COMBUSTION CHAMBER FOR PULSATING COMBUSTION

Abstract: A combustion chamber for pulsating combustion is separated by a partition wall (12) into a first chamber (14) to which there is connected an axial inlet (20) for the fuel stream, and a second chamber (16) for diverting the combustion gases through an outlet (18). The gases depart via side chambers (44) from the first to the second chamber at the edges of the partition wall. A hot body (24) is arranged at a given height above the partition wall in the first chamber, said body being intended for being heated during operation to a temperature which is substantially higher than the carbonization temperature of the fuel and which screens off a central area of the partition wall.

Description: Combustion chamber for pulsating combustion The present invention relates to a combustion chamber of the kind disclosed in the preamble to the following main claim. In pulsating burners of the kind i -question, there is a fuel nozzle at the inlet to direct the stream of fuel axially into the first chamber in a direction towards a central area of the pertinent partition wall in the com¬ bustion chamber. In the case where a liquid fuel such as oil is used, vaporization is already obtained in the inlet, but a portion of the fuel will impinge on the partition wall in the form of vapour or fuel drops. For all conditions some cooling of the partition wall is obtained, and this cooling can be so heavy in some cases that the fuel carbonizes, to be deposited as soot, which results in operational disturbances, especially when starting. The object of the invention is to avoid this problem, and this is achieved in accordance with the invention by an arrangement which has the characterizing features disclosed in the following claims. The hot body in accordance with the invention spreads out the fuel while coming up to a temperature high enough to be substantially above the carbonization temperature of the fuel by a large margin. The desired intense heating of the hot body is done with the aid of the hot gases in the first chamber in the com¬ bustion chamber, and by heat transmission from the partition wall to the hot body via the foot of the latter. The hot body in accordance with the invention spreads the fuel and screens off the central area of the partition wall, which thus cannot be struck by cooling fuel. The hot body simultaneously contributes, as is known in the art, to stabilizing the combustion in the combustion chamber. To further increase heating of the hot body, its foot can to advantage be formed as a pillar extending through an opening in the partition wall to be situated in the hot gases in the outlet. Two suitable embodiments of the invention are shown as examples on the appended drawings. Fig, 1 is a schematic section through a combustion chamber for pulsating combustion, the partition wall in the com¬ bustion chamber supporting a disc-shaped hot body in accordance with the invention, Fig, 2 is a cross section along the line 2-2 in Fig. 1, Fig. 3 is a cross section along the line 3-3 in Fig. 1, Fig. 4 is a side view of the second embodiment, comprising a spherically shaped hot body with a pillar mounted in the opening in the partition wall according to Fig. 1, Fig. 5 is a view seen from below of the hot body in Fig, 4, Fig. 6 is a view from above, Fig. 7 is a section along the line 7-7 in Fig. 4, Fig. 8 is a section along the line 8-8 in Fig. 6 . and Fig. 9 shows the spherical hot body mounted in the combustion chamber. The combustion chamber 10 in Fig. 1 is of known form and is divided by a partition wall 12 into a first chamber 14 and a second chamber 16, the latter merging into an outlet 18. Combustion air is inducted via an inlet 20, in which a nozzle 22 is arranged for spraying in fuel such as oil for admixture with, the combustion air. It will be seen from Fig. 1 that the spread angle of the nozzle is comparatively small, resulting in that the fuel is directed in a relative- ly concentrated jet into the first chamber 14. To avoid fuel particles impinging on the partition wall 12 in its central area, and thereby cooling this area to an undesirably low temperature which can cause the formation of soot, a flat-shaped hot body 24 is arranged at a pre¬ determined height above the partition wall. In the example shown, the hot body 24 is substantially circular, to give a uniform spread to the fuel irrespective of the width of the fuel jet. The body 24 is carried by a foot or a support 26 in the form of four radial flanges 25,28,30,32 arranged in a cross. The foot 26 has an upper part situated above the wall 12, and an extension portion 34 extending through a central hole 36 in the wall 12, down into the second chamber 16 and further down into the outlet 18. Each flange has a shoulder 38 resting on the wall 12. After this shoulder, the width of the flanges is constant along a portion 40 for location in the hole 36 of the wall 12. Below the partition wall 12, the flanges taper off in a direction towards an end portion 42. The fuel-air mixture and hot gases stream out conventionally from the central portion of the first chamber into a number of side chambers 44, over the edges of the partition wall 12 into its side chambers, down into the second chamber 16 and out through the outlet 18. During operation, the hot body 24 is kept heated to a high temperature which is sufficient for the body 24 always to have a temperature substantially greater than the carboniza¬ tion temperature of the fuel. The central area of the wall 12 will therefore lie in a protected position under the shielding hot body 24, so that the central area of the wall 12 will also retain a temperature which is so high that it is substantially above the carbonization temperature of the fuel. The body 24 is heated by the hot gases in the first chamber. Furthermore, the extended portion 34 of the foot or support 26 will be heated by the hot gases in the second chamber -^UR£ OMPI and in the outlet. The heat spreads upwards in the foot and results in there being supplementary heat to keep the body 24 hot. Heat is- also transmitted, from the wall 12 to the foot 26 and further to the body 24. With its foot 26 the body 24 is loosely inserted in the hope 36 in the wall 12 and therefore it can be easily lifted out and up through the inlet 20 for possible exchange. It is thus extremely easy to fit or remove the body 24. The embodiment according to Figs. 4 to 9, which has been developed further, has a substantially spherical hot body 50 carried by a short neck 51 with a flange 52 having slots 52a, said flange abutting the upper side of the wall 12. Below the flange 52, the neck is extended by a pillar 53 which is located in the hole 36 in the wall 12 in the same way as the portion 34 is located in the hole 36 in Fig. 1. The pillar 53 extends through the second chamber 16 and down into the outlet 18 to be heated by the exhaust gases. The hot body 50 is formed at its upper end with a recess having a diameter of the same order of magnitude as the radius of the body 50. The depth of the recess is approxi- ately the same as its radius. Around its spherical surface, the body 50 has a number of uniformly distributed slits 55,56, the alternate slits 56 being in communication with the bowl-shaped recess 54 via radially transverse grooves 57. For predetermined and comparatively constant operating conditions, the flat-shaped hot body 24 according to Figs. 1 to 3 functions completely satisfactory for providing a reliable start and stable operation, and for avoiding soot formation in the first chamber on the partition wall 12. On the other hand, if the operating conditions vary, inter alia with different types of fuels and varying loads, the spherically shaped hot body 50 in Fig. 4 affords greater flexibility and security.

Claims: CLAIMS 1. A combustion chamber for pulsating combustion of a fuel-air mixture, including inlet and outlet providing substantially axial inflow of the fuel-air mixture to a first chamber and substantially axial outflow from a. second chamber, as well as a partition wall situated substantially in a radial plane and separating the two chambers to guide the stream of gases over the edges of the partition wall from the first chamber via a plurality of side chambers to the second chamber, characterized in that a central area of the upper side of the partition wall (12) in the first chamber (14) is screened off by a hot body (25,50) which is arranged at a predetermined height above the partition wall and serves as a fuel spreader. 2. A combustion chamber as claimed in claim 1, character¬ ized^ in that the hot body has a concave striking surface facing towards the inlet for the fuel drops. 3. A combustion chamber as claimed in claim 1, character¬ ized in that the hot body (50) is substantially spherically shaped. 4. A combustion chamber as claimed in claim 3, character¬ ized in that the upper end of the spherically shaped hot body (50) is provided with at least one recess (54) for the reception of fuel drops. 5. A combustion chamber as claimed in claim 4, character¬ ized in that the diameter of the recess is of the same order of magnitude as the radius of the spherical body, and in that the depth of the recess is approximately equal to its radius. 6. A combustion chamber as claimed in claim 4 or 5, characterized in that a plurality of uniformly distributed, -g3R£Λ axial slits (55,561 are made in the spherical surface of the body. 7. A combustion chamber as claimed in claim 6, characterized in that at least some of the slits communicate with the recess via radial grooves (57) . 8. A combustion chamber as claimed in any one of the preceding claims, characterized in that the hot body is carried by a foot (26,51) which is extended and passes through, an opening (361 in the partition wall and is guided in the latter, and has a portion (34,53) situated below the opening, said portion being situated in the second chamber (16] and in the outlet (18) for being heated by the exhaust gases. - < gτjRE 7 OMPI

Inventors: OLSSON K
Applicants: MARECK BV, OLSSON K
Application year: 1981
Main classification: F23C11
IPC codes: F23C15