Vaporizer-Preheaters.—As has been stated before, there are vaporizers internal or external, relatively to the generator.
Internal Vaporizers.—The Deutz apparatus (Fig. 106), for example, consists of an annular cast-iron tank mounted above the retort of the generator.
The hot gases given off by the burning fuel travel around this tank and vaporize the water which it contains. The air drawn in by the suction of the engine enters through an opening located above the tank, travels over the surface of the water which is being vaporized, and thus laden with steam passes to the ash-pit.
The tank in question is supplied with water by means of a cock having a sight feed, located on the outside, and the level is kept constant by means of an overflow tube leading to the ash-pit. It is well to bend this tube and to place a funnel on its lower member. The amount of overflow may thus be regulated.
These vaporizers are simple and take up little room; but they are open to the apparently well-founded objection that they heat up slowly and require a considerable time to produce the steam necessary to enrich the gas, this being due to the relatively large mass of cast-iron and the amount of water contained therein.
The Pierson vaporizer (Fig. 101) and the Chavanon vaporizer (Fig. 115) both consist of an annular tank forming the base of the generator. Steam is formed near the outlet of the ashes, which, as has been described above, leads to the outer air. The development of
steam is regulated by mechanical means controlled by the suction of the engine.
Fig. 115.—Chavanon producer.