U.S. patent application number 12/373009 was filed with the patent office on 2009-08-20 for system and processes for storing an additive and injecting it into the exhaust gases of an engine.
This patent application is currently assigned to INERGY AUTOMOTIVE SYSTEMS RESEARCH (Societe Anonyme). Invention is credited to Joel Op De Beeck, Francois Dougnier, Vincent Potier, Jules-Joseph Van Schaftingen.
Application Number | 20090205316 12/373009 |
Document ID | / |
Family ID | 37709685 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090205316 |
Kind Code |
A1 |
Dougnier; Francois ; et
al. |
August 20, 2009 |
System and processes for storing an additive and injecting it into
the exhaust gases of an engine
Abstract
System for storing an additive solution and injecting it into
the exhaust gases of an internal combustion engine, the system
comprising a tank for storing the additive and a rotary pump, a
metering valve and an injector which are separate devices, this
system making it possible to meter and inject the additive solution
into the exhaust gases as is, without diluting it with a gas. In
this system, the pump outlet pressure is regulated by adjusting the
rotational speed of the pump. Process using such a system.
Inventors: |
Dougnier; Francois;
(Boortmeerbeek, BE) ; De Beeck; Joel Op; (Lint,
BE) ; Potier; Vincent; (Brussels, BE) ; Van
Schaftingen; Jules-Joseph; (Wavre, BE) |
Correspondence
Address: |
Solvay;c/o B. Ortego - IAM-NAFTA
3333 Richmond Avenue
Houston
TX
77098-3099
US
|
Assignee: |
INERGY AUTOMOTIVE SYSTEMS RESEARCH
(Societe Anonyme)
Brussels
BE
|
Family ID: |
37709685 |
Appl. No.: |
12/373009 |
Filed: |
July 11, 2007 |
PCT Filed: |
July 11, 2007 |
PCT NO: |
PCT/EP07/57066 |
371 Date: |
January 8, 2009 |
Current U.S.
Class: |
60/274 ;
60/295 |
Current CPC
Class: |
Y02T 10/12 20130101;
F01N 2610/02 20130101; Y02T 10/24 20130101; F01N 3/2066 20130101;
F01N 2610/1473 20130101; F01N 2610/14 20130101 |
Class at
Publication: |
60/274 ;
60/295 |
International
Class: |
F01N 3/20 20060101
F01N003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 13, 2006 |
FR |
0606425 |
Claims
1. A system for storing an additive solution and injecting it into
the exhaust gases of an internal combustion engine, said system
comprising a tank for storing the additive and a rotary pump, a
metering valve and an injector which are separate devices, this
system making it possible to meter and inject the additive solution
into the exhaust gases as it is, without diluting it with a gas,
wherein the pump outlet pressure is regulated by adjusting the
rotational speed of the pump.
2. The system according to claim 1, wherein the pump discharges an
excess of additive solution (i.e. a higher flow than that of the
injector), and wherein the system comprises a return line equipped
with a pressure-limiting device that enables the excess of solution
to be returned to the tank.
3. The system according to claim 2, wherein the pressure-limiting
device is a restrictor which may be combined with a non-return
valve.
4. The system according to claim 2, wherein the pressure-limiting
device is a calibrated spring or diaphragm valve.
5. The system according to claim 2, wherein the pressure-limiting
device is located downstream of the metering valve, in a line that
enables the flow of additive not consumed by this valve to be
returned to the tank.
6. The system according to claim 2, wherein the pressure-limiting
device is located downstream of the injector, in a line that
enables the flow of additive not consumed by this injector to be
returned to the tank.
7. The system according to claim 6, comprises comprising a by-pass
line that enables the flow of additive not consumed by the injector
to be brought back upstream of the metering valve instead of to the
tank when the temperature of the additive in the tank exceeds a
threshold value.
8. The system according to claim 6, comprising a purge valve with a
gas inlet upstream of the pump.
9. The system according to any one of the preceding claims claim 1,
comprising a filter located between the tank and the pump.
10. The system according to claim 2, wherein the pump, the
pressure-limiting device and the metering valve are integrated into
a flange which is connected to the injector via an injection
line.
11. A process for storing an additive solution and injecting it
into an exhaust pipe of an internal combustion engine, said process
consisting in conveying the solution stored in a tank to an
injector using a rotary pump and a metering valve, injector, pump
and metering valve being separate devices, and in injecting this
solution into the exhaust pipe as is, without diluting it with a
gas, the pump outlet pressure being regulated by adjusting its
rotational speed.
12. The process according to claim 11, wherein the pump discharges
an excess of additive solution (i.e. a higher flow than that of the
injector), and wherein this excess is returned to the tank via a
return line equipped with a pressure-limiting device.
13. The process according to claim 11, wherein the metering valve
is opened for an adjustable duration and frequency, and wherein the
amount of additive solution is metered by adjusting this duration
and this frequency electronically.
Description
[0001] The present invention relates to a system and process for
storing an additive and injecting it into the exhaust gases of an
engine.
[0002] The change in legislation relating to emissions from diesel
vehicles especially stipulates a significant reduction in releases
of nitrogen oxide in exhaust gases. The SCR (Selective Catalytic
Reduction) process in which nitrogen oxides (NOx) are reduced by
ammonia is one of the technologies of choice for achieving this
pollution control objective. An ammonia precursor solution
(generally a solution of urea) is then injected into the exhaust
line upstream of the SCR catalyst. The operation of this catalyst
requires precise metering of the amount of solution sprayed.
[0003] In a known manner, decoupling the pumping, metering and
injection operations results in a better precision of the amounts
of ammonia precursor solution introduced into the exhaust line.
[0004] Thus, Patents U.S. Pat. No. 6,041,594 and U.S. Pat. No.
6,273,120 both describe systems comprising a separate pump,
metering valve and injector that enable each of these functions to
be carried out. The rapid metering valve (i.e. a valve operating
with an adjustable opening frequency and duration) combined with a
suitable pump outlet pressure (via a pressure-regulating device)
enables precise metering of sprayed amounts of the ammonia
precursor solution. These documents however both recommend recourse
to compressed air which is mixed with the additive in a mixing
chamber prior to its injection into the exhaust gases using an
injector. This compressed air would especially prevent clogging of
the injector which could be caused by a solid deposit of the
additive and/or its degradation products resulting from the high
temperature in the vicinity of the exhaust pipe.
[0005] These systems have the advantage of a compact, simple and
adjustable architecture (for example, the pump may be integrated
into the tank; the metering valve may be nearer to or further from
the injector depending on the space available beneath the floor of
the vehicle). The pump and the metering valve may thus be offset
from the exhaust line, which prevents them from overheating and
increases the metering accuracy of the valve. Moreover, the
injector may be adapted as a function of the size and distribution
of the desired droplets. Finally, these systems are particularly
suitable for retrofitting to vehicles in circulation.
[0006] Such systems however require provision of a compressed-air
source, which is furthermore not always available on the vehicle
and which therefore has to be purposely provided, which is
expensive. Moreover, diluting the additive leads to a reduction in
the metering accuracy. Finally, recourse to a mixing chamber adds
complexity and expense to these systems.
[0007] The present application aims at solving these problems and
is based on the fact that recourse to compressed air is in fact not
necessary in these "decoupled" systems. Indeed, it would appear
that the aforementioned solid deposit disappears very quickly in
solution and is easily removed by dissolving during a new
injection. In fact, suitable control of the metering pump makes it
possible to prevent clogging of the injector, and also makes it
possible to prevent the formation of a drop at the outlet orifice
of this injector.
[0008] Document EP 1 656 986 also proposes a system without
compressed air where the pump, metering valve and injector are
separate devices, but this system involves a pressure transducer
and a solenoid valve for regulating the return flow (if necessary)
which is relatively complicated and expensive.
[0009] The present application aims at solving this problem by
providing a system that is significantly simpler, less expensive
and just as effective. Therefore, the present invention relates to
a system for storing an additive solution and injecting it into the
exhaust gases of an internal combustion engine, said system
comprising a tank for storing the additive and a rotary pump, a
metering valve and an injector, this system making it possible to
meter and inject the additive solution into the exhaust gases as it
is, without diluting it with a gas such as compressed air. In
particular, the system according to the invention does not comprise
a mixing chamber nor any device whatsoever for diluting the
additive with a gas such as compressed air. In the system according
to the invention, the pump, metering valve and injector are
separate devices and the pump outlet pressure is regulated by
adjusting the rotational speed of the pump.
[0010] The additive concerned by the invention is preferably a
reducing agent capable of reducing the NOx present in the exhaust
gases of an internal combustion engine. Advantageously it is
ammonia, used directly (which has the associated safety and
corrosion drawbacks) or generated in situ in the exhaust gases from
a precursor, such as urea (which enables the aforementioned
drawbacks to be avoided). The invention gives good results with
urea and, in particular, with aqueous solutions of urea. Eutectic
solutions (comprising 32.5% by weight of urea) are very
suitable.
[0011] The present invention may be applied to any internal
combustion engine likely to generate NOx in its exhaust gases. It
may be an engine with or without a fuel return line (i.e. a line
returning the surplus fuel not consumed by the engine to the fuel
tank). It is advantageously applied to diesel engines, and in
particular to vehicle diesel engines and particularly preferably to
the diesel engines of heavy goods vehicles.
[0012] The system according to the invention comprises at least one
tank intended for storing the additive. This tank may be made from
any material, preferably one that is chemically resistant to the
additive in question. In general, this is metal or plastic.
Polyolefin resins, in particular polyethylene (and more
particularly HDPE or high-density polyethylene), constitute
preferred materials.
[0013] The system according to the invention generally comprises an
injection line intended to bring the additive to the exhaust pipe
of the engine that, in order to do this, connects the tank, the
pump, the metering valve and the injector; the pump, metering valve
and injector being separate devices placed in series from upstream
to downstream (following the flow direction of the additive, i.e.
from the tank (upstream) to the injector (downstream)).
[0014] The pump of the system according to the invention is used to
bring the additive solution to the pressure required for metering
and spraying it. Various types of pumps may be suitable for the
application: gear pump, piston pump, diaphragm pump, etc. This pump
may be located in the additive tank (with the advantage of forming,
with it, a compact and integrated module) or, considering the
corrosive environment, be located outside of the additive tank. Its
constituent materials will preferably be chosen from
corrosion-resistant metals (especially certain grades of stainless
steel and aluminium). The use of copper, even for connection
components, is undesirable.
[0015] According to the invention, the pump outlet pressure is
regulated by a suitable device which makes it possible to act
directly on the rotational speed of the pump. Such a device is
described in Application WO 2007/023142 in the name of the
Applicant, the content of which is, for this purpose, incorporated
by reference in the present application. According to one preferred
variant, the system according to the invention comprises a return
line equipped with a pressure-limiting device and the pump
discharges an excess of additive (by intentionally rotating at too
high a rate, i.e. with too high an outlet pressure), this excess
(difference between the flow from the pump and that from the
injector) being returned to the tank via this line. A simple
calibrated spring or diaphragm valve gives good results. A
preferred device is formed by a simple restrictor on the return
line, preferably combined with a non-return valve. The advantage of
this variant consists in allowing effective cooling of the metering
valve in a simple manner.
[0016] According to a first variant, the pressure-regulating device
is located downstream of the metering valve, in a line returning
the flow of additive not consumed by this valve to the tank.
[0017] According to a second variant, the pressure-regulating
device is located downstream of the injector, in a line returning
the flow of additive not consumed by this injector to the tank.
[0018] The second variant (with excess metering at the injector) is
preferred as it also makes it possible to avoid overheating the
injector. However, it is advantageous in this case to provide a
by-pass line bringing the additive return back upstream of the
metering valve (and preferably upstream of the filter, where
appropriate: see further on) when the temperature of the additive
in the tank exceeds a threshold value (60.degree. C. for
example).
[0019] This variant also makes it possible to easily integrate a
purge function in the conduits, especially to avoid damaging them
in case the additive solution freezes. For this it suffices to
provide a purge valve with a gas (air for example) inlet in the
injection line, upstream of the pump. This valve may then, in a
suitable position, suck air though the conduits and force the
liquid that they contain back towards the tank.
[0020] The injector enabling the injection of the additive into the
exhaust gases is generally located at the end of the injection
line. This injector may be of any known type. It is advantageously
a nozzle or a sprayer making it possible to obtain drops of
solution having a diameter between 5 and 100 .mu.m. Such a nozzle
is advantageously equipped with an orifice having a diameter of
around 150 .mu.m-250 .mu.m. This orifice is supplied by a system of
narrow channels (3-4) producing a "swirl" (vortex) effect in the
solution upstream of the nozzle. Clogging could be avoided by the
purge which removes the last droplets of urea; there is therefore
no crystallization by evaporation.
[0021] Preferably, the system according to the invention also
comprises a filter located between the tank and the pump and making
it possible to retain possible impurities present in the
solution.
[0022] According to the invention, as already explained above, the
pump, valve and injector are separate devices located in the
injection line between the additive storage tank and the exhaust
pipe of the engine. According to one particularly advantageous
variant, and as described in Application FR 06/05082 in the name of
the Applicant (the content of which is incorporated by reference in
the present application), at least the pump is integrated into a
flange present in the tank, in the bottom of it. In a particularly
preferred manner, the pump, the pressure-limitating device and the
metering valve are all integrated into this flange, which is
connected to the injector via an injection line. Thus, a
particularly compact system is obtained.
[0023] The present invention also relates to a process for storing
an additive solution and injecting it into an exhaust pipe of an
internal combustion engine, said process consisting in conveying
the solution stored in a tank to an injector using a rotary pump
and a metering valve, injector, pump and metering valve being
separate devices and in injecting this solution into the exhaust
pipe as is, without diluting it with a gas such as compressed
air.
[0024] In this process according to the invention, the amount of
solution is metered by regulating the opening frequency and
duration of the metering valve. This valve may be a piezoelectric
or solenoid valve, the regulation of which may be electronic. Thus,
most often, the system according to the invention comprises a
computer connected to the metering valve and making it possible to
convey the required amount of additive (especially as a function of
the following characteristics: emission level and degree of
conversion of the NOx; temperature and pressure; engine speed and
load, etc.) to the injector. This computer may also act on the
pressure regulation of the pump. It could, for example, be
advantageous to increase the pressure for low flow rates.
[0025] In a first variant, the amount of additive discharged by the
pump and not consumed by the metering valve (as a function of the
control by the computer) is returned to the additive tank by a
return line connected between the pump and the metering valve. In
another variant, the metering valve conveys an excess of additive
to the injector which is returned to the tank by a return line that
starts from the injector. In both cases, a pressure-limiting device
is located in the return line, which returns the excess flow
(resulting from the difference between the flow from the pump and
the spraying flow) to the tank.
[0026] The present invention is illustrated, in a non-limiting
manner, by FIGS. 1 to 3, which each relate to a different variant
of the invention. In these FIGS. identical numbers represent
identical or similar components. The flow direction of the exhaust
gases is indicated therein by an arrow marked "G".
[0027] FIG. 1 represents a simple system where the metering valve
(4) conveys exactly the amount of additive required to the injector
(8), the excess produced by the pump (3) being returned to the tank
(1) via a calibrated valve (6).
[0028] The tank (1) contains a reducing agent precursor solution,
in this case: an ADBLUE.RTM. 32.5% aqueous urea solution. The
possible impurities are retained by a filter (2). The pump (3)
allows the solution to be withdrawn from the tank and the liquid to
be brought to the pressure needed for the required spraying and for
the return flow needed for cooling the metering valve. The
calibrated valve (6) provides control of the spraying pressure in
the line section (3). Metering of the amount of reducing agent
precursor is carried out by opening the metering valve (4), which
is electronically controlled, with an established opening frequency
and duration. The metering valve (4) is connected to the injector
(nozzle) (8) by the line (7). The nozzle (8) is designed so as to
spray the solution in the form of droplets, of which the size
distribution is in general between 5 .mu.m and 120 .mu.m. The
excess flow (resulting from the difference between the flow from
the pump and the spraying flow) returns to the tank (1) by the line
(5). In one variant of FIG. 1, the calibrated valve (6) is replaced
by a restrictor combined with a simple non-return valve in the case
where the return line (5) is connected to the bottom area of the
tank (1).
[0029] FIG. 2 illustrates a more complex system which includes a
function of cooling the injector (by excess metering of the
additive) and a purge function.
[0030] This system comprises a purge valve (solenoid valve) (11)
which, when the solution is sucked up by the pump (3), is in the
open position so as to connect the tank (1) to the filter (2).
[0031] It also comprises a by-pass valve (solenoid valve) (10)
installed in the return line (5) which this time starts from the
injector (8) to its intersection with a by-pass line (13). This
return makes it possible to avoid excessive overheating of the
nozzle. When the temperature of the solution measured in the tank
(1) exceeds 60.degree. C., the solenoid valve (10) switches over
and the liquid is conveyed into the by-pass line (13) instead of
returning to the tank (1). The valve (11) is a proportional valve.
It could also be an on/off valve or a simple bimetallic strip. As
shown, the system also comprises a purge function for the feed and
return lines. For this purpose, the inlet of the purge valve (11)
is connected to an air inlet (12). With a suitable position of this
valve (11), air may be sucked in by the pump, forcing the liquid
contained in the conduits back towards the tank (1). The lines
illustrated are, in addition, equipped with a known heating
device.
[0032] All the functions of the system are electronically
controlled.
[0033] FIG. 3 illustrates a system that fulfils the same functions
as that of FIG. 2. The components (filter (2), pump (3), metering
valve (4), purge valve (11), calibrated valve (6), by-pass valve
(10)) have however been integrated inside the tank (1), resulting
in a particularly compact system.
* * * * *