Patent Application
20120273298
This application claims priority to German Patent Application No. 10 2011 100 014.7, filed Apr. 29, 2011, which is incorporated herein by reference in its entirety.
The technical field generally relates to a silencer, in particular for air conditioning systems, preferably vehicle air conditioning systems.
From the prior art, a multiplicity of differently structured silencers are known. Thus, it is already known to design the silencers in such a manner that sound attenuation therein takes place by reflection or absorption of sound waves. Furthermore, silencers are known which have a spirally extending region in order to utilize the flow properties of flowing fluid for sound attenuation.
U.S. Pat. No. 5,246,473 discloses a silencer having a first and a second channel. Along the flow axis, the first channel has a divergent and a convergent section. The second channel has a constant flow cross-section along the flow axis and is formed such that a flow intake region of the silencer can be subjected to a counter pressure pulse.
It is at least one object herein to provide an improved silencer. Other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.
The silencer contemplated herein is based on the effect that sound waves propagate faster in a fast flowing fluid than in a slow flowing fluid, in particular a stagnant fluid. By changing the flow velocity and the associated change of the dynamic pressure as well as the static pressure it is possible in this manner, in particular in a divergent-convergent flow channel, to represent a kind of a barrier which attenuates noises, in particular flow and pulsation noises. The silencer contemplated herein also is based on the effect of interference between two channels communicating with each other upstream and downstream, wherein noises in the one channel interfere with the ones in the other channel and can be attenuated in this manner.
For this, in an exemplary embodiment, a silencer has a first and a second channel. The second channel communicates with the first channel in a branch-off region and a connection region of the silencer. Along a flow axis in the flow direction, each of the two channels has a changing flow cross-section. Accordingly, the flow velocities of the fluid flowing in the first and the second channels differ from each other. Due to the different flow velocities of the fluid, the propagation velocities of the sound waves propagating in the first and the second channels differ also from each other. Due to the different propagation velocities of the sound waves, the sound waves can have different phases when entering into the connection region. Therefore, due to the different profile of the flow cross-section and the resulting phase difference of the sound waves entering into the connection region it can be achieved that an interference takes place, in particular a destructive interference, between the sound waves propagating in the first channel and the sound waves propagating in the second channel. A silencer structured in this manner can have small dimensions and result in low production costs.
The profile of the flow cross-section can change, in particular complementary. In the present case, the customary understanding for this is that an enlargement of the profile of the cross-section of the one channel corresponds to the reduction of the profile of the flow cross-section of the other channel. This can be achieved in particular in that the one channel has an outer channel wall and the other channel arranged in the one channel has an inner channel wall which is parallel to the outer wall, and a channel wall bordering the flow cross-section of the one outer channel on the inside borders at the same time as an outer channel wall the cross-section of the other inner channel. In particular, a complementary change of the profile of the flow cross-section can be achieved in that the one channel has an outer channel wall which is parallel to a flow axis and the other channel arranged in the one channel has no inner channel wall, and a channel wall bordering the flow cross-section of the one outer channel on the inside borders at the same time as an outer channel wall the flow cross-section of the other inner channel.
A flow axis as used herein is to be understood as an axis which extends between an inlet region via which the fluid flows into the silencer and an outlet region via which the fluid discharges from the silencer and through the centers of the flow cross-sections. A flow cross-section is in particular to be understood as the area in the respective channel through which area flow passes through.
In a preferred embodiment, the change in flow cross-section of the first channel along the flow axis can be different from the change in cross-section of the second channel. Thereby is achieved that the flow velocity of the fluid in the first channel differs from the flow velocity of the fluid in the second channel. Thus, the first and/or the second channel can in particular have in each case one or a plurality of divergent sections and/or one or a plurality of convergent sections in which the flow cross-section increases or decreases, respectively. Preferably, the flow cross-section increases or decreases linearly.
A divergent section of the one, in particular, first channel can directly communicate with an inlet region of the silencer through which the fluid flows into the silencer, or can be connected thereto. As a result of the increase in the flow cross-section in the divergent section, it is achieved that the dynamic pressure and therefore the flow velocity of the fluid flowing in this channel decreases. Due to the reduction of the dynamic pressure, the static pressure, which represents a barrier for the sound waves, increases and thus contributes to the sound attenuation. Here, the static pressure is at its maximum in that region of this channel in which the flow cross-section is at its maximum.
The other, in particular, second channel can have a convergent section which communicates with the inlet region of the silencer or is connected thereto. In particular in embodiments in which the profile of the flow cross-section of the first channel is complementary to the profile of the flow cross-section of the second channel, the other channel, due to the divergent section of the one channel, has a convergent section. In the convergent section of the other channel, the dynamic pressure and thus the flow velocity of the fluid increase. As a result of the increase of the dynamic pressure, the static pressure in the convergent section decreases. Here, the static pressure is at its minimum in that region of the other channel in which the flow cross-section is at a minimum. For the case that the flow cross-section of the second channel changes complementary to the flow cross-section of the first channel, the region of the maximum flow cross-section in the first channel and the region of the minimum flow cross-section in the second channel form in the same section of the silencer.
The one, in particular, first channel can have a convergent section upstream of the divergent section or of a divergent section, wherein in the convergent section, the flow cross-section can decrease linearly and can communicate with an outlet region of the silencer. The convergent section can be directly connected to the divergent section or can be directly adjacent thereto. Alternatively, between the divergent and the convergent section of the one channel, an intermediate section can be provided which, for example along the flow axis, has a constant flow cross-section. The flow cross-section of the intermediate section can correspond to the divergent section of the one channel which forms on the divergent section's end facing away from the inlet region. In the convergent section, the dynamic pressure increases as well as the flow velocity of the fluid flowing in the first channel.
The other, in particular, second channel can have a divergent section upstream of the convergent section, wherein in the divergent section, the flow cross-section and the dynamic pressure increase. In particular in embodiments in which the profile of the flow cross-section of the first channel is complementary to the flow cross-section of the second channel, the second channel, due to the convergent section of the first channel, has a divergent section.
In one preferred embodiment, one of the first or second channels can be received in the other one of the first or second channels. In particular, the one channel can be received concentrically to the other channel. The channel walls bordering the first channel can be attached to a silencer wall at least in the inlet region of the silencer and in the outlet region of the silencer. The attachment of the channel walls bordering the first channel can be connected to the silencer wall on the inlet region as well as the outlet region of the silencer via at least one holder, in particular three holders. The holders can involve projections provided on the channel wall which project from the channel wall toward the silencer wall.
In an exemplary embodiment, a third channel can be provided in addition to the first and the second channel. The third channel can be formed concentrically or eccentrically to the first and second channels. The flow cross-section of the third channel can be bordered by the walls of the first and/or the second channel.
Analog to the first and second channels, the third channel can have a flow cross-section which changes along the flow axis. Alternatively, the third channel can have a flow cross-section which does not change along the flow axis.
For the case that the profile of the third channel changes along the flow axis, the third channel, analog to the first and/or the second channel, can have one or a plurality of convergent and/or divergent sections. The profile of a flow cross-section in a convergent or divergent section of the third channel can run identically to the profile of the flow cross-section of the first and/or second channel.
Preferably, the profile of the flow cross-section of the third channel differs from the profile of the flow cross-section of the first and the second channels. Thereby, in the case that the profile of the flow cross-section differs in all three channels, it can be achieved that sound waves having phases which differ from each other reach the connection region. By providing at least three channels, a better sound attenuation can be achieved, because due to the third channel, the sound waves have a phase shift with regard to the two other sound waves.
Channel walls bordering the first and/or the second and/or the third channel can be smooth-walled. In this regard, the flow resistance caused by the walls is low.
According to one embodiment, the silencer can be used in an air conditioning system, in particular in a vehicle air-conditioning system. The silencer can be arranged in a line, in particular a line on the low pressure side of an air conditioning circuit of the air conditioning system. The silencer can likewise be used in further technical fields.
The flow cross-section of the first and second channels can be formed round or circular. Likewise, it is possible that the flow cross-section has a different shape. The fluid can involve a liquid medium such as a refrigerant or water, a gaseous medium such as, e.g. air, or a two-phase fluid-gas or -steam mixture.
An adaptation to different fluids flowing through the silencer can be achieved in particular through a variation of the flow cross-section, in particular in the inlet region and/or outlet region, the length of a convergent section or the convergent and/or divergent section of the respective channel, and/or through a variation of the maximum and minimum flow cross-section, respectively, in the respective channel.
The embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the application and uses of the embodiments herein. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
The silencer 1 shown in
The silencer is formed cylindrically and has an inlet region 2 via which a fluid from the line 40 enters into the silencer 1, and an outlet region 3 via which the fluid discharges from the silencer 1 into the line 40. Further, the silencer 1 has a first channel 11 and a second channel 12 which each extend along a flow axis A from the inlet region 2 to the outlet region 3.
In a branch-off region 20 of the silencer 1, the fluid flowing via the inlet region 2 into the silencer 1 divides into one fluid flow which flows through the first channel 11 and another fluid flow which flows through the second channel 12. In a connection region 30, the two fluid flows from the first and second channels 11, 12 mix and flow via the outlet region 3 out of the silencer 1 into the line 40.
The flow cross-section of the first channel 11 is bordered by a channel wall 13. Along the flow axis A, the first channel 11 has a convergent section 132 in which the flow cross-section decreases linearly, and a divergent section 131 in which the flow cross-section increases linearly and which is connected to the convergent section 132. In the connection section M of the convergent section 132 with the divergent section 131, the flow cross-section of the first channel 11 is at a maximum.
The end of the convergent section 132 with the smaller flow cross-section communicates with the outlet region 3 of the silencer 1, and the other end of the convergent section 132 communicates with the end of the divergent section 131 which has the larger flow cross-section. The end of the divergent section 131 with the smaller flow cross-section communicates with the inlet region 2 of the silencer 1.
The flow cross-section of the second channel 12 is defined by the channel wall 13 and a silencer wall 10 that borders the outer circumference of the silencer 1. The channel wall 13 and the silencer wall 10 are formed smooth-walled. The second channel 12 encloses the first channel 11 along the flow axis A.
Since the flow cross-section of the second channel 12 is bordered by the channel wall 13, the flow cross-section changes complementary to the flow cross-section of the first channel 11. This means that in the region in which the first channel 11 has a divergent section 131, the second channel 12 has a convergent section 142. Furthermore, in the region in which the first channel 11 has a convergent section 132, the second channel 12 has a divergent section 141.
Below, the sound attenuation by means of the silencer 1 is explained. The fluid flow flowing via the inlet region 2 into the silencer 1 is divided in the branch-off region 20 into the fluid flow through the first channel 11 and the fluid flow through the second channel 12. The flow velocity of the fluid flow in the first channel 11 decreases due to the increase of the flow cross-section in the convergent section and reaches its minimum value in the connection section M. At the same time, the fluid velocity of the fluid in the second channel 12 increases in the convergent section 142 and reaches its highest value in the transition region of the convergent section 142 to the divergent section 141.
The flow velocity of the fluid in the first channel 11 increases in the convergent section 132 of the first channel 11 until the fluid discharges into the connection region 30. At the same time, the flow velocity of the fluid decreases in the second channel 12 in the divergent section 141 until the fluid discharges into the connection region 30.
Since the flow velocities of the fluid in the first and the second channels 11, 12 differ from each other, the sound waves in the first and second channels 11, 12 propagate at different velocities. Due to the different propagation velocities, the sound waves entering the connection region have phases which differ from each other so that interference in the connection region 30 takes place.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 100 014.7 | Apr 2011 | DE | national |
