Swirl vanes

In practice it has been found that the diameter of holes in the primary zone should be no larger than 0.1 of the liner diameter. Tubular lines with about 10 rings of eight holes each give good efficiency. As discussed before, swirl vanes with holes yield better combustor performance. 

In the second configuration (moderate swirl) tested (see Fig. 20.2a), only the air stream was forced and no liquid-fuel pulsations were imposed. The experiments were performed with a Parker-Hannifan Research Simplex Atomizer. The atomizing nozzle consisted of a primary liquid ethanol feed with a coaxial primary air stream. The air stream passed through a set honeycomb, flow-straightener, and swirl vanes to provide the necessary level of swirl. Three loudspeakers were used to excite the primary air. 

Ghoniem As you increase the number of swirl vanes, you increase the number of places where the flow separates. Thus, pressure drop is affected. How will you handle this ... 

The mixer includes three air passages equipped with swirlers leading into the combustion chamber. The two central coaxial passages feature axial swirlers, while the external air passage heis radial swirling vanes. Air blast fuel atomizers... 

The effect of swirl distribution in the burner on droplet size and velocity distribution, flow, and flame characteristics is reported. Three examined swirl distributions are 50°/30 , 50 /—30°, and 65°/30 , where the first number indicates the swirl vane angle of the inner annulus and the second number refers to that at the outer annulus. Three airflow distributions of 25%/75%, 50%/50%, and 75%/25% were examined for each swirl distribution. The first percentage number indicates the fraction of the total combustion airflow through the inner annulus, while the second number refers to that at the outer annulus. The results presented here are for swirl distributions of 65 /30° and 50 /30° only, where the total airflow was held constant to maintain a fixed equivalence ratio of 0.4. 

Design mode, which can be (a) a scroll or swirl vane inlet instead of the tangential duct, (b) straight-through flow, without the conical portion, (c) insertion of various kinds of internal vanes, or (d) mechanical centrifugal separators... 

The nozzles should not have internal moving parts such as swirl vanes, turbulence promoters, etc. They should not have orifices or internal restrictions which would narrow the flow passage to less than 0.64 cm (0.25 inch) one quarter of an inch in diameter. 

In this case, the dust is localized in the aimular wall layer of a certain thickness in a spiral of dust accumulations in the form of bundles. Initiated the formation of helical bundles is dusty swirl vane. With the passage of dust in vane curved chaimel is the concentration of particles in the peripheral zone of the chaimel. Thus, after the passage of a uniform flow swirler vane is divided into a number of parallel streams with alternating then small, the large concentration of dust. The thickness and density of the boundary layer depends on the gas velocity, the angle of twist, and the character input stream to a dynamic scrubber. Higher speeds may reduce... 

Figure 6.12 Burner nozzle geometry for pulverized fuel combustion in a rotary kiln. Left swirl vanes Right center insert for flame stabilization.

Over the decades that cyclones have been used, many different reverse-flow cyclone geometries have been tried to improve efficiency, prevent particle attrition, prevent erosion of the cyclone wall, or prevent particle buildup on the cyclone surfaces. However, there are a few basic types that have emerged as the most popular over the years. Some of these cyclone types are shown in Fig. 3. The cyclones shown in this figure are the tangential inlet cyclone, the volute Met cyclone, and the axial inlet cyclone. This last type of cyclone uses axial swirl vanes to impel the gas solids mixture into rotary centrifugal motion. 

Fig. 1.3.8. Side and top views of the four most used inlet configurations, a circular or pipe inlet, b slot (also called tangential ) inlet, c wrap-around inlet, and d axial inlet with swirl vanes...

The fourth type of inlet we wish to describe is that of swirl vanes. As shown in Fig. 1.3.8 d, a swirl-vane assembly allows the gas to enter the cyclone parallel to the axis of the cyclone The swirl-vane assembly is positioned between the vortex finder (or, in case of a straight-through device, see below, a central solid body) and the outer (body) wall of the cyclone. This type of inlet is often inserted in cylindrical-bodied cyclones rather than in cylinder-on-cone or conical-bodied geometries. When it is, we refer to the separator as a swirl tube. Swirl tubes are often of small size (by commercial standards) and are most commonly arranged in a parallel array on a common tube-sheet within a pressure-retaining vessel. They are normally fed from, and discharge into, common, but separate overflow and underflow plenums. 

Much less experimental data are available on the effect of solids loading on the separation efficiency of swirl tubes with swirl vanes. If the effect of solids loading is indeed one taking place in the inlet region of tangential inlet cyclones, we might expect it to be quite different in devices with swirl vanes. 

One is that the end of the vortex is an axisymmetric phenomenon, that the end represents a sort of recirculating gas bubble . Such a vortex end is observed in the research field of vortex breakdown in vortex tubes , tubes in which a flowing liquid is caused to swirl with swirl vanes. A difference between a vortex tube and a cyclone or swirl tube is that the flow reverses in the latter, while in the vortex tube it continues past the vortex end, and discharges from the bottom of the tube. Another difference is that this type of experiment is usually (but not always, see Sarpkaya, 1995) performed under laminar flow conditions, while the flow in a cyclone is turbulent. 

This configuration is also sometimes called a tangential inlet, but we reserve this term to distinguish from axial inlets with swirl vanes... 

This completes our look at the design of cylinder-on-cone cyclones with tangential inlets. In the following section we discuss the design of cylindrical swirl tubes with swirl vanes. In this discussion, we concentrate on the aspects that are specific to swirl tubes. For the aspects shared between swirl tubes and tangential entry cyclones, much of the discussion above is equally valid for swirl tubes, such as the discussion pertaining to vortex finder configurations. 

Design of Swirl Tubes with Swirl Vanes... 

Figure 15.2.1 shows a cylindrical swirl tube with swirl vanes. We will look at the effects of two aspects of vane design the shape of the vanes—in particular the entrance and exit angles—and their thickness and number, which determines the area available for flow and, therefore, the velocity in the vane-pack. In this discussion we will often refer to the individual vane elements comprising the vane assembly as a blade element , vane element , or simply blade or vane . 

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