First of all the theory
In 1880, Rudolf Diesel was appointed director of the French branch of the refrigeration company owned by Professor Carl von Linde. At the same time, he initially worked on various cooling processes and, on his own initiative, built an ammonia engine which, although capable of running, failed to fulfil expectations. Finally he had the idea that with internal combustion engines, a higher compression should lead to better use of heat and fuel savings.
The burning idea
From 1890, he managed the technical office of the company in Berlin. While he was there, he continued to pursue this idea and eventually applied for a patent for his "burning" idea of the rational heat engine.
What was unusual about Diesel's approach was that his initial thoughts related purely to theoretical facts and figures. When looking for the ideal implementation of the Carnot cycle, he overlooked the fact that his drawings could not be implemented with the status of technology at that time. For that reason Heinrich von Buz, Director of Maschinenfabrik Augsburg, initially rejected Diesel's application.
Buz and Diesel
Diesel had to revise his drafts once again and eventually wrote to Heinrich von Buz, stating that "a deviation from the ideal process provides the possibility of designing engines that can also be constructed with today's means". After this, there was nothing standing in the way of co-operation between Buz and Diesel.
The initial tests in Augsburg
On 23 February 1893, Rudolf Diesel received the patent certificate number 67207 with the title "Working method and design of internal combustion engines".
At almost the same time, he concluded a contract with Maschinenfabrik Augsburg for the construction of an experimental engine. Buz was also able to convince the company Friedrich Krupp to join in the research for the new engine. The laboratory was set up at Maschinenfabrik Augsburg. In the coming years, Rudolf Diesel dedicated himself solely to the realisation of his engine.
On the verge of despair
Several years were required for the testing phase. Problems arose again and again, which meant that by 1897, a total of six series of tests had to be carried out. The inventor was close to despair several times, but Heinrich von Buz was always at Rudolf Diesel's side and supported him despite the numerous setbacks.
The official acceptance test
On 17 February 1897, Professor Moritz Schröter from the Technical University of Munich carried out the official acceptance test on the engine and determined an efficiency of 26.2%. Such a high value had never before been attained by any engine.