Turbine shaft

In many large plants, an intermediate pressure (IP) turbine is located on the same shaft as either the HP turbine or the low pressure (LP) turbine. In this arrangement, a common gearbox translates the torque from the high speed turbine shaft to a generator shaft turning at a much lower speed. Unless reheat is used, the steam exiting the HP turbine is typicaHy used directly in the IP turbine. 

It was established by feeding measurements that there was a potential difference of 0.45 V between the turbine shaft and the housing. A shaft slip-ring served for the necessaiy potential equalization (see Fig. 21-5). After this system was installed, the potential difference was only <5 mV. According to the operating conditions of the turbine, a current up to 1.5 A flows through this system. 

Radial fit bolts are a special feature used in all types of turbomachinery. They are of increasing importance to users that are both reliability-minded and concerned about life-cycle costs. The radial fit coupling bolt was originally developed for coupling steam turbine shafts by Pilgrim International in Oldham, UK. It is equally useful to coupling other equipment, including, of course, hot gas expander shafts. 

The hydraulieally tensioned, radial-fit bolt (Figure 6-32) replaees the traditional turbine shaft eoupling bolt and is reusable. The main body of the bolt is threaded at eaeh end and has a slight taper on the eenter seetion, whieh engages with the similarly internally tapered sleeve and the two nuts. The bolt is taper-bored at eaeh end to aeeept the puller that is part of the hydraulie tensioning system. 

The methane warms to 10°C. It then passes through the booster compressors on the expansion turbine shaft, increasing in pressure from 325 psi to 375 psi before being introduced into other gas compressors tliat boost the pressure back up to 600 psi. This is the pressure needed for reintroduction of the natural gas back into the TransCanada pipeline. This 50 psi boost, which makes use of available energy from the expansion turbines, provides a significant savings in electrical power. 

The high-veioeity gas impinges on the biade where a iarge portion of the kinetie energy of the moving gas stream is eonverted into turbine shaft work. 

The gas turbine during the start-up is on an auxiliary drive, initially it is brought to a speed of about 1200-1500 RPM when ignition takes place and the turbine speed and temperature rise very rapidly. The bleed valves are open to prevent the compressor from surging. As the speed reaches about 2300-2500 rpm, the turbine is declutched from its start-up motor, the first set of bleed valves are closed, and then as the turbine has reached near full speed, the second set of bleed valves are closed. If the turbine is a two or three shaft turbine as is the case with aero-derivative turbines, the power turbine shaft will break loose at a speed of about 60% of the rated speed of the turbine. 

To analyze a turbine, it is neeessary to measure pressures and temperatures aeross the turbine, shaft vibration, and the temperature and pressure of the lubrieation system. Table 19-7 shows the effeet various parameters have on important funetions of the turbines. Analysis of these parameters will aid in the predietion of ... 

Both top and bottom halves of the journal bearings should be inspected for misalignment wear as well as excessive in-line wear, which can occur in turbines with frequent starts. An indication of the condition of the thrust-bearings can be made by removing a small section of the turbine shaft, usually on the governor end, and axially moving or bumping the shaft. The amount of axial shaft movement will indicate the thrust clearance and, if it is found to be 0.012-0.015 inches, it can be considered normal. 

Extra nozzles require a longer turbine shaft, which increases the span between bearings which can produce rotor dynamics problems. 

Main Oil Pumpr Irttegrqlj Driven from Turbine Shaft Separate Turbine Driven Separate... 

Figure 14-16F. Cutaway of large steam turbine, multistaged, multivalve, for driving mechanical rotating equipment. Connection to mechanical driven equipment shaft shown as a flange joint on right end of turbine shaft. Exhaust steam is at lower right, inlet steam is at bottom center near smaller wheels. (Used by permission Bui. 8908-E0MD. Dresser-Rand Company.)...

The lubricating oil system for a turbine is very important and is nearly always provided with a dual pumping arrangement. One pump can be driven directly off the turbine shaft and the other by separate electric motor or steam turbine. In another arrangement, one pump can be separately electric driven and the other separately steam turbine driven. Twin coolers are often provided in the dual system to... 

It is important to seal the glands on the turbine shaft, and a typical arrangement is illustrated in Figure 14-24. Thrust bearing failures can be serious problems for steam turbines and other mechanical drives, as well as the bearings used on the driven equipment. 

A design of turbine in which a partial reduction in steam pressure takes place in fixed nozzles (vanes) and a further steam pressure reduction takes place in nozzles created by moving rotor blades. A reactive force is generated that results in the rotation of the turbine shaft. 

The maximum and minimum temperatures and pressures of a 40 MW turbine shaft output power ideal air Brayton power plant are 1200 K (Ta), 0.38 MPa (P3), 290 K (TO, and 0.095 MPa (Pi), respectively. Determine the temperature at the exit of the compressor Tj), the temperature at the exit of the turbine (P4), the compressor work, the turbine work, the heat added, the mass rate of flow of air, the back-work ratio (the ratio of compressor work to the turbine work), and the thermal efficiency of the cycle. 

The curve in Fig. 18.4 also represents the best possible vacuum that can be obtained in any surface condenser. The majority of surface condensers I have seen do operate right on the curve. Condensers operating below the curve are typically suffering from air in-leakage through the turbine shaft seals. 

HUM Required hot water mass flow rate WA Net turbine shaft work output CR Condenser shell-side pressure loss coefficient X2 Turbine exit quality... 

The conpressor power is within the range of single-stage turbines. If it is assumed that the compressor will be directly coupled to the steam turbine, the compressor shaft power must be matched by the steam-turbine shaft power. Allowing for a 10% safety factor, the power dehvered to the coii5)ressor will be 110 hp (82.0 kW). From Equation 5.11.5, the turbine efficiency, qe, at 36,000 rpm, 110 hp (82.0 kW), and 1.30 MPa (188.5 psi), is 36%. 

A gas turbine engine is fueled with 3000 kg/h of methane at 15°C and 1000kPa, and supplied with ambient air at 15°C. The air and fuel are compressed to 2900 kPa and fed to a combustor. The air flow rate is designed to give a temperature of 1400°C at the outlet of the combustor. The hot gas leaving the combustor is expanded in the turbine. Shaft work produced by the turbine is used to power the two compressors and run a dynamo for generating electricity. 

The spreadsheet model of the dynamo is relatively simple, as illustrated in Figure 4.38. The model takes the turbine shaft work and compressor duties as inputs. The friction losses are estimated as 1% of the turbine shaft work. The friction losses and compressor duties are then subtracted from the shaft work to give the net power from the dynamo, which is calculated to be 17.7 MW... 

When steam and electricity are co-generated, it is often critical to know how much of the costs should be attributed to each commodity. The first step in determining the unit cost of the turbine shaft work and that of the "back-pressure steam" (the exhaust steam from the turbine) is to obtain the unit cost of the high-pressure steam supplied to the turbine. This cost can be determined by applying the foregoing expression for the unit cost of product, c, to the boiler ... 

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