EP0064170B1

EP0064170B1 - Blue flame burner for liquid fuels

Info

Publication number: EP0064170B1
Application number: EP82102973A
Authority: EP
Inventors: Placido Zampieri; Giovanni Martinoni
Original assignee: INNOCENTI NEE MARTINONI MARIA; MARTINONI NEE VALLI FRANCA; Innocenti Nee Martinoni Maria; Martinoni Anna; Martinoni Giuliana; Martinoni Laura; Martinoni Martino; Martinoni Nee Valli Franca; CEM SpA Trezzano Sul Naviglio
Current assignee: BERTOLI NEE MARTINONI, LUCIANA; INNOCENTI NEE MARTINONI MARIA; Martinoni Anna; Martinoni Giuliana; Martinoni Laura; Martinoni Martino; MARTINONI NEE VALLI FRANCA; CEM SpA Trezzano Sul Naviglio
Priority date: 1981-04-17
Filing date: 1982-04-07
Publication date: 1985-10-09
Also published as: EP0064170A1; IT8184929A0; ZA822613B; ES511471A0; BR8202213A; ES8302886A1; DE3266760D1; IT1147440B; JPS57182005A; ATE16042T1; AR227236A1; AU8267282A

Description

This invention relates to a blue flame burner for liquid fuels as set out in the pre-characterising part of claim 1, and as disclosed in EP-A2-0023001.
Known from this prior art are blue flame burners for liquid fuels which, while being much more efficient than traditional white flame burners, require the provision of two discrete combustion air feed paths to the burner combustion cnamber. The two paths are conventionally designated primary air path and secondary air path, respectively. The provision of such dual paths involves, in addition to designing and construction problems, also the solution of complex problems connected with the volume and velocity metering of the air flow therethrough, as well as of mutual correlation and interdependence.
Thus the task of this invention is to provide a blue flame burner for liquid fuels which, additionally to substantially removing the cited problems and shortcomings affecting prior burners, can afford a definitely superior performance level.
With this task it is an object of the invention to provide a burner as indicated, which affords, to all practical effects, a complete combustion, leaving no unburned portions of the fuel, by ensuring that the combustion can take place in a stoichiometric ratio of fuel to combustion air, or a ratio very close to the theoretical stoichiometric values. This means that the excess air flowing through the burner is nil or close to zero, for a higher thermal efficiency of the burner.
A further object of this invention is to provide a burner as indicated above, which has a very simple construction, comprises a minimum of components, can be readily and conveniently assembled and disassembled, and can be manufactured at a highly competitive cost.
The present invention solves the above task by providing a burner as indicated above with all the features of the characterising part of claim 1.
Further aspects and advantages will become apparent after considering the following detailed description of a preferred embodiment of this invention, given herein by way of example and not of limitation, in conjunction with the accompanying illustrative drawings, where:

Figure 1 is a schematic view, in elevation and longitudinal section, of a burner according to the invention;
Figure 2 is a schematic elevation view of the burner of Figure 1, as placed at the inlet end of a refractory material lined chamber; and
Figure 3 is a C0₂ vs. O2 percent graph.

With reference to Figures 1 and 2, where similar parts have been designated with the same reference numerals, this burner 1 has an elongate hollow body 2, a calibrated nosepiece 3 removably attached to one end of the hollow body 2, and an end cap 4, removably attached to the other end of the hollow body. The latter is formed, at an intermediate region thereof, with an annular increased-thickness portion, whereat a restriction or neck 5 is defined internally. The annular thickened portion in the hollow body 2 acts as a partition member separating two internal cavities in the body 2, namely a front cavity 6 and rear cavity 7. The front cavity 6 is, thus, delimited on the front by the nosepiece 3 and constitutes the burner combustion chamber, which is cooled externally by a fluid circulated at 6a, while the rear cavity 7 is closed by the end cap 4 and constitutes a combustion air pre-heating chamber, as will be explained hereinafter. The chambers 6 and 7, and the neck 5, are all aligned together along the longitudinal axis x-x.
At the neck 5, there is arranged, in a removable manner, a bushing 8, which abuts externally and peripherally against the inner wall of the neck 5, and has an inner bore 9 convergent toward its calibrated end 10 facing the chamber 6.
The end cap 4, and accordingly the chamber 7, is communicated, through a hole 11 formed through a lug 12 whereto is secured one end of a preferably flexible hose line 13, to the delivery end of a blower or compressor 15 of the two-stage type which is arranged to deliver pressurized air into the chamber 7. Through the end cap 4, a hole 16 is also formed which extends coaxial with the axis x-x, and is connected to a pressurized liquid fuel (e.g. Diesel oil) supply conduit 17. More specifically, the hole 16 is formed through an inside lug 18 which, from the rear wall of the end cap 4, extends in cantilever relationship along the axis x-x over the entire length of the end cap. At the free end of the lug 18, there is secured one end of a conduit or line 19, which enters the bushing 8 cantilever-fashion. The free end of the conduit 19 accommodates, mounted therein, an atomizing injector device 20, which barely clears with its spray nozzle 21 the calibrated end 10 of the bushing 8.
On that section of the line 19 which extends outside of the bushing 8, there is slidably mounted, and adjustably fastened, a disk or diaphragm 22 which functions as a restrictor element for the air coming from the passage 11 and directed to the combustion chamber.
Laterally to the restriction 5, at the thickened region of the hollow body 2, there are formed holes intended to accommodate flame ignition and control metal electrodes 24, which protrude into the combustion chamber 6.
The pressurized fuel supply line 17 is in turn connected, with the interposition of a control solenoid valve 25, to a suitable fuel pump 26.
At the intake mouth of the blower 15, a conduit 28 is provided which can be shut off by means of a movable shutter 29 driven by a solenoid valve 30. Upstream of the shutter 29 is located a metering device 31 arranged to control the flow rate of the combustion air directed to the burner.
Preferably, the metering device 31 can be adjusted by means of a micrometric adjustment pin screw.
The burner described hereinabove operates in a very simple manner. After starting the blower 15 and actuating the pump 26, the shutter 29 will be in its air shut-off position; however, thanks to a central hole 32 provided therein, a sufficient amount of air can still be admitted to the combustion chamber 6 to cause ignition. Once the fuel has been so ignited, the solenoid valve 30 will be controlled, by an electronic control unit not shown in the drawings, to open, so that pressurized combustion air can be delivered into the chamber 7 at a pressure and volume consistent with the amount of fuel issuing from the atomizing injector 20, and in all cases in stoichiometric proportion for burning the particular fuel being used.
In operation, the hollow body 2 will be heated at the combustion chamber 6, and transfer part of its heat by conduction to both the air within the chamber 7 and fuel flowing through the lug 18. By convection, the air contained in the chamber 7 will in turn assist in the transfer of heat from the inner walls of the chamber 7 to the conduit 19, thereby the oncoming fuel to the atomizing injector device 20 is adequately pre-heated.
The air contained in the chamber 7 initially undergoes expansion in flowing from the hole 11 to that portion of the chamber 7 which is located upstream of the diaphragm 22. The diaphragm 22 will instead force the air to flow peripherally past it and then sweep the inner wall of the tubular body 2, thereby its velocity is increased. Between the diaphragm 22 and bushing 8, the air is subjected to further expansion, and by virtue of the bushing 8 being configured to protrude in part, cantilever-fashion, toward the interior of the chamber 7 from the restriction or neck 5, it undergoes a mixing and thermal stabilization process prior to flowing through the bore 9 in the bushing 8. Through the bore 9, the air is uniformly distributed along and around the atomizing injector device 20, and upon reaching the calibrated end 10 of the bushing 8, it is directed concentrically toward the interior of the chamber 9, to encircle the jet(s) of atomized fuel issuing from the nozzle 21. It is important that the atomized fuel spray be focussed on the area of highest turbulence of the combustion air being fed into the combustion chamber.
With burners constructed as described hereinabove and operating as herein detailed, efficiency rates have been achieved on a regular basis which equal or exceed 99 percent, as against maximum rated efficiencies of 82-85 percent or comparable white flame burners of conventional design and construction.
Moreover, besides the very high thermal efficiency afforded by a burner according to this invention, several other advantages can be secured, among which:

- complete combustion of the fuel with total absence of unburned residue;
- high temperature of the resulting flame emerging from the combustion chamber 6;
- issue of polluting gases in negligible amounts; and
- very low maintenance costs, largely on account of the absence of unburned products.

Tests have been carried out on a burner as described above, having its nosepiece 3 located at the inlet end of a chamber 33 lined with tiles 34 of a refractory material, as shown in Figure 2. The refractory material lining, upon becoming red-hot, will issue light in the white-red bands with a high emissivity. Thus, inside the chamber 33 temperatures in excess of 1,500°C are to be achieved within few minutes (3 to 5 minutes) from burner ignition.
With a burner 1 and chamber 33 as shown in Figure 2, but associated with a small-size boiler (having outside dimensions of 45 x 88 x 58 cm) surrounded by a water jacket, actual tests have provided the following values:
As may be appreciated from the graph of Figure 3 (Ostwald triangle), for a content of carbon dioxide of 14.5 percent, there only occurs a both theoretical and practical excess of air of 1.3. Moreover, the virtual absence of carbon monoxide from the combustion products along with the high percentage of carbon dioxide is a sure indication, to all practical effects, of all the fuel being burned completely.
Actual tests have also shown that the sizing of this burner to meet varying power requirements in different applications will depend on the varying and mutual correlation of but a few structural elements. These are the inlet port size of the metering device 31 (T), the port size (U) of the calibrated end 10 of the nozzle 8, the maximum inside diameter (C) of the combustion chamber, the length (L) of the combustion chamber, and the diameter (B) of the. nosepiece 3.
The following exemplary correlations of the above-specified values T,U,C,L and B have shown to be advantageous in practicing the invention:
The above-tabulated results relate to a fuel delivery pressure of 18 kg/cr₇i. ^-

Claims

1. A blue flame burner for liquid fuels including an externally cooled combustion chamber (6), an atomizing injector (20) adapted to scatter atomized fuel toward said combustion chamber (6), a pre-heating chamber (7) arranged to receive air from a source of pressurized air, and a pressurized fuel intake conduit (19) which is arranged to feed the atomizing injector (20), is disposed within said pre-heating chamber (7) and is connected to a source of pressurized fuel, characterized in that it comprises a calibrated neck (5) arranged to receive the free end of the atomizing injector (20) cantilever mounted in the pre-heating chamber (7) and to allow communication between the pre-heating chamber (7) and the combustion chamber (6), and in that the said pressurized fuel intake conduit (19) is in heat exchange relationship with the pre-heating chamber (7) to pre-heatthe fuel from the pressurized fuel source, whereby, in use, all combustion or other air from the pressurized air source flows through, and is pre-heated by, said pre-heating chamber (7), passes through the calibrated neck (5) and is mixed, while entering the combustion chamber (6) with the pre-heated atomized fuel scattered by the atomizing injector (20).

2. A burner according to Claim 1, characterized in that said neck (5) accommodates a calibrated passage bushing (8) adjacent said combustion chamber (6).

3. A burner according to either Claim 1 or 2, characterized in that said combustion and pre-heating chambers (6, 7) are formed within an internally restricted hollow body (2) bearing at one end a calibrated nosepiece (3) adapted to confine said combustion chamber (6), and closed at the other end by an end cap (4) adapted to confine said pre-heating chamber (7).

4. A burner according to Claim 3, characterized in that said end cap (4) has a bored lug (18) connected to said pressurized fuel supply source and adapted to feed and cantilever carry said atomizing injector (20).

5. A burner according to Claim 4, characterized in that said combustion chamber (6), calibrated restriction or neck (5), pre-heating chamber (7), and end cap bored lug (18) are all aligned together along a common axis.

6. A burner according to any one of the preceding claims, characterized in that it further comprises a velocity regulator for the airflow entering said pre-heating chamber (7).

7. A burner according to Claim 6, characterized in that said regulator comprises a disk-like diaphragm (22) the position whereof is adjustable.

8. A burner according to any one of the preceding claims, characterized in that said pressurized air source includes a two-stage blower (15) comprising a metering-shutter device (29, 31) located at the intake end thereof (27).

9. A burner according to Claim 8, characterized in that said shutter device (29) is controlled by means of a solenoid valve (30), while said metering device (31) includes a micrometric adjustment pin screw.