With a high-pressure boiler the results are even more dangerous because of the greater release of energy. Water tubes in Royal Navy boilers were checked for blockage by carefully dropping numbered balls down the curved tubes.Ī sudden steam leak into the firebox is perilous enough with a conventional boiler – the fire is likely to be blasted out of the firebox door, with unhappy results for anyone in the way. This was a major drawback with the early water-tube boilers, such as the Du Temple design, tested on the French Nord network in 19. Scale deposited inside the tubes is invisible, usually inaccessible, and a deadly danger, as it leads to local overheating and failure of the tube. The next difficulty is that of scale deposition and corrosion in the boiler tubes. The steam drums and their interconnecting tubes are of relatively small diameter with thick walls and therefore much stronger. For high steam pressures the water-tube boiler is universally used. Structural strength requirements in the boiler shell make this impractical it becomes impossibly thick and heavy. It was not simply a matter of building a normal fire-tube boiler with suitably increased strength and stoking harder. High-pressure locomotives were much more complicated than conventional designs. A simpler way to increase the acceptance temperature is to use a modest steam pressure and a superheater.ĭisadvantages of high pressure Complexity However, experiments in this direction were always defeated by much increased purchase and maintenance costs. Thus it has often been considered that high pressure is the way to go to improve locomotive fuel efficiency. However, both implementations are dead ends: the first one is limited by the loading gauge while the second one tends to be self-defeating because of frictional losses in the greatly increased volumes of exhaust steam to be handled. The latter can be implemented in two ways: bigger cylinders to allow the exhaust steam to expand further and/or condensing the exhaust to further lower the rejection temperature. For a steam engine, the former means raising steam at higher pressure and temperature, which is in engineering terms fairly straightforward. There are two options: raise the acceptance temperature or lower the rejection temperature.
This was quantified by Nicolas Léonard Sadi Carnot.
raising steam in the boiler) as far as possible from the temperature at which it is rejected (i.e. Maximising the efficiency of a heat engine depends fundamentally upon getting the temperature at which heat is accepted (i.e.
0 kommentar(er)
