Experimental study of the effects of secondary air on the emissions and stability of a lean premixed combustor

Tests were run using a perforated plate flameholder with a relatively short attached recirculation zone and a vee gutter flameholder with a relatively long attached recirculation zone. Combustor streamlines were traced in cold flow tests at ambient pressure. The amount of secondary air entrainment in the recirculation zones of the flameholders was determined by tracer gas testing at cold flow ambient pressure conditions. Combustion tests were caried out at entrance conditions of 0.5 MPa/630K and emission of NOx, CO and unburned hydrocarbons were measured along with lean stability and flashback limits. The degree of entrainment increases as dilution air injection decreases. Flashback appears to be a function of overall equivalence ratio and resistance to flashback increases with increasing combustor entrance velocity. Lean stability limit appears to be a function of both primary zone and flameholder recirculation zone equivalence ratios and resistance to lean blowout increases with increasing combustor entrance velocity

An investigation on molecular dynamics of binary mixtures of N-methylacetamide and tetramethylurea in microwave region

The dielectric relaxation times (τ)and the dipole moments (µ) of the binary mixtures of different molar concentrations of tetramethylurea (TMU) in the binary mixtures of N-methylacetamide (NMA) and tetramethylurea (TMU) in benzene solutions have been calculated by using standard standing wave microwave techniques and Gopala Krishna’s single frequency (9.90 GHz) concentration variational method at different temperatures (25 °C, 30 °C, 35 °C and 40 °C). The energy parameters (He, Fe, Se) for the dielectric relaxation process of binary mixtures containing 30% mole-fraction of TMU have been calculated at the respective given temperatures and the comparison has been made with the corresponding energy parameters (Hη, Fη, Sη) for the viscous flow. On the basis of the observations, it is found that the dielectric relaxation process can be treated as the rate process like the viscous flow process. The solute-solute and solute-solvent types of the molecular associations have been predicted

Colours of stratified media. I. Ancient decomposed glass

This article does not have an abstract

Haidinger's rings in curved plates

The paper describes and illustrates the haidinger interference patterns observed in curved plates of uniform thickness but of arbitrary form, and discusses their theory. Using an illuminated screen as light source and a limited viewing aperture, it is possible to observe such patterns with curved plates, their configuration depending upon the form of the plate as well as the position of the aperture with reference to the centers of curvature of the surface of the plate. It is pointed out that the interference pattern for a curved plate is geometrically similar in form to the image of the standard haidinger pattern of circular rings as seen viewed by reflection at the appropriate distance from the curved surface of the shell

The optics of mirages

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Dynamic Response Optimization of Piezoelectrically Excited Thin Resonant Beams

Piezoelectrically excited, resonant, elastic beams find wide use as piezoelectric fans, optical choppers, MEMS sensors, and piezoelectric motors. The devices consist of either one piezoelectric ceramic patch (piezopatch) bonded on one side (asymmetric configuration), or of two oppositely poled patches placed symmetrically on either side of a thin, flexible elastic beam (symmetric configuration). Field equations of the coupled structure governing the coupled longitudinal and bending motions of the resonator are derived using linear constitutive equations, slender beam approximations, and Hamilton’s principle. Analytical solutions are found to the coupled eigenvalue problem. Eigenvalues and eigenfunctions for the short-circuited and open-circuited configurations are predicted analytically and are found to be in excellent agreement with results from threedimensional finite element simulations. Electromechanical coupling factors (EMCF) are computed using the analytical and finite element model and optimal resonator geometries are identified for maximal EMCF. The EMCF predictions are also compared with experiments for an asymmetrically configured resonator. The analytical solution provides a convenient tool for the optimal design of such devices