Turbine Bleeding

Two of the units at the Oak Creek Power Plant have full-sized steam turbine driven boiler feed pumps, along with half-sized motor driven boiler feed pumps for use at low loads and unit startup. The boiler feed pump turbines are supplied with steam from a particular turbine "bleed-point". 

AUTOMATIC EXTRACTION UNIT TURBINE - Bleeds off part of the main steam flow at one, two, or three points. Valved partitions between selected stages control the extracted steam pressure at the desired level. When extracted steam flowing through the unit does not produce enough shaft power to meet the demand, more steam flows through the turbine to exhaust. Located between steam supply and process steam headers. 

To perform thermodynamic analysis of the ORC with turbine bleeding and regeneration, steady-state condition and no pressure drop in any equipment are assumed. The analysis of modified ORC can be given as follows (Desai and Bandyopadhyay, 2009) ... 

Figure 10.4 Schematic diagram of an ORC (a) flow diagram of an ORC incorporating turbine bleeding and regeneration and (b) T diagram of an ORC incorporating turbine bleeding and regeneration working with a dry fluid. Reproduced with permission from Desai and Bandyopadhyay (2009), 2009, Elsevier...

Fla ra meter Cycle with regeneration Cycle with turbine bleeding and regeneration... 

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. 

The shutdown of a gas turbine first requires the shutdown of the steam injection and then the opening of the bleed valves to prevent the compressor from... 

Design of turbine blades to obtain higher effieieney and damping has been done. In some eases, this has improved effieieney by 8-10%, and stopped failures in these blades. Steam injeetion has been utilized in gas turbines to improve effieieney and to inerease the power output. Redesign of various bleed-off ports has redueed tip stalls and their aeeompanying blade failures. 

The turbine applied to driving mechanical equipment is not operated (very often) with extraction or bleed streams. Here again, this depends upon the plant steam balance, and this is one of the fine features of steam turbine drive. The flexibility of design and application allow it to be set in the proper place for the economic balance of a system. The decision as to condensing or noncondensing should not be... 

Large power stations use complex feed heating systems before the boiler feed pumps (LP) and after the boiler feed pumps (HP), which can give high overall thermal efficiencies of 39 per cent. However, for the smaller machine, it becomes uneconomic to consider multiple bleeds from the turbine, and the final choice is dictated by the extra cost for the additional complexity against lower running costs due to increased efficiency. As a minimum, a contact type de-aerator is often employed which would extract a small bleed of around 2-3bar from the turbine. 

Bleed air is a necessary feature of practical gas turbine engines. For example, when one enters a commercial aircraft, the cabin temperature is... 

An open, split-shaft, air bleed Brayton cycle with two compressors (CMPl and CMP2), three turbines (TURl, TUR2, and TUR3), one intercooler (CLRl), one combustion chamber (HTRl), one reheater... 

Flow do you control the power output of a real gas turbine cycle using bleed air ... 

Bleed air is used in a split-shaft gas turbine cycle. The following information is provided ... 

The experimental test and model comparison have been carried out without bleed and hot bypass, but with a cold bypass valve opening of 40%. The use of the cold-air bypass valve (FV-170) allows compressor discharge to be directed into the turbine inlet, bypassing the heat exchangers, air plenum and fuel cell simulator. FV-170 is a nominal 15.4 cm ID Fisher-Rosemont V-150 Vee-Ball control valve with a full range slew rate of 1.5 seconds. 

In the PCU during rapid transients the rate at which inventory must be changed according to the load schedule may not be physically achievable. The helium fill and bleed system has limited capacity. In this case turbine bypass control is used to more quickly vary the power output of the shaft. In this scheme the power output of the turbine is changed by bypassing high pressure compressor outlet coolant to the exit of the turbine. The pressure drop across the turbine is reduced so power is reduced while at the same time the frictional losses through the rest of the PCU circuit increase. The result is a rapid reduction in shaft power. However, PCU efficiency is reduced under turbine bypass control and so control is typically transitioned back to inventory control over time. 

Burner management controls, complete with flame scanners, purging, and cooling should be provided to ensure boiler safety. Supplementary firing should be limited to a fraction of the gas turbine load. The applicable safety codes are a function of the presence of fuel gas in the proximity. Precautions include the use of double stuffing glands with bleeds between the glands on... 

Through the use of such utilization function costs, the turbine costs are separated into primary turbine costs, which by definition are insensitive to the temperature and pressure of the steam, and secondary turbine costs which are automatically paid for by neighboring components via requiring their purchase of utilization functions. The primary turbine cost formulae then result in equal units costs Xg of the bleed steam essergy for all of the feedwater heaters. Thus Xg is then constant with respect to temperature, thereby meeting the condition of thermo-economic isolation of the feedwater heaters with respect to the turbines. 

The gas turbine installed in the plant is an almost standard Typhoon from ABB Alstom Gas Turbines in Lincoln, England. Modified components are the combustors, the burners and the addition of an air bleed from the compressor, Furthennore, has a special design gas control module been developed to control the product gas, steam and nitrogen to the unit. 

Steam is extracted from the turbines at various "bleed points" and is condensed over tube bundles inside which the boiler feed-water mans Figure 4. 

Af a(j,j is the additional boiler fuel required when the heater is ou of service, cB is the unit cost of steam in the i - 1 bleed line, and cp is the unit cost of boiler fuel (coal). These available-energy flows are calculated in the usual manner and are given in Table II and reference (6). The unit costs are obtained with exactly the same techniques discussed by Reistad and Gaggioli (2)—by applying money balances to each component (boiler, high-pressure turbine,. . . ) of the system of interest to get the dollar flows and then by the subsequent division of the appropriate available-energy flows to obtain the unit costs. 

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