Currently Available Steam Turbine Designs

Following are illustrations and descriptions of several steam turbines and components, including a range of capacities and designs.

Figure 11-54 is an open-case view of a single-stage Elliot turbine available in capacities up to about 3,500 hp (2,600 kW). These units range in size up to about 5 ft (1.5 m) long and 3.5 ft (1 m) wide and high, with a weight of about 2,500 lbm (1,100 kg). The turbine has an operating speed range of between 1,000 and 7,000 rpm. To the far right are lubricated steel governor linkage pins connecting to a Woodward governor. To the left of the governor assembly is the rotor locating bearing, which was shown above. To the right of the turbine wheel are the carbon sealing rings. The three segments of each ring are held in place by springs, which prevent the seals from rotating. These units are commonly used to drive pumps, blowers, fans, compressors, and electric generators.

Fig. 11-54 Open-Case View of Single-Stage Steam Turbine. Source: Elliott Company

Single Stage Turbine Rotor Wheel

Fig. 11-55 Closed-Case View of Horizontally Split Single-Stage Steam Turbine. Source: Tuthill Corp., Coppus Turbine Div.

Fig. 11-54 Open-Case View of Single-Stage Steam Turbine. Source: Elliott Company

Figure 11-55 is a closed-case view of a horizontally split, single-stage steam turbine. The inlet and exhaust connections are shown in the lower half casing. The inlet connection on the left is differentiated from the exhaust connection by its smaller diameter. The upper half casing can be removed to permit easy access to internal components for inspection and routine maintenance.

Marine Steam Turbine
Fig. 11-56 Cutaway Illustration of Vertical Single-Stage Steam Turbine. Source: Tuthill Corp., Coppus Turbine Div.

Fig. 11-55 Closed-Case View of Horizontally Split Single-Stage Steam Turbine. Source: Tuthill Corp., Coppus Turbine Div.

Figure 11-56 is labeled a cutaway illustration of a vertical single-stage steam turbine. Vertical designs allow for easy mounting on vertical drive equipment. The compact configuration and small footprint is well suited for limited space and in-line installations. A vertical single-stage turbine is shown in Figure 11-57.

Figure 11-58 shows a standard multi-stage turbine with a capacity range of up to 7,000 hp (5,200 kW) at a speed of 8,000 rpm, with steam conditions of 700 psi (48 bar) and 825°F (441°C). Figure 11-59 is an open-case

Fig. 11-57 Vertical Single-Stage Steam Turbine. Source: Tuthill Corp., Coppus Turbine Div.
Fig. 11-58 Multi-Stage Steam Turbine with Capacity Range of up to 7,000 hp (5,200 kW). Source: Dresser-Rand

low-pressure rotor featuring extremely long exhaust blades.

Figure 11-62 shows a detailed cross-sectional view of three steam turbine designs: straight non-condensing, single automatic extraction/admission condensing, and double automatic extraction/admission condensing. The two units shown on the bottom are both double automatic extraction units.

Figure 11-63 shows a low-p res-sure condensing steam turbine driving a compressor. The turbine is rated at 997 hp (743 kW) at 3,980 rpm with steam conditions of 2 psig (115 kPa), dry and saturated, to 4 in. HgA (14 kPa). This turbine was designed to operate efficiently under such low steam inlet pressure and

Fig. 11-59 Open-Case View Revealing Rotor of Extraction/Induction Steam Turbine. Source: Tuthill Corp., Murray Turbomachinery Div.

view revealing the rotor of an intermediate capacity multi-stage extraction/induction steam turbine. This turbine frame can accommodate up to 15 stages with a maximum power range of up to 15,000 hp (11 MW) and a maximum speed range of up to 15,000 rpm. Maximum inlet steam conditions range up to 900 psi (62 bar) and 900°F (482°C). Maximum non-automatic (bleed) extraction exhaust pressures range up to 400 psig (28 bar).

Figure 11-60 is an overhead open-case view of a 42,000 hp (31 MW) high-pressure extraction steam turbine. Figure 11-61 shows a large capacity steam turbine

Fig. 11-60 Overhead Open-Case View of 42,000 hp (31 MW) High-Pressure Extraction Turbine. Source: Dresser-Rand
Fig. 11-61 Large Capacity Low-Pressure Steam Turbine Rotor. Source: ABB Stal

Fig. 11-62 Steam Turbine Design Types. Source: General Electric Company

Fig. 11-63 997 hp (743 kW) Condensing Steam Turbine Operating with 2 psig (115 kPa) Inlet Steam Condition. Source: Tuthill Corp., Murray Turbomachinery Div.

achieves a full-load steam rate of 25.8 lbm/hp-h (8.7 kg/kW).

Because turbines are custom built, efficiency and operating characteristics can be optimized for each application. Once a unit is designed, it may be pre-packaged to reduce erection time at the site. Figure 11-64 shows a high-pressure steam turbine unit in the 70,000 hp (52 MW) capacity range being prepackaged on its base frame.

Fig. 11-64 Packaged High-Pressure Steam Turbine in the 70,000 hp (52 MW) Capacity Range. Source: ABB Stal

Combined cycles and steam injection cycles are important enhancements to conventional prime mover simple cycles. They can conserve energy by converting rejected heat into additional power production and they reduce air emissions per unit of power generated. Whereas cogeneration cycles involve the use of recovered heat to serve thermal processes, combined and steam injection cycles use recovered heat in the form of high-pressure steam to produce additional power. As such, the techniques are important alternatives in applications where process uses for cogenerated thermal energy are either not available or somewhat limited.

A combined cycle is the sequential linking of any topping and bottoming cycle, or two simple cycles. Typically, a gas turbine or reciprocating engine is used to generate shaft power at the top of the cycle, with steam generated from turbine or engine exhaust heat. The steam is then passed through a steam turbine to generate additional power at the bottom of the cycle.

With gas-turbine systems, an alternative to adding a bottoming cycle is to use the steam injection cycle (also known by trade names as STIG™ or Cheng™ cycles), in which recovered heat is used to generate additional power by injecting steam directly into the gas turbine. It is similar in concept to a combined cycle in that increased mass flow is passed through a turbine to produce more power. The difference is that the increased mass flow is injected into the same (gas) turbine (operating on an open Brayton cycle), as opposed to a different (steam) turbine (operating on a closed Rankine cycle).

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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