System and method for cold engine start

Abstract

The present disclosure provides a system and method for cold starting an engine. Methods and systems for reducing emissions from an internal combustion engine are described. In one example, an electric heater and a selective reduction catalyst are positioned in a passage downstream of a burner, wherein urea can be injected into the selective reduction catalyst to reduce NOx emissions that may be generated by the burner.

Description

Technical Field

[0001] The present description generally relates to methods and systems for starting an internal combustion engine. Background Art

[0002] The burner can be installed in the engine exhaust system, in parallel with the engine and upstream of the engine exhaust aftertreatment device. The burner can heat the engine exhaust aftertreatment device so that the engine emissions can be reduced. However, the burner may also generate selective emissions (e.g., CO, HC and NOx), and these emissions may enter the atmosphere without being converted by the engine exhaust aftertreatment device. Therefore, although the burner can help improve the efficiency of converting engine emissions, it may result in untreated burner emissions. Summary of the invention

[0003] The inventors herein have recognized the above-mentioned disadvantages and have developed an exhaust system for an internal combustion engine, the exhaust system comprising: a burner air pump, the burner air pump selectively supplies air to a burner positioned along a first passage; a bypass passage and a bypass valve, the bypass passage and the bypass valve being arranged in parallel with the burner; a three-way valve, the three-way valve being positioned downstream of the burner along the first passage; an electric heater, the electric heater being positioned downstream of the three-way valve along a second passage; an oxidation catalyst or a three-way catalyst, the oxidation catalyst or the three-way catalyst being positioned downstream of the electric heater along the second passage; a urea injector, the urea injector being positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage; a selective reduction catalyst (SCR), the selective reduction catalyst being positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage; a third passage, the third passage being arranged in parallel with the second passage, the third passage being coupled to the second passage and entering a fourth passage, the fourth passage extending to an engine exhaust passage and being positioned upstream of a group of aftertreatment devices in the engine exhaust passage.

[0004] By arranging the electric heater and the selective reduction catalyst downstream of the burner, it is possible to provide a technical result of reducing untreated burner emissions, so that the engine aftertreatment device can be heated before the engine is started without releasing a larger amount of NOx, CO and HC. Specifically, the burner emission aftertreatment device can be heated to a threshold temperature via an electric heater so that the burner emission products can be treated when the burner is subsequently started. The heat from the burner can then start the engine aftertreatment device before the engine is started. Therefore, the burner emissions and the engine emissions can be treated via separate devices, so that the emissions are treated with higher efficiency. In addition, because the burner emissions are treated via a selective reduction catalyst, the selective reduction catalyst may be more tolerant to higher temperatures than some other types of aftertreatment devices, so the burner can generate higher gas temperatures and supply these gases to the engine aftertreatment device. Higher gas temperatures can reduce the engine aftertreatment device heating time and reduce tailpipe emissions.

[0005] The present description may provide several advantages. Specifically, the method may reduce tailpipe emissions by reducing burner emissions. Additionally, the method may allow the burner to generate higher gas temperatures and reach the engine aftertreatment device, thereby reducing the aftertreatment device heating time. Furthermore, because the method may tolerate higher temperatures, it may improve system robustness.

[0006] The above advantages and other advantages and features of the present specification will be readily apparent from the following detailed description when taken alone or in conjunction with the accompanying drawings.

[0007] It should be understood that the above summary is provided to introduce a series of concepts further described in the detailed description in a simplified form. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to embodiments that address any disadvantages described above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A detailed schematic diagram of an example engine is shown;

[0009] Figure 2 Shows Figure 1 a schematic diagram of an example exhaust system configuration for an example engine;

[0010] Figure 3 Shown according to Figure 4 An example sequence of operations for the method of

[0011] Figure 4 A flow chart of a method for operating an engine and a combustor is shown. DETAILED DESCRIPTION

[0012] The present description relates to operating an engine and exhaust system aftertreatment devices before and during a cold engine start and during operating conditions when the heat output of the engine is low. Figure 1 An example engine is shown in FIG. Figure 2 The Figure 1 An example exhaust system for an engine. Figure 3 It is shown in Figure 4 An example sequence of operations for the method and Figure 1 and Figure 2 system. Figure 4 A method for operating an engine and an aftertreatment system is shown in FIG.

[0013] refer to Figure 1 Internal combustion engine 10 , comprising a plurality of cylinders, is controlled by electronic engine controller 12 , Figure 1 and Figure 2 One of the cylinders is shown in FIG. 1 . The controller 12 Figure 1 and Figure 2 The controller 12 also uses various sensors to receive signals. Figure 1 and Figure 2 Various actuators are used to adjust engine and vehicle operation based on received signals and instructions stored in the controller's memory.

[0014] Engine 10 includes combustion chamber 30 and cylinder walls 32 in which piston 36 is positioned and connected to crankshaft 40. Cylinder head 13 is fastened to engine block 14. Combustion chamber 30 is shown communicating with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. Each intake valve and exhaust valve may be operated by an intake cam 51 and an exhaust cam 53. However, in other examples, the engine may operate the valves via a single camshaft or pushrod. The position of intake cam 51 may be determined by intake cam sensor 55. The position of exhaust cam 53 may be determined by exhaust cam sensor 57. Intake poppet valve 52 may be operated by variable valve activation / deactivation actuator 59. Similarly, exhaust poppet valve 54 may be operated by variable valve activation / deactivation actuator 58. For one or more complete engine cycles (e.g., two engine revolutions), intake poppet valve 52 and exhaust poppet valve 54 may be deactivated and maintained in a closed position, thereby preventing flow into and out of cylinder 30, thereby deactivating cylinder 30. When cylinder 30 is deactivated, fuel flow to cylinder 30 may also be stopped.

[0015] Fuel injector 68 is shown positioned in cylinder head 13 to inject fuel directly into combustion chamber 30, which is known to those skilled in the art as direct injection. Fuel is delivered to fuel injector 68 by a fuel system including fuel tank 26, a low pressure fuel pump (not shown), a high pressure fuel pump 21, a fuel pump flow control valve 25, and a fuel rail (not shown).

[0016] The engine intake system 9 includes an intake manifold 44, a throttle 62, a grid heater 16, a charge air cooler 163, a turbocharger compressor 162, and an intake plenum 42. The intake manifold 44 is shown in communication with an optional electronic throttle 62, which adjusts the position of the throttle plate 64 to control the air flow from the intake plenum 46. The compressor 162 draws air from the intake plenum 42 to supply the plenum 46. The compressor vane actuator 84 adjusts the position of the compressor vanes 19. The exhaust rotates the turbine 164, which is coupled to the turbocharger compressor 162 via a shaft 161. In some examples, a charge air cooler 163 may be provided. In addition, an optional grid heater 16 may be provided to warm the air entering the cylinder 30 when the engine 10 is cold started. The compressor speed may be adjusted by adjusting the position of the turbine variable vane control actuator 78 or the compressor recirculation valve 158. In an alternative example, the wastegate 79 may replace the turbine variable vane control actuator 78 or be used in addition thereto. The turbine variable vane control actuator 78 adjusts the position of the variable geometry turbine vane 166. When the vane is in the open position, the exhaust gas can pass through the turbine 164, supplying little energy to rotate the turbine 164. When the vane 166 is in the closed position, the exhaust gas can pass through the turbine 164 and exert an increased force on the turbine 164. Alternatively, the wastegate 79 or bypass valve may allow the exhaust gas to flow around the turbine 164 so as to reduce the amount of energy supplied to the turbine. The compressor recirculation valve 158 allows the compressed air at the outlet 15 of the compressor 162 to return to the inlet 17 of the compressor 162. Alternatively, the position of the turbine variable vane actuator 78 may be adjusted to change the efficiency of the compressor 162. In this way, the efficiency of the compressor 162 may be reduced so as to affect the flow of the compressor 162 and reduce the possibility of compressor surge. In addition, by returning the air to the inlet 17 of the compressor 162, the work performed on the air can be increased, thereby raising the temperature of the air. An optional motor 165 is also shown coupled to the shaft 161. When the engine 10 is not rotating, when the engine 10 is rotating at a low speed (e.g., a cranking speed such as 250 RPM), or when the exhaust energy is low, the optional motor 165 can rotate the compressor 162 to provide additional boost. Air flows into the engine 10 in the direction of arrow 5.

[0017] Flywheel 97 and ring gear 99 are coupled to crankshaft 40. Starter 96 (e.g., a low voltage (operating at less than 30 volts) motor) includes pinion shaft 98 and pinion 95. Pinion shaft 98 can selectively advance pinion 95 to engage ring gear 99 so that starter 96 can rotate crankshaft 40 during engine cranking. Starter 96 can be mounted directly to the front of the engine or the rear of the engine. In some examples, starter 96 can selectively supply torque to crankshaft 40 via a belt or chain. In one example, when not engaged to the engine crankshaft, starter 96 is in a basic state. Engine start / stop can be requested via a human / machine interface (e.g., a key switch, a button, a remote radio frequency transmission device, etc.) 69 or in response to vehicle operating conditions (e.g., a foot lever position, a driver demand pedal position, a battery SOC, etc.). Battery 8 can supply power to starter 96 and motor 165. Controller 12 can monitor the battery state of charge.

[0018] Combustion is initiated in combustion chamber 30 when the fuel auto-ignites via the combustion chamber temperature reaching the auto-ignition temperature of the fuel injected into cylinder 30. The temperature in the cylinder increases as piston 36 approaches top dead center compression stroke. In some examples, universal exhaust gas oxygen (UEGO) sensor 126 may be coupled to exhaust manifold 48 upstream of aftertreatment device 71. In other examples, the UEGO sensor may be positioned downstream of one or more exhaust aftertreatment devices. Further, in some examples, the UEGO sensor may be replaced by a NOx sensor having both a NOx sensing element and an oxygen sensing element.

[0019] At lower engine temperatures, optional glow plug 66 can convert electrical energy into thermal energy to create a hot spot next to one of the injector's fuel spray cones in combustion chamber 30. By creating a hot spot next to the injected fuel in combustion chamber 30, the fuel spray plume in the cylinder can be more easily ignited, thereby releasing heat that propagates throughout the cylinder, raising the temperature in the combustion chamber, and improving combustion. Cylinder pressure can be measured via optional pressure sensor 67, which can alternatively or additionally sense cylinder temperature.

[0020] In one example, aftertreatment device 71 may include an oxidation catalyst, and may be followed by a diesel particulate filter (DPF) 72 and a selective catalytic reduction (SCR) catalyst 73. In another example, DPF 72 may be positioned downstream of SCR catalyst 73. Temperature sensor 70 provides an indication of SCR temperature. Exhaust flows in the direction of arrow 7. Burner system 199 may supply heated air to the aftertreatment devices via a passage or conduit 198 upstream of aftertreatment devices 71 to 73 and downstream of turbine 164. Passage or conduit 198 may merge into exhaust passage or conduit 185.

[0021] Exhaust gas recirculation (EGR) may be provided to the engine via a high pressure EGR system 83. The high pressure EGR system 83 includes an EGR valve 80, an EGR passage 81, and an EGR cooler 85. The EGR valve 80 is a valve that blocks or allows exhaust gas to flow from upstream of the aftertreatment device 71 to a location in the engine intake system downstream of the compressor 162. The EGR may be cooled by passing through the EGR cooler 85. EGR may also be provided via a low pressure EGR system 75. The low pressure EGR system 75 includes an EGR passage 77 and an EGR valve 76. The low pressure EGR may flow from downstream of the aftertreatment device 71 to a location upstream of the compressor 162. The low pressure EGR system 75 may include an EGR cooler 74.

[0022] The controller 12 Figure 1 1 is shown as a conventional microcomputer, including: a microprocessor unit 102, input / output ports 104, read-only memory (eg, non-transitory memory) 106, random access memory 108, keep alive memory 110, and a conventional data bus. Controller 12 is shown receiving various signals from sensors coupled to engine 10 in addition to those signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114; position sensor 134 coupled to driver demand pedal 130 for sensing driver demand pedal position adjusted by a person's foot 132; a measurement of engine manifold pressure (MAP) from pressure sensor 121 coupled to intake manifold 44 (alternatively or additionally, pressure sensor 121 may sense intake manifold temperature); boost pressure from pressure sensor 122; exhaust oxygen content from oxygen sensor 126; engine position sensor from engine position sensor 118 sensing position of crankshaft 40; a measurement of air mass entering the engine from sensor 120 (e.g., a hot wire air flow meter); and a measurement of throttle position from sensor 60. Barometric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present description, engine position sensor 118 produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined.

[0023] The controller 12 may receive data and requests from a remote device 86 external to the vehicle to which the controller and engine belong. The remote device 86 may be a key fob, a cloud server, a phone, or other device. The request may include an engine cold start preparation request, an engine start request, etc.

[0024] During operation, each cylinder within engine 10 typically undergoes a four-stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During the intake stroke, generally, exhaust valve 54 is closed and intake valve 52 is opened. Air is introduced into combustion chamber 30 via intake manifold 44, and piston 36 moves to the bottom of the cylinder to increase the volume within combustion chamber 30. The position of piston 36 near the bottom of the cylinder and at the end of its stroke (e.g., when combustion chamber 30 is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). During the compression stroke, intake valve 52 and exhaust valve 54 are closed. Piston 36 moves toward the cylinder head to compress the air within combustion chamber 30. The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when combustion chamber 30 is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In some examples, fuel may be injected into a cylinder multiple times during a single cylinder cycle.

[0025] In a process hereinafter referred to as ignition, the injected fuel is ignited by compression ignition, resulting in combustion. During the expansion stroke, the expanding gases push piston 36 back to BDC. Crankshaft 40 converts piston movement into rotational torque of the rotating shaft. Finally, during the exhaust stroke, exhaust valve 54 opens to release the combusted air-fuel mixture to exhaust manifold 48, and the piston returns to TDC. It should be noted that the above is described only as an example, and the intake and exhaust valve opening and / or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples. Further, in some examples, a two-stroke cycle may be used instead of a four-stroke cycle.

[0026] Reference now Figure 2 , shows a detailed schematic diagram of the burner system 199. Electrical connections are shown via dashed lines. Components including conduits or passages are shown via solid lines. The burner system 199 can supply heated air and / or combustion gases to heat the engine aftertreatment devices 71 to 73. The controller 12 can adjust the operating states of the valves, injectors, pumps, igniters, and burners to operate the burner system 199.

[0027] The burner system includes a burner air pump 202 that supplies fresh air to the burner 208 via a passage 250 and a burner flow control valve 204. A bypass passage or conduit 251 is arranged in parallel with the burner 208. The passage or conduit 251 allows fresh air to mix with the output gas of the burner 208. In this way, the passage or conduit 251 allows dilution and cooling of the gas leaving the burner 208. The bypass flow control valve 203 controls the air flow through the bypass passage 251. The burner flow control valve 204 and the bypass flow control valve 203 can be cycled open and closed (e.g., modulated) to control the air flow into the burner 208 and the dilution / cooling of the gas leaving the burner 208 before the gas flows through the three-way valve 210. The bypass valve can provide sufficient air dilution to mix with the output of the burner to maintain the burner exhaust temperature within the burner catalyst temperature threshold under all burner operating conditions.

[0028] Figure 2 The burner system of 208 provides the advantage of adjusting the temperature of the gas entering the three-way valve 210 by controlling the mixing of the fresh air flow from the air pump 202 with the combustion gases exiting the burner 208. This may be beneficial in controlling the temperature of the aftertreatment devices 214 and 216 when the burner 208 is activated (e.g., burning fuel to generate heat).

[0029] Fuel injector 206 may provide fuel to combustor 208 to mix with air, which may be supplied via combustor air pump 202. Igniter 207 may initiate combustion within combustor 208.

[0030] Air or a combination of air and combustion gases may be delivered to three-way valve 210. Three-way valve 210 may be closed in a first position such that flow is prevented through aftertreatment bypass passage or conduit 254 and through burner aftertreatment passage or conduit 252. When three-way valve 210 is in a second position, three-way valve 210 may deliver air and / or combustion gases to passage or conduit 252 instead of passage or conduit 254. When three-way valve 210 is in a third position, three-way valve 210 may deliver air and / or combustion gases to passage or conduit 254 instead of passage or conduit 252.

[0031] The passage or conduit 254 may be referred to as a burner aftertreatment bypass passage or conduit. During conditions where the temperature of the engine aftertreatment devices 71 to 73 exceeds their light-off temperature but the heat output of the engine is low and the temperature of the engine aftertreatment devices 71 to 73 may not be maintained, air or burner byproducts may be directed through the passage or conduit 254 instead of through the burner aftertreatment passage or conduit 252. The electric heater 212, the first aftertreatment device 214 (e.g., a diesel oxidation catalyst or a three-way catalyst), and the selective reduction catalyst 216 (SCR) are positioned along the passage or conduit 252. The aftertreatment devices 214 and 216 may be referred to as burner aftertreatment devices (e.g., a burner oxidation catalyst and a burner SCR) because they are configured to treat burner gases, while the aftertreatment devices 71 to 73 may be referred to as engine aftertreatment devices because they are configured to treat engine exhaust. The passage or conduit 252 and the passage or conduit 254 are combined or merged into the passage or conduit 198 before entering the exhaust passage or conduit 185. When the combustor 208 is operated under high power / warm exhaust conditions, passages 254 may be provided to reduce the likelihood of combustor catalyst degradation.

[0032] The passage or conduit 252 also includes a NOx sensor 230 and a urea injector 232 positioned downstream of the oxidation catalyst 214 and upstream of the selective reduction catalyst 216. The urea injector 232 can be activated to supply urea to the selective reduction catalyst 216 to increase the reduction of NOx to N2 and H2O. Similarly, the exhaust passage or conduit 185 includes a NOx sensor 236 and an optional urea injector 238. The urea injector 232 or urea injector 238 can supply urea 240 to the selective reduction catalyst 73, which can be referred to as an engine selective reduction catalyst because it is configured to reduce NOx from the engine 10. The passage or conduit is arranged to place the burner system 199 in parallel with the engine 10. The exhaust gas and the burner gas flow in the direction indicated by the arrows placed along the passage or conduit.

[0033] Figure 1 and Figure 2The system provides an exhaust system for an internal combustion engine, the exhaust system comprising: a burner air pump, the burner air pump selectively supplies air to a burner positioned along a first passage; a three-way valve, the three-way valve is positioned downstream of the burner along the first passage; an electric heater, the electric heater is positioned downstream of the three-way valve along a second passage; an oxidation catalyst or a three-way catalyst, the oxidation catalyst or the three-way catalyst is positioned downstream of the electric heater along the second passage; a urea injector, the urea injector is positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage; a selective reduction catalyst (SCR), the selective reduction catalyst is positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage; a third passage, the third passage is arranged in parallel with the second passage, the third passage is connected to the second passage and enters a fourth passage, the fourth passage extends to the engine exhaust passage and is positioned upstream of a group of aftertreatment devices in the engine exhaust passage. In the first example, the exhaust system also includes a NOx sensor, the NOx sensor is positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage. In a second example that may include the first example, the exhaust system includes: wherein the engine exhaust passage includes a second oxidation catalyst, a diesel particulate filter, and a second SCR. In a third example that may include one or both of the first and second examples, the exhaust system also includes a second NOx sensor, the second NOx sensor is positioned downstream of the SCR and upstream of the second oxidation catalyst. In a fourth example that may include one or both of the first to third examples, the exhaust system also includes a second urea injector, the second urea injector is positioned downstream of the SCR and upstream of the second oxidation catalyst. In a fifth example that may include one or more of the first to fourth examples, the exhaust system also includes a controller, the controller including executable instructions stored in a non-transitory memory, the instructions causing the controller to start the electric heater, start the burner air pump, and adjust the three-way valve to allow air to flow into the second passage instead of the third passage when the internal combustion engine is not rotating. In a sixth example, which may include one or more of the first to fifth examples, the exhaust system also includes additional executable instructions that cause the controller to: deactivate the electric heater, continue to operate the burner air pump, and inject fuel into the burner in response to the temperature of the oxidation catalyst, the three-way catalyst, or the SCR exceeding a threshold temperature when the internal combustion engine is not rotating.In a seventh example, which may include one or more of the first to sixth examples, the exhaust system further includes executable instructions that cause the controller to inject urea to the SCR in response to output of a NOx sensor positioned along the second passage.

[0034] Reference now Figure 3 , showing the Figure 1 and Figure 2 The basis of the system Figure 4 An example of a method of operating to predict a vehicle operation sequence. Figure 3 The sequence of operations can be Figures 1 to 4 of the system and execute Figure 4 The instructions of the method described are used to generate. Figure 3 The graphs of are aligned in time and occur simultaneously. The vertical marks at t0 to t3 indicate particularly important times during the sequence.

[0035] from Figure 3 The first graph from the top of FIG. 30 is a graph of an aftertreatment preheat request (e.g., a request to preheat an engine aftertreatment device) versus time. The vertical axis denotes the operational state of the aftertreatment preheat request, and when the trace 302 is at a higher level near the vertical axis arrow, the aftertreatment preheat request is asserted. When the trace 302 is at a lower level near the horizontal axis, the aftertreatment preheat request is not asserted. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. The trace 302 represents the operational state of the aftertreatment preheat request.

[0036] from Figure 3 The second graph from the top of FIG. 3 is a graph of engine aftertreatment temperature versus time. The vertical axis represents engine aftertreatment temperature, and engine aftertreatment temperature increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace 304 represents engine aftertreatment temperature. Dashed line 350 represents a threshold engine aftertreatment temperature, such as an engine SCR light-off temperature or an engine oxidation catalyst light-off temperature, where the light-off temperature is the temperature at which the aftertreatment device exhibits a threshold efficiency (e.g., a conversion efficiency of 50 mole % for a particular gas species).

[0037] from Figure 3 The third graph from the top of is a graph of burner air pump operating status versus time. The vertical axis represents the burner air pump status, and the burner air pump is activated when the trace 306 is at a higher level near the vertical axis arrow. When the trace 306 is at a lower level near the horizontal axis, the burner air pump is not activated. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace 306 represents the burner air pump operating status.

[0038] from Figure 3 The fourth graph from the top of is a graph of the electric heater operating state versus time. The vertical axis represents the electric heater operating state, and the electric heater is enabled when the trace 308 is at a higher level near the vertical axis arrow. When the trace 308 is at a lower level near the horizontal axis, the electric heater is not enabled. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. The trace 308 represents the electric heater operating state.

[0039] from Figure 3 The fifth graph from the top of is a graph of burner SCR temperature versus time. The vertical axis represents burner SCR temperature, and the burner SCR temperature increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace 310 represents the burner SCR temperature. Dashed line 352 represents the threshold burner SCR temperature, where the light-off temperature is the temperature at which the burner SCR exhibits a threshold efficiency (e.g., 50 mole % conversion efficiency of NOx).

[0040] from Figure 3 The sixth graph from the top of is a graph of burner operating state versus time. The vertical axis represents the burner operating state, and when the trace 312 is at a higher level near the vertical axis arrow, the burner is activated (e.g., burning fuel and generating heat). When the trace 312 is at a lower level near the horizontal axis, the burner is not activated. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. The trace 312 represents the burner operating state.

[0041] from Figure 3 The seventh graph from the top of FIG. 3 is a graph of urea injector operating state versus time. The vertical axis represents the urea injector operating state, and when the trace 314 is at a higher level near the vertical axis arrow, the urea injector is activated (e.g., urea is injected). When the trace 314 is at a lower level near the horizontal axis, the urea injector is not activated. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. The trace 314 represents the urea injector operating state.

[0042] from Figure 3 The eighth graph from the top of is a graph of engine operating state versus time. The vertical axis represents the engine operating mode, and when the trace 316 is at a higher level near the vertical axis arrow, the engine is started (e.g., burning fuel and spinning). When the trace 316 is at a lower level near the horizontal axis, the engine is not started. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. The trace 316 represents the engine operating state.

[0043] At time t0, the engine is stopped and aftertreatment preheat is not requested. The engine aftertreatment temperature is low and the burner air pump is off or disabled. The electric heater is off and the burner SCR temperature is below its light-off temperature. The burner is not activated and the urea injector is not activated.

[0044] At time t1, the engine aftertreatment preheat request is asserted, which causes the burner air pump to be started together with the electric heater. These actions allow the heated fresh air to warm up the burner oxidation catalyst and SCR. In addition, the engine aftertreatment device can also be heated via the electric heater. One or more valves (not shown) (e.g., 203 and 210) can be adjusted to allow air to flow to the burner aftertreatment device. The burner, urea injector, and engine remain closed so that the engine does not generate exhaust gas. The burner SCR temperature begins to rise, and the engine aftertreatment device also begins to slowly heat up.

[0045] At time t2, the burner SCR temperature reaches its threshold temperature. Therefore, the electric heater is deactivated and the burner is activated because the burner emissions can be processed and because the burner generates more heat than the electric heater. Therefore, the burner is activated to start the engine aftertreatment device. The burner air pump remains activated so that oxygen is provided to the burner and heat can be transferred from the burner to the engine aftertreatment device. The engine aftertreatment device temperature begins to increase at a faster rate, and the burner SCR temperature continues to increase. Compared with other emission devices, the burner SCR can tolerate higher temperatures before it may begin to deteriorate, so it can process the NOx gas from the burner and allow additional heat to be transferred to the engine aftertreatment device. The burner is started via supplying fuel to the burner. In addition, the igniter at the burner can initiate combustion in the burner. The urea injector is also activated so that the injected urea can improve the NOx conversion efficiency of the burner SCR. The engine remains deactivated.

[0046] At time t3, the engine aftertreatment device temperature reaches its threshold temperature (e.g., engine aftertreatment light-off temperature). Therefore, the engine is started and the burner is deactivated. The burner air pump and urea injector are also deactivated, but the engine aftertreatment urea injector (e.g., 238) may be activated to improve the NOx conversion efficiency of the engine aftertreatment SCR. Because the burner has been deactivated, the electric heater remains off and the burner SCR temperature begins to drop.

[0047] Therefore, the burner SCR temperature can be raised before starting the engine and burner so that when the burner is started, the NOx from the burner can be treated by the SCR at operating temperature. The burner SCR can be smaller in volume than the engine aftertreatment SCR because the NOx output of the burner is less than the NOx output of the engine and so that the burner SCR reaches its light-off temperature more quickly. Once the burner SCR has reached its operating temperature, the burner can be started to increase heating of the engine aftertreatment device. When the engine aftertreatment device has reached its threshold temperature, the engine can be started.

[0048] Reference now Figure 4 , showing a schematic diagram of a method for operating an engine, a single burner and Figure 1 and Figure 2 A method of an engine aftertreatment system of the type shown. Figure 4 The method may be implemented at least in part by storing Figure 1 and Figure 2 In addition, Figure 4 The method may include actions taken by the controller in the physical world to transform Figure 1 and Figure 2 The operating status of the system. Figure 4 The method can provide Figure 3 Method 400 may begin when the vehicle's engine is stopped and not rotating.

[0049] At 402 , method 400 judges whether or not a modification to an engine aftertreatment device (eg, Figure 1 71 to 73) for preheating. If so, the answer is yes and method 400 proceeds to 404. Otherwise, the answer is no and method 400 proceeds to exit. In one example, a request to preheat the engine aftertreatment system may be generated in preparation for vehicle startup. The request to preheat the engine aftertreatment device may be generated by a vehicle operator, a cloud server, or other device. For example, a request to preheat the engine aftertreatment device may be generated in response to a person or device entering the vicinity of the device or based on a planned vehicle departure time.

[0050] At 404 , method 400 judges whether the engine aftertreatment device temperature is above a threshold temperature (eg, catalyst light-off temperature or SCR light-off temperature). If yes, the answer is yes and method 400 proceeds to 440 . If no, the answer is no and method 400 proceeds to 406 .

[0051] At 440, method 400 determines whether an engine start request has been generated. The engine start request may be generated via opening a door, turning a key, applying a button, sending a signal via an electronic device (e.g., a phone, a tablet, etc.). If method 400 determines that an engine start has been requested, the answer is yes, and method 400 proceeds to 442. Otherwise, the answer is no, and method 400 returns to 402.

[0052] At 442, method 400 starts the engine by cranking the engine and supplying fuel to the engine. The burner air pump is disabled, the electric heater is disabled, the burner is disabled, and the burner urea injector is disabled. The burner air pump can be electrically driven, and the controller can stop supplying power to the burner air pump, the electric heater (e.g., Figure 2 212 ) delivers current, stops fuel flow to the burner, and commands the burner urea injector (e.g., 232 ) to close. Method 400 may be responsive to an engine NOx sensor (e.g., Figure 2 The output of 236) activates the engine urea injector (for example, Figure 2 238). Because the engine aftertreatment temperature is above the engine aftertreatment light-off temperature, engine emissions at and after engine restart may be treated via the engine aftertreatment device. After the engine is started, engine exhaust (e.g., NOx, CO, HC) flows to the engine aftertreatment device. Additionally, valves 203, 204, and 210 may be positioned to prevent engine exhaust from flowing to the burner 208 and the burner air pump 202 after the engine is started and the temperature of the engine aftertreatment device exceeds a threshold temperature. Method 400 proceeds to exit.

[0053] At 406, method 400 determines whether the burner SCR temperature (e.g., the temperature of the burner SCR) is greater than a threshold temperature (e.g., the light-off temperature of the burner SCR). Alternatively, method 400 may determine whether the burner oxidation catalyst temperature or the three-way catalyst temperature is greater than a threshold temperature (e.g., the light-off temperature of the burner oxidation catalyst). If so, the answer is yes, and method 400 proceeds to 408. Otherwise, the answer is no, and method 400 proceeds to 430.

[0054] At 430, method 400 starts the burner air pump and the electric heater. Method 400 may also adjust valves 204, 203, and 210 so that air flows from burner air pump 202 to electric heater 212 and oxidation catalyst 214. These actions allow fresh air that has been warmed by the electric heater to warm burner oxidation catalyst 214, burner SCR, and engine aftertreatment devices 71 to 73. Method 400 returns to 402.

[0055] At 408 , method 400 may start a combustor air pump (eg, Figure 2 202), deactivate the electric heater, and start the burner (e.g., Figure 2 208), and start the burner urea injector (e.g., Figure 2 218). Method 400 may start a burner air pump to supply fresh air to the burner and push combustion gases toward the burner oxidation catalyst, the burner SCR, and the engine aftertreatment device. The burner is started to generate heat and warm up the engine aftertreatment device so that they can effectively treat the engine exhaust when the engine is started. Because the burner oxidation catalyst and the burner SCR are at their respective light-off temperatures, NOx, HC, and CO that may be generated by starting the burner may be effectively treated. The burner may be started by injecting fuel into the burner and burning the fuel via an igniter or an existing flame. A urea injector may be started to cause urea, a reductant, to flow to the burner SCR, where the burner NOx may be reduced to N2 and H2O. The urea flow through the urea injector may be based on or in response to a NOx sensor (e.g., Figure 2 The method 400 proceeds to 410 .

[0056] At 410 , method 400 judges whether the engine SCR (eg, Figure 1 73) has reached a threshold temperature (e.g., the light-off temperature of the engine SCR). If yes, the answer is yes, and method 400 proceeds to 434. If no, the answer is no and method 400 proceeds to 412.

[0057] At 434, method 400 deactivates the burner air pump, deactivates the electric heater, deactivates the burner, and deactivates the burner urea injector. The burner air pump, electric heater, burner, and urea injector are deactivated to save energy and urea. Method 400 returns to 402. Because the engine SCR is up to temperature, the engine can be started at 442. The burner air pump, electric heater, and urea injector (e.g., Figure 2 The burners can be deactivated by stopping the flow of fuel to the burners.

[0058] At 412 , method 400 judges whether the combustor SCR temperature is above a maximum SCR temperature threshold. If so, the answer is yes and method 400 proceeds to 414 . Otherwise, the answer is no and method 400 returns to 408 .

[0059] At 414 , method 400 keeps the burner air pump activated, opens the bypass valve, deactivates the electric heater, deactivates the burner, and deactivates the urea injector (eg, Figure 2The burner is deactivated to reduce the possibility of burner SCR degradation. Method 400 proceeds to 416.

[0060] At 416, method 400 determines whether the temperature of the burner SCR is below the burner low temperature threshold. If so, the answer is yes, and method 400 returns to 408, where the burner can be restarted. Otherwise, the answer is no, and method 400 returns to 402.

[0061] In this way, method 400 can selectively activate the electric heater to activate the oxidation catalyst and the burner SCR so that when the burner is activated, its combustion byproducts can be treated. The burner can be activated to heat the engine aftertreatment device so that when the engine is started, the engine combustion byproducts can be treated. This sequence can reduce tailpipe emissions of selected gases (e.g., HC, CO, and NOx).

[0062] therefore, Figure 4 A method for operating an engine is provided, comprising: in response to starting a burner or an output of a NOx sensor in a passage downstream of the burner, starting a first injector via a controller to supply urea to a first selective reduction catalyst, the burner being arranged in parallel with the engine; and supplying urea to the second selective reduction catalyst in response to NOx flowing to the second selective reduction catalyst, the second selective reduction catalyst being arranged in the exhaust system of the engine. In a first example, the method includes wherein NOx flows to the second selective reduction catalyst via the engine. In a second example that may include the first example, the method includes: wherein the urea supplied to the second selective reduction catalyst is supplied via the first injector. In a third example that may include one or both of the first and second examples, the method includes: wherein the urea supplied to the second selective reduction catalyst is supplied via the second injector. In a fourth example that may include one or more of the first to third examples, the method includes: wherein the NOx flowing to the second selective reduction catalyst is sensed via a second NOx sensor. In a fifth example, which may include one or more of the first to fourth examples, the method further includes: preventing engine exhaust from flowing to the second selective reduction catalyst in response to a temperature of an aftertreatment device in the exhaust system. In a sixth example, which may include one or more of the first to fifth examples, the method includes: wherein the first injector, the first selective reduction catalyst, and the NOx sensor are positioned along the passage, and wherein the passage is fluidly coupled to the burner via a three-way valve.

[0063] Figure 4The method also provides a method for operating an engine, the method comprising: heating an oxidation catalyst and a selective reduction catalyst via an electric heater in response to the engine start request before starting the engine and the burner; starting the burner in response to an oxidation catalyst temperature or a selective reduction catalyst temperature; generating heat and NOx via the burner, the burner being arranged in parallel with the engine and coupled to the engine via a passage and an engine exhaust system; and reducing the NOx via injected urea and the selective reduction catalyst. In a first example, the method further comprises: raising the temperature of a catalyst in an engine exhaust system via the heat; starting the engine in response to the temperature exceeding a threshold temperature; and reducing the NOx generated by the engine via a second selective reduction catalyst included in the engine exhaust system. In a second example that may include the first example, the method further comprises: injecting urea upstream of the second selective reduction catalyst in response to the NOx generated by the engine. In a third example that may include one or both of the first and second examples, the method comprises: wherein the urea is injected via an injector positioned upstream of the selective reduction catalyst. In a fourth example, which may include one or more of the first to third examples, the method includes wherein the urea is injected via an injector positioned upstream of the second selective reduction catalyst and downstream of the selective reduction catalyst.

[0064] It should be noted that the example control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and programs disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system including a controller in combination with various sensors, actuators and other engine hardware. In addition, parts of the method can be physical actions taken in the real world to change the state of the device. The specific routines described herein may represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). To this end, the various actions, operations and / or functions shown may be performed in the order described, performed in parallel, or omitted in some cases. Similarly, the processing order is not necessarily required to achieve the features and advantages of the exemplary examples described herein, but is provided for ease of illustration and description. One or more of the actions, operations and / or functions shown may be repeatedly performed according to the specific strategy used. In addition, the described actions, operations and / or functions may graphically represent code programmed into a non-transitory memory of a computer-readable storage medium in an engine control system, wherein the described actions are performed by executing the instructions in conjunction with an electronic controller in a system including various engine hardware components. If desired, one or more of the method steps described herein may be omitted.

[0065] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific examples should not be considered limiting, as numerous variations are possible. For example, the above techniques may be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0066] The appended claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims may be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also deemed to be included in the subject matter of the present disclosure.

[0067] According to the present invention, an exhaust system for an internal combustion engine is provided, the exhaust system having: a burner air pump, the burner air pump selectively supplies air to a burner positioned along a first passage; a three-way valve, the three-way valve being positioned downstream of the burner along the first passage; an electric heater, the electric heater being positioned downstream of the three-way valve along a second passage; an oxidation catalyst or a three-way catalyst, the oxidation catalyst or the three-way catalyst being positioned downstream of the electric heater along the second passage; a urea injector, the urea injector being positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage; a selective reduction catalyst (SCR), the selective reduction catalyst being positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage; and a third passage, the third passage being arranged in parallel with the second passage, the third passage being connected to the second passage and entering a fourth passage, the fourth passage extending to an engine exhaust passage and being positioned upstream of a group of aftertreatment devices in the engine exhaust passage.

[0068] According to an embodiment, the present invention is also characterized by a NOx sensor positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage.

[0069] According to an embodiment, the engine exhaust passage comprises a second oxidation catalyst, a diesel particulate filter and a second SCR.

[0070] According to an embodiment, the invention is also characterized by a second NOx sensor positioned downstream of the SCR and upstream of the second oxidation catalyst.

[0071] According to an embodiment, the invention is also characterized by a second urea injector, which is positioned downstream of the SCR and upstream of the second oxidation catalyst.

[0072] According to an embodiment, the present invention is also characterized by a controller, which includes executable instructions stored in a non-transitory memory, and the executable instructions cause the controller to start the electric heater, start the burner air pump, and adjust the three-way valve to allow air to flow into the second channel instead of the third channel when the internal combustion engine is not rotating.

[0073] According to an embodiment, the present invention is also characterized by additional executable instructions, which cause the controller to: deactivate the electric heater, continue to operate the burner air pump, and inject fuel into the burner in response to the temperature of the oxidation catalyst, the three-way catalyst or the SCR exceeding a threshold temperature when the internal combustion engine is not rotating.

[0074] According to an embodiment, the invention also features executable instructions that cause the controller to inject urea to the SCR in response to output of a NOx sensor positioned along the second passage.

[0075] According to the present invention, a method for operating an engine includes: in response to starting a burner or an output of a NOx sensor in a passage downstream of the burner, starting a first injector via a controller to supply urea to a first selective reduction catalyst, the burner being arranged in parallel with the engine; and in response to NOx flowing to a second selective reduction catalyst, supplying urea to the second selective reduction catalyst, the second selective reduction catalyst being arranged in an exhaust system of the engine.

[0076] In an aspect of the present invention, NOx flows to the second selective reduction catalyst via the engine.

[0077] In an aspect of the present invention, urea supplied to the second selective reduction catalyst is supplied via the first injector.

[0078] In one aspect of the present invention, urea supplied to the second selective reduction catalyst is supplied via a second injector.

[0079] In an aspect of the present invention, the NOx flowing to the second selective reduction catalyst is sensed via a second NOx sensor.

[0080] In one aspect of the present invention, the method includes preventing engine exhaust gas from flowing to the second selective reduction catalyst in response to a temperature of an aftertreatment device in the exhaust system.

[0081] In one aspect of the present invention, the first injector, the first selective reduction catalyst, and the NOx sensor are positioned along the passage, and wherein the passage is fluidly coupled to the burner via a three-way valve.

[0082] According to the present invention, a method for operating an engine includes: heating an oxidation catalyst and a selective reduction catalyst via an electric heater in response to an engine start request before starting the engine and a burner; starting the burner in response to an oxidation catalyst temperature or a selective reduction catalyst temperature; generating heat and NOx via the burner, the burner being arranged in parallel with the engine and coupled to the engine via a passage and an engine exhaust system; and reducing the NOx via injected urea and the selective reduction catalyst.

[0083] In one aspect of the present invention, the method includes: increasing the temperature of a catalyst in the engine exhaust system via the heat; starting the engine in response to the temperature exceeding a threshold temperature; and reducing engine-generated NOx via a second selective reduction catalyst included in the engine exhaust system.

[0084] In one aspect of the present invention, the method includes injecting urea upstream of the second selective reduction catalyst in response to engine-generated NOx.

[0085] In one aspect of the present invention, the urea is injected via an injector positioned upstream of the selective reduction catalyst.

[0086] In an aspect of the present invention, the urea is injected via an injector positioned upstream of the second selective reduction catalyst and downstream of the selective reduction catalyst.

Claims

1. An exhaust system for an internal combustion engine, comprising: a burner air pump that selectively supplies air to a burner positioned along the first passage; a three-way valve positioned downstream of the burner along the first passage; an electric heater positioned downstream of the three-way valve along the second passage; an oxidation catalyst or a three-way catalyst, the oxidation catalyst or the three-way catalyst being positioned downstream of the electric heater along the second passage; a urea injector, the urea injector being positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage; a selective reduction catalyst (SCR) positioned downstream of the oxidation catalyst or the three-way catalyst along the second passage; A third passage is arranged in parallel with the second passage, the third passage is coupled to the second passage and enters a fourth passage extending to the engine exhaust passage and positioned upstream of a group of aftertreatment devices in the engine exhaust passage. 2 . The exhaust system of claim 1 , further comprising a NOx sensor positioned along the second passage downstream of the oxidation catalyst or the three-way catalyst.

3. The exhaust system of claim 2, wherein the engine exhaust passage includes a second oxidation catalyst, a diesel particulate filter, and a second SCR. 4 . The exhaust system of claim 3 , further comprising a second NOx sensor positioned downstream of the SCR and upstream of the second oxidation catalyst. 5 . The exhaust system of claim 4 , further comprising a second urea injector positioned downstream of the SCR and upstream of the second oxidation catalyst.

6. The exhaust system of claim 1 , further comprising a controller including executable instructions stored in a non-transitory memory, the instructions causing the controller to activate the electric heater, activate the burner air pump, and adjust the three-way valve to allow air to flow into the second passage instead of the third passage when the internal combustion engine is not rotating.

7. The exhaust system of claim 6, further comprising additional executable instructions that cause the controller to: The electric heater is deactivated, the burner air pump is continuously operated, and fuel is injected into the burner in response to a temperature of the oxidation catalyst, the three-way catalyst, or the SCR exceeding a threshold temperature when the internal combustion engine is not rotating.

8. The exhaust system of claim 7, further comprising executable instructions that cause the controller to: Urea is injected into the SCR in response to output of a NOx sensor positioned along the second passage.

9. A method for operating an engine, comprising: activating a first injector via a controller to supply urea to a first selective reduction catalyst in response to activating a burner or an output of a NOx sensor in a passage downstream of the burner, the burner being arranged in parallel with the engine; as well as Urea is supplied to a second selective reduction catalyst in response to NOx flowing to the second selective reduction catalyst, the second selective reduction catalyst being arranged in an exhaust system of the engine.

10. The method of claim 9, wherein NOx flows to the second selective reduction catalyst via the engine. 11 . The method of claim 10 , wherein urea supplied to the second selective reduction catalyst is supplied via the first injector. 12 . The method of claim 10 , wherein the urea supplied to the second selective reduction catalyst is supplied via a second injector. 13 . The method of claim 9 , wherein the NOx flowing to the second selective reduction catalyst is sensed via a second NOx sensor.

14. The method of claim 9, further comprising: Engine exhaust is prevented from flowing to the second selective reduction catalyst in response to a temperature of an aftertreatment device in the exhaust system.

15. The method of claim 9, wherein the first injector, the first selective reduction catalyst, and the NOx sensor are positioned along the passage, and wherein the passage is fluidly coupled to the burner via a three-way valve.

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