Note: Descriptions are shown in the official language in which they were submitted.
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MONITOR OF AMMONIA IN DOSING SYSTEM
Technical Field
[0001] This disclosure relates to an ammonia dosing system which
delivers ammonia in gas phase from an ammonia storage canister into
exhaust for after-treatment of oxides of nitrogen (NO) in the exhaust
by selective catalytic reduction (SCR).
Background
[0002] Selective catalytic reduction (SCR) is an exhaust after-treatment
technology for enabling certain chemical reactions to occur between
oxides of nitrogen (NO) in exhaust and ammonia (NH3) introduced in
gas phase into an exhaust system upstream of an SCR catalyst to
entrain with exhaust flowing toward the catalyst where catalytic
reactions convert NO into Nitrogen (N2) and water (H20).
[0003] A motor vehicle which uses SCR technology for after-treatment of
engine exhaust produced by operation of an internal combustion
engine carries an on-board supply of ammonia which is stored in one
or more canisters. Such canisters are constructed to be removable
from a vehicle, re-chargeable at a service facility, and re-installable in
a vehicle.
[0004] Strontium chloride is an example of a storage medium which is
present inside a canister for storing ammonia in solid phase and
releasing stored ammonia in gas phase when heated to an ammonia
release temperature.
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[0005] Because selective catalytic reduction of NO cannot occur in the
absence of ammonia, information about ammonia in an ammonia
dosing system would be useful in avoiding potential loss or
interruption of ammonia flow between an ammonia storage canister
and in an exhaust system.
Summary of the Disclosure
[0006] This disclosure introduces apparatus and method for acquiring
information about ammonia in an ammonia dosing system through the
use of optically detectable ammonia.
[0007] Certain gases which are typically considered not optically
detectable can be made optically detectable by certain processes. A
process which creates what are called "fluorophore absorber pairs" in
an ammonia molecule can render ammonia optically detectable. The
fluorophore absorber pairs radiate absorbed energy at a characteristic
wavelength.
[0008] A gas which has been rendered optically detectable may be said to
luminesce or fluoresce. Although the terms "luminophore" and
"fluorophore" are used in scientific literature as descriptors of
molecules which are optically detectable, it appears that the latter is
used to characterize certain species of the fanner. The process which
creates fluorophore absorber pairs in an ammonia molecule suggests
that the molecule is a fluorophore, a species of the generic descriptor
"luminophore." The present applicants will use the term
"luminophore" here as a generic descriptor of an optically detectable
molecule.
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[0009] The apparatus and method disclosed here are useful in an ammonia
dosing system which treats engine exhaust passing through an SCR
after-treatment system using ammonia which contains ammonia
luminophores.
[0010] The presence of ammonia luminophores in an ammonia dosing
system provides luminescence of ammonia which renders the
ammonia detectable by optical sensing apparatus.
[0011] Specific sensing capabilities of optical sensing apparatus are a
function of specific optical sensing technique employed and can
extend from merely distinguishing between the presence and the
absence of ammonia to measuring ammonia quantity and/or ammonia
flow.
[0012] Several embodiments of apparatus are disclosed.
[0013] The apparatus and method can reduce the likelihood that an
ammonia storage canister which contains little or no ammonia being
installed in a vehicle.
[0014] The apparatus and method can indicate quantity of ammonia
present inside an ammonia storage canister.
[0015] The apparatus and method can indicate outflow of ammonia from
an ammonia storage canister.
[0016] A general aspect of the disclosed subject matter relates to an
internal combustion engine comprising an exhaust after-treatment
system comprising an SCR catalyst, and an ammonia dosing system
comprising a canister having an interior containing optically
detectable ammonia and a delivery apparatus for delivering optically
detectable ammonia from the canister interior into the exhaust after-
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treatment system to entrain with engine exhaust flowing toward the
SCR catalyst for catalytic conversion of NO, in the engine exhaust.
[0017] A monitor of ammonia luminophores comprises at least one optical
sensor for detecting luminescence of ammonia luminophores in the
ammonia dosing system.
[0018] The monitor comprises a device providing a signal distinguishing
high luminescence of ammonia luminophores detected by the at least
one optical sensor and low luminescence of ammonia luminophores
detected by the at least one optical sensor.
[0019] The least one optical sensor provides a measure of luminescence of
ammonia luminophores which the at least one optical sensor detects,
and the monitor converts a measure of luminescence of ammonia
luminophores which the at least one optical sensor detects into a
quantified measure of ammonia.
[0020] The monitor provides a signal alert when a quantified measure of
ammonia is less than a predetermined quantity.
[0021] The canister comprises a port via which the canister separably
connects to the delivery apparatus, and the at least one optical sensor
is arranged to view luminescence of ammonia luminophores within
the canister's interior.
[0022] When the canister's port is connected to the delivery apparatus and
the at least one optical sensor detects luminescence of ammonia
luminophores greater than a predetermined luminescence, a closure is
operated to allow ammonia flow between the canister interior and the
exhaust after-treatment system. When the canister's port is connected
to the delivery apparatus and the at least one optical sensor detects
luminescence of ammonia luminophores less than the predetermined
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luminescence, the closure is operated to disallow ammonia flow
between the canister interior and the exhaust after-treatment system.
[0023] In a disclosed embodiment, the closure and the at least one optical
sensor are mounted on the delivery apparatus.
[0024] Another general aspect of the disclosed subject matter relates to a
method for detection of ammonia in an ammonia dosing system which
delivers ammonia into an engine exhaust after-treatment system to
entrain with exhaust flowing toward an SCR catalyst for catalytic
conversion of NOR. The method comprises: installing in the ammonia
dosing system an ammonia storage canister which contains ammonia
luminophores; operating the ammonia dosing system to deliver
ammonia from the ammonia storage canister into the exhaust after-
treatment system; and using at least one optical sensor to detect
luminescence of ammonia luminophores in the ammonia dosing
system.
[0025] The method comprises providing a signal distinguishing high
luminescence of ammonia luminophores detected by the at least one
optical sensor and low luminescence of ammonia luminophores
detected by the at least one optical sensor.
[0026] The method comprises using a measure of luminescence of
ammonia luminophores which the at least one optical sensor detects to
quantify a measure of ammonia.
[0027] The method provides a signal alert when a quantified measure of
ammonia is less than a predetermined quantity.
[0028] The method comprises arranging the at least one optical sensor to
view luminescence of ammonia luminophores in the canister's interior
and when the at least one optical sensor detects luminescence of
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ammonia luminophores greater than a predetemiined luminescence,
allowing ammonia flow between the canister interior and the exhaust
after-treatment system, and when the at least one optical sensor
detects luminescence of ammonia luminophores less than the
predetermined luminescence, disallowing ammonia flow between the
canister interior and the exhaust after-treatment system.
Brief Description of the Drawings
[0029] Figure 1 is a general schematic diagram of an internal combustion
engine which utilizes SCR to convert NO in engine exhaust by
chemical reaction with ammonia introduced into the exhaust.
[0030] Figure 2 is a schematic diagram showing more detail.
[0031] Figure 3 is a schematic diagram similar to Figure 2 but showing a
different embodiment.
Detailed Description
[0032] Figure 1 shows a representative internal combustion engine 10
which can be used in stationary or mobile applications. For example,
engine 10 may be a diesel engine of the type which propels a motor
vehicle such as a truck and which comprises structure forming a
number of engine cylinders 12 into which fuel is injected by fuel
injectors 14 to combust with air which has entered combustion
chamber spaces of engine cylinders 12 through an intake system 16
when cylinder intake valves 18 for controlling admission of air from
an intake manifold 20 into respective engine cylinders 12 are open.
[0033] Engine 10 also comprises an exhaust system 22 through which
engine exhaust created by combustion of injected fuel in the
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combustion chamber spaces to operate engine 10 is conveyed to
atmosphere. Cylinder exhaust valves 24 control admission of exhaust
from respective engine cylinders 12 into an exhaust manifold 26 for
further conveyance through exhaust system 22.
[0034] Exhaust system 22 includes an exhaust after-treatment system 28,
including an SCR catalyst 30 for treating exhaust passing through
after-treatment system 28 prior to entry into the atmosphere. An
ammonia dosing system 32 provides ammonia in gas phase for
catalytic conversion of NO in the exhaust.
[0035] Ammonia dosing system 32 comprises at least one ammonia
storage canister 34 and an ammonia dosing controller 36 for
controlling delivery of ammonia through an ammonia delivery
apparatus 38 into after-treatment system 28 and for monitoring
ammonia in the ammonia dosing system.
[0036] Figure 2 shows one of the storage canisters 34 to comprise a
walled enclosure 40 having a port 42 at one axial end via which the
canister separably connects to ammonia delivery apparatus 38.
[0037] Ammonia delivery apparatus 38 comprises a tubular conduit
terminating is a fitting 44 to which port 42 separably connects. Fitting
44 contains at least one optical sensor 46 and a selectively
positionable closure 48.
[0038] Canister 34 comprises an interior containing an ammonia storage
medium 50 for storing ammonia in solid phase and releasing stored
ammonia in gas phase when heated to an ammonia release
temperature. The stored ammonia comprises ammonia luminophores
in quantity sufficient to provide for detection by at least one optical
sensor 46 even when ammonia remaining in canister 34 reaches a
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point calling for canister replacement. Figure 2 shows at least one
optical sensor 46 arranged to view luminescence of optically
detectable ammonia within the canister's interior.
[0039] The at least one sensor 46 and any associated device or devices,
such as a device 52, form a monitor 54 of ammonia luminophores.
Specific sensing capabilities of a particular monitor 54 are a function
of specific optical sensing technique employed. A monitor may have a
capability extending beyond merely detecting the presence or absence
of ammonia to a capability of measuring ammonia quantity and/or
ammonia flow.
[0040] Device 52 functions to provide a signal distinguishing high
luminescence of ammonia luminophores detected by the at least one
optical sensor 46 and low luminescence of ammonia luminophores
detected by the at least one optical sensor 46. Low luminescence
includes no luminescence.
[0041] At least one sensor 46 which provides a measure of luminescence
of ammonia luminophores which the at least one optical sensor 46
detects can enable monitor 54 to convert a measure of luminescence
of ammonia luminophores which the at least one optical sensor 46
detects into a quantified measure of ammonia in canister 34.
[0042] Monitor 54 can provide a signal alert when a quantified measure of
ammonia is less than a predetermined quantity. This is useful in
signaling that ammonia in a canister presently in use is approaching
depletion and that a fresh canister should be brought on line.
[0043] When port 42 is connected to fitting 44 so that at least one optical
sensor 46 can detect luminescence of ammonia luminophores within
the canister interior, and the detected luminescence is greater than a
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predetetntined luminescence, ammonia dosing controller 36 positions
closure 48 via an actuator (not shown) to allow ammonia flow
between the canister interior and after-treatment system 28. When port
42 is connected to fitting 44 and at least one optical sensor 46 detects
luminescence of ammonia luminophores less than the predetermined
luminescence, ammonia dosing controller 36 positions closure 48 to
disallow ammonia flow between the canister interior and the after-
treatment system.
[0044] Because of the presence of at least one optical sensor 46 and
closure 48 in association with ammonia dosing controller 36, the
presence of ammonia in a newly installed canister will be verified by
at least one sensor 46 detecting luminescence of ammonia
luminophores within the interior of the canister and consequently
ammonia dosing controller 36 operating closure 48 to allow flow. If
the presence of ammonia in a newly installed canister is not verified,
ammonia dosing controller 36 maintains closure 48 in the same closed
position which it had assumed when the previous canister was
disconnected from fitting 44 to disallow flow.
[0045] The embodiment of Figure 3 differs from that of Figure 2 in that
the at least one sensor 46 and closure 48 are mounted on canister port
42 rather than on fitting 44. Both the least one sensor 46 and the
actuator for operating closure 48 are to be connected to device 52 and
ammonia dosing controller 36 as shown after port 42 has been
connected to fitting 44.
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