Walter drive

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Steam generator of a Walter drive system
Turbine of a Walter drive system

The Walter drive was developed by Hellmuth Walter on behalf of the Reichsmarine / Kriegsmarine at the Germania shipyard in Kiel from the mid-1930s .

The aim was to develop a system that would generate enough electricity for the electric motors even under water, where diesel engines were not to be used. The accumulators commonly used had too little capacity. An attempt was made to convert hydrogen peroxide into superheated steam with the help of a catalyst and then to generate electricity using a turbine.

Cold process

Further considerations initially led to the cold process , in which hydrogen peroxide is sprayed from fine nozzles onto a catalyst made from manganese (IV) oxide (manganese dioxide). The resulting high- pressure steam-oxygen mixture was fed into a turbine and was therefore available as drive energy.

Hot procedure

The hot process was tried out in 1936. This system consisted of a decomposer or reactor and a downstream combustion chamber, a separator and a steam turbine. The decomposer consisted of a pressure vessel in which a block of porous potassium permanganate or manganese (IV) oxide (manganese dioxide) was inserted horizontally (the catalyst). From the lid of the vessel, hydrogen peroxide was sprayed onto the catalyst by means of several nozzles, where it decomposed into its constituents, water vapor (550-600 ° C) and oxygen. This gas mixture was able to flow through the porous catalyst into the lower area of ​​the reactor. From there there was a pipe connection to the downstream combustion chamber. The oxygen-vapor mixture now entered the combustion chamber in the area of ​​the combustion chamber cover and was increased there with finely atomized fuel to a 2000 ° C flame. In order to prevent the combustion chamber neck from burning through, the neck was cooled with cooling water and the water was allowed to enter the hot gas flow by means of fine bores. This enormous steam generation (35–40 t / h) made it possible to operate a 7500 HP steam turbine. Because of the severe damage to the turbine blades (due to abrasion from the catalyst stone), a cyclone- like separator was later placed between the combustion chamber outlet and the turbine inlet. The steam outlet of the turbine was connected to a condenser in order to increase the efficiency of the turbine and also to be able to reuse the precious condensate (distilled water). The CO 2 content was pumped overboard by means of a compressor and completely absorbed by the sea water, which enabled a bubble-free journey. A considerably smaller system of the same type was also used on combat aircraft, with the combustion chamber being mounted horizontally on the tail unit. A separator and condenser were of course not required, because the steam and gas ejected directly served as a supporting mass , as with all rocket engines. However, the system was only switched on for a short time during combat operations in order to increase the speed considerably. The aforementioned performance could only be achieved when using 90 to 94 percent hydrogen peroxide concentration.

Indirect method

In addition to the direct hot process, the indirect Walter process with a closed steam circuit for the turbine was tested, with the steam being generated in a heat exchanger that was heated by the gases emerging from the combustion chamber. This process had a lower specific consumption of hydrogen peroxide (“T-substance”), but was more complex in terms of space and weight than the direct process.

Fuel consumption

The Walter drive had a high specific consumption of hydrogen peroxide. The consumption was about:

  • 5 kg / kWh and more with the cold method
  • 2.35 kg / kWh for the hot direct method
  • 1.85 kg / kWh in the hot process using a condenser (through this, hardly any exhaust gases were exposed to the immersion pressure, so that the pressure gradient in the turbine was greater.)
  • 1.32 kg / kWh for the indirect method

use

During test drives in 1940, the test submarine VS 80 equipped with the Walter drive reached an underwater speed of 28.1  knots . The surface speed achieved with this boat was not specified in the test documents; the hull, however, was optimized for underwater travel. Type Wa 201 and Type Wk 202 were submarine classes with the Walter drive. Grand Admiral Erich Raeder stopped their further development; the Walter turbine was also affected. Only when Hitler accused Raeder of incompetence (the capital ships achieved hardly any success, the submarines very much), Raeder then resigned and was replaced by BdU Rear Admiral Karl Dönitz , the further development of the submarines was carried out with great effort. Two boats of each type were built for operational endurance testing, type Wa 201 U 792 and U 793 and type Wk 202 U 794 and U 795 .

After the increased losses during the submarine war in May 1943, the Navy planned several large submarine classes with Walter propulsion (types XVII , XVIII and XXVI ) because of this overwhelming mileage ; however, they were no longer completed. Only three boats of type XVII B were put into service in 1944, but were no longer used. The Type XVIII boats developed as carriers for the Walter drive were put into service as conventional electric motor boats due to the not yet fully completed Walter drive (outwardly, the Type XVIII resembles the actually built Type XXI ).

U 1407 , a Type XVII B boat built by Blohm & Voss , came to England after the war and continued to operate as a test boat under the name HMS Meteorite until 1946 (British name for the Walter drive: HTP High Test Peroxide ). From 1951 to 1959, the Soviet Union used its own boat, the S-99 , for testing purposes, but put it out of service after a series of accidents. In 1956 and 1958 the British test boats Explorer and Excalibur were put into service. It remained the only British boats with HTP propulsion. During the tests, explosions in the drive caused a series of damage, so that the crew of the Explorer sarcastically renamed their ship "Exploder". Hellmuth Walter himself designed a deep-sea submarine for diving depths of up to 5000 m in the 1960s . The design was given the name Stint and was supposed to be operated with a Walter turbine in the cold process, but was not implemented.

The Walter drive was never built in series due to a lack of practical experience with this drive system, but is still regarded as a good drive system that is independent of the outside air ( AIP for air-independent propulsion ). The changed submarine development made a very noisy, fast submarine superfluous. The trend was clearly towards slower, almost silent boats that were difficult to locate.

The Walter propulsion principle was used both in the launch catapult of the V1 cruise missile and as a steam generator for the fuel turbo pumps of the rocket engine of the V2 rocket.

The principle was also used to drive the Me 163 rocket fighter (cold process in the test vehicle Me 163A; hot process in the Me 163B operational aircraft).

In order to be able to produce the required large quantities of highly concentrated hydrogen peroxide, the Navy built two large production plants under the code name Schickert-Werke in Bad Lauterberg and Rhumspringe from 1938 onwards.

literature

  • Karl Günther Strecker: From the Walter submarine to the wafer machine. The story of a great German engineer and the successful conversion of his armaments company. Köster, Berlin 2001, ISBN 3-89574-438-7 ( contributions to peace research and security policy 2).
  • Eberhard Rössler , Fritz Köhl: Submarine type XVII. From the original to the model. (Walter submarines), a picture and plan documentation. Bernard & Graefe, Bonn 1995, ISBN 3-7637-6009-1 .
  • Alexander Szandar: Desirable wishes . In: Der Spiegel . No. 18 , 2008, p. 50 ( online - secret protocols, WEU ban on nuclear propulsion and Walter propulsion for German "surface and underwater vehicles").
  • Emil Kruska and Eberhard Rössler: Walter U-Boats - Defense Scientific Reports. JFLehmanns Verlag, Munich 1969.

Web links

Individual evidence

  1. ^ Project description FZG 76, Fi 103, V 1 ( Memento from June 10, 2015 in the Internet Archive )
  2. ↑ Schickert-Werke at www.zwangsarbeit-in-niedersachsen.eu