Position indicating, rotating boom

Universal multiplanar position indicating, rotating boom for mounting various instruments or sensors is described. Boom is telescoping, and apparatus is capable of 3 types of rotation controlled by electric motors. Movement may be continuous or incremental

Nitric Oxide Pathways in Surface-Flame Radiant Burners

Nitrogen oxide (NOx) formation in surface-flame burners is studied. Surface-flame burners are typically made of metal fibers, ceramic fibers, or ceramic foam and provide radiant flux with low pollutant emissions. A one-dimensional model represents combustion on and within the porous medium using multistep chemistry, separate gas and energy equations, and a radiatively participating porous medium. We describe experimental measurements of NOx profiles above a surface-flame burner and compare them to model predictions. The model predicts NOx concentration with reasonable success. Deviations between model and experiment are primarily the result of heat loss in the experiment that is not considered in the model. Reaction rate analysis is performed to identify the chemical kinetic source of NO in the flame. Zeldovich NO is significant only at the highest firing rate studied (600 kW/m2, ϕ = 0.9), where it is responsible for 50-60% of the total NO. At the lower firing rates (200 and 300 kW/m2, ϕ = 0.9), where total NO is low, nearly all of the NO is formed in the flame front. Zeldovich NO accounts for 20-30% percent of the total NO, the Fenimore pathway accounts for less than 10% of the NO, and 50-75% percent of the NO is formed through the NNH, N2O and other paths. Sensitivity analysis shows that NO production in the flame front is most sensitive to NNH+O = NH+NO, with CH+N2 = HCN+N having the second highest sensitivity coefficient. At the lower firing rates NO emission is insensitive to porous medium properties, while at the high firing rate NO emission is slightly sensitive to porous medium properties

Non-Catalytic NOx Removal from Gas Turbine Exhaust with Cyanuric Acid in a Recirculating Reactor; Small Scale Evaluation and Industrial Application

A novel SNC technique to remove oxides of nitrogen (NOx) from stationary gas turbine exhaust has been investigated and applied. The technique employs the use of cyanuric acid (CYA), a non-toxic, dry powder, combined with the injection of auxiliary turbine fuel and recirculation. During the initial investigation, exhaust, generated by a 150 kW gas turbine, was treated in an insulated recirculation reactor, with a mean residence time of 0.65 to 0.71 seconds and a pressure drop of 660 Pa. In the reactor, autoignition of injected auxiliary gas turbine fuel raises the flue gas temperature to between 700 and 800 ºC. CYA slurry is injected. Temperature rise and NOx reduction occur simultaneously. Load following has been achieved. At all temperatures, significant NOx reduction from initial concentrations of 106 to 124 ppm to as low as 18 ppm at 15% O2 have been observed. However, The process generates N2O emissions, which vary from 45 to 163 ppm, increasing with increasing CYA/NOx ratio. The ratio of N2O formed to NO removed was found to be between 1 to 1.5 to 1. The performance of CYA ((HNCO)3) is compared to that of ammonia (NH3) and urea ((NH2)2CO). A numerical model, which combines a detailed chemical kinetic mechanism with recirculation, has been developed. The model captures all observed trends well and is an invaluable guide to improved understanding of the interactive NOx removal process. The process was then successfully scaled up and applied to a variety of industrial 3.7 MW gas turbines and similarly significant NOx reduction has been achieved

Structure and dynamics of colloidal depletion gels: coincidence of transitions and heterogeneity

Transitions in structural heterogeneity of colloidal depletion gels formed through short-range attractive interactions are correlated with their dynamical arrest. The system is a density and refractive index matched suspension of 0.20 volume fraction poly(methyl methacyrlate) colloids with the non-adsorbing depletant polystyrene added at a size ratio of depletant to colloid of 0.043. As the strength of the short-range attractive interaction is increased, clusters become increasingly structurally heterogeneous, as characterized by number-density fluctuations, and dynamically immobilized, as characterized by the single-particle mean-squared displacement. The number of free colloids in the suspension also progressively declines. As an immobile cluster to gel transition is traversed, structural heterogeneity abruptly decreases. Simultaneously, the mean single-particle dynamics saturates at a localization length on the order of the short-range attractive potential range. Both immobile cluster and gel regimes show dynamical heterogeneity. Non-Gaussian distributions of single particle displacements reveal enhanced populations of dynamical trajectories localized on two different length scales. Similar dependencies of number density fluctuations, free particle number and dynamical length scales on the order of the range of short-range attraction suggests a collective structural origin of dynamic heterogeneity in colloidal gels.Comment: 14 pages, 10 figure

Lean premixed combustion stabilized by radiation feedback and heterogeneous catalysis

Gas-turbine based systems are becoming the preferred approach to electric power generation from gaseous and liquid fossil-fuels and from biomass. As coal gasification becomes more prevalent, gas turbines will also become important in the generation of electricity from coal. In smaller, distributed installations, gas turbines offer the prospect of cogeneration of electricity and heat, with increased efficiency and reduced pollutant emissions. One of the most important problems facing combustion-based power generation is the control of air pollutants, primarily nitrogen oxides and carbon monoxide. Catalytic combustion over noble-metal catalysts offers a method for controlling NO{sub x} emissions. This report describes tests on a gas-fired catalytic combustor and the development of a mathematical model to describe the process. The authors anticipate that the models they develop under this research program will be useful by industry and researchers alike in the design of both experiments and practical gas turbine catalytic combustors. The model--which includes transport codes, mechanisms, and postprocessing routines--is portable and can be run on UNIX workstations. Intelligent design of experiments, guided by this model, can reduce unnecessary expenditures of time and money spent in the laboratory. Likewise, the development of low-NO{sub x} gas turbine systems can be accelerated by using these models to test the effectiveness of combustor designs prior to engaging in time-consuming prototyping

Fuel-Air Mixing In A Turbulent Coannular Pipe Flow Measured Using Laser Absorption With Genetic Algorithm-Based Tomographic Reconstruction And Modeled With LES

This research aims at improving the knowledge base of fuel-air mixing through measurements and modeling. The measurements are from an improved tomographic reconstruction method that is relatively easy to accomplish. A novel aspect of this research is the use of tomography for generating the RMS of fuel concentration. Measurements of fuel concentration for a mixing field were tomographically reconstructed from time resolved line of sight laser absorption measurements. The modeling is done using large eddy simulations (LES). LES predictions were compared to measurements of the mean and RMS of fuel concentration. The LES model predicted time-averaged radial fuel concentration profiles to within 5%, and overpredicted the RMS of fuel concentration slightly, predicting the trends correctly

A Numerical Investigation into the Anomalous Slight NOx Increase When Burning Biodiesel; A New (Old

Biodiesel is a notable alternative to petroleum derived diesel fuel because it comes from natural domestic sources and thus reduces dependence on diminishing petroleum fuel from foreign sources, it likely lowers lifecycle greenhouse gas emissions, and it lowers an engine’s emission of most pollutants as compared to petroleum derived diesel. However, the use of biodiesel often slightly increases a diesel engine’s emission of smog forming nitrogen oxides (NOx) relative to petroleum diesel. In this paper, previously proposed theories for this slight NOx increase are reviewed, including theories based on biodiesel’s cetane number, which leads to differing amounts of charge preheating, and theories based on the fuel’s bulk modulus, which affects injection timing. This paper proposes an additional theory for the slight NOx increase of biodiesel. Biodiesel typically contains more double bonded molecules than petroleum derived diesel. These double bonded molecules have a slightly higher adiabatic flame temperature, which leads to the increase in NOx production for biodiesel. Our theory was verified using numerical simulations to show a NOx increase, due to the double bonded molecules, that is consistent with observation. Further, the details of these numerical simulations show that NOx is predominantly due to the Zeldovich mechanism

Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point Site 5-6, South Africa

There are multiple hypotheses for human responses to glacial cycling in the Late Pleistocene, including changes in population size, interconnectedness, and mobility. Lithic technological analysis informs us of human responses to environmental change because lithic assemblage characteristics are a reflection of raw material transport, reduction, and discard behaviors that depend on hunter-gatherer social and economic decisions. Pinnacle Point Site 5-6 (PP5-6), Western Cape, South Africa is an ideal locality for examining the influence of glacial cycling on early modern human behaviors because it preserves a long sequence spanning marine isotope stages (MIS) 5, 4, and 3 and is associated with robust records of paleoenvironmental change. The analysis presented here addresses the question, what, if any, lithic assemblage traits at PP5-6 represent changing behavioral responses to the MIS 5-4-3 interglacial-glacial cycle? It statistically evaluates changes in 93 traits with no a priori assumptions about which traits may significantly associate with MIS. In contrast to other studies that claim that there is little relationship between broad-scale patterns of climate change and lithic technology, we identified the following characteristics that are associated with MIS 4: increased use of quartz, increased evidence for outcrop sources of quartzite and silcrete, increased evidence for earlier stages of reduction in silcrete, evidence for increased flaking efficiency in all raw material types, and changes in tool types and function for silcrete. Based on these results, we suggest that foragers responded to MIS 4 glacial environmental conditions at PP5-6 with increased population or group sizes, 'place provisioning', longer and/or more intense site occupations, and decreased residential mobility. Several other traits, including silcrete frequency, do not exhibit an association with MIS. Backed pieces, once they appear in the PP5-6 record during MIS 4, persist through MIS 3. Changing paleoenvironments explain some, but not all temporal technological variability at PP5-6.Social Science and Humanities Research Council of Canada; NORAM; American-Scandinavian Foundation; Fundacao para a Ciencia e Tecnologia [SFRH/BPD/73598/2010]; IGERT [DGE 0801634]; Hyde Family Foundations; Institute of Human Origins; National Science Foundation [BCS-9912465, BCS-0130713, BCS-0524087, BCS-1138073]; John Templeton Foundation to the Institute of Human Origins at Arizona State Universit