Boiler using combustible fluid

Abstract

A fluid fuel boiler having a combustion chamber having an opening for introducing a combustion supporting gaseous fluid. A burner introduces a liquid fuel into the combustion chamber mixed with the gaseous fluid for combustion thereof. Water-heating flow paths are disposed circumferentially and axially of the combustion chamber. Axial hot gas flow paths deliver hot gases from a downstream portion of the combustion chamber to a plurality of nozzles for diverting some of the hot gases along axially spaced paths in a direction circumferentially of the combustion chamber. These latter hot gas flow paths are immersed in the flow paths of the water to improve heat transfer.BACKGROUND OF THE INVENTIONThis invention relates generally to boilers and more particularly to a new and improved modular boiler.It is known that the coefficient of heat transfer of a conduit for transferring heat from hot gases to water passing through a boiler is a function of the turbulence of the gases in the heat-transfer or convection conduits. In known boilers, this turbulence of the gases is relatively slight and is increased in practice only by the interposing of baffles distributed along the heat-transfer or convection conduits. In order to lower the temperature of the gases to about 100.degree. to 150.degree. C at the time that they are evacuated towards the stack, the length of the heat-transfer or convection conduits must be relatively large. Since the price of boilers is substantially proportional to the weight of the cast iron used for their manufacture, the great advantage which may exist in increasing the power and reducing the length of the heat-transfer or convection channels by increasing the heat-transfer coefficient will be readily understood.Boilers whose combustion chamber is connected to the heat-transfer or convection channels by nozzles which generate head losses are available on the market. These nozzles have the effect of considerably increasing the velocity of the hot gases due to their small cross section, producing a large increase of movement of the hot gases in the heat-transfer or convection channels. Localized loss in head created by each nozzle makes it possible to pressurize the combustion chamber and make the range of velocities of the gases, their temperature and their pressure less dependent on external conditions.Unfortunately in these embodiments the nozzles are concentrated in the same place in the combustion chamber and each of them injects the hot gases into a separate heat-transfer or convection channel. The concentrating of the nozzles at the same place produces thermal stresses which are very poorly distributed due to the presence of hot points at the place of concentration of the nozzles. Since the injection of the gases takes place near the upstream end of each channel, the secondary movements of the gases which are produced by the injection rapidly decrease due to the friction of the gases in these channels. This decrease and the fact that each nozzle injects the gases at one end of each channel causes the heat transfer coefficients to decrease between the upstream and downstream ends of the heat-transfer or convection channels.SUMMARY OF THE INVENTIONAn object of the present invention is to remedy these drawbacks of the known boilers, at least in part, so as to increase the power and the coefficient of heat transfer. The measures taken have the effect of decreasing the size of the boiler and therefore its weight as compared with the existing boilers of comparable power.For this purpose, the present invention relates to a fluid fuel boiler comprising a combustion chamber formed of sidewalls, a bottom, and a cover which has an opening for a burner. A water circulation circuit surrounds the combustion chamber and connects a source of cold water to a hot water collector. At least one heat-transfer or convection conduit is in contact with the circuit and connects the combustion chamber to at least one exhaust gas collector. This boiler is characterized by the fact that the chamber is placed in communication with the conduit by a plurality of injection nozzles disposed circumferentially of the combustion chamber and in some embodiments also axially thereof.The presence of a plurality of injection nozzles between the combustion chamber and the heat-transfer or convection ducts connecting the chamber to one or more exhaust gas collectors has effects which - as will be explained subsequently - make it possible to achieve the above-indicated goals. These nozzles first of all create losses in the head which are capable of reducing pressure waves in the combustion chamber and therefore make it possible to increase the power of the boiler without increasing the size of the combustion chamber.These injection nozzles strongly accelerate the gases introduced into the heat-transfer or convection ducts, producing a substantial contribution of appreciable movement and an intense mixing of the gases in these ducts. It is due to this stirring of the gases that the heat transfer coefficient is increased and that the length of the convection or heat-transfer ducts can be reduced proportionally to this increase.

Description

Claims

1. A fluid fuel boiler comprising, a combustion chamber, a cover on said combustion chamber having an opening for introducing a combustion supporting gaseous fluid through said opening, a burner for introducing a fluid fuel into the chamber mixed with said gaseous fluid for combustion thereof, water-heating means defining a plurality of water flow paths circumferentially and axially of said combustion chamber, means defining a plurality of axial hot gas flow paths from a downstream portion of said combustion chamber, and means defining a plurality of nozzles for diverting some of said hot gas flow along axially spaced paths in a direction circumferentially of said combustion chamber, and said latter paths being immersed in the flow paths of said water thereby to improve heat transfer.

2. A fluid fuel boiler comprising, a combustion chamber having an opening aligned with a longitudinal axis of said combustion chamber, a burner mounted for introducing a fluid fuel through said opening axially into said combustion chamber, water-heating means defining a plurality of water flow paths circumferentially and axially of said combustion chamber, means for connecting said heating means to a source of cold water, collector means connected to said heating means for collecting hot water flowing through said water flow paths, means defining a plurality of circumferentially spaced axial hot gas flow ducts from a downstream portion of said combustion chamber to an upstream portion of said combustion chamber, means for defining hot gas flow paths comprising convolutions disposed circumferentially of said combustion chamber axially spaced intermediate said water flow paths and next adjacent thereto for heating the water in said water flow paths, means defining a plurality of nozzles for introducing hot gases from said ducts into corresponding hot gas convolutions, and gas collecting means for collecting the hot gases from said hot gas flow paths for exhausting said hot gases after transfer of their heat to water in said water flow paths.

3. A fluid fuel boiler according to claim 2, in which said combustion chamber comprises three substantially circular modules disposed next adjacent each other, said modules comprising said means defining said ducts.

4. A fluid fuel boiler according to claim 2, in which said means defining said hot gas flow paths comprises means defining said convolutions separately, and in which said gas collector means comprises separate gas collectors for collecting gas from said gas flow paths separately.

5. A fluid fuel boiler comprising, a combustion chamber, a cover on said combustion chamber having an opening for introducing a combustion supporting gaseous fluid through said opening, a burner for introducing a fluid fuel into the chamber mixed with said gaseous fluid for combustion thereof, water-heating means defining at least one water flow path circumferentially and axially of said combustion chamber, means defining at least one hot gas flow path from a downstream portion of said combustion chamber circumferentially of said combustion chamber, and means defining nozzles for diverting some of said hot gas flow into said hot gas flow path in a direction circumferentially of said combustion chamber into said hot gas flow path, and said latter path being immersed in the flow path of said water thereby to improve heat transfer.

6. A fluid fuel boiler comprising, a combustion chamber, a through opening on an end of said chamber to receive a burner for introducing into the chamber a mixture of a fluid-fuel and a gaseous combustion supporting agent, means defining at least one water circulation channel connected in operation to a source of cold water, means defining at least one combustion gas circulation channel disposed circumferentially of said combustion chamber and closed at one of its ends while the other end is connectable in operation to an evacuation conduit, means defining a plurality of nozzles whose respective inlet openings communicate with said combustion chamber and having outlet openings discharging into said combustion gas circulation channel, said nozzles being distributed over a portion of the length of said channel extending from its closed end, at least a part of the means defining said water circulation channel and said means defining said gas circulation channel comprising a wall common thereto to obtain an exchange of heat between the gases and the water.

7. A fluid-fuel boiler according to claim 6, in which said combustion chamber is of substantially tubular shape, said opening thereof being disposed concentric to the longitudinal axis of said chamber, a burner to impart to said mixture an intense swirl movement, and means defining several combustion gas circulation channels extending circumferentially around said chamber along planes transverse to the longitudinal axis of said chamber and equidistant from each other.

8. A fluid-fuel boiler according to claim 6, in which said combustion chamber is of substantially tubular shape, said opening being disposed concentric with the longitudinal axis of said chamber, a burner to impart an intense swirl movement to said mixture, said plurality of nozzles being distributed in transverse planes equidistant to each other, the nozzles distributed in a same plane being located at angular distances apart equal to each other.

9. A fluid-fuel boiler according to claim 6, in which at least one cross section of said combustion chamber is a section of revolution, means defining several combustion gas circulation channels extending circumferentially around said section of revolution along planes transverse to the axis of revolution of said chamber, said channels having substantially rectangular cross sections, and said nozzles being disposed to discharge into a middle axial section of the corresponding circulation channels.