Port Diameter Research Articles

Burning Parameters of Premixed Oxygen-Hydrogen and Oxygen-Acetylene Flames

Parameters affecting the stability of premixed oxyhydrogen and oxyacetylene flames are investigated. The results of this study show the effect of port diameter, fuel-oxidant ratio, total gas flow, and burner temperature on the stability of these flames. Data were obtained by the use of a specially designed and constructed one-hole insert burner. The results of this study provide the required design criteria and operational parameters for utilization of these fuel mixtures.

Starting Transient of Solid-Propellant ocket Motors with High Internal Gas Velocities

A comprehensive analytical model which considers time and space development of the flow field in solid propellant rocket motors with high volumetric loading density is described. The gas dynamics in the motor chamber is governed by a set of hyperbolic partial differential equations, that are coupled with the ignition and flame spreading events, and with the axial variation of mass addition. The flame spreading rate is calculated by successive heating-to-ignition along the propellant surface. Experimental diagnostic studies have been performed with a rectangular window motor (50 cm grain length, 5 cm burning perimeter and 1 cm hydraulic port diameter), using a controllable head-end gaseous igniter. Tests were conducted with AP composite propellant at port-to-throat area ratios of 2.0, 1.5, 1.2, and 1.06, and head-end pressures from 35 to 70 atm. Calculated pressure transients and flame spreading rates are in very good agreement with those measured in the experimental system.

Burner Design Criteria and Variables Affecting Flashback of Acetylene Flames

A study is presented on the operating characteristics of burners employing premixed, laminar flow air–acetylene and nitrous oxide–acetylene flames. The variables affecting flashback of these flames have been investigated and found to be critically dependent on such factors as burner port diameter, gas flow, fuel–oxidant ratio, and burner construction. Because the theory previously developed for stable flame formation on isothermal burners is not directly applicable to most burners used in flame spectrometry, an operational theory of flashback is developed. In accordance with this working model, safe limits of operation for conventional burners are examined and presented and important burner design criteria are established, including experimental quenching diameters for both circular port and slot-type burners.

Optical measurements of mass density in a high- speed, confined, gaseous vortex

An optical method based on light-deflection mapping has been developed and used to determine the radial variation of fluid density in a high-pressure ratio, high-speed, air vortex that was generated in a 3-in.-diam, 18-in.-long swirl chamber consisting of two symmetric halves. An intense, parallel, thin light beam was transmitted laterally through the vortex at various off-axis positions, and the small light deflections caused by the density field of the vortex were measured. From the variation of the deflection angle over the radius, the radial density profile was numerically calculated by assuming rotational symmetry and solving the resulting integral equation. The density profile of the vortex was determined in two cross sections, at various operating conditions of the chamber. The results show that the core region in which the fluid rotates like a solid body has a very uniform diameter corresponding to about half of the exhaust port diameter. The presence of slight axial density differences, which are related to the meridional flow movements, is clearly shown. The lowest density is found to occur at the vortex axis in the central portion of the chamber. From the density profiles and suitably corrected pressure profiles measured with probes, static temperature profiles were calculated; the temperature exhibits a very low minimum near the outer limit of the solid-body-type core. The fluctuations of the light-beam deflection angle shed some light on the nature of transient phenomena occurring in the vortex. In addition to acoustic resonance, considerable irregular density fluctuations were observed, especially at radii smaller than that of the exhaust opening. This is believed to be because of the existence of periodic fluctuations in the rotational speed of the vortex.

Mixing and combustion in turbulent gas jets

Visible flame lengths and concentration patternshave been obtained in turbulent jets of flame formed by combustible gas issuing from circular nozzles into stagnant air. The nozzle velocities were above those which, in a previous paper, were found necessary to insure that the mixing should be turbulent. As a basis for analysis of the data a simplified treatment is presented for mixing of nozzle and ambient fluids in a vertical jet. The simplifying assumption of constant velocity and composition in a cross-section normal to the axis of flow is combined with a force-momentum balance, continuity, and the perfect gas laws to obtain a relation between mean concentration and jet spread. The relation allows for initial difference in density of nozzle and ambient streams, density variation due to combustion, and buoyancy. The qualitative agreement between the analysis and the experimental data on visible flame lengths and axial concentration patterns indicates plainly that the process of mixing resulting from the momentum and buoyancy of the jet is the controlling factor in determining progress of the combustion. For tree flames in which the effects of buoyancy are small (high nozzle velocity, small diameter) the analysis leads to the following simple relation for the length of free turbulent flame jets:L/D=5.3CτTFαTTN[Cτ+(1−Cτ)MSMN]where L=visible flame length D=nozzle diameter TF=adiabatic flame temperature, absolute TN=absolute temperature of nozzle fluid MS, MN=molecular weights of surrounding and nozzle fluids, respectively CT=mol fraction of nozzle fluid in the unreacted stoichiometric mixture αT=mols of reactants/mols products, for the stoichiometric mixture. It is to be noted that fuel gas flow rate is no factor, as long as it is great enough to prodace a turbulent jet. Although data for testing this relation covered the small range of port diameter of 0.12 to 0.30 inches, a wide variety of fuels was studied, including propane, acetylene, hydrogen, carbon monoxide, city gas, mixtures of carbon dioxide with city gas, and mixtures of hydrogen with propane. Turbulent flame lengths varying from 40 to 290 nozzle diameters are predicted with average and