MW-50
MW-50 was the abbreviation for a methanol - water mixture with a mixing ratio of 50:50, which was used by the German Air Force in the Second World War to increase the performance of supercharged aircraft engines . Power units that used MW-50 were mainly used in fighter planes such as the Bf 109 or Fw 190 , which enabled the pilots to briefly operate the engines with increased power ("special emergency power") in critical situations.
Mixing ratio
MW-50 consisted of 50% methanol, 49.5% water and 0.5% protective oil. This mixture had a specific weight of 0.9 kg / l and was cold-resistant down to −50 ° C. In addition to MW-50, MW-30 and EW-30 ( ethanol instead of methanol) were also used to a lesser extent . MW-30 consisted of 30% methanol, 69.5% water and 0.5% protective oil. This mixture had a specific weight of 0.95 kg / l and was cold-resistant down to −18 ° C.
functionality
The principle is based on the possibility of increasing the performance of supercharged engines through charge air cooling . A variant of charge air cooling is the internal cooling of the charge air by injecting a liquid into the charger inlet, the liquid extracting heat from the heated charge air through evaporation . The cooled gas mixture contains a larger amount of substance in a given volume, so that more oxygen molecules per unit volume are available for the combustion of the fuel. This improves the filling level of the engine; Due to the increased mean pressure , a higher power can be delivered. Pure water injection would be more effective than MW-50 injection because water has a higher heat of vaporization . MW-50 develops about half the heat of evaporation as pure water. The addition of methanol was done to prevent uncontrolled ignition (the so-called "knocking" ) and freezing at great heights. Furthermore, due to its calorific value , the methanol increased the heat conversion during combustion and reduced the corrosion in the engine. MW-50 was injected at a pressure of 4 bar .
commitment
The increase in performance was permissible for up to ten minutes with sufficient engine cooling; before it was used again, the engine had to be operated at a lower power level for at least five minutes. Unless the engine was overheating, only the life of the spark plugs was reduced. Later, the operation of engines with good cooling performance was extended to up to 20 minutes. The gain in performance at a consumption of 150 l / h was around 300 hp, depending on the engine. The Fw 190 D could operate the injection for a total of 40 minutes with its 115 liter tank.
The use of this technique was only up to the full height pressure sense of the motor, since above this level the loader is no longer the required maximum capacity could supply of air for combustion of the fuel.
See also
literature
- Gersdorff, Grasmann, Schubert: Aeroengines and jet engines . 3. Edition. Bernard & Graefe Verlag Bonn, 1995, ISBN 3-7637-6107-1 .