Ter Linden

FIG. 1 7-37 Variation of tangential velocity and radial velocity at different points in a cyclone. [Ter Linden, Inst. Mech. Eng. J., 160, 235 (1949).]... 

Cyclones have been used to remove particulates from gas streams since the middle of the 19th century (Rietema and Verver, 1961). Early researchers (Rosin et al., 1932 Alexander, 1949 Stairmand, 1951 Ter Linden, 1949 linoya, 1953 Lapple, 1951 van Tongren, 1936) conducted the first experiments designed to understand the operation of this mechanically simple but operationally complex device. Many of these experiments (Ter Linden, 1949 Lapple, 1951 Stairmand, 1951, etc.) resulted in cyclone designs based on relative cyclone dimensions. More recently, Zenz (1975) developed an empirical cyclone design procedure that has achieved popular acceptance in the United States. 

To separate particles from gaseous streams, cyclones are frequently used in large-scale practices. In fact, cyclone based dust collectors are one of the most widely used devices for removing larger-sized particles. Virtually all cyclones used industrially are reverse-flow cyclones. There are two other types of cyclones rotary-flow (CiUberti and Lancaster, 1976a, b) and uniflow (Ter Linden, 1949). Only the reverse-flow cyclone will be considered here. 

As the discussion in Sect. 2.1.1, and Eq. (2.A.12) show, in order for a rotating fluid element to maintain its equilibrium (static position in the r-direction), the pressure on its surface at higher r must exceed that on its surface a lower r. Thus the static pressure must increase monotonically with increasing radius. This, in fact, is borne out by experiment—a classic example of which is the data of Ter Linden (1953), a sample of which is presented in Fig. 3.1.2. Here the lower curves contained within each set of curves represents the variation in static pressure, p, with radial position the upper curves, the total pressure, p+(l/2)y0 (static plus dynamic). Comparing with Eq. (2.1.3) and realizing, as before, that the second term in Bernoulli s trinomial is small, we see from the profiles of total pressure in Fig. 3.1.2 that Bernoulli s trinomial is almost constant in the outer, nearly loss-free part of the vortex, while it decreases significantly in the center. This is as we would have expected. 

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