Turbine horsepower

Many steam turbines do not have full-ported steam nozzles (see Chap. 17). The existing steam nozzles may then be exchanged for larger nozzles. An increase of nozzle diameter of 10 percent would increase the turbine horsepower by 20 percent. 

FIG. 12-8m WSAC configuration with electricity generation. A lower steam condensing pressure increases the turbine horsepower extracted. 

Most large centrifugal refrigeration compressors are driven by steam turbines. A gradual loss in refrigeration duty can be due to a reduction in turbine horsepower. An approximate method for calculating small changes in compressor horsepower is ... 

If steam conditions are normal, loss of turbine horsepower is likely due to fouling of the turbine wheels. This fouling may be removed by condensate washing. With the compressor running, pump clean steam con-... 

Motor-driven, multistage reciprocating compressors have reportedly been the most popular choice for aeroderivatives. Motor-driven, oil-fiooded screw compressors are also used in some cases. High horsepower, multistage centrifugal compressors, similar to those used at many pipeline compressor stations, may be required for the newer heavy-duty units if the distribution pipeline pressure is insufficient (see Pipelines). Gas turbines have more stringent fuel-gas specifications in terms of cleanliness than do gas-fired boilers. Thus oil- and water-knockout systems, coalescing filters, and fine-mesh filters are used. 

Change process to adjust specific gravity to design value, or throttle pump to reduce horsepower requirements. This will not correct problem with some vertical turbine pumps that have a flat horsepower-required curve. 

FIG. 29-11 Steam-turbine capability versus speed, To convert horsepower to kilowatts, multiply by 0,7457,... 

FIG. 29-16 Approximate horsepower loss for single-stage turbines. To convert horsepower to kilowatts, multiply by 0.7457 to convert inches to meters, multiply by 0.0254 and to convert pounds per square inch gauge to Idlopascals, multiply by 6.895. 

Development The following discussion relates specifically to the use of what could be called radial-inflow, centrifugal-pump power-recovery turbines. It does not apply to the type of unit nurtured by the hydroelecti ic industry for the 1 ge-horsepower, large-flow, low- to medium-pressure differential area of hydraulic water turbines of the Felton or Francis runner type. There seems to have been little direct transfer of design concepts between these two fields the major manufacturers in the hydroelectric field have thus far made no effort to sell to the process industries, and the physical arrangement of their units, developed from the requirements of the hydroelectric field, is not suitable to most process-plant applications. 

Since the exacd value of the hydraulic efficiency e, is never known, V/ can be taken as an approximation where e is the gross (hydraulic horsepower/brake horsepower) pump efficiency. Efficiencies of pump designs running as turbines are usually 5 to 10 efficiency points lower than those as pumps at the best efficiency point. 

Involved in producing the curves for Figs. 29-53 and 29-55 is a calculation of the so-called balance point at which the flow and revolutions per minute required by the recovery unit match those provided by the pump. If the recovery turbine is the sole driver (as for the lean pump of Fig. 29-54), both the speed and the brake horsepower of the recoveiy turbine and its driven pump must be the same at the so-called balance point. If there is a makeup driver and the recovery unit has available to it just the flow from the pump that it is driving, as for the pump of Fig. 29-56, then the speea ana capacity must match at the balance point. 

Now, at 3900 r/min and a head of 6,04 m (1982 ft), the required flow and generated brake horsepower of the recovery turbine are read. Since the horsepower of the lean pump and the recovery turbine are not identical, this entire process is repeated at another speed with the 3,03 mVmin (800 gaVniin), The difference in brake horsepower between the lean pump and the recovery turbine is then plotted against the speed for these two points, and a line is drawn between... 

FIG. 29-58 Head-horsepower-capacity characteristics of a lean pump tandem-connected with a power-recovery turbine operating as the sole driver. To convert gallons per minute to cubic meters per minute, multiply by 3.79 X 10 to convert horsepower to kilowatts, multiply by 0.746 and to convert pounds-force per square inch to megapascals, multiply by 6.89 X 10 . ... 

FIG. 29-59 Head-horsepower-capacity characteristics of a power-recovery turbine operating as the sole driver of a lean pump. If the total capacity of lean and semilean pumps exceeds the values indicated by available head limit, bypass must be used. Net recovery-pump head at 8.71 mVmin (2300 gal/min) is figured as follows ... 

Steam turbine performance is modeled using a standard steam flow versus horsepower map and valve position versus steam flow. The turbine inlet valve(s) is positioned by the governor system to maintain constant speed (or another parameter when synchronized). 

Eollowing initial installation in 1971, the Phase 1 expansion turbines have proven extremely reliable. The redesign effort of Phase 2 in 1992 incorporated improved aerodynamics and changed inlet guide vane profiles in the expansion turbines. This redesign yielded an additional. 40 to. 50 Bcf of gas per year without any increase in recompression horsepower. This translates to an increase in propane and butane production of an additional 3,600 to 4,500 bbl of liquid without an increase in electrical power consumption. 

Aeroderivative gas turbines eonsist of two basie eomponents an aireraft-derivative gas generator, and a free-power turbine. The gas generator serves as a produeer of gas energy or gas horsepower. The gas generator is derived... 

Axial-flow turbines are the most widely employed turbines using a eompres-sible fluid. Axial-flow turbines power most gas turbine units—exeept the smaller horsepower turbines—and they are more effieient than radial-inflow turbines in most operational ranges. The axial-flow turbine is also used in steam turbine design however, there are some signifieant differenees between the axial-flow turbine design for a gas turbine and the design for a steam turbine. 

Since aerothermal performance of compressors and turbines is very sensitive to inlet temperature and pressure variations, it is essential to normalize the aerothermal performance parameters such as flow, speed, horsepower, etc., to standard-day conditions. When these corrections to standard conditions are not applied, a performance degradation may appear to occur when in fact it was a performance change resulting merely from ambient pressure and temperature changes. Some of the equations for obtaining correction to standard-day conditions are given in Table 19-3. 

A prerequisite of a eleaning program is some kind of fouling detention system. Naturally, this system must eover the prime reason for eleaning. If the maehine is a gas turbine, the prime reason may be horsepower eapability, or it may be effieieney. On a eentrifugal eompressor, the prime reason for... 

Smaller turbines can vary widely in efficiency depending greatly on speed, horsepower, and pressure condi-... 

For steam turbines the cost should be correlated vs. horsepower w ith steam inlet and outlet pressure as secondary variables. 

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