Diesel, Rudolf

German thermal engineerwho invented the internal-combustion engine that bears his name. He was also a distinguished connoisseur of the arts, a linguist, and a social theorist.

Diesel, the son of German-born parents, grew up in Paris until the family was deported to England in 1870 following the outbreak of the Franco-German War. From London Diesel was sent to Augsburg, his father's native town, to continue his schooling. There and later at the Technische Hochschule (Technical High School) in Munich he established a brilliant scholastic record in fields of engineering. AtMunich he was a protégé of the refrigeration engineer Carl von Linde, whose Paris firm he joined in 1880.

Diesel devoted much of his time to the self-imposed task of developing an internal combustion engine that would approach thetheoretical efficiency of the Carnot cycle. For a time he experimented with an expansion engine using ammonia. About 1890, in which year he moved to a new post with the Linde firm in Berlin, he conceived the idea for the diesel engine (q.v.). He obtained a German development patent in 1892 and the following year published a description of his engine under the title Theorie und Konstruktion eines rationellen Wäremotors (Theory and Construction of a Rational Heat Motor). With support from the Maschinenfabrik Augsburg and the Krupp firms, he produced a series of increasingly successful models, culminating in his demonstration in 1897 of a 25-horsepower, four-stroke, single vertical cylinder compression engine. The high efficiency of Diesel's engine, together with its comparative simplicity of design, made it an immediate commercial success, and royalty fees brought great wealth to its inventor.

Diesel disappeared from the deck of the mail steamer Dresden en route to London and was assumed to have drowned.

Engine

A wide range of energy-conversion systems has been used experimentally and in automotive production. These include electric, steam, solar, turbine, rotary, and a variety of piston-type internal-combustion engines. The most successful for automobiles has been the reciprocating-piston internal-combustion engine, operating on a four-stroke cycle, while diesel engines are widely used for trucks and buses.

The gasoline engine was originally selected for automobiles because it could operate more flexibly over a wide range of speeds, and the power developed for a given weight engine was reasonable; it could be produced by economical mass-production methods; and it used a readily available, moderately priced fuel—gasoline. Reliability, compact size, and range of operation later became important factors. The advent of smaller cars brought a return to smaller engines, four- and six-cylinder designs rated as low as 80 horsepower, compared with the standard-size V-8 of large cylinder bore and relatively short piston stroke with horsepower ratings in the range from 250 to 350.

European automobile engines were of a much wider variety, ranging from 1 to 12 cylinders, with corresponding differences in overall size, weight, piston displacement, and cylinder bores. A majority of the models had four cylinders and horsepower ratings from 19 to 120. Several three-cylinder, two-stroke-cycle models were built. Most engines had straight or in-line cylinders. There were, however, several V-type models and horizontally opposed two- and four-cylinder makes. Overhead camshafts were frequently employed. The smaller engines were commonly air-cooled and located at the rear of the vehicle; compression ratios were relatively low. Increased interest in improved fuel economy during the 1970s and '80s brought a return to smaller V-6 and four-cylinder layouts, with as many as five valves per cylinder to improve efficiency.