GB2512327A

GB2512327A - Exhaust system

Info

Publication number: GB2512327A
Application number: GB1305491.1A
Authority: GB
Inventors: Peter Hawkins; Joseph JOYCE
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2013-03-26
Filing date: 2013-03-26
Publication date: 2014-10-01
Also published as: GB201305491D0

Abstract

An exhaust system 37 for a compressor comprises an inlet for coupling to an exhaust port of the compressor, and preferably an exhaust muffler 41 for venting to atmosphere. An expansion volume 39, disposed between the inlet and the exhaust muffler, is provided for accommodating the expansion of gas exhausted from the compressor to suppress acoustic noise. The expansion volume may be a chamber which provides a stepped increase in cross-sectional area of the fluid flow path. A stepped decrease in cross-sectional area may be provided downstream of the increase in cross-sectional area. The muffler may comprise a sintered filter. The compressor may be part of a vehicle air suspension system.

Description

EXHAUST SYSTEM

TECHNICAL FIELD

The present invention relates to an exhaust system and particularly, but not exclusively, to an exhaust system for a compressor. Aspects of the invention relate to an exhaust system, to a compressor, to a vehicle suspension system, to an expansion silencer, and to a vehicle.

BACKGROUND OF THE INVENTION

It is known to provide a vehicle with a suspension system to couple the wheels of the vehicle to the vehicle body or chassis. In some vehicle applications, it is desirable to provide suspension systems which can adjust the ride height of the vehicle (i.e. the distance between the vehicle body and the ground). This has particular advantages in vehicles intended for use off-road which typically have increased ride heights in order to improve ground clearance. In order to facilitate entry to and exit from the vehicle, the suspension system may lower the vehicle body with respect to the ground level. It may be desirable or necessary to raise the vehicle body prior to moving off. Moreover, it may be appropriate to vary the vehicle ride height when the vehicle is moving, for example in response to vehicle operating parameters (such as terrain) or dynamic parameters (such as vehicle speed).

In other vehicle applications, it is desirable to provide suspension systems which can be employed for levelling the vehicle in the event of a mass change (for example, users getting into or out of the vehicle, luggage being removed or added).

Vehicle suspension systems comprising pneumatic springs or air springs are known. The pneumatic springs employ a bellows or bladder which is inflated and deflated to raise and lower the height of the vehicle or level the vehicle. A compressor can be provided to supply pressurised air to a reservoir which is coupled to the pneumatic springs by a series of air-lines forming an air gallery. One or more valve blocks control the supply of air to each pneumatic spring from the reservoir.

An air dryer, for example comprising a silicate gel, for removing moisture from the compressed air is attached to the reservoir. Air supplied to inflate the pneumatic springs passes through the air dryer. Conversely, when the pneumatic springs are deflated, the compressed air is exhausted from the suspension air gallery to atmosphere through the air dryer, removing the moisture from the dryer unit. An exhaust port forms the outlet of the air dryer unit. The exhaust port comprises a solenoid actuated exhaust valve which is opened when the pneumatic springs are to be deflated.

A problem can arise concerning the suppression of noise generated by the air suspension system, particularly when air is initially exhausted to atmosphere. If the pneumatic pressure in the suspension air gallery is very high, for example following charging of the reservoir, a loud "boom" noise can be heard from the exhaust port when it initially opens due to the large pressure differential. This is particularly prominent when the compressor is fitted inside the vehicle, and sealed in an acoustic box, as the rapid pressure pulse can cause the acoustic box to "pant", amplifying the noise.

One approach to overcoming this problem is to fit a silencer to the exhaust port. By way of example, a conventional exhaust system 100 is shown schematically in Figure 1 with the exhaust air flow direction indicated by an arrow A. A sintered exhaust muffler 101 is mounted to an exhaust valve 103 for controlling exhaust gases from a suspension air gallery 105 (comprising the pressure lines and the air springs). The exhaust muffler 101 can help reduce the exhaust noise during long, relatively low pressure venting operations, such as lowering the vehicle. A potential shortcoming of this arrangement is that the exhaust muffler 101 can restrict the exhaust flow, causing the initial pressure pulse to occur over a longer time period.

The restriction of the exhaust flow can adversely affect vehicle performance, for example resulting in an increased time to lower the suspension to access height. Furthermore, the reduced flow rate through the dryer unit during exhausting may mean that the air dryer is not regenerated (a high flow rate of air is required to regenerate the dryer effectively).

The present invention has been developed against this background. At least in certain embodiments, the present invention sets out to overcome or ameliorate at least some of the problems associated with known systems.

SUMMARY OF THE INVENTION

Aspects of the present invention for which protection is sought relate to an exhaust system for a compressor; a compressor; a vehicle suspension system; an expansion silencer; and a vehicle.

According to a further aspect of the present invention there is provided an exhaust system for a compressor, the exhaust system comprising: an inlet for coupling to an exhaust port of a compressor; an exhaust muffler for venting to atmosphere; and an expansion volume, disposed between the inlet and the exhaust muffler, for accommodating the expansion of gas exhausted from the compressor to suppress acoustic noise.

The compressor is typically arranged to compress air, for example to supply pressurised air to one or more air springs in a vehicle suspension system. When the exhaust port is opened, exhaust gas from the compressor is introduced, under pressure, through the inlet and into the expansion volume. The expansion volume may be arranged to allow compressed fluid entering the exhaust system to expand before venting through the exhaust muffler. An initial high pressure pulse (or spike) created when the exhaust port is opened can be partially or completely dissipated within the expansion volume. Thus, the expansion volume can help to reduce the generation of audible noise when the compressed air is exhausted from the compressor. Moreover, at least in certain embodiments of the present invention, the exhaust system does not inhibit or restrict the exhaust flow from the compressor. The exhaust muffler may form an outlet for the exhaust system.

The inlet, the expansion volume and the exhaust muffler may be arranged in series. A continuous fluid flow path may be formed through the exhaust system. The expansion volume can be defined by an expansion silencer. The expansion volume can be profiled to form an increase in the cross-sectional area of said fluid flow path. The increase in the cross-sectional area can be disposed proximate an inlet to said expansion volume. A sidewall of the expansion volume can be tapered outwardly, for example to form a continuous increase in the cross-sectional area. Alternatively, the expansion volume can be profiled to form a stepped (or discontinuous) increase in the cross-sectional area of said fluid flow path. A sidewall of the expansion volume could extend substantially radially outwardly relative to a longitudinal axis of the fluid pathway.

The expansion volume can be profiled to form a decrease in the cross-sectional area of said fluid flow path. The decrease in the cross-sectional area can be disposed proximal an outlet of said expansion volume. Thus, the increase in the cross-sectional area can be arranged upstream of the decrease in the cross-sectional area. The expansion volume can be tapered inwardly to form a continuous decrease in the cross-sectional area; or a stepped (i.e. discontinuous) decrease in the cross-sectional area.

The expansion volume can comprise a chamber having an inlet aperture and an outlet aperture. The expansion volume can be formed by a sealed container comprising said inlet aperture and an outlet aperture for coupling to said exhaust muffler. The container can comprise a sidewall having a larger diameter than the exhaust port of the compressor or of a pressure line connecting the exhaust port to the exhaust system. The sidewall can, for example, be cylindrical. The sidewall can be L-shaped in transverse section.

The expansion volume can comprise an elongate conduit disposed between said outlet port and the exhaust muffler. The elongate conduit is configured to define sufficient internal volume to dissipate the initial pressure pulse resulting from opening of the exhaust port.

At least in certain embodiments, the exhaust muffler and/or the expansion volume can be configured to permit substantially unrestricted fluid flow.

The exhaust muffler can help to suppress the flow noise of the exhausted air after the initial opening of the valve. The exhaust muffler can comprise a plurality of apertures through which the gas can vent. For example, the exhaust muffler could comprise a grille, grating, mesh or filter. The exhaust muffler can comprise a porous material. For example, the exhaust muffler can comprise a sintered material. The sintered material can, for example, comprise sintered metal and/or ceramic. The sintered material can form a sintered filter. The porosity of the filter can be selected to provide the desired flow properties through the exhaust muffler, for example to allow the air to vent from the expansion chamber at a suitable rate to prevent or reduce the generation of audible sound.

According to a further aspect of the present invention there is provided a fluid compressor in combination with an exhaust system of the type described herein.

According to a still further aspect of the present invention there is provided a vehicle suspension system comprising a compressor and an exhaust system as described herein, the inlet of the exhaust system being mounted to an exhaust port of said compressor.

According to a yet further aspect of the present invention there is provided a vehicle comprising an exhaust system as described herein.

According to a yet further aspect of the present invention there is provided an expansion silencer comprising: an inlet for coupling to an exhaust port of a compressor; an expansion chamber for accommodating the expansion of gas exhausted from the compressor to suppress acoustic noise; and an outlet for venting gas from the expansion chamber. A porous member can be provided at said outlet. For example, a sintered member can be disposed at said outlet. The inlet and the outlet can be offset from each other.

According to a still further aspect of the present invention there is provided an exhaust apparatus comprising: an inlet; an expansion chamber; and a sidewall formed from a porous sintered material to form an outlet; wherein the sidewall is profiled to form said expansion chamber. The sintered material has a porous structure to allow air to vent from the expansion chamber. The expansion chamber is formed within the exhaust apparatus by said sidewall. The sintered material can comprise metal and/or ceramic. The expansion chamber can have an enlarged transverse section ielative to the transveise section of the inlet. The sidewall can, for example, have a part-cylindrical or part-spherical profile.

The term silencer" is used herein to describe apparatus adapted to suppress audible noise and is to be understood as having the same meaning as the term muffler'.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which: Figure 1 shows a schematic representation of a conventional exhaust muffler for a compressor; Figure 2 shows a schematic representation of a vehicle having a compressor exhaust system in accordance with a first embodiment of the present invention; Figure 3 shows a perspective view of a compressor an exhaust system in accordance with the first embodiment of the present invention; Figure 4 shows a schematic representation of the exhaust system in accordance with the first embodiment of the present invention; Figure 5A shows a perspective view of the expansion silencer and the exhaust muffler in accordance with the present invention; and Figure 5B shows a partial sectional view of the expansion silencer in accordance with the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

Detailed descriptions of specific embodiments of the exhaust system, vehicle suspension system and method of the present invention are disclosed herein. It will be understood that the disclosed embodiments are merely examples of the way in which certain aspects of the invention can be implemented and do not represent an exhaustive list of all of the ways the invention may be embodied. Indeed, it will be understood that the exhaust system, vehicle suspension system and method described herein may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimised to show details of particular components. Well-known components, materials or methods are not necessarily described in great detail in order to avoid obscuring the present disclosure. Any specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the invention.

With reference to Figure 2, there is shown a vehicle 1 comprising a vehicle body 3 mounted on four wheels 5a-d. The vehicle 1 comprises a front pair of wheels Sa, Sb and a rear pair of wheels Sc, Sd. The front pair of wheels 5a, Sb and/or the rear pair of wheels Sc, Sd is/are drivingly coupled to a drive system (not shown), for example a combustion engine and/or electric motor. The wheels 5a-d are coupled to the vehicle body 3 by respective suspension means in the form of air springs 7a-d. The air springs 7a-d form part of a vehicle suspension system 9 which is described in more detail herein.

The suspension system 9 includes a fluid compression means in the form of a compressor 11. The compressor 11 selectively supplies pressurised air to the air springs 7a-d of each wheel 5a-d by connection means in the form of pressure lines L16. The pressure lines L16 provide conduits for transferring pressurised air, typically at high pressure (optionally between 700 kPa to 3000 kPa (7 to 30 Bar), alternatively between 700 kPa to 1000 kPa (7 to Bar) and in other embodiments between 900 kPa to 1400 kPa (9 to 14 bar)). In other embodiments other pressure ranges are useful. The pressure lines L16 can be constructed from nylon or other material capable of withstanding the pressures generated by the compressor 11.

The vehicle suspension system 9 also comprises a storage means in the form of a reservoir 13 for storing compressed air. The reservoir 13 can be employed to rapidly raise the height of the vehicle body 3 above the ground level, for example when raising the vehicle body 3 from a low ride height (in which the vehicle body 3 is lowered with respect to the ground level for facilitating easy entry to/exit from the vehicle 1) to an operative ride height in which the vehicle 1 is driven. The reservoir 13 can advantageously reduce the time period required to raise the vehicle body 3.

The vehicle suspension system 9 comprises control means in the form of a first (rear) valve block 15 and a second (front) valve block 17. The first and second valve blocks 15, 17 comprise one or more valves for selectively controlling the supply of compressed air within the vehicle suspension system 9, for example directing air from the compressor 11 to the air springs 7a-d and/or to the reservoir 13. The pressure lines L16 and the valve blocks 15, 17 collectively form a suspension air gallery. The first and second valve blocks 15, 17 can also be employed to direct air from the air springs 7a-d and/or the reservoir 13 to the compressor 11. A suspension electronic control unit (ECU) is provided for controlling operation of the first and second valve blocks 15, 17.

The compressor 11 is located within a cargo space 19, at the rear of the vehicle 1. (In other embodiments the compressor 11 can be disposed in other locations within the vehicle body 3.) The pressure lines [1-6 are disposed, at least in part, within the vehicle body 3.

As shown in Figure 3, the compressor 11 comprises a piston/cylinder arrangement 21 coupled to a drive means in the form of an electric motor 23. A crank or other suitable mechanism is employed to convert the rotary motion of the electric motor 23 into linear motion of the piston. The piston/cylinder arrangement 21 is arranged to provide a two-stage compression of the air in the cylinder; the piston is moved in a first direction to compress the air in a first stage and in a second direction to compress the air in a second stage.

The compressor 14 is disposed within a housing 25 mounted in the spare wheel well provided in the cargo space 19 of the vehicle 1. The housing 25 comprises a plurality of vent apertures to allow exhaust air to vent from the housing 25, and for the intake of air by the compressor 14. The housing 25 is mounted to a bracket 27 which is hingedly mounted to an enclosure (not shown) including a void for receiving a vehicle battery (not shown). It is envisaged that the battery provided in the enclosure may be employed solely to power the electric motor 23 of the compressor 11 or may power additional vehicle systems, such as, but not limited to, the starter motor and ignition system or an electric vehicle propulsion motor.

A drying station 31 is provided to dry the air supplied by the compressor 11 to the vehicle suspension system 9. The drying station 31 contains a drying agent, such as silica gel, to remove moisture from the air. In use, compressed air supplied by the compressor 11 to the vehicle suspension system 9 is passed through the drying station 31. The drying station 31 comprises an exhaust port 33 through which air can be selectively exhausted from the vehicle suspension system 9. The exhaust port 33 comprises a solenoid operated exhaust pilot valve 35 which can selectively be opened to exhaust compressed air from the vehicle suspension system 9. The exhaust air (which has previously been dried by the drying station 31) is passed through the drying station 31 to remove moisture from the drying agent, thereby regenerating the drying station 31. In order for the regeneration to be effective, a high flow rate of exhaust air is required to remove moisture from the drying agent.

An exhaust system 37 is provided to suppress the generation of audible noise by the exhaust port 33. As shown schematically in Figure 4, the exhaust system 37 comprises an expansion volume defined by an expansion silencer 39; and an exhaust muffler 41. A continuous fluid pathway is formed through the expansion silencer 39 and the exhaust muffler 41. The major flow direction of the exhaust air through the fluid pathway is illustrated by the arrow A in Figure 4. The expansion silencer 39 comprises an inlet 51 operatively connected to the drying station 31; and an outlet 53 operatively connected to the exhaust muffler 41. As shown in Figure 5A, the expansion silencer 39 comprises a sidewall 43, a first end wall 45 and a second end wall 47 which collectively form an expansion chamber 49. An inlet aperture is formed in the first end wall 45 and an outlet aperture is formed in the second end wall 47. A first connector 55 is provided in the first end wall 45 to mount an exhaust pressure line L to connect the expansion silencer 39 to the exhaust port 33. A second connector 57 is provided in the second end wall 47 to mount the exhaust muffler 41 to the second end wall 47. The inlet 51 and the outlet 53 are offset from each other; and, in the present embodiment, are also both offset from a longitudinal axis of the expansion silencer 39. The exhaust muffler 41 remains in fluid communication with an interior of the expansion silencer 39 through said outlet 53. The exhaust muffler 41, which in the present embodiment is a sintered silencer, is open to atmosphere (via the housing 25). Thus, the interior of the expansion silencer 39 is open to atmosphere via the exhaust muffler 41.

As shown in the sectional view shown in Figure SB, the sidewall 43 is generally L-shaped in the present embodiment. An inner section of the sidewall 43 is concave to fit around a cylindrical housing of the drying station 31. This arrangement improves packaging of the expansion silencer 39 within the housing 25. The expansion silencer 39 has approximate dimensions of 83mm (width) x 118mm (length) x 45mm (depth) and an internal volume of approximately 57cm3 (0.000057m3). The expansion silencer 39 has a larger cross sectional area (measured orthogonal to the major gas flow direction A) than that of the exhaust port 33 and the exhaust pressure line LE. The expansion silencer 39 is profiled to form step (non-uniform) changes in the cross sectional area of the fluid pathway formed within the exhaust system 37. A stepped increase in the cross sectional area is formed at the inlet 51; and a stepped decrease in the cross sectional area is formed at the outlet 53. These changes in cross sectional area can reflect or dissipate at least some of the acoustic energy being transmitted when the exhaust port 33 is opened.

The size of the expansion silencer 39 is dependent on the volume of the suspension gallery.

When the exhaust pilot valve 35 is opened, exhaust air from the vehicle suspension system 9 is introduced, under pressure, from the exhaust port 33 into the expansion silencer 39.

There is a high initial pressure pulse when the exhaust pilot valve 35 is opened and this is dissipated within the expansion silencer 39. The pressure of the pulse decreases within the expansion silencer 39, before passing through the exhaust muffler 31 and entering the housing 25. The expansion silencer 39 and/or the exhaust muffler 41 are sized to allow substantially unrestricted flow of air from the exhaust port 33. Accordingly, the exhaust system 37 does not increase the time taken to lower the vehicle suspension system 9.

Moreover, a high flow rate can be maintained through the drying station 31 to permit effective dryer regeneration.

In use, the expansion silencer 39 forms a reactive or reflective silencer, the acoustic energy being reflected within the expansion chamber at the first end wall 45 and at the second end wall 47. The attenuation or transmission loss of the acoustic energy is dependent upon the change in cross sectional area between the first pressure line Li and the expansion silencer 39; the maximum attenuation increases the larger the internal cross sectional area of the expansion silencer 39 is with respect to the internal cross sectional area of the first pressure line Li. The attenuation or transmission loss of the acoustic energy is also dependent upon the length of the expansion silencer 39. In this way the expansion silencer 39 can be optimised or tuned to filter specific noise frequencies.

The configuration of the expansion silencer 39 can be modified without departing from the present invention. An elongate conduit, extending between the exhaust port 33 and the exhaust muffler 41, can be provided to form the expansion silencer 39. The elongate conduit can form an expansion volume into which the exhaust air is expelled from the exhaust pilot valve 35. The elongate conduit can, for example, be formed from a nylon tube. The length and/or internal diameter of the elongate conduit can be selected to provide a sufficient internal volume to dissipate the high initial pressure pulse when the exhaust pilot valve 35 is opened. Again, the expansion silencer 39 and/or the exhaust muffler 41 can be sized to allow a substantially unrestricted flow of air from the exhaust port 33. The elongate conduit can have the same internal diameter as the exhaust port 33 or could have a larger internal diameter.

It will be appreciated that various modifications and changes can be made to the exhaust system 37 described herein. For example, the sidewall 43 of the expansion silencer 39 has been illustrated as having an L-shaped section, but other tubular forms having alternative cross-sectional shapes are envisaged, for example a circular tube, square tube, rectangular tube, oval tube, hexagonal tube and so on. Furthermore, the exhaust system 37 could be configured to be mounted directly to the exhaust port 33.

A further modification of the exhaust system 37 is to combine the expansion silencer 39 and the exhaust muffler 47. For example, the exhaust muffler 47 could form the second end wall 47 of the expansion silencer 39. Alternatively, an expansion volume could be incorporated into the exhaust muffler 47. For example, the sidewall 43 and the second end wall 45 of the expansion silencer 39 could be formed from a porous material.

Further aspects of the present invention are known from the following numbered paragraphs.

1. An exhaust system for a compressor, the exhaust system comprising: an inlet for coupling to an exhaust port of a compressor; an exhaust muffler having a fluid outlet for venting to atmosphere; and an expansion volume, disposed between the inlet and the exhaust muffler, for accommodating the expansion of gas exhausted from the compressor to suppress acoustic noise.

2. An exhaust system as described in paragraph 1, wherein a fluid flow path is formed through the exhaust system.

3. An exhaust system as described in paragraph 2, wherein the expansion volume is profiled to form an increase in the cross-sectional area of said fluid flow path.

4. An exhaust system as described in paragraph 3, wherein the expansion volume is profiled to form a stepped increase in the cross-sectional area of said fluid flow path.

5. An exhaust system as described in paragraph 3, wherein the expansion volume is profiled to form a decrease in the cross-sectional area of said fluid flow path.

6. An exhaust system as described in paragraph 5, wherein the expansion volume is provided to form a stepped decrease in the cross-sectional area of said fluid flow path.

7. An exhaust system as described in paragraph 5, wherein said increase in the cross-sectional area is disposed upstream of the decrease in the cross-sectional area.

8. An exhaust system as described in paragraph 1, wherein said expansion volume comprises an elongate conduit disposed between said outlet port and the exhaust muffler.

9. An exhaust system as described in paragraph 1, wherein the expansion volume comprises a chamber having an inlet aperture and an outlet aperture.

10. An exhaust system as described in paragraph 1, wherein the exhaust muffler is adapted to permit substantially unrestricted fluid flow.

11. An exhaust system as described in paragraph 1, wherein the exhaust muffler comprises a sintered filter.

12. A fluid compressor in combination with an exhaust system as described in paragraph 1.

13. A vehicle suspension system comprising a compressor and an exhaust system as described in paragraph 1, the inlet of the exhaust system being mounted to an exhaust port of said compressor.

14. A vehicle comprising an exhaust system as described in paragraph 1.

15. An expansion silencer comprising: an inlet for coupling to an exhaust port of a compressor; an expansion chamber for accommodating the expansion of gas exhausted from the compressor to suppress acoustic noise; and an outlet for venting gas from the expansion chamber.

Claims

CLAIMS: 1. An exhaust system comprising: an inlet for coupling to an exhaust port of a compressor; an exhaust muffler for venting to atmosphere; and an expansion volume, disposed between the inlet and the exhaust muffler, for accommodating the expansion of gas exhausted from the compressor to suppress acoustic noise.
2. An exhaust system as claimed in claim 1, wherein a fluid flow path is formed through the exhaust system.
3. An exhaust system as claimed in claim 2, wherein the expansion volume is profiled to form an increase in the cross-sectional area of said fluid flow path.
4. An exhaust system as claimed in claim 3, wherein the expansion volume is profiled to form a stepped increase in the cross-sectional area of said fluid flow path.
5. An exhaust system as claimed in claim 3 or claim 4, wherein the expansion volume is profiled to form a decrease in the cross-sectional area of said fluid flow path.
6. An exhaust system as claimed in claim 5, wherein the expansion volume is provided to form a stepped decrease in the cross-sectional area of said fluid flow path.
7. An exhaust system as claimed in claim 5 or claim 6, wherein said increase in the cross-sectional area is disposed upstream of the decrease in the cross-sectional area.
8. An exhaust system as claimed in claim 1 or claim 2, wherein said expansion volume comprises an elongate conduit disposed between said outlet port and the exhaust muffler.
9. An exhaust system as claimed in any one of the preceding claims, wherein the expansion volume comprises a chamber having an inlet aperture and an outlet aperture.
10. An exhaust system as claimed in any one of the preceding claims, wherein the exhaust muffler is adapted to permit substantially unrestricted fluid flow.
11. An exhaust system as claimed in any one of the preceding claims, wherein the exhaust muffler comprises a sintered filter.
12. A fluid compressor in combination with an exhaust system as claimed in any one of the preceding claims.
13. A vehicle suspension system comprising a compressor and an exhaust system as claimed in any one of claims 1 to 11, the inlet of the exhaust system being mounted to an exhaust port of said compressor.
14. A vehicle comprising an exhaust system as claimed in any one of claims 1 to 11.
15. An expansion silencer comprising: an inlet for coupling to an exhaust port of a compressor; an expansion chamber for accommodating the expansion of gas exhausted from the compressor to suppress acoustic noise; and an outlet for venting gas from the expansion chamber.
16. An exhaust system substantially as herein described with reference to the accompanying Figures.
17. A vehicle substantially as herein described with reference to the accompanying Figures.