Browsing by Subject "Chemical Kinetics"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    An Experimental Study into the Ignition of Methane and Ethane Blends in a New Shock-tube Facility
    (2011-02-22) Aul, Christopher Joseph Erik
    A new shock tube targeting low temperature, high pressure, and long test times was designed and installed at the Turbomachinery Laboratory in December of 2008. The single-pulse shock tube uses either lexan diaphragms or die-scored aluminum disks of up to 4 mm in thickness. The modular design of the tube allows for optimum operation over a large range of thermodynamic conditions from 1 to 100 atm and between 600-4000 K behind the reflected shock wave. The new facility allows for ignition delay time, chemical kinetics, high-temperature spectroscopy, vaporization, atomization, and solid particulate experiments. An example series of ignition delay time experiments was made on mixtures of CH4/C2H6/O2/Ar at pressures from 1 to 30.7 atm, intermediate temperatures from 1082 to 2248 K, varying dilutions (between 75 and 98% diluent), and equivalence ratios ranging from fuel lean (0.5) to fuel rich (2.0) in this new facility. The percentage by volume variation and equivalence ratios for the mixtures studied were chosen to cover a wide parameter space not previously well studied. Results are then used to validate and improve a detailed kinetics mechanism which models the oxidation and ignition of methane and other higher order hydrocarbons, through C4, with interest in further developing reactions important to methane- and ethane-related chemistry.
  • No Thumbnail Available
    Item
    Evolution equations in physical chemistry
    (2009-05) Michoski, Craig E.; Vasseur, Alexis F.; Stanton, John (John F.); Gamba, Irene M.; Wyatt, Robert E.; Souganidis, Panagiotis E.; Henkelman, Graeme
    We analyze a number of systems of evolution equations that arise in the study of physical chemistry. First we discuss the well-posedness of a system of mixing compressible barotropic multicomponent flows. We discuss the regularity of these variational solutions, their existence and uniqueness, and we analyze the emergence of a novel type of entropy that is derived for the system of equations. Next we present a numerical scheme, in the form of a discontinuous Galerkin (DG) finite element method, to model this compressible barotropic multifluid. We find that the DG method provides stable and accurate solutions to our system, and that further, these solutions are energy consistent; which is to say that they satisfy the classical entropy of the system in addition to an additional integral inequality. We discuss the initial-boundary problem and the existence of weak entropy at the boundaries. Next we extend these results to include more complicated transport properties (i.e. mass diffusion), where exotic acoustic and chemical inlets are explicitly shown. We continue by developing a mixed method discontinuous Galerkin finite element method to model quantum hydrodynamic fluids, which emerge in the study of chemical and molecular dynamics. These solutions are solved in the conservation form, or Eulerian frame, and show a notable scale invariance which makes them particularly attractive for high dimensional calculations. Finally we implement a wide class of chemical reactors using an adapted discontinuous Galerkin finite element scheme, where reaction terms are analytically integrated locally in time. We show that these solutions, both in stationary and in flow reactors, show remarkable stability, accuracy and consistency.
  • No Thumbnail Available
    Item
    OH* Chemiluminescence: Pressure Dependence of O + H + M = OH* + M
    (2011-02-22) Donato, Nicole
    The measure of chemiluminescence from the transition of the hydroxyl radical from its electronically excited state (A^2 Sigma^positive) to its ground state (X^2 Pi) is used in many combustion applications for diagnostic purposes due to the non-intrusive nature of the chemiluminescence measurement. The presence of the ultraviolet emission at 307nm is often used as an indicator of the flame zone in practical combustion systems, and its intensity may be correlated to the temperature distribution or other parameters of interest. To date, the measurement of the excited state OH, OH*, is mostly qualitative. With the use of an accurate chemical kinetics model, however, it is possible to obtain quantitative measurements. Shock-tube experiments have been performed in highly diluted mixtures of H2/O2/Ar at a wide range of pressures to evaluate the pressure-dependent rate coefficient of the title reaction. In such mixtures the main contributing reaction to the formation of OH* is, O H M = OH* M. R1 Previous work has determined the reaction rate of R1 at atmospheric conditions and accurately predicts the amount of OH* experimentally produced. At elevated pressures up to 15 atm, which are of interest to the gas turbine community, the currently used reaction rate of R1 (i.e., without any pressure dependence) significantly over predicts the amount of OH* formed. This work provides the pressure dependence of R1. The new reaction rate is able to reproduce the experimental data over the range of conditions studied and enables quantitative measurements applicable to practical combustion environments.