Rudolf Diesel

German engineer and inventor

• Born: March 18, 1858
• Birthplace: Paris, France
• Died: September 29, 1913
• Place of death: At sea, in the English Channel

Diesel’s greatest invention was the diesel engine, which was named after him. Its high thermal efficiency and the low cost of its fuel have made it an exceptionally economical engine that has found many applications—in automobiles, trucks, ships, and submarines, and for generating electricity.

Early Life

Born to Bavarian parents residing in France, Rudolf Diesel was exposed at an early age to the mechanical arts, both in his father’s leather-goods shop and at the nearby Conservatoire des Arts et Métiers. The Diesel family fled to London in September, 1870, in the face of growing anti-German sentiment during the Franco-Prussian War. After eight weeks there, his father, realizing there were too many mouths to feed, sent twelve-year-old Rudolf to Augsburg, Bavaria, to live with an uncle.

Diesel’s uncle enrolled him in a county trade school, where Diesel decided, at the age of fourteen, to become an engineer. At the trade school, he studied mathematics, physics, mechanical drawing, and modern languages. It was there also that Diesel realized that his life’s ambitions would come true only through hard work and a mastery of science. In the summer of 1875, Diesel advanced to the next level of education in the German system by enrolling, on a scholarship, in the new Technische Hochschule in Munich.

At the Technische Hochschule, Diesel heard the lectures of Professor Carl von Linde on the subject of heat engines. He was particularly struck by the low efficiency of the steam engine and began to think about ways to improve that efficiency. The firm grounding in thermodynamics that he received from Linde’s lectures later formed his approach to the problem of designing a better engine. In December, 1879, Diesel passed his final exams at the Technische Hochschule with honors and began his career as an engineer.

Life’s Work

Linde, who had so impressed Diesel in school, became his first employer. Diesel took a job as the Paris representative of the refrigeration machinery business Linde had founded. By working with heat engines and heat pumps, Diesel gained experience with the subject that most interested him: thermodynamics.

For ten years, Diesel worked in his spare time on various heat engines, including a solar-powered air engine. A heat engine produces work by heating a working fluid; the fluid then expands and exerts pressure on a moving part, usually a piston. Like many of his contemporaries, Diesel investigated the use of ammonia, ether, and carbon dioxide as substitutes for steam as the working medium in a heat engine. He tried to build an ammonia engine but found ammonia too difficult to handle (even small leaks proved hazardous to the health of nearby workers). He then turned to air as a working medium for two reasons: It was abundant and the oxygen in air could support combustion, thus eliminating the need for a separate firebox.

Having thoroughly studied thermodynamics, Diesel understood the Carnot cycle and attempted to apply it to his new heat engine, in the belief that it would improve the engine’s thermal efficiency. First published in 1824 by the French engineer Sadi Carnot, the Carnot cycle describes the ideal heat engine of maximum thermal efficiency and consists of four phases: isothermal (constant temperature) combustion, adiabatic (no loss or gain of heat) expansion, isothermal compression, and adiabatic compression to the initial state. In order to realize the highest possible efficiency, Carnot noted, the heat to be converted into work must be added at the highest temperature of the cycle, and it must not raise the temperature of the cycle.

The difficulty of adding heat (through combustion) while maintaining a constant temperature did not daunt Diesel; he felt confident that he could design such an engine—an ideal Carnot engine. His solution was to heat the air by compressing it with a piston inside a cylinder. At the top of the stroke, the air temperature would be at a maximum. He would then add a small amount of fuel, which the high air temperature would ignite. The heat produced by combustion would then be offset by the tendency of the air temperature to drop as the piston moved down and the air expanded, thus producing isothermal combustion. While theoretically correct, this idea met with many practical difficulties, the most formidable being that the engine had to work at extremely high pressures in order to achieve maximum efficiency.

In Diesel’s 1892 patent application for his engine, he listed isothermal combustion as the essence of his invention. A year later, Diesel published Theorie und Konstruktion eines rationellen Wärmemotors zum Ersatz der Dampfmaschinen und der heute bekannten Verbrennungsmotoren (1893; Theory and Construction of a Rational Heat Motor , 1894), in which he fully described his ideas and supported them with calculations and drawings. This book was important to Diesel as a way of promoting his ideas and thus gaining financial backing. With the endorsement of some of Europe’s leading thinkers in thermodynamics, Diesel gained the support of two industrial giants: Krupp and Maschinenfabrik Augsburg. Under the agreement that he reached with these firms, Diesel received a good salary and the use of their facilities. Despite this boost, it would take him four years of hard work to begin to realize his dream of a more efficient engine.

In the process of writing his book, Diesel realized that the ideal engine he had envisioned would be almost impossible to build because of the high air pressures required by the theory, which were well beyond the practice of the day. Thus, he began, in 1893, to scale down his ideas and to settle for good, but less-than-ideal, efficiencies. Even with the changes in his theoretical goals, building a working engine proved to be a challenge. His first experimental engine, tested in late 1893, exploded upon ignition of the fuel. His second engine ran under its own power for a minute, but only at idling speed. Not until 1897 did a prototype run smoothly, but it had neither the reliability nor the economy to be a marketable engine. Furthermore, it operated at a thermal efficiency far below what Diesel had originally set out to achieve.

Despite the remaining problems, Diesel announced in June, 1897, at a meeting of the Society of German Engineers that his engine was ready to be sold. The resulting fiasco almost ruined Diesel financially, brought him to the brink of a nervous breakdown, and gave his engine a bad name. Continued refinement of the engine over the next five years, however, restored the diesel engine’s reputation. It eventually gained a respectable share of the market, as the number of engines being sold every year increased steadily. By 1908, when Diesel’s basic patent expired, the diesel engine was firmly established as an important type of power plant.

By 1912, doubts were being raised as to Diesel’s role in the invention of the engine that bore his name. By some accounts, men other than Diesel—those who had taken his highly theoretical ideas and produced a working engine—deserved credit for the diesel engine. Those same critics saw Diesel as little more than a promoter. Diesel had always been high-strung (he was prone to migraines when under extreme stress) so it is not surprising that these criticisms stung him sharply. When he heard, in 1912, that a history of the diesel engine was being written, he countered with his own history, “Die Entstehung des Dieselmotors” (he published a book of the same title the following year).

In November, 1912, Diesel presented this paper at a professional meeting of engineers, at which two professors attacked him, pointing out that the diesel engine bore little resemblance to his original concept. At the same time Diesel was suffering these attacks upon his integrity, he was also suffering financial setbacks; bad investments had taken a heavy toll, despite good income from various sources. On the night of September 29, 1913, Diesel disappeared from a steamer while crossing the English Channel. His son later identified the effects taken from a body at the mouth of the Schelde River as those of his father. The death was ruled a suicide.

Significance

The diesel engine of today bears little resemblance to Rudolf Diesel’s original rational engine, but one is still quite justified in calling him the inventor. Few inventions spring from their creator’s mind without the need to refine and improve them, and Diesel’s brainchild was no exception. Significantly, Diesel kept a hand in his engine’s development throughout the lengthy development period. Furthermore, today’s engine retains three essential features of Diesel’s original concept. First, all diesel engines are high-compression engines that use air as the working medium. Second, fuel is still injected into the cylinder at the end of the compression stroke. Third, it is still the heat of the compressed air that ignites the fuel.

Diesel engine production grew dramatically after Diesel’s death. It is difficult to estimate the number of diesel engines in service, but the fact that millions are built each year throughout the world helps put their importance in perspective. The diesel engine’s high thermal efficiency and the low cost of diesel fuel combine to make it an extremely economical engine. As a result, diesel engines have found a growing number of applications such as submarines, ships, locomotives, heavy road and off-road vehicles, passenger cars, and electric generating plants. These engines aptly carry the name of the man who worked so hard to make them a reality.

Bibliography

Auer, Georg. “Renaissance Man Set the Automobile Industry on Fire.” Automotive News 75, no. 5908 (December 18, 2000): 20H. A tribute to Diesel, describing how his interest in thermodynamics led to his creation of a thermodynamic engine. Explains how the engine has been used to power ships, pumps, cars, and other machines and vehicles.

Bryant, Lynwood. “The Development of the Diesel Engine.” Technology and Culture 17 (July, 1976): 432-446. A carefully documented case study of the nature of invention, development, and innovation. Contains a brief but useful discussion of the claims against Diesel in 1912. Highlights the many difficulties Diesel encountered in developing his engine and the many modifications to his original idea. Contains footnotes.

‗‗‗‗‗‗‗. “Rudolf Diesel and His Rational Engine.” Scientific American 221 (August, 1969): 108-117. A careful examination of the intellectual evolution of the diesel engine. Well illustrated and written for the layman, the article explains each step in Diesel’s progress toward the diesel engine of today. Contains an especially useful section, with graphs and illustrations, of the Carnot cycle, Diesel’s starting point.

Cummins, C. Lyle, Jr. Diesel’s Engine. Wilsonville, Oreg.: Carnot Press, 1993. A biography written by a mechanical engineer. In addition to providing an overview of Diesel’s life, the book describes the work of licensees who transformed Diesel’s engine into a reliable source of power for numerous products and vehicles.

Diesel, Eugen. “Rudolf Diesel.” In From Engines to Autos: Five Pioneers in Engine Development and Their Contributions to the Automotive Industry, by Eugen Diesel, Gustav Goldbeck, and Friedrich Schilderberger. Chicago: Henry Regnery, 1960. Written by Diesel’s son, this is, nevertheless, a reasonably objective account of Diesel’s life and work. Details of engine development follow a concise, ten-page summary of his early life. Suffers from a lack of documentation, but is notable for the insights it provides into Diesel’s personality.

Grosser, Morton. Diesel: The Man and the Engine. New York: Atheneum, 1978. A very readable account of the development of the diesel engine from Diesel’s original idea through the date of the book’s publication. Generally dependable in technical details. Contains a glossary and a list of books for further reading, as well as photographs and illustrations.

Nitske, W. Robert, and Charles Morrow Wilson. Rudolf Diesel: Pioneer of the Age of Power. Norman: University of Oklahoma Press, 1965. Biography with two chapters at the end on the diesel engine in the modern world. Not totally reliable. Written mostly from secondary sources and without footnotes; as such, it offers little new information about Rudolf Diesel or his engine.

Thomas, Donald E., Jr. Diesel: Technology and Society in Industrial Germany. Tuscaloosa: University of Alabama Press, 1987. Biography of Diesel, placing his invention within the context of technological, economic, and societal developments in nineteenth century Germany.