A far-sighted engineer
Rudolf Christian Karl Diesel was born on 18 March 1858 in Paris. At the tender age of 14 the son of a bookbinder decided on a career as engineer. After attending trade school and industrial school he went to Munich Technical University (Polytechnic Institute) and concluded his studies in 1880 with the best grade ever given for an examination since the university was founded. During his education in the engineering sciences the design engineer-to-be was particularly impressed by the thermodynamics lectures of Carl von Linde.
The contact with Linde had consequences: after completing his studies, Diesel went to work in the Linde refrigerating machine factory. But most of all, animated by Linde’s lectures he decided to develop a new engine featuring especially good thermal efficiency. In 1881, after a one-year period of traineeship, the young engineer was hired to work in Linde’s ice factory in Paris. Before the year was over, Diesel received a first patent for the manufacture of transparent ice.
During the following years, Rudolf Diesel increasingly focused on the work on his engine. In 1892 he took out a patent for his concept of a “new, rational heat engine”; patent DRP 67 207 “on a principle of operation and construction for internal combustion engines” was granted on 23 February 1893. In November 1893 Diesel modified and improved his first design and took out a second patent (DRP 82 168).
At Augsburg Machine Works (later MAN), from 1893 on Diesel developed a first test engine which he had running within a few months. But it would take four years from the beginning of work to design a successful prototype of an engine fit for series production. The Augsburg diesel engine factory was built in 1898 to produce the new power plant.
1897 – The diesel engine
Whereas the spark-ignition engine compresses a mixture of air and fuel, Diesel’s engine was supposed to compress the intake air, into which the fuel would be injected just before ignition. Subsequent to this mixture formation, which takes place entirely inside the cylinder, the fuel ignites spontaneously due to the heat produced by compression. On paper, Diesel’s calculations for this process showed extremely high compression pressures of as much as 253 bar; in reality, the pressures remained substantially below this level.
But considering that temperatures between 700 and 900 degrees Celsius were obtained by the compression of air in the cylinder, this fully sufficed to operate the new-type engine: with its very good ignition qualities, the diesel oil needed no additional starting aid to burn at these temperatures shortly after being injected. Before Rudolf Diesel finally decided on a middle distillate of petroleum as fuel, he experimented with various other substances, among other things with coal dust. However, the first prototypes then ran on kerosene, which is similar to diesel oil in many respects.
Compared with the petrol engine, the diesel engine has very good efficiency especially at partial load. It was this efficiency which convinced the first buyers of the new engine around 1900 – despite public criticism of Diesel’s concept. But the early engines did not prove durable enough yet in fact, and many customers returned their damaged engines. Particularly, the air compressor and the strainer-type atomiser used for fuel injection were susceptible to mechanical trouble. The inventor reacted by developing a new atomiser and improving the compression of the injection air by effecting compression in two steps.
The supply of fuel to the engine still called for a complicated process: a low-pressure pump delivered the fuel to the atomiser; from here, strongly compressed air blew the diesel oil into the cylinder as a fine fuel mist. This technology made the engines heavy and complex. Neither higher engine speeds, nor rapid reaction to changing loads were possible with this system.
Rudolf Diesel’s development efforts repeatedly were hampered by technical misunderstandings. Among other things, at the beginning of his work the engineer thought the spontaneous inflammation of the fuel was not vital, and he experimented also with sparkplugs. But the very first prototype of 1897 showed that the basic principle of this internal combustion engine had a great future. Indeed, Diesel’s engine soon established itself alongside the petrol engine as second type of internal combustion engine, though originally only in the form of a stationary engine.
All modern-day vehicular diesel engines follow the basic principle of these engines. However, Rudolf Diesel’s simple basic design has long since evolved into a technically sophisticated engine system. Solutions like common rail injection with injection pressures of up to 2000 bar, exhaust-gas turbocharging and ultramodern emission control systems and the combination of internal combustion engine with electric drive in the hybrid vehicle have made the diesel a powerful, economical, clean vehicle drive which still holds great potential for the future.
From stationary engine to marine diesel
Once Diesel had refined his concept to the point where it could be marketed, Augsburg Machine Works discontinued the production of steam engines in the course of the next few years and concentrated entirely on the manufacture of diesel engines. This step was quite in keeping with the market trend: the diesel engine, powerful competition for the steam engine, increasingly prevailed and superseded the steam engine. Between 1907 and 1909 alone, more than 1000 units with outputs from 15 kW to 74 kW (20 - 100 hp) were produced. But as a propulsion unit for transport purposes, prior to the First World War the new engine only saw use in ships, beginning in 1903.
Rudolf Diesel did not live to see the success of his engine as a propulsion unit for road and rail vehicles. The inventor, faced with financial ruin, disappeared from the postal steamship “Dresden” during a crossing from Holland to England in 1913. It is considered probable that the engineer committed suicide. Still, Diesel foresaw the potential of his technology: “I am firmly convinced,” he wrote in 1913, the year of his death, “that the automobile engine will come, and then I consider my life’s work complete.”
1910 – Marine diesels from Benz and Daimler
Benz and Daimler too built diesel engines for watercraft at the beginning of the twentieth century: Benz & Cie. delivered their first two four-stroke marine diesel engines in 1910. In September 1911 Benz then introduced a two-stroke diesel drive for marine use. This engine, “Patent Hesselman”, was based on a Swedish power unit which Aktiebolaget Diesels Motorer in Stockholm had been building since 1907. The Fram, an expedition and research vessel, was one of the ships equipped with the Benz two-stroke engine. The Fram was built back in 1892 for the Norwegian polar explorer Fridtjof Nansen. It served as an expedition vessel from 1893 until 1912. Roald Amundsen had the 132 kW (180 hp) Benz diesel installed for his journey to the South Pole from 1910 to 1912.
In September 1911, Daimler-Motoren-Gesellschaft (DMG) received an order for ten four-stroke air-injection marine diesels with an output of 74 kW (100 hp). The RM 20 274 engines were manufactured in DMG’s Berlin-Marienfelde factory; the first five units were delivered by Daimler in 1912.
Both companies also manufactured engines for submarines in the First World War. In January 1916 the DMG Marienfelde factory won a contract for twelve 221 kW (300 hp) six-cylinder diesel submarine engines. The first seven units of this model MU 256 were supplied to the customer in the same year. During this period Benz & Cie. also worked on powerful diesel engines for submarines, building eight S 6 Ln six-cylinder engines, each with 331 kW (450 hp), between 1915 and 1916.