Diesel engine with self-engaging combustion chamber

Abstract

Recessed combustion chamber (10) comprising: a profile (13) forming the inlet of the combustion chamber (10), which is a projecting surface formed inwards in the combustion chamber (10), and the underside of the combustion chamber (10), which is a recessed space formed outwards below the inlet in the combustion chamber (10); a cone (17) formed in a truncated cone shape extending from the profile (13) and projecting towards the central space in the combustion chamber (10);and an upper end (11) for enlarging the space of the combustion chamber (10) by enlarging the upper surface of the combustion chamber (10) at the inlet of the combustion chamber (10), wherein the profile (13) is divided into a slope (14), a projection (15) and a trough rim (16), the slope (14) being an inclined surface extending from the upper end to the projecting surface, the projection being the protruding surface connecting the slope (14) and the trough rim (16), thereby forming the inlet of the combustion chamber (10), and the trough rim (16) forming the underside of the combustion chamber (10), which is the recessed space, and wherein the trough rim (16) has a trough curvature formed by the recessed space, and wherein the trough rim curvature is divided into an underside curvature (Rc) extending to the projection and a conical curvature (Rd) is subdivided, which continues to the cone (17).;

Description

CROSS REFERENCE TO RELATED APPLICATIONSThis application claims priority to Korean Patent Application No. 10-2017-0134550, filed on Oct. 17, 2017, which is incorporated herein by reference in its entirety.BACKGROUNDField of InterestThe present disclosure relates to a combustion chamber, and more particularly to a diesel engine having a compression combustion chamber suitable for a super high pressure injection environment.DESCRIPTION OF THE RELATED ARTIn general, a diesel engine injects fuel into compressed air at a high temperature and a high pressure and ignites and burns the mixed gas, an important factor in the combustion being the generation of flows of the intake air and the sprayed fuel and the atomization of the injected fuel.The currents are generated to well mix air and fuel by creating swirls, swirls, or rotating motions (tumbles) in a combustion chamber, and atomization serves to form many small droplets of the injected fuel to promote mixing of the sprayed fuel and air from the atmospheric environment by increasing surface areas.Thus, the combustion chamber of a diesel engine must have a shape (or structure) suitable for generating flows and atomizing fuel. For example, there is a split spray type combustion chamber and a two stage bowl type combustion chamber.The split spray type combustion chamber promotes flow generation and fuel atomization by generating small vortices therein by spraying fuel to the top wall thereof and thus splitting the fuel up and down.The two-stage bowl type combustion chamber has a large space defined by a bottom having no step and an upper wall having a step, and promotes flow generation and fuel atomization by generating larger vortices larger than small vortices therein. For this purpose, DE 10 2009 025 404 A1 already discloses a piston for valve-controlled reciprocating piston diesel engines, which is designed with an annular step which runs out into the piston crown via a slope and is provided so as to surround the edge with a piston depression, which receives a dome having a cut-off crown surface. In DE 103 92 141 B4, a piston for an internal combustion engine is shown, which comprises a combustion bowl with a fuel guiding structure for diverting at least a part of the fuel leaving the combustion bowl. One shape of the piston includes a sharp edge disposed on the outer surface of the piston adjacent the entrance to the combustion bowl and a rounded fuel receiving lip located within the combustion bowl. In addition, DE 102 61 333 A1 discloses a piston for an air-compressing internal combustion engine with direct injection, having a combustion chamber depression arranged in the piston, which preferably has a toroidal section and proposes, in order to reduce the combustion residues introduced into the engine oil, that a circumferential indentation facing away from the piston edge is arranged on the top side of the piston between the piston edge and the edge of the combustion chamber depression, wherein the indentation directly adjoins the edge of the combustion chamber depression and runs out into the combustion chamber depression.The disclosure of this section is for providing the background of the invention. The Applicant notes that this section can receive information available prior to this application. However, by providing this portion, the applicant does not eliminate that any information contained in this portion constitutes the prior art.SUMMARYFor smoke reduction, it is desired that the diesel engine has an optimum shape that can generate strong vortices in a combustion chamber and can more effectively use fresh air with the entire air for combustion.Further, when the fuel injection pressure of diesel engines is increased above 2200 bar (220 MPa), it is desired to have a combustion chamber shape suitable for such a super high injection pressure.In consideration of this problem, an aspect of the present invention is to provide a diesel engine having a compression combustion chamber suitable for a super high injection pressure which has not been achieved by the split spray type combustion chamber and the two-stage bowl type combustion chamber by changing the shape of an inlet of a combustion chamber and the shapes of the bottom of the combustion chamber continuing from the inlet and a cone continuing from the bottom of the combustion chamber to the center so as to be suitable for generating large vortices, and more specifically, by bringing the curvature of the bottom, which is strengthened by the compression shape of the inlet of the combustion chamber, into association with the straight shape of the cone.A compression combustion chamber according to an incorporated embodiment of the present invention includes: a profile that forms the inlet of the combustion chamber, which is a protruding surface formed inward in the combustion chamber, and the bottom of the combustion chamber, which is a recessed space recessed downward below the inlet in the combustion chamber; a cone that is formed into a truncated cone shape that continues from the profile and protrudes to the central space in the combustion chamber; and an upper end for expanding the space of the combustion chamber by expanding the top of the combustion chamber at the inlet of the combustion chamber, wherein the profile is divided into an inclination, a protrusion and a bowl edge, the inclination is an inclined surface continuing from the upper end to the protruding surface, the protrusion is the protruding surface and connects the inclination and the bowl edge, thereby forming the inlet of the combustion chamber, and the bowl edge forms the bottom of the combustion chamber being the recessed space, and wherein the bowl edge has a bowl curvature formed by the recessed space, and wherein the bowl edge curvature is divided into a bottom curvature continuing to the protrusion and a cone curvature continuing to the cone.The upper end is formed by cutting the top of the profile at a combustion chamber enlarging depth to enlarge the combustion chamber; and the cone is the truncated cone shape having a straight wave.The slope continues to the protrusion by a slope curvature formed by the top end. The protrusion continues to the trough edge by a protrusion curvature formed from the top end. The trough edge curvature is divided into a bottom curvature continuing to the protrusion and a cone curvature continuing to the cone. The truncated cone of the cone forms a straight oblique side.The radius center of the recessed space is set as a combustion chamber reference diameter, and when the combustion chamber reference diameter is 100%, the minimum combustion chamber diameter defined by the protrusion is 120-1335, the maximum combustion chamber diameter defined by the bowl rim is 120-140%, and the tooth diameter is 10-15%.When the height of the combustion chamber from the lower side to the upper side of the combustion chamber is 100%, the combustion chamber enlargement depth is 4-12% and the tooth depth is 25-42%.A diesel engine according to a incorporated embodiment of the present invention includes: a piston having a re-entry combustion chamber defined by: a profile that forms the inlet of the combustion chamber that protrudes inward in the combustion chamber and the bottom of the combustion chamber through a recessed space that is recessed outward in the combustion chamber; a cone that is formed into a truncated cone shape that protrudes with a straight oblique side at the central space in the combustion chamber; and an upper end that increases the space of the combustion chamber and is formed by widening the top of the profile.The penetrating combustor has a left-right symmetrical structure with a peak at the center. The combustion chamber is formed by connecting a slant curvature and a protrusion curvature having different sizes, and the recessed space is formed by a trough curvature, and the trough curvature is formed by connecting a bottom curvature and a cone curvature having different sizes. The cone is a truncated cone and forms a tip in the center of the combustion chamber.According to the combustion chamber of a certain embodiment, a large vortex is generated in the combustion chamber using energy of the sprayed fuel by increasing the radius of the lower surface using a sinking type, and the flow flowing smoothly to the center of the combustion chamber is formed by a flow of the sprayed fuel generated by the straight portion.According to the diesel engine of a certain embodiment, since a large swirl and a flow flowing to the center of the combustion chamber is formed by the injection shape, the injection combustion chamber is further suitable for a super high injection pressure that cannot be obtained by the split spray type combustion chamber and the two-stage trough type combustion chamber. In particular, the combustion chamber is applied to the super high injection pressure of 2200 bar (220 MPa) or more and may therefore meet improved EM and fuel efficiency regulations.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a view showing a diesel engine having a compression combustion chamber on the top of a piston according to embodiments of the present invention. FIG. 2 is a view showing arrangements of portions of the injection combustion chamber according to embodiments of the present invention. FIG. 3 is a view showing a state in which fuel is sprayed into a compression combustion chamber of a diesel engine according to embodiments of the present invention. FIG. 4 is an analysis diagram showing flows moving to the center in the re-entry combustion chamber according to embodiments of the present invention when fuel is sprayed and burned using a 3D velocity field. FIG. 5 is a view showing the state in which a large vortex is generated to reduce smoke in the injection combustion chamber according to embodiments of the present invention. FIG. 6 is a 3D analysis diagram showing a combustion result in the re-entry combustion chamber according to embodiments of the present invention.DETAILED DESCRIPTIONHereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the present invention can be achieved in various ways by those skilled in the art, and therefore the present invention is not limited to the embodiments.Therefore, referring to FIG. 1 showing the TDC (Top Dead Center) of a piston 5 in a diesel engine in which the piston 5 has a compression combustion chamber 10, large vortices for fuel atomization and flows moving to the center in the combustion chamber are uniformly generated by the compression shape.Referring to FIGS. 1 and 2, in a cross section taken along a central axis (0-0 in FIG. 2 ), a piston 5 and a cylinder head 6 are symmetrical about the central axis (axis of piston movement). The piston has a first flat surface 11 (J to K), a second curved surface 14A (K to L), a third curved surface 14B (L to M), a fourth curved surface 16 (M to N), a fifth flat surface 17, and a sixth flat surface 19 connected in series. In the embodiments, the second curved surface 14A, the third curved surface 14B, and the fourth curved surface 16 have different radii of curvature. The points K, L, M are inflection points separating the second curved surface 14A, the third curved surface 14B, and the fourth curved surface 16. In the embodiments, each of the curved surfaces 14A, 14B, 16 has two or more radii of curvature therein.In the embodiments, the radius of curvature Ra at a point of the second curved surface 14A is smaller than the radius of curvature Rb at a point L, the radius of curvature Rb is smaller than the radius of curvature Rc at a point of the fourth curved surface 16, and the radius of curvature Rc is smaller than the radius of curvature Rd at a point Q (end of the fourth curved surface 16). In the embodiments, the radius of curvature of the curved surfaces 14A, 14B, 16 gradually increases from the point K to the point N, so that vortices grow along the curved surfaces (FIGS. 4 and 5 ). In the embodiments, the curved surfaces 14A, 14B, 16 form a continuous surface without a discontinuity point (no step from the point K to the point N).In detail, the diesel engine 1 is divided into an engine body 2 and an upper body 3, and has the combustion chamber 10 between the engine body 2 and the upper body 3.For example, the piston 5 having a recessed combustion chamber 10 recessed on a piston top 5 athat comes into contact with a head bottom 6 aof the upper part 3 is disposed in the engine body 2 that is the same as a common cylinder block. Thus, the engine body includes an oil pan and a crankshaft configured with a cylinder block, and the cylinder block is connected to the piston 5 and outputs the reciprocating motion of the piston 5 as engine torque.The upper part 3 includes, for example, a cylinder head 6 having the head bottom 6 athat comes into contact with the top 5 aof the cylinder 5, and the cylinder head 6 includes an intake valve 8- 1 for opening / closing an intake port 7- 1 for supplying air to the intake combustion chamber 10, an exhaust valve 8- 2 for opening / closing an exhaust valve 7- 2 for discharging exhaust gas from the intake combustion chamber 10, and an injector 9 for spraying fuel to be burned with compressed air at a high pressure into the intake combustion chamber 10 in a liquid state. Consequently, the upper part 3 has the cylinder head 6, a cylinder head cover and a camshaft, and the camshaft controls the valve timing of the intake and exhaust valves 8-1 and 8-2.For example, the penetrating combustion chamber 10 has an inner space which is divided into a surface of the upper end 11, a profile 13, a cone 17 and a tooth 19. The top end 11 is stepped on the piston top 5a to form the top of the re-initiating combustion chamber 10, the tooth 19 projects upwardly midway in the re-initiating combustion chamber 10 at the tip of the cone 17 which continues to the underside of the re-initiating combustion chamber 10, the profile 13 has a bowl rim 16, a protrusion 15 and an incline 14 which continues from the underside of the cone 17 to the top of the top end 11, whereby a lower inner wall is defined by the bowl rim 16 and an upper inner wall is defined by the protrusion 15 and the incline 14. Thus, the wall of the injection combustion chamber 10 is composed of the lower inner wall and the upper inner wall.Thus, the combustor 10 is a left-right symmetrical cross section with the wave therebetween.With respect to the arrangement of the injection combustion chamber 10 of FIG. 2, a particular shape with respect to the top end 11, the slope 14, the protrusion 15, the bowl rim 16, the cone 17 and a tine 19 and the relation structure are exemplarily shown.The upper end 11 is formed, for example, to have a combustion chamber increasing depth G with respect to the piston top 5 aof the piston 5 by cutting the piston top 5 a. Consequently, the combustion chamber increasing depth G of the upper end 11 increases the volume of the combustion chamber defined by the inner wall surrounding the center formed wave 19.For example, the slope 14 exits from a slope origin at the top end 11 and projects inwardly toward the protrusion 15 in the combustion chamber, and the slope origin defines a slope curvature Ra. The protrusion 15 takes its exit from a protrusion starting point at the end point of the slope 14 and protrudes inwardly toward the bowl rim 16 in the combustion chamber, and the protrusion starting point defines a protrusion curvature Rb. Consequently, the slope 14 and the protrusion 15 form a profile 13 forming the upper inner wall. In this case, the inclination curvature Ra is set to about 1-3R (curvature) and the protrusion curvature Rb is set to about 1-5R (curvature).For example, the bowl rim 16 takes its exit from a bowl rim starting point at the end point of the protrusion 15 to a bowl rim end position at the end point of the cone 17 and is recessed outward in the combustion chamber, thereby forming a recessed space forming a bowl rim bottom. In particular, the trough edge starting position defines a bottom side curvature Rc and the trough edge end position defines a cone curvature Rd. Consequently, the trough edge curvature forming the recessed space of the trough edge 16 is divided into the bottom curvature Rc continuing to the protrusion 15 and the cone curvature Rd continuing to the cone 17. Furthermore, the trough edge 16 is contained in the profile 13 which forms the lower inner wall and forms the underside together with the cone 17. In this case, the lower surface curvature Rc is set to about 3 ~ 10 R (curvature) and the cone curvature Rd is set to about 15 R (curvature). Thus, the underside of the combustion chamber is formed by the bowl rim underside, which consists of an upper underside, which has about 3-10 R (curvature) and is formed on the projection 15, and a lower underside, which has about 15 R (curvature) and is formed on the cone 17, and thereby has a two-stage curvature, which consists of two continuous curvatures. Consequently, the lower surface of the combustion chamber conveys small vortices through the upper lower surface of the bowl rim lower surface and the lower lower surface of the bowl rim lower surface, thereby promoting the growth of large vortices.For example, the cone 17 continues its exit from the cone exit point at the end point of the trough 16 (lower bottom end of about 15 R (curvature)) to the wave 19. Consequently, the cone 17 is formed in the shape of a truncated circular cone with its tip removed to form the planar wave 19 at the top, and the oblique side of the truncated cone continuing from the trough edge 16 to the wave 19 forms a straight portion.For example, the tine 19 is positioned at the center of the combustion chamber and is a cut surface formed by cutting the tip of the cone 17, thereby forming the cone 17 into a truncated cone shape. In particular, the cut surface of the tooth 19 is formed straight, a tooth diameter d being defined thereby.A combustor height ratio and a combustor diameter ratio are defined by, for example, the parts of the re-entry combustor 10.For example, the combustion chamber height ratio is set on the condition that the distance between the piston top 5 aand the bowl edge bottom of the bowl edge 16 is a combustion chamber height H, the distance between the piston top 5 aof the piston 5 and the intersection of the cone 17 is a tooth depth h, and the distance between the piston top 5 aof the piston 5 and the top 11 is the combustion chamber increasing depth G. In this case, assuming that the combustor height H is 100%, the tooth depth h is about 25-42% and the combustor enlargement depth G is about 4-12%.Accordingly, when the combustion chamber height H is 12-17 mm, the tooth depth h is about 3-7 mm and the combustion chamber enlarging depth G is about 0.5-2 mm.For example, the combustor diameter ratio is set on the condition that the size having the bowl edge curvature center of the bowl edge 16 with respect to the center in the combustor is a combustor reference diameter D 1, the size having the bowl edge curvature Rc of the bowl edge 16 with respect to the center in the combustor is a maximum combustor diameter D 3, the size having the protrusion curvature Rb of the protrusion 15 with respect to the center in the combustor is a minimum combustor diameter D 2, and the size having the tooth 19 with respect to the center in the combustor is a tooth diameter d. In this case, when the reference combustor diameter D1 is 100%, the minimum combustor diameter D2 is about 120-1335, the maximum combustor diameter D3 is 120-140%, and the spike diameter d is 10-15%.Accordingly, when the reference combustor diameter D1 is φ30~50 mm, the minimum combustor diameter D2 is φ40~60 mm, the maximum combustor diameter D3 is φ42~62 mm, and the tooth diameter d is φ3~7 mm. Ø means diameter.FIGS. 3, 4, 5 to 6 exemplarily show a large vortex generated in the re-entering combustion chamber 10 and a flow generated toward the center in the combustion chamber when fuel is sprayed, and a 3D combustion analysis.Referring to FIG. 3, in an intake stroke of the piston upon operation of the diesel engine 1, the intake valve 8-1 is opened and air flows into the compression combustion chamber 10 through the intake port 7-1, and the injector 9 sprays fuel in a combustion stroke of the piston 5.Consequently, fuel is sprayed to the profile 13, thereby forming flows in which a part of the sprayed fuel moves to the slope 14 and the most part of the sprayed fuel moves to the trough edge 16 with the protrusion 15 of the profile 13 between them. In this case, the inclination curvature Ra of the inclination 14 and the protrusion curvature Rb of the protrusion 15 promote the flows of the sprayed fuel.With respect to the 3D velocity field in the re-entry combustion chamber 10 of FIG. 4, the sprayed fuel and air in the center in the combustion chamber collide against the protrusion 15 and flow down the protrusion curvature Rb toward the bowl rim 16, thereby forming a bowl rim flow. The bowl rim flow is promoted by the underside curvature Rc of about 3-10 R (radius) in the space of the bowl rim 16, and this promotion of the bowl rim flow increases the kinetic energy of the sprayed fuel.In particular, the straight portion of the cone 17 continuing to the wave 19 directs the bowl rim flow evenly to the center in the combustion chamber.Referring to FIG. 5, in the bowl rim flow, most of the sprayed fuel except a part of the sprayed fuel moving to the center peak 19 in the combustion chamber along the straight portion of the cone, increasing the kinetic energy, forms a swirl that is promoted by the cone curvature Rd that is about 15R and continues to the lower surface curvature Rc. Consequently, the vortex is promoted to grow into a vortex which rotates around the trough edge curvature Rc which is about 3 ~ 10 R, thereby growing the initial vortex into a large vortex.Referring to FIG. 6, which shows an analysis result when a large vortex is grown in the re-entry combustion chamber 10 by the large curvature of the bowl rim 16 and the bowl rim flow is guided to the air in the middle through the straight portion of the cone 17, so that all the air in the combustion chamber and replenishing air can be well burnt.As shown in the figure, the compression combustion chamber 10 greatly reduces NO and soot to Indicated Specific Fuel Consumption (ISFC), thereby significantly reducing smoke.As a result, the diesel engine 1 with the injection type burning heater 19 reduces soot, and therefore the life of a DPF (Diesel Particulate Filter) which is a post-processing device is increased, whereby fuel efficiency can be improved, and particularly a swirl control valve which is a device for reducing soot can be removed.As described above, in the re-entry combustion chamber 10 of the diesel engine 1 of the present embodiment, the profile 13 forms the inlet of the combustion chamber protruding inward in the combustion chamber and the bottom of the combustion chamber through a recessed space recessed outward in the combustion chamber. Further, the cone 17 is formed into a truncated cone shape protruding with a straight oblique side in the central space in the combustion chamber, and the upper end 11 enlarging the space of the combustion chamber is formed by widening the top of the profile 13, thereby forming a symmetrical structure. Consequently, a large vortex and a flow of the sprayed fuel moving to the center in the combustion chamber are formed. Therefore, the injection combustion chamber 10 is suitable for a super high injection pressure that cannot be obtained from the split spray type combustion chamber and the two-stage bowl type combustion chamber.

Claims

A compression combustion chamber (10) comprising: a profile (13) that forms the inlet of the combustion chamber (10) that is a protruding surface formed inward in the combustion chamber (10) and the bottom of the combustion chamber (10) that is a recessed space recessed outward below the inlet in the combustion chamber (10); a cone (17) that is formed into a truncated cone shape continuing from the profile (13) and protruding toward the central space in the combustion chamber (10); and an upper end (11) for increasing the space of the combustion chamber (10) by increasing the top of the combustion chamber (10) at the inlet of the combustion chamber (10), wherein the profile (13) is divided into an inclination (14), a protrusion (15), and a trough edge (16), the inclination (14) is an inclined surface, which continues from the upper end to the protruding surface, the protrusion is the protruding surface and connects the slope (14) and the bowl rim (16), thereby forming the inlet of the combustion chamber (10), and the bowl rim (16) forms the bottom of the combustion chamber (10) which is the recessed space, and the bowl rim (16) has a bowl curvature formed by the recessed space, and the bowl rim curvature is divided into a bottom curvature (Rc) which continues to the protrusion and a taper curvature (Rd) which continues to the taper (17).The compression combustion chamber (10) according to claim 1, wherein the cone (17) is the frustoconical shape with a straight tooth.The injection combustor (10) of claim 2, wherein the slope (14) continues to the protrusion (15) by a slope curve (Ra) formed from the top end.The injection combustor (10) of claim 3, wherein the tilt curve (Ra) has a radius of 1 - 3 mm.The injection combustor (10) of claim 2, wherein the protrusion (15) continues to the bowl rim (16) by a protrusion curve (Rc) formed from the top end (11).The injection combustor (10) of claim 5, wherein the protrusion curvature (Rb) has a radius of 1 - 5 mm.The injection type combustor (10) according to claim 2, wherein the radius center of the recessed space is set as the combustor reference diameter (D1), and when the combustor reference diameter (D1) is 100%, the minimum combustor diameter defined by the protrusion (15) is 120~135%.The injection combustor (10) according to claim 1, wherein the bottom curve (Rc) has a radius of 3 - 10 mm and the cone curve (Rd) has a radius of 15 mm or more.The injection combustor (10) according to claim 1, wherein the radius center of the recessed space is set as a combustor reference diameter (D1), and when the combustor reference diameter (D1) is 100%, the maximum combustor diameter defined by the bowl rim (16) is 120-140%.The injection combustor (10) according to claim 2, wherein the radius center of the recessed space is set as the combustor reference diameter (D1), and when the combustor reference diameter (D1) is 100%, the tooth diameter is 10-15%.The injection combustor (10) according to claim 1, wherein the top end (11) is formed by cutting the top of the profile (13) with a combustor enlarging depth (G) to enlarge the combustor (10), and when the height of the combustor (10) from the bottom to the top of the combustor (10) is 100%, the combustor enlarging depth (G) is 4~12%.The coiled combustor (10) of claim 2, wherein the tooth (19) has a tooth depth (h) and when the height of the combustor (10) from the bottom to the top of the combustor (10) is 100%, the tooth depth (h) is 25-42%.The injection combustion chamber (10) according to claim 1, wherein the truncated cone of the cone (17) has a cone angle (A) of 100-130° and a straight oblique side.A diesel engine with a piston having a compression combustion chamber (10) according to claim 1, defined by: a profile (13) that forms the inlet of the combustion chamber (10) protruding inward in the combustion chamber (10) and the bottom of the combustion chamber (10) through a recessed space recessed outward in the combustion chamber (10); a cone (17) formed into a truncated cone shape protruding with a straight oblique side in the central space in the combustion chamber (10); and an upper end (11) that increases the space of the combustion chamber (10) and is formed by widening the top of the profile (13).The diesel engine of claim 14, wherein the compression combustion chamber (10) has a left-right symmetrical structure with a center wave (19).The diesel engine according to claim 14, wherein the inlet of the combustion chamber (10) is formed by connecting the inclination curvature (Ra) and the protrusion curvature (Rb) to different sizes.The diesel engine according to claim 14, wherein the recessed space is formed by a bowl curvature, and the bowl curvature is formed by connecting the lower surface curvature (Rc) and the cone curvature (Rd) having different sizes.A diesel engine according to claim 14, wherein the cone (17) is a truncated cone and forms a centre peak in the combustion chamber (10).

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