieved with the HR3 hybrid burner in dry premix mode. These can be reduced to values below of 42 ppm NOx in emulsion mode.
Performance Evaluation of Gas Turbine-Fuel Cell Hybrid Micro Generation System
Authors: Kimijima Shinji , Kasagi Nobuhide
Published: February 2009

Design-point and part-load characteristics of a gas turbine-solid oxide fuel cell hybrid micro generation system, of which total power output is 30 kW, are investigated for its prospective use in the small distributed energy systems. A cycle analysis of the hybrid system has been performed to obtain general strategies of highly efficient operation and control. The method of analysis has been compared with previous results, of which power output values are set in the range from 287 to 519 kW. Then, the part-load performance of the 30 kW system has been evaluated. Two typical operation modes, i.e., constant and variable rotation speed gas turbine operation are considered. It is found that the variable speed mode is more advantageous to avoid performance degradation under part-load conditions. Operating under this mode, despite of 10% adiabatic efficiency drop in the gas turbine components, the generation efficiency can be maintained over 60% (LHV) in the power output range from 50 to 100%.
Molten Carbonate Fuel Cell Gas Turbine Combined Cycle for Marine Propulsion: Part B — Part Load Operation
Authors: Basurto Maria-Teresa , Pilidis Pericles , Hales Richard
Published: February 2009

Molten Carbonate Fuel Cell/Gas Turbine (MCFC/GT) hybrid power systems represent a modern, efficient and clean alternative to the currently used marine propulsion systems. The objective of this paper is to present the results found from the application of MCFC/GT hybrid power systems to marine propulsion, and in particular to present the results of the off-design performance of a COGAFC system (Combined Gas Turbine and Fuel Cell System). The results presented are subjected to the current uncertainties on MCFC power systems derived from its early stage of development. It is, then, the interest of the authors to summarise the results of the research work done, providing to the lectors the understanding and a general view of which are the concerns, the benefits, and which should be the next steps on the implementation of these systems. The study is summarised into two papers: “Molten Carbonate Fuel Cell Gas Turbine Combined Cycle for Marine Propulsion. Part A: Design Point Operation” (Basurto et al., 2002), that describes the selection of the design point, and “Molten Carbonate Fuel Cell Gas Turbine Combined Cycle for Marine Propulsion. Part B: Part Load Operation”, that describes the off-design performance of the system. The study is based on previous work published by the authors on the integration of MCFCs with gas turbines (Basurto et al., 2001).
Thermoeconomic Analysis of a Gas Turbine Plant With Fuel Decarbonization and Carbon Dioxide Sequestration
Authors: Bozzolo M. , Brandani M. , Traverso A. , Massardo A. F.
Published: February 2009

In this paper the thermoeconomic analysis of gas turbine plants with fuel decarbonisation and carbon dioxide sequestration is presented. The study focuses on the amine (MEA) decarbonisation plant lay-out and design, also providing economic data about the total capital investment costs of the plant. The system is fuelled with methane that is chemically treated through a partial oxidation and a water-gas shift reactor. CO2 is captured from the resulting gas mixture, using an absorbing solution of water and MEA that is continuously re-circulated through an absorption tower and a regeneration tower: the decarbonised fuel gas is afterwards burned in the gas turbine. The heat required by CO2 sequestration is mainly recovered from the gas turbine exhausts and partially from the fuel treatment section. The reduction in efficiency and the increase in energy production costs due to fuel amine decarbonisation is evaluated and discussed for different gas turbine sizes and technologies (microturbine, small size regenerated, aeroderivative, heavy duty). The necessary level of carbon tax for a conventional plant without a fuel decarbonisation section is calculated and a comparison with the Carbon Exergy Tax procedure is carried out, showing the good agreement of the results.
A Fifty Percent Plus Efficiency Mid Range Advanced Cheng Cycle
Authors: Nelson Albert L. C. , Vaezi Vahid , Cheng Dah Yu
Published: February 2009

Cheng Power Systems, Inc. following the successful Cheng Cycle development based on the Allison 501KH, is developing a 50%+ efficiency medium-power-range Advanced Cheng Cycle. The recent development work involved the selection of a candidate gas turbine which possesses the following attributes: (1) a single shaft, (2) advanced compressor and turbine aerodynamic design, and (3) F-Class firing temperature. The targeted results were a 30MW+ output and 50%+ efficient intermediate-load Advanced Cheng Cycle with the simple-cycle performance characteristics of quick startup and shutdown and a $/kW cost comparable to simple-cycle machines, but at a combined-cycle efficiency. A candidate engine was selected which has the following performance characteristics: a compressor pressure ratio of 18:1, a turbine inlet temperature of 1250°C, and a net efficiency of 35%. Cheng Power has a unique software program which predicts the energy balance at various ambient conditions. The program takes into account the massive cooling air flows incorporated into advanced gas turbines and the heat recovery boiler performance characteristics when developing our performance analyses. The uniqueness of the Cheng Cycle is that it selects a trajectory of steam-to-air ratios to maintain high efficiency for the entire operating range of the power system, while offering competitive efficiency, simple hardware, the possibility of retrofit, fast response to load change, and feasible cogeneration plant operations. The quick startup of the Advanced Cheng Cycle is suitable for variable load operation in the mid range, i.e. 8 to 10 hours per day. This paper provides the energy balance of the proposed plant and its variation with ambient temperature. The paper also addresses the emission characteristics of this engine, which provides low NOx and CO emissions at levels that satisfy most U.S. EPA requirements without SCR or any other add-on devices.
A New Generalised Carbon Exergy Tax: An Effective Rule to Control Global Warming
Authors: Traverso A. , Santarelli M. , Massardo A. F. , Cali` M.
Published: February 2009

An instrument for promoting CO2 emission reductions, taking the Kyoto Protocol goal into account, could be the assignment to energy conversion plants of a monetary charge linked to their specific emission intensity, usually called Carbon Tax. There are two main problems closely connected with this approach: the estimation of the charge (that must be related to the “external” cost associated with CO2 emission) and the choice of the strategy to determine the amount of the imposed charge. In this paper an analytical procedure proposed by the authors and called Carbon Exergy Tax (CET) for the evaluation of CO2 emission externalities is presented. It is based on the thermoeconomic analysis of energy systems, which allows Second Law losses to be quantified in monetary terms: the resulting cost represents the taxation that is to be applied to the energy system under examination, calculated without any arbitrary assumption. Since the complete procedure of the CET evaluation is too complex to become a feasible instrument of energy policy, hereby, after applying the procedure to some conventional and advanced power plants, gas-, oil- and coal-fuelled, a new generalised approach, based on the results of the complete CET procedure, is proposed. The generalised CET evaluation requires much less information about the energy system and thus a simple and effective energy policy rule to manage global warming is obtained and available.
Simulation Investigation of Control Options for Full Load Rejection in the PBMR Closed Cycle Gas Turbine Power Plant
Authors: Botha Barend W. , Rousseau Pieter G.
Published: February 2009

The Pebble Bed Modular Reactor (PBMR) power station concept is currently being developed in South Africa by ESKOM and its partners. This high temperature gas cooled reactor is based on the three-shaft recuperative inter-cooled closed loop Brayton cycle. Detailed cycle analysis was performed with the Flownet thermo-hydraulic network simulation software developed at the Engineering Faculty of Potchefstroom University in South Africa. Using Flownet simulations is especially useful for component design and integration. It furthermore enables the study of complex load following and load rejection scenarios and the design of suitable controller algorithms. One of the most severe load control scenarios is that of full load rejection due to the loss of the grid power. This paper discusses the two control concepts that showed the most promising results for full load rejection.
Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements: Part I — Showerhead Effects
Authors: Cutbirth J. Michael , Bogard David G.
Published: February 2009

The goal of this study was to determine how showerhead blowing on a turbine vane leading edge affects of the performance of film cooling jets farther downstream. An emphasis was placed on measurements above the surface, i.e. flow visualization, thermal field, and velocity field measurements. The film cooling performance on the pressure side of a simulated turbine vane, with and without showerhead blowing, was examined. Results presented in this paper are for low mainstream turbulence; high mainstream turbulence effects are presented in the companion paper. At the location of the pressure side row of holes, the showerhead coolant extended a distance of about 3d from the surface (d is the coolant hole diameter). The pressure side was found to be subjected to high turbulence levels caused by the showerhead injection. Results indicate a greater dispersion of the pressure side coolant jets with showerhead flow due to the elevated turbulence levels.
Flow Visualisation of a Converging Slot-Hole Film-Cooling Geometry
Authors: Sargison J. E. , Guo S. M. , Oldfield M. L. G. , Lock G. D. , Rawlinson A. J.
Published: February 2009

This paper presents the first flow visualisation for the previously published novel film cooling hole, the converging slot-hole or console. Published experimental results [4,5] have demonstrated that the console improved both the heat transfer and aerodynamic performance of turbine vane and rotor blade cooling systems. Flow visualisation data for a row of consoles was compared with that of cylindrical and fan-shaped holes and a slot at the same inclination angle of 35° to the surface, on a large-scale, flat-plate model at engine representative Reynolds numbers in a low speed tunnel with ambient temperature mainstream flow. The data were collected using a fine nylon mesh covered with thermochromic liquid crystals, which allowed measurement of gas temperature in planes perpendicular to the flow. The data demonstrated that the console film was similar to a slot film, and remained thin and attached to the surface for coolant to mainstream momentum flux ratios of 1.1 to 40 and for a case with no crossflow (infinite momentum flux ratio).
Heat Flux Reduction From Film Cooling and Correlation of Heat Transfer Coefficients From Thermographic Measurements at Engine Like Conditions
Authors: Baldauf S. , Scheurlen M. , Schulz A. , Wittig S.
Published: February 2009

Heat transfer coefficients and the resulting heat flux reduction due to film cooling on a flat plate downstream a row of cylindrical holes are investigated. Highly resolved two dimensional heat transfer coefficient distributions were measured by means of infrared thermography and carefully corrected for local internal testplate conduction and radiation effects [1]. These locally acquired data are processed to lateral average heat transfer coefficients for a quantitative assessment. A wide range variation of the flow parameters blowing rate and density ratio as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The effects of these dominating parameters on the heat transfer augmentation from film cooling are discussed and interpreted with the help of highly resolved surface results of effectiveness and heat transfer coefficients presented earlier [2]. A new method of evaluating the heat flux reduction from film cooling is presented. From a combination of the lateral average of both the adiabatic effectiveness and the heat transfer coefficient, the lateral average heat flux reduction is processed according to the new method. The discussion of the total effect of film cooling by means of the heat flux reduction reveals important characteristics and constraints of discrete hole ejection. The complete heat transfer data of all measurements are used as basis for a new correlation of lateral average heat transfer coefficients. This correlation combines the effects of all the dominating parameters. It yields a prediction of the heat transfer coefficient from the ejection position to far downstream, including effects of extreme blowing angles and hole spacing. The new correlation has a modular structure to allow for future inclusion of additional parameters. Together with the correlation of the adiabatic effectiveness it provides an immediate determination of the streamwise heat flux reduction distribution of cylindrical hole film cooling configurations.