Turbines shrouded

Structural components Beams, panels, decking, containers Possible niche applications for EMI shielding, corrosive/abrasive environments, fire-protection, missile protection (e.g. gas turbine shrouds) and major infrastructure applications... 

The rotor or impeller of the radial-inflow turbine eonsists of a hub, blades, and in some eases, a shroud. The hub is the solid axisymmetrieal portion of the rotor. It defines the inner boundary of the flow passage and is sometimes ealled the dise. The blades are integral to the hub and exert a normal foree on the flow stream. The exit seetion of the blading is ealled an exdueer and it is eonstrueted separately like an indueer in a eentrifugal eompressor. The exdueer is eurved to remove some of the tangential veloeity foree at the outlet. 

At the exit of the turbine, the absolute exit veloeity is axial. Sinee the blade speed varies at the exit from hub to shroud, a series of blade diagrams are obtained as shown in Figure 8-12. 

In most designs, the reaetion of the turbine varies from hub to shroud. The impulse turbine is a reaetion turbine with a reaetion of zero (R = 0). The utilization factor for a fixed nozzle angle will increase as the reaction approaches 100%. For = 1, the utilization factor does not reach unity but reaches some maximum finite value. The 100% reaction turbine is not practical because of the high rotor speed necessary for a good utilization factor. For reaction less than zero, the rotor has a diffusing action. Diffusing action in the rotor is undesirable, since it leads to flow losses. 

In high-temperature gas turbines cooling systems need to be designed for turbine blades, vanes, endwalls, shroud, and other components to meet metal temperature limits. The concepts underlying the following five basic air-cooling schemes are (Figure 9-13) ... 

In large gas turbines labyrinth seals are used in statie as well as dynamie applieations. The essentially statie funetion oeeurs where the easing parts must remain unjoined to allow for differenees in thermal expansion. At this junetion loeation, the labyrinth minimizes leakage. Dynamie labyrinth applieations for both turbines and eompressors are interstage seals, shroud seals, balanee pistons, and end seals. 

Beeause of temperature eonstraints, the transdueers, whieh usually do not operate above 350 °F (177 °C) are loeated outside the engine. A probe is then loeated inside to direet the air to the transdueer. Most manufaeturers provide probes to measure the eompressor inlet pressure, eompressor exit pressure, and the turbine exhaust pressure. These probes are usually loeated along the shroud of the maehine, and therefore, the pressure readings may be slightly in error due to boundary-layer effeets. 

For turbine mixers that the width of a baffle should not exceed more than one-twelfth of the tank diameter and, for propeller mixers, no more than one-eighteenth the tank diameter. With side-entering, inclined or off-center propellers, as shown in Figure 13, baffles are not required. Instead, shrouded impellers and diffuser rings may be used to suppress vortex formation. These devices contribute to flow resistance and reduce circulation by creating intense shear and abnormal turbulence... 

Flat blade disc turbine, 11. Shrouded turbine. ... 

Diffuser ring shrouded turbines stator ring having 20 blades,... 

Figure 5-5U. Shrouded turbine for high pumping capacity. Usually used with low static heads, creates minimum of direct shear. Courtesy of International Process Equipment Co., Div. of Patterson Foundry and Machine Co.

Poddle l/Shoft(D/W = 8) Shrouded Turbine-F Stotor Propeiler Pitch = 2D... 

Poddl l/Shoff(D/W = 8) Shrouded Turbin + Stotor Propeller Pitch = 20... 

Figure 7.21. Variation in turbine impeller designs (a) Flat blade (b) Disc flat blade (c) Pitched vane (d) Curved blade (e) Tilted blade (/) Shrouded (g) Pitched blade (h) Pitched curved blade (7) Arrowhead...

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.

A rotating impeller in a fluid imparts flow and shear to it, the shear resulting from the flow of one portion of the fluid past another. Limiting cases of flow are in the axial or radial directions so that impellers are classified conveniently according to which of these flows is dominant. By reason of reflections from vessel surfaces and obstruction by baffles and other internals, however, flow patterns in most cases are mixed. When a close approach to axial flow is particularly desirable, as for suspension of the solids of a slurry, the impeller may be housed in a draft tube and when radial flow is needed, a shrouded turbine consisting of a rotor and a stator may be employed. 

Clare, H., Effect of Burner Shroud Air on Fuel Spray, Natl. Gas Turbine Est. Rept. 

The Kuhni contactor (Fig. 13e) has gained considerable commercial application in Europe. Its principal features are the use of a shrouded turbine impeller to promote radial discharge within the compartments and a variable hole arrangement to allow flexibility of design for different process applications. Kuhni extractors are used for extraction of petrochemicals and chemicals, phosphoric acid purification, as well as hydrometallurgical applications and wastewater treatment. Columns up to 16.5 ft in diameter have been constructed. 

Flat blade disc turbine, 12. Diffuser ring shrouded turbines... 

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