Radial reaction turbine

Figure 2-3. Radial reaction turbine. (Source Kuehnie, Kipp, and Kausch.)...

Another advantage of the radial reaction turbine is that it can be designed to accept condensation in any amount without efficiency deterioration or erosion." This is possible because there are two forces acting on suspended fog particles, the deceleration force and the centrifugal force, and these two forces can be balanced against each other to prevent the droplets from impinging on specially shaped blades. The process is explained as follows ... 

An example of a typical turboexpander is shown in Fig. 29-46. Radial-flow turbines are normally single-stage and have combination impulse-reaction blades, and the rotor resembles a centrifugal-pump impeller. The gas is jetted tangentially into the outer periphery of the rotor and flows radially inward to the eye, from which the gas is jetted backward by the angle of the rotor blades so that it leaves the rotor without spin and flows axially away. 

The radial reaction design has been selected for turboexpanders primarily because it attains the highest efficiency of all turbine designs. However, it has several addition features which favor this apphcation ... 

For the preliminary estimate of the expected efficiency of expansion turbines, in most cases it is sufficient to neglect Reynolds number effects (Rg > 10 ) and use the efficiency and specific speed correlations shown in Figure 2-12 for partial admission axial impulse, reaction radial inflow and full admission impulse and reaction axial turbines. Due to the economic advantage of the radial turbine, die radial inflow turbine is die best selection when operating in die specific speed range 20 < Nj < 140, whereby die optimum efficiency will be achieved at N, = 80. 

The two types of turbines—axial-flow and radial-inflow turbines—can be divided further into impulse or reaction type units. Impulse turbines take their entire enthalpy drop through the nozzles, while the reaction turbine takes a partial drop through both the nozzles and the impeller blades. 

Figure 15.38 The radial-flow double-motion reaction turbine (Ljungstrom)...

For highly exothermic reactions, it is necessary to maintain the temperature at a desired level. In general, the heat-transfer coefficient is proportional to (Pg/F)0 25-033, and the actual power cost varies linearly with (Pt/V) these dependencies lead to an optimum value of the reactor volume. For these reactions, when the demand for mass transfer is not important, the radial-flow turbine (curved blades) can be used for an efficient heat transfer. Optimum stirring conditions in the laminar flow regime have been evaluated by Zlokarnik and Judat (1988) and Pawlowski and Zlokarnik (1972). 

In Figure 15.6 the flow patterns in a baffled tank, generated by an axial-flow propeller and a radial-flow turbine stirrer, are shown. A large variety of stirrers is available (Figure 15.7). The selection is made initially based on the viscosity of the reaction mixture [54]. 

Fig. 5.35. Axial and radial turbine blades (a) axial common impulse, (b) axial reaction, and (c) radial reaction.

TTiere are two main types of expansion turbines axial flow and radial flow. Axial flow expansion turbines are like conventional steam turbines. They may be single-stage or multistage with impulse or reaction blading, or some combination of the two. Turbines of this type are used as power recovery turbines. They are used where flow rates, inlet temperatures, or total energy drops are very high. 

Radial-flow expansion turbines are normally single-stage, with combination impulse reaction blades and a rotor resembling a centrifugal... 

In contrast, flat-blade stirrers and turbines mainly cause radial movement (see Figs. 5.4-5 and 5.4-6). An anchor is used to enhance heat transfer between the reaction mixture and the cooling medium. 

From an internal design perspective, the steam turbine is either an impulse-or a reaction-type design. In the United States, almost all turbine designs are of the axial flow variety, and only a small number are of the tangential flow variety. In Europe, a significant number of turbines are of the radial flow... 

With a gas sparger and a radial turbine of the Rushton type, gas loads of up to 500 m3/(m2h) can be achieved with reasonable energy consumption. This method of dispersing the gas phase is usually employed for fast reactions or in situations where the hourly demand for the gaseous reactant is high, as in industrial fermenters. With such high gas-feed rates, the gas reactant may not react completely, so that eventually the unreacted gas may be recycled externally. 

Numerous types of stirrers are used in practice, and Fig. 3.2 shows the most commonly used ones. The stirrers for low-viscosity media are typically marine propeller and pitched-blade turbine stirrers, which cause axial fluid motion, and flat-blade turbines and impellers, which generate radial fluid motion. The former stirrers are suitable for uniformly suspending solids. The latter type are the preferred ones for carrying out exothermic reactions, like autooxidation reactions (see Section 8.3), where the heat generated dining the process has to be removed effectively through the reactor walls. 

In a planar turbine configuration, the flow expands radially through circumferential rows of blades. Stator blade rows are fixed and tend to deviate the flow in the tangential direction. The swirling flow then enters the next blade row that is attached to the disk, the rotor. The curved rotor blades turn the flow in the opposite direction, which imparts a reaction force on the rotor. With respect to the center of the disk, this force is a moment, or torque T, that sets the rotor in motion. This process of fluid-to-mechanical energy conversion is best described by the conservation of angular momentum applied to a control volume enclosing a blade row ... 

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