45 Matching Results

Search Results

Advanced search parameters have been applied.

Experimental and computational studies of film cooling with compound angle injection

Description: The thermal efficiency of gas turbine systems depends largely on the turbine inlet temperature. Recent decades have seen a steady rise in the inlet temperature and a resulting reduction in fuel consumption. At the same time, it has been necessary to employ intensive cooling of the hot components. Among various cooling methods, film cooling has become a standard method for cooling of the turbine airfoils and combustion chamber walls. The University of Minnesota program is a combined experimental and computational study of various film-cooling configurations. Whereas a large number of parameters influence film cooling processes, this research focuses on compound angle injection through a single row and through two rows of holes. Later work will investigate the values of contoured hole designs. An appreciation of the advantages of compound angle injection has risen recently with the demand for more effective cooling and with improved understanding of the flow; this project should continue to further this understanding. Approaches being applied include: (1) a new measurement system that extends the mass/heat transfer analogy to obtain both local film cooling and local mass (heat) transfer results in a single system, (2) direct measurement of three-dimensional turbulent transport in a highly-disturbed flow, (3) the use of compound angle and shaped holes to optimize film cooling performance, and (4) an exploration of anisotropy corrections to turbulence modeling of film cooling jets.
Date: December 31, 1995
Creator: Goldstein, R.J.; Eckert, E.R.G.; Patankar, S.V. & Simon, T.W.
Partner: UNT Libraries Government Documents Department

Rayleigh/Raman/LIF measurements in a turbulent lean premixed combustor

Description: Much of the industrial electrical generation capability being added worldwide is gas-turbine engine based and is fueled by natural gas. These gas-turbine engines use lean premixed (LP) combustion to meet the strict NO{sub x} emission standards, while maintaining acceptable levels of CO. In conventional, diffusion flame gas turbine combustors, large amount of NO{sub x} forms in the hot stoichiometric zones via the Zeldovich (thermal) mechanism. Hence, lean premixed combustors are rapidly becoming the norm, since they are specifically designed to avoid these hot stoichiometric zones and the associated thermal NO{sub x}. However, considerable research and development are still required to reduce the NO{sub x} levels (25-40 ppmvd adjusted to 15% O{sub 2} with the current technology), to the projected goal of under 10 ppmvd by the turn of the century. Achieving this objective would require extensive experiments in LP natural gas (or CH{sub 4}) flames for understanding the combustion phenomena underlying the formation of the exhaust pollutants. Although LP combustion is an effective way to control NO{sub x}, the downside is that it increases the CO emissions. The formation and destruction of the pollutants (NO{sub x} and CO) are strongly affected by the fluid mechanics, the finite-rate chemistry, and their (turbulence-chemistry) interactions. Hence, a thorough understanding of these interactions is vital for controlling and reducing the pollutant emissions. The present research is contributing to this goal by providing a detailed nonintrusive laser based data set with good spatial and temporal resolutions of the pollutants (NO and CO) along with the major species, temperature, and OH. The measurements reported in this work, along with the existing velocity data on a turbulent LP combustor burning CH{sub 4}, would provide insight into the turbulence-chemistry interactions and their effect on pollutant formation.
Date: December 31, 1995
Creator: Nandula, S.P.; Pitz, R.W.; Barlow, R.S. & Fiechtner, G.J.
Partner: UNT Libraries Government Documents Department

Combustion chemical vapor deposited coatings for thermal barrier coating systems

Description: The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings. In this report, the evaluation of alumina and ceria coatings on a nickel-chromium alloy is described.
Date: December 31, 1995
Creator: Hampikian, J.M. & Carter, W.B.
Partner: UNT Libraries Government Documents Department

Advanced multistage turbine blade aerodynamics, performance, cooling, and heat transfer

Description: The gas turbine has the potential for power production at the highest possible efficiency. The challenge is to ensure that gas turbines operate at the optimum efficiency so as to use the least fuel and produce minimum emissions. A key component to meeting this challenge is the turbine. Turbine performance, both aerodynamics and heat transfer, is one of the barrier advanced gas turbine development technologies. This is a result of the complex, highly three-dimensional and unsteady flow phenomena in the turbine. Improved turbine aerodynamic performance has been achieved with three-dimensional highly-loaded airfoil designs, accomplished utilizing Euler or Navier-Stokes Computational Fluid Dynamics (CFD) codes. These design codes consider steady flow through isolated blade rows. Thus they do not account for unsteady flow effects. However, unsteady flow effects have a significant impact on performance. Also, CFD codes predict the complete flow field. The experimental verification of these codes has traditionally been accomplished with point data - not corresponding plane field measurements. Thus, although advanced CFD predictions of the highly complex and three-dimensional turbine flow fields are available, corresponding data are not. To improve the design capability for high temperature turbines, a detailed understanding of the highly unsteady and three-dimensional flow through multi-stage turbines is necessary. Thus, unique data are required which quantify the unsteady three-dimensional flow through multi-stage turbine blade rows, including the effect of the film coolant flow. Also, as design CFD codes do not account for unsteady flow effects, the next logical challenge and the current thrust in CFD code development is multiple-stage analyses that account for the interactions between neighboring blade rows. Again, to verify and or direct the development of these advanced codes, complete three-dimensional unsteady flow field data are needed.
Date: December 31, 1995
Creator: Fleeter, S. & Lawless, P.B.
Partner: UNT Libraries Government Documents Department

Intramolecular energy- and electron-transfer reactions in polymetallic complexes. Annual report

Description: The complexes (tpy)Ru(II)(tpp)Co(III)(PPhEt{sub 2})H{sub 2}{sup 3+}, (NC){sub 3}Fe(II)(tpp)Co(III)(PPhEt{sub 2})H{sub 2} and (NC){sub 3}Fe(II)(tpp)Co(III)(PPh{sub 3})H{sub 2} (where tpp = 2,3,5,6-tetrakis(2{prime}-pyridyl)pyrazine), were prepared and their photochemistry studied. Reasons for the low quantum yields for H{sub 2} production are discussed briefly. A series of FeRuRh complexes is being prepared. Plans for the coming year on intramolecular energy transfer and charge separation are discussed.
Date: December 1, 1991
Creator: Peterson, J.D.
Partner: UNT Libraries Government Documents Department

Advanced turbine cooling, heat transfer, and aerodynamic studies

Description: The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect of Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.
Date: December 31, 1995
Creator: Han, Je-Chin & Schobeiri, M.T.
Partner: UNT Libraries Government Documents Department

Flow interaction in the combustor-diffusor system of industrial gas turbines

Description: This paper presents an experimental/computational study of cold flow in the combustor-diffuser system of industrial gas turbines to address issues relating to flow interactions and pressure losses in the pre- and dump diffusers. The present configuration with can annular combustors differs substantially from the aircraft engines which typically use a 360 degree annular combustor. Experiments were conducted in a one-third scale, annular 360-degree model using several can combustors equispaced around the turbine axis. A 3-D computational fluid dynamics analysis employing the multidomain procedure was performed to supplement the flow measurements. The measured data correlated well with the computations. The airflow in the dump diffuser adversely affected the prediffuser flow by causing it to accelerate in the outer region at the prediffuser exit. This phenomenon referred to as the sink-effect also caused a large fraction of the flow to bypass much of the dump diffuser and go directly from the prediffuser exit to the bypass air holes on the combustor casing, thereby, rendering the dump diffuser ineffective in diffusing the flow. The dump diffuser was occupied by a large recirculation region which dissipated the flow kinetic energy. Approximately 1.2 dynamic head at the prediffuser inlet was lost in the combustor-diffuser system; much of it in the dump diffuser where the fluid passed through the narrow gaps and pathways. Strong flow interactions in the combustor-diffuser system indicate the need for design modifications which could not be addressed by empirical correlations based on simple flow configurations.
Date: May 1, 1996
Creator: Agrawal, A.K.; Kapat, J.S. & Yang, T.
Partner: UNT Libraries Government Documents Department

The PEAK experience in South Carolina

Description: The PEAK Institute was developed to provide a linkage for formal (schoolteachers) and nonformal educators (extension agents) with agricultural scientists of Clemson University`s South Carolina Agricultural Experiment Station System. The goal of the Institute was to enable teams of educators and researchers to develop and provide PEAK science and math learning experiences related to relevant agricultural and environmental issues of local communities for both classroom and 4-H Club experiences. The Peak Institute was conducted through a twenty day residential Institute held in June for middle school and high school teachers who were teamed with an Extension agent from their community. These educators participated in hands-on, minds-on sessions conducted by agricultural researchers and Clemson University Cooperative Extension specialists. Participants were given the opportunity to see frontier science being conducted by scientists from a variety of agricultural laboratories.
Date: November 1, 1998
Partner: UNT Libraries Government Documents Department

Life prediction of advanced materials for gas turbine application

Description: Emphasis is placed on life characterization based on low cycle fatigue under isothermal conditions and thermomechanical fatigue. Microstructure of failed coated and uncoated specimens is being analyzed. IN 738 LC is the material; the coating is either overlay (NiCoCrAly) or NiAl-based aluminide.
Date: December 31, 1995
Creator: Zamrik, S.Y.; Ray, A. & Koss, D.A.
Partner: UNT Libraries Government Documents Department

Effects of geometry on slot-jet film cooling performance

Description: Physics of film cooling for shaped, inclined slot-jets with realistic slot-length-to-width ratios is studied for a range of blowing ratio and density ratio parameters typical of gas turbine operations. Effect of inlet and exit shaping of the slot-jet on both flow and thermal field is isolated, and the dominant mechanisms responsible for differences in these items are documented. A computation method was used to study 4 configurations. Field results and surface phenomena are presented. Both adiabatic film effectiveness and heat transfer coefficient are vital in assessing film cooling performance. Performance of two popular turbulence models were studied to evaluate ability to handle highly elliptic jet/crossflow interaction type processes. The simulations were consistent.
Date: December 31, 1995
Creator: Hyams, D.G.; McGovern, K.T. & Leyiek, J.H.
Partner: UNT Libraries Government Documents Department

Combustion instability modeling and analysis

Description: It is well known that the two key elements for achieving low emissions and high performance in a gas turbine combustor are to simultaneously establish (1) a lean combustion zone for maintaining low NO{sub x} emissions and (2) rapid mixing for good ignition and flame stability. However, these requirements, when coupled with the short combustor lengths used to limit the residence time for NO formation typical of advanced gas turbine combustors, can lead to problems regarding unburned hydrocarbons (UHC) and carbon monoxide (CO) emissions, as well as the occurrence of combustion instabilities. The concurrent development of suitable analytical and numerical models that are validated with experimental studies is important for achieving this objective. A major benefit of the present research will be to provide for the first time an experimentally verified model of emissions and performance of gas turbine combustors. The present study represents a coordinated effort between industry, government and academia to investigate gas turbine combustion dynamics. Specific study areas include development of advanced diagnostics, definition of controlling phenomena, advancement of analytical and numerical modeling capabilities, and assessment of the current status of our ability to apply these tools to practical gas turbine combustors. The present work involves four tasks which address, respectively, (1) the development of a fiber-optic probe for fuel-air ratio measurements, (2) the study of combustion instability using laser-based diagnostics in a high pressure, high temperature flow reactor, (3) the development of analytical and numerical modeling capabilities for describing combustion instability which will be validated against experimental data, and (4) the preparation of a literature survey and establishment of a data base on practical experience with combustion instability.
Date: December 31, 1995
Creator: Santoro, R.J.; Yang, V.; Santavicca, D.A. & Sheppard, E.J.
Partner: UNT Libraries Government Documents Department

Advanced Sensing and Control Techniques to Facilitate Semi-Autonomous Decommissioning of Hazardous Sites - Final Report

Description: This report summarizes work after 4 years of a 3-year project (no-cost extension of the above-referenced project for a period of 12 months granted). The fourth generation of a vision sensing head for geometric and photometric scene sensing has been built and tested. Estimation algorithms for automatic sensor calibration updating under robot motion have been developed and tested. We have modified the geometry extraction component of the rendering pipeline. Laser scanning now produces highly accurate points on segmented curves. These point-curves are input to a NURBS (non-uniform rational B-spline) skinning procedure to produce interpolating surface segments. The NURBS formulation includes quadrics as a sub-class, thus this formulation allows much greater flexibility without the attendant instability of generating an entire quadric surface. We have also implemented correction for diffuse lighting and specular effects. The QRobot joint level control was extended to a complete semi-autonomous robot control system for D and D operations. The imaging and VR subsystems have been integrated and tested.
Date: December 1, 2000
Creator: Schalkoff, R.J.
Partner: UNT Libraries Government Documents Department

Advanced sensing and control techniques to facilitate semi-autonomous decommissioning. 1998 annual progress report

Description: 'This research is intended to advance the technology of semi-autonomous teleoperated robotics as applied to Decontamination and Decommissioning (D and D) tasks. Specifically, research leading to a prototype dual-manipulator mobile work cell is underway. This cell is supported and enhanced by computer vision, virtual reality and advanced robotics technology. This report summarizes work after approximately 1.5 years of a 3-year project. The autonomous, non-contact creation of a virtual environment from an existing, real environment (virtualization) is an integral part of the workcell functionality. This requires that the virtual world be geometrically correct. To this end, the authors have encountered severe sensitivity in quadric estimation. As a result, alternative procedures for geometric rendering, iterative correction approaches, new calibration methods and associated hardware, and calibration quality examination software have been developed. Following geometric rendering, the authors have focused on improving the color and texture recognition components of the system. In particular, the authors have moved beyond first-order illumination modeling to include higher order diffuse effects. This allows us to combine the surface geometric information, obtained from the laser projection and surface recognition components of the system, with a stereo camera image. Low-level controllers for Puma 560 robotic arms were designed and implemented using QNX. The resulting QNX/PC based low-level robot control system is called QRobot. A high-level trajectory generator and application programming interface (API) as well as a new, flexible robot control API was required. Force/torque sensors and interface hardware have been identified and ordered. A simple 3-D OpenGL-based graphical Puma 560 robot simulator was developed and interfaced with ARCL and RCCL to assist in the development of robot motion programs.'
Date: June 1, 1998
Creator: Schalkoff, R.J.; Geist, R.M. & Dawson, D.M.
Partner: UNT Libraries Government Documents Department

Advanced sensing and control techniques to facilitate semi-autonomous decommissioning of hazardous sites. 1997 annual progress report, September 15, 1996--September 14, 1997

Description: 'The first year of this effort emphasized independent development and refinement of each of the three major subsystems (imaging/AI, robotics and virtual reality). Two of the three efforts emphasized the critical task of site. virtualization, prior to telepresence-guided D and D. Substantial algorithm refinement and software and hardware development occurred in each area. Relevant publications resulting from this work are cited below.'
Date: October 1, 1997
Creator: Schalkoff, R.J.
Partner: UNT Libraries Government Documents Department

The magnesium chelation step in chlorophyll biosynthesis. Progress report 1993

Description: Progress is reported on the identification and fractionation of Magnesium chealatase, an enzyme involved in addition of Mg to chlorophyll during the later`s biosynthesis. Progress is documented as a series of synopsis of published and unpublished papers by the author.
Date: December 1993
Creator: Weinstein, J. D.
Partner: UNT Libraries Government Documents Department

Air extraction in gas turbines burning coal-derived gas

Description: In the first phase of this contracted research, a comprehensive investigation was performed. Principally, the effort was directed to identify the technical barriers which might exist in integrating the air-blown coal gasification process with a hot gas cleanup scheme and the state-of-the-art, US made, heavy-frame gas turbine. The guiding rule of the integration is to keep the compressor and the expander unchanged if possible. Because of the low-heat content of coal gas and of the need to accommodate air extraction, the combustor and perhaps, the flow region between the compressor exit and the expander inlet might need to be modified. In selecting a compressed air extraction scheme, one must consider how the scheme affects the air supply to the hot section of the turbine and the total pressure loss in the flow region. Air extraction must preserve effective cooling of the hot components, such as the transition pieces. It must also ensure proper air/fuel mixing in the combustor, hence the combustor exit pattern factor. The overall thermal efficiency of the power plant can be increased by minimizing the total pressure loss in the diffusers associated with the air extraction. Therefore, a study of airflow in the pre- and dump-diffusers with and without air extraction would provide information crucial to attaining high-thermal efficiency and to preventing hot spots. The research group at Clemson University suggested using a Griffith diffuser for the prediffuser and extracting air from the diffuser inlet. The present research establishes that the analytically identified problems in the impingement cooling flow are factual. This phase of the contracted research substantiates experimentally the advantage of using the Griffith diffuser with air extraction at the diffuser inlet.
Date: November 1, 1993
Creator: Yang, Tah-teh; Agrawal, A. K. & Kapat, J. S.
Partner: UNT Libraries Government Documents Department

Air extraction and LBTU coal gas combustion in gas turbines for IGCC systems

Description: The primary objective of the cold flow experiments is to study the effects of air extraction from two sites in a heavy-frame gas turbine: (1) the engine wrapper or manholes and (2) the compressor/combustor prediffuser inlet. The experiments involve a scale model of components of a state-of-the-art, US made gas turbine between the compressor exit and the turbine inlet Specifically, the purpose is to observe and measure how air extraction affects the flow distribution around the combustor cans and the impingement cooling flow rates on transition pieces of the combustor. The experimental data should provide turbine manufacturers the information needed to determine their preferred air extraction site. The secondary objectives for the experiments are as follows: (1) to identify regions with high-pressure losses, (2) to develop a dam base which will validate computational fluid dynamic calculations, and (3) to establish an experimental facility which may be used to assist the US industry in improving the aerodynamic design of nonrotating components of a heavy-frame gas turbine.
Date: January 1, 1992
Creator: Yang, Tah-teh; Agrawal, A.K. & Kapat, J.S.
Partner: UNT Libraries Government Documents Department

Advanced Gas Turbine Systems Research. Technical progress report, April 1, 1993--June 30, 1993

Description: The responses to the first Request for Proposals issued by AGTSR in March were received and evaluated by the industrial Review Board. Ten were selected for subcontract awards, which are presently being negotiated. The number of Performing Member universities has increased by six, to 56, since the last report. Two additional members are pending.
Date: December 31, 1993
Partner: UNT Libraries Government Documents Department

University participation in the ATS program

Description: The Advanced Gas Turbine Systems Research Program was included in DOE`s Advanced Turbine Systems initiative to conduct basic research in support of the overall ATS program, and to strengthen the university gas turbine technology base in the USA. The results of the research will be transferred to the industrial members to enhance and/or facilitate their designs of advanced gas turbine powerplants. Concurrently, the involvement of many students both graduate and undergraduate, will provide a better qualified group of engineers for hire by the industry.
Date: November 1, 1993
Creator: Allen, R. P. & Golan, L. P.
Partner: UNT Libraries Government Documents Department

Bond strength and stress measurements in thermal barrier coatings

Description: Thermal barrier coatings have been used extensively in aircraft gas turbines for more than 15 years to insulate combustors and turbine vanes from the hot gas stream. Plasma sprayed thermal barrier coatings (TBCs) provide metal temperature reductions as much as 300{degrees}F, with improvements in durability of two times or more being achieved. The introduction of TBCs deposited by electron beam physical vapor deposition (EB-PVD) processes in the last five years has provided a major improvement in durability and also enabled TBCs to be applied to turbine blades for improved engine performance. This program evaluates the bond strength of yttria stabilized zirconia coatings with MCrAlY and Pt-Al bond coats utilizing diffraction and fluorescence methods.
Date: December 31, 1995
Creator: Gell, M. & Jordan, E.
Partner: UNT Libraries Government Documents Department

Separation of Fischer-Tropsch wax from catalyst by supercritical extraction. Quarterly progress report, October 1, 1996--December 31, 1996

Description: One of the major objectives of this research project is to predict the phase behavior of model wax compounds in dense supercritical fluids such as hexane. Because initial results with the SAFT equation have been less promising than expected, the group at North Carolina State University has focused their recent attention on cubic equations of state, in particular the Peng-Robinson and Soave-Redlich-Kwong versions. The focus of this work has been on developing correlations that can be used to predict binary interaction parameters (i.e., k{sub ij}s) for a given binary wax-solvent system. As a first step, k{sub ij}s were first calculated from experimental data on systems containing alkanes between nC{sub 4} and nC{sub 23} at temperatures between 25 and 357{degrees} C. Attempts were then made to correlate these parameters with specific pure component properties of the alkanes of interest. Reasonably good agreement between experimental and predicted k{sub ij}s was found using a correlation that incorporates both temperature and the molecular size of the alkanes. As phase equilibrium data becomes available for higher molecular weight model wax compounds, the ability of the correlation to handle such systems will need to be tested. The phase equilibrium apparatus is currently undergoing modifications that will allow the system to run components that are solids at ambient temperatures. Some problems are still being resolved, as the heavy component tends to precipitate in the sample lines. Modifications have been made that should allow the system to operate reliably.
Date: January 1, 1997
Creator: Joyce, P.C. & Thies, M.C.
Partner: UNT Libraries Government Documents Department

Improved modeling techniques for turbomachinery flow fields

Description: This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbomachinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. This will be accomplished in a cooperative program by Penn State University and the Allison Engine Company. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tenor.
Date: December 31, 1995
Creator: Lakshminarayana, B. & Fagan, J.R. Jr.
Partner: UNT Libraries Government Documents Department

XRF and leaching characterization of waste glasses derived from wastewater treatment sludges

Description: Purpose of this study was to investigate use of XRF (x-ray fluorescence spectrometry) as a near real-time method to determine melter glass compositions. A range of glasses derived from wastewater treatment sludges associated with DOE sites was prepared. They were analyzed by XRF and wet chemistry digestion with atomic absorption/inductively coupled emission spectrometry. Results indicated good correlation between these two methods. A rapid sample preparation and analysis technique was developed and demonstrated by acquiring a sample from a pilot-scale simulated waste glass melter and analyzing it by XRF within one hour. From the results, XRF shows excellent potential as a process control tool for waste glass vitrification. Glasses prepared for this study were further analyzed for durability by toxicity characteristic leaching procedure and product consistency test and results are presented.
Date: December 1, 1994
Creator: Ragsdale, R.G., Jr
Partner: UNT Libraries Government Documents Department