Page 36: of Maritime Reporter Magazine (October 15, 1981)
Diesel Power Review —Paxman Diesel (continued from page 37) running with only the snorkel above the surface, when there can be a severe restriction on in- coming air and outgoing exhaust gases.
Paxman took full advantage of existing centrifugal compressor technology by using the super- charger rotor and involute from the Napier NA250 turbocharger.
The result, according to the com- pany, is an engine with an output similar to the turbocharged en- gine less the power required to drive the supercharger, but with much greater tolerance of chang- ing inlet depression and exhaust back pressures.
To maintain commonality with the standard Valenta engine, the supercharger drive has been add- ed to the free end of the engine.
The drive increases the crank-- shaft's 1,350 rpm to 24,000 in two stages. Primary speed in- crease is by epicyclic gears that drive into a fluid coupling before the secondary spur gear stage.
The first engine is undergoing comprehensive testing and has been run at outputs up to 1,518 kW at 1,350 rpm. A second unit is undergoing acceptance tests under submarine conditions at a
Ministry of Defence facility.
For further information on
Paxman diesel engines,
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Early next year Rolls-Royce plans to introduce a new 12-cyl- inder diesel engine, the CV 12, for installation in fast patrol craft and rescue vessels. This en- gine, in a 60-degree Vee configu- ration, can deliver 750 bhp at 2,100 rpm, enough power to drive a 50-foot boat at speeds up to 28 knots. Derived from the Rolls-
Royce Condor 12V1200 already used in tanks and generating sets, the reliability of the CV 12 has been proven.
The CV 12 has been designed to meet the needs of police and customs all over the world. The engine is also aimed at the search and rescue services.
With a net dry weight of about 4,000 pounds, the CV 12 will have a very favorable power/weight ratio. It will have twin turbo- charged, rear-mounted and twin high-mounted camshafts, gear- driven from rear gear trains.
The CV 12 cannot run on heavy fuel and must burn gas oil. But for specialized operations where high speed is essential and time is costly, the new Rolls-Royce en- gine should find a market.
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The first cargoships powered by SEMT-Pielstick diesel engines entered service more than 25 years ago and became the fore- runners of a fleet that at present aggregates more than 1,000 ves- sels propelled by the modern
PC2-5, PC3, and PC4 versions of the now famous Pielstick design.
During the past year SEMT-
Pielstick, along with other marine diesel designers, had to face the second fuel crisis, which had two main consequences: the cost of a ton of fuel increased above $200, and the oil refineries developed new processes and will supply lower quality fuels for marine uses.
To cope with these problems,
SEMT-Pielstick concentrated re- search and development on a de- crease in fuel consumption and use of the worst quality fuel. It has developed new engine models with higher cylinder output and, particularly, lower specific fuel consumption. These engines, with the same bore and stroke as their predecessors, have been designed with all the experience already gained with them.
The PC2-6, with bore of 400 mm and stroke of 460 mm, has a maximum continuous rating of 750 bhp per cylinder at 520 rpm, and specific fuel consumption of 136 grams per horsepower-hour at 85 percent of mcr. The PC4-2 (continued on page 42)
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