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Compression ratio effect on methane HCCI combustion

Description: We have used the HCT (Hydrodynamics, Chemistry and Transport) chemical kinetics code to simulate HCCI (homogeneous charge compression ignition) combustion of methane-air mixtures. HCT is applied to explore the ignition timing, bum duration, NO<sub>x</sub> production, gross indicated efficiency and gross IMEP of a supercharged engine (3 atm. Intake pressure) with 14:1, 16:l and 18:1 compression ratios at 1200 rpm. HCT has been modified to incorporate the effect of heat transfer and to calculate the temperature that results from mixing the recycled exhaust with the fresh mixture. This study uses a single control volume reaction zone that varies as a function of crank angle. The ignition process is controlled by adjusting the intake equivalence ratio and the residual gas trapping (RGT). RGT is internal exhaust gas recirculation which recycles both thermal energy and combustion product species. Adjustment of equivalence ratio and RGT is accomplished by varying the timing of the exhaust valve closure in either 2-stroke or 4-stroke engines. Inlet manifold temperature is held constant at 300 K. Results show that, for each compression ratio, there is a range of operational conditions that show promise of achieving the control necessary to vary power output while keeping indicated efficiency above 50% and NO<sub>x</sub> levels below 100 ppm. HCT results are also compared with a set of recent experimental data for natural gas.
Date: September 29, 1998
Creator: Aceves, S. M.; Pitz, W.; Smith, J. R. & Westbrook, C.
Partner: UNT Libraries Government Documents Department

Pathway and kinetic analysis on the iso-propyl radical + O{sub 2} reaction system

Description: We analyze the isopropyl + 02 reaction system using thermochemical Transition State Theory (TST), molecular thermodynamic properties, analysis (quantum RRK) for k(E) and modified strong collision analyze Cyclic transition states for both hydrogen transfer and concerted propylene from isopropylperoxy are calculated using semi-empirical theory in addition to transition states for H02 elimination from hydroperoxy-isopropyl. Computed rate constants are compared to constant measurements of for isopropyl + H02.
Date: April 7, 1997
Creator: Bozzelli, J. W. & Pitz, W. J.
Partner: UNT Libraries Government Documents Department

Ultrafast studies of solution dynamics

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Fast chemical dynamics generally must be initiated photochemically. This limits the applicability of modern laser methods for following the structural changes that occur during chemical and biological reactions to those systems that have an electronic chromophore that has a significant yield of photoproduct when excited. This project has developed a new and entirely general approach to ultrafast initiation of reactions in solution: laser-induced temperature jump (T-jump). The results open entire new fields of study of ultrafast molecular dynamics in solution. The authors have demonstrated the T-jump technique on time scales of 50 ps and longer, and have applied it to study of the fast events in protein folding. They find that a general lifetime of alpha-helix formation is ca 100 ns, and that tertiary folds (in apomyoglobin) form in ca 100 {mu}s.
Date: October 1, 1997
Creator: Woodruff, W.H.; Dyer, R.B. & Callender, R.H.
Partner: UNT Libraries Government Documents Department


Description: The basic information about the path of carbon in photosynthesis is reviewed together with the methods that were used to discover it. This has led to the knowledge of what is required of the photochemical reaction in the form of chemical species. Attention is then directed to the structure of the photochemical apparatus itself insofar as it is viewable by electron microscopy, and some principoles of ordered structure are devised for the types of molecules to be found in the chloroplasts. From the combination of these, a structure for the grana lamella is suggested and a mode of function proposed. Experimental test for this mode of function is underway; one method is to examine photoproduced unpaired electrons. This is discussed.
Date: September 23, 1958
Creator: Calvin, Melvin
Partner: UNT Libraries Government Documents Department

A Survey of the Rates and Products of Short-Term Photosynthesis inPlants of 9 Phyla

Description: The conclusions of this paper are: (1) Short-term photosynthetic experiments using C{sup 14}O{sub 2} and paper chromatography were performed with 27 different plants representing nine phyla: Schizophyta (Schizophyceae), Euglenophyta, Chlorophyta, Charophyta, Chrysophyta, Rhodophyta, Bryophyta, Pteridophyta, and Spermatophyta. (2) There is a remarkable uniformity in the types of ethanol-soluble compounds which became radioactive in the entire group of plants used. The amounts of the different compounds varied considerably percentage-wise among the various plants as would be expected because of their inherent metabolic differences and the variations in their physiological states induced by experimental conditions. (3) Sucrose became radioactive in very different amounts in two major groupings of plants: (a) those containing only photosynthetic tissue and (b) those containing non-photosynthetic tissue as well. The amount of radioactive sucrose in the former group was much lower than that in the latter. (4) An unidentified compound became radioactive in appreciable amounts in two of the blue-green algae, but was radioactive in very small amounts or not visible at all on the chromatograms of all other plants.
Date: May 1, 1954
Creator: Calvin, M.; Norris, R.E. & Norris, Louisa
Partner: UNT Libraries Government Documents Department

The Path of Carbon in Photosynthesis VI.

Description: This paper is a compilation of the essential results of our experimental work in the determination of the path of carbon in photosynthesis. There are discussions of the dark fixation of photosynthesis and methods of separation and identification including paper chromatography and radioautography. The definition of the path of carbon in photosynthesis by the distribution of radioactivity Within the compounds is described.
Date: June 30, 1949
Creator: Calvin, M.
Partner: UNT Libraries Government Documents Department


Description: In its usual form activated complex theory assumes a quasi-equilibrium between reactants and activated complex, a separable reaction coordinate, a Cartesian reaction coordinate, and an absence of interaction of rotation with internal motion in the complex. In the present paper a rate expression is derived without introducing the Cartesian assumption. The expression bears a formal resemblance to the usual one and reduces to it when the added assumptions of the latter are introduced. The new equation for the transmission coefficient contains internal centrifugal terms. The derivation employs an extension of the Stackel-Robertson formalism for separation of variables in mechanics. The fourth assumption can also be weakened and a rotational interaction included in the formalism. In applications of the rate equation use is made of the recent findings that in the immediate vicinity of a saddle-point or a minimum a potential energy surface can be imitated in some major topographical respects by a surface permitting separation of variables. The separated wave equation for the reaction coordinate is then curvilinear because of the usual curvature of the path of steepest ascent to the saddle-point. Calculations of transmission coefficients and rates can be made and compared with those obtainable from the usual one-dimensional Cartesian-like calculations on the one hand and with some based on the numerical integration of the n-dimensional Schrodinger equation on the other. An application to a common three-center problem is discussed.
Date: November 1, 1964
Creator: Marcus, R.A.
Partner: UNT Libraries Government Documents Department

Activity Coefficient Derivatives of Ternary Systems Based on Scatchard's Neutral Electrolyte description

Description: Activity coefficient derivatives with respect to molality are presented for the Scatchard Neutral Electrolyte description of a ternary common-ion electrolyte system. These quantities are needed for the calculation of 'diffusion Onsager coefficients' and in turn for tests of the Onsager Reciprocal Relations in diffusion. The usually-omitted b{sub 23} term is included. The direct SNE binary approximations and a further approximation are discussed. Binary evaluation strategies other than constant ionic strength are considered.
Date: May 16, 2007
Creator: Miller, D G
Partner: UNT Libraries Government Documents Department


Description: Lecture presented at the Atomic Industrial Forum's Third Course on Reactor Materials, Stanford University, Stanford, California, July 9-19, 1957A review of progress in the use of liquid metals is presented. A number of liquid metals are compared, and the general problems of selecting container materials are considered. In addition. a discussion of corrosion mechanisms and corrosion testing methods commonly employed are examined as well as problems encountered with the liquid metals of greatest interest. (J.R.D.)
Date: October 28, 1957
Creator: Holman, W.
Partner: UNT Libraries Government Documents Department

Data Assimilation Tools for CO2 Reservoir Model Development – A Review of Key Data Types, Analyses, and Selected Software

Description: Pacific Northwest National Laboratory (PNNL) has embarked on an initiative to develop world-class capabilities for performing experimental and computational analyses associated with geologic sequestration of carbon dioxide. The ultimate goal of this initiative is to provide science-based solutions for helping to mitigate the adverse effects of greenhouse gas emissions. This Laboratory-Directed Research and Development (LDRD) initiative currently has two primary focus areas—advanced experimental methods and computational analysis. The experimental methods focus area involves the development of new experimental capabilities, supported in part by the U.S. Department of Energy’s (DOE) Environmental Molecular Science Laboratory (EMSL) housed at PNNL, for quantifying mineral reaction kinetics with CO2 under high temperature and pressure (supercritical) conditions. The computational analysis focus area involves numerical simulation of coupled, multi-scale processes associated with CO2 sequestration in geologic media, and the development of software to facilitate building and parameterizing conceptual and numerical models of subsurface reservoirs that represent geologic repositories for injected CO2. This report describes work in support of the computational analysis focus area. The computational analysis focus area currently consists of several collaborative research projects. These are all geared towards the development and application of conceptual and numerical models for geologic sequestration of CO2. The software being developed for this focus area is referred to as the Geologic Sequestration Software Suite or GS3. A wiki-based software framework is being developed to support GS3. This report summarizes work performed in FY09 on one of the LDRD projects in the computational analysis focus area. The title of this project is Data Assimilation Tools for CO2 Reservoir Model Development. Some key objectives of this project in FY09 were to assess the current state-of-the-art in reservoir model development, the data types and analyses that need to be performed in order to develop and parameterize credible and robust reservoir simulation models, and ...
Date: September 30, 2009
Creator: Rockhold, Mark L.; Sullivan, E. C.; Murray, Christopher J.; Last, George V. & Black, Gary D.
Partner: UNT Libraries Government Documents Department


Description: A small, laboratory-sized loop was designed for steady-state radiolytic gas recombination studies. It consists of an electrolysis cell, which simulates the radiolytic gas formed in a reactor, and a bomb for containing slurry under test. The electrolysis capacity of the system is adequate for the study of slurries having recombination rates as high as 10 moles/hr/liter of slurry at the proposed slurry reactor operating conditions. (auth)
Date: September 18, 1958
Creator: Culver, R.S.
Partner: UNT Libraries Government Documents Department

Gaseous Reduction of an Alloy Oxide

Description: Ni(Al, Fe){sub 2}O{sub 4} ceramic alloys were reduced by hydrogen gas at a pressure of 1 atm, and at temperatures between 450 and 800 C. The reaction rate was determined from the rate of advance of the porous metal product layer-unreduced oxide interface. A simple analysis was presented permitting assessment of both the interface reaction resistance and the gas transport resistant through the porous product scales. The reaction was under mixed control in all conditions studied. In a range of temperatures and reaction times, preferred grain-boundary attack was observed. The conditions under which this was observed depended strongly on the Al{sup 3+} content of the ceramic alloy. Al{sup 3+} also lowered the interface reaction rate and inhibited scale coarsening by formation of dispersed unreduced phases in the product scales.
Date: September 1, 1980
Creator: Allender, Jeffrey S. & DeJonghe, Lutgard C.
Partner: UNT Libraries Government Documents Department

Chemical reaction rates using the semiclassical Van-Vleck initialvalue representation

Description: A semiclassical IVR formulation using the Van-Vleck propagator has been used to calculate the flux correlation function and thereby reaction rate constants. This Van-Vleck formulation of the flux-flux correlation function is computationally as simple as the classical Wigner model. However unlike the latter, it has the ability to capture quantum interference/coherence effects. Classical trajectories are evolved starting from the dividing surface that separates reactants and products, and are evolved negatively in time. This formulation has been tested on model problems ranging from the Eckart barrier, double well to the collinear H + H{sub 2}.
Date: November 29, 2006
Creator: Venkataraman, Charulatha & Miller, William H.
Partner: UNT Libraries Government Documents Department

Wide range modeling study of dimethyl ether oxidation

Description: A detailed chemical kinetic model has been used to study dimethyl ether (DME) oxidation over a wide range of conditions. Experimental results obtained in a jet-stirred reactor (JSR) at I and 10 atm, 0.2 < 0 < 2.5, and 800 < T < 1300 K were modeled, in addition to those generated in a shock tube at 13 and 40 bar, 0 = 1.0 and 650 :5 T :5 1300 K. The JSR results are particularly valuable as they include concentration profiles of reactants, intermediates and products pertinent to the oxidation of DME. These data test the Idnetic model severely, as it must be able to predict the correct distribution and concentrations of intermediate and final products formed in the oxidation process. Additionally, the shock tube results are very useful, as they were taken at low temperatures and at high pressures, and thus undergo negative temperature dependence (NTC) behavior. This behavior is characteristic of the oxidation of saturated hydrocarbon fuels, (e.g. the primary reference fuels, n-heptane and iso- octane) under similar conditions. The numerical model consists of 78 chemical species and 336 chemical reactions. The thermodynamic properties of unknown species pertaining to DME oxidation were calculated using THERM.
Date: April 1, 1997
Creator: Pitz, W.J.; Marinov, N.M.; Westbrook, C.K.; Dagaut, P.; Boettner, J-C & Cathonnet, M.
Partner: UNT Libraries Government Documents Department

Free-radical kinetics of coal liquefaction

Description: A rate expression with first- and second-order terms in the concentration of extractable compounds in solid coal particles is derived from a fundamental free-radical mechanism. The expression was suggested empirically by prior experiments for coal liquefaction in the presence of a hydrogen-donor solvent. Radical reactions are considered to occur in both coal and in solvent. The long-chain approximation justifies the neglect of initiation, hydrogen abstraction, and termination rates as quantitatively insignificant relative to propagation reaction rates.
Date: July 16, 1994
Creator: Wang, M.; Smith, J.M. & McCoy, B.J.
Partner: UNT Libraries Government Documents Department

Beyond transition state theory: Rigorous quantum approaches for determining chemical reaction rates

Description: Transition state theory (TST) has historically been the most important and widely used theoretical approach for describing the rates of chemical reactions, and for qualitative pictures and order-of-magnitude estimates one does not expect this situation to change. However a rigorous, quantitative treatment of chemical reaction rates must go beyond TST. A rigorous description, for example, must be based on a quantum mechanical description of the molecular system, but the fundamental assumption on which TST is based - namely that the molecular dynamics is {open_quotes}direct,{close_quotes} i.e., that no trajectories re-cross a dividing surface which separates reactants and products (vide infra) - is couched inherently in the language of classical mechanics. There is no unambiguous way to quantize TST, for the various ways of trying to do so invariably require one to introduce additional assumptions about the reaction dynamics. As one tries to eliminate these {open_quotes}additional assumptions{close_quotes} one is driven ultimately to an exact quantum treatment of the reaction dynamics which is then no longer a transition state theory (i.e., approximation) but simply an exact formulation. It is such exact approaches, those without inherent approximations, that are the subject of this chapter.
Date: January 1, 1995
Creator: Miller, W.H.
Partner: UNT Libraries Government Documents Department