US3747704A

US3747704A - Silencer

Info

Publication number: US3747704A
Application number: US00255381A
Authority: US
Inventors: C Ware
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-05-22
Filing date: 1972-05-22
Publication date: 1973-07-24
Anticipated expiration: 1990-07-24
Also published as: IT987763B; CA976437A; DE2318814A1; GB1437717A; IL42099A; JPS4943040A; FR2185750B1; IL42099A0; FR2185750A1

Abstract

A silencer for attenuating sound coming from a source,having high and low fluid pressure and flow variations is disclosed. The silencer features a housing having an inlet connected to the source, a throat and two divergent branches for the flow of fluid therethrough. A first means coupled to the throat directs fluid pressure and flows from the source to one of the branches and a second means coupled to the throat diametrically opposed to the first means diverts the fluid pressure and flow to the other branch when the pressure in the second means is greater than the fluid pressure and flow at the first means. The second means includes a means for deriving a mean pressure, viz., attenuates peak pressures so that fluid pressure and flow variations at the other one of the divergent branches are reduced.

Description

[. July 24, 1973 SILENCER [76] Inventor: Colin C. Ware, 83 Tamarack Drive,

Rochester, N.Y. 14622 [22] Filed: May 22, 1972 [21] Appl. No.: 255,381

Primary Examiner-Richard B. Wilkinson Assistant Examiner-John F. Gonzales Attorney-Samuel R. Genca [5 7] ABSTRACT A silencer for attenuating sound coming from a source,having high and low fluid pressure and flow variations is disclosed. The silencer features a housing having an inlet connected to the source, a throat and two divergent branches for the flow of fluid therethrough. A first means coupled to the throat directs fluid pressure and flows from the source to one of the branches and a second means coupled to the throat diametrically opposed to the first means diverts the fluid pressure and flow to the other branch when the pressure in the second means is greater than the fluid pressure and flow at the first means. The second means includes a means for deriving a mean pressure, viz., attenuates peak pressures so that fluid pressure and flow variations at the other one of the divergent branches are reduced.

12 Claims, 9 Drawing Figures PAIENIEQJUM 3.741. 70 1 SHEET 1 0F 2 Fig. 4

PATENIEDJULZMQTS SHEET 2 BF 2 42 Fig. 6

SILENCER BACKGROUND OF THE INVENTION I. Field of Invention The present invention relates to an anti-pollution device and more particularly to silencers.

2. Prior Art Although the present invention is suited for more general applications such as devices for suppressing fluid pulsations, pressure and flow variations from a source, it is particularly adapted for use in an internal combustion engine exhaust system such as but not limited to muffling of exhaust noise. Mufflers and resonators for internal combustion engines are well known to those skilled in the art. While prior art mufflers and resonators have been satisfactory for their intended purpose, problems of noise suppression still exist and discharge of pollutents in the atmosphere is still prevalent with these devices. Accordingly, there is a pressing need for a silencer that will not only suppress noise but will also reduce pollution.

SUMMARY OF THE INVENTION Briefly described, a silencer in accordance with a preferred embodiment of the invention includes a housing having an inlet for receiving a pulsating fluid from a source having high and low fluid pressures and flow variations and two divergent branches for the flow of fluid therethrough. The housing has'a throat region interposed between the inlet and the two divergent branches. A first means is disposed at the throat for directing the fluid pressure and flow to one of the branches and a second means is connected between the throat and the one branch for diverting the fluid pressure and flow variations to the other'branch only when the pressure in the second means is greater than the fluid pressure at the first means in the throat. The second means includes an attenuator for deriving a mean pressure or pressure lower than a peak pressure therein so that peak pressures which are higher than the mean pressure on the above said lower pressure in the attenuator are directed into the attenuator through the first branch and when the fluid pressure or flow variations from the source are lower than the pressure in the attenuator, the fluid pressure and flow variations at the throat are directed to the other branch. In other words, the fluid pressures and flow variations from the source which are in effect alternating variations are reduced to a substantially constant level, thus suppressing noise.

DESCRIPTION OF THE DRAWINGS The invention both as to its organization and method of operation, will best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. I is a longitudinal sectional view of a silencer embodying the features of the invention;

FIG. 2 is a graph relating fluid pressure and flow variation from a source such as an internal combustion engine;

FIG. 3 isa side view of a motor vehicle exhaust system showing that a silencer made in accordance with FIG. 5 is a longitudinal sectional view of a silencer made in accordance with a preferred embodiment of the invention;

FIG. 6 is a longitudinal sectional view of another silencer made in accordance with the invention;

FIG. 7 is a longitudinal sectional view of yet another silencer made in accordance with the invention;

FIG. 8 is a cross-sectional view of the silencer shown in FIG. 5 taken along line 8-8;

FIG. 9 is a fragmentary cross-sectional view of the silencer similar to the silencer in FIG. 5 only disposed at the manifold section of the engine.

DETAILED DESCRIPTION Referring to the drawings, there are shown various embodiments of the invention in silencers which are not only suited for other applications as stated above, but which are particularly adapted for internal combustion engines such as shown at l. The engine 1 when operating on fuel such as gas or oil, discharges exhaust gases from each cylinder, one of which is partly shown at 2 (FIG. 9) after each burning of fuel within the cylinder 2. The exhaust gases bypass an exhaust valve 3 through exhaust port 4. In accordance with the invention, a SILENCER 90 may be coupled to the engine 1 at

exhaust port

4 and 5 which is generally the region in which a conventional exhaust manifold may be assembled to the internal combustion engine 1. If desired, however, the SILENCER may be installed at another location such as at 7 with respect to engine 1, for. example, SILENCER 10 (FIG. 10);SILENCER 40 (FIG. 4); SILENCER 50' (FIG. 5); SILENCER 60 (FIG. 6) or SI- LENCER (FIG. 7) may be employed to silence exhaust noise at port 4 by a connection from the engine at the manifoldregionat 5 by exhaust pipe 6. Thus the present invention is interchangeable with present mufflers which are usually located at 7 to suppress noise.

Those skilled in the art will appreciate the above mentioned components of the engine I and their operation. It is also well known to those skilled in the art that engine 1 when operating, exhaust carbon dioxide, carbon monoxide, hydrocarbons and other pollutants through the exhaust port 4 as well as noise. The engine 12 generates sound waves at the exhaust port 4 having a frequency that is a function of the engine speed (revolutions per minute) and the number of combustion cylinders 2. This frequency is sometimes referred to as the firing frequency and is illustrated by the curves 21, 22 illustrated in FIG. 2. The curves 21, 22 are representative of the firing and exhausting frequency and each

peak

23, 24 of curves 2], 22 respectively, indicates an exhausting from a cylinder 2. Curve 21 represents fluid inlet pressure with a time base while curve 22 represents inlet fluid flow eith the same time base, both of which happen to have the same frequency for the internal combustion engine 1. Horizontal line 25 incurve 21 is the mean or average pressure while the horizontal line 26 is the average flow of the curve22.

Referring first to FIG. 1, a SILENCER 10 in accordance with the invention is shown. The SILENCER 10 includes an inlet at I1 and two divergent branches 12, I3 and a throat region at I4. The throat region is preferably a venturi having a uniformly converging section to a reduced cross-sectional area and adiverging section expanding towards the divergent branches 1 2 and 13.

Branch 13 is connected to a pipe 15 to an outlet 16. Divergent branch 12 is connected to an attenuator 17 in which peak pressure and flow are attenuated and mean pressure or lower pressure than the peak pressure is derived. Connected between the attenuator 17 and an attenuator port 18 at the throat region 14 is a tube or pipe 19 for directing pressure from the attenuator 17 to the attenuator port 18 substantially normal to the flow of gases in the throat region 14. This tube or pipe 19 may have a length equal to one quarter wave length of the operating or firing frequency of the engine 1. Fluid pressure and flow at the inlet 11 is sensed by a tube or pipe 9 connected between the inlet 11 and a port 20 at the throat region 14. This tube or pipe 9 is also in the order of one quarter wave length of the operating frequency of the engine 1. The port 20 is diametrically opposed to the attenuator port 18 and the flow of gases from the port 20 is also substantially normal to flow of gases in the throat region 14. The length of tube 9, 19 is not restricting.

In the operation of the SILENCER 10, exhaust gases having fluid pressure and flow variations such as the type emitted from the source or the engine 1 are admitted at inlet 11 and travel down the throat region 14 and at the same time travel in tube or pipe 90 in phase with the exhaust gas traveling within the throat region 14. If the pressure or flow within attenuation port 18 is less than the pressure or flow at port 20, exhaust gases are directed towards divergent branch 12 and into attenuator 17. The exhaust gases in the attenuator 17 are allowed to expand and a reduction pressure is achieved in the attenuator 17. This reduced pressure in the attenuator 17 may be the mean of average pressure 26 or flow as shown in the curves 21 and 22 respectively in FIG. 2. The reduced pressure in the attenuator 17 is sensed by the tube or pipe 19 and this reduced pressure or flow is fed back into the throat region 14 in a substantially normal direction to the gases flowing in the throat region 14, and if the pressure or flow at port 20 is less than the pressure or flow at attenuator port 18, the exhaust gases are directed to divergent branch 13 and are exhausted to the atmosphere through pipe 15 and outlet 16. Since exhaust gases flowing within the throat region 14 do have flow and pressure variation, the gases may be directed to either one of the divergent branches 12, 13 as a function of the diametrical flow or pressures at ports 18 and 20. The diametrical pressures are a function of the flow and pressure variations of the exhaust gases. The maximum pressure and flow in the attenuator 17 cannot be greater than .peak pressure of the exhaust gases from the engine 1 because any higher pressure or flow than peak pressure in the branch 12 will direct flow and pressure to divergent branch 13. The peak pressure 23 and flow 24 will normally be directed to branch 12 and attenuator l7 and be attenuated or reduced therein when pressure and flow at port 20 is greater than flow at port 18. The effective reduced or average pressure in the attenuator l7 and at port 18 however may be greater than pressure or flow in the throat region 14 and port 20 so that the exhaust gases in the throat region 14 will be directed to the divergent branch 13 and exhausted through pipe and outlet 16. As was mentioned earlier, the exhaust gases in the throat 14 the port 20 are in phase with each other and therefore it may now be seen that the peak pressures and flow are chopped by the attenuator 17 and energy as shown by cross-section at 28 of curve 22 is shifted in phase and dumped into the shaded area 29 of curve 22 so that the resultant pressure and flow waves shown by curves 21, 22 (FIG. 2) is in effect substantially a straight line illustrated as an average or mean pressure at 26. Thus, pressure and fluid flow variations are reduced or substantially eliminated by the SI- LENCER 10 to suppress noise.

While the operation of the SILENCER 10 has been described by the use of exhaust gases from a source or engine 1, it should be understood that the invention will also function in the same manner for fluids having sound waves since such waves are alterations in pressure and particle displacement and may be shifted to the divergent branches l2 and 13 as a function of the relative pressures at ports 20 and 18 and then may either be discharged or attenuated to derive a steady state condition without objectionable variations.

Referring now to FIGS. 4 to 9, various embodiments of the invention are shown in

SILENCERS

40, 50, 60, and 90. These

SILENCERS

40, 50, 60, 70 and are of similar construction; accordingly, like elements and structures will have designations and reference numerals which are alike.

The SILENCER 40 may be connected to the engine 1 by 7 by a pipe 6 (FIG. 3), at inlet 41. The SILENCER 40 is similar to the SILENCER 10, except that the attenuator 42 for the SILENCER is a wrap around attenuator 42 instead of being a closed end attenuator 17 as shown in FIG. 1. The wrap around attenuator 42 provides a more compact SILENCER 40 than the SI- LENCER 10. The attenuator 42 includes end caps 36, 37 in sealing relationship with a wrap around member 35, inlet 41 and outlet 38. The SILENCER 40 includes

divergent branches

43, 44 and a throat region 45 interposed between the inlet 41 and the

divergent branches

43, 44. The throat region 45 is similar to throat region 14 of the SILENCER l0 and is a venturi. Pressure at the inlet 41 is sensed by a tube or pipe 46 terminating at port 47. The length of the tube or pipe 46 is less than a quarter wave length of the operating frequency of the engine 1. The port 47 at the throat 45 has a crosssection area equal to about one third of the crosssection of the cross-sectional area of throat region 45 at the smallest cross-section of the throat 45. However, this is not a limiting condition and may be varied if desired without departing from the invention. The pressure or flow at port 47 is directed normal to the flow of fluid in the throat 45. The divergent branch 44 is coupled to the attenuator 42 which functions similar to the attenuator 17 except that a baffle 48 is included to divert fluid flow and pressure waves entering the attenuator 42 and also for stopping reflected pressure and flow from re-entering the branch 44. Pressure in the attenuator 42 is senses at the tube or pipe 49 which is connected to attenuator port 39. The attenuator port 39 is diametrically opposed to port 47 and may be of the same size as port 47. Pressure and flow at the port 39 is normal to the flow of fluid in the throat region 45. Divergent branch 43 is connected to an outlet 38.

The operation of the SILENCER 40 is similar to the operation of the SILENCER 10 except that the attenuator is wrapped around the throat region 45 and accordingly, operates at a slightly higher temperature. Also, the SILENCER 40 includes a baffle 48 disposed proximal to the divergent branch 44 not only for directing fluid flow and pressure theoughout the attenuator but also for preventing a reflection or bouncing back of fluid flow or pressure.

Assuming for purposes of describing the operation of the SILENCER 40, the exhaust gases from the engine I are pulsating in a manner similar to the wave form 21 shown in FIG. 2 and are applied to inlet 41. Each of the pressure peaks 23 occur at an exhaust of gas from the cylinder 2 while the valleys between the peaks are between firing time so that the pressure curve 21 is a function of time. The exhaust gases entering the inlet 41 are passed to the throat region 45 directly and at the. same time and in phase so that a peak pressure 23 will be present at the throat region 45 and at port 47 since the peak pressure was sensed through tube. 46. Assume also that there is a relatively low pressure at port 49 and attenuator 42 and the pressure tube 46 and port 47 will direct the exhaust gas therein normal to the flow of exhaust gases in the throat region 45 so that the resultant flow of the exhaust gases is towards the divergent branch 44 and attenuator 42.

A study of vector analysis will show that when two flows are perpendicular to each other, the gases will travel in a resultant direction into the divergent branch 44 and thence into the attenuator 42. The gases in the attenuator will expand and be directed by the baffle 48 throughout the attenuator 42. At the same time, the pressure in the attenuator will increase and be applied to port 39 by tube 49. If the pressure at 39 is greater than the pressure at port 47, the exhaust gases will be directed towards branch 43 and exhausted through outlet 38. However if the pressure at port 39 is still less than the pressure at port 47, the gases will continue to be directed to divergent branch 44 until the pressures at

ports

39 and 47 are equal at which time the exhaust gases may be directed to both of the

divergent branches

43, 44.

In effect then, peak pressure 23 is directed to the attenuator 42 where they are attenuated or chopped and shifted in phase between the next peak pressure as more particularly shown in FIG. 2 where the flow 28 and energy content is dumped into the valley to raise its pressure and energy as shown by the shaded area 29,

thereby reducing the pressure in the attenuator.

THE PREFERRED EMBODIMENT Referring now to FIGS. and 8, a SILENCER 50 in accordance with a preferred embodiment of the invention is shown. The SILENCER 50 is similar to the SI- LENCER 40 except that the sensing tubes or

pipes

46 and 49 and

ports

47 and 39 respectively are eliminated. Instead a new throat region 51 is employed having the same effectiveness as the

ports

39 and 47.

A header port 52 is disposed at approximately the same place as port 47 and directs fluid flow and pressure to branch 44 while another header port 53 directs fluid pressure and flow to the branch 43 when the differential pressures thereat are appropriate in a manner to be described hereinafter. The throat region 51 of the SILENCER 50 is rectangular as shown in FIG. 8 and is a venturi having a smaller cross-sectional area proximal to

header ports

52 and 53 and expands therefrom into

divergent branches

43, 44. The remaining components and elements of the SILENCER 50 are similar to corresponding components and elements of the SILENCER 40 and are similarly numbered as previously stated.

In the operation of the SILENCER 50, exhaust gases are directed to the throat 51 from inlet 41. The exhaust gases as described before have the same waveform and. as a consequence, each pressure peak 23 coming in contact with header port 52 directs pressure normal to the exhaust gases traveling through the throat 51 so that a result flow of exhaust gases isdirected to attenuator 42. To further assist the flow of gases to the attenuator, the header port 53 may have a low pressure thereat when the. pressure 52. is at or near a peak pressure. However, when the pressure in the attenuator 42 increases and approaches peak pressure, the header port 53 in cooperation with the pressure in the attenua: tor 42 directs the flow of gases to branch 43 and outlet 38.

The SILENCER 90 of FIG. 9 is similar to the SI- LENCER 50 except that it is connected to the engine 1 at 5 and it includes an attenuator 92 which is structurally and functionally similar except that it has a rectangular cross-section and is used in common with other SILENCER 90 and thus also serves as an exhaust manifold for the engine 1.

Referring now to FIGS. 6 and 7, SILENCERS 60 and 70 are shown. These

SILENCERS

60, 70 are similar to SILENCER 50 of the preferred embodiment of the invention.

SILENCER 60 is similar to SILENCER 50 except that it includes a throat region 61 having the sensing tube and port 39 of the SILENCER (FIG. 4). SI- LENCER 70 is similar to SILENCER 50 except that it includes a throat region having the sensing tube or pipe 46* and port 47. It will be seen that in principle, the exhaust gases flowing through the

throat region

61 or 71 of SILENCERS 60, 70 respectively will be directed to one of the

divergent branches

43 or 44 depending upon the differentially opposed pressures acting normal to the transverse flow of exhaust gases through the throat, which differential pressures are presented by the

header ports

52 and 53 or

ports

39 and 47 as a combination of the ports and -port headers. The SILENCER 60 also includes another baffle 62 in the attenuator 42 to dispurse and achieve a mean pressure in the attenuator 42.

In the operation of the SILENCER 60, exhaust gases are admitted at the inlet 41 and are accelerated at the venturi throat region 61 whence the header port 52 directs the exhaust gases to the divergent branch 44 since the normal pressure acting on the transverse gases flowing through the throat region 61 is higher at 52 than at 39. From the branch 44, the gases enter the attenuator 42 and are expanded therein. The tube 49 senses the pressure in the attenuator 42 and the pressure in the attenuator 42 is present at 39 when it acts normal to the flowing of exhaust gases through the throat region 61. Now if the pressure at port 39 is greater than the pressure at header port 52, the exhaust gases will be directed to the divergent branch 43 and through outlet 38. However, if the pressure'at port 39 is less than the pressure at header port 52, the exhaust gases will be directed towards the branch 44 as previously stated. If the pressure at port 39 and header port 52 are equal, the gases will flow in the path of least resistance, namely, through branch 43 and outlet 38. It may now be seen in the

SILENCERS

10, 40, 50, 60, and that the pressure in the attenuator is a floating reference pressure which adjusts to conditions and levels the fluid flow and pressure variations to reduce or suppress noise.

The SILENCER 70 operates in a manner similar to the

SlLENCERS

10, 40, 50, 60, 90 and functions in a similar manner, that is the difference in pressure at header port 53 and port 47 controls the flow of fluid, gases and liquids automatically to the attenuator 42 or to the outlet 38 as just described.

The

divergent branches

43, 44 may be symmetrical or assymmetrical with respect to the longitudinal axis of the

throat regions

51, 61, 71 of the SILENCERS S0, 60, 70 respectively to controlthe amount of flow to outlet 38 or attenuator 42.

While specific embodiments of the invention have been desc-ibed and shown, these may be considered illustrative. Still further modifications will undoubtedly occur to those skilled in the art. Therefore, the foregoing description is to be considered as illustrative and not in any limiting sense.

What is claimed is:

l. A silencer comprising:

a. a housing having an inlet for receiving a fluid having high and low fluid pressure and flow variations and at least two divergent branches,

b. said housing having a throat region interposed between said inlet and said two divergent branches,

- c. first means disposed at said throat for directing said fluid pressure and flow to one of said branches, and

(1. second means connected between said throat and said one branch for diverting said fluid pressure and flow variations to said other branch when the pressure in said second means is greater than said fluid pressure at said first means in said throat.

2. The invention defined in claim 1 wherein said second means includes attenuation means for deriving a mean pressure therein.

3. The invention defined in claim 1 wherein said second means includes means for reducing said fluid pressure and flow variations.

4. The invention defined in claim 1 wherein said second means includes an attenuator.

S. The invention defined in claim 1 wherein said throat region is relatively long.

6. The invention defined in claim 1 wherein said throat region is relatively short.

7. The invention defined in claim 1 wherein said throat is a venturi.

8. The invention defined in claim 1 wherein said divergent branches diverge along a symmetrical axis of said throat region.

9. The invention defined in claim 1 wherein said divergent branches diverge along an asymmetrical axis of said throat region.

10. The invention defined in claim 1 wherein said second means includes a deflector means disposed proximal to said one divergent branch for diverting re flected pressure waves within said second means when present.

11. The invention defined in claim 1 wherein said second means is diametrically opposed to said first means in said throat region.

12. The invention defined in claim 1 wherein said first and second means are fixed in cooperative relationship to each other and said throat region.

Claims

1. A silencer comprising: a. a housing having an inlet for receiving a fluid having high and low fluid pressure and flow variations and at least two divergent branches, b. said housing having a throat region interposed between said inlet and said two divergent branches, c. first means disposed at said throat for directing said fluid pressure and flow to one of said branches, and d. second means connected between said throat and said one branch for diverting said fluid pressure and flow variations to said other branch when the pressure in said second means is greater than said fluid pressure at said first means in said throat.

5. The invention defined in claim 1 wherein said throat region is relatively long.

7. The invention defined in claim 1 wherein said throat is a venturi.

10. The invention defined in claim 1 wherein said second means includes a deflector means disposed proximal to said one divergent branch for diverting reflected pressure waves within said second means when present.