Diesel engines torque it up
Manek Dubash looks at the diesel's long and honourable history
Following the recent announcement of the anniversary of the the very first internal combustion engine, made by Belgian Etienne Lenoir, it's worth taking a look at the ugly sister of the petrol-propelled motor, the diesel.
These days, almost every carmaker has one or more diesels in its product line-up. Not just a few either -- Peugeot Citroën has just announced that it's produced its 25,000,000th engine -- a diesel. The picture shows a modern two-stroke marine diesel engine -- said to be the most powerful in the world (more below).
But how did the diesel come about?
Rudolf Diesel
Born in Paris of Bavarian parents, Rudolf Diesel (1858-1913) studied at Munich Polytechnic where he was an outstanding mechanical engineering student. He began his career as a refrigerator engineer. For ten years he worked on various heat engines, including a solar-powered air engine.
Backed by Baron von Krupp and Machinenfabrik Augsburg Nurnberg Company in Germany, he began experimenting with a high-pressure ammonia engine. In 1892 Rudolf Diesel was issued a patent for a proposed engine that air would be compressed so much that the temperature would far exceed the ignition temperature of the fuel. In other words, no spark would be needed to ignite te mixture.
His backers provided him with engineers to help him develop an engine that would burn coal dust -- at the time, there were mountains of useless coal dust piled up in the Ruhr valley.
Experimental engines
The first experimental engine was built in 1893 and used high pressure air to blast the coal dust into the combustion chamber. While the prototype blew its cylinder head off but, four years later, Diesel produced a reasonably reliable engine. His ideas for an engine where the combustion would be carried out within the cylinder were published in 1893, one year after he applied for his first patent.
Further developments using coal dust as fuel failed. A compression ignition engine that used oil as fuel was successful and a number of manufacturers were licensed to build similar engines.
The original oil burning engines used very crude mechanical injection equipment so Rudolf Diesel again began using air blast to provide fuel atomisation as well as turbulence for improved air-fuel mixing. It was very successful and was employed in Rudolf Diesel's third engine, built in 1895. An engine very similar to those in use today, it was a four-stroke cycle with 450psi compression.
Diesel goes overboard
Rudolf Diesel's enjoyment of fame and fortune was marred by ill health, probably caused by exhausting legal battles over patent rights and unwise financial speculations. He lost a fortune and, while on a ship to England, he disappeared overboard.
In his notebook he had marked an X by that date, and speculation has it that he was pushed overboard for political reasons, as he was a vocal critic of Germany's foreign policy.
Diesels motor on...
Diesel's new engine, which his wife convinced him to name the engine after himself, was soon accepted throughout the world, and many of his engines were produced under licence.
The diesel's success can be attributed to many factors but its ability to produce prodigious amounts of torque for its capacity and its good fuel economy --which results from the fuel's greater energy-density over the more-refined petrol -- are key elements of the equation.
The most powerful diesel in the world is said to be the Wartsila-Sulzer RTA96-C turbocharged two-stroke. Designed for large container ships, it weighs 2,300 tons and pushes out 108,920hp and 102 rpm, and 5,608,312 lb-ft of torque, consuming 1,660 gallons of diesel per hour to do that. It has 14 cylinders with a total capacity of 25,480 litres.
More about this massive machine here: www.bath.ac.uk/~ccsshb/12cyl/
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