M method

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Principle of the MAN-M process
M-piston of a 4 VD 14.5 / 12-1 SRW

The M process , short for center sphere process , is a mixture formation process for diesel engines in which the fuel is injected into a spherical combustion chamber distributed across the walls. It is counted among the direct injection processes . Today the M-procedure is considered out of date. It was mainly used for stationary engines and engines for commercial vehicles; there are no car engines with the M process.

Working principle

In contrast to a conventional injection process, in which the fuel should remain as far away from the combustion chamber wall as possible in order to increase efficiency, with the M process the fuel is applied specifically to the wall of the combustion chamber, which is designed as a spherical depression in the piston crown (see picture on the right) . The fuel is injected tangentially to the combustion chamber wall at low pressure through a one-hole or two-hole nozzle, whereby it is largely distributed as a film on the wall surface. In order to initiate ignition, a small part of the fuel is air-distributed. It is only due to the high gas temperature that prevails in the combustion chamber after ignition that the fuel evaporates from the combustion chamber wall and is quickly mixed with the intake air by a strong air vortex, causing it to burn. Since the speed of the fuel approaches 0, the speed of the air must be increased in order to achieve a high relative speed between fuel and air. This is achieved with twisted air inlet ducts.

The background to the M process is that the fuel, which is still liquid, is not exposed to the high combustion chamber temperature due to wall-distributed injection, i.e. it is not “processed”, which means that the pressure increase in the cylinder when combustion starts is very low and combustion takes place slowly, which is what happens noticeable in a low combustion noise. In addition, the wall-distributed injection leads to good air utilization, which means that engines with the M process produce very little soot. In this way, high mean pressures can be achieved up to the smoke limit.

The disadvantage of the M-process is that, as a result of the principle, high flow and heat transfer losses occur, which reduces efficiency and thus increases fuel consumption. In addition, the piston and cylinder head in particular are exposed to greater thermal stress, which is why engines with the M process are not well suited for compressor or turbo-charging . In the partial load range , the mixture formation behavior is poor due to the falling temperatures, which means that more hydrocarbons are emitted.

Multifunctional properties

Since the M process is based on the principle that the fuel is applied to the colder combustion chamber wall and is not directly exposed to the hot gas, the process is not only suitable for conventional diesel fuels, but also for petroleum fractions that are heated at temperatures of 40 ° C (313.15 K. ) boil up to 400 ° C (673.15 K) as well as motor gasoline with up to 86 octane. A further development of the M process is the FM process (F for external ignition), in which the diesel engine-typical features of internal mixture formation and qualitative regulation have been retained, but the mixture is ignited in a controlled manner with a spark plug. Therefore, engines with FM processes are strictly speaking neither gasoline nor diesel engines, but are counted among the engines with hybrid combustion processes. Compared to the classic M process, the exhaust gas behavior is improved. With the FM method, the spark plug is arranged with two parallel pin electrodes on the combustion chamber wall opposite the injector. Alternatively, a spark plug with three ground electrodes can be positioned at the edge of the fuel jet.

history

The engineer Kurt Blume started thinking about the M process in 1940, and in 1941 these considerations were first recorded in writing. The M process was then brought to series production by Joachim Siegfried Meurer at MAN . The first engines with the M process ran on the test bench in 1954 and 1955. The M process was licensed in the GDR in order to use it for the industrial engine 4 VD 14.5 / 12-1 SRW . The FM method derived from the M method was used from the late 1960s to the mid 1980s.

Individual evidence

  1. ↑ a b c d e v. Basshuysen, Schäfer: Handbook Internal Combustion Engine: Basics, Components, Systems, Perspectives . P. 761
  2. ↑ Braess, Seiffert: Vieweg Handbook Automotive Technology . P. 233
  3. ^ A b Hans Christian Graf von Seherr-Thoß: The technology of MAN commercial vehicle construction in MAN Nutzfahrzeuge AG (Ed.): Performance and way: To the history of MAN commercial vehicle construction . P. 438
  4. ↑ Richard van Basshuysen (Ed.): Otto engine with direct injection - process systems development potential , 3rd edition, Springer Vieweg, Wiesbaden, 2013, ISBN 9783658014087 , p. 21
  5. ↑ Gaier, Commercial Vehicles in the GDR, Volume 2 . P. 100
  6. ^ ATZ, Automobiltechnische Zeitschrift, Volume 75. Franck, 1973. P. 152
  7. ↑ Kirchberg: Plastic, sheet metal and planned economy: the history of automobile construction in the GDR . P. 757
  8. ↑ Gaier, Commercial Vehicles in the GDR, Volume 2 . P. 89
  9. ↑ v. Basshuysen: Otto engine with direct injection and direct injection: petrol, natural gas, methane, hydrogen p. 23

literature

  • J. Siegfried Meurer : The MAN-M combustion process . ATZ Automobiltechnische Zeitschrift, Franck, Volume 58, 1956. No. 4 p. 92 u. 98; No. 5, p. 127 and 133.
  • J. Siegfried Meurer: Further development of the MAN-M and multi-fuel engines . ATZ Automobiltechnische Zeitschrift, Franck, Volume 59, 1957. No. 7. P. 179 u. 182
  • MAN Nutzfahrzeuge AG (Ed.): Achievement and way: On the history of MAN commercial vehicle construction , Springer, Berlin / Heidelberg, 1991. ISBN 978-3-642-93490-2 . P. 436 ff.
  • Richard van Basshuysen, Fred Schäfer (Ed.): Handbook Internal Combustion Engine: Fundamentals, Components, Systems, Perspectives , 8th edition, Springer, Wiesbaden, 2017. ISBN 978-3-658-10902-8 . Chapter 15.1, p. 761
  • Robert Bosch GmbH (Ed.): Diesel injection technology . Springer, Berlin / Heidelberg, 1993. ISBN 978-3-662-00904-8 . P. 8
  • Heinrich Dubbel : Dubbels Taschenbuch für den Maschinenbau , 12th edition, Springer, Berlin / Heidelberg, 1961. ISBN 978-3-662-41644-0 . P. 175
  • Hans-Hermann Braess, Ulrich Seiffert (eds.): Vieweg Handbook Motor Vehicle Technology , 6th edition, Vieweg + Teubner, Wiesbaden, 2012. ISBN 978-3-8348-8298-1 . P. 233
  • Peter Kirchberg: Plastic, sheet metal and planned economy: the history of automobile construction in the GDR , 2nd edition, Nicolai, Berlin, 2001. ISBN 978-3-87584-027-8 . P. 485 and 757
  • Achim Gaier: Commercial vehicles in the GDR, Volume 2 . 2nd edition, Schrader, Stuttgart, 2002. ISBN 9783613872103 . P. 89 and 100
  • Richard van Basshuysen: Otto engine with direct injection and direct injection: Otto fuels, natural gas, methane, hydrogen , 4th edition, Springer, Wiesbaden, 2016. ISBN 9783658122157 . P. 23