Showing papers by "Iran University of Science and Technology published in 1993"

Far infrared spectrum of CD3OH methanol from 40–220 CM−1

Abstract: The Fourier transform far-infrared (FTFIR) spectrum of CD3OH has been obtained from 40–220 cm−1 at a resolution of 0.002 cm−1, and partially analyzed. Numerousb-type branches have been assigned in the spectrum, ranging over torsional states fromn=0 to 3. The branches have been fitted toJ(J+1) power-series energy expansions in order to obtainJ-independent branch origins. These in turn have been fitted to the torsion-rotation Hamiltonian, and improved molecular constants have been obtained for the ground vibrational state.

Stress and strain range predictions for axisymmetric and two-dimensional components with stress concentrations and comparisons with notch stress-strain conversion rule estimates

Abstract: A comparison is made between finite element predictions of strain and strain range for hollow tubes with axially loaded axisymmetric internal projections and values obtained from the simple notch stress-strain conversin (NSSC) rules. Data from other published analyses, where notch strains were predicted, support this investigation. The comparison is made for a variety of monotonic and cyclic loads, material hardenning assumptions, and geometries. An intermediate rule (m = 0.5) which appears to correlate with the finite element predictions to a reasonable degree of accuracy, is identified. In addition, an analytical relationship is suggested for calculating strain and strain range, in terms of load level, strain hardening assumption, and elastic stress concentration factor (SCF) for this type of axisymmetric component. Also, a comparison is made between some previously published experimental and numerical data, obtained for other two-dimensional and axisymmetric problems, and NSSC rule estimates in...

Microwave spectra of cd3oh methanol

Abstract: The microwave spectrum of CD3OH has been studied over the 8 to 58 GHz region, and numerousb-type transitions have been assigned. Many of these belong toP subbranches which descend to the microwave region from subband origins lying much higher in the far-infrared, pass through zero frequency, and return upward again. Others are members ofb-typeQ branches which extend across the region. As well, variousa-typeK-doublet lines arising as transitions directly across the split levels of asymmetry doublets have been identified.

Elastic-plastic finite element analysis of hollow tubes with axially loaded axisymmetric internal projections

Abstract: The finite element method is used to study the monotonic and cyclic elastic-plastic stress and strain characteristics of hollow tubes with axisymmetric internal projections subjected to monotonic and repeated axial loading. Two geometries having low and high elastic stress concentration factors are considered in this investigation, and the results are complementary to previously published data. For cyclic loading, three simple material behaviour models, e.g., elastic-perfectly-plastic, isotropic hardening, and kinematic hardening are assumed. All results have been normalized with respect to material properties so that they can be applied to all geometrically similar components from other materials which may be represented by the same material models. Finally, normalized maximum monotonic strain and steady state strain range, predicted in the present investigation and from previously published data, are plotted as a function of the nominal load for different material hardening assumptions and diffe...

Species Concentrations in a Model Gas Turbine Combustor

Abstract: To investigate the combustion characteristics of hollow-cone spray flames somewhat similar to those occurring in the primary zone of gas turbine combustion chambers or within oil burners, a swirl-stabilized combustor was designed. The combustor is circular in cross section, with a swirl plate and fuel nozzle axis coinciding with the axes of the combustor. Separate swirl and dilution air flows are distributed into the combustor that pass through honeycomb flow straighteners and screens. A kerosene spray was generated by a simplex atomizer with a nominal initial-spray-angle of 30 degrees. Swirling air with swirl number of 1.5 was produced from a swirl plate. A Phase Doppler Particle Analyzer (PDPA) was used to measure the drop size, mean and rms values of axial drop velocity with and without combustion. Air and fuel flow rates and other conditions were kept identical for reacting and non-reacting cases to investigate effects of combustion alone on the spray. A thermocouple was used to measure the average uncorrected temperature in this turbulent spray flame. A water-cooled stainless-steel gas sampling probe was designed to be used with a gas chromatograph (GC) to measure the gaseous species concentrations in this combustor.Results for mean axial drop velocity profiles indicate widening of the spray, with slight increase in the magnitudes of the peak drop velocities due to combustion. No measurements of this type are possible inside the hollow-cone spray due to burning of fuel droplets within the flame zone. Root-Mean-Square (RMS) values of drop velocity fluctuations decrease due to combination of increase in gas kinematic viscosity and elimination of small drops at high temperatures. Sauter Mean Diameter (SMD) radial profiles at all axial locations increase with combustion as compared to the no-combustion case due to preferential burning of small drops. At the initial stages of combustion near the atomizer, the gas species concentration changes due to droplet evaporation, decomposition of fuel, reaction, and mixing with extra air. At the end of the visible flame zone, away from the nozzle, no significant amounts of methane and hydrogen have been observed. The gas concentration profiles at this axial position are flat within the burned gas zone. The species concentration profiles measured in the burned gas zone near the nozzle and along the spray centerline axis are similar to those of turbulent gaseous-fuel diffusion flame.Copyright © 1993 by ASME

Notch strain calculations for axisymmetric problems based on a local strain approach

Abstract: Introduction Previously published results for axisymmetric components with moderate to high elastic stress concentration factors, i.e., hollow tubes with axially loaded axisymmetric internal projections (1)-(3)t suggest that the monotonic notch strain and the cyclic notch strain range can be estimated using an intermediate notch stress-strain conversion (NSSC) rule with the index m set to 0.5. In this paper, a simple method for estimating these strain and strain range values, based on a knowledge of the elastic stress concentration factor, loading and material properties, is presented.