This Date in History: Rudolf Diesel Patents the Diesel Engine

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On August 9, 1898, German inventor Rudolf Diesel was awarded a U.S. Patent for his internal combustion engine.  116 years later, Diesel’s engine is more popular than ever. 

Rudolf Diesel applied for his US patent in 1895, describing a process that “consists in first compressing air or a mixture of air and neutral gas or vapor to a degree producing a temperature above the igniting-point of the fuel to be consumed, then gradually introducing the fuel for combustion into the compressed air while expanding against resistance sufliciently to prevent an essential increase of temperature and pressure, then discontinuing the supplyof fuel and further expanding without transfer of heat.”

In Diesel’s day, the most common method to make power was through steam. But steam generates tremendous heat energy, about 90 percent of which was lost to the environment. Diesel understood thermodynamics, and put his knowledge to work developing an engine with a much higher efficiency ratio.

In basic terms, Diesel’s engine only injected fuel at the very end of the compression cycle — as opposed to the conventional internal combustion engine which introduces fuel in the intake cycle. Diesel’s design ignited fuel through the heat generated by compression.

Diesel died under mysterious circumstances. On September 29, 1913, while aboard the steamer Dresden, Diesel disappeared. His cabin was empty, and his hat and overcoat were neatly folded.

Ten days later, sailors discovered the corpse of a man floating in the North Sea near Norway. The body was unrecognizable, but Diesel’s son identified the man’s personal effects as those of his father. His biographer suggests that his death was self-inflicted, a theory buoyed by the fact that his wife received a bag from her husband with instructions not to open it for a week. The bag contained 200,000 German marks.

Craig Fitzgerald

Craig Fitzgerald

Writer, editor, lousy guitar player, dad. Content Marketing and Publication Manager at