US20150283508A1 - Reductant dosing system - Google Patents
Reductant dosing system Download PDFInfo
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- US20150283508A1 US20150283508A1 US14/245,197 US201414245197A US2015283508A1 US 20150283508 A1 US20150283508 A1 US 20150283508A1 US 201414245197 A US201414245197 A US 201414245197A US 2015283508 A1 US2015283508 A1 US 2015283508A1
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- Prior art keywords
- reductant
- control valve
- reservoir
- pressure
- outlet
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9495—Controlling the catalytic process
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
- F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2590/00—Exhaust or silencing apparatus adapted to particular use, e.g. for military applications, airplanes, submarines
- F01N2590/10—Exhaust or silencing apparatus adapted to particular use, e.g. for military applications, airplanes, submarines for stationary applications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/08—Adding substances to exhaust gases with prior mixing of the substances with a gas, e.g. air
- F01N2610/085—Controlling the air supply
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/14—Arrangements for the supply of substances, e.g. conduits
- F01N2610/1433—Pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2610/00—Adding substances to exhaust gases
- F01N2610/14—Arrangements for the supply of substances, e.g. conduits
- F01N2610/1473—Overflow or return means for the substances, e.g. conduits or valves for the return path
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/18—Parameters used for exhaust control or diagnosing said parameters being related to the system for adding a substance into the exhaust
- F01N2900/1806—Properties of reducing agent or dosing system
- F01N2900/1808—Pressure
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Definitions
- This disclosure is directed to exhaust systems for internal combustion engines that include reductant dosing systems. More specifically, the disclosed reductant dosing systems are less prone to pressure pulsations and can operate at high altitudes and at high temperatures without significant vaporization or boiling of the reductant fluid.
- Internal combustion engines include diesel, gasoline, gaseous fuel-powered and other engines known in the art. These engines produce a complex mixture of emissions. These emissions include gaseous compounds such as oxides of nitrogen, NO and NO 2 , or collectively, NOx. In atmospheric chemistry, the term NOx means the total concentration of NO and NO 2 . Due to increased environmental awareness, the amount of NOx emitted to the atmosphere by an engine is regulated depending on the type, size and/or class of the engine.
- SCR selective catalytic reduction
- Reductant dosing systems may be used to introduce the reductant, e.g., urea, into the exhaust stream.
- an aqueous urea solution may be stored in a tank.
- the aqueous urea solution or reductant fluid may be referred to as DEF (diesel exhaust fluid), and may consist of about 32.5 wt % urea and about 67.5 wt % water.
- DEF is pumped from the tank and intermittently sprayed into the exhaust stream via an injector.
- Some reductant dosing systems control the DEF pressure by varying the pump speed while simultaneously monitoring the DEF pressure.
- a reductant dosing system can produce pressure pulsations, which cannot be accurately controlled by modifying the pump speed.
- the pressure drop in the pump suction line in combination with operation at high altitudes (low ambient pressure) and/or high temperatures can result in significant vaporization or boiling of the DEF. Vaporization or boiling of the DEF may result in a mixture of vapor and fluid entering the pump, which prevents accurate dosing of the DEF into the exhaust stream.
- CN 101818675 avoids relying upon modifying the pump speed by eliminating the pump altogether and pressurizing the DEF tank. While, such a system without a pump is applicable to passenger vehicles with diesel engines, reliance upon a pressurized DEF tank alone, without a pump, may not be suitable for larger diesel power systems, such as those for trucks, generators, construction equipment, mining equipment, etc.
- the reservoir may be fluidly connected to an inlet of a reductant pump.
- the reductant pump may have an outlet that is fluidly connected to the reservoir, as well as to an inlet of a pressure regulator and to an inlet of an injector.
- the pressure regulator may include a reductant pressure control valve that fluidly connects the outlet of the reductant pump to the reservoir when the reductant pressure control valve is in an open position.
- the system may further include a compressed gas source that is fluidly connected to an air supply control valve that fluidly connects the compressed gas source to the reservoir when the air supply control valve is in an open position.
- the air supply control valve also has a closed position.
- the air supply control valve may be linked to a controller for shifting the air supply control valve between the open and closed positions.
- the pressure regulator may include a reductant pressure control valve that fluidly connects the outlet of the reductant pump to the reservoir when the reductant pressure control valve is in an open position.
- the compressed gas source may be fluidly connected to an air supply control valve.
- the air supply control valve may fluidly connect the compressed gas source to the reservoir when the air supply control valve is in an open position.
- the air supply control valve may also have a closed position and the air supply control valve may be linked to a controller for shifting the air supply control valve between the open and closed positions.
- a method for injecting reductant into an exhaust stream of an engine may include providing a reservoir of reductant fluid and pressurizing the reservoir with a compressed gas source that is fluidly connected to the reservoir through an air supply control valve.
- the method may further include ordering a first dosing event.
- the method may then include pumping reductant fluid from the reservoir to an injector with a reductant pump and regulating a pressure of the reductant fluid that is pumped from the reservoir to the injector. If the pressure of the reductant fluid pumped from the reservoir to the injector is below a first predetermined value, the method further includes opening the air supply control valve. And, if the pressure of the reductant fluid pumped from the reservoir to the injector is above a predetermined value, the method may further include closing the air supply control valve.
- FIG. 1 is a perspective view of an exemplary disclosed power system.
- FIG. 2 is a schematic illustration of the power system of FIG. 1 , particularly illustrating the disclosed reductant dosing system.
- FIGS. 1 and 2 illustrate an exemplary power system 10 having an engine 11 and a reductant dosing system 12 .
- the engine 11 may be an internal combustion engine operable to combust fuel and produce a mechanical power outlet and a flow of exhaust.
- the exhaust from the engine 11 may be directed through an aftertreatment system 13 before being released to the atmosphere.
- the aftertreatment system 13 may include the use of a reduction catalyst configured to reduce a constituent of the exhaust in the presence of a reductant to an acceptable level before the exhaust is discharged to the atmosphere.
- Such aftertreatement systems like that shown at 13 in FIG. 1 are often referred to as selective catalytic reduction (SCR) systems or modules.
- the reductant dosing system 12 may be configured to supply the correct amount of reductant utilized for the reduction process that occurs within the SCR module or aftertreatment system 13 .
- the engine 11 may be associated with a generator 14 that converts mechanical power of the engine 11 into electrical power.
- the engine 11 and generator 14 may together form a stationary generator set.
- the engine 11 and generator 14 may together embody the prime mover of a mobile machine, for example a locomotive.
- the engine 11 may be used without a generator 14 , for example in vehicular applications, pumping applications, and marine applications.
- the reductant fluid may be an aqueous urea solution (e.g., 32.5 wt % urea, 67.5 wt % water), or DEF. In some applications, the urea content may reach 40 wt %.
- the reductant dosing system 12 may be configured to spray or otherwise advance reductant fluid into the exhaust 15 upstream of the aftertreatment system 13 to produce a reducing chemical reaction.
- the urea solution may decompose into ammonia (NH 3 ) that is used to convert NO x (NO and NO 2 ) in the exhaust 15 of the engine 11 to diatomic nitrogen (N 2 ) and water (H 2 O).
- the reductant dosing system 12 may include a reductant injector 16 disposed upstream or at the aftertreatment system 13 , a reductant reservoir 17 and a compressed gas source 18 associated with the engine 11 and configured to supply pressurized air to the reductant reservoir 17 .
- a diesel particulate filter (DPF) 19 may be disposed upstream of both the reductant injector 16 and the aftertreatment system 13 .
- the reductant injector 16 may include a normally closed directional control valve 24 (hereinafter “injector control valve”) that may be opened when a signal is received at the solenoid 25 from the controller 26 .
- injector control valve normally closed directional control valve 24
- a restriction or an orifice 30 may be disposed between the injector control valve 24 and the aftertreatment module or the aftertreatment system 13 .
- An air supply control valve 27 may be disposed downstream of the compressed gas source 18 .
- the air supply control valve 27 may be a normally closed, two way, two position directional control valve having a solenoid 29 that is linked to the controller 26 .
- the air supply control valve 27 provides communication between the compressed gas source 18 and the reductant reservoir 17 .
- a reservoir safety relief valve 31 may be disposed between the air supply control valve 27 and the reductant reservoir 17 .
- the safety relief valve 31 may be in fluid communication with a muffler or air exhaust silencer 32 .
- a combination air filter and pressure regulator 28 may be disposed in-line between the compressed gas source 18 and the air supply control valve 27 .
- separate components may be used for filtering and pressure regulation, as will be apparent to those skilled in the art.
- a three way, two position valve could be used that vents the reductant reservoir 17 to the atmosphere when the valve is in the non-energized position. In the energized position, communication is provided between the compressed gas source 18 and the reductant reservoir 17 while communication between the atmosphere and the reductant reservoir 17 is blocked.
- Use of such a three way, two position air supply control valve may eliminate the need for the safety relief valve 31 , as will be apparent to those skilled in the art.
- An ambient air pressure sensor 33 may be linked to the controller 26 for purposes of monitoring the ambient air pressure, especially at higher altitudes.
- the compressed gas source 18 and the reductant pump 21 may both be driven or powered by the engine 11 as shown in FIG. 2 .
- the pressure regulator 23 may also include a normally closed directional reductant control valve 34 that provides variable spool positions thereby permitting variable flow through the reductant control valve 34 .
- a pressure at a pump outlet 35 of the reductant pump 21 exceeds a threshold value, pressure in the pilot line 36 shifts the reductant control valve 34 from the closed position shown in FIG. 2 to an open position (not shown) thereby providing communication between the pump outlet 35 and the reductant return line 37 .
- the reductant return line 37 is in communication with the reductant reservoir 17 .
- the reductant control valve 34 remains closed and the pump outlet 35 is in communication with the line 38 that leads to reductant injector 16 or, more specifically, the injector control valve 24 .
- the pump outlet 35 is in communication with the backflow line 39 in addition to the reductant return line 37 .
- the backflow line 39 is in communication with the pilot line 41 . If pressure in the backflow line 39 and therefore the pilot line 41 reaches a threshold value, the reductant control valve 34 will shift back to the closed position shown in FIG. 2 . This happens when there is sufficient pressure in the reductant reservoir 17 so that the fluid pressure in the reductant return line 37 and backflow line 39 are sufficient to close the reductant control valve 34 . In contrast, when pressure in the lines 37 , 39 are insufficient to close the reductant control valve 34 , the pressure at the pump outlet 35 is communicated to the pilot line 36 to shift the reductant control valve 34 to an open position.
- the pressure in the line 38 should be sufficient for an injection event.
- Reductant fluid is communicated from the pump outlet 35 , through the line 38 , past the reductant fluid pressure sensor 42 and to the injector control valve 24 of the reductant injector 16 . If the pressure in the line 38 is sufficient for an injection event, as measured by the reducant fluid pressure sensor 42 and communicated to the controller 26 , the controller 26 sends a signal to the solenoid 25 of the injector control valve 24 to open the injector control valve 24 , thereby providing communication between the line 38 and the restriction or orifice 30 .
- Fluid is sprayed through the orifice 30 and into the line 43 which leads to the aftertreatment system 13 , which, in turn, is in communication with the atmosphere 44 .
- the injector control valve 24 When the injector control valve 24 is closed, fluid in the line 38 is routed through the orifice 50 and the return line 60 back to the reductant reservoir 17 .
- the engine 11 is coupled to an air intake 45 , which is in communication with the atmosphere 44 .
- Air from the air intake 45 is combined with fuel in the engine 11 and combusted to produce an exhaust 15 .
- the exhaust 15 may pass through an aftertreatment device, such as a DPF 19 , before the exhaust stream makes its way to the aftertreatment system 13 and before it is released to the atmosphere 44 .
- Air from the atmosphere 44 may also be drawn through an air filter 46 and into the compressed gas source 18 .
- the compressed gas source 18 may be driven by the engine 11 .
- the compressed gas source 18 includes an compressor outlet 47 that may be in direct communication with an air supply control valve 27 or an air filter and/or a pressure regulator, both of which are shown at 28 , may be disposed between the compressor outlet 47 and the air supply control valve 27 .
- a pressure sensor 48 may be used to sense the pressure in the reductant reservoir 17 and the pressure sensor 48 may be linked to the controller 26 . When the pressure in the reductant reservoir 17 is below a desired threshold, the controller 26 may send a signal to the solenoid 29 of the air supply control valve 27 thereby shifting the air supply control valve 27 from the closed position shown at FIG.
- a pressure relief valve 51 may be provided that may be manual, as shown, or may be activated by the controller 26 .
- the reductant pump 21 may draw fluid from the reductant reservoir 17 , through the filter 22 and through the pump outlet 35 .
- the pump outlet 35 may be in communication with the line 38 as well as the pressure regulator 23 . If the pressure in the line 38 and the pilot line 36 is below a certain threshold, the reductant control valve 34 may remain in the closed position as shown in FIG. 2 and fluid may be communicated through the line 38 towards the reductant injector 16 . If the reductant pressure in the line 38 and the pilot line 36 rise above the threshold level, the pressure in the pilot line 36 may shift the reductant control valve 34 to an open position, thereby recirculating reductant from the pump outlet 35 , through the reductant return line 37 and back to the reductant reservoir 17 .
- the controller 26 may send a signal to the solenoid 25 of the injector control valve 24 , thereby shifting the injector control valve 24 to an open position (not shown) and causing reductant from the line 38 , through the injector control valve 24 and through the orifice 30 and to the line 43 that leads to the aftertreatment system 13 .
- the pump outlet 35 may be in communication with an anti-backflow check valve 52 .
- the check valve 52 may be disposed in the backflow line 39 and opposite the orifice 53 from the pilot line 41 . With the reductant control valve 34 in the closed position as shown in FIG. 2 , fluid from the pump outlet 35 may flow past the check valve 52 and through the orifice 53 to the backflow line 39 , which is in communication with the reductant return line 37 .
- the check valve 52 and the orifice 53 are useful for purging the reductant dosing system 12 .
- the check valve 52 prevents air in the lines 39 or 37 from passing through the check valve back towards the reductant pump 21 , which would prevent a complete purge.
- a compressed gas source in the form of a compressed gas source 18 and air supply control valve 27 may be connected to the reductant reservoir 17 .
- a pressure regulator 28 with or without filtering capabilities, may be included to control the pressure of the air delivered to the reductant reservoir 17 . Increased pressure in the reductant reservoir 17 increases the boiling point of the reductant fluid above expected operating temperatures.
- a safety relief valve 31 may also be included to relieve pressure in the reductant reservoir 17 , for safety purposes, such as when the power system 10 is moving from high to low altitudes.
- a manual or automatic pressure relief valve 51 may be included so that the reductant reservoir 17 may be safely filled.
- the pressure regulator 23 insures that fluid flowing towards the reductant injector 16 through the line 38 is at an appropriate pressure for an injection. If the pressure in the line 38 is too high, the reductant control valve 34 is opened and reductant fluid is returned to the reductant reservoir 17 . If the pressure in the line 38 is not excessive, the reductant control valve 34 remains closed and reductant fluid is delivered to the injector control valve 24 , which may be opened by the controller 26 to create an injection event.
- a disclosed method for injecting reductant into an exhaust stream of an engine may include providing a reductant reservoir 17 of reductant fluid.
- the method may further include pressurizing the reductant reservoir 17 using a compressed gas source 18 that is fluidly connected to the reductant reservoir 17 through an air supply control valve 27 .
- the method may further include ordering a first dosing event, which may be carried out by the controller 26 .
- the method then further includes pumping reductant fluid from the reductant reservoir 17 to a reductant injector 16 with a reductant pump 21 .
- the method may further include regulating a pressure of the reductant fluid pumped from the reductant reservoir 17 to the reductant injector 16 and, if the pressure of the reductant fluid pumped from the reductant reservoir 17 to the reductant injector 16 is below a first predetermined value, the method includes opening the air supply control valve 27 . If the pressure of the reductant fluid pumped from the reductant reservoir 17 to the reductant injector 16 is above a second predetermined value, the method may include closing the air supply control valve 27 . Finally, the method may include injecting reductant fluid through the reductant injector 16 and into the aftertreatment system 13 .
- the method may further include opening the reductant control valve 34 when the pressure of the reductant fluid being delivered to the reductant injector 16 rises above a predetermined value and recirculating reductant fluid from the reductant pump 21 back to the reductant reservoir 17 .
- the controller 26 may be in communication with the air supply control valve 27 , the injector control valve 24 , the pressure sensor 48 and the ambient air pressure sensor 33 .
- the pilot actuated reductant control valve 34 may also be replaced by a solenoid valve that is linked to the controller 26 .
- the controller 26 may embody a single or multiple microprocessors, field programmable gate arrays (FPGAs), digital signal processors (DSPs), etc. that include a means for controlling an operation of the reductant dosing system 12 in response to signals received from the sensors 48 , 33 and valves 27 , 24 , as well as other signals from the engine 11 , the aftertreatment system 13 and possibly the DPF 19 .
- Numerous commercially available microprocessors can be configured to perform the functions of the controller 26 .
- controller 26 could readily embody a microprocessor separate from that controlling other non-exhaust related functions, or that the controller 26 could be integral with a general power system microprocessor and be capable of controlling numerous power system functions and modes of operation. If separate from the general power system microprocessor, the controller 26 may communicate with the general power system microprocessor via data links or other methods that will be apparent to those skilled in the art. Various other circuits may be associated with the controller 26 , including power supply circuitry, signal-conditioning circuitry, actuator driver circuitry (i.e., circuitry powering solenoids, motors or piezo actuators), and communication circuitry.
- actuator driver circuitry i.e., circuitry powering solenoids, motors or piezo actuators
- one or more heaters may be associated with the reductant reservoir 17 to avoid freezing of the reductant fluid.
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Abstract
Description
- 1. Technical Field
- This disclosure is directed to exhaust systems for internal combustion engines that include reductant dosing systems. More specifically, the disclosed reductant dosing systems are less prone to pressure pulsations and can operate at high altitudes and at high temperatures without significant vaporization or boiling of the reductant fluid.
- 2. Description of the Related Art
- Internal combustion engines include diesel, gasoline, gaseous fuel-powered and other engines known in the art. These engines produce a complex mixture of emissions. These emissions include gaseous compounds such as oxides of nitrogen, NO and NO2, or collectively, NOx. In atmospheric chemistry, the term NOx means the total concentration of NO and NO2. Due to increased environmental awareness, the amount of NOx emitted to the atmosphere by an engine is regulated depending on the type, size and/or class of the engine.
- In order to comply with the regulation of NOx emissions, some engine manufacturers have implemented a strategy called selective catalytic reduction (SCR). SCR is an exhaust treatment process where a reductant, most commonly urea ((NH2)2CO) or a water/urea solution, is selectively injected into the exhaust gas stream of an engine and adsorbed onto a downstream substrate. The adsorbed urea decomposes into ammonia (NH3), which reacts with NOx in the exhaust gas to form water (H2O) and diatomic nitrogen (N2).
- Reductant dosing systems may be used to introduce the reductant, e.g., urea, into the exhaust stream. In one example, an aqueous urea solution may be stored in a tank. The aqueous urea solution or reductant fluid may be referred to as DEF (diesel exhaust fluid), and may consist of about 32.5 wt % urea and about 67.5 wt % water.
- As the power system or engine operates and produces exhaust, DEF is pumped from the tank and intermittently sprayed into the exhaust stream via an injector. Some reductant dosing systems control the DEF pressure by varying the pump speed while simultaneously monitoring the DEF pressure. However, such a reductant dosing system can produce pressure pulsations, which cannot be accurately controlled by modifying the pump speed. Further, the pressure drop in the pump suction line in combination with operation at high altitudes (low ambient pressure) and/or high temperatures can result in significant vaporization or boiling of the DEF. Vaporization or boiling of the DEF may result in a mixture of vapor and fluid entering the pump, which prevents accurate dosing of the DEF into the exhaust stream.
- CN 101818675 avoids relying upon modifying the pump speed by eliminating the pump altogether and pressurizing the DEF tank. While, such a system without a pump is applicable to passenger vehicles with diesel engines, reliance upon a pressurized DEF tank alone, without a pump, may not be suitable for larger diesel power systems, such as those for trucks, generators, construction equipment, mining equipment, etc.
- In one aspect, a reductant dosing system for an engine is disclosed. The disclosed reductant dosing system may include a reservoir that accommodates a reductant fluid. The reservoir may be fluidly connected to an inlet of a reductant pump. The reductant pump may have an outlet that is fluidly connected to the reservoir, as well as to an inlet of a pressure regulator and to an inlet of an injector. The pressure regulator may include a reductant pressure control valve that fluidly connects the outlet of the reductant pump to the reservoir when the reductant pressure control valve is in an open position. The system may further include a compressed gas source that is fluidly connected to an air supply control valve that fluidly connects the compressed gas source to the reservoir when the air supply control valve is in an open position. The air supply control valve also has a closed position. The air supply control valve may be linked to a controller for shifting the air supply control valve between the open and closed positions.
- In another aspect, a power source is disclosed. The disclosed power source includes an engine that is connected to an exhaust system. The exhaust passes through a selective catalytic reduction (SCR) module. The exhaust may also be fluidly connected to a reductant dosing system disposed upstream of the SCR module. The reductant dosing system may include a reservoir that accommodates reductant fluid, a compressed gas source and a reductant pump. The compressed gas source and reductant pump may be coupled to and driven by the engine. The reservoir may be fluidly connected to an inlet of the reductant pump. The reductant pump may have an outlet that may be fluidly connected to the reservoir, as well as to an inlet of a pressure regulator and to an inlet of an injector. The pressure regulator may include a reductant pressure control valve that fluidly connects the outlet of the reductant pump to the reservoir when the reductant pressure control valve is in an open position. The compressed gas source may be fluidly connected to an air supply control valve. The air supply control valve may fluidly connect the compressed gas source to the reservoir when the air supply control valve is in an open position. The air supply control valve may also have a closed position and the air supply control valve may be linked to a controller for shifting the air supply control valve between the open and closed positions.
- In yet another aspect, a method for injecting reductant into an exhaust stream of an engine is disclosed. The disclosed method may include providing a reservoir of reductant fluid and pressurizing the reservoir with a compressed gas source that is fluidly connected to the reservoir through an air supply control valve. The method may further include ordering a first dosing event. The method may then include pumping reductant fluid from the reservoir to an injector with a reductant pump and regulating a pressure of the reductant fluid that is pumped from the reservoir to the injector. If the pressure of the reductant fluid pumped from the reservoir to the injector is below a first predetermined value, the method further includes opening the air supply control valve. And, if the pressure of the reductant fluid pumped from the reservoir to the injector is above a predetermined value, the method may further include closing the air supply control valve.
- Other advantages and features will be apparent from the following detailed description when read in conjunction with the attached drawings.
- For a more complete understanding of the disclosed methods and apparatuses, reference should be made to the embodiments illustrated in greater detail in the accompanying drawings, wherein:
-
FIG. 1 is a perspective view of an exemplary disclosed power system. -
FIG. 2 is a schematic illustration of the power system ofFIG. 1 , particularly illustrating the disclosed reductant dosing system. - It should be understood that the drawings are not necessarily to scale and that the disclosed embodiments are sometimes illustrated diagrammatically and in partial views. In certain instances, details which are not necessary for an understanding of the disclosed methods and apparatuses or which render other details difficult to perceive may have been omitted. It should be understood, of course, that this disclosure is not limited to the particular embodiments illustrated herein.
-
FIGS. 1 and 2 illustrate anexemplary power system 10 having anengine 11 and areductant dosing system 12. Theengine 11 may be an internal combustion engine operable to combust fuel and produce a mechanical power outlet and a flow of exhaust. The exhaust from theengine 11 may be directed through anaftertreatment system 13 before being released to the atmosphere. In one example, theaftertreatment system 13 may include the use of a reduction catalyst configured to reduce a constituent of the exhaust in the presence of a reductant to an acceptable level before the exhaust is discharged to the atmosphere. Such aftertreatement systems like that shown at 13 inFIG. 1 are often referred to as selective catalytic reduction (SCR) systems or modules. Thereductant dosing system 12 may be configured to supply the correct amount of reductant utilized for the reduction process that occurs within the SCR module oraftertreatment system 13. - It is contemplated that the
engine 11 may be associated with agenerator 14 that converts mechanical power of theengine 11 into electrical power. In one embodiment, theengine 11 andgenerator 14 may together form a stationary generator set. In another embodiment, theengine 11 andgenerator 14 may together embody the prime mover of a mobile machine, for example a locomotive. In yet another embodiment, theengine 11 may be used without agenerator 14, for example in vehicular applications, pumping applications, and marine applications. If theengine 11 is a diesel engine, the reductant fluid may be an aqueous urea solution (e.g., 32.5 wt % urea, 67.5 wt % water), or DEF. In some applications, the urea content may reach 40 wt %. - As shown in
FIG. 2 , thereductant dosing system 12 may be configured to spray or otherwise advance reductant fluid into theexhaust 15 upstream of theaftertreatment system 13 to produce a reducing chemical reaction. At temperatures higher than about 250° C., the urea solution may decompose into ammonia (NH3) that is used to convert NOx (NO and NO2) in theexhaust 15 of theengine 11 to diatomic nitrogen (N2) and water (H2O). Thereductant dosing system 12 may include areductant injector 16 disposed upstream or at theaftertreatment system 13, areductant reservoir 17 and acompressed gas source 18 associated with theengine 11 and configured to supply pressurized air to thereductant reservoir 17. In some embodiments, a diesel particulate filter (DPF) 19 may be disposed upstream of both thereductant injector 16 and theaftertreatment system 13. Thereductant injector 16 may include a normally closed directional control valve 24 (hereinafter “injector control valve”) that may be opened when a signal is received at the solenoid 25 from thecontroller 26. A restriction or anorifice 30 may be disposed between theinjector control valve 24 and the aftertreatment module or theaftertreatment system 13. - The compressed
gas source 18 may be an air compressor as indicated inFIG. 2 , or the compressed gas source may be provided by a turbocharger in the form of compressed air or compressed exhaust. Also, the compressedgas source 18 may be a compressed gas container, such as a CO2 or N2 bottle or reservoir or any other convenient source of compressed gas, as will be apparent to those skilled in the art. - An air
supply control valve 27 may be disposed downstream of the compressedgas source 18. The airsupply control valve 27 may be a normally closed, two way, two position directional control valve having asolenoid 29 that is linked to thecontroller 26. In response to a signal received from thecontroller 26, the airsupply control valve 27 provides communication between thecompressed gas source 18 and thereductant reservoir 17. A reservoirsafety relief valve 31 may be disposed between the airsupply control valve 27 and thereductant reservoir 17. Thesafety relief valve 31 may be in fluid communication with a muffler orair exhaust silencer 32. A combination air filter andpressure regulator 28 may be disposed in-line between thecompressed gas source 18 and the airsupply control valve 27. Of course, separate components may be used for filtering and pressure regulation, as will be apparent to those skilled in the art. - Instead of the two way, two position air
supply control valve 27 shown inFIG. 2 , a three way, two position valve (not shown) could be used that vents thereductant reservoir 17 to the atmosphere when the valve is in the non-energized position. In the energized position, communication is provided between thecompressed gas source 18 and thereductant reservoir 17 while communication between the atmosphere and thereductant reservoir 17 is blocked. Use of such a three way, two position air supply control valve may eliminate the need for thesafety relief valve 31, as will be apparent to those skilled in the art. - An ambient
air pressure sensor 33 may be linked to thecontroller 26 for purposes of monitoring the ambient air pressure, especially at higher altitudes. The compressedgas source 18 and thereductant pump 21 may both be driven or powered by theengine 11 as shown inFIG. 2 . - The
pressure regulator 23 may also include a normally closed directionalreductant control valve 34 that provides variable spool positions thereby permitting variable flow through thereductant control valve 34. When a pressure at apump outlet 35 of thereductant pump 21 exceeds a threshold value, pressure in thepilot line 36 shifts thereductant control valve 34 from the closed position shown inFIG. 2 to an open position (not shown) thereby providing communication between thepump outlet 35 and thereductant return line 37. As shown inFIG. 2 , thereductant return line 37 is in communication with thereductant reservoir 17. In contrast, when the fluid pressure at thepump outlet 35 is insufficient to shift thereductant control valve 34 to the open position, thereductant control valve 34 remains closed and thepump outlet 35 is in communication with theline 38 that leads toreductant injector 16 or, more specifically, theinjector control valve 24. - Returning to the
reductant control valve 34, when thereductant control valve 34 is open, thepump outlet 35 is in communication with thebackflow line 39 in addition to thereductant return line 37. Thebackflow line 39 is in communication with thepilot line 41. If pressure in thebackflow line 39 and therefore thepilot line 41 reaches a threshold value, thereductant control valve 34 will shift back to the closed position shown inFIG. 2 . This happens when there is sufficient pressure in thereductant reservoir 17 so that the fluid pressure in thereductant return line 37 andbackflow line 39 are sufficient to close thereductant control valve 34. In contrast, when pressure in thelines reductant control valve 34, the pressure at thepump outlet 35 is communicated to thepilot line 36 to shift thereductant control valve 34 to an open position. - With the
reductant control valve 34 in the closed position as shown inFIG. 2 , the pressure in theline 38 should be sufficient for an injection event. Reductant fluid is communicated from thepump outlet 35, through theline 38, past the reductantfluid pressure sensor 42 and to theinjector control valve 24 of thereductant injector 16. If the pressure in theline 38 is sufficient for an injection event, as measured by the reducantfluid pressure sensor 42 and communicated to thecontroller 26, thecontroller 26 sends a signal to the solenoid 25 of theinjector control valve 24 to open theinjector control valve 24, thereby providing communication between theline 38 and the restriction ororifice 30. Fluid is sprayed through theorifice 30 and into theline 43 which leads to theaftertreatment system 13, which, in turn, is in communication with theatmosphere 44. When theinjector control valve 24 is closed, fluid in theline 38 is routed through theorifice 50 and thereturn line 60 back to thereductant reservoir 17. - Referring to the bottom of
FIG. 2 , in operation, theengine 11 is coupled to anair intake 45, which is in communication with theatmosphere 44. Air from theair intake 45 is combined with fuel in theengine 11 and combusted to produce anexhaust 15. Theexhaust 15 may pass through an aftertreatment device, such as aDPF 19, before the exhaust stream makes its way to theaftertreatment system 13 and before it is released to theatmosphere 44. - Air from the
atmosphere 44 may also be drawn through anair filter 46 and into the compressedgas source 18. The compressedgas source 18 may be driven by theengine 11. The compressedgas source 18 includes ancompressor outlet 47 that may be in direct communication with an airsupply control valve 27 or an air filter and/or a pressure regulator, both of which are shown at 28, may be disposed between thecompressor outlet 47 and the airsupply control valve 27. Apressure sensor 48 may be used to sense the pressure in thereductant reservoir 17 and thepressure sensor 48 may be linked to thecontroller 26. When the pressure in thereductant reservoir 17 is below a desired threshold, thecontroller 26 may send a signal to thesolenoid 29 of the airsupply control valve 27 thereby shifting the airsupply control valve 27 from the closed position shown atFIG. 2 to an open position (not shown) thereby charging thereductant reservoir 17 with pressure. When the pressure in thereductant reservoir 17 reaches a threshold value, the airsupply control valve 27 may shift back to its normally closed position shown inFIG. 2 . To safely refill thereductant reservoir 17 with reductant, pressure should be released from thereductant reservoir 17. To accomplish this, apressure relief valve 51 may be provided that may be manual, as shown, or may be activated by thecontroller 26. - With sufficient reductant in the
reductant reservoir 17, thereductant pump 21 may draw fluid from thereductant reservoir 17, through thefilter 22 and through thepump outlet 35. Thepump outlet 35 may be in communication with theline 38 as well as thepressure regulator 23. If the pressure in theline 38 and thepilot line 36 is below a certain threshold, thereductant control valve 34 may remain in the closed position as shown inFIG. 2 and fluid may be communicated through theline 38 towards thereductant injector 16. If the reductant pressure in theline 38 and thepilot line 36 rise above the threshold level, the pressure in thepilot line 36 may shift thereductant control valve 34 to an open position, thereby recirculating reductant from thepump outlet 35, through thereductant return line 37 and back to thereductant reservoir 17. If the pressure in theline 38 is sufficient and an injection event is requested, upon thecontroller 26 receiving a pressure reading from the reductantfluid pressure sensor 42, thecontroller 26 may send a signal to the solenoid 25 of theinjector control valve 24, thereby shifting theinjector control valve 24 to an open position (not shown) and causing reductant from theline 38, through theinjector control valve 24 and through theorifice 30 and to theline 43 that leads to theaftertreatment system 13. - Returning to the
pressure regulator 23, thepump outlet 35 may be in communication with ananti-backflow check valve 52. Thecheck valve 52 may be disposed in thebackflow line 39 and opposite theorifice 53 from thepilot line 41. With thereductant control valve 34 in the closed position as shown inFIG. 2 , fluid from thepump outlet 35 may flow past thecheck valve 52 and through theorifice 53 to thebackflow line 39, which is in communication with thereductant return line 37. Thecheck valve 52 and theorifice 53 are useful for purging thereductant dosing system 12. Thecheck valve 52 prevents air in thelines reductant pump 21, which would prevent a complete purge. - To prevent boiling or limit vaporization of reductant fluid (or DEF) at high altitudes and/or high temperatures, a compressed gas source in the form of a compressed
gas source 18 and airsupply control valve 27 may be connected to thereductant reservoir 17. Apressure regulator 28, with or without filtering capabilities, may be included to control the pressure of the air delivered to thereductant reservoir 17. Increased pressure in thereductant reservoir 17 increases the boiling point of the reductant fluid above expected operating temperatures. Asafety relief valve 31 may also be included to relieve pressure in thereductant reservoir 17, for safety purposes, such as when thepower system 10 is moving from high to low altitudes. A manual or automaticpressure relief valve 51 may be included so that thereductant reservoir 17 may be safely filled. Thepressure regulator 23 insures that fluid flowing towards thereductant injector 16 through theline 38 is at an appropriate pressure for an injection. If the pressure in theline 38 is too high, thereductant control valve 34 is opened and reductant fluid is returned to thereductant reservoir 17. If the pressure in theline 38 is not excessive, thereductant control valve 34 remains closed and reductant fluid is delivered to theinjector control valve 24, which may be opened by thecontroller 26 to create an injection event. - A disclosed method for injecting reductant into an exhaust stream of an engine may include providing a
reductant reservoir 17 of reductant fluid. The method may further include pressurizing thereductant reservoir 17 using a compressedgas source 18 that is fluidly connected to thereductant reservoir 17 through an airsupply control valve 27. The method may further include ordering a first dosing event, which may be carried out by thecontroller 26. The method then further includes pumping reductant fluid from thereductant reservoir 17 to areductant injector 16 with areductant pump 21. The method may further include regulating a pressure of the reductant fluid pumped from thereductant reservoir 17 to thereductant injector 16 and, if the pressure of the reductant fluid pumped from thereductant reservoir 17 to thereductant injector 16 is below a first predetermined value, the method includes opening the airsupply control valve 27. If the pressure of the reductant fluid pumped from thereductant reservoir 17 to thereductant injector 16 is above a second predetermined value, the method may include closing the airsupply control valve 27. Finally, the method may include injecting reductant fluid through thereductant injector 16 and into theaftertreatment system 13. - In an embodiment, the method may further include opening the
reductant control valve 34 when the pressure of the reductant fluid being delivered to thereductant injector 16 rises above a predetermined value and recirculating reductant fluid from thereductant pump 21 back to thereductant reservoir 17. - The
controller 26 may be in communication with the airsupply control valve 27, theinjector control valve 24, thepressure sensor 48 and the ambientair pressure sensor 33. The pilot actuatedreductant control valve 34 may also be replaced by a solenoid valve that is linked to thecontroller 26. Thecontroller 26 may embody a single or multiple microprocessors, field programmable gate arrays (FPGAs), digital signal processors (DSPs), etc. that include a means for controlling an operation of thereductant dosing system 12 in response to signals received from thesensors valves engine 11, theaftertreatment system 13 and possibly theDPF 19. Numerous commercially available microprocessors can be configured to perform the functions of thecontroller 26. It should be appreciated that thecontroller 26 could readily embody a microprocessor separate from that controlling other non-exhaust related functions, or that thecontroller 26 could be integral with a general power system microprocessor and be capable of controlling numerous power system functions and modes of operation. If separate from the general power system microprocessor, thecontroller 26 may communicate with the general power system microprocessor via data links or other methods that will be apparent to those skilled in the art. Various other circuits may be associated with thecontroller 26, including power supply circuitry, signal-conditioning circuitry, actuator driver circuitry (i.e., circuitry powering solenoids, motors or piezo actuators), and communication circuitry. - In at least one configuration, one or more heaters may be associated with the
reductant reservoir 17 to avoid freezing of the reductant fluid.
Claims (20)
Priority Applications (2)
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US14/245,197 US9140166B1 (en) | 2014-04-04 | 2014-04-04 | Reductant dosing system |
CN201520198884.6U CN204572133U (en) | 2014-04-04 | 2015-04-03 | Reducing agent feeding system |
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US14/245,197 US9140166B1 (en) | 2014-04-04 | 2014-04-04 | Reductant dosing system |
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US9140166B1 US9140166B1 (en) | 2015-09-22 |
US20150283508A1 true US20150283508A1 (en) | 2015-10-08 |
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US14/245,197 Active US9140166B1 (en) | 2014-04-04 | 2014-04-04 | Reductant dosing system |
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DE102017217891A1 (en) * | 2017-10-09 | 2019-04-11 | Robert Bosch Gmbh | Delivery module for conveying a fluid |
CN109989806B (en) * | 2019-03-04 | 2021-02-05 | 中国船舶重工集团公司第七一一研究所 | Diesel engine high-pressure SCR (selective catalytic reduction) ventilation and pressure stabilization system |
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Also Published As
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CN204572133U (en) | 2015-08-19 |
US9140166B1 (en) | 2015-09-22 |
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