SE541324C2

SE541324C2 - An air distribution system

Info

Publication number: SE541324C2
Application number: SE1651529A
Authority: SE
Inventors: Emil Pettersson
Original assignee: Scania Cv Ab
Priority date: 2016-11-23
Filing date: 2016-11-23
Publication date: 2019-07-02
Also published as: SE1651529A1; DE102017010542A1

Abstract

An air distribution system comprises an air flow conducting duct (5) and a member connected to the duct and causing a negative air pressure therein generating an air flow in the duct. A channel (11) is connected to the duct at a second location (12) at a distance to a first location (10) along the extension of the duct and leading to an air chamber (13) at the first location. The air chamber assumes a volume and by that a size depending upon the difference of the air pressure in the duct at the second location with respect to that at the first location. A member (15) providing internal walls (16) of the duct defining the cross-section of the duct at the first location (10) is designed to give this cross-section a dependency upon the size of the air chamber (13) maintaining the air velocity in the duct at the first location (10) at a constant level. The invention also relates to a use of an air distribution system, a motor vehicle and a centrifugal force particle separator.

Description

An air distribution system TECHNICAL FIELD OF THE INVENTION The present invention relates to an air distribution system comprising • an air flow conducting duct, • a member connected to the duct to cause a negative air pressure therein generating an air flow in the duct, and • an arrangement arranged at a first location along the extension of the duct and configured to control the air flow in the duct at that location.

Any type of air distribution system having these features is comprised, i.e. where a member, such as a fan or compressor, causes a negative air pressure generating an air flow in a duct and it is desired to control the air flow in the duct at a location along the extension of the duct. However, so as to illuminate but not in any way restrict the invention the case of such an air distribution system containing a centrifugal force particle separator at said first location will now be discussed. Such a particle separator is used to clean the air by making the air to rotate and use centrifugal force to separate particles from the air flow. In an air intake pipe to a combustion engine such a centrifugal force particle separator may be used as a precleaner removing particles from the air to be mixed with a fuel before arriving to the engine and the cylinders thereof. Such a centrifugal force particle separator would work best if the air velocity in it would be constant, and a said arrangement may be used in an attempt to obtaining this in spite of variations of the air flow inside the duct.

BACKGROUND ART An air distribution of the type defined in the introduction is disclosed in EP 1 413 739 A2. The air distribution system described therein is provided with a centrifugal force particle separator at said first location. The arrangement used for control of the air flow in the duct at that location controls the air flow by changing the cross-section of an inlet opening to the separator so that a substantially constant velocity of the air through this inlet opening is obtained. This is made in an attempt to control the function of the separator to be efficient for different air flows through the duct. However, it is very delicate to change the crosssection of an inlet opening to a separator and may be detrimental to the efficiency of the separator since it will in spite of different measures taken in the air distribution system result in variations of the air velocity inside the separator and accordingly a lowering of the efficiency of the separating function thereof.

SUMMARY OF THE INVENTION The object of the present invention is to provide an air distribution system being improved in at least some aspect with respect to such systems already known.

This object is obtained by providing such an air distribution system with the features listed in the characterizing part of appended claim 1.

Thus, the invention is based on the understanding that the generation of an air flow in said duct results in different air pressures at different locations along the extension of the duct and that the size of such pressure differences is depending upon the magnitude of the air flow through the duct, and to use this fact to obtain a constant air velocity in the duct at said first location. This is done by connecting a channel to the duct at a second location at a distance to the first location along the extension of the duct and leading to an air chamber at the first location. The air chamber is at the same time configured to assume a volume and by that a size depending upon the difference of the air pressure in the duct at the second location with respect to that at the first location, and the arrangement has a member providing internal walls of the duct defining the cross-section of the duct at the first location and designed to give this cross-section a dependency upon the size of the air chamber maintaining the air velocity in the duct at the first location at a constant level. This means that in the case of a centrifugal force particle separator at said first location the air velocity will be constant therein irrespectively of variations of the air mass flow in the system resulting in a high efficiency of the separating function of the separator. However, the reason for maintaining the air velocity in the duct at said first location at a constant level may be another than the presence of such a separator at said location, such as any type of filter with a folded design making the filter more efficient when the velocity of the air therethrough is kept at a constant level.

The invention will more exactly result in a cross-section of the duct at the first location increasing with an increased air flow through the duct so as to keep the air velocity at said location at a constant level.

According to an embodiment of the invention the air chamber is defined by walls of an elastic material making it assuming a predefined volume and size in a rest state corresponding to the same pressure prevailing at said first and second location. This feature ensures that the size of the air chamber will be the same for a certain said difference of the air pressure in the duct and by that air flow in the duct whenever this difference of air pressure occurs.

According to another embodiment of the invention said internal walls of the duct define a cross-section of the duct at said first location being smaller than, ? 70%, ? 50% or ? 30 % and at least 10%, of the cross-section of the duct directly upstreams and downstreams of the first location in said rest state. This ensures that the cross-section of the duct at the first location may be increased when the air flow in the duct increases from the condition corresponding to said rest state and still not be larger at said first location than directly upstreams and downstreams thereof. More exactly, if the cross-section of the duct at said first location is for instance 30% of the cross-section of the duct directly upstreams and downstreams of the first location in the rest state the cross-section of the duct at the first location may increase by more than 300% when the air flow through the duct increases so as to keep the air velocity at the first location at a constant level and still keeping the cross-section of the duct at this location below the cross-section of the duct directly upstreams and downstreams of this location.

According to another embodiment of the invention the internal walls of the duct define a cross-section of the duct at the first location being smaller than the cross-section of the duct at the second location in said rest state. By having such a restriction of the duct at the first location with respect to the second location in said rest state a clear said pressure difference will be obtained as soon as there is any air flow in the duct influencing the controllability of the arrangement positively.

According to another embodiment of the invention said member providing internal walls of the duct is configured to form the air chamber, which have the shape of a ring with an internal diameter changing in dependency of the value of said pressure difference. This means more exactly that the internal diameter of the ring will increase with an increasing air flow through the duct.

According to another embodiment of the invention the channel is connected to the duct at said second location upstreams of the first location as seen in the intended direction of air flow in the duct so as to increase said pressure difference caused by an increased air flow in the duct resulting in an increase of the volume of the air chamber to increase the cross-section of the duct at the first location. Thus, in this case the arrangement of the air chamber at the first location is made so that an increase of the volume of the air chamber will result in an increase of the cross-section of the duct at the first location.

According to another embodiment of the invention the air distribution system further comprises a centrifugal force particle separator arranged to be passed by the air flow in the duct at the first location, and the arrangement is configured to control the air flow to have a constant air velocity through the particle separator independently of the value of the air flow through the duct. This results in a high efficiency of the particle separator not dependent upon the total air mass flow through the duct.

According to another embodiment of the invention being a further development of the embodiment last mentioned the member providing internal walls of the duct defining the cross-section of the duct at the first location is located inside the centrifugal force particle separator for forming the internal walls of the separator.

According to another embodiment of the invention the duct is an air intake pipe to a combustion engine and the centrifugal force particle separator constitutes a precleaner removing particles from the air before arriving to the combustion engine. This constitutes an advantageous application of the idea of the present invention.

According to another embodiment of the invention the air distribution system is arranged in a motor vehicle by having the duct forming an air intake pipe leading to a combustion engine of the motor vehicle.

The invention also relates to a use of an air distribution system and a motor vehicle defined in the corresponding appended claims.

Further advantageous features as well as advantages of the present invention appear from the description following below.

BRIEF DESCRIPTION OF THE DRAWING With reference to the appended drawing, below follows a specific description of embodiments of the invention cited as examples.

In the drawing: Fig. 1 is a schematic view illustrating how an air distribution system according to the invention may be arranged in a motor vehicle for providing air to a combustion engine, Fig. 2 is a schematic view of a part of an air distribution system according to a first embodiment of the invention, and Figs. 3 and 4 are schematic views corresponding to Fig. 2 of a part of an air distribution system according to a second embodiment of the invention for two different levels of air mass flow therethrough.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Fig. 1 illustrates schematically the general structure of an air distribution system of the type to which the present invention belongs. The air distribution system is arranged for feeding air to a combustion engine 1 of a motor vehicle 2 and has a turbo charger 3 and a compressor 4 arranged in an intake pipe 5 to the engine and a turbine 6 in the exhaust pipe 7 from the engine, which is connected to the compressor 4 by a shaft 8 driving the compressor by the flow of exhaust gases hitting the turbine blades. Thus, the compressor 4 constitutes a member causing a negative air pressure in a duct 5 in the form of the intake pipe generating an air flow in this duct. Furthermore, a precleaner 9 in the form of a centrifugal force particle separator is arranged in the duct 5 to remove particles from the air flow before reaching the engine.

Fig. 2 shows schematically a part of an air distribution system according to a first embodiment of the invention and which may for instance be a part of the air distribution system shown in Fig. 1. This system has an arrangement configured to control the air flow in the duct at a first location 10 where a centrifugal force particle separator 9 is arranged. This arrangement comprises a channel 11 connected to the duct at a second location 12 at a distance downstreams of the first location along the extension of the duct and leading to an air chamber 13 at the first location 10. The air chamber 13 is defined by walls 14 of an elastic material making it assuming a predefined volume and size in a rest state corresponding to the same pressure prevailing at the first 10 and second 12 location. The air chamber 13 is formed inside a member 15 providing internal walls 16 of the duct and this member has the shape of a ring.

It is shown how guide vanes 17 are arranged at the entrance of the particle separator to set the air into a spin for creating a high velocity swirl separating particles from the air inside the particle separator 9.

Thus, the air chamber 13 will assume a volume and by that a size depending upon the difference of the air pressure in the duct at the second location 12 with respect to that at the first location 10, and the member 15 providing the internal walls 16 of the duct is designed to give the cross-section of the duct at the first location a dependency upon the size of the air chamber maintaining the air velocity in the duct at the first location at a constant level. More exactly, the air pressure will be lower at the second location than at the first location, and this difference will increase with an increased air mass flow through the duct resulting in a decrease of the size of the air chamber 13 and by that an increase of the cross-section of the member 15 inside the particle separator 9, so that the air velocity through the particle separator will be kept constant in spite of the increase of the air mass flow through the duct.

The diameter of the passage through the member 15 in the particle separator may for instance in a rest state corresponding to the same pressure prevailing at the first and second location be half the diameter of the duct directly upstreams and downstreams of the particle separator, which means that the cross-section of that passage will then be 25% of the cross-section of the duct on either side of the particle separator. The cross-section of the passage will then increase with an increased air mass flow in the duct.

An air distribution system according to a second embodiment of the invention is shown in Figs. 3 and 4 and instead of controlling the outer walls of the air distribution system as in the first embodiment the volume inside the air distribution system is here controlled. The channel 111 is in this embodiment connected to the duct 105 at a second location 112 upstreams of the first location 110 as seen in the intended direction of air flow in the duct. This means that the air pressure will at the second location be higher than that at the first location. The channel 111 is at the first location connected to an air chamber 113 in the form of a flexible body with bellows arranged inside the duct 105 and the air pressure therein will be the same as at the second location 112. Thus, the air swirl created by the vanes 117 will pass the first location through the space 120 surrounding the air chamber 113 and surrounded by the wall of the duct 105. The cross section of this space 120 will determine the velocity of the air swirl passing the first location 110.

If the air mass flow increases the difference of the pressure in the duct at said second location and first location will increase resulting in an increase of the volume of the flexible body forming the air chamber. This flexible body is designed to be able to change geometry in a controlled way, here by having bellows allowing the body to move in an axial direction. This means that an increased air mass flow will result in a change of geometry of the flexible body in an axial direction, such as from the shape shown in Fig. 3 to that shown in Fig. 4, so that the bellows’ outer circumference decreases and said space 120 will increase and by that the velocity of the air swirl will be the same as before despite the increased air mass flow through the duct.

The invention is of course in no way restricted to the embodiments described above, since many possibilities for modifications thereof are likely to be obvious to one skilled in the art without having to deviate from the scope of invention defined in the appended claims.

Claims

1. An air distribution system comprising • an air flow conducting duct (5, 105), • a member (4) connected to the duct to cause a negative air pressure therein generating an air flow in the duct, and • an arrangement arranged at a first location (10, 110) along the extension of the duct and configured to control the air flow in the duct at that location, characterized in that said arrangement comprises a channel (11, 111) connected to the duct at a second location (12, 112) at a distance to said first location (10, 110) along the extension of the duct and leading to an air chamber (13, 113) at said first location, that the air chamber is configured to assume a volume and by that a size depending upon the difference of the air pressure in the duct at said second location with respect to that at said first location, and that the arrangement further comprises a member (15) providing internal walls (16) of the duct defining the cross-section of the duct at said first location (10, 110) and designed to give this cross-section a dependency upon the size of the air chamber maintaining the air velocity in the duct at said first location at a constant level. 2. An air distribution system according to claim 1, characterized in that the air chamber (13, 113) is defined by walls of an elastic material making it assuming a predefined volume and size in a rest state corresponding to the same pressure prevailing at said first (1 0, 110) and second (12, 112) location. 3. An air distribution system according to claim 2, characterized in that said internal walls (16) of the duct define a crosssection of the duct at said first location (10, 1 10) being smaller than, ? 70%, ? 50% or ? 30 % and at least 10%, of the crosssection of the duct directly upstreams and downstreams of the first location in said rest state. 4. An air distribution system according to claim 2 or 3, characterized in that said internal walls (16) of the duct define a cross-section of the duct at said first location (10, 110) being smaller than the cross-section of the duct at said second location (12) in said rest state. 5. An air distribution system according to any of the preceding claims, characterized in that said member (15) providing internal walls (16) of the duct is configured to form said air chamber (13), which have the shape of a ring with an internal diameter changing in dependency of the value of said pressure difference. 6. An air distribution system according to any of the preceding claims, characterized in that said channel (11) is connected to the duct at said second location (12) downstreams of said first location (10) as seen in the intended direction of air flow in the duct so as to increase said pressure difference caused by an increased air flow in the duct (5) resulting in a decrease of the volume of the air chamber (13) to increase said crosssection of the duct at said first location (10). 7. An air distribution system according to any of the preceding claims, characterized in that it further comprises a centrifugal force particle separator (9) arranged to be passed by the air flow in the duct (5) at said first location (10), and that said arrangement is configured to control the air flow to have a constant air velocity through the particle separator independently of the value of the air flow through the duct. 8. An air distribution system according to claim 7, characterized in that said member (15) providing internal walls (16) of the duct defining the cross-section of the duct at said first location (10) is located inside the centrifugal force particle separator (9) for forming the internal walls of the separator. 9. An air distribution system according to claim 7 or 8, characterized in that the duct is an air intake pipe (5) to a combustion engine (1) and the centrifugal force particle separator (9) constitutes a precleaner removing particles from the air before arriving to the combustion engine (1). 10. An air distribution system according to claim 9, characterized in that the duct (5) is forming an air intake pipe leading to a combustion engine (1) in a motor vehicle (2). 11. Use of an air distribution system according to any of the preceding claims to provide a combustion engine (1) in a motor vehicle (2) with air.

2. A motor vehicle, characterized in that it is provided with an air distribution system according to any of claims 1-10 to feed air to a combustion engine (1) of the vehicle.