US20080127641A1

US20080127641A1 - Exhaust system

Info

Publication number: US20080127641A1
Application number: US11/608,994
Authority: US
Inventors: Christian Kellermann
Original assignee: Dolmar GmbH
Current assignee: Makita Engineering Germany GmbH
Priority date: 2005-12-14
Filing date: 2006-12-11
Publication date: 2008-06-05
Also published as: EP1798391A2; JP2007162692A; CN1982662B; CN1982662A; DE202006013247U1; EP1798391A3

Abstract

In order to provide an exhaust system for a combustion engine with an outer casing in which hot exhaust gas is introduced through an exhaust inlet and discharged from an exhaust outlet wherein the exhaust outlet is of a tubular, more preferably having a circular or oval cross section design which, in a simple way, preferably effectively lowers the exhaust gas temperature in the exhaust outlet it is proposed that arranged in the area of the tubular exhaust outlet is an exhaust swirling device having at least one guide blade through which the exhaust gas is deflected in the exhaust outlet.

Description

TECHNICAL AREA

The present invention relates to an exhaust system for a combustion engine with an outer casing in which hot exhaust gas is introduced through an exhaust gas inlet. Such an exhaust system can be used for a four-stroke or a two-stroke petrol engine. Since the exhaust system itself is of a particularly compact design it can also be utilised with hand-operated machines such as petrol engine driven disc grinders, chainsaws, hedge clippers or similar. After treatment of the exhaust gas within the exhaust system the exhaust gas is discharged into the environment from the exhaust outlet. The treatment of the exhaust gas can be a measure for sound absorption of the exhaust gas noise, for pollutant reduction of the exhaust gas or for cooling the exhaust gas or similar. In this way the exhaust gas is treated by the exhaust system so that it is subsequently discharged into the environment through the exhaust outlet. The exhaust gas outlet in this case is designed in the shape of a tube especially with a circular or oval cross section.

PRIOR ART

Arranging an exhaust gas swirling device within an exhaust system is generally known from the prior art. Here, these swirling devices generally serve to extinguish glowing particles in the combustion exhaust gas so that these are not discharged into the environment through the exhaust gas outlet. For example DE-PS 948 210 discloses an exhaust system with a so-called cyclone winding or arrangement. Here, brought about by the cyclone arrangement, the exhaust gases are imparted rapid rotary motion as a result of which the glowing particles present in the exhaust gas are squashed against the inside of the exhaust system and quickly and safely extinguished as a consequence. However, this cyclone is arranged within the exhaust system, i.e. far upstream of the exhaust outlet, so that the glowing particles can still be extinguished on the inside of the exhaust system.
In addition it is known from the prior art that a long exhaust gas duct is arranged for instance behind an exhaust element to cool down the converted exhaust gases. Here, the exhaust gas duct itself can serve as spark extinguisher in that it assumes a zigzag type or arched course. As a rule, the hot exhaust gases are then directly discharged from the exhaust duct into the open or the environment. However, very high exhaust gas temperatures still occur behind the exhaust outlet in this case.

Presentation of the Invention, Object, Solution, Advantages

Since the problem mentioned before mainly occurs with highly compact exhaust systems, additional slits or openings are arranged in the prior art in the outer casing of the exhaust system through which fresh air is able to enter the exhaust system and is redirected into the environment through the suction of the hot combustion exhaust gas. Through the much cooler fresh air, mixing of the hot exhaust gases with the cool ambient air occurs even within the exhaust system. Injectors are also known which serve for the cooling of the hot exhaust gas at the exhaust outlet but which are little effective because of the pulsating flow of the exhaust gas. As a consequence, very high temperatures still occur directly after the exhaust gas outlet in the exhaust flow. These high temperatures can pose a risk of injury especially in the case of portable machines with combustion engines. They additionally pose a fire hazard through the hot exhaust gases.
Before this background it is the object of the present invention to provide a compact exhaust system which, in a simple way, lowers the exhaust gas temperature in the exhaust outlet as effectively as possible. Here, previously known designs of exhaust systems are to be preferably used in order to achieve an economical solution as well.
To solve this object an exhaust system with the features of claim 1 is proposed.
With the exhaust system according to the invention it is intended that an exhaust gas swirling device is arranged in the area of the tubular exhaust outlet, having at least one guide blade through which the exiting exhaust gas is deflected or swirled in the exhaust outlet. The exhaust swirling device can be provided before or in the exhaust outlet, or the exhaust swirling device itself constitutes the exhaust outlet. It is further intended through the invention that the exhaust swirling device has at least one guide blade through which deflection or swirling of the exhaust gas with the ambient air takes place. In this way it is possible to transform a possible laminar flow of the exhaust gas into a turbulent flow of the exiting exhaust gas which directly intermixes with the cool ambient air after the exhaust outlet. By using the exhaust gas swirling device according to the invention in the area of the exhaust outlet the exhaust gas is rapidly rotated through the existing guide blades. Owing to the centripetal force the exhaust gas is greatly fanned out in the ambient air on leaving the exhaust outlet. The exhaust gas can thus be mixed and cooled with the ambient air over a considerably shorter distance. Consequently the exhaust swirling device according to the invention does not serve as spark extinguisher within an exhaust system as is known from the prior art but the exhaust swirling device serves exclusively for the reduction of the exhaust temperature downstream of the exhaust outlet. Since, with the application intended here, the exhaust swirling device itself only has a depth of a few centimetres the demanded compact design of the exhaust system can be realised. The exhaust swirling device can also be integrated in already existing exhaust system designs. Greater depths are possible if the requirement of compact design is not as great as for instance with lawnmowers.
Additional advantageous designs of the exhaust system are mentioned in Sub-claims 2-24.
To preferably achieve an uneconomical design of the exhaust system and obtain simple assembly of the exhaust system it can be designed that the exhaust swirling device is provided as an independent component in the area of the exhaust outlet. Consequently no major changes to the previous manufacture of the known exhaust systems are necessary and the assembly of the exhaust system is also hardly affected by the exhaust swirling device. As a result, the exhaust swirling device can simply be inserted in the planned exhaust outlet as an independent component. However, it must be ensured that the exhaust swirling device is not forced from the exhaust outlet by the hot exhaust gas flow. To this end, the exhaust swirling device can be arranged positively and/or non-positively in the exhaust outlet. Here it is conceivable to attach the exhaust swirling device in the exhaust outlet using a screw, rivet, welded, soldering and/or clamping connection or to secure it in the exhaust outlet by way of a bayonet closure.
It has also proved to be practical to arrange the exhaust swirling device in a separate casing. Thus, the exhaust swirling device largely contains a casing and an insert having the guide blade provided in the casing. The additional casing can be used for securing the exhaust swirling device in the exhaust outlet while the fastening possibilities mentioned in the previous paragraph can be employed. To keep the flow resistance of the exhaust swirling device as low as possible it is advisable to provide a circular cross section for the casing of the exhaust swirling device. Obviously the present invention is not however restricted to a casing with a circular cross section so that oval or other kinds of cross sectional areas can also be employed. To ensure that the exhaust gas is transformed into a turbulent flow small projections can be arranged on the inside of the casing. Likewise, the inside of the casing can have a rough surface. In addition, the exhaust swirling device can be arranged in the exhaust outlet such that a short pipe section of the exhaust outlet joins the exhaust swirling device before the exhaust gas leaves the casing or enters the environment. This measure can be used to cause the ambient air to be drawn into the exhaust outlet where it mixes with the outflowing exhaust gas, in this way lowering the discharge temperature as a whole before the exhaust gas finally leaves the casing of the exhaust system.
In order to preferably utilise the entire cross sectional area of the casing for the exhaust flow it is advisable to form a small-area central mounting surface as a fixed element on which the guide blade can be centrally attached. As a result, the entire exhaust flow can be deflected or swirled through the guide blades to effectively avoid temperature peaks in the exhaust flow. As an option it is possible to omit the mentioned fixed element in form of a central mounting surface to utilise the entire cross sectional area of the casing for the complete exhaust flow whereby the guide blades cannot be attached centrally. In this case the central cross sectional area of the exhaust swirling device is of an open design.
To achieve economical manufacture of the exhaust swirling device a sheet metal design can be provided. Here, the casing as well as the insert with the guide blades can consist of sheet metal. These sheet metal designs can be manufactured through a deep drawing method or another forming method. With this version it is also possible to form the exhaust swirling device from the outer casing, especially a casing shell of the exhaust system. Consequently a connection of the exhaust swirling device with the exhaust system can be omitted since these two components are of a single piece and uniform material design. It is also conceivable to form only the casing or the insert of the exhaust swirling device from the outer casing of the exhaust system.
With another embodiment of the exhaust system it is conceivable that the exhaust swirling device, especially its insert with the guide blades, consists of a casting. Here it is practical for the casting to be a precision casting. Although a casting is more expensive in manufacture than a comparable sheet metal design but the design freedom is greater so that for instance profiled guide blades can be cast. Obviously the entire exhaust swirling device, i.e. insert and casing, can be designed as one or several casting.
With a particularly interesting further development of the exhaust swirling device it is intended that a triangular opening be provided for each guide blade through which a part of the exhaust gas or the exhaust flow is directed. Here, the nth part of the exhaust gas is generally directed via the nth guide blade through the n th opening. Consequently two, three or several guide blades can be present for the exhaust swirling device. Here, the exhaust gas or a part of the exhaust gas first flows in the flow direction along the guide blades in order to be subsequently directed into the ambient air through the triangular opening. By using n guide blades the exhaust flow is fanned out into n parts.
It is also conceivable that the guide blades have circular segment shape surfaces which more preferably have one flat or flat surfaces. When using n guide blades 360°/n circular arc shaped surfaces will then be used for the guide blades. Likewise, a guide blade can also have an arched wave-shaped or bent surface, more preferably if this is designed as a short turbine-type or propeller-type blade. As an option, the guide blades can also be arranged in uneven distribution over the circumference of the exhaust outlet, i.e. adjacent guide blades each can have different angles relative to each another.
In order to preferably use the entire cross section of the exhaust swirling device for the exhaust outlet it is practical that the approximate width of a guide blade corresponds to a radius of the exhaust swirling device. Thus, the flow resistance of the exhaust swirling device can be clearly reduced. To this end the central mounting of the guide blades, if available, should be of a particularly space saving or small design. This mounting surface is generally arranged around the centre of the exhaust swirling device. Likewise, it is advisable to arrange all guide blades symmetrically even around the centre point or the longitudinal axis of the exhaust swirling device. In this way, it is then possible to guarantee even and effective mixing of the exhaust gas with the ambient air. However, the invention is not restricted to symmetrical guide blades so that the individual guide blades can also be further developed geometrically different.
In addition it is practical if the area of all openings for a part flow of the exhaust gas is at least as large as the cross sectional area of the exhaust outlet. Thus, there is no cross sectional reduction which results in increased flow resistance. Here, the passage area of an opening for a part flow of the exhaust gas is largely connected also with the axial depression of the relevant guide blade. While it can be determined that the greater the area of the passage opening for the respective part flow of the exhaust gas, the greater also the axial depression of the guide blade. In an advantageous way, the axial depression of the guide blade is 5-70%, particularly advantageous 10-50% and highly advantageous 15-30% of the diameter of the exhaust duct. Through this diameter-height ratio in the exhaust swirling device it is possible to achieve an optimum flow of the exhaust gas. When using a two-stroke engine the exhaust swirling device can also be utilised to provide the necessary flow resistance for optimum engine charging if applicable. In accordance with this, the exhaust swirling device, especially its flow resistance, must be adjusted to suit the combustion engine.
To achieve comprehensive swirling of the exhaust gas with the ambient air it is practical that the exhaust swirling device discharges the exhaust gas largely tangentially to its longitudinal axis or helically. Since the exhaust gas is also forced out of the exhaust outlet in the direction of the longitudinal axis (i.e. axially) comprehensive three-dimensional mixing of the exhaust gas with the ambient air also takes place. Consequently the exhaust gas significantly cools down even at a short distance behind the exhaust outlet whereby this distance amounts to a few centimetres. It is also conceivable that the exhaust swirling device discharges the exhaust gas largely radially to the longitudinal axis of the exhaust swirling device. In this case, the same positive effects as previously described occur as well. To discharge the exhaust gas from the exhaust swirling device or the exhaust outlet as desired the geometry of the guide blades must be suitably adapted. Here it is advisable to arrange the guide surfaces similar to turbine blades to impart the desired swirl to the exhaust gas. To this end, the rotation-symmetrically arranged guide blades if applicable are similar to an aircraft propeller having n propeller blades. In this case, the individual propeller blades can be arranged obliquely to the flow direction of the entering exhaust gas. Owing to the large number of development possibilities, desired swirling of the exhaust gas with the ambient air can be realised.
In addition, the exhaust system according to the invention can be practically provided with at least one catalyst element for exhaust treatment. By using one or several catalyst elements retreatment of the exhaust gas with the (chemical) components contained in the exhaust gas is made possible. In this case, the existing hydrocarbons are converted into carbon dioxides and water or carbon monoxides for instance with the help of the residual oxygen content. However, since additional heat is liberated during this chemical conversion process the already hot exhaust gases are heated additionally. Thus it is further practical to pre-cool the exhaust gases directed through the catalyst element by means of a downstream exhaust duct even within the exhaust system. Here, the sparks in the exhaust gas should be extinguished at the same time. To this end an additional spark protection screen can be arranged especially before or in the exhaust swirling device. This spark protection screen serves to filter any remaining sparks from the exhaust gas so that these do not enter the environment. With a particularly simple design the spark protection screen can be arranged directly before or after the guide blades and can be easily replaced for maintenance purposes provided the exhaust swirling device is arranged on the exhaust system or in the exhaust outlet by means of a reversible non-permanent connection. Consequently the spark protection screen can be replaced or maintained directly when the exhaust swirling device is disassembled.
In a particularly interesting embodiment of the exhaust system it can be provided that the catalyst element is arranged in a catalyst chamber and the exhaust gases directed from the catalyst chamber are directed through an exhaust duct to the exhaust swirling device before the exhaust gas enters the environment through the exhaust outlet. In addition, it is possible that the spark protection screen already described is employed between the exhaust duct and the exhaust swirling device. Such an exhaust system according to the invention is not only of a compact design but also satisfies the legal environmental regulations.
In addition, the invention is also aims at an exhaust swirling device according to claim 25. This exhaust swirling device has the characteristics from any of the claims 1 to 24.

SHORT DESCRIPTION OF THE DRAWINGS

Different embodiment examples of the inventions are described in more detail by means of the enclosed drawings. It shows in purely schematic representation:

FIG. 1 in three-dimensional view an exhaust system with an exhaust swirling device according to the invention having five propeller-type guide surfaces,

FIG. 2 in three dimensional exploded view a similar exhaust system according to the invention—as in FIG. 1—with an exhaust swirling device with four guide blades,

FIG. 3 in a diagram-type view an exhaust swirling device with five propeller-type guide blades,

FIG. 4 a, b, c in three different three-dimensional views an insert for an exhaust swirling device having a total of four flat and circular segment shaped guide blades,

FIG. 5 a, b a further insert for an exhaust swirling device also having four flat and circular segment shaped guide blades however, of open design in the central cross sectional area, and

FIG. 6 a to e another version for an exhaust swirling device in various views where the exhaust swirling device is partially formed from the exhaust system, and

FIG. 7 a to d in various views an exhaust system with the exhaust swirling device from FIGS. 6 a to 6 e.

BEST WAY TO PERFORM THE INVENTION

FIG. 1 shows an exhaust system 100 according to the invention in three-dimensional representation. Here, the exhaust system 100 has an exhaust swirling device 20 arranged in the exhaust outlet 12. This exhaust outlet 12 is located in an upper casing shell 11 which, together with an outer casing shell 11, forms the outer casing 10. The two lower and upper casing shells 11 can be connected with each other gas tight through a welded connection, flanging or through the fasteners 19 shown. No exhaust inlet is shown in FIG. 1 as a result of which the exhaust flow 31 is able to directly enter the exhaust system 100 from a cylinder of the combustion engine. As can be seen however an exhaust swirling device 20 is employed which has a total of 5 propeller-type guide blades 23 while the respective guide blades are arranged obliquely relative to the entering exhaust flow. As a result, the exiting exhaust flow 31 is imparted a swirl through which the exhaust gas 31 is swirled or mixed with the ambient air directly behind the exhaust outlet 12. In order to preferably avoid causing any flow losses through the additionally employed exhaust swirling device 20 the individual guide blades 23 reach from the centre point 27, which also forms the longitudinal axis of the exhaust swirling device, to the circular inner surface of the exhaust duct 15. Consequently the entire cross sectional area of the exhaust swirling device 20 or the exhaust outlet 12 is utilised for swirling the exhaust flow 31. By means of this it is possible to avoid a laminar flow in the exhaust flow 31. This causes optimum swirling of the exhaust gas directly after discharge from the exhaust outlet 12.
FIG. 2 shows another exhaust system 100 according to the invention where an exhaust swirling device 20 is likewise provided in the exhaust outlet 12. This exhaust swirling device 20 mainly contains a separate casing 21 and an insert 22 provided in the casing 21 on which the guide blades 23 are arranged. Consequently the exhaust swirling device 20 is constructed of two parts. As a result, economical manufacture of the exhaust swirling device 20 can be achieved. Assembly of the exhaust swirling device 20 is also simplified through this modular construction of the exhaust system 100. In addition, the exhaust system 100 has a catalyst element (not shown) which is arranged within a catalyst chamber 13. An exhaust duct 15 starts from the catalyst chamber 13 which is of a meander-type design and terminates at the exhaust swirling device 20. Between the exhaust duct 15 and the exhaust swirling device 20 at least one spark protection screen can be additionally arranged. In order to bring about an easy further development of the catalyst chamber 13 and the exhaust duct 15, two chamber halves 14 are provided which simultaneously form the catalyst chamber 13 and the exhaust duct 15. These two chamber halves 14 are an upper and lower chamber half 14 which themselves can consist of formed sheet metal parts. These two chamber halves 14 are held approximately centrally in the exhaust system 100 through spacers 17. To join the upper chamber half 14 with the lower chamber half 14 additional fasteners 19, consisting of a screw nut connection, can be provided. It is also conceivable that the two chamber halves 14 are joined to each other through flanging over of their edge areas. When using additional fasteners 19 it is advantageous to also join the exhaust swirling device 20 or its casing 21 with the chamber halves 14. To this end, openings 30 are provided in the casing 21 of the exhaust swirling device 20 which are provided congruently with additional openings 30 in the chamber halves 14.
To securely mount the insert 22 in the casing 21 of the exhaust swirling device 20 it can be provided positively and/or non-positively in the casing 21. It is also conceivable to jam the insert 22 between the edge of the exhaust outlet 12 and the swirling device casing 21. With a special version the insert 22 can even be arranged so that it can rotate in casing 21.
In addition, a flow plate 16 with openings for exhaust gas passage is provided with the exhaust system 100 from FIG. 2 below the catalyst chamber 13. Thus this flow plate 16 is arranged between the lower chamber half 14 and the lower casing shell 11. A flange disc 18 can also be present between the flow plate 16 and the lower casing shell 11.
FIG. 3 shows an exhaust swirling device 20 in three-dimensional representation. With this exhaust swirling device 20 the casing 21 consists of a formed sheet metal part. In casing 21, the insert 22 with a total of five propeller-type guide blades 23 is arranged. These guide blades 23 have a circular segment type outline while the circular segments roughly form an approximate angle of 72° (360°/5=72°, since five guide blades). The surfaces of the guide blades 23 are arranged obliquely or tilted relative to the flow direction of the entering exhaust flow 31. The width 28 of the guide blades 23 largely runs from the centre 27, which is designed as a fixed element, to the circular or oval edge of the cylinder-type insert 22. The centre point 27 or the longitudinal axis 27 is formed by a five-star closed surface from which the five guide blades 23 radially originate or meet. It is also conceivable instead of the closed central surface for instance to employ a pipe or a continuous cylinder from the outer edge of which the guide blades 23 originate radially. This central cross sectional area can also be of an open design as will still be described in the following.
As can be seen in FIG. 3 the exhaust flow 31 is introduced into the exhaust swirling device 20 through the lateral opening 29. The exhaust flow 31 is then deflected through the casing 21 to impinge on the insert 22 with the guide blades 23. Here, at least one spark protection screen can be additionally employed in the casing 21. This spark protection screen can be arranged and attached between the casing 21 and the upper chamber half 14. The exhaust swirling device 20 also has a short pipe section behind the guide blades 23 which can either be formed by the exhaust swirling device 20, more preferably the insert 22, or by the tubular exhaust outlet 12.
FIGS. 4 a, b and c show an exemplary embodiment for an insert 22 of the exhaust swirling device 20 in three dimensional representation. Here, the individual FIGS. 4 a, b and c each show different views of the same three-dimensional element 22. To illustrate the operation of the exhaust swirling device 20 or the insert 22 and the guide blades 23 arranged on it, the exhaust flow 31 is shown as an example in bold arrows.
FIG. 4 a shows the insert 22 largely from its front 24. Here, the front 24 meets the exhaust flow 31. This exhaust flow 31 now impinges on the circular segment shaped guide blades 23 which run obliquely to the back or axially to the back. In order to preferably achieve a stable attachment of the guide blades 23 a cross is provided as a fixed element in the front 24. A side of the guide blade 23 originates from each of the sides of the cross. This side determines the width 28 of the guide blade 23. The width 28 largely corresponds to the radius of the cylinder shaped insert 22 or the circular casing 21. Once the exhaust gas 31 impinges on the guide blades 23 directed obliquely to the back it is directed tangentially to the longitudinal axis 27 through triangular openings 26 by the flat guide surfaces. A triangular opening 26 each is provided at the end of the open side of the guide blade 23. Consequently 4 triangular openings 26 are also provided for the four guide blades 23. The triangular opening is formed, on the one hand, by the unsecured side of the guide blade 23 and, on the other hand, by a side of the already described fixed cross on the front 24 and a side of the circular edge of the insert 22 originating from this and largely arranged orthogonally.
FIG. 4 b shows the same insert 22 from FIG. 4 a in three dimensional side view. The circular segment type guide surface 23 is clearly visible here which, in the present case, consists of a 90° circular arc segment (quarter circular arc). Also clearly visible is the triangular opening 26 through which the exhaust gas 31 deflected on the guide blade 23 is forced so that it can exit from the insert 22 or the exhaust outlet 12 with the swirl imparted. This swirl of the exhaust flow 31 is represented as an example by the two arrows 31. Obviously this exhaust flow can also be generated further radially outward. Through the number n of the guide blades 23 and the design of the individual guide blades 23 proper, direct influence can be exercised on the desired swirl of the exhaust flow 31.
The present insert 22 consists of a shaped sheet metal part which itself can be produced economically. To increase the lifespan of this insert 22 a special alloy can be used for the sheet metal. Stainless steel sheet can also be used. It is also conceivable to provide the insert 22 with a surface coating through which the service life or lifespan of the insert 22 can be extended.
FIG. 4 c shows the already known insert 22 from FIGS. 4 a, b. However, this time the back 25 of the insert 22 is shown in particular. Here, the exhaust gas 31 impinging on the front 24 is directed to the four guide blades 23 and, through these, through the four triangular openings 26 through the insert 22 proper. Through the four guide blades 23 the exhaust flow 31 is subdivided into a total of four part flows. These exhaust part flows exit tangentially or radially to the longitudinal axis 27 from the triangular openings 26. Consequently the exhaust flow 31 has been imparted the desired swirl through the guide blade 23 so that following its discharge from the exhaust outlet 12 it can directly intermix with the ambient air.
Another insert 22 for an exhaust swirling device 20 is shown in the FIGS. 5 a, b. This insert 22 also has four guide blades 23. The essential difference to insert 22 from the FIGS. 4 a, b, c consists in that here the guide blades 23 are not attached in the central cross sectional area. Consequently the central cross sectional area around the centre point 27 or the longitudinal axis 27 is designed open since a fixed element has been omitted. Thus the entire cross sectional area is open for the flow of the exhaust gas 31. However, as a result, the outer part of the exhaust gas 31 is deflected by the guide blades 23 to a greater extent than the inner part of the exhaust gas 31, which is able to pass through the (cross-shaped) opening 26 of the exhaust swirling device 20 more or less unaffected. Depending on the approach flow velocity of the exhaust gas 31, swirling of the inner part of the exhaust gas 31 can nevertheless take place since this part can be dragged along by the outer part of the exhaust gas 31. This is an indirect deflection or swirling of the inner part.
As is evident from FIG. 5 a, showing the insert 22 largely from its front 24, the insert 22 meets the exhaust gas 31 flow at its front 24 so that the exhaust gas 31 flows mixed and/or swirled from the insert 22 at the back 25.
In contrast with FIG. 5 a the insert 22 is largely shown from its back in FIG. 5 b. Here, the short pipe section of the insert 22 is particularly clearly visible behind the guide blades 23. This short pipe section in the present case has a circular cross section. The individual guide blades 23 in this case are only attached to the circular outer wall of the insert 22. Also clearly visible is the cross-shaped opening 26 in the central cross sectional area of the insert 22. In addition it is also visible how the exiting exhaust gas 31 is initially conducted in the short pipe section of the insert 22 before it is finally able to leave the exhaust outlet 12 into the ambient air.
Depending on the flow velocity of the exhaust flow 31, suction can partly form in the area of the centre point 27 causing the ambient air outside the exhaust system 100 to be centrally drawn into the exhaust outlet 12 or the insert 22. Thus mixing of the exiting exhaust gases within the exhaust outlet 12 already occurs. To further enforce this suction it is advisable to conduct the deflected or outwardly directed exhaust flows 31 within a short pipe section so that the suction effect forming in the area of the centre point 27 is amplified.
The inserts 22 shown from the FIGS. 4 a, b, c as well as 5 a, b can—as already mentioned—be designed as a formed sheet metal part. However, the insert 22 can also be designed as a casting, especially a precision casting. This casting can also be surface coated additionally. Obviously it is also conceivable that the exhaust swirling device 20 can be developed as a single part from a casing 21 and an insert 22 with the corresponding guide blades 23 so that the casing 21 and the insert 22 form one part or piece and are more preferably developed with uniform material.
FIGS. 6 a to e show another exhaust swirling device 20 where the casing 21 and the insert 22 are developed as a single-part. The special feature of this exhaust swirling device 20 is that the exhaust swirling device 20 entirely or partially can be formed from a casing shell 11 or the outer casing 10 of the exhaust system 100. To obtain a particularly economical and simple design a further attachment 11 a can be used in the area of the exhaust outlet 12. Here, this attachment plate 11 a can be attached to the outer casing by way of welded, riveting, screw or soldering connections. With this version it is conceivable to arrange the already described spark protection screen between the guide blades 23 and the additional attachment plate 11 a. Obviously the spark protection screen can also be arranged upstream of the guide blades 23.
FIG. 6 a shows a front view of an exhaust swirling device 20 formed from the outer casing 10. Here, the guide blades 23 of the exhaust swirling device 20 are visible through the exhaust outlet 12. These guide blades 23 are formed from the outer casing 10 through a deep drawing or other forming method. This forming step for the exhaust swirling device 20 can take place directly when forming the outer casing 10 into the casing shell 11. Consequently no additional manufacturing step is required as a result of which significant cost saving is possible. In addition, the diameter-height ratio in the exhaust swirling device 20 can also be determined through the axial depression of the guide blades 23.
FIG. 6 b represents the section I-I through the FIG. 6 a. Here it becomes clear that the casing 21 of the exhaust swirling device 20 is a one-piece development for the insert 22 of the exhaust swirling device. Both the casing 21 and the insert 22 are formed by the outer casing 10 in this case. The advantage with this version consists in that fewer components and consequently fewer sealing points are present. However it must be mentioned that the exhaust swirling device 20 from the FIGS. 6 a to e can also consist of additional sheet metal parts which, in the area of the exhaust outlet 12, are mounted to the outer casing 10.
FIG. 6 c shows a rear view of the exhaust swirling device 20 from FIGS. 6 a and b. It is clearly visible that the four guide blades 23 have been shaped segment-type from the outer casing 10. However, during this forming process a star-shaped centre point 27 has been left in place. Obviously it is also conceivable to omit this star-shaped centre point 27 during forming.
FIGS. 6 d and 6 e show a three dimensional view of the exhaust swirling device 20. Here, the triangular opening 26 after the guide blades 23 is visible in both figures. With this present version the exhaust swirling device 20, the area of all openings 26 for a part flow of the exhaust gas 31 is smaller than the cross sectional area of the exhaust outlet 12. Thus a cross sectional reduction in the exhaust swirling device results. Provided that the guide surfaces 23 are formed lower, i.e. with a greater axial depth from the outer casing 10, the total area of all openings 26 can increase.
FIGS. 7 a to d show another version of the exhaust system 100 with an exhaust swirling device 20 from FIGS. 6 a to e in various views.
FIGS. 7 a and 7 b show a three dimensional view of the outside of the exhaust system 100. It can be clearly seen that the exhaust swirling device 20 was partly formed from the outer casing 10, especially the casing shell 11. An attachment plate 11 a is additionally used in the area of the exhaust outlet 12 as a result of which the actual tubular exhaust outlet 12 is formed.
FIG. 7 c shows a section II-II through FIG. 7 b. This sectional drawing explains that the exhaust swirling device 20 was formed from the casing half 11. The additional attachment plate 11 a is also visible.
FIG. 7 d shows a schematic exploded view of the outer parts of the exhaust system 100. This view also makes it clear that the exhaust swirling device 20 with its guide blades 23 and the respective openings 26 were formed from the casing half 11. Likewise it becomes clear that a spark protection screen can be arranged between the guide blades 23 and the separate attachment plate 11 a. This spark protection screen could then also be held in place through the attachment of the attachment plate 11 a.
Finally it must be mentioned that the technical features described above can be used for the exhaust system 100 or the exhaust swirling device 20 according to the invention individually or in any combination provided they are not explicitly mutually exclusive.

LIST OF REFERENCE NUMBERS

100 Exhaust system
10 Outer casing
11 Casing shell
11 a Attachment
12 Exhaust outlet in 11
13 Catalyst chamber
14 Chamber half
15 Exhaust duct
16 Flow plate (with openings)
17 Spacer
18 Flange disc
19 Fastener
20 Exhaust swirling device
21 Casing of 20
22 Insert of 20
23 Guide blade
24 Front of 22
25 Back of 22
26 Opening for exhaust flow
27 Centre point/longitudinal axis of 20 and 22
28 Width of 23
29 Entry opening for exhaust flow
30 Opening for fastener
31 Arrow for exhaust flow

Claims

1. An exhaust system (100) for a combustion engine with an outer casing (10), directed into which is hot exhaust gas (31) through an exhaust inlet and discharged from an exhaust outlet (12) while the exhaust outlet (12) is constructed in tube form, especially with a circular or oval cross section, characterised in that in the area of the tubular exhaust outlet (12) an exhaust swirling device (20) having at least one guide blade (23) is arranged by means of which the exhaust gas (31) is deflected in the exhaust outlet (12).

2. The exhaust system according to claim 1, characterised in that the exhaust swirling device (20) is provided as an independent component in the area of the exhaust outlet (12).

3. The exhaust system according to claim 1 characterised in that the exhaust swirling device (20) is arranged in a separate casing (21) more preferably in a casing (21) with a sectional circular or oval cross section, where the casing (21) more preferably serves for the attachment of the exhaust swirling device (20) in the area of the tubular exhaust outlet (12).

4. The exhaust system according to claim 1 characterised in that the exhaust swirling device (20) is arranged in the exhaust outlet (12) such that a short pipe section, especially of the exhaust outlet (12), additionally joins the exhaust swirling device (20) before the exhaust gas (31) leaves the casing (10).

5. The exhaust system according to claim 1 in that the exhaust swirling device (20) has a sheet metal design wherein more preferably a part or the entire exhaust swirling device (20) can be formed from the outer casing (10).

6. The exhaust system according to claim 1 characterised in that the exhaust swirling device (20) has a casting more preferably a precision casting.

7. The exhaust system according to claim 1 characterised in that the entire exhaust gas (31) can be deflected by means of the guide blade(s) (23) as a result of which swirling of the entire exhaust gas (31) with the ambient air takes place.

8. The exhaust system according to claim 7, characterised in that a fixed element is provided in the central cross sectional area of the exhaust swirling device (20) to which the guide blade(s) (23) can also be attached.

9. The exhaust system according to claim 1 characterised in that only a part of the exhaust gas (31) can be deflected centrally by means of the guide blade(s) (23) while an outer part of the exhaust gas (31) can be influenced by the guide blade(s) (23) while an inner part in the central cross sectional area passes through the exhaust swirling device (20) without being influenced.

10. The exhaust system according to claim 9 characterised in that the central cross sectional area of the exhaust swirling device (20) is designed open.

11. The exhaust system according to claim 1 characterised in that a triangular opening (26) through which a part of the exhaust gas (31) is directed is provided for each guide blade (23).

12. The exhaust system according to claim 11 characterised in that the exhaust gas (31) passes the guide blade(s) (23) first in flow direction and is subsequently directed through the triangular openings (26).

13. The exhaust system according to claim 1 characterised in that a guide blade (23) has a circular segment type surface more preferably constructed flat.

14. The exhaust system according to claim 1 characterised in that a guide blade (23) is developed arch-shaped or wave-type.

15. The exhaust system according to claim 1 characterised in that the approximate width (28) of a guide blade (23) corresponds to a radius of the exhaust swirling device (20).

16. The exhaust system according to claim 1 characterised in that all guide blades (23) are constructed symmetrically identical.

17. The exhaust system according to claim 1 characterised in that the exhaust swirling device (20) discharges the exhaust gas (31) largely tangentially to the longitudinal axis (27) of the exhaust swirling device (20).

18. The exhaust system according to claim 1 characterised in that the exhaust swirling device (20) discharges the exhaust gas (31) largely radially to the longitudinal axis (27) of the exhaust swirling device (20).

19. The exhaust system according to claim 1 characterised in that the hot exhaust gas (31) is discharged from the exhaust outlet (12) following treatment of the exhaust gas (31).

20. The exhaust system according to claim 1 characterised in that at least one catalyst element for exhaust gas treatment is arranged in the exhaust system.

21. The exhaust system according to claim 20 characterised in that the catalyst element is arranged in a catalyst chamber (13) and the exhaust gases (31) are directed from the catalyst chamber (13) through an exhaust duct (15) to the exhaust swirling device (20) before the exhaust gas (31) enters the environment through the exhaust outlet (12).

22. The exhaust system according to claim 1 characterised in that at least one spark protection screen is arranged before or in the exhaust swirling device (20).

23. The exhaust system according to claim 1 characterised in that an axial depression of the guide blades (23) comprises 5 to 70% advantageously 10 to 50% and particularly advantageously 15 to 30% of the diameter of the exhaust duct (12).

24. The exhaust system according to claim 1 characterised in that the area of all openings (26) for a part flow of the exhaust gas (31) is at least as large as the cross sectional area of the exhaust outlet (1 2).

25. (canceled)