[0001] The present invention relates generally to methods and apparatus for removal of particulate
from engine exhaust and more particularly to improved particulate filter systems,
controls therefore, and a method of operating
BACKGROUND OF THE INVENTION
[0002] The Environmental Protection Agency (EPA) has issued increasingly stringent standards
for particulate and NOx emissions. For example, the standards in place in October,
2002 include 0. 1 g/hp-hr for particulates and 2.0 g/hp-hr for NOx. In 2007 these
will be further reduced to 0.01 g/hp-hr for particulates and 0.2 g/hp-hr for NOx.
Industry has intensive programs aimed at achieving these requirements.
[0003] U. S. Patent Application Serial No. 10/846,780, now Patent No.
, discloses a method and apparatus for filtering or trapping particulate from engine
exhaust and periodically disposing of the collected soot and ash. The system uses
a monolithic ceramic trap having passages with porous walls through which the exhaust
is passed to filter out the particles at very high (90-97%) trapping efficiency. The
systems use wall-flow traps in single or multi-trap configurations. Each of these
systems can be used with any diesel engine and is capable of achieving the EPA particulate
standards for the foreseeable future. Engine manufacturers can concentrate on achieving
the very challenging NOx standards without concern for particulate emissions control.
The particulate trap system can also be used for retrofit applications.
[0004] The wall-flow particulate trap systems use cordierite traps, such as Corning EX-80
or RC-200, to filter the exhaust gas by passing it through the porous walls of trap
channels. This action removes 90-98% of the particulate and this collects on the inside
surfaces of the passages as a layer or cake which after a few hours of operation increases
the engine backpressure and must be removed to prevent adverse affect on engine performance.
Most prior art trap systems remove this layer by burning the particulate or soot in
the trap. To avoid excessive temperatures during this operation, expensive noble metal
catalytic coatings are required and ultra low sulfur fuel must be used which will
not be broadly available for a number of years. Also, the engines must be operated
at a relatively high average load factor to assure that burn-out occurs before too
much soot is collected. To assure that light-off temperatures are reached heaters
such as burners or late injection coupled with catalysts are increasingly employed.
Finally, the incombustible ash builds up and the traps and must then be cleaned in
an expensive and disruptive maintenance operation. It is desirable to overcome one
or more of these problems.
OBJECTS AND ADVANTAGES
[0005] Accordingly, objects of the present invention include one or more of the following:
- 1. Provide apparatus for using an instantaneously applied reverse pressure drop pulse
of previously filtered exhaust gas for effective dislodging and removal of the soot/ash
cake in a single trap or multi-trap particulate trap systems.
- 2. Provide apparatus for utilization of very high reverse pressure drops such as those
used with diesel engine exhaust brakes (25 - 60psig) without loss of component life
or reliability.
- 3. Provide apparatus and controls for a single trap system in which a duct/rotor is
stationary when the relatively high reverse pressure drop occurs and the pressure
induced force of the duct/rotor against the trap face is high; and in which the duct/rotor
is rotated when there is substantially zero reverse pressure and thus no pressure
induced forces to assure negligible wear of the rotor and trap faces.
- 4. Provide apparatus and controls for a single trap systems in which the reverse pressure
is provided by actuating a relief valve, a duct/rotor aligns with a group of contaminated
passages; and in which the substantially constant pressure reverse pressure is almost
instantly applied by a small two-position mode valve as one or more pulses which will
more effectively dislodge the soot cake than steady state reverse flow pressure drop.
- 5. Provide for regeneration of a multi-trap particulate trap system in which the system
used for single trap system is duplicated to provide filtration capacity for larger
vehicle and industrial engines. The regeneration may be carried out simultaneously
in each of the traps to reduce the time the increased reverse pressure must be maintained
in order to minimize any adverse affect on engine efficiency and power output. The
actual reverse flow pulses may sequentially occur in the group of traps to provide
a relatively constant purge flow rate to the separation chamber to enhance separation
and combustion of the soot particles.
- 6. Provide control systems for carrying out regeneration that are simple and inexpensive
and which are independent of the engine or its controls.
- 7. Provide control systems which in whole, or in part, obtain the reverse pressure
across the porous walls of the trap from the high backpressure utilized in diesel
exhaust brake systems and using a commercially available exhaust brake installed downstream
of the particulate trap.
- 8. Provide control systems which in whole, or in part, obtain the reverse pressure
across the porous walls of the trap from the backpressure that results when a relief
valve is actuated downstream from the trap when the engine is operating at low idle.
SUMMARY OF THE INVENTION
[0006] In accordance with the present invention there is provided a particulate trap system
for an exhaust system of an internal combustion engine and including a monolithic
wall-flow particulate trap having a plurality of contiguous porous walls, a remotely
actuated relief valve downstream of said trap for periodically creating a reverse
pressure throughout the exhaust system upstream of the relief valve and including
said trap, a reversing apparatus for periodically creating a reverse pressure drop
across a portion of the contiguous porous walls of said trap to dislodge accumulated
particulate and cause a portion of the filtered exhaust gas to flow back through said
portion of the contiguous porous walls to remove particulate therefrom, and controls
for actuating the relief valve and the reversing apparatus.
[0007] The reversing apparatus includes an indexing mechanism upstream of said trap to periodically
change the said portion of the porous walls receiving the back flow of filtered exhaust
gas so that the entire trap is systematically cleaned.
[0008] Advantageously, wall-flow single trap and multi-trap technology is used to reduce
particulate emissions. The particulate trap system can be located almost anywhere
in the exhaust system and is substantially independent of the engine and its controls.
[0009] In accordance with another aspect of the present invention there is provided a method
of regenerating a wall-flow particulate trap having a plurality of contiguous porous
walls for filtering particulate from an exhaust system of an internal combustion engine,
the method including the steps of: creating a backpressure in the entire exhaust system
from a location downstream of the trap; creating a reverse pressure drop across only
a portion of the porous walls to dislodge accumulated particulate therefrom; and causing
a portion of filtered exhaust gas to flow back through said portion of the porous
walls to carry the dislodged particulate out of the trap.
[0010] Other aspects of the present invention include alternative regeneration strategies
and associated control systems to effectively dislodge and remove the soot/ash deposits
from the passages of single trap and multi-trap particulate trap systems during regeneration.
The improvements relate to the manner in which the components operate and/or interact
with each other. In addition, some of the improvements interact with, or provide,
diesel exhaust brakes that are increasingly popular for larger vehicles such as trucks
and motor homes. These alternative strategies assure effective regeneration and improved
durability and reliability of the particulate trap systems and are adaptable to a
broad range of industrial engines and vehicles such as automobiles, trucks, and buses.
[0011] The particulate trap systems avoid the necessity of using high pressure air, used
by some companies, by using a reverse flow of filtered exhaust gas to create a pulse-induced
reverse pressure drop across the trap of sufficient magnitude and duration to dislodge
and erode the accumulated soot and ash cake and to transport the dislodged particles
to an external chamber for suitable disposal. When the reverse pressure is permitted
to exist across only a smaller number of the passages at a given time, only these
passages will have their soot dislodged and removed and the resultant reverse flow
rate at a given time will be much less.
[0012] These and other objects and advantages will become apparent as the same become better
understood from the following detailed description when taken in conjunction with
the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
FIG. 1 illustrates a wall-flow single trap according to U.S. Patent Application Serial No. 10/845,780, now Patent No. , during normal filtration.
FIG. 2 shows the FIG. 1 configuration during regeneration.
FIG. 2A is a cross-section taken generally along line A-A of FIG. 1 or FIG. 2.
FIGS. 3A-C illustrate a remotely actuated relief valve for use with any of the particulate
trap systems.
FIG. 4 illustrates a ratchet drive for rotating the duct rotor.
FIG. 5 is a diagrammatic view illustrating an apparatus embodying the present invention
during normal filtration.
FIG. 6 illustrates Fig. 5 apparatus in a regeneration position.
FIG. 7 shows a portion of the FIG. 1 apparatus in phase 1 of a regeneration process.
FIG. 7A is a cross-section taken generally along line B-B of FIG. 7.
FIG. 7B is a sectional view taken along line C-C of FIG. 7A.
FIG. 8 is a view similar to FIG. 7 but illustrating phase 2 of the regeneration process.
FIG. 8A is a cross-section taken generally along line D-D of FIG. 8.
FIG. 8B is a sectional view taken along line E-E of FIG. 6A.
FIG. 9 is a graph of pressure vs. time events which take place during phases 1 and
2 of the regeneration process.
FIG. 10 is a longitudinal sectional view showing a particulate trap system utilizing
a D-celerator® diesel exhaust brake valve for the remotely actuated relief valve and
a spiral burner.
FIG. 11 is a schematic drawing illustrating a control used with a single particulate
trap system for regeneration after an elapsed time period.
FIG. 11A is a diagrammatic view showing significant events that occur during operation
of the particulate trap system controlled by the FIG. 11 control.
FIG. 12 is a schematic drawing illustrating a control used with a single particulate
trap system in which regeneration occurs after reaching a designated trap pressure
drop.
FIG. 12A is a diagrammatic view showing tsignificant events that occur during operation
of the particulate trap system controlled by the FIG. 12 control.
FIG. 13 is a schematic drawing illustrating a control used with a single particulate
trap system in which regeneration begins after reaching a designated trap pressure
drop and is effected by the increased pressure resulting from closing the relief valve
during diesel engine operation at low idle.
FIG. 13A is a diagrammatic view showing significant events that occur during operation
of the particulate trap system that regenerates during engine low idle operation and
is controlled by the FIG. 13 control.
Fig. 14 is a schematic drawing illustrating a control used with a single particulate
trap system in which regeneration begins after reaching a designated trap pressure
drop and is effected by the increased pressure at the trap exit during diesel exhaust
brake application.
Fig. 14A is a diagrammatic view showing significant events that occur during operation
of the particulate trap system having a diesel exhaust brake and controlled by the
Fig. 14 control.
Fig. 15 is a sectional view illustrating a multi-trap particulate trap system used
for larger engines in which the single trap system is substantially duplicated.
Fig. 16 is a schematic drawing illustrating a control used with a multi-trap system
that is regenerated after an elapsed time period.
Fig. 16A is a diagrammatic view showing significant events that occur during operation
of the particulate trap system controlled by the Fig. 16 control.
FIG. 17 is a schematic drawing illustrating a control used with the multi-trap system
in which regeneration occurs after reaching a designated trap pressure drop.
FIG. 17A is a diagrammatic view shows significant events that occur during operation
of the particulate trap system controlled by the FIG. 17 control.
FIG. 18 is a cross-section of a secondary timer usable with any of the above single
trap or multi-trap systems.
FIG. 19 is a cross-section of a rig used to load traps for testing.
FIG. 20 is a cross-section of a rig used for evaluating regeneration at various reverse
pressures.
FIG. 21 is a table showing the 35 psi regeneration test data.
FIG. 22 is a graph of the particulate trap regeneration test results at 35 psi reverse
pressure with a loaded Corning DuraTrap™ 200/12.
FIG. 23 is a table showing the 20 psi regeneration test data.
FIG. 24 is a graph of the particulate trap regeneration test results at 20 psi reverse
pressure with a loaded Corning DuraTrap™ 100/17.
DETAILED DESCRIPTION OF THE INVENTION
[0014] In this Description all values are approximate and the values may vary as a result
of product configuration, usage, and requirements.
[0015] FIGS. 1 and 2 show the salient features of a particulate trap system with which various
improvements are utilized. The principal parts are a monolithic wall-flow trap 20,
a duct rotor 24, a duct rotor ratchet actuator 40, a mode valve assembly 32, a remotely
actuated relief valve 38, and a cyclone separator 44, with its attached igniter 46
and ash storage chamber 48. The mode valve assembly 32 includes a purge duct 28, a
two-position valve 34, and a mode valve actuator 36. The duct rotor 24 includes a
duct section 27 and a ring gear 29, and is mounted loosely on a pilot bearing 26 which
keeps the duct rotor centered. The duct rotor 24 is pressed against the face of the
trap 20 by a spring/seal 30, with just enough force to preclude the duct rotor from
moving off the face of the trap due to inertia or gas loading. The contact between
the duct rotor and the trap is shown by footprint 23, indicated in FIG. 2A. The footprint
23, results in a reverse flow duct section 22, and a continuous ring of contact between
the duct rotor and the trap. The enclosed area of the reverse flow duct section 22,
of the duct rotor/trap footprint is only about 4-6% of the total area of the trap
entrance face. The faces of the duct rotor 24, and the trap 20, that contact each
other are ground very flat and smooth to permit relative movement with negligible
wear.
[0016] In normal filtration operation, shown in FIG. 1, the remote actuated relief valve
38, is wide open and pressure P2 is substantially ambient. Engine exhaust enters the
large majority of the trap passages and, because the mode valve 36 is not energized,
exhaust flows past the mode valve 34 and enters the reverse flow duct section 22.
[0017] As shown in FIG. 2, when the trap is loaded (i.e. has a particulate cake) and regeneration
is desired, the igniter coil 46 is energized. After a brief period for the igniter
coil to reach a desired temperature, the remote actuated relief valve 38 is actuated
and pressure P2 is raised to a substantially constant pressure sufficient to dislodge
the particulate cake. Then the mode valve actuator 36, is energized to move the mode
valve 34 to the position shown. This prevents further exhaust flow into the reverse
flow duct and, at the same time, opens the reverse flow duct 22, to ambient pressure.
This action results in a reverse pressure drop across the porous walls throughout
the length of the smaller number of trap passages encompassed by the reverse flow
duct 22, and results in the soot/ash cake being dislodged from the entire inner surface
of the affected passages and transported to the cyclone separator 44, which removes
the soot from the purge flow to be ignited and burned by the igniter coil 46. The
incombustible ash is collected in the ash storage chamber 48 for periodic disposal.
Because in this earlier version the duct rotor is substantially continuously rotating,
the reverse flow duct section 22, of the rotor will move to provide reverse pressure
drop across additional passages and, at the same time, return cleaned passages to
normal filter operation.
[0018] FIG. 3 illustrates an electromechanical remotely actuated relief valve which includes
two hemispherical butterfly valves 50 that are closed in response to an electrical
input to an actuator 52. Upon closing, the pressure immediately builds up and impose
a force against the butterfly valves 50. When the pressure reaches the desired level,
the force will act through linkages 54, and overcome a low rate spring 56 that is
pre-loaded between slip link 57 and an actuator plunger 58. The butterfly valves will
open as required to maintain the desired pressure regardless of the engine speed and
load. A relief valve of this type can be used in the various particulate trap systems.
[0019] FIG. 4 illustrates a ratchet drive having springs 60, 62 with integral pawls that
engage teeth 64 in ring gear 29, and are used for actuation. The springs are made
from a material that will retain its mechanical properties under all anticipated temperatures
that the trap system will encounter. Use of a ratchet mechanism of this type for the
rotor drive has important advantages such as freedom for the duct rotor to expand
and contract due to changes in exhaust temperature without affecting the ratchet action.
An important advantage is that the ratchet actuation is effected by digital pulses
of electricity. Consequently, the duct rotor rotation can occur or be stopped at will.
In addition, the digital nature of the ratchet actuation simplifies the control device
that is used to provide the desired regeneration strategy. Also, no changes need to
be made to the ratchet actuation device for various single and multi-trap particulate
trap configurations.
[0020] FIG. 5 schematically illustrates the particulate trap regeneration principle during
normal filtration. The monolithic wall-flow particulate trap 20 has a plurality of
porous walls 20W which are contiguous to each other. It will be noted that of the
trap passages (a portion of which are shown enlarged in FIG. 5), only about five percent
are regenerated at a given time and exhaust gas continues to pass through the remaining
ninety five percent of the trap passages where it is filtered and continues to pass
through the remote actuated relief valve (not shown in this view). Because the three-way
mode valve is in the position shown, five percent of the exhaust gas enters the selected
passages in which it is filtered and then mixes with the exhaust passing through the
relief valve. During normal filtration, the remote actuated relief valve is open and
P2 is at ambient pressure. During normal filtration, the duct rotor is moved to select
a new group of passages to prevent it from becoming stuck by particulate. However,
the events continue as described above.
[0021] When regeneration is initiated, the pressure at the trap exit is increased by actuating
a relief valve 38 or 76 set, for example, at 35 psig. This will raise the pressure
in the entire exhaust system upstream of the relief valve, including in all of the
passages in the trap 20 including the selected group. However, with the mode valve
32 closed as shown, the flow continues as before through the selected passages. The
pressures in the passages have been labeled P1 for the inlet passages and P2 for the
exit passages of the group. During this period the pressures P1 and P2 are nearly
equal. This is Phase 1 of the regeneration process as will be discussed more fully
later.
[0022] FIG. 6 shows the particulate trap principle during Phase 2 of the regeneration process.
The mode valve has been changed to the open position, thus connecting the inlet passages
to the purge duct which is at ambient pressure and, by the same action, precluding
exhaust from entering the inlet passages. Therefore, the pressure in all of the inlet
passages in the selected group shown as P3 almost instantly drops to ambient. It is
theorized that a depression wave occurs in the inlet passages of the selected group.
However, the pressure in all of the exit passages shown as P2 remains at the high
35 psig pressure. Thus, almost instantly a reverse pressure of 35 psi is imposed across
the porous walls of the selected group of passages. This reverse pressure dislodges
the particulate cake from the inlet passage walls and the resultant flow carries these
particles out through the purge duct. The way the Phases of this process are carried
out and controlled will become more clear later in the Specification. As used herein
the term "dislodge" is intended to mean any sudden removal of or breaking away of
the cake and/or an erosion thereof
[0023] FIG. 7 shows more detail of phase 1 of the regeneration process during normal filtration.
The FIG. 5 design is somewhat different from the FIG. 1 design and different reference
numerals have been provided for similar parts. As can be seen by the arrows, most
of the exhaust from the engine passes directly through the trap to be filtered. However,
because the mode valve 34 is closed, about 5% of the exhaust enters the purge duct
and enters a small group of trap passages from the reverse flow duct 70. This exhaust
is also filtered and then joins the majority of the filtered exhaust gas and then
passes through the remote actuated relief valve (shown at 38 in FIG.1) and thence
to the atmosphere. It will be noted that with the mode valve 34 closed, as shown,
pressure P1 will equal pressure P3 in a reverse flow duct 70. Therefore, during normal
filtration no pressure difference exists across the walls of the reverse flow duct
70, and there is no pressure induced force tending to push the duct rotor against
the trap. The only force of the rotor against the trap face is the light spring/seal
30 which is used as a seal and to keep duct rotor in contact with the trap face.
[0024] FIG. 8 shows more detail of phase 2 of the regeneration process during the regeneration
step. As can be seen, the mode valve 34, has been actuated upwardly and is seated
in the upper position. This prevents the flow of exhaust into the reverse flow duct
70. At the same instant, the mode valve 34 opens the reverse flow duct 70 to ambient
pressure. This causes the pressure in the reverse flow duct to also drop to ambient.
This drop in pressure results in a depression wave passing through the contaminated
passages causing an almost instantaneous pressure drop across the porous trap passage
walls as a pulse. This sharp application of the pulse is effective in dislodging the
particulate cake. Also, this drop in pressure P3 in the reverse flow duct 70 causes
a pressure difference between P1 and P3. If the relief valve (e.g. 38 in FIG.1) is
set at a high pressure, there will be a similarly high force created by the pressure
differential between P1 and P3 acting across the area encompassed by the reverse flow
duct. Although the area encompassed by the reverse flow duct 70 is only about 5% of
the trap face area, this force will be about 200 pounds if the relief valve is set
at 35 psig in a 12" diameter trap. Consequently, it is desirable to have the duct
rotor 68 remain stationary while the regeneration step is carried out. It should be
noted that the force of the rotor against the trap face is countered by the force
in the opposite direction that results from the pressure drop across the passages
being cleaned. Therefore, there is no force trying to move the trap 20. In view of
the above, the control will cause the ratchet 42 to stop and hold the duct rotor 68
stationary during the very brief period of the regeneration pulse
[0025] When the phase 2 regeneration step ends, the mode valve 34 again closes, returning
the regeneration process to phase 1. This, as noted in connection with FIG. 5, causes
the pressure P3 in the reverse flow duct 70 to equal the pressure P1 at the trap entrance.
This removes all pressure induced force pushing the duct rotor 68 against the face
of trap 20, leaving only the light force of spring seal 30. At this time, a control
(hereafter described in detail) causes the ratchet 42 to rotate the duct rotor 68
to the next group of contaminated passages.
[0026] FIG. 9 shows the pressure vs. time curves for each of the above discussed phases
of the regeneration process. It will be noted that the sequencing of actuation of
mode valve 34 and movement of ratchet 42 to rotate the duct rotor 68, is carried out
by a simple secondary timer (hereinafter described) which rotates at a constant speed
of about 1 revolution per each 10 seconds. Since there are about 40 groups of contaminated
passages to be cleaned and only one group is cleaned per revolution of the secondary
timer, the entire trap will be cleaned in 400 seconds or about 7 minutes. Other embodiments
can be cleaned even faster, even under 2 minutes. Secondary timers of this general
type are usable in all trap systems described herein.
[0027] FIG. 10 shows the particulate trap system from FIG. 6 to which a D-Celerator® diesel
exhaust brake 76 marketed by United States Gear Corp. has been installed for use as
the remote actuated relief valve 34. This exhaust brake 76 is electrically actuated
and is available in various sizes. It has been developed to provide pressures from
23 to 60 psi for diesel engine braking. However, when regeneration is carried out
in concert with exhaust braking, the use of 35 psig is preferred because the published
literature states that this lower pressure is safe for all diesel engines without
modification. This pressure exceeds the reverse pressure required for regeneration
under all conditions that might be expected in service. As has been discussed, the
system can operate with these high reverse pressure drops while maintaining negligible
wear of the rotor 68 and trap 20 against which it is engaged. However, unless used
as an exhaust brake in the various embodiments, the D-Celerator® is adjusted to provide
only enough pressure to assure adequate regeneration.
[0028] Also shown in FIG. 10 is a spiral burner 78 which is considered a preferred embodiment
for separating and burning the soot. Because the average flow rate of the purge flow
is quite small, the entire purge flow with its entrained soot particles can be passed
through the spiral burner 78. The spiral burner has a very high temperature nickel/
chrome igniter element wound around its periphery. The soot particles are moved outwardly
by centrifugal force as they spin through the spiral burner and are ignited and burned
on contact. The incombustible ash is so minute for each regeneration that it is believed
the ash can simply be carried out with the exhaust without adverse effects to the
environment.
[0029] For ease of understanding, the following control systems are described using electro-mechanical
components. While these will perform satisfactorily, it should be understood that
many or all of the control components may be computerized and/or executed using solid
state technology.
[0030] FIGS. 11 and 11A illustrate a control system used for the single trap particulate
trap system in which regeneration is initiated after a fixed time of engine operation.
The fixed time period is selected to assure that the trap will not exceed a safe loading
of six grams per liter. However, it should be long enough for a reasonable particulate
cake to accumulate in the passages of the trap 20. The cake provides more effective
filtering and is amenable to dislodging during regeneration. In periods of normal
operation when the particulate trap is filtering the exhaust, electrical power enters
the control and passes through a circuit leading to a pulse generator 80. Between
regeneration periods a single pole double throw (SPDT) relay 81 is closed and the
pulse generator 80 sends pulses of electricity every few minutes to the duct rotor
ratchet drive actuator 42. When the relay 81 is in this postion, the pulse generator
is disconnected from the secondary timer 88 to isolate the secondary timer 88 and
its circuitry from the periodic pulses of electrical energy. The action of the pulse
generator keeps the duct rotor from becoming stuck due to particulate deposits. In
addition, power is constantly supplied via line 83 to a main timer 82 which runs all
of the time that the engine is in operation. After the engine has operated for say,
two hours, the igniter contact 84 closes and energizes the igniter element of spiral
burner 78. After about three minutes to allow the igniter element to reach its maximum
temperature, the event circuit contact 86 is closed and the event circuits energized.
Closing the event contact 86 causes SPDT relay 81 to open. This stops the pulse generator
80 from periodically rotating the duct rotor 68 and, at the same time, connects the
secondary timer 88 to the duct rotor ratchet actuator 42. Closing of the event contact
86 also closes the remote actuated relief valve 38 and increases the pressure of the
filtered exhaust gas at the exit of trap 20 to a level that assures reliable regeneration.
Finally, closure of the event contact 86 starts rotation of the secondary timer 88.
As noted in connection with FIG. 7, rotation of the secondary timer causes the ratchet
actuator 42 to rotate the duct rotor 68 (phase 1) and causes mode valve 34 to alternately
open and close to dislodge the particulate (phase 2). As the secondary timer 88 continues
to run, this alternate action occurs until all of the groups of passages in trap 20
have been cleaned. This will require about seven minutes. As noted earlier, the main
timer 82 runs continuously during engine operation. Consequently, after about 10 minutes
to assure all of the passage groups have been cleaned, the main timer 82 opens both
the igniter contact 84 and the event contact 86. At this time, the remote actuated
relief valve 38, secondary timer 88, and igniter in spiral burner 78 are turned off.
In addition, the relay 81 is turned off and its contacts closed to again return the
pulse generator 80 to its task of periodically rotating the duct rotor 68. The particulate
trap system is thus retuned to normal filtration operation for another two hours.
[0031] FIGS. 12 and 12A illustrate a control for the single trap particulate trap system
in which regeneration is initiated after the trap pressure drop has reached a pre-selected
value. As in FIG. 11, the power is directed to the control all of the time that the
engine is operating. During normal filtering operation, power is supplied to a pulse
generator 90, then through a normally closed SPDT relay switch 99, to the ratchet
42. When the relay 99 is in this position, the pulse generator 90 is disconnected
from the secondary timer 98 to isolate the secondary timer 98 and its circuitry from
the periodic pulses of energy. Power is also supplied to a switch 91 which is a time
delay momentary pressure switch that closes when the trap pressure drop reaches a
designated sustained level, e.g. 40 in. W.G., for a pre-selected interval longer than
the normal engine exhaust pulse interval. When this occurs, power is supplied to a
drive line 92a of a main timer 92 which begins to move. After the main timer 92 moves
enough, an igniter contact 94 closes and energizes the igniter element of spiral burner
78. After another few minutes, an event contact 96 closes and energizes the event
circuits. First, relay switch 97 is energized and closed thereby supplying power to
the main timer 92 regardless of the condition of momentary switch 91 and the main
timer continues to run until regeneration is complete. Also, SPDT relay switch 99
is energized and opened, thereby stopping the periodic actuation of the ratchet 42
at the trap and, at the same time, connects the secondary timer 98 to the duct rotor
ratchet actuator 42. Current is also sent to the remote actuated relief valve 38 which
is closed. Finally, power is sent to a secondary timer 98 which provides the power
alternately to ratchet 42 and mode valve 34, thus carrying out the phase 1 and phase
2 steps as discussed in connection with FIG. 7. Following completion of regeneration
of all of the groups of passages, the main timer 92 will have turned enough to open
both the igniter contact 94 and the event contact 96. Because all the associated circuits
are now turned off, the components all return to their normal filtration positions
and the trap 20 returns to the normal filtration operation until the pressure drop
across the trap again actuates the time delay momentary switch 91.
[0032] FIGS. 13 and 13A illustrate a control for a single trap particulate in which regeneration
is carried out when the remote actuated relief valve is actuated while the engine
is operating at low idle. It has been stated by U.S. Gear that the pressure upstream
of their exhaust valve (remote actuated relief valve) under these conditions is 22
psig and can be maintained without causing engine stalling. In this configuration
regeneration is initiated after reaching a designated trap pressure drop. During normal
filtration operation power is supplied to the pulse generator 108, then through a
normally closed SPDT relay switch 110, to the ratchet 42. When relay 110 is in this
position, the pulse generator is disconnected from the secondary timer 118 to isolate
the secondary timer and its circuitry from periodic pulses of electrical energy. Also
power is supplied to a time-delay momentary pressure switch 104, which closes after
the trap inlet pressure reaches a sustained 40 in. W.G., to signal that the trap is
loaded and the regeneration period should begin.
[0033] When the particulate trap pressure drop during normal filtration operation has reached
40 in. W.G., time-delay momentary pressure switch 104 closes and power is sent to
a single pole double throw (SPDT) switch 120 which is spring loaded to the right in
the drawing. This directs power to the main timer drive 112a, causing main 112 to
begin operating. After the main timer 112 has operated for a brief period, igniter
contact 114 closes and the igniter element in the spiral burner 78 is energized. Following
sufficient time for the element to reach its maximum temperature, event circuit contact
116 closes and energizes the event circuit. This action moves the SPDT relay 110 which
opens and temporarily keeps the pulse generator 108 from rotating the duct rotor 24
and, at the same time, connects the secondary timer 118 to duct rotor ratchet drive
42. If the engine is operating at any normal speed above low idle speed, the engine
tachometer will not send a signal to pole single throw (SPST) 125 and it will be spring
loaded to its open position. Under these conditions no electrical energy is sent to
the remote actuated relief valve 38 and it will remain in its open position and the
pressure at the trap exit will be ambient. Thus, momentary pressure switch 122 will
also remain open. Under these conditions there will be no electrical energy transmitted
to the drive circuit 112a of the main timer 112 and the drive circuit 118a of the
secondary timer 118. The system will then remain poised until the driver takes his
foot off of the accelerator and the engine speed drops to low idle.
[0034] When the driver closes the throttle and slows the engine to about 100 rpm above low
idle, the engine tachometer will send an electrical signal to close relay 125. This
will close the remote actuated relief valve 38, which will increase the pressure at
the trap exit 122 which will, in turn, energize the drives for timer 112 and 118a
and the regeneration process will begin. When the operator again accelerates the engine
the increases the engine speed, relay 125 will open removing electrical energy from
the relief valve which will open, the regeneration process will stop, the system will
return to normal filtration and the control will remain poised.
[0035] The above actions continue until all of the trap passages have been cleaned and the
main timer 112 has rotated enough to open contacts 116 and 114 which deenergize the
event circuit and igniter circuits, respectively. The particulate control will return
to normal filtration until trap pressure drop increases enough to activate time-delay
momentary switch 104.
[0036] FIGS. 14 and 14A illustrate a control for the single trap particulate system in which
the regeneration is carried out in concert with diesel exhaust braking. In this configuration
regeneration is initiated after reaching a designated trap pressure drop. During normal
filtration operation power is supplied to the pulse generator 108, then through a
normally closed SPDT relay switch 110, to the ratchet 42. When relay 110 is in this
position, the pulse generator is disconnected from the secondary timer 118 to isolate
the secondary timer and its circuitry from periodic pulses of electrical energy. Also
power is supplied to a time-delay momentary pressure switch 104, which closes after
the trap inlet pressure reaches a sustained 40 in. W.G., to signal that the trap is
loaded and the regeneration process should begin. Because the exhaust brake will apply
a much higher pressure to the exhaust many times during normal filtration operation,
normally-closed relay 106 opens by application of the brake control to prevent false
signals of trap loading from being sent to the time delay momentary pressure switch
104.
[0037] When the particulate trap pressure drop during normal filtration operation has reached
40 in. W.G., time-delay momentary pressure switch 104 closes and power is sent to
a single pole double throw (SPDT) switch 120 which is spring loaded to the right in
the drawing. This directs power to the main timer drive 112a, causing main timer 112
to begin operating. After the main timer 112 has operated for a brief period, igniter
contact 114 closes and the igniter element in the spiral burner 78 is energized. Following
sufficient time for the element to reach its maximum temperature, event circuit contact
116 closes and energizes the event circuit. This action moves the SPDT relay switch
120 to the left in the drawing, disconnecting all power to the main timer112 which
temporarily stops. The event circuit also sends a signal to the SPDT relay 110 which
opens and temporarily keeps the pulse generator 108 from rotating the duct rotor 24
and, at the same time, connects the secondary timer 118 to duct rotor ratchet drive
42. Energizing the event circuit also sends a signal to activate the exhaust brake
control system which de-activates the cruise control and locks out the overdrive.
In the Fig. 8 example, it also places the exhaust brake in the "D-Feat" mode of the
United States Gear D-Celerator® system. In this mode, the exhaust brake 76 is applied
whenever the driver lifts his foot from the accelerator, and the brake is released
whenever the driver again presses the accelerator. Energizing the event circuit also
stops the main timer 112 which remains poised. Advantageously, this action also turns
on a cab signal that notifies the driver that the regeneration period is in progress.
[0038] When the driver's foot is removed from the accelerator to cause the exhaust brake
76 to be applied, a signal is sent to exhaust brake 38 causing it to close. When the
brake pressure builds up to about 20 psig, the momentary pressure switch 122 closes.
Because the event circuit is energized, this action then starts the main timer 112
and, also starts the secondary timer 118 via line 118 a to cause the trap system to
alternate between phase 1 and phase 2 as described in regard to FIG. 7. When the brake
is released, the pressure at the momentary pressure switch 122 drops and thus opens
switch 122 and again the system stops and remains poised. After a cumulative time
of brake applications, the secondary timer 118 will have rotated the duct rotor 24
far enough to have cleaned all of the groups of passages. During this period, the
main timer 112 and the secondary timer 118 rotate at their respective speeds. Thus
after the trap has been cleaned, the igniter contact 114 and the event contact 116
open and all components will return to normal filtration mode. There may be some concern
that the driver of a line haul truck operating on an interstate highway may not lift
his foot to decelerate often enough once the regeneration process is initiated to
prevent the trap from becoming overloaded. The optional safety timer 123 and associated
relays 126 and 128 is identified to begin to run for about one hour. If the trap is
not cleaned and the event circuit deenergized within fifty minutes, the timer 123
will close relay 128 and provide a signal or apply the exhaust brake.
[0039] It should be noted that when the particulate trap system is integrated with an exhaust
brake the increased engine backpressure required for regeneration occurs only during
vehicle deceleration or idle operation. Consequently, the regeneration process has
substantially no adverse affect on engine fuel consumption or the means used to control
NOx or other gaseous emissions.
[0040] FIG. 15 illustrates an approach to provide greater particulate trap capacity with
large industrial engines in various applications. As shown, the single trap system
is duplicated to provide a two trap system. Advantageously, the particulate trap systems
are identical to those used in single trap applications and appropriately sized. These
are ducted together using one remote actuated relief valve 96, and one purge duct
leading to a spiral burner, along with a suitably modified control. Although the preferred
remote actuated relief valve 96, is shown as a United States Gear Corp. D-Celerator®,
it would be adjusted to provide just enough pressure to assure complete regeneration
of the trap passages. It is assumed that few, if any, of the larger engines would
use diesel exhaust brakes. It will apparent to those skilled in the art, that any
of the single trap configurations that were discussed earlier can be executed as multi-trap
configurations by use of the minor changes discussed in conjunction with FIGS. 16
& 17.
[0041] FIGS. 16 and 16A illustrate the control for a multi-trap configuration in which regeneration
is initiated every two hours. This control is similar to the control shown and described
in FIGS. 9 and 9A. The same parts contain the same reference numerals as FIGS. 11
and 11 A. The changes relate to SPDT relay 148, and an arrangement for connecting
the mode valves 34a and 34b, and ratchets 42a and 42b to the secondary timer 150.
The relay 148 contains a pole for each trap and the poles are operated together. There
is little difference in the secondary timer 150 in this system. However, with multiple
traps it is important that only one mode valve 34 is opened at any one time and that
they be opened in sequence for the traps. Similarly, the ratchet 42 is also actuated
for only one trap at a time but 180 degrees out of phase with the mode valves. This
results in a steadier purge flow to and through the spiral burner.
[0042] FIGS. 17 and 17A illustrate a control for a multi-trap configuration in which regeneration
is initiated by reaching a pre-selected pressure drop across the traps. This control
is similar to the control shown and described in FIGS. 12 and 12A for a single trap
and the same parts contain the same reference numerals as in said FIGS. Again, the
only difference between the multi-trap and single trap control is the SPDT relay 174
having a pole for each trap used and the connection of the secondary timer 172 to
mode valves 34a and 34b and to ratchets 42a and 42b. Consequently, no further description
is considered necessary.
[0043] FIG. 18 illustrates a cross section of secondary timer 88, 98, 118, 150 or 172 that
can be used with any of the particulate trap systems. The secondary timer consists
of a rotor 180 which is insulated from the rotor drive motor (not shown) and the housing
182. The rotor can be rotated by energizing drive line 184, as directed by the control.
During the regeneration period the rotor 180 is electrically charged by line 186,
and a slip ring (not shown). The rotor 180 contains an integral contact lobe 188 that
periodically briefly engages a brush or other electrical contact 190 which is also
insulated from the housing 182. Electrical lines are run from the contacts 190 to
the trap mode valves and ratchet actuators described above. When the regeneration
process begins, the rotor drive 184 is energized and the rotor begins to rotate at
about six revolutions per minute. As the timer lobe 188 engages one of the electrical
contacts 190, a trap mode valve or trap ratchet will be actuated in the case of a
single particulate trap system. This action will alternate between ratchet actuation
(phase 1) and mode valve actuation (phase 2) during each half revolution of the rotor
180. In the case of a multi-particulate trap system, as in the four trap system illustrated,
each engagement of the trap contact lobe 188, with an electrical contact 190, will
actuate both a mode valve for one trap and, at the same instant, a ratchet for another
trap.
[0044] In the case of a particulate trap system in which no exhaust brake is employed, the
regeneration process once dictated by the control will continue without interruption
until the entire trap has been cleaned. However, in the case of a particulate trap
system in which the exhaust brake pressure plays a role, the regeneration process
will be interrupted each time the exhaust brake is turned off. This action will stop
the rotation of the rotor 180. When the exhaust brake is again applied, the rotor
will again begin to rotate. To prevent extraneous mode valve and ratchet movements,
the rotor is constantly energized. If the contact lobe 188, is in contact with an
electrical contact 190, when the rotor stops, the mode valve or ratchet will simply
remain in the actuated position until once again the rotor begins to rotate.
[0045] With a single particulate trap system, only two electrical contacts would be used,
with the mode valve contact and the ratchet contact placed at opposite sides of the
timer housing 181. The timer rotation would then provide the alternate action required
for phase 1 and phase 2 of the regeneration process. With a multiple trap system such
as the one illustrated for a four trap system, the mode valve contacts and the ratchet
contacts would be arranged in numerical sequence around the housing. This arrangement
will provide an evenly spaced series of reverse pressure pulses and consequently,
a more steady flow to the spiral burner. The ratchet actuations would be interspersed
evenly between the periods of reverse flow.
[0046] FIG. 19 is a cross section of a test rig 200 used to load the trap by connection
to the diesel engine exhaust as shown. The test engine (not shown) is a small 3600
rpm Onan diesel engine such as used for a generator set in recreational vehicles.
The three cylinder four cycle engine has a displacement of 43.85 cubic inches (0.72
liters) and a rating of 16.6 HP at 3600 rpm and uses conventional No. 2 diesel fuel
having less than 500 ppm sulfur. The load of the engine can be varied from idle, one
air conditioner operating or two air conditioners operating (actual hp steps unknown).
A 5.66 in. x 6.00 in. particulate trap module T is loaded axially and the gaskets
G define a 3.5 in. diameter opening at each end which provides an effective trap volume
of 57.73 cubic inches (0.95 liters). As exhaust flows from the engine and through
the trap T the pressure drop across the trap is measured by a manometer and the test
is ended when the pressure drop totals 36 in. W.G. An effort was made to keep the
same overall average load factor during operation, portions of which included idle
and with one or two air conditioners.
[0047] The particulate traps T obtained for the tests were two 5.66 in. dia. x 6 in. long
Corning DuraTrap™ 200/12 modules, one of which was identified as and permanently labeled
"A" and the other "B". Also obtained were two Corning DuraTrap™ 100/17 modules, one
of which was identified as and permanently labeled "C" and the other "D". All of the
new traps were dried at 400 degrees Fahrenheit for 4-5 hours and then weighed using
a scale with an accuracy of plus or minus 0.01 grams. During the tests each of the
traps used were similarly weighed following each loading and each regeneration of
the traps.
[0048] FIG. 20 is a cross section of a trap regeneration test rig 210. It consists of the
same trap holding and sealing arrangement. Two inch pipes are used to provide air
under the desired reverse pressure to the clean end of the trap from a 5.5 cubic foot
surge tank ST which is supplied from a small air compressor through a pressure reducing
control valve V. Flow leaves the dirty end of the trap and, initially, is prevented
from leaving the rig by a snap open one inch diameter ball valve. Thus, air pressure
is permitted to gradually build up to a desired reverse pressure (eg. 35 psig, 20psig,
etc.).
[0049] Following stabilization of the air pressure at the desired level, the snap- open
ball valve is very quickly snapped open. This results in an almost instantaneously
applied reverse pressure across the porous walls and a similarly quick dislodgement
of the particulate cake and removal of the resulting particles.
[0050] FIG. 21 lists the results of the various dry weight changes of a Corning DuraTrap™
200/12 trap module starting with a new clean dry trap when regenerated with 35 psi
reverse pressure drop.
[0051] FIG. 22 is a graph of the data in FIG. 21 illustrating the dry trap weight gains
following loading and the dry trap weight losses following regeneration. It can be
seen that after the first two loadings and regenerations the weight gains during loading
and weight loss following regeneration are equal. This shows the effectiveness of
regeneration at 35 psi reverse pressure. This is a normal reverse pressure during
exhaust braking obtained by closing a remote actuated relief valve (e.g. D-Celerator
® 76 diesel exhaust brake).
[0052] FIG. 23 lists the results of the various dry trap weight changes of a Corning DuraTrap™
100/17 trap module starting with a new clean dry trap when regenerated with 20 psi
reverse pressure drop.
[0053] FIG. 24 is a graph of the data in FIG. 23 that illustrates the dry trap weight gains
following loading and the dry trap weight losses following regeneration. It can be
seen that after the first three loadings and regenerations the weight gains during
loading and weight loss following regeneration are generally equal. This shows the
effectiveness of the 22 psi reverse pressure obtained by closing the remote actuated
relief valve (e.g. D-Celerator® 76 diesel exhaust brake) during engine low idle operation.
[0054] Movies were made of the reverse flow being emitted from the exit of the ball valve
during a 20 psi regeneration and it was found that all of the added particulate was
removed from the entire 0.95 liter trap in just 0.13 seconds! This very quick regeneration
of a test trap of about the same size as the group of passages that will be selected,
suggests that each step (phase 1 plus phase 2) of the regeneration process that was
shown in FIG. 9 can be completed in one second instead of the ten seconds shown. Thus,
the forty groups of selected passages of a twelve inch diameter trap can all be completely
regenerated in just forty seconds instead of the earlier estimated seven minutes.
[0055] The very short regeneration time suggests that the safety timer, if used, would almost
never be activated. It also suggests that it may be desirable to incorporate in on-road
vehicles (FIG. 14) a tachometer signal similar to used in FIG. 13 but which would
open a relay in the remote actuated relief valve line thus returning the trap exit
pressure to normal as the engine slows down to low idle speed. This would limit regeneration
to braking during deceleration and return the system to normal filtration as the vehicle
idles when slowed or stopped. This very minor change would eliminate any possible
pressure related interference with other emission controls and substantially prevent
any increase in vehicle fuel consumption related to the particulate trap system.
[0056] The method of regenerating a wall-flow particulate trap having a plurality of contiguous
porous walls for filtering particulate from an exhaust system of an internal combustion
engine, includes the steps of: creating a backpressure in the entire exhaust system
from a location downstream of the trap; creating a reverse pressure drop across only
a portion of the porous walls to dislodge accumulated particulate therefrom; and causing
a portion of filtered exhaust gas to flow back through said portion of the porous
walls to carry the dislodged particulate out of the trap.
[0057] While the exhaust system in which the trap 20 is used can be the usual system of
an entire engine; there can be more than one exhaust system for an engine. For example
an eight cylinder engine may have dual exhausts. In some very large engines there
may be even more exhaust systems. Thus, while the above description discloses increasing
the back pressure across the entire exhaust system, it should be understood that separate
exhaust systems may or may not be simultaneously so increased.
[0058] It is deemed that there has been shown and described several embodiments of particulate
trap systems, controls therefore, and methods of operation; however, it is to be understood
that variations and modifications can be made thereto within the skill of those skilled
in the art.
[0059] Following is a summary of various aspects of the disclosure. The invention itself,
however, is defined in the appended claims following this summary.
- 1. A particulate trap system for an exhaust system of an internal combustion engine
and including a monolithic wall-flow particulate trap, having a plurality of contiguous
porous walls, a remotely actuated relief valve downstream of said trap for periodically
creating a reverse pressure throughout the exhaust system upstream of the relief valve
and including said trap, a reversing apparatus for periodically creating a reverse
pressure drop across a portion of the contiguous porous walls of said trap to dislodge
accumulated particulate and cause a portion of the filtered exhaust gas to flow back
through said portion of the contiguous porous walls to remove particulate therefrom,
and controls for actuating the relief valve and the reversing apparatus.
- 2. A particulate trap system of item 1 in which the valve downstream of said trap
is a relief valve which has a first open position permitting unrestricted flow of
filtered exhaust to the atmosphere and a second position restricting passage of the
filtered exhaust until a pre-selected pressure level is reached.
- 3. A particulate trap system as set forth in item 1 wherein the reversing apparatus
includes a mode valve at the upstream end of the trap and movable between a first
position allowing exhaust flow through said portion of the contiguous walls and a
second position blocking such exhaust flow and creating the reverse pressure drop.
- 4. A particulate trap system as set forth in item 3, wherein the mode valve is a three-way
mode valve; and including: a particulate disposal unit at ambient pressure and a stationary
purge duct operatively connected to the three-way mode valve so that, in the first
position, flow from the purge duct to the particulate disposal unit is blocked and
flow of unfiltered engine exhaust passes through the purge duct to said selected passages
of the trap to be filtered and, in the second position, blocks in-flow of unfiltered
engine exhaust and opens the purge duct to the particulate disposal unit.
- 5. A particulate trap system as set forth in item 1 wherein said reversing apparatus
includes an indexing mechanism upstream of said trap to periodically change the said
portion of the porous walls receiving the back flow of filtered exhaust gas so that
the entire trap is systematically cleaned.
- 6. A particulate trap system according to item 5 in which the indexing mechanism includes
a duct rotor that is periodically rotated by a ratchet actuator operatively arranged
to engage said duct rotor.
- 7. A particulate trap system according to item 6 wherein the trap has an inlet face,
and the duct rotor has a first end that is flat and smooth; and including a spring
for lightly pressing the duct rotor against the inlet face of the trap to provide
a seal between the duct rotor and the inlet face: and further including a stationary
purge duct for receiving engine exhaust; the duct rotor having a second end connected
to the stationary purge duct; and being constructed and arranged so that a portion
of the engine exhaust passes to the selected portion of the passages of said trap
articles may pass for disposal of the dislodged particulate outside the trap.
- 8. A particulate trap system according to item 6 including:
a mode valve at the upstream end of the trap and movable between a first position
allowing exhaust flow through said portion of the contiguous walls and a second position
blocking such exhaust flow and creating the reverse pressure drop, and when the mode
valve is in its first position and the duct rotor pressures are balanced there is
substantially no pressure induced force pressing the duct rotor against the trap inlet
face; and
arranged so that when said ratchet actuator is energized the duct rotor rotates to
select a new group of passages having accumulated particulate; and when de-energized
the duct rotor remains stationary; and when said mode valve is moved to its second
position a pressure differential is created across walls of the duct rotor that dislodges
and removes the collected particulate and the pressure differential increases the
force pushing the duct rotor against the upstream end of the trap.
- 9. A particulate trap system according to item 8 in which the controls include an
auxiliary timer for alternately energizing the mode valve and the ratchet actuator.
- 10. A particulate trap system according to item 1 in which the controls are actuated
following attainment of a pre-selected trap exhaust pressure drop during normal filtration
operation of the engine.
- 11. A particulate trap system according to item 1 in which the internal combustion
engine is mounted in a vehicle, and the controls are actuated during deceleration
of the vehicle, and in which the reverse pressure downstream of the trap exit resulting
from closure of the remote actuated relief valve also increases engine backpressure
which is effective as an exhaust brake, and said remotely actuated relief valve being
constructed and arranged for use as an exhaust brake during periods of normal filtering
operation between trap regenerations.
- 12. A particulate trap system according to item 1 in which the controls effect regeneration
of the trap, and so arranged that regeneration occurs during engine low idle operation
or when the engine is operating at normal speeds.
- 13. A method of regenerating a wall-flow particulate trap having a plurality of contiguous
porous walls for filtering particulate from an exhaust system of an internal combustion
engine, the method including the steps of: creating a backpressure in the entire exhaust
system from a location downstream of the trap; creating a reverse pressure drop across
only a portion of the porous walls to dislodge accumulated particulate therefrom;
and causing a portion of filtered exhaust gas to flow back through said portion of
the porous walls to carry the dislodged particulate out of the trap.
- 14. A particulate trap system for an exhaust system of an internal combustion engine
and including a wall-flow particulate trap having a plurality of porous walls, a valving
mechanism downstream of said trap for periodically creating a reverse pressure throughout
the exhaust system upstream of the valving mechanism and including said trap, a reversing
apparatus operative after the reverse pressure is created for periodically creating
a substantially instantaneous reverse pressure drop across a portion of the porous
walls of said trap to dislodge accumulated particulate and cause a portion of the
filtered exhaust gas to flow back through said portion of the porous walls to remove
the dislodged particulate therefrom, an indexing mechanism to periodically change
the said portion of the porous walls receiving the back flow of filtered exhaust gas,
and controls for starting and stopping a regeneration cycle.
- 15. A particulate trap system as set forth in item 14, wherein the timer apparatus
includes a main timer to start and stop the regeneration cycle.
- 16. A particulate trap system as set forth in item 15, wherein the controls include
a first pressure switch which closes when the trap needs regeneration to energize
the main timer.
- 17. A particulate trap system as set forth in item 16, wherein the timer apparatus
includes an auxiliary timer for controlling the indexing mechanism.
- 18. A particulate trap system as set forth in item 17, wherein operation of the relief
valve creates said reverse pressure, and the event circuit de-energizes the main timer
and connects it to the auxiliary timer, and places the indexing mechanism under control
of the auxiliary timer.
- 19. A particulate trap system as set forth in item 18, wherein the reversing apparatus
includes a mode valve at an upstream end of the trap and movable between a first position
allowing exhaust flow through said portion of the porous walls and a second position
blocking such exhaust flow and creating the reverse pressure drop; and wherein the
auxiliary timer also controls the mode valve.
- 20. A particulate trap system as set forth in item 19, wherein the controls include
a second pressure switch which closes in response to a preselected level of the reverse
pressure and re-energizes the main timer and energizes the auxiliary timer.
- 21. A particulate trap system as set forth in item 1, including a main timer, an auxiliary
timer, a sensor for determining that regeneration is needed, and an igniter having
an igniter element; and wherein the main timer starts operation when the sensor so
determines, the main timer being operative to preheat the igniter element for burning
the particulate, the main timer thereafter operating in concert with the auxiliary
timer during the time the reverse pressure is created and the particulate is being
removed from the porous walls, the main timer being operative to de-energize the relief
valve after particulate removal to cease the reverse pressure and return the exit
pressure to a normal pressure, and said controls being operative to return the particulate
trap system to normal filtration until another regeneration is needed.
- 22. A system for regenerating a particulate trap in an exhaust system of an internal
combustion engine and including a wall-flow particulate trap having a plurality of
porous walls for filtering engine exhaust, and removing particulates therefrom to
form a particulate cake on the porous walls, a valving mechanism downstream of said
trap for periodically creating a reverse pressure throughout said trap, a reversing
apparatus operative after the reverse pressure is created for periodically creating
a substantially instantaneous reverse pressure drop across the porous walls of said
trap to dislodge accumulated particulate cake and causing the filtered exhaust gas
to flow back through the porous walls to remove the dislodged particulate from said
trap, and controls for starting and stopping a regeneration cycle.
- 23. A system for regenerating a particulate trap as set forth in item 22 wherein the
back pressure is increased to about 35 psig.
- 24. A system for regenerating a particulate trap as set forth in item 23 wherein the
back pressure is increased to a range from about 20 psig to about 35 psig.
- 25. A system for regenerating a particulate trap as set forth in item 22 wherein the
valving mechanism includes a relief valve having a first open position permitting
flow of filtered exhaust to atmosphere and a second position restricting flow of the
filtered exhaust until the pressure throughout the exhaust system reaches a pre-selected
level.
- 26. A system for regenerating a particulate trap as set forth in item 22 including
a purge duct upstream of said trap for receiving the dislodged particulate from said
trap, and wherein the reversing apparatus includes a purge duct valve associated with
the purge duct.
- 27. A system for regenerating a particulate trap as set forth in item 26 wherein the
controls are operative for opening the purge duct valve to thereby drop the pressure
on the particulate cake to ambient; thereby creating a pressure drop sufficient to
dislodge portions of the cake.
- 28. A system for regenerating a particulate trap-as set forth in item 26, wherein
the porous walls define a plurality of trap passages; wherein the purge duct valve
arrangement is operative during normal filtration for admitting unfiltered engine
exhaust gas into the purge duct and directing the exhaust gas to some of the trap
passages for filtration; and said purge duct valve arrangement being controlled during
regeneration so that the filtered exhaust gas flows from some of the trap passages
back through the purge duct to remove the dislodged particulate from said trap.
- 29. A particulate trap system as set forth in item 22, wherein the reversing apparatus
includes a valve arrangement at the upstream end of the trap and movable between a
first position allowing exhaust flow through a portion of the porous walls and a second
position blocking said exhaust flow and creating the reverse pressure drop.
- 30. A particulate trap system as set forth in item 29, including a particulate disposal
unit at ambient pressure and a stationary purge duct operatively connected to the
particulate disposal unit and to the valve arrangement at the upstream end of the
trap valve; and so that, in the first position, flow from the purge duct to the particulate
disposal unit is blocked and, in the second positions opens the purge duct to the
particulate disposal unit.
- 31. A particulate trap as set forth in item 30 wherein the particulate disposal unit
includes a separator.
- 32. A particulate trap as set forth in item 30 wherein the particulate disposal unit
includes a storage chamber.
- 33. A particulate trap system according to item 22 wherein said reversing apparatus
includes an indexing mechanism upstream of the trap to periodically change the said
portion of the porous walls receiving the backflow of filtered exhaust gas so that
the entire trap is systematically regenerated.
- 34. A particulate trap system according to item 33 wherein the indexing mechanism
includes a duct rotor and a ratchet actuator operatively arranged to engage said duct
rotor for periodically rotating the duct rotor to a new position.
- 35. A particulate trap system according to item 34 wherein the trap has an inlet face,
and the duct rotor has a first end that is flat and smooth; and the duct rotor having
a spring for lightly pressing the first end against the inlet face of the trap; and
further including a stationary purge duct, the duct rotor having a second end connected
to the stationary purge duct.
- 36. A particulate trap system according to item 34 including: a mode valve at the
upstream end of the trap and movable between a first position allowing exhaust flow
through said portion of the contiguous walls and a second position blocking such exhaust
flow and creating the reverse pressure drop, and when the mode valve is in its first
position and the duct rotor pressures are balanced there is substantially no pressure
induced force pressing the duct rotor against the trap inlet face; and arranged so
that when said ratchet actuator is energized the duct rotor rotates to select a new
group of passages having accumulated particulate; and when de-energized the duct rotor
remains stationary; and when said mode valve is moved to its second position a pressure
differential is created across the walls of the duct rotor that dislodges and removes
the collected particulate and the pressure differential increases the force pushing
the duct rotor against the upstream end of the trap.
- 37. A particulate trap system according to item 26 wherein the controls include an
auxiliary timer for actuating the purge duct valve and the valving mechanism downstream
of the trap.
- 38. A particulate trap system according to item 22 including a separator operative
for receiving said dislodged particulate particles from the trap.
- 39. A particulate trap system according to item 22 in which the controls are actuated
following attainment of a pre-selected trap exhaust pressure drop during normal filtration
operation of the engine.
- 40. A particulate trap system as set forth in item 22, wherein the controls for starting
and stopping a regeneration cycle include a main. timer.
- 41. A particulate trap system for an exhaust system of an internal combustion engine
and including a wall-flow particulate trap having a plurality of porous walls for
filtering engine exhaust and removing particulates therefrom which fill the pores
of the trap and form a particulate cake on the upstream surface of the trap walls,
a first valve for periodically creating a back pressure throughout at least a portion
of the exhaust system including the trap in its entirety, a purge duct upstream of
the trap adjacent the inlet end thereof for receiving a reverse flow of gas through
the trap and having a valve for directing back flow of gas through the trap through
the purge duct, apparatus for operating the first valve to increase the back pressure
to a level sufficient to regenerate the trap by reverse flow and thereafter for quickly
opening the purge duct valve to release outflow almost instantly and drop the said
back pressure to substantially ambient in at least a portion of the trap passages
that contain collected particulate cake on the entrance surfaces said drop in pressure
to ambient almost instantly creating a pressure drop across the particulate cake sufficient
to dislodge portions of the cake whereby the cake portions are directed through the
purge duct.
1. A system for regenerating a particulate trap in an exhaust system of an internal combustion
engine and including a wall-flow particulate trap having a plurality of porous walls
for filtering engine exhaust. and removing particulates therefrom to form a particulate
cake on the porous walls, a valving mechanism downstream of said trap for periodically
creating a reverse pressure throughout said trap, a reversing apparatus operative
after the reverse pressure is created for periodically creating a substantially instantaneous
reverse pressure drop across the porous walls of said trap to dislodge accumulated
particulate cake and causing the filtered exhaust gas to flow back through the porous
walls to remove the dislodged particulate from said trap, and controls for starting
and stopping a regeneration cycle.
2. A system for regenerating a particulate trap as set forth in claim-1 wherein the back pressure is increased to a range from about 20 psig to about 35
psig, and preferably to about 35 psig.
3. A system for regenerating a particulate trap as set forth in claim-1 wherein the valving mechanism includes a relief valve having a first open position
permitting flow of filtered exhaust to atmosphere and a second position restricting
flow of the filtered exhaust until the pressure throughout the exhaust system reaches
a pre-selected level.
4. A system for regenerating a particulate trap as set forth in claim 1 including a purge
duct upstream of said trap for receiving the dislodged particulate from said trap,
and wherein the reversing apparatus includes a purge duct valve associated with the
purge duct.
5. A system for regenerating a particulate trap as set forth in claim 4 wherein the controls
are operative for opening the purge duct valve to thereby drop the pressure on the
particulate cake to ambient; thereby creating a pressure drop sufficient to dislodge
portions of the cake.
6. A system for regenerating a particulate trap-as set forth in claim 4, wherein the
porous walls define a plurality of trap passages; wherein the purge duct valve arrangement
is operative during normal filtration for admitting unfiltered engine exhaust gas
into the purge duct and directing the exhaust gas to some of the trap passages for
filtration; and said purge duct valve arrangement being controlled during regeneration
so that the filtered exhaust gas flows from some of the trap passages back through
the purge duct to remove the dislodged particulate from said trap.
7. A particulate trap system as set forth in claim 1, wherein the reversing apparatus
includes a valve arrangement at the upstream end of the trap and movable between a
first position allowing exhaust flow through a portion of the porous walls and a second
position blocking said exhaust flow and creating the reverse pressure drop,
said particulate trap system preferably further including a particulate disposal unit
at ambient pressure and a stationary purge duct operatively connected to the particulate
disposal unit and to the valve arrangement at the upstream end of the trap valve;
and so that, in the first position, flow from the purge duct to the particulate disposal
unit is blocked and, in the second positions opens the purge duct to the particulate
disposal unit,
wherein preferably the particulate disposal unit includes a separator or a storage
chamber.
8. A particulate trap system according to claim 1 wherein said reversing apparatus includes
an indexing mechanism upstream of the trap to periodically change the said portion
of the porous walls receiving the backflow of filtered exhaust gas so that the entire
trap is systematically regenerated.
9. A particulate trap system according to claim 8 wherein the indexing mechanism includes
a duct rotor and a ratchet actuator operatively arranged to engage said duct rotor
for periodically rotating the duct rotor to a new position, wherein preferably the
following optional features are provided: the trap has an inlet face, and the duct
rotor has a first end that is flat and smooth; and the duct rotor having a spring
for lightly pressing the first end against the inlet face of the trap; and further
including a stationary purge duct, the duct rotor having a second end connected to
the stationary purge duct.
10. A particulate trap system according to claim 9 including: a mode valve at the upstream
end of the trap and movable between a first position allowing exhaust flow through
said portion of the contiguous walls and a second position blocking such exhaust flow
and creating the reverse pressure drop, and when the mode valve is in its first position
and the duct rotor pressures are balanced there is substantially no pressure induced
force pressing the duct rotor against the trap inlet face; and arranged so that when
said ratchet actuator is energized the duct rotor rotates to select a new group of
passages having accumulated particulate; and when de-energized the duct rotor remains
stationary; and when said mode valve is moved to its second position a pressure differential
is created across the walls of the duct rotor that dislodges and removes the collected
particulate and the pressure differential increases the force pushing the duct rotor
against the upstream end of the trap.
11. A particulate trap system according to claim 4 wherein the controls include an auxiliary
timer for actuating the purge duct valve and the valving mechanism downstream of the
trap.
12. A particulate trap system according to claim 1 including a separator operative for
receiving said dislodged particulate particles from the trap.
13. A particulate trap system according to claim 1 in which the controls are actuated
following attainment of a pre-selected trap exhaust pressure drop during normal filtration
operation of the engine.
14. A particulate trap system as set forth in claim 1, wherein the controls for starting
and stopping a regeneration cycle include a main timer.
15. A particulate trap system according to any of the preceding claims, for an exhaust
system of an internal combustion engine and including a wall-flow particulate trap
having a plurality of porous walls for filtering engine exhaust and removing particulates
therefrom which fill the pores of the trap and form a particulate cake on the upstream
surface of the trap walls, a first valve for periodically creating a back pressure
throughout at least a portion of the exhaust system including the trap in its entirety,
a purge duct upstream of the trap adjacent the inlet end thereof for receiving a reverse
flow of gas through the trap and having a valve for directing back flow of gas through
the trap through the purge duct, apparatus for operating the first valve to increase
the back pressure to a level sufficient to regenerate the trap by reverse flow and
thereafter for quickly opening the purge duct valve to release outflow almost instantly
and drop the said back pressure to substantially ambient in at least a portion of
the trap passages that contain collected particulate cake on the entrance surfaces
said drop in pressure to ambient almost instantly creating a pressure drop across
the particulate cake sufficient to dislodge portions of the cake whereby the cake
portions are directed through the purge duct.