Emission control apparatus

Apparatus for controlling emissions from an internal combustion engine including an enclosed cylindrical housing and a converter assembly coaxially mounted in the housing for reducing noxious gases emitted from the engine. The converter assembly is characterized by a catalytic module transversely disposed within the housing at a predetermined location between an inlet and an outlet, thereof. The center of the catalytic module is formed by a cylindrical hub closed against flow of exhaust gases therethrough, surrounded by a catalytic cell of annular cross-section through which exhaust gases from the engine may flow, converting nitrogen oxides, carbon monoxide and unburned hydrocarbons to less noxious compounds before being discharged through the outlet. The hub is normally closed against flow of exhaust gases by a closure member. The closure member is openable in response to abnormal increases in pressure from the engine exhaust to prevent damage to the catalytic cell.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention pertains to apparatus for use with internal 
combustion engines to reduce emission of noxious gases and noise emitted 
therefrom. More specifically, the present invention pertains to apparatus, 
particularly suited for use with a natural gas fueled engines, for 
converting nitrogen oxides, carbon monoxides and unburned hydrocarbons 
from the exhaust of such engines to less noxious compounds and for 
reducing the noise emitted therefrom. 
2. Brief Description of the Prior Art 
Both noise and air pollution have been of increasing concern in recent 
years. Silencers or mufflers for noise reduction of internal combustion 
engines have existed for many years. Most industrial silencers utilize 
some type of housing in which is mounted various types of baffles or other 
silencing components for reducing the noise produced at the exhaust of an 
internal combustion engine. 
Of more recent and heightened concern is air pollution created by noxious 
gases emitted from the exhaust of an internal combustion engine, primarily 
nitrogen oxides, carbon monoxides and other unburned hydrocarbons. 
Catalytic converters have been developed through which the exhaust gases 
may be passed for converting the nitrogen oxides, carbon monoxide and 
unburned hydrocarbons to less noxious compounds before being discharged to 
the atmosphere. Problems associated with three-way catalytic converters 
have been identified as: precise air/fuel ratio control, deactivation of 
the catalyst and flow distribution in the catalytic converter. The flow 
distribution problem is the one least investigated and the one which holds 
most promise in increased efficiency and extended catalyst life. 
Exhaust silencers and catalytic converters for internal combustion engines 
are governed by chemical, fluid flow, and acoustical characteristics. 
These characteristic interact with each other and when properly combined 
provide an efficient exhaust system for control of air and noise 
pollution. 
Air pollution and noise abatement equipment may take many forms or 
configurations. For example, the engine may be provided only with a 
catalytic converter or with a catalytic converter first and then a 
silencer or with a silencer first and then a catalytic converter. In more 
recent years, catalytic converters and exhaust silencers have been 
combined in a single housing. Examples of such may be seen in U.S. Pat. 
Nos. 4,601,168; 5,016,428 and 5,184,464. 
Especially in the manufacture of a combined catalytic converter and exhaust 
silencer all three disciplines or characteristics (chemical, fluid flow 
and acoustical) must be considered and properly balanced. Exhaust 
silencing quality, emissions reduction efficiency, and engine efficiency 
all depend upon a proper combination. 
As previously stated, one of the primary problems to consider in a combined 
catalytic converter and exhaust silencer, particularly for efficiency of 
catalytic conversion, is flow distribution. In recent years, research has 
been conducted to determine the velocity profile of exhaust gases entering 
the frontal area of the catalyst module of a catalytic converter. One such 
study has been reported in a paper entitled Improvement of Catalytic 
Converters for Stationary Gas Engines by Using a Metal-Supported Catalyst, 
Y. Tsurumachi and A. Fujiwara and Y. Yamada all of Tokyo Gas Co., Ltd. 
Tokyo, Japan. Research has produced evidence that exhaust gases entering a 
catalytic converter housing at high velocity concentrate in the center 
core of the catalytic converter module in a pattern substantially the same 
diameter and area as the inlet. Other results of the research show that 
when a truncated conical inlet transition is provided exhaust gases 
recirculate around the transition causing flow maldistribution and 
scattered hot and cold spots in the frontal area of the catalyst module, 
reducing conversion efficiency. 
Catalytic converters of relatively small frontal area result in increased 
impingement velocity and higher linear velocity through the catalyst 
depth. This creates higher back pressures, raising the mean effective 
pressure in the exhaust system between the catalytic converter and the 
engine exhaust valves. Undersized exhaust silencers can also increase the 
back pressure and when coupled with an undersized catalytic converter 
multiply the back pressure many times over, reducing operational 
efficiency of the engine. 
Velocity control and pulsation dampening are products of capacity made 
possible by diameter and length. Diameter controls velocity and length 
controls expansion of exhaust gases to achieve design velocity and reduced 
pulsation level. In addition, staging pulsation (manifested as vibration 
and noise due to engine firing frequency) helps flow condition the exhaust 
gases upstream of the catalyst to assure even distribution of exhaust 
gases to the catalyst face. 
From a chemical standpoint, residence time of exhaust gases through a 
catalyst module is important for catalytic reduction of toxic emissions. 
Research has determined that the linear velocity through the catalyst 
should be between 14 and 17 actual feet per second to provide optimum back 
pressure and residence time for conversion. In order to efficiently 
utilize the three characteristics or disciplines in the design of an 
internal combustion engine exhaust system, the catalytic converter module 
should be manufactured to accept exhaust gases at the prescribed velocity, 
maintaining linear velocity through the catalyst module depth while 
providing optimum residence and conversion therethrough. 
Another problem associated with catalytic converters, whether in 
combination with a silencer or not, is the damage thereto that may be 
created by engine backfires. A typical engine backfire may result in an 
increase in pressure to as much as 100 psi. Such a rapid increase in 
pressure and velocity therefrom may actually blow a hole or otherwise 
damage the catalyst module of a catalytic converter. This would require 
replacement of an expensive, only partially otherwise depleted, catalytic 
cell or module. Some attempts have been made to overcome this problem, 
including the provision of relief valves in the engine exhaust piping 
prior to connection with the catalytic converter and relief valves in the 
housing of the catalytic converter itself. However, such valves do not 
typically react quickly enough to prevent damage to the catalytic cell. 
Improvements are needed. 
SUMMARY OF THE PRESENT INVENTION 
The present invention provides apparatus for controlling emissions from an 
internal combustion engine to reduce noxious gas emissions and to reduce 
noise therefrom. The apparatus includes an enclosed cylindrical housing 
having an inlet at one end thereof for connection with the exhaust of an 
internal combustion engine and an outlet at the opposite end thereof 
through which the exhaust gases may be discharged to the atmosphere. Both 
noise reduction means and noxious gas converter means may be disposed in 
the housing. 
The converter means, coaxially mounted in the housing, is characterized by 
a catalytic module the center of which is formed by a cylindrical hub 
closed against flow of exhaust gases therethrough and which is surrounded 
by a catalytic cell of annular cross section the inner diameter of which 
is substantially the same as the outer diameter of the hub and the outer 
diameter of which is substantially the same as the inner diameter of the 
cylindrical housing. Exhaust gases from the engine flow from the housing 
inlet through the catalytic cell, where the nitrogen oxides, carbon 
monoxides and unburned carbons thereof are converted to less noxious 
compounds before being discharged through the outlet. By preventing flow 
through the center of the catalytic module and redistributing flow to the 
larger diameter catalytic cell of annular cross section, exhaust gases 
through the catalytic cell are more evenly distributed and the velocity 
thereof is reduced, increasing the residence time and efficiency of 
conversion in the catalytic cell. 
The hub at the center of the catalytic module is normally closed against 
flow of exhaust gases by a closure member. However the closure member is 
operable in response to abnormal increases in pressure from the engine 
exhaust (such as occurs with backfire) to prevent damage to the catalytic 
cell. In a preferred embodiment, the closure member includes a replaceable 
rupture disk. In another preferred embodiment the closure member comprises 
a circular member the outer edges of which are seated against an annular 
seating surface by biasing means, the circular member being moveable away 
from the seating surface in response to abnormal increases in pressure 
from the engine exhaust. Thus protection is provided against destruction 
of the catalytic cell by back fires or other unusual pressure increases. 
In preferred embodiments of the invention, the housing is divided by first 
and second partitions into three chambers: an inlet chamber, a converter 
chamber in which the catalytic cell is disposed and an outlet chamber. 
Each of the partitions is provided with a plurality of ports around the 
outer portions thereof providing for flow of exhaust gases from the inlet, 
through the inlet chamber, through the converter chamber and through the 
outlet chamber, prior to discharge through the outlet. Tubular members of 
various sizes and dispositions may be provided within the inlet and outlet 
chambers to reduce pulsation and noise emitted from the engine exhaust. 
Thus, the present invention provides for reduction of noxious gases and, in 
preferred embodiments, reduction of noise, in a unique combination 
especially characterized by better distribution of exhaust gas flow 
through the catalytic converter portion thereof. It also greatly reduces 
the risk of damage from engine backfire or other abnormal increases in 
pressure. The combination provided by the emission control apparatus of 
the present invention is one which takes advantages of chemical, dynamic 
fluid flow and acoustic principals in a combination which results in 
superior reduction of noise and air pollution. Many other objects and 
advantages of the invention will be apparent from the description which 
follows in conjunction with the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring first to FIGS. 1 and 2, there is shown combination noise and 
pollution control apparatus which includes a cylindrical housing 1 closed 
at opposite ends by dished or semispherical heads 2 and 3. The head 2 is 
provided with an inlet 4 surrounding which is a flange 5 by which the 
apparatus may be connected to the exhaust (not shown) of an internal 
combustion engine (not shown). The opposite head 3 is provided with an 
outlet 6 surrounding which is a flange 7. The flange 7 may be connected to 
a discharge pipe (not shown) for discharge into the atmosphere or for 
additional handling. 
Actually the cylindrical housing 1 may be divided by first and second 
partitions 8 and 9 into three chambers: an inlet chamber 10, a converter 
chamber 11 and an outlet chamber 12. The partitions 8 and 9 may be 
conveniently formed of pressure vessel heads, similar to the heads 2 and 3 
of the housing 1 welded in place within the housing 1. Since the exhaust 
gases and pressures created thereby flow from the inlet 4 toward the 
outlet 6, it is preferable that the convex side of the heads 8 and 9 face 
upstream. 
In the preferred embodiment of FIG. 1, a central tubular member 14 extends 
from the inlet 4 into the inlet chamber 10 providing for flow of exhaust 
gases from the inlet 4 into the inlet chamber. Actually, the inlet 4 may 
be formed by one end of the tubular member 14. The walls of the central 
tubular member 14 may also be provided with perforations 15 which allow 
some of the exhaust gases to enter or exit the central tubular member 
therethrough. The diameter and length of the central tubular member 14 and 
the size and number of perforations 15 provided therein are selected to 
provide optimum pulsation and noise reduction and uniform flow 
distribution of the exhaust gases through the inlet chamber 10. 
Another central tubular member 16 extends from the outlet 6 into the outlet 
chamber 12 and provides for flow of exhaust gases from the outlet chamber 
12 for discharge through the outlet 6. The outlet 6 may actually be formed 
from a portion of the central tubular member 16. The tubular member 16 may 
also be provided with perforations 17 which allow some of the exhaust 
gases to enter or exit the central tubular member 16 therethrough. Like 
the central tubular member 14, central tubular member 16 and its 
perforation 17 are also selected of diameters, lengths and sizes primarily 
for effecting pulsation and noise reduction in the apparatus. 
A plurality of ports 20, 21, etc. (two, three or more) are radially 
disposed around the outer portions of partition 8 a plurality of tubular 
members 22, 23, etc., each one of which extends into the inlet chamber 10 
from one of the ports 20, 21 providing for the flow of exhaust gases 
passing from the inlet chamber 10 into the converter chamber 11. Thus, the 
centralized flow from the inlet 4 is redistributed to peripheral flow into 
the converter chamber 11. The walls of the tubular members 22, 23 may also 
be provided with perforations 24, 25, etc. allowing some of the exhaust 
gases to enter or exit the tubular members 22, 23, etc. therethrough. 
The partition 9 may also be provided with a plurality of ports 30, 31, etc. 
around the outer portions thereof providing for flow of exhaust gases from 
the converter chamber 11 into the outlet chamber 12 prior to discharge 
through the outlet 6. A plurality of tubular members 32, 33 each one of 
which extends into the outlet chamber 12 from one of the ports 30, 31, 
etc. help direct the flow of exhaust gases from the converter chamber 11 
into the outlet chamber 13. The walls of these tubular members 32, 33 may 
also be provided with perforations 34, 35, etc. which allow some of the 
exhaust gases to enter or exit the tubular members 32, 33 therethrough. 
The diameter and length of the tubular members 32 and 33 and the number 
and size of the perforations 34 and 35 are selected primarily for optimal 
pulsation and noise reduction characteristics. 
Coaxially mounted in the converter chamber 11 is a catalytic converter 
module 50, more fully described hereafter, which converts nitrogen oxides, 
carbon monoxide and unburned hydrocarbons from engine exhaust gases 
entering the housing 1 through the inlet 4 to less noxious compounds 
before being discharged through the outlet 6. The catalytic converter 
module 50 is supported or enclosed in a cylindrical outer shell or housing 
51 of relatively short axial length. The catalytic module 50 is supported 
upstream and downstream between inwardly directed radial flanges of 
support rings 52 and 53 welded or otherwise affixed within the converter 
chamber 11 of the housing 1. The cylindrical housing 1 may be provided 
with a side opening through which the catalytic module 50 may be removed 
for repair or replacement thereof. In the embodiment of FIGS. 1 and 2, the 
side opening is provided by an elongated housing 55 transversely disposed 
relative to the cylindrical housing 1 and providing an elongated opening 
which is normally closed by a removable closure member 56. The closure 
member 56 may be attached to a corresponding flange 57 surrounding the 
elongated opening of the housing 55 by nuts and bolts, clamps or any other 
suitable fastening means (not shown). When the closure member 56 is 
removed, the length of the elongated opening, which is perpendicular to 
the axis of the cylindrical housing 1, is substantially equal to the 
diameter of the housing and the width of the opening is at least as great 
as the axial length or depth of the catalytic module 50. 
Referring now to FIGS. 3 and 4, a preferred embodiment of the catalytic 
module 50 will be described. As previously stated, the module 50 may be 
outwardly defined by a cylindrical housing 51 at opposite ends of which 
are outer support rings 60, 61. The center of the catalytic module is 
formed of a cylindrical hub 63 at the opposite ends of which are support 
rings 64 and 65. The support rings may be mutually and coaxially supported 
by radial support members 66, 67, 68, 69 at the upstream face of the 
catalytic module 50. Similar radial supports 66A, 67A, 68A, 69A may be 
provided for mutual and coaxial support of rings 65 and 61 on the 
downstream face of the catalyst module. Handles 58 and 59 may be attached 
to the housing 51 for handling the catalytic module 50 and for lifting it 
in or out of the side opening provided by the housing 55. Surrounding the 
hub 63 and confined between the exterior of the hub 63 and the interior of 
the cylindrical housing 51 is a catalytic cell of annual cross section 
made up of a honeycomb like structure of two-way or three-way catalytic 
materials which convert nitrogen oxides, carbon monoxide and unburned 
hydrocarbons passing therethrough to less noxious compounds. The upstream 
and downstream faces of the catalytic module, in the annular cross 
sectional area of the catalytic cell 70, are substantially unobstructed 
allowing even flow of exhaust gases therethrough. 
The cylindrical hub 63 which forms the center of the catalytic module 50 is 
normally closed against flow of exhaust gases therethrough by a closure 
member. In the embodiments of FIGS. 3 and 4, the closure member comprises 
a replaceable rupture disk 71 coaxially and transversely disposed within 
the cylindrical hub 63. The peripheral edges of the rupture disk 71 are 
sandwiched between a pair of annular flange members, the first 72 of which 
is affixed to the hub 63 and the second 73 of which is removably attached 
by fastening means to the first flange member 72 to allow replacement 
thereof. The fastening means illustrated in FIGS. 3 and 4 comprises a 
plurality of cooperating bolts and nuts 74, 75, the bolt heads of which 
may be disposed in recesses provided in the flange 72. One can readily 
understand that if pressure in the upstream portion of the converter 
chamber 11 reaches the rupture point of the rupture disk 71, the disk 71 
will rupture, allowing flow of exhaust gases through the flanges 72 and 73 
to relieve pressure within the housing 1 and specifically within the 
converter chamber 11 thus preventing rupture or destruction of the 
catalytic cell 70 surrounding the hub 63. 
FIGS. 5 and 6 illustrate a catalytic module 50A which is another preferred 
embodiment of the invention. The catalytic module 50A is similar in many 
respects to the catalytic module 50 of FIGS. 3 and 4 and similar or like 
parts thereof will be referred to by the same reference numbers. The 
catalytic module 50A comprises an outer cylindrical housing 51 and a 
central hub 63 between which is disposed or confined catalytic cell 70 of 
annular cross section. Support rings 60, 61, 64, 65 and support members 
66, 67, 68, 69, 66A, 67A, 68A, 69A support all these components in the 
same manner as in the embodiment of FIGS. 3 and 4. 
In the embodiment of FIGS. 5 and 6, the cylindrical hub 63 is also normally 
closed against flow of exhaust gases by a closure member. However, in this 
embodiment, the closure member comprises a circular plate 80 transversely 
and coaxially disposed within the cylindrical hub 63 and the outer edges 
of which are seated against an annular seating surface provided by flange 
like member 81 affixed to the hub 63. The outer edges of the circular 
closure member 80 are provided with a plurality of holes slidingly engaged 
by a plurality of stud members 82, 83, etc. which are threadedly connected 
to the flange member 81 for guiding the closure member 80 away from the 
seating surface if a substantial force of pre-determined pressure is 
exceeded in the upstream portion of the converter chamber 11. However, the 
stud members are provided with surrounding spring members 84, 85 which 
bias the closure member 80 toward engagement with the seating surface 
provided by the flange member 81, normally closing the cylindrical hub 63 
to the passage of exhaust gases therethrough. If the pressure within the 
upstream portion of the converter chamber reaches a predetermined level, 
the closure member 80 compresses the springs 84 and 85, opening passage 
through the hub 63 and allowing the relief of pressure therethrough. 
Thus, the emission control apparatus of the present invention provides a 
unique catalytic converter in which the catalytic cell is annular in 
cross-section and surrounds a normally closed hub so that exhaust gases 
passing through the apparatus are more evenly distributed and flow at 
reduced velocities therethrough. This results in increased converter 
residence time, increased life of catalyst and greater efficiency in 
reducing noxious exhaust gases to less noxious gases for discharge to the 
atmosphere. 
The central hub is normally closed by a closure member but which is 
operable in response to increased pressures, such as during engine 
backfires, to open a passage through the hub providing pressure relief and 
preventing damage to the catalytic converter. This avoids having to 
replace a partially depleted catalytic module with a new one. 
The emission control apparatus of the present invention also provides, in a 
unique combination, noise reduction components. In preferred embodiments 
the apparatus comprises a cylindrical housing divided into three chambers: 
inlet, converter and outlet chambers. The inlet and outlet chambers are 
preferably provided with perforated tubular members of various sizes and 
dispositions designed to evenly distribute exhaust gas flow and to reduce 
noise produced by the internal combustion engine. 
Although unique and complex in utilizing chemical, fluid flow and 
acoustical principles, the apparatus is relatively simple in construction 
and operation. Most importantly it is extremely efficient and cost 
effective in reducing noise and air pollution from internal combustion 
engines. 
Although several embodiments of the invention are described herein, many 
variations will be apparent to those skilled in the art. Accordingly, it 
is intended that the scope of the invention be limited only by the claims 
which follow.