After-chamber

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The mixture formation process with post-chamber is a process of direct fuel injection for diesel engines . It was developed by MAN and was first presented in 1932. It was used by various manufacturers and was on the market until the 1940s. Today it is obsolete and is no longer used in engine construction. It represents an approximation of engines with indirect fuel injection, as it is technically related to the air storage process . Because of the poor efficiencythe post-chamber process is referred to in the specialist literature as the “fall from grace” of MAN engine development. The reason for the development of the post-chamber process was the better running and cold start behavior, which was rated higher than favorable fuel consumption, since diesel engines had to assert themselves against the still widespread smooth-running Otto engines with good starting properties in the first years of diesel truck construction .

construction

In the post-chamber engine, the combustion chamber is designed as a funnel-shaped "cannon" at an angle at the top of the cylinder head, into which the fuel is injected directly with a nozzle. Below the injection nozzle is the so-called post-chamber, which is connected to the lower end of the "cannon" with a small hole. During the compression stroke of the piston, the air in the combustion chamber and in the post-chamber is compressed; the compression volume of the post-chamber makes up approx. 20 to 25% of the total compression volume. The fuel is injected very early during the compression stroke, and a small part of it also reaches the post-chamber. The fuel ignites in the main combustion chamber and in the post-chamber at the same time, which forces the air out of the post-chamber into the main combustion chamber, where it ensures an improved swirling of fuel and air. In contrast to pre-chamber machines, post- chamber machines do not have to be pre-annealed , as the fuel is not applied to a cold combustion chamber wall and therefore ignites reliably even when it is started. Post-chamber motors are suitable for rotational frequencies up to 2400 min −1 .

literature

  • Friedrich Sass (Hrsg.): Construction and operation of diesel engines: A textbook for students. First volume: Basics and machine elements , Springer, Berlin / Heidelberg, 1948. ISBN 978-3-662-00419-7 , p. 100 ff.
  • Olaf von Fersen (ed.): A century of automobile technology. Commercial vehicles. VDI-Verlag, Düsseldorf 1987, ISBN 978-3-662-01119-5 , p. 131
  • Walter Knecht: History of internal combustion engine development in Switzerland , O. Baldinger, 1993. P. 186 ff.

Individual evidence

  1. a b c v. Heels: a century of automotive engineering. Commercial vehicles. P. 131
  2. a b c Sass: Construction and operation of diesel engines: A textbook for students. P. 101
  3. ^ Knecht: History of internal combustion engine development in Switzerland, p. 188