Combustion chamber boiler

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Class 41 steam locomotive with a DR Reco boiler. The Ifs type mixing preheater can be recognized by the trapezoidal structure above the smoke chamber.

The combustion chamber boiler is a special design of the boiler of a steam locomotive . Contrary to what the name suggests, the combustion chamber is not primarily used for combustion, but rather to make better use of thermal radiation .

Structure / mode of operation

The combustion chamber protrudes into the long boiler as an extension of the actual firebox . Because of the shortening of the pipe length, the pipe heating surface is reduced, but the particularly effective radiant heating surface is increased (radiant heating surface is about six times as effective as the pipe heating surface). This means that the area that is not heated by convection of the hot gases but directly by the more effective heat radiation of the furnace is larger.

A further advantage of the combustion chamber boiler is the fact that the greater distance between the pipes and the grate or the flames results in less thermal stress on the pipes and the rear pipe wall. In addition, entrained sparks are given more time to burn out. Shifting the focus forwards was also an often desired side effect.

Development in Germany

The Deutsche Reichsbahn-Gesellschaft (DR), whose design principles were very conservative, rejected the combustion chamber boiler, although it had long been state of the art in the USA, for example . It was not until 1937 that the 05 003 was the first German and the only locomotive commissioned by the DR to receive such a boiler, because the coal dust intended for firing on this locomotive required a relatively long combustion path. After the Second World War, the Deutsche Bundesbahn retrofitted many locomotives to fire boxes with combustion chambers or completely newly built combustion chamber boilers. At the Deutsche Reichsbahn in the GDR, too, the entire so-called reconstruction program was based on newly built, standardized combustion chamber boilers. The resulting locomotive boilers - incorrectly called Recoke boilers - were always newly built combustion chamber boilers. By completely welding the boilers, the weight of the boilers could also be reduced and the construction improved. The welding of the rear boiler, which is required for the use of the combustion chamber, also made it possible to use a U-shaped base ring instead of a solid base ring with a rectangular cross-section as the lower standing boiler end. Due to its rigidity against heat-induced changes in shape of the firebox walls, the massive base ring was a frequent cause of firebox damage in riveted boilers.

For locomotives standard gauge the German National Railroad was built in 1958, three different types of boilers, which were adjusted to be reconstructed locomotives:

The latter design was the most powerful steam locomotive boiler of the Deutsche Reichsbahn with a maximum steam delivery of 16.8 t per hour and a heating surface load of 75 kg generated steam per hour and square meter. The most striking signs of the Deutsche Reichsbahn's Reco boilers were the large, trapezoidal mixing box of the mixing preheater system type IfS on the top of the smoke chamber and the row of wash hatches above and in front of the combustion chamber.

For the fully-welded high-performance boilers ordered by the Deutsche Bundesbahn, the basic specification required an evaporation capacity of 75 to 85 kilograms of steam per hour and square meter of evaporation heating surface. The boiler of the DR series 01.10 , like the boiler of the DB series 10, was designed for a maximum evaporation capacity of 85 kilograms per square meter and hour. Due to the tight grate area of ​​these DB high-performance boilers, which, in contrast to the boilers of the Deutsche Reichsbahn, limits the boiler output, the theoretically possible maximum evaporation capacity of 17.8 tons of steam per hour in operation could only be fully used by converting to oil firing . The newly built DR series 45 boiler may be viewed as the boiler with the highest output for the German Federal Railroad ; With a heating surface load of 81 kilograms per square meter and hour, it developed over 22 tons of steam per hour and enabled the machine to have over 3000 hp on the tow hook.

  • Type 39E boiler during repairs in the boiler shop (Meiningen, 2003)

  • View into the combustion chamber of the 39E. In preparation for the repair, parts of the firebox walls have already been slit and the pipes removed from the boiler. The slotted surfaces will be completely renewed later.

  • For repairing opened rear shells of a 39E. The combustion chamber protrudes into the long boiler. The standing boiler and firebox wall are removed below the combustion chamber except for the U-shaped floor ring.

  • For comparison: cut-open boiler without combustion chamber

The Henschel company not only developed the successful boilers for the 23 series of the DB or the replacement boiler for the 01.10, but also demonstrated the ability to build very powerful boilers for locomotives intended for export. The SAR class 25 boiler of the South African Railway is probably the most powerful locomotive boiler that has ever been built in Germany. The modern combustion chamber boiler with fire box boiler tubes was able to generate around 25 tons of steam per hour.

Individual evidence

  1. ↑ Arge. for training aids on behalf of the main administration of the Deutsche Bundesbahn (ed.): Railway teaching library of the Deutsche Bundesbahn, Volume 134, Steam Locomotive Studies . 2nd edition, Josef Keller, Starnberg 1959, p. 67 f., P. 301 ff.
  2. ^ Manfred Weisbrod, Hans Müller, Wolfgang Petznick: Steam Locomotive Archive , Volume 1 . transpress VEB Publishing House for Transport, Berlin 1976, p. 23
  3. ^ Manfred Weisbrod, Hans Müller, Wolfgang Petznick: Steam Locomotive Archive , Volume 1 . transpress VEB publishing house for transport, Berlin 1976, p. 29

See also