Annular rings

There are various designs of flare tips that incorporate such features as central steam injection, an annular ring of steam nozzles, internal air-inspirating steam nozzles, windshields, etc. Table 2 provides some details of suitable types from which selection may be made. 

Annular Liquid flows in continuous annular ring on pipe W all, gas flows through center of pipe... 

There are four basic valve designs used in these compressors finger, channel, leaf, and annular ring. Within each class, there may be variations in design, depending upon operating speed and size of valve required. 

Annular ring over which energy balance is made. (From Transport Phenomena by R. B. Bird, W. E. Stewart, and E. N. Lightfoot. Copyright (c) 196Q. Reprinted with permission of John Wiley and Sons, Inc.)... 

H and the cylinder C an asbestos curtain A is hung from a plate of non-conducting material B. The lid of the tank, which is insulated from both H and C, has two flanges O and N which form an annular ring. It also has two outlet pipes G and F,... 

Pressure oscillations with RMS value up to 10 kPa in two models of lean-burn gas turbine combustors, with heat release around 100 kW, have been actively controlled by the oscillation of fuel flow. The flames were stabilized behind an annular ring and a step in one arrangement, and downstream of an expansion and aided by swirl in the other. Control was sensitive to the location of addition of oscillated fuel. Oscillations in the annular flow were attenuated by 12 dB for an overall equivalence ratio of 0.7 by the oscillation of fuel in the core flow and comprising 10% of the total fuel flow, but negligibly for equivalence ratios greater than 0.75. Oscillation of less than 4% of the total fuel in the annulus flow led to attenuation by 6 dB for all values of equivalence ratio considered. In the swirling flow, control was more effective with oscillations imposed on the flow of fuel in a central axial jet than in the main flow, and oscillations were ameliorated by 10 dB for equivalence ratio up to 0.75, above which the flame moved downstream so that the effectiveness of the actuator declined. The amelioration of pressure oscillations resulted in an increase in NOj, emissions by between 5% and 15%. 

Figure 19.1 Annular flow arrangement and devices to oscillate fuel flow AR — annular ring BS — backward-facing step FI — fuel injector ID — inner duct MD — main duct PT — pressure transducer SR — swirl register (all dimensions are in mm), (a) annular flow arrangement (6) needle valve arrangement to oscillate fuel flow 1 — vibrator, 2 — receiver, 3 — needle, 4 — spider (c) arrangement to deliver oscillated fuel to inner duct and (d) arrangement to oscillate fuel flow with three circumferentially equispaced injectors...

The second device comprised a set of three circumferentially located pintle-type injectors Keihin, 10450-PG7-0031) to inject fuel radially into the main duct of the first flow arrangement as near-rectangular pulses. The frequency and duration of fuel injection were software controlled, and the fuel flow from each injector was delivered close to the outer edge of the annular ring flame holder by a cross-jet of air (1.2 x 5 mm), directed along the duct axis with exit velocity up to 100 m/s. The amplitude of the oscillated input was limited by the volume injection rate of the injectors. Propane, rather than methane, provided up to 3.5 kW of the total heat release of around 100 kW. With fluid dynamic damping, the RMS of the oscillated fuel flow corresponded to a heat release of around 1.8 kW. 

Measurements were obtained with a ratio of flow rates (flow rate in the an-nulus/flow rate in the inner duct) of 9, so that the bulk mean velocities upstream of the annular ring were nearly equal to those in practical combustors. Deviations from this ratio were allowed where they provided insight into the nature of the oscillations. Results relating to the influence of the geometric and flow parameters on flame stabilization and combustion oscillations are presented first. 

Figure 19.3 Influence of equivalence ratio on antinodal RMS pressure fluctuation annular flow arrangement, bulk mean velocity in main flow, Um = 7-5 m/s bulk mean velocity in pilot stream. Up = 8 m/s Re j = UmD/v = 40,000, axial separation between annular ring and step, A = 0.513. 1 — 4 m = 0.62 2 — 0.70 3 — 0.76 dashed line corresponds to flame detachment...

Acoustic quarter-waves with an antinode at the upstream end of the combustor and RMS pressures up to 10 kPa have been shown to dominate the flows in the two combustors tested. The quarter-wave occupied the duct length upstream of the annular ring in the first arrangement and the entire duct length in the swirling flow. 

Pressure oscillations in the first arrangement depended on the equivalence ratio of the flow in the annulus and decreased with velocities in the pilot stream greater than that in the main flow due to decrease in size of the recirculation zone behind the annular ring and its deflection towards the wall. Increase in swirl number of the second arrangement caused the lean flammability limit to decrease, and the pressure oscillations to increase at smaller values of equivalence ratio. Unpremixedness associated with large fuel concentrations at the centre of the duct increased the pressure oscillations. Pressure oscillations caused the position of flame attachment to move downstream in both flows with a decrease in amplitude of oscillations. 

Although the oscillation of fuel in the annulus was limited by the actuator to 4% of the total fuel flow, the addition of the oscillated fuel close to the outer edge of the annular ring flame holder resulted in attenuations around 6 dB for the range of equivalence ratios considered. 

Solution. Assume an infinite plane containing m point sources per unit area each of strength m. The plane is located in the (y,z) plane at x = 0. All the point sources in the plane lying within a thin annular ring of radius r and thickness dr centered on the x-axis will contribute a concentration at the point P located along the x-axis at a distance, x, given by... 

In its ultimate form, AIDECS is intended to be an inspection device which will provide a high resolution, three-dimensional scan profile of an entire expl charge in an artillery shell. It is designed to perform a differential measurement which, with an appropriately small inspection volume element, will not only identify the presence of discontinuities in the expl (such as voids, cracks, annular rings, base separations and inclusions), but is also to provide data about their size, three-dimensional location and orientation... 

Figure 4.23. Different possible flow modes in rotary processing of polyester resin 1 - quasi-solid rotation 2 - stable hydrocyst 3 - rotation in an annular (ring-shaped) layer, 4 - cascade flow. [Adapted, by permission, from I. L. Throne, I. Gianchandani, Potym. Eng. Sci., 20 (1980), 913.]...

By jet velocity is meant the value of the average velocity at the vena contracta. The velocity profile across an orifice opening such as that shown in Fig. 10.5a is seen to be nearly constant except for a small annular ring around the outside. The average velocity V is thus only slightly less than... 

The output bias contact 107 is shaped to concentrate an electric field bias in the immediate vicinity of the contact 107. This concentrated field sweeps away minority carriers which otherwise accumulate near the output contact. It is proposed that the contact 107 is shaped by extending it towards input bias contact 105, or that the detector material 103 near this contact 107 is configured by slotting or tapering, or that an annular ring input bias contact surrounds a circular disc output contact. 

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