Rudolf Christian Karl Diesel (English: /ˈd iː z əl ˌ – s əl /, German: [ˈʁuːdɔlf ˈkʀɪsti̯an kaʁl ˈdiːzl̩]; born March 18, 1858, and died September 29, 1913) was a German inventor and mechanical engineer. He is best known for creating the diesel engine, which uses diesel fuel. Both the engine and the fuel are named after him.

Early life and education

Rudolf Diesel was born on March 18, 1858, at 38 Rue Notre-Dame-de-Nazareth in Paris, France. He was the second child of Elise (born Strobel) and Theodor Diesel. His parents were immigrants from Bavaria who lived in Paris. Theodor Diesel worked as a bookbinder, a person who binds books. He left his hometown of Augsburg, Bavaria, in 1848. He met his wife, who was the daughter of a merchant from Nuremberg, in Paris in 1855. He later became a manufacturer of leather goods in Paris.

After Rudolf was born, he was sent to live with a farming family in Vincennes for the first nine months of his life. When he returned to his family, they moved to a flat at 49 Rue de la Fontaine-au-Roi. At this time, the Diesel family faced financial challenges. Because of this, young Rudolf worked in his father’s workshop and delivered leather goods to customers using a barrow. He attended a school that taught both Protestant and French subjects. He became interested in social issues and technology. Rudolf was a strong student and received a bronze medal from the Société pour l'Instruction Elémentaire in 1870. He planned to attend the Ecole Primaire Supérieure that year.

In 1870, the Franco-Prussian War began. Because of this, Rudolf’s family was sent to England and settled in London. There, Rudolf attended a school that taught in English. However, before the war ended, Rudolf’s mother sent him to live with his aunt and uncle, Barbara and Christoph Barnickel, in Augsburg, Germany. She wanted him to learn German and attend the Königliche Kreis-Gewerbeschule, a vocational school where his uncle taught mathematics. Rudolf was enrolled at the Technische Hochschule, a technical high school.

At age 14, Rudolf wrote a letter to his parents stating he wanted to become an engineer. After finishing his basic education in 1873, he joined the newly established Industrial School of Augsburg. He graduated at the top of his class. Two years later, in 1875, he received a merit scholarship from the Royal Bavarian Polytechnic of Munich. He accepted the scholarship, even though his parents wanted him to start working instead.

Career

Rudolf Diesel studied under Professor Carl von Linde in Munich. He could not graduate with his class in July 1879 because he became very sick with typhoid fever. While waiting to take his next exam, he worked as an engineer at the Sulzer Brothers Machine Works in Winterthur, Switzerland. Diesel graduated in January 1880 with the highest academic honors and returned to Paris, where he helped Linde design and build a modern refrigeration and ice plant. One year later, Diesel became the director of the plant.

In 1883, Diesel married Martha Flasche and continued working for Linde, receiving many patents in Germany and France.

In early 1890, Diesel moved to Berlin with his wife and children—Rudolf Jr., Heddy, and Eugen—to manage Linde’s research and development department and join several company boards. Because he could not use his patents for personal purposes while working for Linde, he expanded his work beyond refrigeration. He first studied steam engines, researching how to improve thermal and fuel efficiency. He built a steam engine using ammonia vapor, but it exploded during testing and nearly killed him. His experiments with high-compression cylinder pressures tested the strength of iron and steel cylinder heads. One head exploded during a test, and Diesel spent many months in the hospital, followed by health and eyesight problems. It was during this time that he began thinking about creating a diesel engine.

Since studying under von Linde, Diesel had worked on designing an internal combustion engine that could reach the maximum theoretical thermal efficiency of the Carnot cycle. In 1892, after years of research, he completed his theory and received the German patent DRP 67207. In 1893, he published a book titled Theory and Construction of a Rational Heat-Engine to Replace the Steam Engine and the Combustion Engines Known Today, which explained his ideas. By summer 1893, he realized his initial theory was incorrect and filed a new patent application for the corrected version.

Diesel understood thermodynamics and the limits of fuel efficiency. He knew that steam engines wasted about 90% of the energy in fuel. His engine designs aimed to achieve much higher efficiency.

Unlike engines that use external ignition to ignite a fuel-air mixture, Diesel’s engine compressed air inside the cylinder until it became hot enough to ignite fuel on its own. This design made the engine smaller, lighter, and did not require additional fuel sources. Fuel efficiency in his engine was 75% higher than the 10% theoretical efficiency of steam engines.

In his engine, fuel was injected at the end of the compression stroke and ignited by the high temperature from compression. From 1893 to 1897, Heinrich von Buz, director of Maschinenfabrik Augsburg, supported Diesel’s testing and development. The Krupp firm also provided assistance.

Diesel’s design used compression ignition instead of spark plugs, like in gas engines. His engine could run on biodiesel or petroleum-based fuels. Compression engines are about 30% more efficient than traditional gas engines because compressed air raises the temperature in the combustion chamber, creating higher pressure and faster movement of pistons.

Biodiesel is often made from synthesis gas produced by gasifying waste cellulose or extracting lipids from algae. This process usually involves combining vegetable oils and algae with methanol through a chemical reaction called transesterification. Many companies have developed different methods to produce biodiesel.

The first successful diesel engine, Motor 250/400, was tested in 1897. It had a 25-horsepower four-stroke, single vertical cylinder compression system. This engine revolutionized the industry and quickly became popular, earning Diesel significant income through royalties. The engine is now displayed at the German Technical Museum in Munich.

In addition to Germany, Diesel received patents for his design in other countries, including the United States (1895, 1898).

Disappearance and death

On September 29, 1913, Rudolf Diesel boarded the ship SS Dresden in Antwerp while traveling to a meeting with the Consolidated Diesel Manufacturing company in London. He had dinner on the ship and then went to his cabin around 10 p.m. He told the crew to wake him at 6:15 a.m. the next day, but he was never seen again. In the morning, his cabin was empty, and his bed had not been slept in. His nightshirt was neatly placed, and his watch was visible from the bed. His hat and folded overcoat were found near the back of the ship.

After Diesel disappeared, his wife, Martha, opened a bag he had given her before his trip. He had told her not to open it until the following week. Inside, she found 20,000 German marks in cash (about $120,000 today) and papers showing their bank accounts had almost no money. In a diary he carried, a cross was drawn next to the date September 29, 1913. This might have meant he was dead.

Ten days after his disappearance, the crew of the Dutch pilot boat Coertsen found a man’s body floating in the Eastern Scheldt. The body was so badly decomposed that it was hard to identify. Because of heavy weather, the crew did not bring the body aboard. Instead, they took personal items, such as a pill case, wallet, ID card, pocketknife, and eyeglass case, from the clothing and returned the body to the sea. On October 13, these items were confirmed by Rudolf’s son, Eugen Diesel, as belonging to his father. Five months later, in March 1914, Martha Diesel seemed to disappear in Germany. She died in Brandenburg on April 16, 1944, at the age of 85.

There are several theories about Diesel’s death. Some biographers, like Grosser (1978) and Sittauer (1978), believe he died by suicide. Others think he was murdered because he refused to give the German military exclusive rights to use his invention. Diesel had boarded the Dresden to meet with Royal Navy representatives to discuss using diesel engines to power British submarines. Another theory suggests that his death was a trick to hide his escape to Britain. It is claimed he later worked in Canada for the Vickers shipyard in Montreal and helped improve submarine diesel engines. Because of limited evidence, the cause of his disappearance and death remains unknown.

In 1950, Magokichi Yamaoka, founder of Yanmar, a Japanese diesel engine company, visited West Germany. He learned there was no tomb or monument for Diesel. Yamaoka and others began planning a tribute. In 1957, on the 100th anniversary of Diesel’s birth and the 60th anniversary of the diesel engine’s development, Yamaoka dedicated the Rudolf Diesel Memorial Garden (Rudolf-Diesel-Gedächtnishain) in Wittelsbacher Park, Augsburg, Bavaria. This was where Diesel studied and first developed his engine.

Legacy

He was added to the Automotive Hall of Fame in 1978.

After Diesel’s death, his engine was improved and became a key replacement for steam piston engines in many uses. The Diesel engine needed stronger construction than gasoline engines, so it was not widely used in aviation. However, it became common in other areas, such as stationary engines, farm equipment, off-road machinery, submarines, ships, and later, trains, trucks, and modern cars.

Diesel engines use fuel more efficiently than other internal combustion engines used in vehicles, which means more heat is changed into energy that moves machines.

Diesel was interested in using coal dust or vegetable oil as fuel. His engine was even run on peanut oil. Although these fuels were not better choices at the time, in 2008, higher fuel prices and worries about how much oil was left led to more use of vegetable oil and biodiesel.

The main fuel used in Diesel engines is diesel fuel, which comes from refining crude oil. Diesel fuel is safer to store than gasoline because its flash point is about 81°C (145°F) higher, and it will not explode.

The asteroid 10093 Diesel, located in the main asteroid belt, was discovered in 1990 by Eric Walter Elst at the European Southern Observatory. It was named in his honor.

In a book titled Diesel Engines for Land and Marine Work, Diesel wrote, “In 1900 a small Diesel engine was shown by the Otto company, which, because the French Government suggested it, was run on arachide [peanut] oil. It worked very well, and few people knew it. The engine was built for regular oils and, without changes, was run on vegetable oil. I recently repeated these experiments on a large scale with full success and confirmation of the earlier results.”

Works

• Rudolf Diesel: Theory and Design of a Rational Heat Engine as a Replacement for the Steam Engine and the Combustion Engines Known Today. Published by Springer in Berlin in 1893. ISBN 978-3-642-64949-3 (Theory and Design of a Rational Heat Engine at Google Books)
• Rudolf Diesel: The Origin of the Diesel Engine. Published by Springer in Berlin in 1913. ISBN 978-3-642-64940-0
• Rudolf Diesel: Solidarismus: Natürliche wirtschaftliche Erlösung des Menschen. Published by Oldenbourg in Berlin/Munich in 1903. (PDF archived on the Wayback Machine on May 10, 2021)