DIESEL ENGINE PARTICULATE FILTER REGENERATION PROCESS

Abstract

Particulate filter regeneration process, comprising: Receiving sensor data to a controller (12); and adjusting a post-injection fuel pulse width provided to a second fuel injection device of a cylinder (30) via the controller (12) in response to an amount of internal residue in the cylinder (30) as estimated from the sensor data.

Description

The present invention relates to a particle regeneration process. General state of the art / Summary A diesel engine can incorporate a particulate filter in its exhaust system to capture carbon-based soot, a byproduct of combustion. Over time, the particulate filter can become clogged with soot, significantly reducing emissions. The particulate filter can regenerate by increasing the exhaust temperature and introducing an oxygen-rich exhaust mixture, burning off the accumulated soot. One way to increase exhaust gas temperature is to supply fuel that was not involved in combustion in the engine cylinders to an oxidation catalyst. The fuel is burned in the oxidation catalyst to raise the exhaust gas temperature, which in turn raises the particulate filter temperature, allowing soot in the particulate filter to burn off and thus regenerate it. The fuel can be supplied to the oxidation catalyst by injecting post-injection fuel pulses into a cylinder, allowing the fuel to be expelled from the cylinder during its exhaust stroke. Specifically, expanding combustion gases leave the cylinder containing unburned fuel when the cylinder's exhaust valves open.Most of the fuel injected into the cylinder exits because the overlap between the intake and exhaust valves is small, and the flow of exhaust gases and fuel back into the cylinder is reduced by the closing of the exhaust valve. However, two-stroke diesel engines do not necessarily need to include intake or exhaust valves to prevent exhaust gases and fuel from flowing back into the cylinder when post-injection fuel pulses are provided to facilitate particulate filter regeneration. Furthermore, the exhaust and intake ports of a cylinder in a two-stroke diesel engine can be open simultaneously for a long crankshaft angle duration, allowing exhaust gases and post-injection fuel to be drawn back into the cylinder.Consequently, the post-injection fuel may be involved in combustion in the cylinder during a subsequent cylinder cycle, which may not be desirable. Document US 8,100,116 B2 describes a direct-injection diesel engine in which, at loads below maximum load, the exhaust valve is opened in a controlled manner during part of the intake stroke to draw exhaust gas remaining in the exhaust manifold back into the cylinder, thereby ensuring a specific amount of exhaust gas in the cylinder. The document anticipates that this will reduce carbon monoxide emissions. Furthermore, document US 2015 / 0033736 A1 describes a two-stroke engine with exhaust gas recirculation in which fresh air from a turbocharger is mixed with recirculated exhaust gas, and exhaust backpressure is created at the exhaust valve by selectively controlling the exhaust flow.Furthermore, the document EP 1 380 742 A1 describes a diesel engine with direct injection and a particulate filter in the exhaust system, whereby fuel is injected after the expansion stroke to clean the particulate filter, in order to have unburned fuel in the exhaust system, which can be used to support particulate filter regeneration. Accordingly, it would be desirable to provide a way to regenerate a particulate filter of a two-stroke diesel engine so that a significant portion of the subsequently injected fuel leaves the engine cylinder and reaches the oxidation catalyst in order to simplify particulate filter regeneration. To mitigate the described problem, particle filter regeneration methods according to claims 1 and 9 are proposed according to the invention. Preferred embodiments of the invention are the subject of the dependent claims. The inventors have thus developed a particulate filter regeneration process comprising: receiving sensor data to a controller; and adjusting a post-injection fuel pulse width, provided to a second fuel injection device of a cylinder, via the controller in response to a quantity of internal residue in the cylinder, as estimated from the sensor data. By adjusting the post-injection fuel pulse width in response to a certain amount of internal residue, it may be possible to regenerate a particulate filter by injecting fuel into a cylinder of a two-stroke diesel engine. Furthermore, the present method can reduce the amount of fuel injected during a cylinder cycle that is retained in that cylinder until the next cylinder cycle, or it can help to ensure that this occurs with less fuel. By reducing the amount of fuel retained from one cylinder cycle to the next, the possibility of fuel auto-ignition can be reduced. Additionally, the generation of engine torque can be made more consistent. The present description can offer several advantages. In particular, the approach can improve particulate filter regeneration for a two-stroke diesel engine. Furthermore, the approach can improve engine torque control by improving the control of the amount of fuel burned in a cylinder cycle. Additionally, the approach can provide improved control over how much post-injected fuel is released into the exhaust system for particulate filter regeneration. The aforementioned advantages, as well as other advantages and features of the present description, are readily apparent from the following detailed description, whether considered on its own or in conjunction with the accompanying drawings. It is understood that the foregoing summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the full description. It is not intended to identify important or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the full description. Furthermore, the claimed subject matter is not limited to implementations that overcome the disadvantages mentioned above or in any part of this disclosure. Brief description of the characters Fig. 1 shows a schematic diagram of an engine; Fig. 2 shows an exemplary particulate filter regeneration sequence; Fig. 3 shows the timing of post-fuel injection in relation to the piston position; and Fig. 4 is an exemplary method for regenerating a particulate filter. Detailed description This description concerns the regeneration of a particulate filter in a two-stroke diesel engine. Fig. 1 shows an example of a turbocharged two-stroke diesel engine. The diesel engine in Fig. 1 is an opposed-piston engine; however, the methods described here can also be applied to two-stroke engines that include a single piston in each cylinder. Fig. 2 shows an exemplary particulate filter regeneration sequence. The fuel injection timing for a two-stroke diesel engine is shown in Fig. 3. A method for regenerating a particulate filter is shown in Fig. 4. With reference to Fig. 1, an opposed-piston internal combustion engine 10, comprising a plurality of cylinders, one of which is shown in Fig. 1, is controlled by the electronic engine control unit 12. The control unit 12 receives signals from the various sensors shown in Fig. 1 and uses the various actuators shown in Fig. 1 to adjust the engine operation based on the received signals and instructions stored in a memory of the control unit. The engine 10 comprises the cylinder 30 and the cylinder walls 32 with the intake piston 36a and the exhaust piston 36b positioned within it and each connected to the crankshafts 40a and 40b, respectively. The crankshafts 40a and 40b can be coupled to each other via belts, chains, or gears. The crankshafts 40a and 40b can be rotated by the electric machine 77 (e.g., a starter motor) to crank the engine 10. The cylinder 30 is shown communicating with the intake manifold 44 and the exhaust manifold 48 via the intake ports 44a and 44b and the exhaust ports 48a and 48b. The first fuel injection device 69 and the second fuel injection device 68 are shown positioned in the cylinder walls 32 and capable of injecting fuel directly into the cylinder 30, a process known to those skilled in the art as direct injection. Fuel is supplied to the first fuel injection device 69 and the second fuel injection device 68 via a fuel system comprising a fuel tank 95, a fuel pump 91, a fuel pump control valve 93, and a fuel distributor (not shown). The fuel pressure supplied by the fuel system can be adjusted by varying a control valve flow to a fuel pump (not shown). Furthermore, a measuring valve for closed-loop fuel control may be located in or near the fuel distributor.A pump metering valve can also regulate the fuel flow to the fuel pump, thereby reducing the amount of fuel pumped to a high-pressure fuel pump. The first fuel injector is positioned such that its longitudinal axis 69d and the fuel spray cone 69c are at an obtuse angle 69b to the portion of the cylinder wall 32 located between the fuel injector 69 and the exhaust piston 36b. Thus, the fuel spray cone 69c points towards the intake piston 36a and away from the exhaust piston 36b. The second fuel injector 68 can be positioned so that its nozzle 68a points directly towards the exhaust port 48a. The second fuel injector 68 can supply fuel in a fuel spray cone 68c that directly impacts the exhaust port 48a when fuel is injected via the second fuel injector 68.Alternatively, the second fuel injection device can be positioned such that its longitudinal axis 69b and the fuel spray cone 68c are at an acute angle 68d to the portion of the cylinder wall 32 located between the fuel injection device 68 and the exhaust piston 36b. Accordingly, the fuel spray cone 68c points towards the exhaust piston 36b and away from the intake piston 36a. In this way, the nozzle 69a can direct fuel mist towards the intake piston 36a, and the nozzle 68a can direct fuel mist towards the exhaust piston 36b. The intake manifold 44 is shown connected to an optional electronic throttle 62, which sets the position of the throttle valve 64 to control the airflow from an intake charge chamber 46. The compressor 162 is mechanically driven and draws air downstream of the turbocharger compressor 135. The turbocharger compressor 135 draws air from the air inlet 42. The compressor 162 supplies air to the charge chamber 46. Exhaust gases cause a variable geometry turbine 137 to rotate, which is coupled to the turbocharger compressor 135 via the shaft 136. The compressor 162 is mechanically driven via the crankshaft 40b through the shaft 161 and the gearbox 163, which can be coupled to the crankshaft 40b via the mechanism 164 (e.g. gears, a chain or a belt).The compressor gearbox 163 incorporates a variety of gear ratios to change the speed of the compressor 162 relative to the speed of the crankshaft 40b. The speed of the compressor can be adjusted by selecting and engaging gear(s) 163a of the gearbox 163. For example, the compressor 162 can be rotated at a given engine crankshaft speed to a first speed and a second speed by switching between a first and a second gear ratio in the gearbox 163. The compressor bypass valve 158 can be selectively opened to reduce the air pressure in the charge chamber 46 and recirculate air and exhaust gas recirculation (EGR) upstream of the compressor 162. In some examples, an intercooler 156 may be provided downstream of the compressor 162 to cool the air charge entering cylinder 30. The intercooler bypass valve 157 can be selectively opened to bypass the intercooler 156. The position of the swivel motor 137a can be adjusted via the control 12 to increase or decrease the rotational speed of the turbine 137. In alternative examples, a wastegate 137b may replace or be used in addition to the swivel motor 137a. The swivel motor 137a adjusts the position of variable geometry turbine guide vanes.Exhaust gases can be routed through the turbine 137, supplying a small amount of energy to rotate the turbine 137 when the guide vanes are in an open position. Exhaust gases can be routed through the turbine 137, transferring increased power to the turbine 137 when the guide vanes are in a closed position. Alternatively, the wastegate 137b or a bypass valve allows the exhaust gases to flow around the turbine 137, thus reducing the amount of energy supplied to the turbine. In an alternative example, the compressor 162 can be positioned upstream of the turbocharger 135. Furthermore, an intercooler (not shown) can be positioned downstream of where the EGR channel 82 connects to the inlet 43 between the compressor 162 and the turbocharger 135. The intercooler eliminates the need for an EGR cooler. Exhaust gases can be recirculated to cylinder 30 via the EGR system 81. The EGR system includes an optional EGR cooler 85, an optional EGR valve 80, an optional EGR duct 82, an optional EGR cooler bypass 84, and an optional cooled EGR duct 83. Exhaust gases can flow from the exhaust manifold 48 to the engine air intake 43 between the supercharger compressor 162 and the turbocharger compressor 135. EGR can flow to the engine air intake when the pressure in the exhaust manifold 48 is greater than the pressure between the turbocharger compressor 135 and the supercharger compressor 162. The EGR can flow through the EGR cooler 85 to reduce engine exhaust gas temperatures. The EGR can bypass the EGR cooler 85 when the engine exhaust temperatures are low. Fuel can be injected into cylinder 30 when pistons 36a and 36b approach each other, after the intake piston 36a covers the intake ports 44a and 44b and the exhaust piston 36b covers the exhaust ports 48a and 48b. The fuel can then be combusted with air in cylinder 30 when piston 36 is near top dead center of the compression stroke. The fuel and air are ignited via compression ignition. In some examples, a wideband lambda sensor (universal exhaust gas oxygen sensor - UEGO sensor) 126 may be coupled to the exhaust manifold 48 upstream of an emission device 70. In other examples, the UEGO sensor may be located downstream of one or more exhaust aftertreatment devices. Furthermore, in some examples the UEGO probe can be replaced by a NOx sensor that has both NOx and oxygen detection elements. Engine 10 does not include glow plugs or spark plugs, as it is a compression-ignition engine and does not include a cylinder head. Furthermore, engine 10 does not include poppet valves to regulate the flow of air and exhaust gases into and out of cylinder 30. The exhaust system 131 transports exhaust gas away from the engine 10 and processes it. The exhaust valve 140 is shown positioned in the exhaust channel 49 downstream of the turbine 137a and upstream of the emission device 70. Alternatively, the exhaust valve 140 can be positioned downstream of the emission device 70. The exhaust valve 140 can be opened and closed to regulate the pressure in the exhaust manifold 48. Closing the exhaust valve 140 limits the flow through it, thereby increasing the pressure in the exhaust manifold 48. Opening the exhaust valve 140 increases the flow and decreases the pressure in the exhaust manifold 48. The emission control device 70 can, in one example, include an oxidation catalyst 72 and a particulate filter 73. In another example, several emission control devices, each with multiple honeycomb bodies, can be used. The emission control device 70 can include an oxidation catalyst in one example. In other examples, the emission control device can include a lean NOx trap or selective catalytic reduction (SCR) and / or a diesel particulate filter (DPF). An upstream temperature sensor 79 and a downstream temperature sensor 81 provide exhaust gas temperature measurements for determining the change in exhaust gas temperature in the emission control device 70. The differential pressure sensor 71 provides a differential pressure change in the emission control device 70, which can form the basis for assessing whether the emission control device 70 needs to regenerate. The controller 12 is shown in Fig. 1 as a conventional microcomputer comprising: a microprocessor unit 102, input / output channels 104, a read-only memory (e.g., non-volatile memory) 106, a random access memory 108, a keep-alive memory 110, and a conventional data bus.According to the diagram, in addition to the signals discussed previously, the control unit 12 receives various signals from the sensors connected to the engine 10, including: an engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 to detect the accelerator pedal position set by a human foot 132; an engine manifold pressure (MAP) measurement from a pressure sensor 121 coupled to the intake manifold 44; a boost pressure from a pressure sensor 122; an exhaust oxygen concentration from a lambda sensor 126; an engine position sensor from a Hall effect sensor 118 detecting the position of the crankshaft 40b; and a measurement of the mass of air flowing into the engine from a sensor 120 (e.g.,a hot-wire air mass meter); and a measurement of the throttle position from a sensor 58. The barometric pressure can also be acquired for processing by the controller 12 (sensor not shown). In a preferred aspect of the present description, the engine position sensor 118 generates a predetermined number of evenly spaced pulses at each revolution of the crankshaft, from which the engine speed (rpm) can be determined. During operation, each cylinder in engine 10 is typically subjected to a two-stroke cycle: The cycle includes a first stroke in which the intake piston 36a moves towards the exhaust piston 36b and the exhaust piston 36b moves towards the intake piston 36a. In the second stroke, the intake piston 36a moves away from the exhaust piston 36b and the exhaust piston 36b moves away from the intake piston 36a. The intake piston 36a controls the flow through the intake ports 44a and 44b. The exhaust piston 36b controls the flow through the exhaust ports 48a and 48b. In this example, the exhaust piston 36b precedes the intake piston 36a by reaching a top dead center position (e.g., a maximum distance of the exhaust piston 36b to the crankshaft 40b) a few crankshaft degrees earlier (e.g., depending on the configuration, the difference can be between 0 and 20 crankshaft degrees) before the intake piston 36a reaches its top dead center position (e.g.,the maximum distance of the intake piston 36a from the crankshaft 40a) is reached. Thus, the movement of the exhaust piston is offset from the movement of the intake piston by a few crankshaft degrees. During the first stroke, the intake piston 36a and the exhaust piston 36b generally move towards each other to compress air that has entered cylinder 30. The stroke begins for the intake piston 36a at bottom dead center (BDC) (the intake piston 36a is at its closest point to the crankshaft 40a) and ends for the intake piston 36a at top dead center (TDC) (the intake piston 36a is at its farthest point from the crankshaft 40a). As mentioned earlier, the exhaust piston 36b precedes the intake piston 36a by a few degrees, so it is already moving towards its TDC position when the intake piston is at BDC. Furthermore, the exhaust piston 36b reaches its TDC position shortly before the intake piston 36a reaches its TDC position. The drain piston 36b is located directly after its TDC position when the intake piston 36a reaches its TDC position.The cylinder volume is at its smallest when the intake piston 36a and the exhaust piston 36b are near their respective top dead center (TDC) positions. Air and fuel are compressed in cylinder 30 as the intake piston 36a and the exhaust piston 36b move towards their respective TDC positions. The intake ports 44a and 44b are open, and compressed air flows into cylinder 30, when the intake piston 36a and the exhaust piston 36b are near their respective bottom dead center (BDC) positions. The exhaust ports 48a and 48b are also open when the intake piston 36a and the exhaust piston 36b are near BDC. The compressor 162 and the turbocharger 135 supply compressed air to the intake manifold 44, which can flow into cylinder 30 when the intake ports 44a and 44b are open.As the intake piston 36a and the exhaust piston 36b move towards their respective top dead center (TDC) positions, the intake ports 44a and 44b are closed to prevent additional air from entering cylinder 36 and to prevent backflow from cylinder 36. After the intake ports 44a and 44b are closed, the intake piston 36a and the exhaust piston 36b continue to approach their respective TDC positions. Once the intake ports 44a and 44b are closed, the crankshafts 40a and 40b rotate through a predetermined angle, and then the exhaust ports 48a and 48b are closed. Thus, the exhaust ports 44a and 44b remain open throughout the entire intake stroke.Fuel is injected into cylinder 30 after the exhaust ports 44a and 44b close; the fuel-air mixture is then ignited when the intake piston 36a and the exhaust piston 36b are near their respective top dead center (TDC) positions. The fuel-air mixture is ignited by compression ignition, not by a spark plug or glow plug. The fuel can be injected into cylinder 30 via a variety of injection methods, including pre-injection, main injection, and post-injection. During the second stroke, the intake piston 36a and the exhaust piston 36b generally move away from each other after combustion has occurred in cylinder 30. The second stroke begins at top dead center (TDC) of the intake piston 36a and ends at bottom dead center (BDC) of the intake piston 36a. The intake piston 36a and the exhaust piston 36b approach their respective BDC positions, near which the volume of cylinder 30 is greatest. Expanding gases in cylinder 30 push the intake piston 36a and the exhaust piston 36b away from each other towards their respective BDC positions. The exhaust piston 36b passes the exhaust ports 48a and 48b as it moves towards its BDC. The exhaust ports 48a and 48b are exposed when the top of the drain piston 36d passes the exhaust ports 48a and 48b as the drain piston 36b moves towards the crankshaft 40b.Exhaust gases exit cylinder 30 after the exhaust piston 36b passes exhaust ports 48a and 48b as it moves towards bottom dead center. The intake piston 36a and exhaust piston 36b continue to move towards their respective bottom dead center positions, and after a predetermined total number of crankshaft degrees, the intake piston 36a exposes intake ports 44a and 44b. Intake ports 44a and 44b are exposed when the top of the intake piston 36c passes intake ports 44a and 44b as the intake piston 36a moves towards the crankshaft 40a. Fresh air enters cylinder 30 through intake ports 44a and 44b as they are exposed. The outlet ports 48a and 48b are open or exposed at all times when the intake ports 44a and 44b are open or exposed.The intake piston 36a and the exhaust piston 36b continue to move towards their respective bottom dead center (BDC) positions. After the intake piston reaches BDC, the cylinder cycle repeats. Thus, the engine cycle consists of two strokes, and one engine cycle corresponds to one engine revolution. Other engine cylinders operate similarly, but these other cylinders may burn air and fuel out of phase with the cylinder shown. For example, the top dead center of the compression stroke of one engine cylinder may be at zero crankshaft degrees, while the top dead center of another cylinder may be at one hundred and eighty crankshaft degrees. Accordingly, the system shown in Fig. 1 provides an engine system comprising: an opposed-piston diesel engine, including a cylinder with a first fuel injection device and a second fuel injection device; a compressor coupled to the opposed-piston diesel engine, the compressor having multiple drive ratios; a turbocharger coupled to the opposed-piston diesel engine; and a control system, including executable instructions stored in non-volatile memory, to provide a late post-injection fuel quantity during a cylinder cycle solely through the second fuel injection device, and to provide a main injection fuel quantity during the cylinder cycle solely through the first fuel injection device.The engine system further includes additional instructions to adjust the post-injection fuel quantity in response to the amount of internal residue in the cylinder. The engine system includes instructions to initiate post-injection in response to an increase in the amount of internal residue. The engine system includes instructions to initiate post-injection in response to an increase in the amount of internal residue. The engine system includes instructions to delay the initiation of post-injection in response to a decrease in the amount of internal residue. The engine system further includes additional instructions to adjust internal exhaust gas recirculation in response to engine speed and load. An exemplary particulate filter regeneration sequence according to method 400 is now shown with reference to Fig. 2. The particulate filter regeneration sequence from Fig. 2 can be intended for the engine and system shown in Fig. 1. The vertical lines at times t0-t3 represent relevant time points in the sequence. The processes are temporally aligned and occur simultaneously. In this exemplary particulate filter regeneration sequence, the post-injection fuel quantity is adjusted in response to internal residues in an engine cylinder. The internal residues correspond to combustion byproducts (e.g., the exhaust gases CO, HC, NOx) that can remain in a cylinder from one combustion event (e.g., compression ignition and combustion of air and fuel in a cylinder) to the next subsequent combustion event. The first graph from the top in Fig. 2 shows the regeneration request of a diesel particulate filter (DPF) over time. Trace 201 represents a regeneration state of the DPF. The vertical axis represents the regeneration state of the DPF, and a regeneration request is confirmed when trace 201 is at a higher level near the arrow of the vertical axis. A regeneration request is not confirmed when trace 201 is at a lower level near the horizontal axis. The horizontal axis represents time, and time increases from the left to the right side of the figure. The second graph from the top in Fig. 2 shows the post-injection fuel quantity injected into a cylinder as a function of time. Trace 202 represents the post-injection fuel quantity. The vertical axis represents the post-injection fuel quantity, which increases in the direction of the arrow on the vertical axis. The horizontal axis represents time, and time increases from the left side of the figure to the right side. The third graph from the top in Fig. 2 shows the amount of internal exhaust gas recirculation (IAGR) over time. Trace 204 represents the IGR amount. The vertical axis represents the IGR amount, which increases in the direction of the arrow on the vertical axis. The horizontal axis represents time, and time increases from the left side of the figure to the right side. The fourth graph from the top in Fig. 2 shows the motor speed versus time. Trace 205 represents the motor speed. The vertical axis represents the motor speed, and the motor speed increases in the direction of the arrow on the vertical axis. The horizontal axis represents time, and time increases from the left side of the figure to the right side. The fifth graph from the top in Fig. 2 is a graph of engine load versus time. Trace 207 represents the engine load. The vertical axis represents the engine load, and the engine load increases along the vertical axis. The horizontal axis represents time, and time increases from the left side of the figure to the right side. The sixth graph from the top in Fig. 2 shows the amount of soot that has accumulated in a particulate filter over time. The vertical axis represents the amount of soot that has accumulated in the particulate filter. Line 206 represents the amount of particulate matter that has accumulated in the particulate filter. The horizontal axis represents time, and the time increases from the left side of the figure to the right side. At time t0, the engine is running and burning air and fuel at a medium speed and load. DPF regeneration is not requested, however, the soot level in the DPF is at a higher stage. The IGR amount corresponds to a medium stage, and the post-injection fuel quantity is zero. At time t1, the DPF regeneration request is confirmed in response to the amount of accumulated soot and vehicle operating conditions. The post-injection fuel quantity begins to increase in response to the confirmation of the particulate filter regeneration request. The amount of IGR decreases in response to an increase in engine load. The engine speed begins to increase in response to an increase in engine load. The increase in engine load may be due to higher driver demand torque (not shown). The amount of soot accumulated in the particulate filter begins to decrease. Between time t1 and time t2, the engine speed continues to increase, and the engine load also increases. The amount of IGR (Intake Air Recirculation) is reduced in response to the engine speed and load. The amount of post-injection fuel is increased in response to the reduced IGR amount. The post-injection fuel quantity can be increased in response to the reduced IGR amount because the reduced IGR amount indicates that less post-injection fuel can be retained in the cylinder until the next cylinder cycle. Therefore, an increased amount of fuel can be subsequently injected into the cylinder and expelled into the engine's exhaust system, preventing it from remaining in the cylinder during the next cycle. This subsequently injected fuel can then increase the exhaust gas temperature, thus regenerating the particulate filter.The amount of soot in the particulate filter is reduced when the exhaust gas temperature of the engine is increased (not shown). At time t2, the engine load is reduced in response to a decrease in driver demand torque (not shown). The engine speed begins to decrease in response to the reduced engine load. The amount of IGR is increased in response to the reduced engine load. The amount of post-injection fuel is reduced in response to the increased IGR, so less fuel can be carried in the cylinder until the next cylinder cycle. The amount of soot continues to decrease, and the particulate filter regeneration request remains confirmed. Between time t2 and time t3, the engine load increases after having been reduced, and the engine speed begins to rise. The amount of IGR is increased in response to the increase in engine load and engine speed. The amount of post-injection fuel is increased in response to the reduction in IGR, and the soot collected in the particulate filter continues to decrease. The particulate filter regeneration request remains valid. At time t3, the soot collected in the particulate filter is less than a threshold value, so the particulate filter regeneration request is withdrawn. The post-injection fuel quantity is set to zero, and the IGR amount is based on engine speed and load. Engine speed and load respond to the driver's torque demand (not shown). In this way, the post-injection fuel quantity can be adjusted in response to the IGR amount. Furthermore, the start and end of the post-injection fuel injection timing can also be adjusted in response to the IGR amount. By adjusting the post-injection fuel quantity in response to the IGR amount, the amount of fuel supplied to the oxidation catalyst can be controlled, while simultaneously controlling the amount of post-injected fuel that remains in the cylinder for the next cylinder cycle. Therefore, it may be possible to simplify particulate filter regeneration by increasing the temperature of gases exiting the oxidation catalyst, while reducing the possibility of post-injection fuel igniting in a cylinder during a subsequent cylinder cycle. An exemplary fuel injection sequence according to method 400 is now shown with reference to Fig. 3. This exemplary fuel injection sequence occurs during particulate filter regeneration. The fuel injection sequence from Fig. 3 can be considered for the engine and system shown in Fig. 1. The vertical lines at times t10-t15 represent relevant points in the sequence. The processes are temporally aligned and occur simultaneously. In this example, post-injection of fuel is carried out via a second fuel injection device, which has a nozzle pointing directly at an outlet port. The first curve from the top in Fig. 3 shows a curve of fuel injection pulses delivered to a cylinder via a first fuel injection device (e.g., the injection device 69 from Fig. 1). The fuel pulses are delivered during the regeneration of a particulate filter. Trace 302 represents fuel injection pulses from a first fuel injection device. The amount of fuel injected into the cylinder increases as the pulse widths increase, and the amount of fuel injected into the cylinder decreases as the pulse widths decrease. The horizontal axis represents time, and time increases from the left side of the figure to the right side. The second trace from the top in Fig. 3 is a trace of fuel injection pulses delivered to a cylinder via a second fuel injection device (e.g., the injection device 68 from Fig. 1). The fuel pulses are delivered during the regeneration of a particulate filter. Trace 304 represents fuel injection pulses from a second fuel injection device. The amount of fuel injected into the cylinder increases as the pulse widths increase, and the amount of fuel injected into the cylinder decreases as the pulse widths decrease. The horizontal axis represents time, and time increases from the left side of the figure to the right. The nozzle of the second fuel injection device points directly at an exhaust port, so a fuel spray cone from the second fuel injection device impinges directly on the exhaust port. The third curve from the top in Fig. 3 shows the opening and closing of a cylinder's intake port over time. Trace 303 represents the state of the intake port. The vertical axis represents the state of the cylinder's intake port, and the port is open when trace 303 is at a higher level near the arrow on the vertical axis. The intake port is closed when trace 303 is at a lower level near the horizontal axis. The horizontal axis represents time, and time increases from the left side of the figure to the right. The fourth curve from the top in Fig. 3 shows the state of a cylinder's exhaust port over time. Trace 304 represents the exhaust port's state. The vertical axis represents the exhaust port's state, and the exhaust port is open when trace 304 is at a higher level, close to the arrow on the vertical axis. The exhaust port is closed when trace 304 is near the horizontal axis. The horizontal axis represents time, and time increases from the left to the right side of the figure. The fifth curve from the top in Fig. 3 is a curve of the piston position against time. The curve 305 represents the piston position of an intake piston 36a. The piston is at top dead center (TDC) when the curve 305 is on the step of the vertical axis labeled TDC. The piston is at bottom dead center (BDC) when the curve 305 is on the step of the vertical axis labeled BDC. The horizontal axis represents time, and time increases from the left side of the figure to the right. At time t10, the piston is at bottom dead center (BDC) and the intake and exhaust ports are open. Fuel is not injected through the first and second fuel injectors. The engine rotates, and at time t11, the exhaust port is closed while the intake port remains open. Fuel is still not injected through the first and second fuel injectors. The engine continues to rotate, and then at time t12, the intake port closes. Fuel is still not injected at time t12, and the engine continues to rotate as time increases. The exhaust port remains closed. As the piston approaches top dead center (TDC), fuel pre-injections are provided at time t13.In this example, fuel pre-injections are provided via the first and second fuel injectors; however, in some examples, the fuel pre-injections may only be provided by the first fuel injector. Two fuel pre-injections are provided. Then, at time t14, a main fuel injection pulse is provided via the first fuel injector. However, in other examples, a main fuel injection pulse may also be provided via the second injector. The engine compresses the injected fuel, and the air-fuel mixture is ignited. At time t15, post-injection is provided only via the second fuel injection device, allowing a larger percentage of post-injected fuel to be expelled from the cylinder and reach the oxidation catalyst, thus facilitating particulate filter regeneration. In this example, a single post-injection pulse is provided, but additional pulses can be supplied. The post-injected fuel is injected late, when the exhaust port opens at time t15, allowing a larger percentage of injected fuel to flow out of the cylinder. However, post-injection can be provided after the main injection and before the exhaust port opens. Furthermore, if the post-injection timing is early (e.g.,Towards the end of the ignition cycle, the first fuel injection device can also provide post-injection of fuel. The post-injection is completed before the intake port opens at time t16. The cylinder cycle then repeats, starting shortly after time t16. In this way, fuel can be injected post-injection during a cylinder cycle to simplify particulate filter regeneration. The post-injection fuel pulse widths are timed to increase the flow of post-injected fuel to the oxidation catalyst, thus reducing the amount of fuel remaining in the cylinder for the next cylinder cycle. With reference to Fig. 4, a method for regenerating a particulate filter positioned downstream of a two-stroke diesel engine in an exhaust system is shown. The method from Fig. 4 can be stored as executable instructions in non-volatile memory within systems such as those shown in Fig. 1. The method from Fig. 4 can be integrated into and interact with the systems from Fig. 1. Furthermore, at least parts of the method from Fig. 4 can be included as executable instructions stored in non-volatile memory, while other parts of the method can be executed via a controller that translates the operating states of devices and actuators into the physical domain. The controller can utilize motor actuators of the engine system to adjust engine operation according to the methods described below. In procedure 402, the method determines 400 vehicle operating conditions. Vehicle operating conditions may include, among other things, the amount of soot captured by a particulate filter, the amount of internal residue, the particulate filter temperature, the engine speed, the engine load, and the driver-demand torque. The vehicle operating conditions may be determined from or derived from sensor data received via the controller 12 shown in Fig. 1. For example, the amount of internal residue may be estimated in response to the engine speed, the engine load, the intake manifold pressure, and the position of an exhaust valve. The engine speed, the engine load, the intake manifold pressure, and the exhaust valve position may reference one or more tables and functions that include empirically determined values ​​of an amount of internal residue. The tables or functions output the estimate of the amount of residue in the cylinder.The driver-demand torque can be determined from the accelerator pedal position and the vehicle speed with respect to a table or function containing empirically determined values ​​for the driver-demand torque. The function or table outputs the driver-demand torque. Procedure 400 transitions to 404. In procedure 404, procedure 400 operates the engine according to the operating conditions specified in 402. The timing of fuel injection for pre- and main injections is based on the vehicle operating conditions specified in 402. Fuel pre-injections are short-duration fuel injections that may be less than 4 mg. Fuel pre-injections begin and end before the top dead center (TDC) compression stroke in the cylinder cycle in which they are injected. Fuel pre-injections can reduce combustion noise in the engine, control peak cylinder pressures, and adjust heat dissipation in the cylinder. Fuel main injections are injections of the largest amount of fuel injected during a cylinder cycle. Fuel main injections can range from 3 mg to 100 mg per cylinder cycle. Fuel pre-injections precede fuel main injections.The first fuel injection device can supply pre-injections, main injections, and early post-injections. The second fuel injection device can provide pre-injections, main injections, and early and late post-injections. Boost pressure, throttle position, exhaust throttle position, pre- and main injection timing, and external EGR settings can be based on engine speed and load. Procedure 400 transitions to 406. At 406, procedure 400 assesses whether particulate filter (PF) regeneration is desired. Procedure 400 can assess that PF regeneration is desired in response to the amount of soot collected in the PF exceeding a threshold amount and the engine load being greater than a threshold load. If procedure 400 decides that PF regeneration is desired, the answer is yes, and procedure 400 proceeds to 408. Otherwise, the answer is no, and procedure 400 proceeds to 440. At 440, procedure 400 terminates the particulate filter regeneration by stopping the injection of post-injection fuel. Furthermore, procedure 400 can adjust the engine boost pressure and exhaust throttle positions to complete the particulate filter regeneration. Procedure 400 then proceeds to its end. At stage 408, procedure 400 begins, increasing the particulate filter (PF) temperature. Procedure 400 can increase boost pressure and at least partially close the exhaust throttle to raise exhaust temperatures and initiate PF regeneration. Procedure 400 then transitions to stage 410. In procedure 400, method 410 estimates the internal residues in an engine cylinder. Internal residues correspond to residues (HC, NOx, and CO) that remain in a cylinder from a first combustion event (e.g., combustion of air and fuel in a cylinder) to a subsequent second combustion event. Internal residues do not leave the cylinder from the first combustion event to the next or second combustion event, except that internal residues may include residues that exit the exhaust port and are drawn back into the cylinder from the exhaust port before the second combustion event. Internal residues do not include residues that exit the exhaust port and re-enter the cylinder via the intake port. In one example, Procedure 400 estimates the amount of internal exhaust gas recirculation (IAGR) in the cylinder. In another example, the amount of internal residue can be estimated by referencing one or more tables or functions on the engine speed, engine load, boost pressure, and exhaust throttle position. The tables or functions contain empirically determined estimates of the amount of internal residue. The tables or functions output the amount of internal residue. Procedure 400 then proceeds to 412. In procedure 400, method 412 determines a post-injection fuel quantity, the start of the post-injection pulse width, and the end of the post-injection pulse width. Early post-injections can occur ten crankshaft degrees after top dead center (TDC) compression stroke and after a main fuel injection. Early post-injections can range from 1 mg to 10 mg. Late post-injections are fuel injections that occur after the completion of combustion of the main fuel injection pulse and before an exhaust port of the cylinder receiving the fuel closes during the cylinder stroke. Early and late post-injections can be useful for regenerating emission control devices in the engine's exhaust system (e.g., a power distribution filter). In one example, procedure 400 refers to one or more functions and / or tables that include a post-injection fuel quantity, the start of the post-injection fuel pulse width, and the end of the post-injection fuel pulse width. The values ​​in the table are determined empirically and stored in the control unit's memory. The tables and / or functions can be referenced via a desired PF temperature, engine speed, engine load, and a desired IGR amount. The tables and / or functions increase the post-injection fuel quantity when the IGR amount is decreased. The post-injection fuel quantity can be increased when the IGR amount is decreased because a larger proportion of post-injected fuel can exit the cylinder when the IGR amount is small.The tables and / or functions also show that the post-injection fuel quantity is reduced when the IAGR amount is increased, so less fuel is trapped in the cylinder from one cylinder's first cycle to the next. In one example, the end of the post-injection pulse width is within five crankshaft degrees of the exhaust port opening, so blowing off the cylinder helps to clear fuel injected into the cylinder.Additionally, the start of post-injection can be brought forward in response to an increase in the IAGR amount, allowing the end of post-injection to also be brought forward. This enables all the post-injected fuel to be injected during a cylinder cycle before the exhaust port opens, allowing more post-injected fuel to exit the exhaust port before the next cylinder cycle. Conversely, the start of post-injection can be delayed in response to a decreasing IAGR amount, allowing the end of post-injection to also be delayed. This enables larger post-injection fuel pulses to end before the exhaust port opens. The larger fuel pulse widths can increase the temperature in the oxidation catalyst, thereby increasing the exhaust gas temperatures reaching the particulate filter.In one example, the post-injection fuel pulses start at a time before the cylinder's exhaust port opens, or when the cylinder's exhaust port opens. The post-injection fuel pulses end before the intake port opens during the cylinder stroke in which the fuel was injected, as shown in Fig. 3. Method 400 transitions to 414. In 414, method 400 provides the post-injection fuel pulses for one or more engine cylinders via the first and second fuel injectors, or via the second fuel injector alone. The post-injections can be provided by either the first or second fuel injector if the post-injections are early. The second fuel injector can be the only fuel injector providing late post-injections. Method 400 transitions to 416 after post-injections have been provided at the times determined in 412. At 416, procedure 400 assesses whether the particulate filter regeneration is complete. In one example, differential pressure sensor 71 outputs data indicative of whether the soot absorbed by the particulate filter is less than a threshold amount. If procedure 400 determines that particulate filter regeneration is complete, the answer is yes, and procedure 400 proceeds to the end. Otherwise, the answer is no, and procedure 400 returns to 410. Accordingly, the method shown in Fig. 4 provides a particulate filter regeneration process comprising: receiving sensor data to a controller; and setting a post-injection fuel pulse width, provided to a second fuel injection device of a cylinder, via the controller in response to a quantity of internal residue in the cylinder, as estimated from the sensor data. The particulate filter regeneration process includes the internal residue being estimated from the engine speed and the engine boost pressure, and the post-injection fuel pulse width being provided during the cylinder cycle before the exhaust port opens.The method includes, wherein the second fuel injection device is positioned at an angle to a cylinder wall such that fuel mist is directed from the second fuel injection device to a drain piston, and further comprises: adjusting a post-injection fuel pulse width provided to a first fuel injection device of the cylinder via the control unit in response to the amount of residue in the cylinder, as estimated from sensor data. The particulate filter regeneration method includes, wherein the internal residue is estimated from the engine speed and the position of a valve in an exhaust system. The particulate filter regeneration method includes, wherein adjusting the post-injection fuel pulse width includes increasing the post-injection fuel pulse in response to a decrease in the amount of internal residue in the engine cylinder.The particulate filter regeneration process includes adjusting the post-injection fuel pulse width, which involves reducing the post-injection fuel pulse in response to an increase in the amount of internal residue in the cylinder. Additionally, the particulate filter regeneration process includes the post-injection fuel pulse width being injected directly into a cylinder during a cylinder stroke, in which a piston exposes an exhaust port and an intake port. The particulate filter regeneration process includes the exhaust port being open for the entire duration that the intake port is open during the stroke. The particulate filter regeneration process also includes the provision of a post-injection fuel pulse width for the cylinder's second fuel injector during a cylinder cycle, and the provision of a main injection fuel pulse width for the cylinder's first fuel injector during the cylinder cycle. The method shown in Fig. 4 also provides a particulate filter regeneration process comprising: receiving sensor data to a controller; setting a post-injection fuel pulse width, provided to a second fuel injector of a cylinder, via the controller in response to a quantity of internal residue in the cylinder, as estimated from the sensor data; and injecting a post-injection fuel quantity into the cylinder via the second fuel injector, wherein the second fuel injector includes a spray cone that directly impinges an exhaust port of the cylinder. The particulate filter regeneration process includes, wherein the injection of the post-injection fuel quantity includes the injection of fuel via the second fuel injector between the time at which the exhaust port opens and the time at which an intake port of the cylinder opens.The particulate filter regeneration process includes a piston opening the intake and exhaust ports. The process further includes injecting a main quantity of fuel into the cylinder via a first fuel injection device. The process also includes adjusting the amount of internal residue in response to engine speed and load. Finally, the process includes adjusting the amount of internal residue by adjusting the cylinder boost pressure. It should be noted that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-volatile memory and can be executed by the control system, which includes the control unit in combination with the various sensors, actuators, and other engine hardware. Furthermore, parts of the methods can be physical actions performed in the real world to change the state of a device. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like.Accordingly, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted. Likewise, the processing order is not strictly necessary to achieve the features and benefits of the examples described here, but is provided to facilitate illustration and description. One or more of the illustrated actions, operations, and / or functions can be performed repeatedly, depending on the specific strategy employed.Furthermore, the described actions, operations, and / or functions can graphically represent code that is to be programmed into the non-volatile memory of the computer-readable storage medium in the engine control system, whereby the described actions are carried out by executing the instructions in a system that includes the various engine hardware components in combination with the electronic control unit. One or more of the procedure steps described here can be omitted if desired. It is understood that the configurations and routines disclosed herein are exemplary and that these specific examples are not to be interpreted restrictively, as numerous variations are possible. For example, the foregoing technique can be applied to V-6, I-4, I-6, V-12, 4-cylinder boxer, and other engine types. The subject matter of this disclosure includes all new and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or properties disclosed herein.

Claims

Particulate filter regeneration process, comprising: Receiving sensor data to a controller (12); and adjusting a post-injection fuel pulse width provided to a second fuel injection device of a cylinder (30) via the controller (12) in response to an amount of internal residue in the cylinder (30) as estimated from the sensor data. Particle filter regeneration method according to claim 1, wherein the inner residue is estimated from the engine speed (205) and the engine boost pressure, wherein the second fuel injection device is located at an angle with respect to a wall of the cylinder (30) such that fuel mist is directed from the second fuel injection device to a drain piston (36b). Particulate filter regeneration method according to claim 1, wherein the inner residual is estimated from the engine speed (205) and the position of a valve (140) in an exhaust system (131), and wherein the post-injection fuel pulse width is provided during the cylinder cycle before the opening of the exhaust port (48a, 48b). Particulate filter regeneration method according to claim 1, wherein adjusting the post-injection fuel pulse width includes increasing the post-injection fuel pulse in response to a reduction in the amount of internal residue in the engine cylinder, and further comprising: adjusting a post-injection fuel pulse width provided to a first fuel injection device of the cylinder (30) via the control (12) in response to the amount of internal residue in the cylinder (30), as estimated from the sensor data. Particle filter regeneration method according to claim 1, wherein adjusting the post-injection fuel pulse width includes reducing the post-injection fuel pulse in response to an increase in the amount of internal residue in the cylinder (30). Particulate filter regeneration method according to claim 1, wherein the post-injection fuel pulse width is injected directly into a cylinder (30) during a stroke of the cylinder (30) in which a piston (36) exposes an exhaust port (48a, 48b) and an intake port (44a, 44b). Particle filter regeneration method according to claim 6, wherein the post-injection fuel pulse width is provided during the cylinder cycle before the opening of the intake port (44a, 44b). Particulate filter regeneration method according to claim 1, wherein the post-injection fuel pulse width is provided for the second fuel injection device of the cylinder (30) during a cylinder cycle and wherein a main injection fuel pulse width is provided for a first fuel injection device of the cylinder (30) during the cylinder cycle. Particulate filter regeneration method comprising: receiving sensor data to a controller (12); setting a post-injection fuel pulse width provided to a second fuel injection device of a cylinder (30) via the controller (12) in response to a quantity of internal residue in the cylinder (30) as estimated from the sensor data; and injecting a post-injection fuel quantity to a cylinder (30) via the second fuel injection device, the second fuel injection device comprising a spray cone acting directly on an outlet port (48a, 48b) of the cylinder (30). Particulate filter regeneration method according to claim 9, wherein the injection of a post-injection fuel quantity comprises injecting fuel via the second fuel injection device between the time of opening of the exhaust port (48a, 48b) and the opening of the inlet port of the cylinder (30). Particle filter regeneration method according to claim 10, wherein a piston (36) opens the inlet port and the outlet port (48a, 48b). Particle filter regeneration method according to claim 9, further comprising injecting a main injection fuel quantity to a cylinder (30) via a first fuel injection device. Particle filter regeneration method according to claim 9, further comprising adjusting the amount of internal residue in response to engine speed (205) and load. Particle filter regeneration method according to claim 13, wherein the amount of the internal residue is adjusted by adjusting the boost pressure of the cylinder (30).

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