Turbines mixed-flow turbine

Mixed-Flow Turbine. The turbine as shown in Figure 1-35, is almost identical to a centrifugal compressor—except its components have different functions. The scroll is used to distribute the gas uniformly around the periphery of the turbine. 

Abidat, M.I., Chen, H., Baines, N.C., and Firth, M.R., 1992. Design of a Highly Loaded Mixed Flow Turbine, Proc. Inst. Mechanical Engineers, Journal Power 8 Energy, 206 95-107. 

Arcoumanis, C., Martinez-Botas, R.F., Nouri, J.M., and Su, C.C., 1997. Performance and Exit Flow Characteristics of Mixed Flow Turbines, International Journal of Rotating Machinery, 3(4) 277-293. 

Wallace, F.J., and Pasha, S.G.A., 1972, Design, Construction and Testing of a Mixed-Flow Turbine. 

Regenerative - turbine Vertical - turbine Mixed - flow... 

Hi) Pitched blade turbines (mixed flow agitators)... 

Rouse, H. (1976). John B. McCormick. Hydraulics in the United States 1776-1976 40-41. P Safford, A.T., Hamilton, E.P. (1922). The American mixed-flow turbine and its setting. Trans. ASCE 85 1237-1292. 

In emulsion polymerization, a high shear rate may cause coagulation. However, a certain amount of turbulence is required for emulsification and to avoid phase segregation. Moreover, high fluid circulation is needed in order to guarantee the macroscopic uniformity and to enhance mass and heat transfer. In this way, mixed-flow turbines with features of both radial and axial flow can be useful. The most common of these impellers is the 45° angled blade turbine. Multiple impellers on the same shaft can also be employed. 

Similar diagrams may be constructed to apply to other combinations such as double automatic and mixed-flow turbines. As an example, lines of constant induction flow would be located below and parallel to a line of zero induction flow in the case of mixed-pressure or induction turbines. 

Turbine Pumps The term Turbine pump is applied to units with mixed-flow (part axial and part centrihigal) impellers. Such units are available in capacities from 20 mVh (100 gal/min) upward for heads up to about 30 m (100 ft) per stage. Turbine pumps are usually vertical. 

FIG. 10-46 Vertical multistage turbine, or mixed-flow, pump. 

There are three types of mixing flow patterns that are markedly different. The so-called axial-flow turbines (Fig. 18-3) actually give a flow coming off the impeller of approximately 45°, and therefore have a recirculation pattern coming back into the impeller at the hub region of the blades. This flow pattern exists to an approximate Reynolds number of 200 to 600 and then becomes radial as the Reynolds number decreases. Both the RlOO and A200 impellers normally require four baffles for an effective flow pattern. These baffles typically are V12 of the tank diameter and width. 

Axial-flow turbines are often used in blendiug pseudoplastic materials, and they are often used at relatively large D/T ratios, from 0.5 to 0.7, to adequately provide shear rate in the majority of the batch particularly in pseudoplastic material. These impellers develop a flow pattern which may or may not encompass an entire tank, and these areas of motion are sometimes referred to as caverns. Several papers describe the size of these caverns relative to various types of mixing phenomena. An effec tive procedure for the blending of pseudoplastic fluids is given in Oldshue (op. cit.). 

Impeller Radial Flow. Impeller Mixed Flow. Vertical Regenerative Turbine. 

The inward-flow radial turbine has many components similar to a centrifugal compressor. There are two types of inward-flow radial turbines the cantilever and the mixed-flow. The cantilever type in Figure 1-34 is similar to an axial-flow turbine, but it has radial blading. However, the cantilever turbine is not popular because of design and production difficulties. 

The radial-inflow turbine has many eomponents similar to those of a eentrifugal eompressor. Flowever, the names and funetions differ. There are two types of radial-inflow turbines the eantilever radial-inflow turbine and the mixed-flow radial-inflow turbine. Cantilever blades are often two-dimensional and use nonradial inlet angles. There is no aeeeleration of the... 

Figure 8-4. Mixed-flow-type radial-inflow turbine.

The primary cause of efficiency losses in an axial-flow turbine is the buildup of boundary layer on the blade and end walls. The losses associated with a boundary layer are viscous losses, mixing losses, and trailing edge losses. To calculate these losses, the growth of the boundary layer on a blade must be known so that the displacement thickness and momentum thickness can be computed. A typical distribution of the displacement and momentum thickness is shown in Figure 9-26. The profile loss from this type of bound-ary-layer build-up is due to a loss of stagnation pressure, which in turn is... 

Slow speed close-clearance impellers are used when mixing high viscosity materials. Helical or anchor type close-clearance impellers are used in this application at speeds from 5 to 20 rpm. Table 1 compares the pow er required and cost for conventional axial flow turbines and the helical type. 

As is shown in Fig. 4.3a, the lower pressure cooling is fed by air i/(l at state 7, at a corresponding pressure p-j and a temperature T, and this mixes with air (1 + 4>w) froni the HP exhaust at temperature T,) to produce a temperature Tg as indicated in the diagram. The full turbine gas flow (1 + i/() then expands through a pressure ratio Al to a temperature Tio, and subsequently rejects heat, finishing at Tj = Ta. 

For two step cooling, now with irreversible compression and expansion, Fig. 4.7 shows that the turbine entry temperature is reduced from Ti. to by mixing with the cooling air i/ H taken from the compressor exit, at state 2, pressure p2, temperature T2 (Fig. 4.7a). After expansion to temperature Tg, the turbine gas flow (1 + lp ) is mixed with compressor air at state 7 (mass flow i/h.) at temperature Tg. This gas is then expanded to temperature T g. 

Engineers quickly recognized that turbines could be arranged iu a variety of ways. For example, water could be fed to the wheel internally (as Fourneyron s machine did), externally, axially, or by a combination. Between 1830 and 1850 a host of European and American engineers experimented with almost every conceivable arrangement. The turbines that resulted— the most popular being the mixed-flow Francis turbine—quickly demonstrated their superiority to traditional vertical wheels in most respects. Turbines were... 

At present our 6-m tank reactor gives 75% conversion for the first order reaction A R. However, since the reactor is stirred with an underpowered paddle turbine, we suspect incomplete mixing and poor flow patterns in the vessel. A pulse tracer shows that this is so and gives the flow model sketched in Fig. E12.2. What conversion can we expect if we replace the stirrer with one powerful enough to ensure mixed flow ... 

The impeller is the part of the agitator that impacts force to the material being mixed. Propellers, turbines, gates, anchors, and paddles are all types of impellers. Typically, the impeller is a single propeller or turbine blade connected to a shaft that is driven by an electric motor at a fixed speed. There are two classes of impeller agitators axial-flow and radial-flow, and the mixing characteristics are shown in Figure 3.14. 

Pitched blade turbine The pitched blade turbine is essentially a modified open flat-blade turbine with the blades angled (Figure 3.16). It is available with different blade angles and the 4-blade, 45° pitch turbine is the most common and popular type. The flow is discharged both axially and radially, depending on the angle. For the typical case of a 45° axial-flow turbine, one half of the total flow is discharged axially and one half radially (mixed-flow). 

Figure 7.10. Some types of impellers for centrifugal pumps, (a) Open impeller, (b) Semiopen impeller, (c) Shrouded impeller, (d) Axial flow (propeller) type, (e) Combined axial and radial flow, open type, (f) Shrouded mixed-flow impeller, (g) Shrouded impeller (P) in a case with diffuser vanes (V). (h) Turbine impeller.

Turbine pumps mix features of a simple propeller (axial flow) pump with a centrifugal pump and are often referred to as units with mixed flow. A simple turbine pump carries curved vanes on a central rotating spindle. Such pumps are often immersed in the liquid and find use in closed-loop circulation systems, in condenser circulating water, and in sumps and wells. Turbine pumps have noteworthy pumping capacity, and like positive displacements pumps are often used for heads up to about 100 ft/stage with capacities of up to several hundred gallons/minute. 

Choose the best speed for the pump. Analyze the specific speed and suction specific speed at each of the various operating speeds using the data in Tables 6.20 and 6.21. These tables show that at 870 and 1160 r/min, the suction specific-speed rating is poor. At 1750 r/min, the suction specific-speed rating is excellent, and a turbine or mixed-flow type of pump will be suitable. Operation at 3500 r/min is unfeasible because a suction specific speed of 26,000 is beyond the range of conventional pumps. 

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