Exhaust Assembly

Abstract

A vehicle includes an engine and an exhaust gas outlet assembly with an exhaust outlet pipe surrounded by a tubular heatshield spaced from the exhaust outlet pipe. At least one divider extends between the exhaust outlet pipe and the heatshield to divide an interior volume between the exhaust outlet pipe and the heatshield into two or more sections, each section containing a column of air. The dividers are positioned so that the resonant frequencies of the columns of air do not correspond with a predetermined frequency of the engine. The predetermined frequency of the engine is generally one that arises when the vehicle is in use carrying out tasks for prolong periods of time.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the filing date of U. K. Patent Application 2500919.2, “Exhaust Assembly,” filed Jan. 22, 2025, the entire disclosure of which is incorporated herein by reference.FIELD

[0002] Embodiments of the present disclosure relate generally to an exhaust outlet assembly for a vehicle, especially an agricultural vehicle, and to a vehicle having such an exhaust outlet assembly.BACKGROUND

[0003] Agricultural vehicles such as tractors usually comprise an internal combustion engine which is used with associated components to provide propelling power to the agricultural vehicle. Exhaust gases are generated through the operation of the agricultural vehicle with the internal combustion engine. The internal combustion engine is commonly connected to an exhaust system for directing exhaust gases from the engine to atmosphere. The exhaust system includes an exhaust gas after treatment (EAT) system for reducing pollution in the exhaust gases before they are directed to the atmosphere through an exhaust outlet pipe. In agricultural tractors, it is common for the exhaust outlet pipe to be aligned generally upwardly and often generally vertically adjacent the cab so that the exhaust gasses are emitted close to the level of a roof of the cab. The exhaust outlet pipe is often surrounded by a heatshield which is spaced from the exhaust outlet pipe so that a column of air is contained in an interior volume between the exhaust outlet pipe and the heatshield. The exhaust outlet pipe and heatshield form part of an exhaust outlet assembly sometimes referred to as an exhaust stackpipe, especially when aligned generally upright. The exhaust outlet assembly may serve a variety of purposes, such as controlling noise, directing exhaust fumes away from an operator or other occupant in the cab and improving the performance of the engine.

[0004] Vibrations of the engine may be induced in the exhaust outlet assembly which may further be transmitted to the cab causing discomfort to an operator present in the cab.

[0005] The column of air between the exhaust outlet pipe and the heatshield has a resonant frequency which is dependent on its length. If the resonant frequency of the column of air happens to correspond with a frequency of the engine while the tractor is in use, this may also produce vibrations that are transmitted to the cab and / or sound. This is a particular issue if the resonant frequency is one produced by the engine while the tractor is performing a task in a field that takes a long time, as the resulting resonance can be particularly unpleasant for the operator over a prolonged period. Such a frequency of the engine may be referred to as a “working frequency.”BRIEF SUMMARY

[0006] In a first embodiment, a vehicle has an internal combustion engine and an exhaust system for receiving exhaust gases from the engine, the exhaust system having an exhaust outlet assembly comprising an exhaust outlet pipe surrounded by a tubular heatshield spaced from the exhaust outlet pipe so that air is present in an interior volume between the exhaust outlet pipe and the heatshield, the exhaust assembly having a first length over which the heatshield overlaps the exhaust outlet pipe, wherein at least one divider extends between the exhaust outlet pipe and the heatshield to divide the interior volume between the exhaust outlet pipe and the heatshield into two or more longitudinal sections, each section containing a column of air having a length less than the first length of the exhaust outlet assembly.

[0007] In the exhaust outlet assembly, the air contained between the exhaust outlet pipe and the heatshield is divided into two or more columns, each having a length less that the first length of the exhaust outlet assembly. Accordingly, each column of air has a resonant frequency different from the resonant frequency of a column extending over the first length of the undivided exhaust outlet assembly. By appropriate positioning of the at least one divider, it can be arranged that none of the columns of air in the exhaust outlet assembly has a resonant frequency that coincides with a predetermined frequency of the engine. The predetermined frequency is typically selected as a working frequency of the engine. This reduces the risk of vibrations / sound being generated due to resonance between the engine and the air in the exhaust outlet assembly that adversely affect an operator without having to change the overall length of the exhaust outlet assembly.

[0008] The at least one divider may extend in a plane generally orthogonal to a longitudinal axis of the exhaust outlet pipe. It should be noted that the exhaust outlet assembly may not be straight but may be curved or cranked to a limited amount between its ends. Accordingly, reference to the at least one divider extending in a plane generally orthogonal to a longitudinal axis of the exhaust outlet pipe should be understood as referring to the longitudinal axis at the location of the at least one divider.

[0009] The at least one divider may be compressed between the exhaust outlet pipe and the heatshield.

[0010] The at least one divider may take the form of a solid closure plate, i.e., a plate with no openings or apertures. In this case, the exhaust outlet assembly may be configured so that substantially no air can pass from one section to another past the at least one divider. It will be appreciated though that the divider may not be 100% leakproof. However, in other embodiments the divider may not fully close the cross-sectional area between the exhaust outlet pipe and the heatshield provided it sufficiently disrupts the passage of air to alter the resonant frequency of the air columns. The at least one divider may close off at least 60%, or at least 80%, or at least 90%, or at least 95% of the cross-sectional area between the exhaust outlet pipe and the heatshield. The at least one divider may take the form of a perforated baffle.

[0011] The location of the at least one divider may be configured such that none of the columns of air has a resonant frequency that corresponds to a predetermined frequency Fe1 of the engine. The location of the at least one divider may be configured such that the ratio of the resonant frequency of the column of air in each section of the exhaust outlet assembly and the predetermined frequency of the engine is greater than √2±15%. The predetermined frequency may be a working frequency Few of the engine. In embodiments, the location of the at least one divider may be configured such that none of the sections of the exhaust outlet assembly contain a column of air having a resonant frequency that corresponds to a frequency of the engine when the engine is operating at one or more of a maximum torque, a maximum power, and a maximum engine speed. In embodiments, the location of the at least one divider may be configured such that none of the sections of the exhaust outlet assembly contain a column of air having a resonant frequency that corresponds to a frequency of the engine when the engine is operating at a stable speed in the range of 1800 to 2500 RPM or more particularly a stable speed in the range of 1900 to 2100 RPM.

[0012] The predetermined frequency Fe1 of the engine may be a frequency that corresponds to a dominant resonant frequency of the cab ±15%.

[0013] The exhaust outlet assembly may have two or more dividers spaced apart longitudinally of the exhaust outlet assembly at locations between the longitudinal ends of the exhaust outlet assembly.

[0014] Brackets for supporting the heatshield on the exhaust outlet pipe may be attached between the exhaust outlet pipe and the heatshield and the at least one divider may be located on a respective bracket. The exhaust outlet assembly may extend generally upwardly and the at least one divider may be located above and supported from below by a respective one of the brackets.

[0015] The exhaust system may comprise an EAT system and the exhaust outlet assembly may form part of an outlet from the EAT.

[0016] The exhaust outlet assembly may be aligned generally upwardly and may form an exhaust stackpipe.

[0017] A closure may be provided between the exhaust outlet pipe and the heatshield at an inlet end of the exhaust outlet assembly. If the exhaust outlet assembly is aligned generally upwardly, the closure may be provided between the exhaust outlet pipe and the heatshield at a lower end of the heatshield.

[0018] Within the scope of this application, it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0020] FIG. 1 is a schematic drawing of an example agricultural vehicle known in the prior art;

[0021] FIG. 2 is a schematic drawing of an exhaust outlet assembly adjacent a cab of an agricultural vehicle;

[0022] FIG. 3 illustrates an exhaust outlet assembly for the vehicle of FIG. 2 according to the disclosure;

[0023] FIG. 4 is a view similar to that of FIG. 3 but in which a heatshield of the exhaust outlet assembly is partially cut away so that internal details of the exhaust gas outlet assembly can be seen;

[0024] FIG. 5 is an enlarged view of part of the exhaust outlet assembly of FIG. 4; and

[0025] FIG. 6 is a perspective view of a divider from part of the exhaust outlet assembly of FIGS. 3 to 5.DETAILED DESCRIPTION

[0026] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0027] The following description provides specific details of embodiments of the present disclosure in order to provide a thorough description thereof. However, a person of ordinary skill in the art will understand that the embodiments of the disclosure may be practiced without employing many such specific details. Indeed, the embodiments of the disclosure may be practiced in conjunction with conventional techniques employed in the industry. In addition, the description provided below does not include all elements to form a complete structure or assembly. Only those process acts and structures necessary to understand the embodiments of the disclosure are described in detail below. Additional conventional acts and structures may be used.

[0028] As used herein, the terms “comprising,”“including,”“containing,”“characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps, but also include the more restrictive terms “consisting of” and “consisting essentially of” and grammatical equivalents thereof.

[0029] As used herein, the term “may” with respect to a material, structure, feature, or method act indicates that such is contemplated for use in implementation of an embodiment of the disclosure, and such term is used in preference to the more restrictive term “is” so as to avoid any implication that other, compatible materials, structures, features, and methods usable in combination therewith should or must be excluded.

[0030] As used herein, the term “configured” refers to a size, shape, material composition, and arrangement of one or more of at least one structure and at least one apparatus facilitating operation of one or more of the structure and the apparatus in a predetermined way.

[0031] As used herein, the singular forms following “a,”“an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0032] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0033] As used herein, spatially relative terms, such as “beneath,”“below,”“lower,”“bottom,”“above,”“upper,”“top,”“front,”“rear,”“left,”“right,” and the like, may be used for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figures.

[0034] As used herein, the term “substantially” in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0% met, at least 95.0% met, at least 99.0% met, or even at least 99.9% met.

[0035] As used herein, the term “about” used in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter).

[0036] FIG. 1 illustrates an example agricultural vehicle in the form of a tractor 100 which is known in the prior art. The tractor 100 comprises a chassis 101 on which are mounted front wheels 102 and rear wheels 103. An engine enclosure 104 towards the front of the tractor 100 encloses an internal combustion engine and associated components for providing propelling the vehicle. An operator cab 105 is located towards a rear of the tractor 100 behind the engine enclosure 104. The internal combustion engine is connected to an exhaust system for directing exhaust gases from the engine to atmosphere. The exhaust system 106 includes an exhaust gas after treatment (EAT) system 107 for reducing pollution in the exhaust gases. Exhaust gases exiting the EAT are directed to atmosphere though an exhaust outlet pipe 108. The exhaust outlet pipe 108 is aligned vertically adjacent the cab 105 so that the exhaust gasses are emitted close to the level of a roof of the cab 105. The exhaust outlet pipe 108 is surrounded by a heatshield 109 which is spaced from the exhaust outlet pipe 108 so that a column of air is contained in an interior volume between the exhaust outlet pipe 108 and the heatshield 109. The exhaust outlet pipe 108 and heatshield 109 form part of an exhaust outlet assembly 110 also referred to as an exhaust stackpipe.

[0037] Since the engine is mechanically connected to the exhaust outlet assembly 110, the engine may induce vibrations in the exhaust outlet assembly 110. With the exhaust outlet assembly 110 being mounted adjacent the cab 105 of the tractor 100, vibrations from the exhaust outlet assembly 110 may be transmitted to the cab 105, causing discomfort to an operator present in the cab 105.

[0038] FIG. 2 illustrates an example vehicle in the form of an agricultural tractor 200, similar to the tractor 100 of FIG. 1. The vehicle has an internal combustion engine 211 for providing motive force and an exhaust system 206 for receiving exhaust gases from the engine 211 and delivering them to atmosphere. The exhaust system 206 includes an exhaust gas after treatment (EAT) system 207 for removing particulates and other pollutants from the exhaust gases. Treated exhaust gases are directed from an outlet 212 of the EAT 207 to an exhaust outlet pipe 208 that extends upwardly (and in this case generally vertically) to a final exhaust gas outlet 213 where the treated exhaust gases are emitted to atmosphere. A heatshield 209 locates about the exhaust outlet pipe 208. The heatshield 209 is generally tubular to enclose at least part of the length the exhaust outlet pipe 208. Though tubular, the heatshield need not be cylindrical in shape. The heatshield 209 may be formed from sheet metal or any other suitable material capable of withstanding extended periods at temperatures in excess of 100° C. The heatshield 209 acts to partially insulate the exhaust outlet pipe 208, operating at higher temperatures. It protects against people contacting the hot exhaust outlet pipe 208 and also prevents field debris, such as straw or other crop residue, from contacting the exhaust outlet pipe 208, which might otherwise cause a fire risk. A plurality of brackets or connectors 214 may extend between the heatshield 209 and an external surface of the exhaust outlet pipe 208 and connect the heatshield 209 to the exhaust outlet pipe 208.

[0039] The exhaust outlet pipe 208 and the heatshield 209 form part of an exhaust outlet assembly 210 containing a column of air 215 in an interior volume 216 between the exhaust outlet pipe 208 and the heatshield 209. The length of the column of air 215 is determined by the length X over which the heatshield 209 overlaps the exhaust outlet pipe 208. This overlapping length X will be referred to as a “first length.” In different applications, the heatshield 209 may extend over substantially the whole of the length of the exhaust outlet pipe 208 but in others may extend only over part of its length. The exhaust outlet pipe 208 and the heatshield 209 may each be constructed from a number of component parts assembled together.

[0040] The exhaust outlet assembly 210 may extend upwardly and may be mounted adjacent to a cab 205 of the agricultural vehicle, for example as shown in FIG. 1. Other mounting positions of the exhaust outlet assembly 210 relative to other components of the vehicle are also possible. Similarly, in the example of FIG. 2, the exhaust outlet assembly 210 is mounted with a longitudinal axis 217 of the exhaust outlet pipe 208 oriented upwardly relative to an upright orientation of the vehicle. Other orientations are also possible. It should be noted that though the exhaust outlet assembly 210 may extend generally vertically in an upward direction, it need not be straight. It may curve or be kinked along its length and / or it may be inclined relative to the vertical. However, the person skilled in the art will understand that the exhaust outlet assembly 210 has a longitudinal axis 217.

[0041] The exhaust outlet assembly 210 is generally only connected to the remainder of the exhaust system 206 at a single point around the outlet 212 of the EAT system 207 which is located at an inlet to the exhaust outlet pipe 209. During operation of the vehicle, multiple modes of vibration may be set up along the exhaust outlet assembly 210 by the engine and by movement of the vehicle. This may result in resonant frequencies being excited within the heatshield 209.

[0042] In addition to vibrations transmitted mechanically to the exhaust outlet assembly 210, vibrations or sound 218 may arise due to resonance between the column of air 215 in the exhaust outlet assembly 210 and the engine. The column of air 215 has a resonant frequency F0 that is dependent on its length, among other things. If this happens to coincide with a frequency of the engine when operating at a stable speed, the resulting resonance can produce vibrations in the heatshield and / or noise that can adversely affect an operator 219 in the cab 205. This is a particular issue if the resonant frequency F0 of the column of air 215 happens to coincide with a frequency Fe of the engine when the vehicle is being operated to perform a lengthy task, such as field work. Tractors 200 are often required to carry out tasks in a field that require the tractor to be driven at a largely uniform speed and with the engine operating at a fairly constant, stable, speed (RPM) for prolonged periods. For example, during tillage, planting, or spraying operations. If the resonant frequency F0 of the column of air 215 happens to coincide with the frequency Fe of the engine when performing such tasks, this can result in considerable discomfort for the operator 219. Such an engine frequency Fe will be referred to as a “working frequency” of the engine Few.

[0043] The frequency Fe of an engine can be calculated by the following equation:Fe=(engine RPM×engine order) / 60  (Equation 1)

[0044] where “engine order” is related to the firing order and where a first order corresponds to half the number of cylinders.

[0045] A tractor engine is often operated at speeds corresponding to maximum torque, maximum power, and / or maximum engine speed for prolonged periods, such as when undertaking field work. Accordingly, when the resonant frequency F0 of the air column in the exhaust outlet assembly corresponds to an engine frequency at one or more of these three working points of the engine, this can create unwanted vibration and / or sound leading to operator fatigue. The problem is increased when this frequency is close to the dominant resonant frequency of the cab.

[0046] In an example, a tractor cab may have a dominant resonant frequency of 100 Hz + / −15 Hz. A situation in which the resonant frequency F0 of the air column in the exhaust outlet assembly 210 and a frequency of the engine Fe operating at a stable speed falls within this range should be avoided.

[0047] In an example, the frequence Fe of a six-cylinder engine working at a stable speed of 1950 RPM (which in this example corresponds to a speed at which the engine is operating at maximum power) is given by equation 1:Fe=(1950×3) / 60=97.5 Hz.

[0048] This falls within the range of the dominant resonant frequency of the cab of 100 Hz + / −15 Hz. Accordingly, it is highly preferable that the resonant frequency F0 of the air column in the exhaust outlet assembly 210 does not correspond to this frequency if operator fatigue is to be avoided. This is an example of a working frequency Few of the engine. Other working frequencies Few of the engine may also be problematical and in one example, frequences when the engine is operating at a stable speed in the range of 1800 to 2500 RPM, or more particularly in the range of 1900-2100 RPM, are working frequencies Few of the engine that are particularly problematical. However, depending on engine size and other factors, problematic working frequencies Few can be generated at other engine speeds, particularly when the engine is working at maximum torque, maximum power or maximum speed.

[0049] One way to address this issue would be to design the exhaust outlet assembly 210 so that the column of air 215 does not have a resonate frequency that coincides with potentially problematic working frequencies Few of the engine. However, since the resonant frequency F0 of the column of air 215 is dependent on its length, this may require adjusting the first length X of the exhaust outlet assembly. This may not be desirable to meet other design and operational constraints of the system. The present disclosure seeks to avoid this issue by using at least one divider to divide the interior volume 216 longitudinally into two or more sections, each containing a column of air, and positioning the at least one divider so that none of the columns have a resonant frequency F0 that corresponds to a predetermined frequency Fe1 of the engine. In otherwards, the resonant frequencies F0 of the columns of air are tuned as far away as possible from at least one preselected or predetermined frequency Fe1 of the engine. Usually, the predetermined engine frequency Fe1 will be a working frequency of the engine Few such as those produced when carrying out field operations. In an embodiment, the at least one divider is positioned so that the ratio of the resonant frequency F0 of any given column of air in the exhaust outlet assembly 210 to the predetermined frequency Fe1 of the engine is greater than √2. Though this provides an ideal separation between the resonant frequency FO of the columns of air and the predetermined frequency Fe1 of the engine in practice, less of a gap may be acceptable to reduce operator fatigue but at an acceptable cost. In an embodiment, a tolerance in the region of ±15% may be applied. The predetermined engine frequency Fe1 may be selected as being one which is close to a dominant resonant frequency of the cab, such as within a tolerance of ±15% of the dominant resonant frequency.

[0050] An embodiment of an exhaust outlet assembly 210 according to the present disclosure is shown in FIGS. 3 to 6. The exhaust outlet assembly 210 may be used in a vehicle 100, 200 such as those shown in FIG. 1 or FIG. 2 as discussed above. The vehicle 200 may be an agricultural tractor having a cab 205. The vehicle has an exhaust system 206 which receives exhaust gases from an internal combustion engine. The exhaust system 206 includes an EAT system 207 and an exhaust outlet assembly 210 according to the disclosure which receives exhaust gas from the EAT system.

[0051] The exhaust outlet assembly 210 is illustrated in isolation in FIGS. 3 and 4 and comprises an exhaust gas outlet pipe 208 enclosed within a heatshield 209. In FIG. 4, the heatshield 209 is shown partly cut away so that internal details of the exhaust gas outlet assembly 210 can be seen.

[0052] The heatshield 209 is supported on the exhaust outlet pipe 208 by a number of brackets 214 attached to an outer surface of the exhaust outlet pipe 208. Air 215 is contained within the interior volume 216 between the exhaust outlet pipe 208 and the heatshield.

[0053] In accordance with the present disclosure, at least one divider 220 (220a, 220b) is located between the exhaust outlet pipe 208 and the heatshield 209 to divide the interior volume 216 into a number of longitudinal sections 216a, 216b, 216c, each containing a respective column of air 215a, 215b, 215c. Each divider 220 is a plate-like member that extends transversely to the longitudinal axis 217 of the exhaust outlet pipe 208 to form a closure or cap extending transversely across the gap between the exhaust outlet pipe 208 and the heatshield 209. As illustrated in FIG. 6, each divider 220 may have a central aperture 221 for locating about the exhaust outlet pipe and outer edge profile 222 that is shaped to conform to the inner surface of the heatshield 209. In an embodiment, the divider 220 is made of a solid but pliant material and a slit 223 extends from one edge to the central aperture 221 to enable the divider 220 to be positioned about the exhaust outlet pipe. A divider 220 can be made of any suitable material capable of withstanding the high temperatures within the exhaust outlet assembly 210 for extended periods. A divider 220 could be made from an insulation type material commonly used for exhaust systems, for example. However, a divider 220 can be made from other materials and other methods of assembly used.

[0054] In the present embodiment there are two dividers 220a, 220b spaced apart in a longitudinal direction of the exhaust outlet assembly between the longitudinal ends of the assembly. This divides the interior volume into three sections 216a, 216b, 216c, including a relatively long primary middle section 216b having a length Y between the two dividers 220a, 220b. The length Y between the two dividers 220a, 220b determines the length of the column of air 215b in the middle section 216b and hence the resonant frequency F0 of the column of air 215b. The positioning of the dividers 220a, 220b is calculated so that the resonant frequency F0 of the column of air 215b in the middle section 216b does not correspond with a predetermined frequency Fe1 of the engine. The predetermined frequency Fe1 may be selected as one of the working frequencies Few of the engine. In an embodiment, the predetermined frequency Fe1 is selected as being at least one of the engine frequencies when the engine 211 is operating at a stable speed which corresponds to the maximum engine toque, maximum engine power and / or maximum engine speed. In an example, the predetermined frequency Fe1 is selected as being at least one of the engine frequencies when the engine 211 is operating at a stable speed in the range of 1800 to 2500 RPM, or more particularly 1900 to 2100 RPM. In another example, the predetermined frequency Fe1 is selected as being the dominant resonant frequency of the cab 205±15%. In an embodiment, the dividers 220a, 220b are positioned such that the ratio of the resonant frequency F0 of the column of Air 215b to the predetermined engine frequency Fe1 is greater than √2 within a tolerance of ±15%.

[0055] The dividers 220a, 220b may be compressed between the exhaust outlet pipe 208 and the heatshield 209. As illustrated, a divider 220a, 220b may be located above and rest on one of the brackets 214 mounting the heatshield 209 to the exhaust outlet pipe 208. This can help to support a divider 220a, 220b so that it does not become dislodged over time. However, other arrangements for mounting a divider 221a, 221b can be adopted.

[0056] Columns of air 215a, 215c are also contained the sections 216a, 216c at either end of the exhaust outlet assembly 210 outside the two dividers 220a, 220b. However, these are relatively short so that their resonant frequencies F0 should not correspond with a working frequency Few of the engine, but this can be confirmed at the design stage.

[0057] In other embodiments, there may be only one divider 220. In some embodiments the gap between the exhaust outlet pipe 208 and the heatshield 209 is closed at the lower, inlet end of the exhaust outlet assembly 210. This is sometimes the case to prevent debris from entering the volume 216 between the exhaust outlet pipe 208 and the heatshield 209. In this case, only a single divider may be necessary. In other embodiments there may be more than two dividers 220.

[0058] A divider 220 may be arranged so that air is not able to pass from one section to another past the divider such that the air columns in the adjacent sections are entirely separated from one another. However, many of the advantages of the present disclosure may be obtained where some fluid connection between the sections past a divider 220 is possible, provided that the resonance of the air contained in the exhaust air outlet assembly210 is tuned so that it is out of phase with the particularly problematic working engine frequencies Few. A divider 220 may not be a perfect seal between the exhaust outlet pipe 208 and the heatshield 209 and may even take the form of a perforated baffle. In this case, it is expected that the at least one divider 220 may close off at least 60%, or at least 80%, or at least 90%, or at least 95% of the cross-sectional area between the exhaust outlet pipe 208 and the heatshield 209.

[0059] Though the disclosure has been described in relation to an agricultural tractor 200, it can be applied to any other type of vehicle including other agricultural vehicles, other utility vehicles such as are used in the construction industry and road trucks. Furthermore, the exhaust outlet assembly 210 need not be aligned upwardly but could be aligned at an angle to the vertical and could be aligned generally horizontally.

Claims

1. A vehicle comprising:an internal combustion engine; andan exhaust system for receiving exhaust gases from the engine, the exhaust system having an exhaust outlet assembly comprising an exhaust outlet pipe surrounded by a heatshield spaced from the exhaust outlet pipe so that air is present in an interior volume between the exhaust outlet pipe and the heatshield, the exhaust assembly having a first length over which the heatshield overlaps the exhaust outlet pipe, wherein at least one divider extends between the exhaust outlet pipe and the heatshield to divide the interior volume between the exhaust outlet pipe and the heatshield into two or more longitudinal sections, each section containing a column of air having a length less than the first length of the exhaust outlet assembly;wherein the at least one divider is located such that none of the columns of air has a resonant frequency that corresponds to a predetermined frequency Fe1 of the engine, and wherein a ratio of the resonant frequency F0 of the column of air in each section of the exhaust outlet assembly to the predetermined frequency Fe1 of the engine is greater than 0.85*√2 .

2. The vehicle of claim 1, wherein the least one divider extends in a plane generally orthogonal to a longitudinal axis of the exhaust outlet pipe.

3. The vehicle of claim 1, wherein the at least one divider is compressed between the exhaust outlet pipe and the heatshield.

4. The vehicle of claim 1, wherein the exhaust outlet assembly is configured so that substantially no air can pass from one section to another past the at least one divider.

5. The vehicle of claim 1, wherein the at least one divider is in the form of a solid closure plate.

6. The vehicle of claim 1, wherein the exhaust outlet assembly is configured such that the at least one divider closes off at least 60% of a cross-sectional area between the exhaust outlet pipe and the heatshield.

7. The vehicle of claim 6, wherein the exhaust outlet assembly is configured such that the at least one divider closes off at least 80% of the cross-sectional area between the exhaust outlet pipe and the heatshield.

8. The vehicle of claim 7, wherein the exhaust outlet assembly is configured such that the at least one divider closes off at least 90% of a cross-sectional area between the exhaust outlet pipe and the heatshield.

9. The vehicle of claim 1, wherein the at least one divider is located such that the ratio of the resonant frequency F0 of the column of air in each section of the exhaust outlet assembly to the predetermined frequency Fe1 of the engine is greater than √2.

10. The vehicle of claim 1, wherein the at least one divider is located such that the ratio of the resonant frequency F0 of the column of air in each section of the exhaust outlet assembly to the predetermined frequency Fe1 of the engine is between 0.85 *√2 and 1.15*√2 .

11. The vehicle of claim 1, wherein the predetermined frequency Fe1 of the engine is a working frequency Few of the engine.

12. The vehicle of claim 1, wherein the at least one divider is located such that none of the sections of the exhaust outlet assembly contain a column of air having a resonant frequency F0 that corresponds to a frequency of the engine Fe when the engine is operating at a speed corresponding to one of a maximum torque, maximum power, or maximum speed of the engine.

13. The vehicle of claim 1, wherein the at least one divider is located such that none of the sections of the exhaust outlet assembly contain a column of air having a resonant frequency F0 that corresponds to a frequency of the engine Fe when the engine is operating at a speed in the range of 1800 to 2500 RPM.

14. The vehicle of claim 13, wherein the at least one divider is located such that none of the sections of the exhaust outlet assembly contain a column of air having a resonant frequency F0 that corresponds to a frequency of the engine Fe when the engine is operating at a speed in the range of 1900 to 2100 RPM.

15. The vehicle of claim 1, wherein the at least one divider comprises at least two dividers spaced apart longitudinally of the exhaust outlet assembly at locations between the longitudinal ends of the exhaust outlet assembly.

16. The vehicle of claim 1, wherein brackets for supporting the heatshield on the exhaust outlet pipe are attached between the exhaust outlet pipe and the heatshield and the at least one divider is located on a respective bracket.

17. The vehicle of claim 1, wherein the exhaust system comprises an EAT system and the exhaust outlet assembly is part of an outlet from the EAT system.

18. The vehicle of claim 1, wherein the exhaust outlet assembly is aligned generally upwardly.

19. The vehicle of claim 1, wherein the exhaust outlet assembly forms an exhaust stackpipe.

20. The vehicle of claim 1, further comprising a closure between the exhaust outlet pipe and the heatshield at an inlet end of the exhaust outlet assembly.

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