US3531229A - Burner - Google Patents

Description

United States Patent 15cc 3,531,229 BURNER Lars Goran Gobriel Berglund, Enkoping, Sweden, as-

signor to Aktiebolaget Bahco, Stockholm, Sweden, a joint-stock company of Sweden Filed Apr. 17, 1969, SenNo. 817,021 Claims priority, application Sweden, Apr. 18, 1968,

,203/ 68 Int. Cl. F23q 7/08 US. Cl. 431-262 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a burner having a combustion chamber, a fuel atomizing or vapourizing body arranged in said chamber and consisting of a heat-resistant, porous material, means for supplying liquid fuel to the combustion chamber and an electric igniting means adapted to heat, vapourize and ignite the fuel, to initiate the combustion sequence.

There exists in known constructions of carburation burners of the type specified, particularly heaters fired o with petrol or diesel oil for instance and installed in motor vehicles or water going vessels, a problem which has not been satisfactorily solved; this problem being one of positive functioning in heating, vapourizing and igniting the incoming fuel when starting the heater, and of maintaining the extent of vapourization during operation in a manner which ensures uniform combustion. A stable flame is to be desired, especially in the case of car heaters, partly from the aspect of noise and partly in view of the fact that a complete combustion must be obtained in all situations, so that the heater can be accepted for maintaining the temperature of or heating the vehicle within confined spaces, such as a garage, in which the exhaust gases are discharged direct to the ambient air. The burner must be capable of starting and working under widely varying conditions, which is particularly true when used in a vehicle heater. Hard winds and slip stream change the pressure conditions and thus the flow of air and fuel for combustion through the heater; shaking of the vehicle whilst in motion and different attitudes of inclination when stationary varies the fuel supply conditions, while the condition of the electrical system can affect the ignition sequence. Furthermore, the sudden supply of very cold air of combustion to the combustion chamber immediately after starting can cause local drops in temperature, which jeopardizes an effective atomization of the fuel and delays the transition to a continuous, stable combustion sequence.

The object of the invention is to provide a combustion chamber unit which is adapted to cooperate with the electric ignition means and to afford the advantages whereby fuel is absorbed and stored therein, thereby to equalize fluctuations in the supply of fuel; whereby the fuel is distributed over a wide area to facilitate vapourization; whereby a large quantity of heat is stored through a relatively large mass, thereby obtaining a stabilizing heat inertia; whereby local heating is provided for initiating vapourization and combustion of the fuel; whereby good 3,531,229 Patented Sept. 29, 1970 heat conductivity is obtained, to provide the vapourization and combustion zones with an opportunity of increasing possibility during the starting sequence immediately after ignition; and whereby a good flame maintaining function is afforded. All these properties, which facilitate ignition, stabilize combustion and render the burner less sensitive to variations in external conditions, are obtained by means of a burner constructed in accordance with the present invention, which is mainly characterized in that the fuel vapourizing body is made of sintered, corrosion resistant steel or other sintered material having a corresponding degree or higher degree of heat conductivity; is adapted as the sole fuel accumulating and fuel distributing means present in the combustion chamber; has the fuel supply means connected direct to the material thereof, to absorb the fuel in the pores thereof; is adapted together with an auxiliary chamber and a main chamber, to maintain a stable flame, said auxiliary chamber and main chamber communicating through a constricted connection and form together therewith a through-flow passage passing through the fuel vapourizing body and opening out at one end into the combustion chamber; and wherein the fuel vapourizing body is so arranged in the combustion chamber that the air for combustion can be supplied through the through-flow passage and at the combustion chamber in such a way that it contacts the tubular outersurface of the fuel vapourization body encircling the through-flow passage, and that the igniter means is arranged in connection with the auxiliary chamber.

The invention will now be described with reference to an embodiment thereof illustrated in the accompanying drawing, FIG. 1 of which shows in longitudinal section a burner fired by means of a spark plug, and FIG. 2 is a section taken along line 2--2 of FIG. 1.

In FIG. 1 there is shown a combustion chamber 2 arranged within a casing 1, which also partly constitutes a wall portion of a heat-exchange arrangement situated between the gases of combustion and a flow of air or water. The combustion chamber 2 comprises a substantially cylindrical, sheet-metal jacket 3, which may comprise one or more parts and which for heat insulation purposes is situated remote from the wall surfaces of the casing 1. One end of the combustion chamber projects out from the interior of the casing 1 towards an end wall of said casing in which a spark plug 5 is arranged, while its other end opens out inwardly towards the casing, to furnish an outlet for the gases of combustion via said end and an exhaust pipe (not shown). The requisite air for combustion is supplied through an opening 6 leading to the interior of the casing within a section which is shielded against the portion through passed by the gases of combustion by a wall 7. Primary air is passed to the burner through openings 8 disposed in the wall of a tubular end portion of the combustion chamber jacket 3 located nearest the end wall and embracing the spark plug 5, while secondary air is supplied through openings 9 in the form of gills disposed in a wall situated in a radial plane, said wall connecting the main portion of the jacket 3 with said narrower end portion. The secondary air openings are adapted so as to impart a rotary movement to the air. The embodiment heretofor described coincides essentially with a conventional, e.g. gasoline, carburation burner.

In accordance with the invention, however, the combustion chamber 2 is provided adjacent the spark plug 5 with a fuel vaporizing body 10 made of sintered, heat resistant material of high thermal conductivity, preferably sintered corrosion resistant steel. The fuel vaporizing body comprises an essentially cylindrical body which is arranged coaxial with the combustion chamber jacket 3 and which presents at its end facing the spark plug 5 an auxiliary chamber 14, while at its other end it presents a main chamber 15 open towards the combustion chamber 2. The

3 auxiliary and main chamber are separated by a partition 16, which is provided with one or more openings 17 (see FIG. 2) disposed asymmetrically relative to the vapourization space, to impart a swirling motion to the flow of air and gas for combustion. The spark plug has only one electrode, and this projects into the auxiliary chamber 14, to leave an appropriate sparking gap between that and the partition 16, which comprises the other pole of the ignition means. Fuel is supplied via a fuel supply line 18 connected to the fuel vapourizing body and opening out into a cavity or recess 19 in the material thereof, to distribute the fuel through the channels of the porous sintered material.

When starting the burner, pulses of high-voltage current are applied thereto, to form sparks between the two poles, which comprise the electrode of plug 5 and the partition 16, simultaneously as fuel is passed to the recess 19. The high temperature of the spark causes a very local vapourization and ignition of the fuel, and thereby initiates a combustion process, the heat of which is used to increase progressively the combustion zone until the entire free surface of the fuel vapourizing body 10 is utilized for vapourizing the fuel and to provide a stable flame.

The main chamber primarily serves during operation to mix preatomized fuel and air, and to maintain and partially from the flame, although the annular space, through which the secondary air is passed, between the outside of the vapourizing body and the wall of the combustion chamber 3 also cooperates in this respect, at least with respect to mixing the fuel and air, as does also the auxiliary chamber 14. It is also possible within the purview of the invention, to construct the burner in a way so as to present a number of main chambers arranged in parallel with regard to flow, whereby the relationship between free vapourization surface and through flow cross-section can be increased.

It is not necessary that ignition is caused by means of a sparking plug in order to practice the invention. For instance, a glow member arranged to project into the auxiliary chamber can be used instead. Furthermore, the material of the fuel vapourization body 10 can be heated to a temperature sufiicient to vapourize and ignite the fuel resistively or inductively, by incorporating a resistance material in the material of the body, by using the material of the body itself as a resistance, or by arranging induction coils in or outside the body 10.

Irrespective of the type of ignition used, the fuel vapour izing body serves to facilitate ignition and during continuous operation assures a stable combustion sequence in the manner specified in defining the object of the (2), a fuel vapourizing body (10) arranged therein and made of porous, heat-resistant material, means (18) for Supplying liquid fuel to the combustion chamber, and an electric igniting means (5) adapted to heat, vapourize and ignite the fuel, to initiate the combustion sequence, characterized in that the fuel vapourizing body (10) is made of sintered material having a corresponding degree or higher degree of heat conductivity; is adapted as the sole fuel accumulating and fuel distributing means present in the combustion chamber; has the fuel supply means (18) connected direct to the material thereof, to absorb the fuel in the pores thereof; is adapted together with an auxiliary chamber (14) and a main chamber (15), to maintain a stable flame, said auxiliary chamber and main chamber communicating through a constricted connection (17) and form together therewith a through-flow passage (14, 17, 15) passing through the fuel vapourizing body (10) and opening out at one end into the combustion chamber (2); and wherein the fuel vapourizing body (10) is so arranged in the combustion chamber so that air for combustion is supplied through the through-flow passage (14, 17, 15) and at the combustion chamber in such a way that it contacts the tubular outer-surface of the fuel vapourization body encircling the through-flow passage, and that the igniter means (5) is arranged in connection with the auxiliary chamber (14).

2. The burner of claim 1, characterized in that the igniter means (5) comprises a glow body projecting into the auxiliary chamber 14).

3. The burner of claim 1, characterized in that the igniter means (5) comprises a sparking plug cooperating with the material of the fuel vapourization body (10) and arranged in or in the 'vicinity of the auxiliary chamber (14), said plug preferably being so arranged that the material of the fuel vapourizing body constitutes one spark pole.

4. The burner of claim 1, characterized in that the igniting means (5) comprises means for resistively or inductively heating a portion of the fuel vapourization body (10), at least adjacent the auxiliary chamber (14).

5. The burner of claim 1, characterized in that the connection (17) between the auxiliary chamber (14) and the main chamber (15) is comprised of a symmetrically arranged openings in a wall (16) separating the chambers.

References Cited UNITED STATES PATENTS 2,229,717 2/1970 Brace et al. 43l262 CARROLL B. DORITY, JR., Primary Examiner US. Cl. X.R.

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