Gambar halaman
PDF
ePub

of stalling the engine on sudden overloads. Without a battery reserve, an engine is seriously handicapped on economy. This is well illustrated by a load curve from a gas-driven interurban railway plant,* noted below; with peaks ranging well up to the capacity of the engine, the average loading was only about onethird rating in the long run.

Automatic Gas Regulator-As the steam boiler operates on a constant-pressure system, so does the producer, and in addition on a constant quality of gas. But, whereas steam is enormously

[graphic][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][merged small]

expansive as compared to feed-water, the volume of gas made is practically proportional to that of the air blast. A steaming boiler has large storage capacity which tides it over sudden demands until the fire can respond; in the producer, the blast must follow the changes in output, volume for volume. With hand regulation this is difficult, if not impossible, without the 'intervention of auxiliary storage in the shape of a gas holder. In the intermittent type of plant producing water and air gas alternately, which for power purposes must be thoroughly mixed, a holder is an

*Warren and Jamestown Street Railway. See Table V.

absolute necessity; but in the continuous-blast plant the holder is not necessary if automatic control of gasification is provided.

Such a form of control may be readily worked out, and is employed on all Westinghouse producers. The seat of control is the pressure at the nozzle of the steam injector blower supplying air to the producer. This steam supply is varied by throttling according to the demand for gas through the action of a pressure regulator shown in Figure 11. This may be either of the diaphragm or of the gasometer type, and is connected to the main header supplying gas to the engines. As the demand for gas increases, the pressure falls and the regulator opens the blower throttle D, until enough gas is made to bring the pressure

[ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small]

back to normal. These changes take place almost instantly, but without violent fluctuations.

Tests were recently made at East Pittsburgh to prove the action of this regulator. A by-pass to atmosphere was used to obtain wide ranges of producer output, as well as instantaneous changes. By means of the movable weight on lever B, the regulator was set for about one inch water pressure. Figure 12 summarizes the results. With the exception of a slight "wink," due to valve opening while charging coal, the regulator held the gas pressure to within half an inch of mean pressure, even when instantaneously loading and unloading the producer, which is the

20

severest test that could be found. It must be remembered that gas engines are equipped with individual pressure regulators to insure gas at atmospheric pressure at the mixing valves. Although these are still provided in the field, it has been found possible, on the test floor at East Pittsburgh, to run engines. on test with only the producer regulator in the line, which

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][ocr errors]
[ocr errors][ocr errors][merged small]

PRODUCER BLOWER TEST

-%

Pressure Characteristic

[blocks in formation]

oop

500 HP Non Bit Producer

300HP+

[blocks in formation]

FIG. 13-TEST OF GAS REGULATOR

holds the gas pressure sufficiently uniform to maintain the proper mixture.

The variation in the output of the producer by this regulator has no noticeable effect on the heat value of gas. During the 2-hour test, the gas averaged 131 B. t. u. per cubic foot, varying only 3.75 per cent from the mean. Variation in output

[graphic][subsumed][subsumed][subsumed][subsumed][ocr errors][merged small][subsumed][ocr errors][ocr errors][subsumed][subsumed][merged small]

FIG. 14-PLAN OF PRODUCER PLANT, FIRTH-STIRLING STEEL COMPANY

proved to be a function of the regulator movement, and consequently the blower pressure, as shown by Figure 13. That it is not a linear relation is due entirely to the characteristics of the injector type of blower, in which the velocity of steam and the resulting entrainment of air is proportional to the square of the pressure head. This apparatus, in doing away with the gas holder with the extra ground space and piping necessary, reduces the producer plant to its simplest form-producer and scrubber in one self-contained unit.

Typical Plant-In the small but excellently-designed plant of the Firth-Stirling Steel Company, now operating the ordnance

BIN

FIG. 15-SECTION PRODUCER PLANT, FIRTH-STIRLING STEEL COMPANY

works at Giesboro Point, below Washington, may be found a good example of the simplicity characterizing this style of producer plant. See Figures 14 and 15. Owing to the extreme necessity of uninterrupted service, a duplicate equipment has been provided throughout. Note the simplicity of piping, which is entirely above ground. Each gas unit consists of a water-sealed producer and wet coke scrubber, with a three-way valve between, connecting with the purge stack. The plant is designed for continuous running, and ashes are removed at intervals through the water seal without disturbing its operation. An excellent form of coal-handling apparatus is shown in the sectional drawing. A

« SebelumnyaLanjutkan »