This invention relates to a hot gas generator for the production of hot combustion gases from liquid combustibles such as light fuel oil wherein the combustion gases, for example transfer their energy to heating water or similar material in a heat exchanger which is ancillary to the hot gas generator.
In conventional oil burners as they are used, for example for operating hot water boilers, soot arises or occurs particularly when the boiler is started up and also when the draft in the chimney varies. This soot causes fouling of the boiler or of other ancillary heating surfaces which results in greatly diminishing the heat transfer from the heating gases to the media which are to be heated, for example the boiler water. Furthermore, carbon monoxide and unburned hydrocarbons are produced which cause noxious odors from the oil burner due to the unburned hydrocarbons and also increased heating costs due to incomplete combustion.
Hot gas generators have been developed which atomize the fuel oil by means of a nozzle and, like in a conventional oil burner, mix it with an air stream which is produced by a blower, and burn the liquid fuel in a combustion chamber, the combustion chamber being a part of the hot gas generator. In these known generators a cylinder encloses the combustion chamber, such cylinder having at one end thereof an exhaust port for the hot gases and at the other end a port where the atomized liquid fuel and air are introduced. The cylinder is surrounded by two concentric ring-shaped cylindrical air conduits, and the blower is first led to the exhaust port end of the combustion chamber cylinder. From that end the blower air passes back to the fuel nozzle end of the inner air conduit along the hot combustion chamber cylinder, where then the preheated blower air enters into the combustion chamber cylinder and is admixed with the atomized liquid fuel. These known hot air generators have the disadvantage that it is never possible to keep the combustion chamber completely free of residues, so that after some time, soot precipitates and fouling of the combustion chamber occurs with all its disadvantages.
Accodingly, an object of the present invention is to provide a hot gas generator which is capable of producing soot-free combustion of fuel oil or similar fuels which is practically free of excess air, thus being stoechiometrical, needs very little space, and is not objectionable from the standpoint of pollution control. Such a generator will produce a hot gas of a very high temperature which will make it furthermore possible to heat, for example boiler aggregates for a central heating system, where said aggregates will not need any boiler combustion chamber, but will consist only of a very compact ancillary heating surface. Such heating surfaces may also be ribbed because no soot can precipitate upon them. Such ribs cannot be built into conventional oil burners because the soot would have to be removed periodically which is impossible because the heating surfaces are not easily accessible.
The present invention encompasses, in one embodiment, a hot gas generator having a cylindrical combustion chamber which has at one end an exhaust port and at the other end fuel nozzle means. The cylindrical combustion chamber is surrounded by two concentric cylindrical air conduits which are connected to each other at the exhaust end of the combustion chamber. Also the inner air conduit is connected to the inner space of the cylindrical combustion chamber at the fuel nozzle end of the combustion chamber, and the external air conduit is connected to a blower. A baffle plate is disposed at the fuel nozzle end of the cylindrical combustion chamber, such baffle plate filling completely the whole internal diameter of the cylindrical combustion chamber. The baffle plate is provided with openings for the air which streams or passes from the inner air conduit into the inner space of the cylindrical combustion chamber. The fuel nozzle means introduces fuel through an opening in the center of the baffle plate into the cylindrical combustion chamber.
As a particularly advantageous characteristic, openings in the baffle plate are arranged in a plurality of concentric circles and these openings are shaped and arranged in such a way that the air receives an angular momentum or rotary motion around the longitudinal axis of the cylindrical combustion chamber as it passes through such openings. The baffle plate which completely fills the entrance portion of the cylindrical combustion chamber renders possible a stabilization of the flame and results in an extraordinarily advantageous soot-free combustion of the liquid fuel. The realization of satisfactory soot-free combustion is also remarkably increased by a further characteristic of the present invention wherein the cylindrical combustion chamber is provided over its whole circumference at a distance from the baffle plate with one or more rows of holes for the introduction of air from the inner air conduit into the internal space of the cylindrical combustion chamber. A part of the blower air which is preheated by the cylindrical combustion chamber while passing through the inner air conduit is introduced through these holes as hot secondary air and is admixed at the outer rim zones of the fuel oil fog cone so that complete and satisfactory combustion of the fuel oil droplets at the rim zone is obtained and unburned hydrocarbons are precluded in the exhaust gases which leave the hot gas generator. Furthermore, the realization of completely pollution-free combustion is obtained by providing, according to another characteristic of the present invention, swirl vanes for the production of a helicoidal air stream within the inner air conduit. This arrangement materially improves the preheating of the blower air by the cylindrical combustion chamber, so that very hot primary air enters through the baffle plate into the cylindrical combustion chamber and also very hot secondary air is mixed into the outer rim zones of the fuel oil fog cone. Also during start-up of the hot gas generator complete and absolutely soot-free combustion of the liquid fuel occurs because the cylindrical combustion chamber is heated very quickly by the flame and thereby also provides very quickly a high preheating of the blower air.
Other features which are considered characteristic of the invention are set forth in the appended claims.
Although the invention is illustrated and described in relationship to specific embodiments, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.