Page 43: of Maritime Reporter Magazine (March 2002)

(continued from page 27) crankshaft strength limited engine power. Not until the introduction of higher quality steel were high output powers possible.

Use of the compound was followed by the triple expansion steam engine, considered reliable by the 1880s. In these engines, which needed a minimum of 120 psi to operate, the steam was exhausted from the high-pressure cylinder to the intermediate cylinder, then to a low-pressure cylinder. A triple expansion engine could operate at around 200 psi with a con- denser vacuum of 26 inches of mercury.

The cranks were placed at 120° to give more uniform torque to the shaft. To operate with a higher pressure and offer smoother power, quadruple expansion engines were built as well. However, triple expansion technology dominated until the advent of the steam tur- bine.

Steam Turbine

Invented in the 18th century, the rotary engine was not practical until 1884 when Sir Charles Parsons invented a turbine to operate an electrical generator.

The first turbine-powered vessel was the HMS

Turbinia in 1897. This direct-drive engine operated at a relatively slow speed. The main problem with turbines was their high rotation speed — which required use of a reduction gear — and the fact that they were not reversible.

Yet, because of their favorable size-to-power ratio, steam turbines had been adopted for use in many large express passenger liners by the early 1900s. Canadian

Pacific's 21,517-gross ton trans-Pacific liner Empress of Canada, which entered service in 1922, typified the period. Her propulsion plant consisted of two sets of

Brown-Curtis turbines employing double reduction gearing, each set consisting of four separate turbines in series. During the war the turbine reigned supreme, dri- ving First World War ships from large battleships to destroyers.

During the 1930s, manufacturers were preparing for war production. The main industrial wartime strategies were achieving standardization and developing increased manufacturing capacity and efficiency. Tech- nology temporarily regressed in favor of producibility.

Because of an acute shortage of turbine, gear, and large diesel engine manufacturing capability, the approximately 3,000 ships built during WWII were powered with triple-expansion reciprocating steam engines. The 2,700 Liberty ships supplied by the Allies served the war effort in an exemplary fashion. Despite a significantly behind-the-times fuel rate of about 1.2 lb/ihp-hr, the ships' plants were capable of being oper- ated by relatively inexperienced personnel. ^ORTELBOER

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ANCHORS

CHAINS encour- ~ age exploita- tion of better fuel rates and alleviate the anticipated shortage of steam turbines and gears, a few experimental diesel installa- tions took place just before and after the start of WWII. The direct-drive,

British-patented, opposed-piston Doxford diesel engines were built in 3-, 4-, and 5-cylinder versions with 6,000 and 7,500 bhp continuous ratings.

These became the popular, American-made, large diesel engines, built by the Sun Shipbuilding and Dry- dock Company of Pennsylvania.

Postwar Progress

After WWII, the unending quest for reduced weight and machinery space continued. By the late 1940s most steam merchant ships were turbine powered.

Striving for heat and space efficiency inevitably led to pressure-fired boilers, or supercharged steam genera- tors. In such boilers air from a turbine-driven compres- sor, powered by furnace exhaust gas was fed to the fur- nace at about 65 psi/490°F.

In the early 1960s U.S. operators of ocean-going ves- sels began to move toward increased speed and cargo system improvements. Grace lines' four Santa Mag- dalena-class (with a 20.5 knot speed) became the mod- ern cargo carriers of the day. Both plants, which were of about 18,000 shp maximum, had two oil-fired D- type water tube boilers supplying 600 lb steam to a sin- gle set of cross compound steam turbines driving dou- ble reduction gears and a single propeller. This design represented a conservative standard for U.S. power plants for the next decade.Relief from wartime restric- tions led to more experimentation. More than 1,000 nearly new Liberty ships were targeted as working test beds and outfitted with a steam turbine, a free piston gas turbine, a regenerative gas turbine, or a diesel engine. The most notable of the Liberties was the John

Sergeant converted in 1956 with a 6,000 shp open- cycle regenerative gas turbine, double-reduction gears, and a controllable, reversible-pitch propeller.

Gas Turbine

When the U.S. Navy made the transition to light dis-

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Tel.: +31 (0)10 429 2222 tillate VJ Fax:+31 (0)10 429 6459 fuel in ^^^^^ [email protected] the late 1960s www.wortelboer.n and early 70s, the shift paved the way for a transition to more diesel- and gas turbine-pow- ered combatants. By effectively equalizing the cost of the basic propul- sion fuel, the cost advantage of the steam plant was lost and a logistical advantage for gas turbine power was born.

The gas turbine was touted as a compact, fuel-effi- cient plant that offered high power per unit weight.

While the concept predates the 20th century, it was not until after WWII that gas turbines began to find wide acceptance and application in power generation and propulsion. The first U.S. gas turbine-propelled mer- chant ship was the above-mentioned John Sergeant. Its low compression ratio, heavy-duty, industrial-type gas turbine's fuel consumption rate was a respectable 0.52 lb/shp-hr. By 1965 the Navy had installed many gas turbines for electric and auxiliary power, but only 78 for propulsion. One major step was the Navy's com- bined-diesel-or-gas propulsion plant for patrol motor gunboats, using diesel engines for cruising and a GE

LM1500 gas turbine of 14,000 hp for high-speed oper- ations.

Diesel Engine Drives

Throughout the 1920s and 1930s the diesel engine found increasing favor with many ship owners because it was more economic to operate. Scandinavian ship

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