DIESEL, RUDOLPH (1858–1913)

Rudolph Christian Karl Diesel was a German thermal engineer and inventor of the high-efficiency internal-combustion engine that bears his name.

Much of Diesel's life and brilliant career was tragic—from his business failings, to his struggles to translate theory into practice, to his chronic physical and mental ailments. Yet his research and engine prototypes laid the foundation for one of the world's most efficient and widely used fossil fuel engine technologies.

Diesel was born to German Protestant parents. His father, Theodor, a bookbinder, emigrated from Germany to Paris in 1850, and five years later married Nuremberg-born Elise Strobel, a teacher of German and English. The couple had three children—Louise (b. 1856), Rudolph (b. 1858), and Emma (b. 1860)— and were strict disciplinarians. French was spoken in the Diesel home, and Rudolph's mother also taught him English. Rudolph had few friends, but took an interest in technology, reinforced by frequent visits to the Conservatoire des Arts et Métiers, a technical museum in Paris.

In 1870 the Diesels were forced to leave Paris by a government general expulsion order during the Franco-Prussian War, and in November Rudolph went to live with relatives in Augsburg, Germany. He enrolled in the royal commercial school and then studied at the city's industrial school. In a letter to his parents on his fourteenth birthday, Diesel declared his ambition to become an engineer. Perhaps inspired by a "fire piston" at the school (a device that caused a tinder to glow with compressed air), Diesel became intrigued with compression ignition. He was plagued with chronic health problems, especially headaches and insomnia, yet still excelled at his studies. His final exam grades in 1875 were the highest in the school's history.

Diesel's distinguished academic record drew the attention of Professor Karl Max von Bauernfeind of Munich's Techniche Hochschule, who offered Diesel a two-year scholarship. Ultimately Diesel spent four years in the school's mechanical-technical division, where he studied theoretical machine design under Carl von Linde (a leader in that field and in refrigeration science) Moritz Schroeter, and others. Graduating at the top of his class with a civil engineering degree in 1880, Diesel took a job at the Sultzer Brothers factory in Winterthur, Switzerland. Diesel was then hired by the Linde Refrigeration Company in Paris and soon went to work directly for Linde, traveling regularly to consult with clients.

By this time Diesel had become enamored with the "social question"—the social problems and class conflict fostered by industrialization. Perhaps in reaction to his father's earlier strong embrace of magnetic healing, Diesel rejected organized religion in favor of an increasingly popular rational humanism. One of Diesel's key motivations to invent a high-efficiency engine was to help relieve the burdens of the artisan class. Later (in 1903) he published a book called Solidarismus: Natuürliche wirtschaftliche Erloösung des Menschen (Solidarism: The Natural Economic Salvation of Man), in which he called for, among other things, worker-run factories.

In 1882 Diesel met Martha Flasche, a German. The couple married in November 1883 and for the remainder of the decade lived in Paris, where they had three children: Rudolph, Jr. (b. 1884), Hedy (b. 1885), and Eugen (b. 1889).

Diesel began work on an economical engine as early as 1880. The following year he took out his first patents—for machines to make clear ice. Throughout the remainder of the decade he worked on an ammonia vapor engine and (less rigorously) on a solar-powered engine. In 1889 he moved to Berlin to work as Linde's representative there. In 1890 or 1891 Diesel began to work out the theoretical basis for a constant temperature (isothermic) engine that would later evolve into the diesel engine. Diesel hoped to create a "universal" (flexible-fuel) engine that would operate on the cycle described by Nicolas Leonard Sadi Carnot and thus waste only about 20 to 30 percent of its energy through heat loss. In his model, the first downward stroke of the piston drew air into the cylinder. That air was then compressed to high pressure and temperature with the return (upward) stroke. With the second downward stroke, fuel was introduced at such a rate that the heat generated by its combustion would counterbalance the natural decline in temperature caused by the expansion of the cylinder space.

Diesel received a patent for his engine design in 1893, the same year he published a book on the subject, Theorie und Kunstruktion eines rationellen Waärmemotors (Theory and Construction of a Rational Heat Engine), which was translated into English in 1894. He then persuaded Machinenfabrik Augsburg (Augsburg Engine Works), led by Heinrich Buz, to form a syndicate with Krupp in April 1893 to manufacture a 2-cylinder, 50-horsepower engine. But Diesel and his backers were unable to produce a smoothly running prototype until 1897. For that to happen, Diesel modified many of the fundamentals of his original theoretical design. The working engine operated at much higher pressures (18 to 33 atmospheres); ran on kerosene (instead of any liquefied or pulverized fuel) and at a new fuel-air mix; used compressed air rather than solid injection; and, most importantly, did not operate at constant pressure.

After announcing the success and imminent commercialization of his engine at the June 1897 meeting of the Society of German Engineers, Diesel began seeking licensees throughout the industrialized world. Three German companies bought patent rights, as did several non-German firms and individuals, including brewing magnate Adolphus Busch in the United States. The Augsburg company managed to produce a reliable 60-horsepower model by 1902. But Diesel's foreign licensees continued to struggle, despite drawings and engineering assistance from Augsburg. Busch's company produced a mere 260 engines between 1902 and 1912, when its license expired, the diesel venture having cost the family millions of dollars.

Meanwhile, Rudolph Diesel's growing fame was haunted by a series of personal and business setbacks. Working to the point of exhaustion, he required months of recuperation in a sanitarium from late 1898 to early 1899 and again in 1901–1902. Some of his critics pointedly challenged the originality of his work, claiming that Diesel's engines operated on principals articulated by others, not on the inventor's original concepts. A poor financial manager, Diesel nevertheless maintained a lavish villa in Munich called Jugendstil. In 1913, when he boarded the steamship Dresden at Antwerp, bound for England, Diesel faced financial ruin. Sometime during the evening of September 29–30, he disappeared from the ship's deck. His body was recovered ten days later, and all signs pointed to suicide.

Diesel engines—heavier and more expensive to build per horsepower than gasoline engines, but much more durable and cheaper to operate—made rapid inroads in shipping in the 1920s, heavy-duty trucking and construction equipment in the 1930s, railroads in the 1950s, and began to gain ground in passenger automobiles following the energy crises of the 1970s.

David B. Sicilia

See also: Automobile Performance; Carmot, Nicolas Leonard Sadi; Diesel Cycle Engines; Diesel Fuel; Engines; Gasoline Engines.