Steam turbines operation

Most steam turbines operate in the condensing (of steam on exhaust from turbine) mode or noncondensing or backpressure mode. (Steam is exhausted or extracted from the turbine at preselected exhaust pressure for other uses.) See Figures 14-17A-C, 14-18A, 14-18B, 14-19A, 14-19B, 14-20A, and 14-20B. 

All turbines are variable-speed drivers and operate near or above one of the rotor s critical speeds. Narrowbands should be established that track each of the critical speeds defined for the turbine s rotor. In most applications, steam turbines operate above the first critical speed and in some cases above the second. A movable narrowband window should be established to track the fundamental (1 x), second (2x), and third (3x) harmonics of actual shaft speed. The best method is to use orders analysis and a tachometer to adjust the window location. 

A steam turbine operates with inlet steam conditions of 40 barg and 420°C and can be assumed to operate with an isentropic efficiency of 80% and a mechanical efficiency of 95%. Calculate the power production for a steam flowrate of 10 kg s-1 and the heat available per kg in the exhaust steam (i.e. superheat plus latent heat) for outlet conditions of ... 

A steam turbine, operating isentropically, takes in superheated steam at 1,800 kPa and discharge at 30 kPa. What is the minimum superheat required so that the exhaust contains no moisture What is the power output of the turbine if it operates under these conditions and the steam rate is 5 kg s 1-... 

A steam turbine operates adiabatically with a steam rate of 30 kgs. The steam is supplied at... 

A steam turbine operates adiabatically at a power level of 3,000 kW. Steam enters the turbine at 2,IOOkPa and 47S°C and exhausts from the turbine as saturated vapor at 30 kPa. What is the steam rate through the turbine, and what is the turbine efficiency ... 

A steam turbine operates adiabatically with a steam rate of 30 kgs. The steam is supplied all 1,050 kPa and 37S°C and discharges at 20 kPa and 7S°C. Determine tthe power output of the turbine and the efficiency of its operation in comparison with a turbine that operates isentropically from the same initial conditions to the same final pressure. 

A steam turbine, operating reversibly and adiabatically, takes in superheated steam at 2000 kPa and discharges at 50 kPa. 

Table 11.2. Typical Steam Turbine Operation Conditions ...

Since for steam turbine operation we may assume Cp > 2000 J/(kg K) and s - Sg < 2000 J/(kg K), squared and higher terms in (16.66) will contribute relatively little to the final figure, and may be neglected for the purpose of estimating the effect of the error in specific heat on the calculation of specific enthalpy. Assuming the error in average specific heat is fractional, we may expand using the binomial expansion ... 

Another Example of Using the Entropy Balance in Problem Solving A steam turbine operates at the following conditions ... 

A steam turbine operates with a steam flow rate of 3 kg/s. At the inlet, the steam is at 300 °C, 5800 kPa, and 32 m/s. At the outlet, the steam is saturated at 99.6 °C, 100 kPa, and 75 m/s. Heat loss is 30 kJ/s. Estimate the power produced by the steam turbine and compare with the power produced when the steam power production is carried out at reversible conditions. 

Rotating equipment used in the process industry includes pumps, compressors, motors and turbines. For pumps and compressors with fixed speed motors, minimizing spill backs could result in significant power savings. Optimizing steam turbine operation and maintenance could save steam. The selection of process drivers, namely, motors versus steam turbines, could save energy costs. 

An example is that a large pump is driven by a steam turbine operating between ISOpsig and atmospheric condition. 3800 Ib/h steam is measmed online. The pump power requirement is estimated by equation (8.1) as 72 hp. On the other hand, the theoretical power supplied by the steam mrbine can be estimated from the theoretical steam table. The steam table indicates the specific steam rate of 18.22 Ib/kWh, which indicates the steam turbine can deliver 208.6 kW (38001b/h/18.221b/kWh) or 279.6 hp. Thus, the overall efficiency of the turbine and pump is only 26% (72/279.6). This efficiency is much lower than design. It was found that steam turbine blades were severely eroded over time and no inspection and maintenance work was ever done on the turbine for a long time. 

Both EdF reference sets of EOPs have four separate procedures for the reactor operator, for the water and steam (turbine) operator, for the shift supervisor (containing a combination of reactor, water and steam operator procedures) and for the safety engineer. All procedures are in the colour flow chart format (paper based). The recent four loop N4 plants have fully computerized procedures (with computerized operating actions actuated from the operator video display units) as well as a complete backup paper based set of procedures for operating from the auxiliary panel if the computer system fails. 

The pony motors are direct-shaft linked to the primary drive turbines for reduced circulation of the primary loop coolant should steam be lost to the drive turbines. The BPA power system is used to power the electric drive units. These units are normally de-energized during steam turbine operation but will be automatically energized if pump drive speeda falls below 900 HPH ... 

The temperatures are in Kelvin, where room temperature is about 290 K, and so T2 is never likely to be small. As an example, for a steam turbine operating at 400°C (675 K), with the water exhausted through a condenser at 50°C (325 K), the Carnot efficiency limit is... 

Steam turbines operate in far less demanding service than gas turbines as the following list of typical steam turbine materials illustrates. 

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