US20090301068A1 - Exhaust-gas purification apparatus and method for purifying exhaust gas - Google Patents

Exhaust-gas purification apparatus and method for purifying exhaust gas Download PDF

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Publication number
US20090301068A1
US20090301068A1 US12/478,870 US47887009A US2009301068A1 US 20090301068 A1 US20090301068 A1 US 20090301068A1 US 47887009 A US47887009 A US 47887009A US 2009301068 A1 US2009301068 A1 US 2009301068A1
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United States
Prior art keywords
urea water
exhaust
reducing agent
particle size
temperature
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US12/478,870
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English (en)
Inventor
Tatsuya Fujita
Masatoshi Maruyama
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Denso Corp
Soken Inc
Original Assignee
Denso Corp
Nippon Soken Inc
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Assigned to DENSO CORPORATION, NIPPON SOKEN, INC. reassignment DENSO CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MARUYAMA, MASATOSHI, FUJITA, TATSUYA
Publication of US20090301068A1 publication Critical patent/US20090301068A1/en
Abandoned legal-status Critical Current

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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
    • 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
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/04—Methods of control or diagnosing
    • F01N2900/0408—Methods of control or diagnosing using a feed-back loop
    • 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
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1602—Temperature of exhaust gas apparatus
    • 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

  • the present invention relates to an exhaust-gas purification apparatus for an exhaust gas purification system such as a selective catalytic reduction (SCR) system having a selective reduction catalyst for selectively purifying nitrogen oxide (NOx) in exhaust gas of an internal combustion engine by charging ammonia as a reducing agent.
  • SCR selective catalytic reduction
  • NOx nitrogen oxide
  • the present SCR system generally employs a urea aqueous solution as a reducing agent, and such an SCR system is known as a urea SCR system.
  • the present invention relates to a method for purifying exhaust gas of the internal combustion engine.
  • a urea SCR system is employed as an exhaust-gas-purification system for an engine such as a diesel engine for a vehicle such as an automobile so as to purify NOx in exhaust gas of at a high purification rate.
  • a conventional urea SCR system has the following structure.
  • a selective reduction type NOx catalyst is provided in an exhaust pipe, which is connected to a main body of an engine.
  • a urea water charge valve is further provided in the exhaust pipe at an upstream of the NOx catalyst for charging urea water (urea aqueous solution) as a NOx reducing agent.
  • the urea water charge valve charges urea water into the exhaust pipe so as to selectively perform reductive reaction and removal of NOx, which is contained in exhaust gas, on the NOx catalyst.
  • NOx which is contained in exhaust gas
  • urea water is hydrolyzed by thermal energy of exhaust-gas to produce ammonia (NH3), and thereby the ammonia is absorbed into the NOx catalyst to cause reductive reaction on the NOx catalyst.
  • NH3 ammonia
  • JP-A-2007-255343 proposes an art to accelerate evaporation and diffusion of a reducing agent, which is charged from a urea water charge valve into an exhaust pipe, so as to enhance a NOx purification performance of a NOx catalyst.
  • a shielding member is provided in the exhaust passage at an upstream of the NOx catalyst in an exhaust-gas flow, and a depurator is injected to a downstream of the shielding member so as to accelerate atomization of the depurator.
  • the depurator injected into the exhaust passage collides with the distribution member, and thereby further atomized.
  • the shielding member and the distribution member increase pressure loss in the exhaust passage.
  • the pressure loss in the exhaust passage is regularly caused during an operation of the engine, and consequently the engine is exerted with an adverse effect such as increase in fuel consumption.
  • the exhaust-gas flow varies in response to an operation state of the engine. For example, an amount of intake air and exhaust gas increases when the engine is in a high load operation state. In such a high load operation state, pressure loss caused by the shielding member and the distribution member in the exhaust passage becomes large, and consequently fuel consumption is increased.
  • an object of the present invention to produce an exhaust-gas-purification apparatus for controlling a reducing agent charged to enhance a NOx purification rate of an internal combustion engine and configured to restrict an adverse influence to the internal combustion engine. It is another object of the present invention to produce a method for purifying exhaust gas of the internal combustion engine.
  • an exhaust-gas purification apparatus for an exhaust-gas-purification system for an internal combustion engine, the system including a NOx catalyst, which is provided in an exhaust passage of the internal combustion engine for selectively purifying NOx in exhaust gas with a reducing agent, charging means, which is for charging the reducing agent into exhaust gas at an upstream of the NOx catalyst, and pressurizing means, which is for pressurizing the reducing agent and supplying the reducing agent to the charging means, the exhaust-gas purification apparatus comprises obtaining means for detecting or estimating catalyst temperature of the NOx catalyst or temperature information, which is correlated with the catalyst temperature.
  • the exhaust-gas purification apparatus further comprises particle size control means for changing reducing-agent pressure of reducing agent, which is pressurized by the pressurizing means and supplied to the charging means, to control an atomized particle size of the reducing agent, which is atomized from the charging means and charged into exhaust gas, based on the catalyst temperature or the temperature information.
  • a method for purifying exhaust gas of an internal combustion engine comprises detecting or estimating catalyst temperature of a NOx catalyst, which is provided in an exhaust passage of the internal combustion engine for selectively purifying NOx in exhaust gas with a reducing agent, or temperature information, which is correlated with the catalyst temperature.
  • the method further comprises manipulating reducing-agent pressure of reducing agent, which is charged into exhaust gas at an upstream of the NOx catalyst, to control an atomized particle size of the reducing agent based on the catalyst temperature or the temperature information.
  • FIG. 1 is an over view showing an engine control system according to an embodiment of the present invention
  • FIG. 2 is a graph showing a relationship between a NOx purification rate of an SCR catalyst, an SCR catalyst temperature, and an atomized particle size of urea water;
  • FIG. 3 is a graph showing a relationship between a urea water pressure and the atomized particle size of urea water
  • FIG. 4 is a flow chart showing a urea water charge control
  • FIG. 5 is a graph showing a relationship between an amount of urea water charge, the urea water pressure, and an opening period of a urea water charge valve, and
  • FIG. 6 is a time chart showing the urea water control.
  • an engine control system controls a multi-cylinder diesel engine for a vehicle as a controlled object.
  • an electronic control unit ECU
  • a common-rail fuel injection system is employed as a fuel injection system
  • a urea SCR system is employed as an exhaust-gas-purification system.
  • An engine 10 includes an engine main body 11 , which has a reciprocating engine structure.
  • a piston 12 is movable back and forth in a cylinder of the engine main body 11 .
  • An intake valve 13 and an exhaust valve 14 are respectively and correspondingly provided to an intake port and an exhaust port for opening and closing the intake port and the exhaust port.
  • a crankshaft 15 is rotatable in response to the movement of the piston 12 .
  • a fuel injection valve 16 is provided for each cylinder in the cylinder head. The fuel injection valve 16 directly injects fuel into a combustion chamber 17 , and the injected fuel is burned in the combustion chamber 17 .
  • a crank angle sensor 18 is provided to the crankshaft 15 for detecting rotation of the crankshaft 15 .
  • a temperature sensor 19 is provided to the cylinder block for detecting temperature of engine cooling water.
  • the fueling system may have a generally known structure, and therefore detailed description of the fueling system with reference to drawings is omitted.
  • the fueling system includes a high-pressure pump and a common rail (accumulator pipe).
  • the high-pressure pump pressurizes fuel drawn from a fuel tank and press-feeds the pressurized fuel to a common rail.
  • the common rail accumulates high-pressure fuel of several tens to two hundred MPa, and the accumulated high-pressure fuel is supplied to the fuel injection valve 16 of each cylinder. Fuel pressure in the common rail is arbitrarily controlled according to an engine operation state and the like.
  • An intake pipe 21 including a manifold portion is connected to the intake port of the engine main body 11 , and an exhaust pipe 22 including a manifold portion is connected to the exhaust port.
  • a throttle actuator 23 which has an electric throttle valve, is provided in the intake pipe 21 .
  • An EGR passage 24 connects an intake passage in the intake pipe 21 with an exhaust passage in the exhaust pipe 22 .
  • An EGR valve 25 and an EGR cooler 26 are provided in the EGR passage 24 .
  • An air cleaner 27 is provided at the uppermost in the intake pipe 21 .
  • Air flow meter (intake air sensor) 28 is provided in the air cleaner 27 .
  • a turbocharger 30 is provided as a supercharging device in the furling system.
  • the turbocharger 30 includes an air intake compressor 31 , which is provided in the intake pipe 21 , and an exhaust turbine 32 , which is provided in the exhaust pipe 22 .
  • the exhaust turbine 32 is driven by exhaust gas flowing through the exhaust pipe 22 to produce torque, and the torque is transmitted via a shaft 33 to the air intake compressor 31 .
  • the air intake compressor 31 pressurizes intake air flowing through the intake pipe 21 , thereby to supercharge the intake air.
  • the intake air supercharged by the turbocharger 30 is cooled through an intercooler 34 , and thereafter fed to the downstream of the intake pipe 21 .
  • the intake pipe 21 is further provided with sensors such as an intake air pressure sensor and an intake air temperature sensor.
  • an oxidation catalyst 41 a selective catalytic reduction (SCR) catalyst (ammonia selective reduction catalyst) 42 , and an ammonia slip catalyst 43 are sequentially provided from the upstream.
  • the SCR catalyst 42 is equivalent to a NOx catalyst.
  • a urea water charge valve 44 is provided between the oxidation catalyst 41 and the SCR catalyst 42 in the exhaust pipe 22 for charging urea water (urea aqueous solution) as a reducing agent into the exhaust pipe 22 .
  • the urea water charge valve 44 has substantially the same structure as a generally known fuel injection valve (injector) actuated by an electromagnetic power source such as a solenoid.
  • the urea water charge valve 44 opens in response to an electric control instruction, and thereby injecting urea water from a tip end nozzle hole portion of the urea water charge valve 44 .
  • the urea water charge valve 44 is successively supplied with urea water from a urea water tank 51 .
  • the urea water tank 51 is an airtight container provided with a liquid supply cap.
  • the urea water tank 51 stores urea water of predetermined concentration such as 32.5%.
  • the urea water tank 51 is connected with one end of a urea water piping 52 .
  • a urea water pump 53 is provided as a compression unit midway through the urea water piping 52 .
  • the other end of the urea water piping 52 is connected to the urea water charge valve 44 .
  • a pressure sensor 54 is provided in the urea water piping 52 for detecting pressure of urea water in the urea water piping 52 .
  • the urea water pump 53 is an electromotive pump and driven in response to a driving signal transmitted from an ECU 60 .
  • the urea water pump 53 is driven so as to pump urea water from the urea water tank 51 to the urea water charge valve 44 through the urea water piping 52 .
  • the urea water pump 53 is variable in feeding capacity (press-feeding amount) of urea water.
  • the urea water piping 52 is capable of manipulating feed pressure of urea water in response to change in the feeding capacity.
  • the urea water pump 53 may be an in-tank pump immersed in urea water inside the urea water tank 51 .
  • a mixer 55 is provided between the oxidation catalyst 41 and the SCR catalyst 42 in the exhaust pipe 22 for causing swirl flow in exhaust gas flowing through the exhaust pipe 22 .
  • the mixer 55 is an exhaust-gas stirring device, which includes a rotor having multiple vane pieces, for example. The mixer 55 rotates in response to passage of exhaust gas, and thereby swirls exhaust gas flowing into the SCR catalyst 42 .
  • urea water is charged from the urea water charge valve 44 into the exhaust pipe 22 in the engine operation, and thereby urea water is charged together with exhaust gas into the SCR catalyst 42 in the exhaust pipe 22 .
  • NOx causes reductive reaction in the SCR catalyst 42 , and thereby exhaust gas is purified.
  • urea water injected from the urea water charge valve 44 is applied with thermal energy of exhaust-gas and thereby to cause the following reaction (1) and hydrolyzed to produce ammonia (NH3).
  • the charged ammonia selectively causes reduction reaction and purification in NOx in the exhaust gas.
  • the following reduction reactions (2) to (3) are caused.
  • ammonia may be excessive, and surplus ammonia may not cause reaction with NOx.
  • the surplus ammonia is mixed with exhaust gas and emitted downstream of the exhaust gas flow.
  • the surplus ammonia is to be removed by the ammonia slip catalyst 43 at the downstream of the SCR catalyst.
  • the ammonia slip catalyst 43 may be an oxidation catalyst.
  • An oxygen concentration sensor 45 and a temperature sensor 46 are further provided between the oxidation catalyst 41 and the SCR catalyst 42 in the exhaust pipe 22 . The oxygen concentration in exhaust gas and the catalyst temperature are detected based on an output signal of the sensors 45 , 46 .
  • a NOx sensor 47 is provided at the downstream of the SCR catalyst 42 so as to detect an amount of NOx, which relates to the NOx concentration in exhaust gas after passing through the SCR catalyst 42 .
  • a NOx purification rate of the SCR catalyst 42 is detected based on an output signal of the NOx sensor 47 .
  • a diesel particulate filter (DPF not shown) is provided in the exhaust pipe 22 for capturing particulate matter (PM) in exhaust gas.
  • the ECU 60 includes a generally-known microcomputer (not shown) having a CPU, a ROM, a RAM, and the like.
  • the ECU 60 receives the detection signals of a rail pressure sensor, which is for detecting fuel pressure (rail pressure) in the common rail, and an accelerator sensor, which is for detecting manipulation of an accelerator pedal (accelerator position), and the like, in addition to the detection signals of the various sensors.
  • the ECU 60 performs a fuel injection control, a fuel pressure control (rail pressure control), and the like based on engine operation information items including an engine speed, the accelerator position, and the like.
  • an injection operation of the fuel injection valve 16 and a feeding operation of a high-pressure pump are controlled.
  • the ECU 60 arbitrarily controls the throttle actuator 23 , the EGR valve 25 , and the like, based on the engine operation state.
  • the ECU 60 calculates an amount of NOx at the downstream of the SCR catalyst 42 and a NOx purification rate based on the output signal of the NOx sensor 47 .
  • the ECU 60 further controls an amount of urea water to be charged based on the NOx purification rate.
  • the amount of NOx (Y 1 ) emitted from the engine is calculated by using an equation or obtained from a data map based on an engine operation state such as an engine speed and fuel an injection quantity of each time.
  • the amount NOx (Y 2 ) at the downstream of the SCR catalyst 42 is calculated based on the output signal of the NOx sensor 47 .
  • an amount of ammonia adsorption of the SCR catalyst 42 may be calculated, and an amount of urea water to be charged may be controlled based on the amount of ammonia adsorption.
  • an actual amount of ammonia adsorption (actual adsorption) may be calculated based on a balance of charge of ammonia and consumption of ammonia, which is caused by reaction in the SCR catalyst 42 .
  • the amount of urea water to be charged may be feedback-controlled based on a deviation between the actual adsorption and a target value.
  • the ECU 60 outputs an open command pulses to the urea water charge valve 44 at a predetermined cycle.
  • a driving current flows in an actuator portion (solenoid portion) of the urea water charge valve 44 in response to the open command pulses.
  • the urea water charge valve 44 is opened in response to the driving current, and thereby urea water is injected and charged.
  • the amount of urea water to be charged (urea water charge) is controlled by manipulating an output cycle or an output frequency of the open command pulses.
  • the output cycle of the open command pulses is increased so as to decrease the urea water charge.
  • the output cycle of the open command pulses is decreased so as to increase the urea waters charge.
  • the driving current of the urea water charge valve 44 may be terminated for a predetermined time period so as to decrease the urea water charge.
  • FIG. 2 is a graph showing the correlation between the SCR catalyst temperature and the NOx purification rate in the case where the atomized particle size of urea water is changed.
  • the solid line indicates the case where the atomized particle size is 100 micrometers in a normal operation of the pump
  • the two-dot chain line indicates the case where the atomized particle size is 20 micrometers and reduced to produce further microscopic spray than the normal operation.
  • FIG. 2 indicates that when the SCR catalyst temperature is higher than 220° C., the NOx purification rate is saturated at a predetermined high purification rate of about 80%, and the NOx purification performance is substantially constant regardless of the atomized particle size.
  • the SCR catalyst temperature is lower than 220° C., the NOx purification performance is excellent in the condition where the atomized particle size is small. It is conceived that when the temperature of the SCR catalyst 42 is low, urea water spray, which is smaller in the atomized particle size, is tend to obtain thermal energy from exhaust gas therearound, and thereby production of ammonia is accelerated.
  • the saturation temperature of the NOx purification rate is about 220° C.
  • the saturation temperature of the NOx purification rate is about 200° C. That is, the NOx purification rate can be enhanced by using urea spraying of minute particle diameter in a low-temperature range equal to or less than the purification rate saturation temperature of about 220° C. when the particle diameter is 100 micrometers.
  • the NOx purification rate becomes 50% at an activated temperature of the SCR catalyst 42 in the normal charge of urea water of atomized particle size of 100 micrometers. In the present embodiment, the activated temperature of the SCR catalyst 42 is about 180° C.
  • the pressure of urea water (urea water pressure) and the atomized particle size of urea water charged to the urea water charge valve 44 therebetween have a correlation shown in FIG. 3 .
  • FIG. 3 indicates that as the urea water pressure becomes large, the atomized particle size of urea water becomes small. Therefore, in the present embodiment, the amount of urea water press-feed from the urea water pump 53 is manipulated so as to change the urea water pressure, and thereby to control the atomized particle size of urea water.
  • urea water is increased in pressure to be in a compressed state and charged when the SCR catalyst 42 is relatively low in temperature and activity.
  • urea water is decreased in pressure to be in a non-compressed state and charged when the SCR catalyst 42 is relatively high in temperature and activity.
  • atomization of urea water spray is arbitrary controlled by manipulating the urea water pressure, and thereby the NOx purification performance is maintained at a high level.
  • the SCR catalyst 42 is in a predetermined high-temperature state, the NOx purification performance can be maintained at a high level, regardless of the atomized particle size of urea water and pressurization of urea water.
  • the pump load can be reduced by decreasing the urea water pressure. Thereby, power consumption of an in-vehicle battery can be reduced.
  • FIG. 4 is a flow chart showing a procedure of a urea water charge control.
  • the ECU 60 repeats the present urea water charge control operation at a predetermined cycle.
  • step S 11 it is determined whether an engine speed NE is currently greater than a predetermined value K 1 .
  • the predetermined value K 1 is a threshold for determining whether the engine 10 is an operation state. For example, the predetermined value K 1 is 800 rpm.
  • step S 12 it is determined whether an SCR catalyst temperature Tscr is greater than a predetermined value K 2 .
  • the SCR catalyst temperature Tscr is calculated based on an output signal of the temperature sensor 46 at the upstream of the SCR catalyst 42 .
  • the predetermined value K 2 is a temperature threshold for determining whether the SCR catalyst 42 is in a completely activated state or a non-activated state.
  • the predetermined value K 2 is 180° C. In the present embodiment, the temperature of 180° C. is equivalent to the catalyst temperature at which the NOx purification rate of the SCR catalyst 42 becomes 50%.
  • step S 13 it is determined whether the urea water pressure Pn is currently greater than a predetermined value K 3 .
  • the urea water pressure Pn is calculated based on the detection signal of the pressure sensor 54 provided in the urea water piping 52 .
  • the predetermined value K 3 is a pressure threshold for determining whether urea water can be charged from the urea water charge valve 44 .
  • the predetermined value K 3 is a minimum pressure at which urea water can be charged. For example, the predetermined value K 3 is 0.4 MPa.
  • step S 14 the urea water pump 53 is driven at a predetermined rotation speed. Specifically, the urea water pump 53 is driven so as to obtain the urea water pressure Pn greater than the minimum pressure at which urea water can be charged from the urea water charge valve 44 .
  • the predetermined value K 4 is a temperature threshold for determining whether urea water spray is to be microscopically atomized.
  • the predetermined value K 4 is 220° C.
  • the predetermined value K 4 is a purification rate saturation temperature when the atomized particle size is 100 micrometer (refer to FIG. 2 ).
  • the present processing proceeds to step S 16 on condition of Tscr>K 4 .
  • the present processing proceeds to step S 17 on condition of Tscr ⁇ K 4 .
  • the first target pressure PT 1 is set, and the urea water pump 53 is controlled based on the first target pressure PT 1 .
  • the second target pressure PT 2 is set, and the urea water pump 53 is controlled based on the second target pressure PT 2 .
  • the first target pressure PT 1 is a normal urea water pressure.
  • the first target pressure PT 1 is, for example, 0.5 MPa.
  • the second target pressure PT 2 is higher than the first target pressure PT 1 .
  • the second target pressure PT 2 is, for example, 5 MPa.
  • the atomized particle size is set at 100 micrometers by controlling the urea water pressure at the first target pressure PT 1 (0.5 MPa), and the atomized particle size is set at 20 micrometers by controlling the urea water pressure at the second target pressure PT 2 (5 MPa).
  • the first target pressure PT 1 is greater than the predetermined value K 3 (0.4 MPa), which is the minimum pressure at which urea water can be charged.
  • a control parameter of the urea water charge valve 44 is determined. Specifically, an opening period (charge time) of the urea water charge valve 44 in one injection is determined For example, the opening period is determined from the relationship shown in FIG. 5 with reference to the current amount of urea water charge and current urea water pressure. The amount of urea water charge is calculated based on the NOx purification rate or an amount of ammonia adsorption of each time. A charge cycle of urea water may be determined as a control parameter of the urea water charge valve 44 based on the current urea water pressure. A control parameter may be calculated based on the target pressure (PT 1 , PT 2 ) of each time in place of the detection result of the urea water pressure.
  • step S 20 the urea water charge valve 44 charges urea water based on the control parameter determined at step S 19 .
  • FIG. 6 is a time chart for describing the urea water control further in detail according to the present embodiment.
  • (a) shows a transition of the engine speed
  • (b) shows a transition of the SCR catalyst temperature
  • (c) shows a transition of the urea water pressure.
  • the engine 10 is started at the time point t 1 , and an idling operation is performed in the period between t 1 and t 2 .
  • the SCR catalyst receives thermal energy from exhaust-gas, and thereby the SCR catalyst temperature gradually increases.
  • the engine speed increases in response to an operation such as acceleration, and thereby the SCR catalyst temperature starts quickly increasing.
  • the SCR catalyst temperature reaches the predetermined value K 2 (180 ⁇ ), and thereby the urea water pump 53 is operated so as to increase the urea water pressure.
  • the urea water pressure becomes greater than the predetermined value K 3 (0.4 MPa)
  • a control of the urea water pressure at the second target pressure PT 2 (5 MPa) is started.
  • the urea water pressure is increased so as to microscopically atomize urea water and charge the atomized urea in the period between t 3 and t 4 .
  • the target value of the urea water pressure is changed from the second target pressure PT 2 (5 MPa) to the first target pressure PT 1 (0.5 MPa).
  • the urea water pressure is changed to the normal pressure, and thereby normal spray of the urea water without the microscopic atomization is performed in the period between t 4 and t 5 .
  • the SCR catalyst temperature decreases with deceleration of the vehicle and becomes less than or equal to the predetermined value K 4 (220 ⁇ ) at the time point t 5 .
  • the target value of the urea water pressure is again changed to the second target pressure PT 2 (5 MPa), and thus, atomization of urea water spray is performed in the period between t 5 and t 8 .
  • the SCR catalyst temperature becomes less than or equal to the predetermined value K 2 (180 ⁇ ), which is the activated temperature of the SCR catalyst 42 . Therefore, in the period between t 6 and t 7 , urea water charge is temporarily stopped, and the amount of urea water press-fed from the urea water pump 53 is decreased to be significantly small.
  • this embodiment produces the following operation effects.
  • the pressure of urea water pumped from the urea water pump 53 is manipulated based on the SCR catalyst temperature of each time, and thereby the atomized particle size of urea water injected from the urea water charge valve 44 is controlled.
  • the urea water pressure is increased so as to further microscopically atomize urea water and significantly decrease the particle size of urea water.
  • the NOx purification rate can be significantly enhanced by the microscopic atomization and decrease in the atomized particle size of urea water in the predetermined low-temperature range, in which the NOx purification rate of the SCR catalyst 42 is low.
  • the urea water pressure is arbitrary manipulated so as to control the atomized particle size of urea water. Therefore, dissimilarly to the conventional structure, in which a shielding member and a distribution member are provide in the exhaust passage, the engine can be protected from an adverse effect. Consequently, urea water can be charged while an adverse effect to the engine is restricted. Thus, the NOx purification rate can be enhanced.
  • the urea water pressure When the urea water pressure is not increased to as to significantly decrease the atomized particle size, the urea water need not be compressed. Therefore, electricity supplied from the power supply (battery) to the urea water pump 53 can be reduced, and thereby energy consumption can be reduced.
  • the SCR catalyst 42 is in a cold condition immediately after an engine start operation (cold start). In the present condition, increasing in the NOx purification rate is apt to slow. In the present embodiment, the atomized particle size of urea water is significantly decreased immediately after the engine start operation, and thereby increasing in the NOx purification rate can be accelerated. Therefore, the exhaust-gas-purification performance immediately after the engine start operation can be enhanced.
  • urea water is microscopically atomized in the predetermined low-temperature range less than the temperature threshold.
  • the NOx purification rate can be enhanced by microscopically atomizing urea water when the NOx purification rate of the SCR catalyst 42 does not increase to the saturation value in the case where the particle diameter of urea water is large.
  • At least one of the cycle of urea water charge from the urea water charge valve 44 and the charge time in one injection is manipulated according to urea water pressure. Therefore, urea water can be charged by a desirable amount even when the urea water pressure changes.
  • the atomized particle size of urea water is set to be small based on the comparison between the SCR catalyst temperature and the temperature threshold (predetermined value K 4 ).
  • the atomized particle size may be controlled according to progress of time immediately after an engine start operation for a predetermined period. Specifically, in the engine start operation, in particular, in cold engine start, an elapsed time from the engine start operation is measured. Further, the atomized particle size of urea water is set to be small until a predetermined time elapses, and the atomized particle size is increased after the predetermined time period (time threshold) elapses.
  • the time threshold at which the atomized particle size is changed from small to large, may be beforehand determined based on an experimental result and the like or may be manipulated according to a standby condition such as engine water temperature in the engine start operation. According to the present operation, the atomized particle size of urea water can be manipulated in accordance with increase in temperature of the SCR catalyst 42 . Thereby, urea water can be suitably charged.
  • the atomized particle size of urea water is switched in the two steps including 100 micrometers and 20 micrometers.
  • the atomized particle size may be switched in three steps or more.
  • the atomized particle size of urea water may be manipulated in consideration of the amount of urea water charge of each time, in addition to the SCR catalyst temperature. For example, when the amount of urea water charge is large, the urea water pressure is increased so as to decrease the atomized particle size of urea water.
  • the atomized particle size of urea water changes in dependence upon the urea water temperature, in addition to urea water pressure. Therefore, the atomized particle size of urea water may be decreased by heating urea water, in addition to pressurizing urea water using the urea water pump 53 .
  • a heater may be provided in the urea water piping 52 so as to heat urea water when the atomized particle size of urea water is set to be small.
  • atomization of urea water spray can be further accelerated by pressurizing and heating urea water.
  • the urea water pump 53 may have the heater.
  • the SCR catalyst temperature Tscr is detected based on the output signal of the temperature sensor 46 provided at the upstream of the SCR catalyst 42 , and thereby the atomized particle size of urea water is manipulated based on the SCR catalyst temperature Tscr.
  • a sensor or the like may be provided for detecting temperature of exhausted gas of the engine, or the temperature of exhausted gas may be computed and estimated based on an engine operation state.
  • the atomized particle size of urea water may be manipulated based on the temperature of exhaust gas.
  • the temperature of exhaust gas is equivalent to temperature information of the NOx catalyst.
  • the atomized particle size of urea water may be manipulated based on the engine load of each time. Specifically, when the engine load is low, the SCR catalyst temperature decreases as the exhaust gas temperature decreases. Therefore, when the engine load is less than a predetermined value, the atomized particle size of urea water is set to be small.
  • the engine load can be estimated from engine speed, an amount of fuel injection, manipulation of the accelerator pedal, an amount of intake air flow, an amount of NOx exhaust, the exhaust gas temperature, and/or the like.
  • the above technical feature may be applied to a system other than the urea SCR system.
  • the above technical feature may be applied to a system, in which a solid urea is used as an ammonia source so as to produce urea water or ammonia solution as a reducing agent from the solid urea.
  • the above technical feature may be further applied to a system, in which fuel such as light oil is used as an ammonia source, a system, in which an ammonia solution is directly charged into an exhaust passage, a system, in which a reducing agent such as HC other than ammonia is used, and the like.
  • the above processings such as calculations and determinations are not limited being executed by the ECU 60 .
  • the control unit may have various structures including the ECU 60 shown as an example.
  • the above processings such as calculations and determinations may be performed by any one or any combinations of software, an electric circuit, a mechanical device, and the like.
  • the software may be stored in a storage medium, and may be transmitted via a transmission device such as a network device.
  • the electric circuit may be an integrated circuit, and may be a discrete circuit such as a hardware logic configured with electric or electronic elements or the like.
  • the elements producing the above processings may be discrete elements and may be partially or entirely integrated. It should be appreciated that while the processes of the embodiments of the present invention have been described herein as including a specific sequence of steps, further alternative embodiments including various other sequences of these steps and/or additional steps not disclosed herein are intended to be within the steps of the present invention.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
US12/478,870 2008-06-05 2009-06-05 Exhaust-gas purification apparatus and method for purifying exhaust gas Abandoned US20090301068A1 (en)

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US20130199157A1 (en) * 2012-02-02 2013-08-08 Cary Henry Systems and methods for controlling reductant delivery to an exhaust stream
US8701389B2 (en) 2011-12-06 2014-04-22 Tenneco Automotive Operating Company Inc. Reagent injector control system
US8875499B2 (en) 2011-03-18 2014-11-04 Hino Motors Ltd. Urea solution reformer and exhaust gas purifier using same
US20150075270A1 (en) * 2013-09-16 2015-03-19 International Engine Intellectual Property Company, Llc Reductant delivery performance diagnostics system
US20150151251A1 (en) * 2012-03-29 2015-06-04 Volvo Construction Equipment Ab Method for diagnosing a selective catalytic reduction catalyst
WO2014113567A3 (en) * 2013-01-17 2015-11-05 Miratech Group, Llc Method and apparatus for analysis and selective catalytic reduction of nox-containing gas streams
US20160032804A1 (en) * 2013-03-07 2016-02-04 Scania Cv Ab Method pertaining to an scr system and an scr system
US9670812B2 (en) 2012-06-22 2017-06-06 Toyota Jidosha Kabushiki Kaisha Deterioration detection system for exhaust gas purification apparatus
CN107269358A (zh) * 2016-04-04 2017-10-20 劳士领汽车集团 具有阀门配置组件的scr‑设备
US10294845B2 (en) * 2014-08-08 2019-05-21 Isuzu Motors Limited System and method for managing temperature of urea solution
US10900401B2 (en) * 2016-08-17 2021-01-26 Robert Bosch Gmbh Method for detecting a blocked pressure line
US11274583B1 (en) * 2019-11-05 2022-03-15 Sonix Enterprises Inc. Internal combustion engine exhaust modification system
CN114370318A (zh) * 2022-01-19 2022-04-19 潍柴动力股份有限公司 一种减少后处理尿素结晶的方法及汽车
US11480090B2 (en) * 2018-07-19 2022-10-25 Isuzu Motors Limited Exhaust structure for vehicle-mounted engine
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WO2013153606A1 (ja) * 2012-04-09 2013-10-17 トヨタ自動車 株式会社 内燃機関の排気浄化装置
JP2014005742A (ja) * 2012-06-21 2014-01-16 Denso Corp 内燃機関の排気浄化装置
JP2018076801A (ja) * 2016-11-08 2018-05-17 いすゞ自動車株式会社 内燃機関の排気ガス浄化システム
JP2018150851A (ja) * 2017-03-10 2018-09-27 いすゞ自動車株式会社 エンジンの尿素ｓｃｒシステム
JP6939528B2 (ja) * 2017-12-25 2021-09-22 株式会社デンソー 排気浄化制御装置
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US8875499B2 (en) 2011-03-18 2014-11-04 Hino Motors Ltd. Urea solution reformer and exhaust gas purifier using same
US8635854B2 (en) * 2011-08-05 2014-01-28 Tenneco Automotive Operating Company Inc. Reductant injection control system
CN103717850A (zh) * 2011-08-05 2014-04-09 坦尼科汽车操作有限公司 还原喷射控制系统
DE112012003259B4 (de) * 2011-08-05 2020-07-09 Tenneco Automotive Operating Company Inc. Reduktionsmitteleinspritzsteuerungsystem
US20130031890A1 (en) * 2011-08-05 2013-02-07 Shovels Michael L Reductant Injection Control System
US8701389B2 (en) 2011-12-06 2014-04-22 Tenneco Automotive Operating Company Inc. Reagent injector control system
US9222389B2 (en) * 2012-02-02 2015-12-29 Cummins Inc. Systems and methods for controlling reductant delivery to an exhaust stream
US20130199157A1 (en) * 2012-02-02 2013-08-08 Cary Henry Systems and methods for controlling reductant delivery to an exhaust stream
US9492788B2 (en) * 2012-03-29 2016-11-15 Volvo Construction Equipment Ab Method for diagnosing a selective catalytic reduction catalyst
US20150151251A1 (en) * 2012-03-29 2015-06-04 Volvo Construction Equipment Ab Method for diagnosing a selective catalytic reduction catalyst
US9670812B2 (en) 2012-06-22 2017-06-06 Toyota Jidosha Kabushiki Kaisha Deterioration detection system for exhaust gas purification apparatus
WO2014113567A3 (en) * 2013-01-17 2015-11-05 Miratech Group, Llc Method and apparatus for analysis and selective catalytic reduction of nox-containing gas streams
US20160032804A1 (en) * 2013-03-07 2016-02-04 Scania Cv Ab Method pertaining to an scr system and an scr system
US9822686B2 (en) * 2013-03-07 2017-11-21 Scania Cv Ab Method pertaining to an SCR system and an SCR system
US9399942B2 (en) * 2013-09-16 2016-07-26 International Engine Intellectual Property Company, Llc. Reductant delivery performance diagnostics system
US20150075270A1 (en) * 2013-09-16 2015-03-19 International Engine Intellectual Property Company, Llc Reductant delivery performance diagnostics system
US10294845B2 (en) * 2014-08-08 2019-05-21 Isuzu Motors Limited System and method for managing temperature of urea solution
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CN107269358A (zh) * 2016-04-04 2017-10-20 劳士领汽车集团 具有阀门配置组件的scr‑设备
CN107269358B (zh) * 2016-04-04 2020-11-13 劳士领汽车集团 具有阀门配置组件的scr-设备
US10900401B2 (en) * 2016-08-17 2021-01-26 Robert Bosch Gmbh Method for detecting a blocked pressure line
US11480090B2 (en) * 2018-07-19 2022-10-25 Isuzu Motors Limited Exhaust structure for vehicle-mounted engine
US11274583B1 (en) * 2019-11-05 2022-03-15 Sonix Enterprises Inc. Internal combustion engine exhaust modification system
US11591941B2 (en) 2019-11-05 2023-02-28 Sonix Enterprises Inc. Internal combustion engine exhaust modification system
CN114370318A (zh) * 2022-01-19 2022-04-19 潍柴动力股份有限公司 一种减少后处理尿素结晶的方法及汽车

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DE102009026754B4 (de) 2012-04-26

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