bluuebunny/crossref_metadata_2025 huggingface dataset:
Impacts of the Heating Value and CO/H2 Ratio on Syngas Diffusion Flame Structure
Authors: Feng Chong , Qi Haiying , Zhu Junzong , Bi Dapeng
Published: July 2013

Syngas with CO/H2/N2 as the primary ingredients is the main fuel for the gas turbine in the IGCC system, but changes of the heating value and CO/H2 ratio frequently cause great impacts on the normal operation of the combustor, which is a challenge to the design of the syngas combustor. In this paper based on the Sandia/ETH-Zurich CO/H2/N2. Flame A, numerical simulations and predictions of the impacts of these two factors on the flame structure and diffusion combustion characteristics are carried out, and the main results are as follows. The heating value and CO/H2 ratio both have important impacts on the diffusion combustion characteristics. Most of the impacts have regularity such as changes of the axis velocity and temperature distribution, the highest temperature of the whole temperature field, the combustion efficiency and the NO formation with the heating value and CO/H2 ratio. However, the most important one is that the relationship between the flame size and the Wobbe Index is linear, for it has established connections between the structure size of the combustor and the characteristics of the fuel and the linear relationship can be used to provide reference for the combustor design. So the Wobbe Index is not only an important parameter to judge whether different fuels can be exchanged or not under the same initial pressure and heat load of a combustion equipment, but also an important parameter for syngas combustor design.
Large Eddy Simulations of Hydrogen Oxidation at Ultra-Wet Conditions in a Model Gas Turbine Combustor Applying Detailed Chemistry
Authors: Krüger Oliver , Terhaar Steffen , Paschereit Christian Oliver , Duwig Christophe
Published: July 2013

Humidified Gas Turbines (HGT) offer the attractive possibility of increasing the plant efficiency without the cost of an additional steam turbine, as is the case for a combined gas-steam cycle. In addition to efficiency gains, adding steam into the combustion process reduces NOx emissions. It increases the specific heat capacity (hence, lowers possible temperature peaks) and reduces the oxygen concentration. Despite the thermo-physical effects, steam alters the kinetics, and thus, reduces NOx formation significantly. In addition, it allows operation using a variety of fuels, including hydrogen and hydrogen-rich fuels. Therefore, ultra-wet gas turbine operation is an attractive solution for industrial applications. The major modification compared to current gas turbines lies in the design of the combustion chamber, which should accommodate a large amount of steam without losing in stability. In the current study, the premixed combustion of pure hydrogen diluted with different steam levels is investigated. The effect of steam on the combustion process is addressed using detailed chemistry. In order to identify an adequate oxidation mechanism, several candidates are identified and compared. The respective performances are assessed based on laminar premixed flame calculations under dry and wet conditions, for which experimentally determined flame speeds are available. Further insight is gained by observing the effect of steam on the flame structure, in particular HO2 and OH* profiles. Moreover, the mechanism is used for the simulation of a turbulent flame in a generic swirl burner fed with hydrogen and humidified air. Large Eddy Simulations (LES) are employed. It is shown that by adding steam, the heat release peak spreads. At high steam content, the flame front is thicker and the flame extends further downstream. The dynamics of the oxidation layer under dry and wet conditions is captured, thus, an accurate prediction of the velocity field, flame shape and position is achieved. The latter is compared with experimental data (PIV and OH* chemiluminescence). The reacting simulations were conducted under atmospheric conditions. The steam-air ratio was varied from 0% to 50%.
Modelling Flame-Generated Noise in a Partially Premixed, Bluff Body Stabilized Model Combustor
Authors: Tufano Saverio , Stopford Phil , Roman Casado J. C. , Kok J. B. W.
Published: July 2013

Numerical simulation using Computational Fluid Dynamics (CFD) has become increasingly important as a tool to predict the potential occurrence of combustion instabilities in gas turbine combustors operating in lean premixed mode. Within the EU-funded Marie Curie project, LIMOUSINE (Limit cycles of thermo-acoustic oscillations in gas turbine combustors), a model test burner has been built in order to have reproducible experimental results for model validation. The burner consists of a Rijke tube of rectangular section having a flame-stabilizing wedge at about 1/4 of its length. Fuel and air supplies were carefully designed to give closed end acoustic inlet boundary conditions while the atmospheric outlet representing an acoustically open end. A transient CFD simulation of the turbulent, partially premixed, bluff body stabilized combusting flow has been carried out for the LIMOUSINE burner using ANSYS CFX commercial software. A 2-D section has been modelled by means of the scale resolving turbulence model, Scale-Adaptive Simulation (SAS), and a two-step Eddy Dissipation combustion model.

Experiments were performed on the LIMOUSINE model burner to measure the dynamic variation of pressure and temperature. Results were obtained for several cases with power input ranging from 40 to 60 kW and air factors between 1.2 and 1.8.

The CFD results are found to be in good agreement with experiments: the flame is predicted to stabilise on the bluff body in the fluid recirculation zone; resonance frequencies are found to change depending on power and air excess ratio and have a good agreement with experimental results and analytical values; pressure oscillations are consistent with pipe acoustic modes.
Modeling CO With Flamelet-Generated Manifolds: Part 2 — Application
Authors: Goldin Graham , Ren Zhuyin , Forkel Hendrik , Lu Liuyan , Tangirala Venkat , Karim Hasan
Published: July 2013

Conventional Flamelet Generated Manifold (FGM) closure of the mean progress variable reaction rate assumes PDF shapes to account for turbulent fluctuations. The FGM parameters are commonly assumed to be statistically independent, and the marginal PDFs invariably require second moments, which are difficult to model accurately and have limited coefficients that can be adjusted to calibrate the simulation. A new model is presented which locates the flame brush with a turbulent flame speed model, and applies the FGM kinetic rate to model kinetically limited processes, such as CO quenching, behind the flame-front. The model is applied to 3D RANS simulations of an equivalence ratio sweep in the GE Entitlement Rig perfectly premixed combustor experiment. Calculating the mean FGM reaction progress source term with standard assumed shape PDFs leads to a narrow flame brush and equilibrium CO outlet emissions. By limiting the mean FGM reaction progress source term by the turbulent flame speed model, the flame brush is broadened and super-equilibrium CO is predicted at the outlet. Good agreement with measurement is obtained with default model coefficients. Since the majority of the mean reaction progress source term is limited by the turbulent flame speed reaction rate, it is demonstrated that the model is relatively insensitive to assumed shape PDFs for the FGM rate, as well as the parameter used to determine the turbulent flame leading edge.
Characterizing Particulate Matter Emissions From Aircraft Engines
Authors: Bhargava Anuj , Liscinsky David , McKinney Randal , Anderson Bruce , Petzold Andreas , Miake-Lye Richard C.
Published: July 2013

Research in the areas of particulate matter (PM) emissions impacts on both climate and human health are currently very active, however there are a large number of variables and response times. As a better understanding of the contribution of aviation PM emissions is developed, new aircraft engines will need to be designed for reduced PM emissions. In order to do this, measurement methods for different PM metrics like mass, number, size distribution, volatile precursors and composition need to be developed followed by measurements for existing engines to assess their environmental impact. Relevant literature will be reviewed to show that it is necessary to control emissions of nanometer-size particles from a total “number count” as well as a “mass” perspective. Several activities to develop a measurement method and evaluate its effectiveness will be discussed. The results are being used to develop standard measurement methods for aircraft PM emissions which will allow the design of lower emission combustors.
Investigation of Precessing-Vortex-Core–Flame Interaction Based on Tomographic Reconstruction Techniques
Authors: Moeck Jonas P. , Bourgouin Jean-Francois , Durox Daniel , Schuller Thierry , Candel Sébastien
Published: July 2013

Unsteady helical flow structures, such as the precessing vortex core (PVC), are often observed in swirling flows with vortex breakdown. Although this type of flow is of high relevance for industrial combustors, the role of these flow instabilities in reacting systems, in particular their effect on flame stabilization and combustion instabilities, remains poorly understood. The three-dimensional structure of the interaction between the helical mode and the flame is difficult to assess with common measurement techniques, such as chemiluminescence imaging, due to the non-axisymmetry of the oscillation pattern. In the present work, a novel method is proposed to determine the full field of the heat release rate perturbation associated with the helical mode. This method requires only line-of-sight integrated information from a single camera. Tomographic reconstruction techniques are used, exploiting the fact that the helical mode is a rotating structure. Reconstruction algorithms are presented that are tailored to the specific spatio-temporal structure of the oscillation pattern, and it is shown that these techniques outperform standard methods. The proposed methodology is applied in a turbulent swirl-stabilized model combustor with significant PVC oscillations. Images from an intensified high-speed camera are used for the reconstruction. The analysis shows that the helical mode perturbs the flame in the inner and the outer shear layers of the annular jet and thereby creates helical traveling waves. The perturbation in the outer shear layer grows significantly in downstream direction and causes strong heat release rate fluctuations when impinging on the combustor wall.
Investigation of a Flame Anchored in Crossflow Stream of Vitiated Air at Elevated Pressures
Authors: Galeazzo Flavio Cesar Cunha , Prathap Chockalingam , Kern Matthias , Habisreuther Peter , Zarzalis Nikolaos , Beck Christian , Krebs Werner , Wegner Bernhard
Published: July 2013

The objective was to study the effect of equivalence ratio of secondary stage combustible mixture injected into the cross flow stream of vitiated air in a two staged combustion system on the characteristics of the secondary stage combustion zone. The primary cylindrical combustor equipped with low swirl air blast nozzle operating with kerosene generates vitiated air. A methane injector was flush mounted to the inner surface of the secondary combustor. It was used to inject the premixed methane-air mixtures perpendicular into the crossflow of vitiated air. An optical, double shell, secondary combustor with three optical windows on its outer shell was used to image the secondary stage flames. The inner shell was a quadratic fused quartz tube which acts as a thermal barrier and the outer thick quartz windows mounted in the quadratic stainless steel chamber withholds the pressure. Chemiluminescence imaging technique equipped with ICCD camera was used to image the OH* emissions of the secondary stage flame.

The vitiated air was generated at 2 bar and 1700 K. The velocity of the vitiated air in the secondary combustor was 57 m/s. A premixed methane air mixture was injected into the cross flow stream of vitiated air. The momentum flux ratio between the jet and the vitiated air was maintained at 1.4. The equivalence ratio of the premixed methane-air mixture was varied from 0.5 to 1.0. As the equivalence ratio of the secondary stage combustible mixture moves towards stoichiometric condition, the secondary stage combustion zone becomes compact and also the distance between the burner and the combustion zone decreases.

The turbulent flame stabilized in the secondary combustor exhibited large scale structures and other unsteady phenomena that require time-resolved computational methods. Large eddy simulations (LES) are well suited to the calculation of such complex flows. The flame was embedded in a strong turbulent flow where auto-ignition and quenching are important, which poses a significant challenge for the reaction modeling. The presumed JPDF turbulent reaction model, which has been proven to be a reliable model for these challenging conditions, was successfully coupled with the LES simulation. The qualitative agreement between the results of simulations and measurements was quite satisfactory.
Swirler Effects on Passive Control of Combustion Noise and Instability in a Swirl-Stabilzed Combustor
Authors: Borsuk Alex , Williams Justin , Meadows Joseph , Agrawal Ajay K.
Published: July 2013

High strength porous inert media (PIM) placed in the reaction zone of a swirl-stabilized lean-premixed combustor is a passive method of controlling combustion noise and instabilities. In this study, the effect of swirler location and swirl number on combustion without and with PIM has been investigated experimentally, using a methane-fueled quartz combustor at atmospheric pressure. Three axial swirlers were designed with 8 vanes, a solid centerbody, and vane angles of 30, 45, and 55 degrees to yield calculated swirl numbers of 0.45, 0.78, and 1.10, respectively. Swirler location was varied to obtain recess depth in the premixer tube of 0.0 cm, 2.5 cm, and 5.0 cm. A downstream bluff body was used with the recessed swirlers to stabilize the flame at the dump plane. Experiments were conducted at constant air flow rate of 300 SLPM and equivalence ratios of 0.70, 0.75, and 0.80. PIM annular rings with increasing and decreasing cross-sectional area in the flow direction were tested, referred to as diverging and converging PIM. The performance of each test case is compared by observing the flame behavior and measuring sound pressure level (SPL) with a microphone probe. Results include total SPL and SPL in one-third octave bands. PIM proved effective in mitigating combustion noise and instability for all flush-mounted swirlers with total SPL reductions of up to 7.6 dBA. The effectiveness of the PIM generally improved with increasing equivalence ratio. Combustion instability that occurred within the frequency band centered about 630 Hz was suppressed with both PIM configurations. These results confirm that PIM is an effective method to control combustion noise and instabilities in swirl-stabilized LPM combustion.
Effects of Outlet Boundary Conditions on the Reacting Flow Field in a Swirl-Stabilized Burner at Dry and Humid Conditions
Authors: Terhaar Steffen , Bobusch Bernhard C. , Paschereit Christian Oliver
Published: July 2013

During the design and testing process of swirl-stabilized combustors, it is often impractical to maintain identical outlet boundary conditions. Furthermore, it is a common practice to intentionally change the acoustic boundary conditions of the outlet in order to suppress thermoacoustic instabilities. In the presented work the susceptibility of the reacting flow field to down-stream perturbations is assessed by the application of an area contraction at the outlet. Since combustion and fuel composition are shown to be important parameters for the influence of the boundary conditions on the flow field, highly steam diluted flames are investigated in addition to dry flames, at different equivalence ratios and degrees of swirl. The applied measurement techniques include Particle Image Velocimetry, Laser Doppler Velocimetry, and emission analysis. The results reveal a clear correlation of the susceptibility of the flow field to downstream perturbations to both, the inlet swirl number and the amount of dilatation caused by the flame. The concept of an effective swirl number down-stream of the flame is applied to the results and is proven to be the dominating parameter. A theoretical explanation for the influence of this parameter is provided by the usage of the well known theory of subcritical and supercritical swirling flows, where perturbations can propagate upstream solely in subcritical flows via standing waves. Knowledge of the flow state is of particular importance for the evaluation of combustion tests with differing exit boundary conditions and the results emphasize the need for realistic exit boundary conditions for numerical simulations.
Amplitude-Dependent Flow Field and Flame Response to Axial and Tangential Velocity Fluctuations
Authors: Schimek Sebastian , Ćosić Bernhard , Moeck Jonas P. , Terhaar Steffen , Paschereit Christian Oliver
Published: July 2013

Lean premixed combustion is prone to thermoacoustic instabilities. These mostly self-excited instabilities are caused by a feedback mechanism between the acoustic field, hydrodynamic structures, and the heat release rate in the flame. While various modeling tools are available for the linear analysis of thermoacoustic systems, a detailed knowledge of the governing nonlinearities, responsible for the saturation in the flame response, is still missing. The fundamental understanding of the flow field–heat release interaction is of crucial importance for the prediction of the pressure oscillation amplitude. To improve the understanding of these interaction processes, the current paper investigates the nonlinear interaction of the flow field and the unsteady heat release rate and the role of swirl fluctuations. The test rig that is used in the present work consists of a generic swirl-stabilized combustor fed with natural gas and equipped with a high-amplitude forcing device. The influence of the phase between axial and azimuthal velocity oscillations is assessed on the basis of the amplitude and phase relations between the velocity fluctuations at the inlet and the outlet of the burner. These relations are determined in the experiment with the Multi-Microphone-Method and a two component laser-Doppler velocimeter. Particle image velocimetry and OH*-chemiluminescence measurements are conducted to study the interaction between the flow field and the flame. For several frequency regimes, characteristic properties of the forced flow field and flame are identified, and a strong amplitude dependence is observed. It is found that the convective time delay between the swirl generator and the flame has an important influence on swirl-number oscillations and the flame dynamics in the low-frequency regime. For mid and high frequencies, significant changes in the mean flow field and the mean flame position are identified for high forcing amplitudes. These affect the interaction between coherent structures and the flame and are suggested to be responsible for the saturation in the flame response at high forcing amplitudes.
Flame Transfer Function Measurements With CH4 and H2 Fuel Mixtures at Ultra Wet Conditions in a Swirl Stabilized Premixed Combustor
Authors: Schimek Sebastian , Göke Sebastian , Schrödinger Christina , Paschereit Christian Oliver
Published: July 2013

The influence of humidity and fuel composition on thermoacoustic flame characteristics is investigated. This is an important aspect in the development of combustion chambers for humidified gas turbines. Thermoacoustic issues are in the focus of the current investigation. These pressure pulsations result from the interaction of combustor acoustics with an unsteady heat release of the flame and have a negative influence on the combustion process and can even damage components of the engine. A key point concerning combustion dynamics is the role of convective time lags which are determined by the temporal delay between the appearance of a perturbation and the response of the flame. Experiments are conducted with different fuel mixtures containing natural gas, hydrogen, and nitrogen, each with steam contents in the air mass flow of up to 40%. The multi-microphone method and OH* chemiluminescence measurements with a photomultiplier and an intensified CCD camera are used to determine the flame transfer function and flame dynamics. It is observed that the characteristics of the flame response are related to the flame shape and position rather than to the fuel composition or the steam content. Using a Strouhal-number normalization based on the bulk velocity of the annular jet and the distance between fuel injection and the flame, a good agreement between the phases of the flame transfer functions of all flames attached to the burner outlet is found.
Experimental Investigation on Effusion Liner Geometries for Aero-Engine Combustors: Evaluation of Global Acoustic Parameters
Authors: Andreini A. , Facchini B. , Ferrari L. , Lenzi G. , Simonetti F. , Peschiulli A.
Published: July 2013

In new generation aero-engines based on the innovative lean combustion technology, thermoacoustic instabilities are one of the most important issues and their prevention and reduction are challenging goals. To achieve these targets, the use of multi-perforated liners, that have to primarily provide an efficient liner cooling, is very attractive because they are efficient passive dampers of pressure fluctuations, especially with bias flow. The design of multi-perforated liners for both thermal and acoustic purposes can be accomplished by selecting liner parameters, such as hole diameter, pattern and inclination, main and bias Mach numbers, fulfilling both requirements; this procedure requires to assess the effect of both geometrical and fluid-dynamic features. Thus, a specific research project is ongoing on the acoustic and thermal experimental characterization of selected multi-perforated liner geometries. In this paper, the complete experimental campaign on the acoustic behavior of the aforementioned liners has been carried out in the planar wave field range, that is of main concern in aero-engines. For this purpose, an innovative modular test rig has been designed to characterize test cases at ambient conditions, changing bias and main flows up to operating engine conditions. Liner geometries account for 3 different hole diameters, 5 different patterns and 2 hole inclinations, ranging within typical cooling system values; tests were performed with the two-source multi-microphone technique to evaluate global acoustic parameters independently from test rig boundary conditions. The acoustic performances of liners are discussed in terms of the energy dissipation coefficient.
Development of “SAWBLAST®” Fuel Nozzle Concept for Improved Fuel Atomization and Mixing in High Performance Gas Turbine Combustors: Part I—Conceptual Design
Authors: Mawid Mohammed A. , Lee F. Philip
Published: July 2013

A novel piloted-single lip airblast fuel nozzle design concept termed “SAWBLAST®” was conceived, designed, fabricated, and tested. It has three airflow passages and two fuel circuits for pilot and main. The fuel nozzle was tested under cold flow conditions for spray characterization such as spray patternation, ACd, and SMD. A large test matrix that included over 22 design configurations, in addition to a baseline fuel nozzle was used. Based upon the cold flow spray characterization tests, two different fuel injector design configurations were down selected for combustion tests. The down selected configurations incorporated specific design features and geometries to reflect the novel fuel nozzle concept. The spray characterization tests for “SAWBLAST®” design configuration labeled as number 4 (in text) yielded a much improved spray patternation than a baseline piloted airblast fuel nozzle with a similar total ACd and under the same operating conditions. This improvement amounted to about 40% reduction in the spray patternation compared to the baseline fuel nozzle design. This level of improvement was deemed as substantial over the currently employed piloted airblast fuel nozzles. The same “SAWBLAST®” design configuration number 4 also showed better SMD performance than the baseline near the spray edges.
Improvement of the Outlet Temperature Distribution of a Dual-Fuel Gas Turbine Combustor by a Simplified CFD Model
Authors: Gobbato Paolo , Lazzaretto Andrea , Masi Massimo
Published: July 2013

The mixing process within the dilution zone noticeably affects the temperature field in the outlet section of a gas turbine combustor. In fact, dilution jets lower the temperature of the hot flow exiting the primary zone establishing suitable temperature profile and pattern factor at the combustor outlet. Thus, the dilution zone design has a significant impact on performance and durability of the turbine. In this study, a dual-fuel gas turbine combustor is investigated by a commercial finite-volume CFD code. The computational domain extends from the compressor discharge to the gas turbine inlet and it is meshed with a coarse grid since it was originally conceived for thermoacoustic analysis. The model has been already validated throughout measurements acquired during full scale isothermal and reactive tests. On the basis of the results of reactive simulations, several solutions of the dilution zone are designed to improve the uniformity of radial and circumferential temperature at the turbine inlet. The designed configurations feature number, arrangement and diameter of dilution holes which differ from the commercial configuration providing four identical dilution holes equally spaced. Advantages and drawbacks of each dilution zone layout are supported by results of numerical calculations. The results suggest that the solutions featuring two dilution holes perform better than the actual layout.
An Experimental and Numerical Study of the Laminar Flame Speed of Jet Fuel Surrogate Blends
Authors: Denman Bradley M. , Munzar Jeffrey D. , Bergthorson Jeffrey M.
Published: July 2013

Kerosene-type fuels are the most common aviation fuel, and an understanding of their combustion properties is essential for achieving optimized gas turbine operation. Presently, however, there is lack of experimental flame speed data available by which to validate the chemical kinetic mechanisms necessary for effective computational studies. In this study, premixed jet fuel surrogate blends and commercial kerosene are studied using particle image velocimetry in a stagnation flame geometry. Numerical simulations of each experiment are obtained using the CHEMKIN-PRO software package and the JetSurF 2.0 mechanism. The neat hydrocarbon surrogates investigated include n-decane, methylcyclohexane, and toluene, which represent the alkane, cycloalkane, and aromatic components of conventional aviation fuel, respectively. Two blends are studied in this paper. The first is a binary blend formulated to reproduce the laminar flame speed of aviation fuel using a mixing rule based on the laminar flame speed and adiabatic flame temperature of the hydrocarbon components, weighted by their respective mixture mole fractions. The second blend is a tertiary blend formulated to emulate the hydrogen to carbon ratio of the kerosene studied. All of the considered fuels and blends are studied at three equivalence ratios, corresponding to lean, stoichiometric, and rich conditions, and at several stretch rates. The centreline axial velocity profiles from numerical simulations are directly compared to the measured velocity profiles to validate the mechanism at each condition. The difference between the experimental and simulated reference flame speed is used to infer the true unstretched laminar flame speed of the mixture. These results allow the effectiveness of the different blending methodologies to be assessed.
Heating and Efficiency Comparison of a Fischer-Tropsch (FT) Fuel, JP-8+100, and Blends in a Three-Cup Combustor Sector
Authors: Thomas Anna E. , Saxena Nikita T. , Shouse Dale T. , Neuroth Craig , Lynch Amy , Frayne Charles W. , Stutrud Jeffrey S. , Corporan Edwin , Hankins Terry , Hendricks Robert C.
Published: July 2013

In order to realize alternative fueling for military and commercial use, the industry has set forth guidelines that must be met by each fuel. These aviation fueling requirements are outlined in MIL-DTL-83133F(2008) or ASTM D 7566-Annex standards and are classified as “drop-in” fuel replacements. This paper provides combustor performance data for synthetic-paraffinic-kerosene- (SPK-) type (Fisher-Tropsch (FT)) fuel and blends with JP-8+100, relative to JP-8+100 as baseline fueling. Data were taken at various nominal inlet conditions: 75 psia (0.52 MPa) at 500 °F (533 K), 125 psia (0.86 MPa) at 625 °F (603 K), 175 psia (1.21 MPa) at 725 °F (658 K), and 225 psia (1.55 MPa) at 790 °F (694 K). Combustor performance analysis assessments were made for the change in flame temperatures, combustor efficiency, wall temperatures, and exhaust plane temperatures at 3%, 4%, and 5% combustor pressure drop (%ΔP) for fuel:air ratios (F/A) ranging from 0.010 to 0.025. Significant general trends show lower liner temperatures and higher flame and combustor outlet temperatures with increases in FT fueling relative to JP-8+100 fueling. The latter affects both turbine efficiency and blade/vane life. In general, 100% SPK-FT fuel and blends with JP-8+100 produce less particulates and less smoke and have lower thermal impact on combustor hardware.
Characteristics of Deposits in Gas Turbine Combustion Chambers Using Synthetic and Conventional Jet Fuels
Authors: Pucher Greg , Allan William , Poitras Pierre
Published: July 2013

The synthetic fuel industry is poised to experience large scale growth and profoundly affect current aviation fuel infrastructure. New candidate technologies, such as Camelina oil-derived synthetic fuel have been demonstrated to not only provide satisfactory quasi drop-in characteristics for conventional fuels, but in life cycle analysis studies have also been shown to potentially offer positive improvements relative to conventional feedstocks with respect to economic, environmental, and land use considerations.

As part of a multi-year study at the Royal Military College of Canada to evaluate combustion related parameters of fuel additives and alternative fuels for gas turbine applications, a Camelina-derived synthetic fuel blend was assessed to determine potential combustion related benefits as compared to conventional and other synthetic blends. The Combustion Chamber Sector Rig (CCSR) which houses a Rolls Royce T-56-A-15 combustion section, was utilized for the evaluation of emissions and deposits. Following combustion testing, several combustion system components, including the combustion chamber, fuel nozzle and igniter plug were analyzed for relative levels of deposit build-up. As with other Fischer Tropsch derived synthetic fuels, there were positive benefits found with Camelina blends in terms of emissions performance and deposit production tendencies.
Consistent Theoretical Model of Mean Diameter and Size Distribution by Liquid Sheet Atomization
Authors: Inoue Chihiro , Watanabe Toshinori , Himeno Takehiro , Uzawa Seiji , Koshi Mitsuo
Published: July 2013

A consistent theoretical model is proposed and validated for calculating droplet diameters and size distributions. The model is derived based on the energy conservation law including the surface free energy and the Laplace pressure. Under several hypotheses, the law derives an equation indicating that atomization results from kinetic energy loss. Thus, once the amount of loss is determined, the droplet diameter is able to be calculated without the use of experimental parameters. When the effects of ambient gas are negligible, injection velocity profiles of liquid jets are the essential cause of the reduction of kinetic energy. The minimum Sauter mean diameter produced by liquid sheet atomization is inversely proportional to the injection Weber number when the injection velocity profiles are laminar or turbulent. A non-dimensional distribution function is also derived from the mean diameter model and Nukiyama-Tanasawa’s function. The new estimation methods are favorably validated by comparing with corresponding mean diameters and the size distributions, which are experimentally measured under atmospheric pressure.
Pratt and Whitney Gas Turbine Combustor Design Using ANSYS Fluent and User Defined Functions
Authors: Sen Baris A. , Guo Yanhu , McKinney Randal G. , Montanari Federico , Bedford Frederick C.
Published: July 2013

This paper summarizes work conducted at Pratt & Whitney to incorporate ANSYS Fluent into the computational fluid dynamics-based combustor design process. As a first step, turbulence, combustion and spray models that already exist and have been validated in the Pratt & Whitney legacy computational fluid dynamics (CFD) solver ALLSTAR were converted into user defined functions (UDFs) for usage with the core ANSYS Fluent solver. In this manner, a baseline solver was established that allowed a systematic testing of the ANSYS Fluent native models. The baseline solver was validated against computational results as well as experimental data obtained for (i) liquid jet in cross-flow (LJICF), (ii) ambient spray injector tests and (iii) Pratt & Whitney next generation product family configurations. These test cases established a thorough evaluation of ANSYS Fluent with UDFs on a spectrum of simple to complex geometries and flow physics relevant to the conditions encountered in aeroengine combustors. Results show that Fluent produces calculated results obtained by ALLSTAR with similar level of agreement to the experiments. Furthermore, Fluent provides better convergence compared to the legacy ALLSTAR solver with a similar computational resource requirement. The ANSYS Fluent native spray break-up models were also tested for the liquid jet in cross flow configuration, demonstrating the importance of modeling the stripping and primary break-up regime of a spray jet. This capability is currently available only via the use of UDFs.
An Equipment Reliability Strategy and Maintenance Program for Improving the Reliability of Cranes at Commercial Nuclear Power Facilities
Authors: Kriner Jeffrey B. , Lytle Bradford P. , Lauri John C.
Published: July 2013

Many commercial nuclear power facilities have been in operation well over 20 years, and many facilities have been or will have their original 40 year operating license renewed for an additional 20 years. The anticipated stresses to plant equipment and the longer service life increase the challenge to maintain reliable equipment performance. Establishing equipment maintenance programs that are effective and compliant with applicable regulations is critical to avoid unplanned equipment unavailability and the potential costs of lost generation. An equipment reliability (ER) strategy for commercial nuclear power plant equipment is described that considers the programmatic recommendations of the Institute of Nuclear Power Operations ([1], [2]), Electric Power Research Institute ([3], [4], [5], [6]), Nuclear Energy Institute standard nuclear business model [7], Nuclear Regulatory Commission ([8], [9], [10], [11]), and industry societies and working groups, such as the American Society of Mechanical Engineers ([12], [13]). All ER strategies must properly implement mandatory requirements and commitments ([14], [15], [16]). Additionally, ER strategies should also consider the appropriate manufacturer/vendor recommendations, industry and plant personnel operating experience feedback, equipment operating and maintenance history information, etc. As a result, the ER strategy includes reviewing multiple information sources to inform the decisions to either include or exclude the specific maintenance activities that impact reliability. Ultimately the maintenance program is tailored for each equipment application and implements the necessary maintenance activities while avoiding the cost of performing unnecessary maintenance activities.
Finite Element Analysis of Laser Welding Induced Alignment Distortion During Pigtail of Pump Lasers
Authors: Labudovic M. , Cook M.
Published: July 2013

Laser Welding Induced Alignment Distortion (WIAD) during pigtailing of pump lasers has been numerically modeled and studied experimentally. The results demonstrate that the WIAD can be minimized by properly controlling the laser beam energy delivery. A 3D finite element model has been developed for effectively predicting the WIAD.
Design of Cast Pin Fin Coldwalls for Air-Cooled Electronics Systems
Authors: Short B. Elliott , Price Donald C. , Raad Peter E.
Published: July 2013

At low to moderate Reynolds numbers, cast pin fin coldwalls provide the best performance and lowest unit cost for air-cooled electronics systems. Until recently, insufficient data existed to design coldwalls with moderate length pin fins for electronics systems. Empirical correlations for the Fanning friction factor, f = f(S/d, T/d, L/d, Red), and the Colburn j-factor, j = j(S/d, T/d, L/d, Red), were previously developed for two flow regimes with a transition Reynolds number, Retrn, separating the two regimes. Using these correlations, the effect of configuration on the design is discussed and a design procedure is proposed. Example problems are presented for (1) a system cooled by an environmental control system, and (2) a system cooled by ambient air using a fan.
Thermal Management of QFN 48 Package Attached to Different Multi-Layers of Printed Circuit Board Designs
Authors: Chia John , Yang Charles
Published: July 2013

A near CSP plastic encapsulated package with a quad flat non-leaded (QFN) structure has been drawn much attention due to it small size and lightweight applications. Thermal efficiency is the major concern for adopting such type of package in place of TSSOP package. The thermal dissipation for electronics with the higher power consumption is current developing to it uppermost limitation as a wire bonded, lead-frame substrate type of QFN with various pine counts and body sizes. It is therefore an object of the present study to investigate thermal performance of QFN package optimum design attached on different layers and thickness of laminated printed circuit board (PCB), which is further related to reliability issue of this type of IC package. Numerical simulation illustrates how the thermal efficiency of the QFN package can be reached with different PCB designs and airflow conditions.
Study on Alternative Cooling Methods Beyond Next Generation Microprocessors
Authors: Chan Albert , Wei Jie
Published: July 2013

Feasibility study on alternative cooling methods to air-cooling with heat sinks is provided in this paper. The study focuses on cooling of 64-bit microprocessor at 80nm technology node with projected heat dissipation of 200W. An example was presented to illustrate limitation of air-cooling for the 200W microprocessor using an all-Cu heat sink with tall fins. Three alternatives to air-cooling were studied in this work: liquid cooling, two-phase convective flow cooling and refrigeration cooling. Thermodynamic analysis was used to estimate operating conditions and fluid flow rates for each alternative. The information provides a preliminary basis for assessing capabilities and weaknesses among alternatives. Liquid and two-phase cooling simply transfer heat from high to low temperature. In contrast, refrigeration cooling operates as a heat pump, moving heat from low to high temperature. Refrigeration cooling offers capability to cool microprocessor (LSI) chip to temperatures below ambient or freezing. The drawback is more heat must be removed from the system. Liquid cooling operates at close to ambient pressure, while two-phase and refrigeration cooling operate at higher pressures. Challenges to implementation of all three alternatives include availability of low cost, miniature components (pumps or compressors, heat exchanger and condenser), designing for redundancy (or reliability) and ease of installation and field service. In terms of component availability and cost, liquid cooling is preferred choice, followed by two-phase and refrigeration cooling.
Towards Next Generation of Switching
Authors: Vukovic Alex , Savoie Michel , Hua Heng
Published: July 2013

The heart of next generation networks is currently centered on building blocks for performing transport, switching, routing, amplification, attenuation, storage and conversion functions. One of the key elements of the network is a switch, which might perform as an optical switch (optical-electrical-optical, or OEO) or a “purely” photonic switch (optical-optical-optical or OOO). The merits and benefits of both in actual network applications are analyzed and outlined. Although both switches have their own advantages as a network element, the full judgement of their role in next generation networks requires an “overall network view”. Network functionalities such as grooming capabilities, scalability, traffic management, protection, line equalization or performance monitoring are those taken in competitive analyses in terms to understand some impacts of switch choice in the network. It is expected that both optical and photonic switches will play complementary roles in next generation networks. Combined with new communication technology advances in routing, transport, amplification and wavelength conversion, both switches will be the cornerstones of next generation solutions, each one with its specific role.
Thermal Analysis of Natural Convection Cooled Switch Mode Power Supplies
Authors: Koizumi Katsuhiro , Joboji Akito , Nagahara Kuniaki , Ishizuka Masaru
Published: July 2013

This paper describes an application example of thermal flow simulation to the design of a switch mode power supply (SMPS) that is natural convection air-cooled. In this analysis, the modeling of printed circuit board (PCB) and power semiconductor devices was examined using the design of experiments method. The PCB was treated as a simple plate, and average thermal conductivity was not considered. The power semiconductor devices were modeled as a simple hexahedral resistive network block. As the heat generation sources, a field effect transistor (FET) and a diode were considered in the simulation, and the calculation method of power loss is described. The difference between measured and calculated values for power semiconductor devices was found to be within approximately 10 K.
The Development of a Bonded Fin Graphite/Epoxy Heat Sink for High Performance Servers
Authors: Marotta E. E. , Ellsworth M. J. , Norley J. , Getz G.
Published: July 2013

IBM’s has recently introduced a high performance server that utilizes multichip modules that dissipate very high heat loads. Each multichip module consists of four microprocessor chips encased by a copper cap that serves to spread the heat load over an area of roughly 113 mm × 113 mm. The module is air cooled by a single aluminum alloy bonded-fin fan sink. For applications requiring the microprocessors to operate at higher frequencies, the aluminum heat sink, with its lower thermal conductivity, cannot provide sufficient cooling; therefore, a copper heat sink must be employed. However, copper alloys have the disadvantage of a significant weight penalty (density ∼ 8.9 g/cm3), being 3.3 times heavier than aluminum (density ∼ 2.7 g/cm3), and is significantly more costly to manufacture. A novel approach for an improved heat sink has been developed using a new natural graphite-based/epoxy composite material. This material has low density (∼1.9 g/cm3) and anisotropic thermal conductivity (∼370 W/m-K in two directions, ∼ 7 W/m-K in the third direction). Bonded fin manufacturing methods have been developed to produce a heat sink that exploits the material’s high thermal conductivity when used in combination with a copper spreader module, such as used in the IBM server. Convective heat sink thermal performance approaching that of copper (e.g. 0.030 °C/W) has been achieved at a fraction of copper’s weight. Therefore, additional hardware required to allow the copper heat sinks to withstand shock and vibration standards, was not necessary with the lightweight graphite solution. Mechanical issues involved with using the lower strength graphite materials in a metal retrofit situation had to be resolved. Solutions included the use of aluminum end plates to provide edge protection to the heat sink with metal stiffeners inserted into the base for extra structural integrity. A variety of mechanical attachment methods was evaluated to join the graphite to the copper heat spreader. Lapping procedures were developed for the graphite heat sink to provide the required flatness necessary to minimize the temperature drop across the interface.
Ultra-Thin and High-Density Packaging Using Both Sides Flip Chip Technology
Authors: Nishida Kazuto , Shimizu Kazumichi , Yoshino Michiro , Koguchi Hideo , Taweejun Nipon
Published: July 2013

We have developed a high-density packaging technology by using a thin IC and a thin substrate and bonding it by new flip chip technology. Numerical analysis with the finite element method (FEM) as well experiments clearly showed that deflection of the IC and reliability were affected by the IC thickness. Consequently, reliability could be improved by reducing IC thickness. The dependency of the life in single-sided CSP and both-sided CSP on the thickness of IC and substrate could be expressed using a normal stress in the thickness direction and shear stress in the vertical cross section, respectively. Moreover, a both-sided flip chip approach solved the problem of warpage. A high-capacity memory card of 512 MB was put to practical use by applying these results. This increased the Si density by four times over that of a conventional chip-size package (CSP).
Numerical Evaluation of High Power Amplifier Heat Sink Design Options
Authors: Maguire Luke , Behnia Masud , Morrison Graham
Published: July 2013

Numerical techniques have been used to evaluate various modifications to the design of a cooling system currently used for high power RF signal amplifiers. The system utilises a 300mm long × 220mm wide × 70mm high heat sink in forced turbulent air flows up to 120 litres per second. Using Computational Fluid Dynamics (CFD) software a detailed model of the heat sink, primary transistors and air flow was created. Experimental data obtained from the working system was used to validate the simulation results. The model was then modified to test the effects of various changes to the cooling system including incorporation of heat spreading techniques, elimination of bypass flow and changes to fin geometry. Reductions in transistor junction temperature of between 9°C and 12°C were predicted through the use of a copper heat spreader or full copper heat sink while the elimination of bypass flow reduced junction temperatures by up to 6°C. Strip fin and staggered fin arrangements provided little improvement, however by halving fin pitch and fin thickness (i.e doubling heat transfer area) device temperature reductions of 4°C were possible.
Numerical Calculation of Sub-Micron Hot Spot in Si Devices
Authors: Fushinobu Kazuyoshi , Maruyama Hirohisa
Published: July 2013

Numerical calculation of silicon MOSFET is performed. Conjugate nature of the thermal and electrical behavior in the device is considered, and the lattice temperatures is solved as well as the electron concentration and the electron temperature. The calculated results shows the importance of considering both the electron and lattice temperatures for device modeling; the electron temperature has a significant impact on the calculated electron concentration and the lattice temperature. Submicron local hot spot is observed in the device, and its characteristics are discussed.