Reduction In Jet Velocity Research Articles

Numerical Simulation of CO2 Used for Slag Splashing Process in Converter

Utilizing CO2 for the slag splashing process presents a novel approach that enhances CO2 utilization in the steel industry and promotes efficient slag splashing. Herein, numerical simulation is employed to investigate the kinetic feasibility of this technique on a 100 t converter. The volume of fluid (VOF) model is utilized to trace the gas–slag interface, while the standard k–ε model is selected to describe the turbulent flow of each phase. Initially, the model is validated via isentropic theory and experimental data. Subsequently, the effects of gas and oxygen lance replacement are evaluated. The results indicate that employing CO2 solely instead of N2 leads to a reduction in jet velocity and slag mass flow rates at different positions. However, the utilization of the innovative oxygen lance slows down the jet decay and increases the slag mass flow rate at various heights and sidewalls, except for the lower cone, resulting in a satisfactory slag splashing performance. The present study verifies the feasibility of this new technology and its potential to contribute to CO2 reduction in the industry positively.

Characteristics of supersonic jets in LD steelmaking

In the Linz–Donawitz (LD) steelmaking process supersonic oxygen jets expand into the surroundings formed by hot and dense slag foam thus it is necessary to understand the innate characteristics of supersonic jets when expanding into such surroundings. In this study, the individual influences of both the elevated temperature and high density of the surrounding medium on the jet characteristics are presented. It was found that the supersonic jet characteristics were not affected significantly by the expansion into hot environments with no correlation between the Mach number profiles and changes in surrounding temperature. However, the influence of the dense surroundings on the jet characteristics was profound. The jet velocity was reduced when expanding into a dense medium in comparison with that expanding into a gaseous medium. The peak value of momentum at any cross-section of the jet was not at the axis but in the gas/dense medium interface. The confluence of these factors, i.e. severe reduction in jet velocity and the location of peak momentum within the jet, are expected to change the present understanding of flow dynamics within LD vessels and its influence on refining reactions. Further studies in this area are recommended for better understanding of these phenomena.

Suppression of Self-Excited Oscillatory Flow in Collapsible Tubes Effect of Rod Insertion.

An experimental study was conducted to suppress self-excited oscillation of collapsible tubes, where a steel rod was inserted from the downstream bend into a silicone rubber tube. It was found that rod insertion along the tube center was effective in suppressing self-excited oscillation and that insertion with offset from the center was ineffective in suppression. The principal effect of rod insertion is that the rod contacts the internal surface of the tube and prevents collapse when located at the tube center. This was clearly indicated in the measured tube law. Secondary effects are the release of negative pressure impulse and the reduction of jet velocity at the throat.

Species Concentration and Temperature Measurements in a Lean, Premixed Flow Stabilized by a Reverse Jet

The chemical and thermal structure and the emission performance of an aerodynamic flameholder are presented and examined. Recirculation is established by injecting a premixed jet into an opposing mainstream of premixed reactants. The injection of the jet directly into the recirculation zone provides a control of the stabilization zone mixture ratio, temperature, and size not found in bluffbody flameholding. The size and stoichiometry of the recirculation zone is dictated by the jet velocity and mixture ratio respectively. A parametric study of the controlling variables (main and jet stream velocities, main and jet stream equivalence ratios) reveals the partitioning between the recirculation zone and wake in both the heat release and pollutant production. An examination of the emission indexes and flowfield profiles of temperature and species concentration establishes the influence and control of jet and mainstream conditions on pollutant production. A reduction in jet velocity and/or an enrichment of the jet, for example, effects a substantial change in NO, emission. Further, jet enrichment extends the lean blow-off limit of the mainstream. There exists a point, however, beyond which the reaction is not supported in the wake and further leaning of the mainstream results in a substantial emission of unspent fuel. © 1982, Taylor & Francis Group, LLC. All rights reserved.

Month in the Patent Office

A helicopter rotor wherein each blade 3 carries a tip propulsion‐jet unit 4 has each unit constructed to reduce the velocity and noise level of the propulsive jets. Each unit 4 consists of an outer casing formed into a double wall at its forward end to provide an annular duct 12 which communicates through an aperture 20 with a conduit which extends through each blade from a gas producing plant 22, consisting of a gas turbine engine or engines or a separate compressor driven by such engine(s). Arms 10 secured radially on the forward end of the fairing support a central faired body 9 which is connected at its rear end to the fairing by stator blades 18 mounted ahead of a bladed rotor 5 secured in body 9 by a bearing 11. Blades 6 of rotor 5 carry a shroud ring formed on its periphery with turbine blades 8. Further stator blades 14, 15 connect the casing 4 to a tail fairing cone 16 and stator blades 13 bridge the duct 12. In operation gas flow from the blade conduit passes into duct 12 to be directed over blades 8 to drive rotor 5 which draws air through the unit to mix with the gases from gas producing plant 22 with a consequent reduction in jet velocity and noise. Any one of the rows of fan rotor and stator blades may be angularly adjustable to control the rotor speed. Alternatively, the turbine rotor blades 8 may be of the impulse type and a variable area admission nozzle used.

The Influence of the Exit Velocity Profile on the Noise of a Jet

SummaryThe noise levels of a jet issuing from a long pipe are compared with those of a jet having a square velocity profile at the exit. A subsonic noise reduction of between 2 and 5 decibels for various conditions is found for the case of the flow emerging with an approximately “turbulent pipe-flow” velocity profile for the same maximum jet velocity, but this is at the expense of a loss in thrust of a quarter. On comparison with a jet of smaller diameter which has an equal thrust for the same maximum jet velocity, it is found that the changes in noise level are rather smaller. For jets of equal diameters, the effects on the subsonic aerodynamic noise generated of a reduction of velocity gradient near the boundary are more than offset by the increased velocities necessary near the centre of the jet to obtain equal thrust. It is concluded that if the effect of differences in initial turbulence can be neglected the use of an auxiliary flow forming a comparatively thin sheath of slower moving fluid at the exit is not likely to result in large decreases in the subsonic noise level, and that a general reduction in jet velocity is more effective.Above the critical pressure larger reductions of up to 10 decibels are found. These are consistent with a delay of the onset of the self-maintained shock-produced noise.