US 3825404 A
The burner is supplied from at least one injector in which to ensure the correct air/gas mixture for the various flow-rates of gas, the injector delivering into at least two successive chambers. One chamber receives the gas at the outlet from the injector and is relatively small so that even at very small flow-rates the proportionality of the air/gas mixture is substantially maintained. This one chamber delivers into the following chamber, which is provided with narrow longitudinal slots for introducing additional air suitable for the largest flow-rates.
Description (OCR text may contain errors)
United States Patent [19 De Gouville I GAS BURNERS, ESPECIALLY FOR DOMESTIC APPLIANCES Inventor: Jean Bernard De Gouville, Veigne Pres Montbazon, France Establissments Sourdillon, Matricage et Robinetberie de Precision, Veigne pres Montbazon, France Filed: Apr. 14, 1972 Appl. No.: 244,042
US. Cl 431/354, 48/180 C, 137/604 Int. Cl. F2311 13/40 Field of Search 431/354, 355; 137/604;
48/180 R, 180 A, 180 C References Cited UNITED STATES PATENTS 11/1891 Boyce 431/355 3/1919 Hansen 431/355 8/1919 Hunten. 431/355 [451 Jul 23, 1974 2,117,270 5/1938 Bloom 431/354 2,450,790 10/1948 Greaves 431/355 FOREIGN PATENTS OR APPLICATIONS 304,938 1/1929 Great Britain 431/355 Primary Examiner-Carroll 'B. Dority, Jr. Attorney, Agent, or Firm-Eric H. Waters  ABSTRACT The burner is supplied from at least one injector in which to ensure the correct air/gas mixture for the various flow-rates of gas, the injector delivering into at least two successive chambers. One chamber receives the gas at the outlet from the injector and is relatively small so that even at very small flow-rates the proportionality of the air/gas mixture is substantially maintained. This one chamber delivers into the following chamber, which is provided with narrow longitudinal slots for introducing additional air suitable for the largest flow-rates.
12 Claims, 7 Drawing Figures PATfNTEuJuLzswn 3,825,404
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GAS BURNERS, ESPECIALLY FOR DOMESTIC APPLIANCES The invention relates to gas burners, especially for domestic equipment (cookers, ovens, washing ma-' chines, etc.), which application will be considered more particularly below.
It is a particular object of the invention to construct these burners such that they enable a greater range of variation in flow-rate, without risk, without back-firing to the injector at very low flow-rates,nor blowing out of the flame at high flow-rates.
It will be recalled firstly, on this subject, that gas burners of known type, that is to say with a calibrated injector and a venturi, are characterized by the induction, of a portion of the air necessary for the combustion, by the effect of a jet of gas emerging from the injector and directed across the opening of the venturi, the latter then leading the air-gas mixture thus obtained, towards the outlet to sections of the burner proper, for example of a crown burner, to which sections the flames attach themselves.
The proper operation of such a burner is conditioned, on one hand, by the quality of the combustion (which must be complete without leaving a deposit) and, on the other hand, by the equilibrium of the flames at the outlet of the burner orifices.
- The equilibrium results from the respective values of two speeds, namely the outlet speed V, of .the air-gas mixture, and the propagation speed of the flames V,
(see FIG. 1 of the accompanying drawings). If V, is too great with respect to V,, the flame is blown out, which can be the case for high flow-rates with a poorly designed burner. If V, is too small with respect to V, (case of slow speed), there is back-firing to the injector.
Now, the values of these two speeds are essentially a function of the values of the air-gas ratio.
In fact, regarding V,, its value is conditioned by the flow-rate of the air-gas mixture admitted to the outlet orifices of the burner, which flow-rate is itself a function of the ratio R air/ gas. On the other hand, regarding V its value is brought to vary with R, and this has been shown in practice. Lastly, theratioR varies itself or with the nature of the gas selected, so that, in the case of all gas burners, which is now the most general case, a just compromise must be selected.
As regards the air-gas mixture, known types of gas burners, with an injector and venturi, show a very distinct tendency for the ratio R air/gas, to be modified with the flow-rate of gas, while on the contrary it is desirable that this ratio remain constant and close to stoichiometric conditions.
Thus, in burners of known type, with an injector and a venturi, if the tap of the burner is manipulated sufficiently rapidly to bring it from the full gas position to the slow speed position, the air/gas ratio is considerably reduced, as is seen in FlG. 5, where the time is plotted on the abscissa and the respective volumes Q, and Q, of air and of gas on the ordinate. The manipulation of the tap is shown by the descending curves Q, and 0,; it is seen that one rapidly arrives at a minimum m for which the ratio R of the volumes of air and of gas is relatively reduced.
On the other hand, as regards theis point m which corresponds to a ratio R sufficiently different from the ratio S of stoichiometry, the speedof propogation of the flame V, tends to increase a corresponding maximum M. This is what happens particularly in the case of town gas that is to say at high-speed V,. The curve C of FIG. 7 shows the variations in the case of town gas, of the speed V, as a function of. the ratio R. For this type of gas, the conditions of stoichiometry (corresponding to the normal flow-rate of gas from-the tap) are shown as the ordinate S, which occur facing the descending portion of the curve C. If, therefore, the ratio R diminishes, it is moved towards zone Z which corresponds to back-firing to the injector. The maximum M of FIG. 5 also expressesthis.
By resaon of this sudden reduction in the ratio R at slow speed, existing burners therefore have the risk of back-firing to the injector and do not permit correct ment does not enable, at slow-speed operation, dropping of the flow-rates of gas to below 1/5 or 1/7 the normal value. This is even more evident in all gas burners for which one must in addition, take into account'differences in the composition of the various gases concerned. I
It is an object of the invention to provide, in burners of the type concerned, such a suction of the air through the flow-rate of gas, that, even at sbw speed, the ratio R tends to remain constant, as illustrated for example in FIG. 6. In this Figure it is seen that the abovementioned special points M and m are avoided and that ratio R remains substantially the same, whence there also results the maintenance of V, at a substantially constant value.
To realize these conditions, or in any case, to approach them as closely as possible, the inventionprovides, in order to ensure correct air-gas mixture at different flow-rates of gas, a succession of at least two chambers, namely, on the one hand, a first chamber into which the injector delivers, this chamber beingsufficiently reduced so that the gas, even at very small flow-rates, ensures the suitable arrival of mixing vair through appropriate orifices, and at the desired ratio R, and on the other hand, a second chamber following the first and adapted to ensure the introduction of additional air for the highest flow-rate. V
This second chamber can, for example,- be arranged in the form of a diffusing cone into which the mixture emerging from the first chamber penetrates, this cone being provided with lateral slots for the introduction of air. These slots create a pressure loss such that, for small flow-rates, the energy brought into play by the jet of gas emerging from the first chamber is not sufficient to overcome the said pressure losses, the first chamber coming practically alone into play, for these rates.
The invention comprises, apart from these features, certain other features which are preferably used at the same time and which will be more explicitly considered below.
It relates more particularly to certain types of uses (especially that in which it is applied to burners of the type concerned for domestic equipment), as well as to certain embodiments of said features; and it relates, more particularly again and this by way of new industrial products, to burners of the type concerned including the application of these same features, as well as to 3 equipment, especially domestic, comprising such burners.
The invention will in any case, be well understood with the aid of the additional description which follows, as well as of the accompanying drawings, which description and drawings are of course given purely by way of illustrative but non-limiting example.
In the drawings:
FIG. 1 shows in vertical section one embodiment of a burner constructed according to the invention;
FIGS. 2 to 4 show separately, respectively in axial section along the line 11-11, FIG. 3, in elevation and in plan, an injection device of the type suitable for inclusion in the embodimentof FIG. 1, this device being constructed according to the invention; and
FIGS. 5 to 7 are graphs intended to assist in the understanding of the invention.
According to the invention and more especially according to that of its types .of application, as well as according to those embodiments of its various parts, to which it would appear that preference should be given, in order for exampleto construct a burner which will be supposed, purely to establish ideas, to be a burner of the ring type procedure is as follows or in analogous manner.
As regards firstly the burner as a whole, to the exclusion of the lower portion'intended to ensure the operation of injecting gas and the introduction of combustion or primary air, that may be arranged in any suitable manner, of course therein calculating the inner volume and the cross-sections so that, taking into account the flow-rate of the air-gas mixture intended to be directed to it from the injector, there is obtained, at the outlet of the burner orifices, a suitable speed V ensuring the maintenance of equilibrium between V and V,.
It is assumed in FIG. 1, that the burner comprises a central body 1, intended to bring. the air-gas mixture, through a passage 2 flaring outwardly, into the distributing chambers 3, extending between a burner head 4 and a cover 5, the air-gas mixture escaping through the orifices 6 distributed all around the burner.
At the lower portion, this body 1 is advantageously extended by a support '7 intended to receive the metering injection device which is to be discussed, the gas arriving through a passageor nozzle 8.
Now as regards the injector with its auxilliary members, instead of being content, as up to the present, to cause the injector to deliver to the inlet of a venturi device arranged at the base of the body such as 1, recourse is had to an arrangement such that there are provided at least two successive mixing chambers, namely:
ranged inside a sleeve 13 which the air can reach, for example, through a plurality of longitudinal slots 14 of constant or variable'cross-section (for instance variable along the axis), it being understood that the crosssection of these slots could be made adjustable, for example by an external sleeve 13a of adjustable position or by any other suitable means.
The three above-mentioned devices, injector, first and second chambers can, as shown, be machined out of the same block, which can for example be screwed at 15 onto the support 7, or again on the contrary they could be constructed separately and assembled in suitable manner. In the example shown, a shoulder of a hexagonal shape is provided at 16 to facilitate screwing. The sleeve 13 can itself have a hexagonal shape in section.
Once this doser-injector 9, 13 is placed in position, the air-gas mixture which escapes penetrates into the passage 1, as shown, with if necessary a space at 17, which can enable, for large flow-rates, introduction of additional air. I
The assembly thus constructed operates in the following manner. e
If there is first considered what occurs in the first chamber 9, it is noted that, in view of the slenderness of this chamber, the jet of gas-which penetrates therein ensures by suction whatever the rate, the introduction the first chamber 9 into which the injector delivers,
this chamber being relatively small to enable the gas emerging from the injector 10, even at very low flowrates, to ensure the suction of mixing air at a predetermined ratio R, through one or several suitably calibrated orifices 11, and if necessary adjustable by any suitable means 11a,
and a second chamber following the preceding one and adapted to ensure the introduction of additional air for higher flow-rates of gas, this chamber being if necessary constituted by the body 1 forming a venturi, but being preferably arranged in the manner indicated be low.
According to a preferred construction, this second chamber is constituted by a divergent passage 12 arof air through the orifices 11 (which are, for example, six in number, regularly distributed).
In-particular, for low and very low rates, it is ensured that the jet of gas enables the introduction of an amount of air in principle proportional to the amount of gas admitted, so that the ratio R air/ gas desired can be realized, even for these low and very low rates.
If one now considers what occurs in the second chamber, it is firstly noted that, for the lower rates which have just been considered, the action of the slots 14 is practically nil, since the energy brought into play by the jet of gas and the air is not sufficient to overcome the considerable pressure losses to which the said slots give rise. Hence theyhave no disturbing effect on the value of R at low rates.
It is self-evident that to determine the ideal crosssection of these slots 14 to the desired end, suitable experiments could be carried out in a laboratory.
On the other hand, for very high rates, up to nominal rate, the induction of supplementary air is ensured by theabove'said slots, due to the increase in energy of the gas jet emerging from the said chamber 9. Possibly, a re-introduction of additional air could be provided for the highest rates.
Dut to the action of these two successive chambers,
the principal object sought by the invention can be achieved, namely:
to maintain substantially constant the ratio R air/gas, which will be selected in the neighborhood of the stoichiometric conditions,
and, consequently reduction to a great extent of the variation in the outlet speed V at the burner as a function of the flow-rate of gas.
By way of example and while enabling reduction in the flow-rate of the gas at slow-speed operation to values of the order of l/lO to l/l5 of the nominal flowrate, there is a possibility of arranging that the ratio between the out flow speed V, at normal operation and the speed V, at slow speed operation does not exceed 20. Under these conditions, since the speed of flame propagation V, can be kept almost constant (due to the stability of the ratio R) the equilibrium of the speeds V, and V, at the outlet of the burner can thus be maintained, thus avoiding both the blowing out at high delivery rates and back-firing at low delivery rates.
It will also be possible to manipulate the tap rapidly from the position of nominal rate to the position of slow-speed operation, without risking the anomalies of the curves of FIG. 5, at M and m.
There is given below, of course by way of nonlimiting example, data relative to specific cases (in mm).
a. Burner of 2,600 kcal/h:
Diameter of injector: 2,30
Total section s of the holes 11 z 19 mm Size of the chamber 9 diameter: 3.5 length: 4
Width L of the cone 12 17 Diameter of this cone at the outlet: 9
Width of the slots 14 0.7
For town gas, the ratio nominal flow rate/slow speed flow rate, has been of the order of- 1/17, with risk neither of blowing out nor of back-firing. The ratio R air/gas is of the order of 4.2, little different from the stoichiomatic ratio.
For natural gas, the conditions are as follows:
R air/gas is of the order of 9.7, little different from the stoichiometric ratio.
b. Another example for a burner of different power.
Burner of 1,500 kcal/h:
Diameter of injector: 1.70
Total cross section s of the holes 11 11 mm Dimensions of the chamber 9 diameter: 2.55 length Length L of the cone l2 17 Diameter D of the cone at the outlet: 9
Width of the slots 14 0.7
Ratios nominal flow rate/slow speed flow rate, and R air/gas: are identical with those of the burner of power 2,600 kcal/h.
As a result of which, whatever the embodiment adopted, there can be constructed burners whose operation becomes clear from the foregoing for it to be unnecessary to dwell further on the subject and which have, with respect to previously existing burners of the type concerned, numerous advantages, especially:
The possibility of substantially increasing the range of variations in flow-rate, that is to say of lowering the slow-speed flow-rate,
consequently, in its application to cookers, the possibility of enabling very slow flames(for simmering, etc.),
and the possibility of avoiding back-firing in the case especially where the taps are rapidly manipulated towards their slow-speed position.
As is self-evident and as emerges already from the foregoing, the invention is in no way limited to those of its types of application, nor to those embodiments of its various parts, which have been more especially envisaged; it encompasses, on the contrary, all modifications.
1. A gas burner comprising an injector means for introducing gas under pressure, means having at least two successive chambers into which said injector means delivers the gas under pressure, a first said chamber receiving the gas from the injector means being relatively small and having air orifices to form an air/gas mixture in said first chamber so that for very small flow rates, the composition of the air/gas mixture is maintained substantially constant, a second said chamber being downstream of the first chamber and in communication therewith to receive the air/gas mixture from said first chamber, said second chamber having relatively narrow longitudinal slots extending substantially along the entire length thereof and proportioned for introducing additional air suitable for the largest flow rate in such amount that the air/gas mixture is maintained substantially constant in composition for all flow rates through the burner.
2. Burner according to claim 1, wherein thesecond chamber is in the form of a venturi.
3. Burner according to claim 1, wherein the. second chamber is constituted by a divergent passage following the first chamber.
4. Burner according to claim 1, wherein the second chamber forms a single unit with the injector.
5. Burner according to claim 1, wherein the injector, the first and second chambers are of monobloc construction.
6. Burner according to claim 5, including a support on to which said monobloc is screwed.
7. Burner according to claim 5, comprising a burner assembly and a support for the monobloc construction of the injector and its chambers forming a unit with the burner assembly.
8. Burner according to claim 1, comprising a central body into which said second chamber opens.
9. Burner according to claim 8, wherein said second chamber is a divergent chamber which opens with a gap into the central body of the burner.
10. Burner according to claim 1, wherein orifices of the first chamber extended radially.
ll. Burner according to claim 1, including means for adjusting the orifices for the inlet of air into the first chamber.
l2. Burner according to claim 1, including means for adjusting said slots through which the air enters into the second chamber.