Heating device for an exhaust system of an internal combustion engine

Abstract

To provide an economical heating device for an exhaust system for an internal combustion engine enabling complete fuel combustion (preventing unburned fuel from being introduced into an exhaust duct) and easily manufactured.SOLUTION: A heating device 6 for an exhaust system for an internal combustion engine includes: a tubular body 12 in which a combustion chamber 7 is provided; a fuel injector 9 injecting fuel into the combustion chamber 7; at least one inlet opening 18 connectable to a fan so as to receive an air current toward the combustion chamber 7; a supply channel 21 receiving air from the inlet opening 18, surrounding an end of the fuel injector 9 and ending at a nozzle 22 disposed around a spray tip of the fuel injector 9; and a spark plug 10 mounted through a side wall 16 of the tubular body 12. An axial distance X between the spray tip of the fuel injector 9 and a longitudinal axis 30 of the spark plug 10 is within a range from 33% to 100% of an inner diameter D of the tubular body 12.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority from Italian Patent Application No. 102021000001871, filed January 29, 2021, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a heating device for an exhaust system of an internal combustion engine. [Background technology]

[0003] The exhaust system of an internal combustion engine comprises an exhaust duct along which at least one device for the treatment of the exhaust gases coming from the internal combustion engine is installed, in particular there is always a catalytic converter (either an oxidation catalytic converter or a reduction catalytic converter), to which a particle filter can be added. Since the chemical reactions for converting unburned hydrocarbons, nitrogen oxides and carbon monoxide into carbon dioxide, water and nitrogen only occur when the operating temperature is reached, the catalytic converter needs to operate at a relatively high operating temperature in order to work (i.e. to carry out the catalytic conversion) (modern catalytic converters operate at temperatures approaching 800°C).

[0004] During the cold start phase (i.e. when the internal combustion engine is turned on after being switched off for a long time and thus the temperature of its different parts has reached the ambient temperature), the temperature of the catalytic converter remains significantly below its operating temperature for a relatively long time (even up to several minutes in winter and during urban travel when the internal combustion engine is idling or running very slowly). As a result, during the cold start phase, i.e. during the time when the catalytic converter has not yet reached its operating temperature, the purification effect of the catalytic converter is close to zero or, in any case, is hardly effective, and therefore polluting emissions are very high.

[0005] To speed up the attainment of the operating temperature of the catalytic converter, US Pat. Nos. 5,629,299, 5,729,313, 5,829,413, 5,929,529, and 5,929,530 propose installing a heating device along the exhaust duct, which burns fuel to generate a (very) hot airflow that flows through the catalytic converter. In particular, the heating device includes a combustion chamber, which is connected at its outlet to the exhaust duct (just upstream of the catalytic converter) and at its inlet to a fan, which generates the airflow that flows through the combustion chamber, which also contains a fuel injector that injects fuel that is mixed with air, and a spark plug that periodically generates a spark that ignites the air-fuel mixture to obtain combustion that heats the air.

[0006] In known heating devices, the combustion of fuel is not always complete under all operating conditions, and therefore it can happen (especially when large amounts of fuel are injected to generate large amounts of heat) that unburned fuel reaches the exhaust duct and burns inside the exhaust duct, thus determining a sudden, unexpected and unwanted temperature rise locally. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent Application Publication No. 0631039 [Patent Document 2] International Publication No. 2012139801 Brochure [Patent Document 3] U.S. Patent No. 8,006,487 [Patent Document 4] European Patent Application Publication No. 0590699 [Patent Document 5] Japanese Patent Application Laid-Open No. 2005-180371 [Patent Document 6] European Patent Application Publication No. 1939419 Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to provide a heating device for the exhaust system of an internal combustion engine, which allows complete fuel combustion (i.e., no unburned fuel is introduced into the exhaust duct), and which is simple and economical to manufacture. [Means for solving the problem]

[0009] According to the present invention there is provided a heating device for an exhaust system of an internal combustion engine according to the appended claims.

[0010] The appended claims describe preferred embodiments of the invention and form an integral part of this description.

[0011] The present invention will now be described with reference to the accompanying drawings, which show some non-limiting embodiments thereof. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic, partial view of an exhaust system of an internal combustion engine provided with a heating device according to the invention; [Figure 2] 2 is a schematic, longitudinal cross-sectional view, with parts removed for better clarity, of the heating device of FIG. 1; FIG. [Figure 3] FIG. 3 is a more enlarged view of a detail of FIG. 2. [Figure 4] 3 is a more enlarged view of a detail of FIG. 2 showing a different embodiment. [Figure 5] 2 is a schematic diagram of an alternative embodiment of a fuel injection generated by a fuel injector of the heating device of FIG. 1. [Figure 6] 2 is a schematic diagram of an alternative embodiment of a fuel injection generated by a fuel injector of the heating device of FIG. 1. [Figure 7] 2 is a schematic diagram of a spark plug of the heating device of FIG. 1. [Figure 8]8 is a schematic diagram of the electrodes of the spark plug of FIG. 7, highlighting the possible directions of the fuel jet emitted by the fuel injector. [Figure 9] 8 is a schematic diagram of an alternative embodiment of the electrodes of the spark plug of FIG. 7, highlighting possible directions of fuel jets emitted by the fuel injector. [Figure 10] 8 is a schematic diagram of an alternative embodiment of the electrodes of the spark plug of FIG. 7, highlighting possible directions of fuel jets emitted by the fuel injector. [Figure 11] FIG. 3 is a more enlarged view of a detail of FIG. 2 according to a further embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] In FIG. 1, the number 1 indicates as a whole an exhaust system of an internal combustion engine 2 .

[0014] The exhaust system 1 comprises an exhaust duct 3, which starts from the exhaust manifold of the internal combustion engine 2 and ends in a silencer 4, from which the exhaust gases are released into the atmosphere. Along the exhaust duct 3, at least one device 5 for treating the exhaust gases coming from the internal combustion engine is installed, in particular there is always a catalytic converter (either an oxidation catalytic converter or a reduction catalytic converter), to which a particle filter can be added. Since the chemical reactions for converting unburned hydrocarbons, nitrogen oxides and carbon monoxide into carbon dioxide, water and nitrogen only occur when the operating temperature is reached, the catalytic converter needs to operate at a relatively high operating temperature in order to operate (i.e. to carry out the catalytic conversion) (modern catalytic converters operate at temperatures approaching 800°C).

[0015] To speed up the heating of the treatment device 5, i.e. to enable the treatment device 5 to reach its operating temperature more quickly, the exhaust system 1 includes a heating device 6, which, by burning fuel, generates a (very) hot airflow, which flows through the treatment device 5.

[0016] The heating device 6 includes a combustion chamber 7, which is connected at its outlet to the exhaust duct 3 (just upstream of the treatment device 5), and at its inlet to a fan 8 (i.e., to an air pump), which generates an airflow that flows through the combustion chamber 7, in which there is also a fuel injector 9 for injecting fuel that is mixed with the air, and a spark plug 10 for periodically generating a spark that ignites the air-fuel mixture to obtain combustion that heats the air. The combustion chamber 7 of the heating device 6 ends in an outlet duct 11, which leads into the exhaust duct 3 (just upstream of the treatment device 5).

[0017] 2 , the heating device 6 comprises a tubular body 12 (e.g., cylindrical and with a circular or elliptical cross section) having a longitudinal axis 13, the tubular body 12 being bounded at two ends by two opposing base walls 14 and 15 and laterally by a side wall 16, which connects the two base walls 14 and 15 to one another. The base wall 14 is centrally perforated to accommodate a fuel injector 9, which is mounted coaxially with the tubular body 12 (i.e., coaxially with the longitudinal axis 13); in other words, the fuel injector 9 is mounted through the base wall 14 of the tubular body 12 to inject fuel into the combustion chamber 7.

[0018] Similarly, the base wall 15 is centrally drilled to fit the outlet duct 11, which terminates in the exhaust duct 3, i.e. the base wall 15 has an outlet opening 17 through which the hot air leaves the combustion chamber 7 where the outlet duct 11 begins.

[0019] According to Figure 2, through the tubular body 12 there is (at least) a portion of an inlet opening 18 which is connected to the fan 8 by means of an inlet duct 19 (shown in Figure 1) for receiving an airflow which is directed towards the combustion chamber 7 and mixed with fuel injected by the fuel injector 9. Preferably, air flows into the inlet opening 18 in a flow which is oriented tangentially (with respect to the tubular body 12), i.e. the inlet duct 19 is oriented tangentially (with respect to the tubular body 12).

[0020] 1, there is a check valve 20 in the region of the inlet opening 18, which allows only airflow towards the combustion chamber 7 (i.e. into the tubular body 12). Preferably, the check valve 20 is passive (i.e. does not include an electric, hydraulic or pneumatic actuator that generates movement) and is pressure controlled, opening only when the pressure upstream of the check valve 20 is higher than the pressure downstream of the check valve 20. The function of the check valve 20 is to prevent the exhaust gases from flowing back out of the inlet opening 18 when the heating device 6 is not in use (i.e. when the fan 8 is turned off) and thus being released into the atmosphere without passing through the treatment device 5. Alternatively, the check valve 20 can be mounted along the outlet duct 11, for example in the area of ​​the outlet opening 17, in which case the check valve 20 only allows air to flow out of the combustion chamber 7 (out of the tubular body 12) towards the exhaust duct 3, i.e. prevents exhaust gases from flowing from the exhaust duct 3 towards the combustion chamber 7 (into the tubular body 12).

[0021] According to FIG. 2, the heating device 6 includes a supply channel 21, which is completely housed inside the tubular body 12, receives air from the inlet opening 18, surrounds the end of the fuel injector 9 and terminates in a nozzle 22, which is positioned around the injection point of the fuel injector 9 (i.e., around the spray tip of the fuel injector 9, from which the fuel exits).

[0022] The spark plug 10 is mounted through the side wall 16 of the tubular body 12 to cause combustion of the air-fuel mixture that is obtained due to the mixing of air that enters the tubular body 12 through the inlet opening 18 and is introduced into the combustion chamber 7 by the nozzles 22 of the supply channel 21 with fuel that is injected into the combustion chamber 7 by the fuel injector 9. In particular, the side wall 16 of the tubular body 12 has a through-hole that is radially oriented (i.e. perpendicular to the longitudinal axis 13) and that houses inside (threaded into) the spark plug 10 (which is obviously radially oriented).

[0023] The heating device 6 includes a static mixer 23 (i.e., no moving parts), which has an annular shape and is arranged around the fuel injector 9 along the supply channel 21 and is configured to generate turbulence, in particular a vortex motion, in the air flowing towards the nozzle 22.

[0024] According to a preferred, but non-binding, embodiment shown in the accompanying figures, the feed channel 21 has a gradual decrease in cross-sectional area so as to determine the increase in air velocity downstream of the static mixer 23. In particular, downstream of the static mixer 23, the feed channel 21 has a beginning portion with a constant cross-sectional area, a middle portion with a gradually decreasing cross-sectional area, and an end portion with a constant cross-sectional area up to the nozzle 22.

[0025] The supply channel 21 is bounded on the outside by an (at least partially conical) outer tubular body 24 and on the inside by an (at least partially conical) inner tubular body 25, which surrounds the fuel injector 9 and internally houses the fuel injector 9 (i.e., serves as a receptacle for the end of the fuel injector 9). That is, the supply channel 21 is defined between the inner tubular body 25 and the outer tubular body 24. In particular, the two tubular bodies 24 and 25 alternate between conical sections (i.e., having a converging shape that gradually decreases in size) and cylindrical sections (i.e., having a shape of constant size); preferably, the end of the inner tubular body 25 has a converging taper (i.e., which gradually decreases in size towards the nozzle 22), while the end of the outer tubular body 24 has a cylindrical shape.

[0026] According to a preferred embodiment, the air enters the supply channel 21 in a tangentially oriented flow so as to have a vortex motion (which is subsequently enhanced by the action of the static mixer 23) that helps to mix with the fuel injected by the fuel injector 9; in other words, by introducing the oxidation air into the combustion chamber 7 through a duct oriented tangentially to the combustion chamber 7, the oxidation air flow is enabled to acquire a circular motion (which is further enhanced by the presence of the static mixer 23) so as to optimize the mixing of the air and fuel inside the combustion chamber 7.

[0027] According to Fig. 3, the fuel injector 9 is configured to spray at least 80% (preferably at least 90-95%) of the fuel against the inner surface 26 of the supply channel 21, i.e. the fuel injector 9 does not direct the fuel directly towards the outside of the supply channel 21, but instead directs the fuel against the inner surface 26 of the supply channel 21, so that the fuel leaving the fuel injector 9 hits the inner surface 26 before leaving the supply channel 21 through the nozzle 22. The impact of the fuel against the inner surface 26 makes it possible to break up the fuel droplets released by the fuel injector 9 in a very effective manner, thereby significantly improving the mixing of said fuel with the air flowing along the supply channel 21. The improved mixing between air and fuel ensures an ideal, in particular complete, combustion of the fuel and therefore prevents any unburned fuel from leaving the combustion chamber 7.

[0028] According to a preferred embodiment, the fuel injector 9 is configured to emit a fuel spray 27 having a hollow conical shape at the center, i.e., a ring-like shaped cross section, with fuel collecting at the periphery, and in particular, according to the embodiment shown in Figure 3, the outer surface of the fuel spray 27 has an opening angle α of about 70° (e.g., in the range between 65° and 75°) and the inner surface of the fuel spray 27 has an opening angle β of about 50° (e.g., in the range from 45° to 55°). In other words, the fuel injector 9 generates a fuel spray 27 having a conical shape (the apex of the cone is close to the injection nozzle) and a hole (i.e., a fuel-free area) in the center, also in the conical shape (the apex of the cone is close to the injection nozzle); therefore, the fuel spray 27 generated by the fuel injector 9 has the shape of a conical shell due to the presence of the central hole, i.e., a hollow conical shape.

[0029] When it is said that the fuel spray 27 generated by the fuel injector 9 has the shape of a conical shell (i.e., has a hollow conical shape), it is meant that most of the fuel exiting the fuel injector 9 spreads out in the space within the conical shell, but it should be pointed out that a very small (remaining) portion of the fuel may spread out differently. Furthermore, depending on how the fuel exit opening is fabricated, the fuel spray 27 exiting the fuel injector 9 may have a more symmetrical distribution about the longitudinal axis 13 (as shown in FIG. 5 ) or a less symmetrical distribution about the longitudinal axis 13 (as shown in FIG. 6 ). In particular, when the fuel injector 9 is of a “swirl” type, the fuel spray 27 exiting the fuel injector 9 has the shape shown in FIG. 5 , whereas when the fuel injector 9 is of a “multi-hole” type, the fuel spray 27 exiting the fuel injector 9 has the shape shown in FIG. 6 (FIG. 6 shows a “multi-hole” fuel injector 9 with six exit holes, but the number of exit holes may vary).

[0030] According to a preferred embodiment, the fuel injector 9 is of the "swirl" type, i.e. it imparts a rotational vortex motion to the injected fuel (i.e. a vortex motion in which the fuel rotates about the longitudinal axis 13 of the tubular body 12).

[0031] As described above, the supply channel 21 is bounded on the outside by an outer tubular body 24 (having an inner surface 26 of the supply channel 21) and on the inside by an inner tubular body 25, which surrounds the fuel injector 9 and houses the fuel injector 9 on the inside.

[0032] According to Figure 3, the outer tubular body 24 comprises a conical portion 28, which reduces in size towards the nozzle 22, and furthermore, according to a preferred embodiment shown in the accompanying figures, the outer tubular body 24 also comprises a cylindrical portion 29, which is arranged downstream of the conical portion 28 and terminates at the nozzle 22. According to a different embodiment not shown here, the outer tubular body 24 does not have the cylindrical portion 29 and therefore comprises only the conical portion 28. According to a further embodiment not shown here, the cylindrical portion 29 can also be replaced by a further conical portion having a smaller taper (convergence) than that of the conical portion 28.

[0033] In the embodiment shown in the accompanying figures, the fuel injector 9 is configured to spray at least a portion of the fuel onto the cylindrical portion 29 (or onto the further conical portion) of the outer tubular body 24, in particular the fuel injector 9 is configured to spray a majority (almost all) of the fuel onto the cylindrical portion 29 (or onto the further conical portion) of the outer tubular body 24. According to a different embodiment, the fuel injector 9 is configured to spray at least a portion of the fuel onto the cylindrical portion 29 (or onto the further conical portion) of the outer tubular body 24 and at least a portion of the fuel onto the conical portion 28 of the outer tubular body 24, for example the fuel injector 9 is configured to spray about half of the fuel onto the conical portion 28 of the outer tubular body 24 and about half of the fuel onto the cylindrical portion 29 (or onto the further conical portion) of the outer tubular body 24. According to a further embodiment, the fuel injector 9 is configured to spray at least a portion of the fuel onto the conical portion 28 of the outer tubular body 24, and in particular, the fuel injector 9 is configured to spray a majority (almost all) of the fuel onto the conical portion 28 of the outer tubular body 24.

[0034] 2 , the axial distance X (i.e., measured along the longitudinal axis 13 of the tubular body 12) between the spray tip of the fuel injector 9 (i.e., the injection point of the fuel injector 9) from which the fuel exits and the longitudinal axis 30 of the spark plug 10 is in the range of 33 to 100% of the inner diameter D of the tubular body 12 (i.e., the diameter D of the combustion chamber 7), preferably, the axial distance X is in the range of 50 to 100% of the inner diameter D of the tubular body 12, and in particular, the axial distance X is in the range of 60 to 90% of the inner diameter D of the tubular body 12. The tubular body 12 preferably has a circular cross-section, and therefore there is no doubt as to how the inner diameter D of the tubular body 12 must be measured to assess the axial distance X; however, it should be pointed out that if the tubular body 12 had an elliptical cross-section, the larger diameter D of the tubular body 12 would have to be taken into account to assess the axial distance X.

[0035] According to Figures 7 and 8, the spark plug 10 has only one inner electrode 31 and only one outer electrode 32, and according to variations shown in Figures 9 and 10, the spark plug 10 has only one inner electrode 31 and two outer electrodes 32 (Figure 9), or only one inner electrode 31 and four outer electrodes 32 (Figure 10), and according to a further variation not shown here, there could also be three outer electrodes 32.

[0036] 4 , the outer tubular body 24 has a through-opening 33 (i.e., a slit) through which the spray tip of the fuel injector 9 (i.e., the injection point of the fuel injector 9) from which the fuel flows is aimed directly at the electrodes 31 and 32 of the spark plug 10. Thanks to the presence of the through-opening 33, a limited portion 34 of the fuel jet 27 emitted by the fuel injector 9 does not strike the outer tubular body 24 but passes through the outer tubular body 24 until it reaches the electrodes 31 and 32 of the spark plug 10 directly. In other words, thanks to the presence of the through-opening 33, the limited portion 34 of the fuel jet 27 directly “wets” the electrodes 31 and 32 of the spark plug 10, creating a local fuel surplus (i.e., a locally richer mixture) around the electrodes 31 and 32 of the spark plug 10, which aids in the ignition of the flame and therefore aids in faster propagation of the flame to the rest of the mixture.

[0037] According to FIG. 4, the through opening 33 is shaped like a slit, i.e. has a circumferential dimension greater than its axial dimension, and preferably the circumferential side of the through opening 33 has an angle ranging from 30° to 60°.

[0038] 8, 9, and 10, the outer electrode 32 (or the outer electrodes 32) of the spark plug 10 is oriented so as not to obstruct (block) the limited portion 34 of the fuel spray 27 moving toward the inner electrode 31; i.e., the outer electrode 32 (or the outer electrodes 32) of the spark plug 10 is oriented so as not to cover (block) the inner electrode 31 from the limited portion 34 of the fuel spray 27. As a result, the spark generated between the two electrodes 31 and 32 is not covered (blocked) by the outer electrode 32 with respect to the limited portion 34 of the fuel spray 27. FIGS. 8 and 9 show both the portions 34 of the fuel spray 27 that have the correct orientation relative to the electrode 32 (i.e., they are not blocked by the electrode 32) and the portions 34 of the fuel spray 27 that have the wrong orientation relative to the electrode 32 (i.e., they are blocked by the electrode 32) and for this reason are "canceled" by means of an "X."

[0039] 3 and 4, the fuel jet 27 emitted by the fuel injector 9 is perfectly symmetrical with respect to the longitudinal axis 13 of the tubular body 12 (and of the fuel injector 9), i.e., the longitudinal axis 13 of the tubular body 12 coincides with the central axis of symmetry 35 of the fuel jet 27. On the other hand, in the embodiment shown in FIG. 11, the fuel jet 27 emitted by the fuel injector 9 is asymmetrical with respect to the longitudinal axis 13 of the tubular body 12 (and of the fuel injector 9), and therefore the fuel jet 27 is inclined toward the electrodes 31 and 32 of the spark plug 10, i.e., the central axis of symmetry 35 of the fuel jet 27 forms an angle γ (other than zero) with the longitudinal axis 13 of the tubular body 12. According to a preferred embodiment, the central axis of symmetry 35 of the fuel jet 27 is inclined towards the electrodes 31 and 32 of the spark plug 10 so as to form an angle γ with the longitudinal axis 13 of the tubular body 12 having a width ranging from 5° to 20°, preferably equal to about 13-15°. By inclining the fuel jet 27 towards the electrodes 31 and 32 of the spark plug 10, a local fuel surplus (i.e., a locally richer mixture) is created around the electrodes 31 and 32 of the spark plug 10, which aids in the ignition of the flame and therefore in the faster propagation of the flame to the rest of the mixture.

[0040] According to a preferred embodiment, the heating device 6 includes a control unit 36 ​​(schematically shown in FIG. 1 ) configured to control the overall operation of the heating device 6, i.e., to coordinately control the fan 8, the injector 9 and the spark plug 10, in order to achieve the desired objective as efficiently and effectively as possible (i.e., to heat the processing device 5 quickly without damaging the processing device 5 due to excessive temperatures).

[0041] 1, the heating device 6 includes a temperature sensor 37 arranged along the outlet duct 11 to measure the temperature of the hot air flowing through it, or alternatively, the heating device 6 includes a temperature sensor 38 arranged along the exhaust duct 3 downstream of the point where the outlet duct 11 branches (and upstream of the treatment device 5) to measure the temperature of the exhaust gas and hot air mixture flowing through the exhaust duct 3. Although in special applications both temperature sensors 37 and 38 may be present, in general there will be only one of the two temperature sensors 37 and 38. The control device 36 uses the readings of the temperature sensor 37 or 38 to control the combustion in the combustion chamber 7 (if necessary by means of feedback control) to heat the treatment device 5 quickly without damaging it due to excessive temperatures.

[0042] The embodiments described herein can for this reason be combined with one another without exceeding the scope of protection of the invention.

[0043] The heating device 6 described above has many advantages.

[0044] Firstly, the above-mentioned heating device 6 ensures complete fuel combustion (i.e. no introduction of unburned fuel into the exhaust duct 3) under all operating conditions (especially when large amounts of fuel are injected to generate large amounts of heat) thanks to the ideal mixing between the oxidation air introduced by the nozzles 22 of the supply channel 21 and the fuel injected by the fuel injectors 9.

[0045] Furthermore, the heating device 6 described above has a high heating power relative to its overall size, i.e., even though it is relatively small, the heating device 6 described above generates a high heating power.

[0046] Finally, the heating device 6 described above is simple and economical to manufacture, as it consists of a small number of parts with uncomplicated shapes that are easy to join by standard welding and joining. [Explanation of symbols]

[0047] 1 Exhaust system 2. Internal combustion engine 3 Exhaust duct 4 Silencer 5 Processing equipment 6 Heating device 7. Combustion chamber 8 Fans 9 Fuel Injectors 10 Spark Plugs 11 Exit duct 12 Tubular body 13 Longitudinal axis 14 Base wall 15 Base wall 16 side wall 17 Exit opening 18 Entrance opening 19 Inlet duct 20. Check valve 21 Supply Channels 22 nozzles 23 Static Mixer 24 Outer tubular body 25 Inner tubular body 26 Inner 27 Fuel injection 28 Cone part 29 Cylindrical part 30 Longitudinal axis 31 Inner electrode 32 Outer electrode 33 Through opening 34 parts 35 Axis of Symmetry 36 Control Unit 37 Temperature Sensor 38 Temperature Sensor α angle β angle γ angle X distance D diameter

Claims

1. A heating device (6) for an exhaust system (1) of an internal combustion engine (2), said heating device (6) comprising: a tubular body (12) inside which the combustion chamber (7) is obtained; a fuel injector (9) mounted through the base wall (14) of the tubular body (12) to inject fuel into the combustion chamber (7); at least one inlet opening (18) connectable to a fan (8) to receive an airflow directed towards the combustion chamber (7) and mixed with the fuel; a supply channel (21) entirely contained inside the tubular body (12), receiving air from the inlet opening (18), surrounding the end of the fuel injector (9) and terminating in a nozzle (22) disposed around the spray tip of the fuel injector (9); a spark plug (10) mounted through a sidewall (16) of said tubular body (12) to cause combustion of an air-fuel mixture; Including, The heating device (6) is characterized in that a distance (X) measured in an axial direction between the spray tip of the fuel injector (9) and the longitudinal axis (30) of the spark plug (10), i.e., along the longitudinal axis (13) of the tubular body (12), is in the range of 33% to 100% of the inner diameter (D) of the tubular body (12).

2. 2. The heating device (6) of claim 1, wherein the axial distance (X) is in the range of 50% to 100% of the inner diameter (D) of the tubular body (12).

3. 2. The heating device (6) of claim 1, wherein the axial distance (X) is in the range of 60% to 90% of the inner diameter (D) of the tubular body (12).

4. 4. The heating device (6) according to claim 1, 2 or 3, wherein the fuel injector (9) is configured to spray at least a portion of the fuel against an inner surface (26) of the supply channel (21).

5. 5. The heating device (6) according to claim 4, wherein the injector is configured to spray at least 80%, preferably at least 90%, of the fuel onto the inner surface (26) of the supply channel (21).

6. 6. The heating device (6) according to any one of claims 1 to 5, wherein the injector (9) is configured to emit a fuel jet (27) having a centrally hollow conical shape, i.e. an annular-like shaped cross section.

7. 7. The heating device (6) according to claim 6, wherein the outer surface of the fuel injection (27) has an opening angle (α) of about 70° and the inner surface of the fuel injection (27) has an opening angle (β) of about 50°.

8. 8. The heating device (6) according to claim 1, wherein the fuel jet (27) emitted by the fuel injector (9) is asymmetric with respect to the longitudinal axis (13) of the tubular body (12), such that the fuel jet (27) is inclined towards the electrodes (31, 32) of the spark plug (10).

9. 9. The heating device (6) according to claim 8, wherein the central axis of symmetry (35) of the fuel jet (27) forms a non-zero angle (γ) with the longitudinal axis (13) of the tubular body (12).

10. 10. The heating device (6) according to claim 9, wherein the angle (γ) between the central axis of symmetry (35) of the fuel injection (27) and the longitudinal axis (13) of the tubular body (12) is in the range of 5° to 20°.

11. 11. The heating device (6) according to any one of claims 1 to 10, wherein the fuel injector (9) is of the volute type and imparts a rotational vortex motion to the fuel.

12. 12. The heating device (6) according to any one of claims 1 to 11, comprising a static mixer (23) which is annular in shape and which is arranged around the fuel injector (9) along the supply channel (21) and which is configured to generate turbulence, in particular a vortex motion, in the air flowing towards the nozzle (22).

13. said supply channel (21) being delimited externally by an outer tubular body (24) and internally by an inner tubular body (25) which surrounds and internally houses said fuel injector (9); 13. The heating device (6) of any one of claims 1 to 12, wherein the outer tubular body (24) is initially separate and independent from the tubular body (12) and is completely contained within the tubular body (12).

14. An exhaust system (1) for an internal combustion engine (2), said exhaust system (1) comprising: an exhaust duct (3) starting from the exhaust manifold of the internal combustion engine (2) and ending in a silencer (4) through which the exhaust gases are discharged into the atmosphere; an exhaust gas treatment device (5) arranged along the exhaust duct (3); a heating device (6) connected to the exhaust duct (3) upstream of the treatment device (5) by means of an outlet duct (11) coming from the exhaust duct (3), designed to generate a hot air current by burning a fuel, and manufactured according to any one of claims 1 to 13; An exhaust system (1) comprising:

15. The heating device (6) a temperature sensor (37, 38) located along the outlet duct (11) or along the exhaust duct (3) downstream of the point where the outlet duct (11) branches off; a control unit (36) for regulating the combustion in the heating device (6) according to the measurements provided by the temperature sensors (37, 38); 15. The exhaust system (1) according to claim 14, comprising:

Images