Patent Application
20130277143
The subject invention generally relates to a diffuser for a vehicle exhaust system.
Vehicle exhaust systems are comprised of various components that direct exhaust gas generated by an internal combustion engine to the external environment. The exhaust system includes components that remove contaminants from the exhaust gas and components that control the noise produced by vehicle during operation. One example of a noise reduction component is a muffler. Exhaust gas passes through the muffler and exits to the external environment through a tailpipe. Flow noise is generated as exhaust gas exits the tailpipe.
Previous proposed solutions for addressing flow noise have included using a larger tailpipe or using a perforated inner tube or high frequency tuner within the muffler. These prior solutions were disadvantageous from a packaging perspective and presented tuning challenges.
Another proposed solution is to mount a diffuser to the tailpipe. The diffuser is mounted to an end of the tailpipe and is configured to diffuse and dilute exhaust gas exiting the vehicle. One adverse effect of using a diffuser is an increase in exhaust system backpressure, which is undesirable.
A diffuser for a vehicle exhaust system includes a body defined by a tubular portion comprising an outer peripheral wall extending about a central axis and at least one surface that extends at an angle relative to the central axis. A tailpipe connection interface is formed at one end of the tubular portion.
In one example, the at least one surface extends at an oblique angle relative to the central axis.
In another example, the at least one surface comprises at least a first surface extending at a first angle relative to the central axis and a second surface extending at a second angle relative to the central axis.
In one example, the first and second angles are oblique angles relative to the central axis.
In one example, a first plurality of holes is formed within the outer peripheral wall and a second plurality of holes is formed within the at least one surface.
In one example, the first plurality of holes is defined by a first diameter and the second plurality of holes is defined by a second diameter that is different than the first diameter.
In one example, the first diameter is greater than the second diameter.
In one example, the body is defined by an outer surface area and the first and second pluralities of holes define a total open area portion of the outer surface area that is at least 50%.
In one example, the total open area portion is within a range of 54% to 80% of the outer surface area.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A vehicle exhaust system 10 directs exhaust gas generated by an internal combustion engine 12 to the external environment. The exhaust system 10 includes a series of pipes 14 and one or more components 16 that remove contaminants from the exhaust gas. The exhaust system also includes components that control the noise produced by vehicle during operation. One example of a noise reduction component is a muffler 18. Exhaust gas passes through the muffler 18 and exits to the external environment through a tailpipe 20. Flow noise is generated as exhaust gas exits the tailpipe 20.
In order to reduce the flow noise, a diffuser 22 is mounted to the tailpipe 20. The diffuser 22 is mounted to an end of the tailpipe 20 and is configured to diffuse and dilute exhaust gas exiting the vehicle.
In one example shown in
In one example, the tubular portion 32 is configured to be attached to a tailpipe having an overall diameter of 2.5 inches or less. In one example, the tailpipe connection interface 38 of the diffuser 22 comprises weld connection to the tailpipe 20; however, other methods can be used to attach the diffuser 22 to the tailpipe 20.
Any type of metallic material can be used to form the diffuser. A material with good corrosive properties is preferred.
In this example, the body 30 and angled surface 36 cooperate to define a cup-shaped diffuser. The angled surface 36 is generally orientated at a perpendicular angle relative to the central axis A and forms an end face of the diffuser 22. The outer peripheral wall portion extends axially from an outer periphery of the surface 36 in a direction common with the central axis A to form the tubular portion 32.
As shown in
In the example shown in
As shown in
In this example, the angled surface 36b is orientated at an oblique angle relative to the central axis A.
The angled surface 36b provides a tapered end face of the diffuser 22b with a distal edge 50 of the surface 36b being spaced a greater axial distance from the tailpipe connection interface 38b than an opposite edge 52 of the surface 36b. The outer peripheral wall 34b extends in an axial direction from an outer peripheral edge of the tapered end face to the tailpipe connection interface 38b. In the example of
In this example the diameters D1, D2 of the holes 40b, 42b are generally equal to each other. However, the holes 40b, 42b could also have diameters that are different from each other. Preferably, the second plurality of holes 42b would have a larger diameter D2 than the diameter D1 of the first plurality of holes 40b such as in the example of
In the example shown, the first holes 40d are defined by a diameter D1 that is greater than a diameter D2 of the second holes 42d.
Further, as best shown in
In each of the embodiments disclosed above, the tailpipe diffuser is used to reduce flow noise. As discussed above, the percentage of open surface area in the diffuser is critical to eliminating back pressure issues that are created in the attempt to address the flow noise. Generally, an open area of 54% provides an ideal configuration for reducing noise and back pressure; however, a range of open area could comprise 54%-80%. Further, the combination of two different hole sizes for the tubular portion and angled surfaces also assists in reducing back pressure. Also, having at least one obliquely angled surface further enhances the reduction of noise and back pressure compared to the configuration of
The combination of the 60/40 open area ratio with the overall open area of 54% of the total surface area greater than tailpipe connection interface diameter provides the most effective noise and back pressure reduction. This combination effectively reduces flow created by high velocity flow through a small diameter pipe to obtain a more subjectively pleasing sound without significantly increasing back pressure.
The shape of the diffuser is uniquely configured to create a flow distribution that is a minimal to back pressure increase. The angled surface creates more surface area for the 60 (smaller hole surface)/40 (larger hole surface) split where the smaller sized holes are on the angled surfaces and the larger holes are on the tubular portion. The angle of the surfaces also disperses the air flow more evenly through the holes. The mismatch between the holes sizes compliment diffusing the high velocity flow in small diameter tailpipes while at the same time limiting restriction. Experimental testing showed that if a 54% open area larger than the pipe diameter is maintained, balancing the 60/40 split between the different hole sizes results in a minimal increase to restriction. Further, tailpipe acoustic content is also reduced with this diffuser tip configuration.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
