Power machine method and power machine system for draining condensate from an intercooler

Abstract

Power engine process, which includes the following: in response to a condensate level in an intercooler (80, 166), adjusting the timing of the fuel injection while the engine airflow is increased to a level greater than requested by a vehicle operator (132), wherein adjusting the timing of the fuel injection includes switching from a first injection timing control providing a homogeneous cylinder-air-fuel charge ignited by a spark to a second injection timing control providing a stratified cylinder-air-fuel charge ignited by a spark.

Description

[0001] The present application relates to methods and systems for emptying condensate from a charge air cooler without impairing combustion stability.

[0002] Turbocharged and supercharged engines can be configured to compress the ambient air entering the engine to increase power. Compressing the air can cause an increase in air temperature, and consequently, an intercooler can be used to cool the heated air, thereby increasing its density and further increasing the engine's potential power. Ambient air from outside the vehicle passes over the CAC (Cooling Air Conditioner) to cool the intake air passing through its interior. When the ambient air temperature decreases, or during humid or rainy weather conditions, condensation can form in the CAC if the intake air is cooled below the dew point of water. The condensate can accumulate at the bottom of the CAC or in the internal channels and cooling turbulence generators. When torque is increased, such as...During acceleration, the increased air mass flow can draw the condensate out of the CAC, pull it into the engine, and increase the likelihood of engine misfire.

[0003] Exemplary approaches to address combustion problems (e.g., misfires) resulting from condensate intake include preventing condensate buildup. However, the inventors have recognized the potential problems with such methods. While some specific methods can reduce or slow condensate formation in the CAC, condensate can still accumulate over time. If this buildup cannot be stopped, condensate intake during acceleration can cause engine misfires. Furthermore, based on both the engine speed-load condition and the engine configuration (e.g., whether the engine is a V-engine with different rows or an inline engine), some cylinders may receive more condensate than others, making them more susceptible to combustion problems.Other exemplary approaches to addressing combustion problems include collecting and / or draining the condensate from the CAC. While this can reduce condensate levels in the CAC, the condensate is moved to an alternative location or container that may be exposed to other condensate problems, such as freezing and corrosion. Furthermore, the container can add component cost and complexity. Still other approaches opportunistically drain condensate from the CAC when engine airflow increases, such as during a driver tip-in event. However, a tip-in may not occur at the time condensate draining is requested. In the meantime, condensate may continue to be drawn into the engine, impairing combustion. DE 10 2013 111 112 A1 describes a charge air cooler condensate purge cycle.DE 10 2013 111 118 A1 discloses an engine control system and method. DE 10 2014 203 425 A1 discloses a reduction of engine misfires due to charge air cooler condensate using cylinder-internal enrichment and positive valve overlap.

[0004] An improvement in the prior art is achieved by a power engine method according to independent claim 1 and independent claim 10, and by a power engine system according to independent claim 17. Preferred embodiments thereof are specified in the further claims. In one example, the problems described above can be addressed, at least partially, by a method for draining the condensate from the CAC during vehicle operation. The method may include: adjusting the timing of the fuel injection in response to a condensate level in an intercooler while the engine airflow is increased to a level higher than that requested by a vehicle operator.In this way, one or more engine cylinders can be temporarily operated in a lean stratified mode to drain the condensate, while the operation of other engine cylinders is stopped to maintain a stoichiometric air-fuel ratio of the exhaust gas.

[0005] In one example, an engine system may include an intercooler coupled downstream of a compressor and upstream of an intake throttle valve. During engine operation, condensate may accumulate in the intercooler. In response to condensate levels exceeding a threshold, the draining conditions may be considered met, and a drain cycle may be initiated to remove the condensate. Specifically, the timing of the fuel injection of one or more engine cylinders may be changed from a timing system that provides a homogeneous cylinder-air-fuel charge ignited by a single spark to another injection timing system that provides at least a somewhat stratified cylinder-air-fuel charge ignited by a single spark.By operating at least some cylinders in a lean stratified mode, an engine airflow level can be raised to or above a blow-off level at which condensate is blown into the engine.

[0006] For example, cylinders less sensitive to water absorption (i.e., cylinders less prone to absorption-induced misfires) can be run in lean stratified mode, while the remaining cylinders (i.e., cylinders more prone to absorption-induced misfires) are run rich, maintaining an overall exhaust air-fuel ratio at or near stoichiometry. The degree of leanness can be adjusted based on the amount of condensate received at the cylinder, allowing for a sufficient increase in engine airflow. The water absorption sensitivity of the cylinders can be determined based on engine speed-load conditions at the time of discharge, the amount of condensate received in each cylinder, engine configuration, cylinder firing order, and other factors.Adjusting the timing of a cylinder's fuel injection for a change from homogeneous combustion to lean stratified combustion can involve changing the first fuel injection timing from an intake stroke to a compression stroke, increasing the number of injections per combustion event, setting a fuel supply split ratio between injections, etc.

[0007] In this way, condensate can be periodically cleared from an intercooler by operating one or more cylinders in a lean, stratified mode. By adjusting the fuel injection timing of a cylinder to increase the airflow level to a height that allows condensate to be blown off the CAC, purging can be performed without waiting for a tip-in event. Simultaneously, adjusting the fuel injection timing to provide stratified fuel injection maintains a rich environment near the cylinder's spark plug, allowing for more stable combustion. By adjusting the fuel injection timing in such a way as to maintain an overall air-fuel ratio at stoichiometry, engine performance is improved during purging.

[0008] It is understood that the above summary is provided to introduce, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify any key or essential features of the claimed subject matter, the scope of which is defined solely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate any disadvantages mentioned above or in any part of this disclosure. Fig. Figure 1 is a schematic graphical representation of an exemplary power engine system that includes an intercooler. Fig. Figure 2 shows an exemplary combustion chamber of the engine system according to Fig. 1. Fig. Figure 3 shows a high-level flowchart of a procedure for adjusting engine fuel supply during condensate draining from a charge air cooler (CAC) based on the water absorption sensitivity of each cylinder. Fig. Figure 4 shows a high-level flow diagram of a procedure for adjusting fuel injection during the draining of condensate from a charge air cooler (CAC) in order to temporarily operate one or more engine cylinders in a lean stratified mode. Fig. Figure 5 shows an example lookup table that can be used to store data regarding the water absorption sensitivity of the power engine cylinders. Fig. Figure 6 shows a high-level flow diagram of a procedure for determining a degree of richness for the ‘weak’ cylinders based on the combustion stability limits and for adjusting the degree of leanness of the ‘strong’ cylinders in accordance. Fig. Figure 7 shows a high-level flowchart of a procedure for determining a degree of leanness of the “strong” cylinders based on a limit of the lean stratified mode and for adjusting the degree of fatness for the “weak” cylinders in accordance. Fig. Figure 8 shows a diagram illustrating a relationship between the strength of the strong cylinders and the required degree of leanness, and the weakness of the weak cylinders and the required degree of fatness. Fig. Figure 9 shows a graphical example of adjusting the fuel injection into one or more cylinders during emptying based on their respective water absorption sensitivities. Fig. Figure 10 shows a graphical example of adjusting the air-fuel ratio of one or more engine cylinders during emptying in order to operate at least some cylinders in a lean stratified mode.

[0009] The following description refers to systems and methods for draining condensate from a charge air cooler (CAC) to a powertrain system, such as the system according to the Fig. 1-2. During emptying, the power machine airflow can be temporarily increased while a power machine actuator, such as the spark timing controller, is adjusted in response to the condensate flow. Emptying of the CAC condensate can occur in response to increased condensate levels. A power machine controller can be configured to execute a control routine, such as the routine after Fig. 3, to adjust the fuel supply to each cylinder during emptying based on the water absorption sensitivity of each cylinder ( Fig. 5) to set. Alternatively, the controller can run the example routine after Fig. 4. Execute to adjust the fuel injection timing so that a lean stratified combustion mode of the cylinders is provided. The controller can run one or more cylinders rich, while other cylinders run lean, with degrees of richness and leanness set to maintain exhaust emissions. Fig. 6-8). In each case, the engine airflow is increased to blow the condensate into the engine cylinder, thereby reducing the occurrence of misfires caused by the intake. Exemplary fuel settings that can be used to draw the condensate from a CAC and drain it into an engine intake are given with reference to the Fig. Shown 9-10.

[0010] Fig. Figure 1 is a schematic graphical representation showing an example power engine 10 that may be included in a propulsion system of a motor vehicle. The power engine 10 is shown with four cylinders 30. However, in accordance with the current disclosure, other numbers of cylinders may be used. The power engine 10 may be controlled at least partially by a control system that includes a controller 12 and by input from an operator 132 of the vehicle via an input device 130. In this example, the input device 130 includes an accelerator pedal and a pedal position sensor 134 to generate a proportional pedal position signal PP. Each combustion chamber (e.g., each cylinder) 30 of the power engine 10 may contain combustion chamber walls in which a (in Fig. 2 (discussed) piston is positioned. The pistons can be coupled to a crankshaft 40, so that the reciprocating motion of the piston is converted into a rotary motion of the crankshaft. The crankshaft 40 can be coupled to at least one drive wheel of a vehicle via an intermediate gear system (not shown). Furthermore, a starter motor can be coupled to the crankshaft 40 via a flywheel to enable a starting operation of the engine 10.

[0011] The combustion chambers 30 can receive intake air from the intake manifold 44 via an intake port 42 and can discharge the combustion gases to the exhaust port 48 via an exhaust manifold 46. The intake manifold 44 and the exhaust manifold 46 can be selectively connected to the combustion chamber 30 via corresponding intake and exhaust valves (not shown). In some embodiments, the combustion chamber 30 can contain two or more intake valves and / or two or more exhaust valves.

[0012] It is shown that the fuel injectors 66 are directly coupled to the combustion chamber 30 to inject the fuel directly into it, proportional to the pulse width of the FPW signal received by the controller 12. In this way, the fuel injector 66 provides what is known as direct injection of the fuel into the combustion chamber 30; however, it is recognized that port injection is also possible. The fuel can be supplied to the fuel injector 66 by a fuel system (not shown) comprising a fuel tank, a fuel pump, and a fuel distributor.

[0013] The intake duct 42 can contain a throttle valve 21 with a throttle plate 22 to control the airflow to the intake manifold. In this particular example, the position (TP) of the throttle plate 22 can be varied by the controller 12 to enable electronic throttle control (ETC). In this way, the throttle valve 21 can be actuated to modify the intake air supplied to the combustion chamber 30 between other engine cylinders. In some embodiments, additional throttle valves may be present in the intake duct 42, such as a throttle valve upstream of the (not shown) supercharger.

[0014] Furthermore, in the disclosed embodiments, an exhaust gas recirculation (EGR) system can direct a controlled proportion of the exhaust gas from the exhaust port 48 via an EGR port 140 to the intake port 42. The amount of EGR supplied to the intake port 42 can be varied by the controller 12 via an EGR valve 142. Under certain conditions, the EGR system can be used to control the temperature of the air-fuel mixture within the combustion chamber. Fig. Figure 1 shows a high-pressure EGR system, wherein the EGR is routed from a location upstream of a turbocharger turbine to a location downstream of a turbocharger compressor. In other embodiments, the engine may additionally or alternatively include a low-pressure EGR system, in which the EGR is routed from a location downstream of a turbocharger turbine to a location upstream of a turbocharger compressor. When the EGR system is operational, it can cause the formation of condensate from the compressed air, particularly when the compressed air is cooled by the charge air cooler, as described in more detail below.

[0015] The engine 10 may further include a compression device, such as a turbocharger or a supercharger, which includes at least one compressor 162 arranged along the inlet manifold 44. In the case of a turbocharger, the compressor 162 may be driven at least partially by a turbine 164, for example, via a shaft or other coupling arrangement. The turbine 164 may be arranged along the outlet port 48. Various arrangements may be provided for driving the compressor. In the case of a supercharger, the compressor 162 may be driven at least partially by the engine and / or an electric motor and may not include a turbine. Consequently, the amount of compression supplied to one or more cylinders of the engine via a turbocharger or supercharger can be varied by the controller 12.

[0016] Furthermore, the exhaust port 48 can contain a boost pressure control valve 171 to redirect the exhaust gas away from the turbine 164. Additionally, the intake port 42 can contain a compressor return valve (CRV) 27 configured to redirect the intake air around the compressor 162. The boost pressure control valve 171 and / or the CRV 27 can be controlled by the controller 12 to be open when, for example, a lower boost pressure is desired.

[0017] The inlet duct 42 may further include a charge air cooler (CAC) 80 (e.g., an intercooler) to reduce the temperature of the intake gases charged by the turbocharger or supercharger. In some embodiments, the charge air cooler 80 may be an air-to-air heat exchanger. In other embodiments, the charge air cooler 80 may be an air-to-liquid heat exchanger. The CAC 80 may also be a variable-volume CAC, wherein the charge air cooler 80 includes a valve to selectively modulate the quantity and flow rate of the intake air moving through the charge air cooler 80 in response to both condensation within the charge air cooler and the engine load conditions.

[0018] In both the variable and non-variable embodiments of the CAC 80, draining of the stored condensate can be enabled in response to a condensate level exceeding a threshold. As elaborated here, draining can be performed opportunistically during conditions when the power engine airflow is higher, such as during a tip-in event. Alternatively, the power engine airflow can be actively increased, for example, by widening a throttle valve opening, to drain the condensate while a power engine actuator, such as the spark timing control, is adjusted to maintain the power engine's torque output. As further elaborated here, draining can also be enabled by temporarily operating the power engine in a stratified mode.Specifically, the timing of fuel injection into one or more engine cylinders can be adjusted so that at least some cylinders operate in a lean stratified mode. The degree of leanness can be adjusted so that the level of engine airflow (the mass airflow) is at a level that causes condensate blow-off. By increasing the mass airflow high enough above the mass flow required to initiate condensate discharge from the CAC, but not high enough to cause misfires and poor combustion, the condensate can be removed without the adverse effects of poor combustion.

[0019] As such, the water absorption sensitivity of engine cylinders can vary, with some cylinders exhibiting higher water absorption sensitivity (e.g., being more prone to misfires caused by absorption) and other cylinders exhibiting lower water absorption sensitivity (e.g., being less prone to misfires caused by absorption). This variation can be due to factors such as engine geometry, the location of the cylinders in an engine inline, and the firing order. In other words, the shape of the exhaust manifold can typically determine which cylinder(s) receive the condensate. In an inline engine, for example, the cylinders furthest from the CAC (condensate absorption curve) may be more sensitive to water absorption than the cylinders closest to the CAC. As another example, in a V-engine (e.g., a V-twin), the cylinders furthest from the CAC may be more sensitive to water absorption than those closest to it.In a V-6 configuration, the cylinders furthest from the throttle inlet receive more condensate than those closer to it. For example, the left bank may experience more water absorption if the throttle body points towards it. Because water is denser than air, the condensate does not bend around the inlet bends, allowing it to reach the end of the inlet and flow into the furthest cylinders. As yet another example, cylinders in one row may be more sensitive than those in the other. Furthermore, the presence of additional bends in the inlet can direct a majority of the discharged condensate into essentially one specific cylinder.

[0020] In some embodiments, the water absorption sensitivity may be correlated with the amount (or percentage) of condensate that the cylinders are likely to receive. This is because, when the engine airflow is increased to drain the condensate, the amounts of condensate may flow unevenly to the engine cylinders, with some cylinders receiving larger amounts of condensate than others. In this context, cylinders receiving larger amounts of condensate may be more prone to misfires and other combustion problems (i.e., exhibit higher water absorption sensitivity), while other cylinders receiving smaller amounts of condensate may be less prone to misfires and other combustion problems (i.e., exhibit lower water absorption sensitivity).

[0021] The sensitivity to water absorption can also change with the engine's speed-load conditions. For example, a particular cylinder (or set of cylinders) might be more sensitive to water absorption under low engine speed-load conditions, while an alternative cylinder (or set of cylinders) might be more sensitive under low to medium engine speed-load conditions. Alternatively, the sensitivity to water absorption of all cylinders might be lower under low engine speed-load conditions because the intake airflow is too low at low engine speeds and / or loads to carry water from the CAC to the intake manifold.In another example, under conditions of high engine speed and high engine load, the water absorption sensitivity of all cylinders may be higher due to the increased airflow, which draws the condensate from the CAC and carries it into the intake manifold. Furthermore, if the airflow is sufficiently strong, under conditions of high engine speed and low engine load, the cylinders may be most susceptible to water absorption due to the poor combustion stability of these cylinders under light load conditions.Because the shape of the manifold largely determines which cylinders absorb the condensate, in another example, a particular cylinder (or set of cylinders) may be more susceptible to water absorption under high engine speed-load conditions, while an alternative cylinder (or set of cylinders) may be more susceptible to water absorption under low to medium engine speed-load conditions.

[0022] Differences in water absorption sensitivity between cylinders can be derived or estimated based on operating conditions. Alternatively, the engine can be characterized during testing using a dynamometer. Specifically, water vapor can be introduced into the air intake system during testing, and cylinder pressure data can be used to characterize the effect of the water. The cylinders can then be mapped to identify the "weak" cylinders with high water absorption sensitivity and the "strong" cylinders with low water absorption sensitivity. The map can be stored in the controller's memory (e.g., as a function of the engine's speed-load conditions) and retrieved during a draining operation.As detailed here, the fuel supply to each cylinder can be adjusted based on its water absorption sensitivity to compensate for differences in water absorption sensitivity and / or uneven condensate flow along the cylinders during venting. For example, the "weak" cylinders (those with higher water absorption sensitivity) can be run rich, while the "strong" cylinders (those with lower water absorption sensitivity) can be run lean. A degree of leanness can be set for the lean-running cylinders, allowing the engine airflow to be increased to or above a blow-off level that enables condensate to be vented from the CAC.Then, the richness of the rich-running cylinders is adjusted based on the leanness of the lean-running cylinders, so that the overall air-fuel ratio of the exhaust gases (as seen through an exhaust catalyst) can be maintained at or around stoichiometry (e.g., oscillating around stoichiometry). In an example where water absorption sensitivity is caused by uneven condensate uptake, the controller can run the cylinders receiving more condensate rich while running the cylinders receiving less lean, maintaining an overall air-fuel ratio of the exhaust gases at or around stoichiometry.By adjusting the fuel supply to each cylinder, taking into account the water absorption sensitivity of each cylinder, the condensate can be drained without impairing cylinder combustion and without suffering frequent misfires.

[0023] The Controller 12 is in Fig. 1 is shown as a microcomputer comprising a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory chip 106, a read / write memory 108, a hold memory 110 and a data bus.In addition to the signals previously discussed, the controller 12 can receive various signals from sensors coupled to the engine 10, including the measurement of the input mass airflow (MAF) from the mass airflow sensor 120; the engine coolant temperature (ECT) from a temperature sensor 112, which is shown schematically at a location within the engine 10; a profile ignition response (PIP) signal from a Hall effect sensor 118 (or another type) coupled to the crankshaft 40; a throttle position (TP) signal from a throttle position sensor, as discussed; and an absolute manifold pressure (MAP) signal from a sensor 122, as discussed, to perform various functions for operating the engine 10. A power machine speed signal, RPM, can be generated from the PIP signal by the controller 12.The manifold pressure signal MAP from a manifold pressure sensor can be used to provide an indication of the vacuum or pressure in the intake manifold 44. It is stated that various combinations of the above sensors can be used, such as a MAF sensor without a MAP sensor or vice versa. During stoichiometric operation, the MAP sensor can provide an indication of the engine torque. Furthermore, this sensor, together with the detected engine speed, can provide an estimate of the charge (including air) introduced into the cylinder. In one example, the sensor 118, which is also used as an engine speed sensor, can generate a predetermined number of equally spaced pulses at each revolution of the crankshaft 40.

[0024] Other sensors that can send signals to the controller 12 include a temperature sensor 124 at the outlet of the charge air cooler 80 and a boost pressure sensor 126. Still other sensors include a knock sensor 90 coupled to the engine block. The controller can determine the condensate consumption at one or more engine cylinders during condensate draining based on the cylinder knock frequency. Other sensors, not shown, may also be present, such as a sensor for determining the velocity of the intake air at the charge air cooler inlet and other sensors, as shown in Fig. 2 is described. In some examples, the read-only memory 106 of the storage medium can be programmed with computer-readable data representing instructions executable by the processor 102 for carrying out both the procedures described below and other variants that are anticipated but not specifically listed. Example routines are given here in the Fig. 3-4 described.

[0025] In Fig. Figure 2 is a detailed embodiment of a cylinder of the power engine according to Fig. 1 shown. As such, the previously in Fig. 1 introduced components in Fig. The two components are numbered identically and are not reintroduced. The engine 10 contains a combustion chamber (a cylinder) 30 and the cylinder walls 32, with the piston 36 positioned therein and connected to a crankshaft 40. The combustion chamber 30 is shown to be connected to an intake manifold 46 and an exhaust manifold 48 via an intake valve 52 and an exhaust valve 54, respectively. Each intake and exhaust valve can be actuated by an intake cam 51 and an exhaust cam 53. The opening and closing timing of the exhaust valve 54 can be adjusted relative to the camshaft position by a camshaft adjuster 58. The opening and closing timing of the intake valve 52 can be adjusted relative to the camshaft position by a camshaft adjuster 59. The position of the intake cam 51 can be determined by an intake cam sensor 55.The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57. In this way, the controller 12 can control the cam timing via the camshaft adjusters 58 and 59. The variable cam timing (VCT) can be advanced or retarded depending on various factors, such as engine load and engine speed (RPM).

[0026] It is shown that the direct injection nozzle 66 is positioned to inject fuel directly into the combustion chamber 30, a process known to those skilled in the art as direct injection. Alternatively, the fuel can be injected into an inlet port to provide port fuel injection. The direct injection nozzle 66 supplies liquid fuel proportional to the pulse width of the FPW signal from the controller 12. The fuel is supplied to the direct injection nozzle 66 by a fuel system (not shown) comprising a fuel tank, fuel pump, and fuel distributor (not shown). Operating current is supplied to the fuel injection nozzle 66 by a driver 68 that responds to the controller 12. In one example, a two-stage high-pressure fuel system is used to generate higher fuel pressures.Furthermore, it is shown that the intake manifold 46 is connected to an optional electronic throttle valve 62, which sets the position of a throttle plate 64 to control the airflow from an intake charging chamber 44. A compressor 162 draws air from the air intake 42 to supply the intake charging chamber 44. The exhaust gases drive the turbine 164, which is coupled to the compressor 162, compressing the air in the charging chamber 44. Various arrangements can be provided to drive the compressor. For a supercharger, the compressor 162 can be driven at least partially by the engine and / or an electric motor and may not include a turbine. Consequently, the amount of compression supplied to one or more cylinders of the engine via a turbocharger or supercharger can be varied by the controller 12.The turbocharger boost pressure control valve 171 is a valve that allows exhaust gases to bypass the turbine 164 via a bypass channel 173 when the turbocharger boost pressure control valve 171 is in an open state. When the boost pressure control valve 171 is in a fully closed position, essentially all exhaust gas passes through the turbine 164.

[0027] An exhaust gas recirculation (EGR) system can route a specified proportion of the exhaust gas from the exhaust manifold 48 via an EGR channel 140 to the intake charging chamber 44. The amount of EGR supplied to the intake charging chamber 44 can be varied by the controller 12 via an EGR valve 172. Under certain conditions, the EGR system can be used to regulate the temperature of the air-fuel mixture within the combustion chamber. The EGR system can cause condensation to form from the compressed air, especially when the compressed air is cooled by the charge air cooler, as described in more detail below. Specifically, the EGR contains a large amount of water, as it is a combustion byproduct. Because the EGR is at a relatively high temperature and contains a significant amount of water, the dew point temperature can also be relatively high.Consequently, the condensate formation from the EGR can be much higher than the condensate formation from compressing the air and lowering the air to the dew point temperature.

[0028] The inlet charging chamber 44 may further include an intercooler (CAC) 166 (e.g., an intercooler) to reduce the temperature of the intake gases charged by the turbocharger or supercharger. In some embodiments, the CAC 166 may be an air-to-air heat exchanger. In other embodiments, the CAC 166 may be an air-to-liquid heat exchanger. The CAC 166 may include a valve to selectively modulate the flow rate of the intake air passing through the intercooler 166 in response to condensation within the intercooler.

[0029] The hot charge air from the compressor 162 enters the inlet of the CAC 166, cools as it passes through the CAC 166, and then exits to pass through the throttle valve 62 and into the intake manifold 46 of the engine. An ambient airflow from outside the vehicle can enter the engine 10 through the front of the vehicle and pass over the CAC to assist in cooling the charge air. If the ambient air temperature decreases, or during humid or rainy weather conditions, condensation can form and accumulate in the CAC if the charge air is cooled below the water dew point. If the charge air contains recirculated exhaust gases, the condensate can become acidic and corrode the CAC housing. This corrosion can lead to leaks between the air charge, the atmosphere, and potentially the coolant in the case of water-to-air coolers.To reduce condensate accumulation and the risk of corrosion, the condensate can be collected at the bottom of the CAC and then discharged into the engine during selected operating conditions, such as acceleration events. However, if the condensate is introduced into the engine all at once during an acceleration event, it can increase the likelihood of engine misfire or combustion instability (in the form of delayed / slow combustion) due to water absorption. Consequently, as discussed here with reference to the... Fig. As detailed in section 3-4, the condensate is drained from the CAC to the engine under controlled conditions. This controlled draining can help reduce the likelihood of engine misfires. For example, the condensate can be drained from the CAC using an increased airflow.

[0030] The distributorless ignition system 88 provides a spark to the combustion chamber 30 via a spark plug 92 in response to the controller 12. A universal exhaust gas oxygen sensor (UEGO sensor) 126 is shown to be coupled to the exhaust manifold 48 upstream of the turbine 164. Alternatively, the UEGO sensor 126 can be replaced by a dual-state exhaust gas oxygen sensor.

[0031] In some examples, the power unit may be coupled to an electric motor / battery system in a hybrid vehicle. The hybrid vehicle may have a parallel configuration, a series combination, or a variation or combination thereof. Furthermore, other power unit configurations may be used in some examples, such as a diesel engine.

[0032] During operation, each cylinder in the engine 10 typically goes through a four-stroke cycle: the cycle includes the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. Generally, during the intake stroke, the exhaust valve 54 is closed and the intake valve 52 is open. Air is introduced into the combustion chamber 30 via the intake manifold 46, with the piston 36 moving towards the bottom of the cylinder to increase the volume in the combustion chamber 30. The position in which the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 is at its largest volume) is typically referred to by those skilled in the field as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves towards the cylinder head to compress the air in the combustion chamber 30.The point at which the piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber 30 is at its smallest volume) is typically referred to by those skilled in the field as top dead center (TDC). In a process referred to below as injection, the fuel is introduced into the combustion chamber. In a process referred to below as ignition, the injected fuel is ignited by known ignition means, such as a spark plug 92, resulting in combustion. The spark timing can be controlled so that the spark occurs before (advanced) or after (retarded) the manufacturer's specified time. The spark timing can, for example,The maximum braking torque (MBT) timing can be retarded to control engine knock, or advanced under high humidity conditions. In particular, the MBT can be advanced to accommodate the slow combustion rate. During the power stroke, the expanding gases push the piston 36 back to the BDC. The crankshaft 40 converts the piston movement into a torque of the rotating shaft. The crankshaft 40 can be used to drive a three-phase generator 168. Finally, during the exhaust stroke, the exhaust valve 54 is open to expel the burnt air-fuel mixture to the exhaust manifold 48, with the piston returning to the TDC. It should be noted that the above has been shown only as an example and that the opening and / or closing times of the intake and exhaust valves may change, for example,to provide positive or negative valve overlap, late closing of the intake valve, or various other examples.

[0033] The controller 12 receives various signals from sensors coupled to the power unit 10, including those previously discussed. The controller 12 can communicate with various actuators, which may include the power unit actuators, such as the fuel injectors, an electronically controlled intake air throttle plate, spark plugs, camshafts, etc. The various power unit actuators can be controlled to provide or maintain the torque requirement as specified by the vehicle operator 132. These actuators can adjust certain control parameters of the power unit, including variable cam timing (VCT), air-fuel ratio (AFR), alternator load, spark timing, throttle position, etc. For example, if an increase in power delivery (PP) (e.g.,During a tip-in, the torque requirement is increased when the pedal position sensor 134 indicates a torque requirement.

[0034] In Fig. Figure 3 shows an example routine 300 for draining the condensate from a CAC while adjusting the fuel supply to the engine cylinders to compensate for uneven condensate flow and variations in water absorption sensitivity. By increasing the engine airflow while adjusting the fuel supply to the cylinders based on their condensate sensitivity, the condensate can be drained without increasing the frequency of misfires or other combustion problems.

[0035] At 302, the routine involves estimating and / or measuring the engine's operating conditions. These may include the driver's torque request (based on a pedal position), engine speed (Ne) and load, ECT, boost pressure, ambient temperature, MAF, MAP, EGR quantity, air-fuel ratio (A / F), ambient humidity, ambient pressure, BP, engine temperature, exhaust catalyst temperature, CAC conditions (intake and exhaust temperature, intake and exhaust pressure, flow velocity through the CAC, etc.), and other parameters.

[0036] In procedure 304, the routine involves determining the level (or quantity) of condensate stored in the CAC. This may involve retrieving details such as ambient air temperature, ambient air humidity, inlet and outlet charge air temperature, and inlet and outlet charge air pressure from multiple sensors and using these variables to determine the quantity of condensate formed in the CAC. The condensate level can be estimated based on the air mass flow rate, ambient temperature, CAC outlet temperature, CAC pressure, ambient pressure, or an EGR quantity. The condensate level can also be based on an input from a humidity sensor.In one example, reference 306 uses a model to calculate the condensate levels in the CAC based on ambient temperature, CAC outlet temperature, mass flow rate, EGR, humidity, and other factors. This model uses ambient temperature and humidity values ​​to determine the dew point of the inlet air, which can be further influenced by the amount of EGR in the inlet air (the EGR may have a different humidity and temperature than the ambient air). The difference between the dew point and the CAC outlet temperature indicates whether condensation forms within the cooler, with the air mass flow rate affecting the actual amount of condensation that accumulates.

[0037] In another example, Figure 308 maps condensate levels to the CAC outlet temperature and a ratio of CAC pressure to ambient pressure. Alternatively, the condensation value can be mapped to the CAC outlet temperature and engine load. The engine load can be a function of air mass, torque, accelerator pedal position, and throttle position, and can therefore provide an indication of the airflow velocity through the CAC. For example, a moderate engine load combined with a relatively cool CAC outlet temperature can indicate a high condensation value due to the cold CAC surfaces and the relatively low intake airflow velocity. In one example, the mapping can include an ambient temperature modifier. In another example, a CAC pressure-to-ambient pressure ratio can be used to estimate condensation.This allows the engine load in the intake manifold (behind the throttle valve) to be normalized and estimated, so that it could be a lower pressure than in the CAC.

[0038] At 310, the determined condensate level can be compared with a threshold level to determine whether the draining conditions have been met. The threshold level can be an upper threshold for condensate storage. If the condensate level is not higher than the threshold level, then at 312 it can be determined that the draining conditions have not been met, and a draining cycle is not initiated.

[0039] If the condensate level is higher than the threshold level, then routine 314 includes determining the water absorption sensitivity of the engine cylinders under the given operating conditions. For example, the water absorption sensitivity of the engine cylinders may have been determined during engine testing (e.g., based on an output from a dynamometer) and stored in the controller's memory in a lookup table (e.g., as a function of engine speed-load). The controller can then retrieve the data from the lookup table. An example lookup table is provided at 500. Fig. Figure 5 shows the engine as a 4-cylinder in-line engine with a firing order of 1, 3, 4, 2. Based on test data for a given engine speed-load condition, cylinders exhibiting higher water absorption sensitivity may be marked as "weak," while cylinders exhibiting lower water absorption sensitivity may be marked as "strong." For example, under low engine speed and low engine load conditions, all cylinders are considered strong because the mass airflow under these conditions is not high enough to draw the condensate out of the CAC.In comparison, under conditions of high engine speed and low engine load, all cylinders can be considered weak because the air mass flow rate is high enough to draw the condensate out of the CAC, although the low engine load leads to poor combustion stability. In another example, under conditions where the cylinders are sufficiently hot, none of the cylinders can be considered weak.

[0040] It is recognized that, in an alternative example, a given set of cylinders may be consistently prone to condensate absorption across the engine speed-load range. This may be because, generally, condensate absorption is a problem most often experienced under conditions of high engine speed and / or high engine load, where the mass airflow is high enough to draw the condensate out of the condensate intake airflow (CAC). Furthermore, at light loads at low or high engine speeds, the mass airflow may be unlikely to be high enough to draw the condensate out. In yet other engine configurations, a device such as a charge motion control valve or an air chamber communication valve may be incorporated in the intake manifold that can sufficiently alter the manifold dynamics to affect condensate distribution within the intake manifold.

[0041] On the 316, the more powerful cylinders with lower water absorption sensitivity can be selected for lean engine operation. Furthermore, a degree of leanness can be set for the selected cylinders to increase the engine airflow to or above a threshold level (also referred to here as the blow-off level) that allows condensate to be expelled. This is achieved by increasing the opening of the intake throttle valve based on the requested degree of leanness. The degree of leanness can be selected to provide an increased level of engine airflow based on the estimated condensate level in the charge air cooler and the engine's operating conditions. For example,As the condensate level increases, a degree of leanness can be planned to increase the power engine airflow to or above a threshold level required to remove the water from the CAC at a controlled rate.

[0042] This means that by running one or more of the engine cylinders lean (here, by running the high-output cylinders lean), the level of the engine airflow is increased to or above a blow-off level required to drain the condensate from the charge air cooler. This increase is based on both the condensate level in the charge air cooler and the rate at which the condensate should be introduced into the engine (which, in turn, is based on the rate at which it can absorb the condensate while minimizing the effect on combustion). Increasing the airflow velocity raises the airflow velocity for drawing the condensate out of the charge air cooler, thus draining the condensate into the engine.

[0043] At 318, the routine includes selecting the weaker cylinders with higher water absorption sensitivity for rich engine operation. Specifically, the degree of richness in the rich-running cylinders can be adjusted based on the degree of leanness in the lean-running cylinders to maintain the overall air-fuel ratio of the exhaust gases oscillating around stoichiometry.

[0044] During the drain cycle, unequal amounts of condensate can flow from the intercooler to the cylinders. This variation can be largely a function of both the geometry of the intake manifold and the physics of the path the condensate takes through the manifold. The amount of condensate flowing into each engine cylinder can change based on engine speed and / or engine geometry (e.g., an inline engine versus a V-engine, a 4-cylinder engine versus a 6-cylinder engine, etc.) and / or the cylinder position within the engine block (e.g., close to or farther from the CAC) and / or the cylinder firing order. For example, cylinders located farther from the CAC outlet and the throttle inlet may receive more condensate during drain than those located closer to the CAC outlet or the throttle inlet.In particular, due to the momentum of the water flow towards the rear of the intake manifold, condensate can strike the rear of the manifold and be directed into the rear cylinders. As another example, the cylinders may receive more condensate under higher engine speed-load conditions and less under lower engine speed-load conditions. In addition to the design of the manifold and combustion system, this uneven distribution of discharged condensate among the engine cylinders may at least partially account for the differences in the cylinders' sensitivity to water absorption. This sensitivity may also be due to other engine operating conditions. For example, if a particular cylinder receives more residue and also receives above-average amounts of condensate, it may misfire first.

[0045] A degree of enrichment of the richly fueled cylinders and a degree of leaning of the leanly fueled cylinders can be set based on a number of cylinders with higher water absorption sensitivity and a number of cylinders with lower water absorption sensitivity, and further based on the amount of condensate that is drained, in order to maintain the air-fuel ratio of the exhaust gases (as received by an exhaust gas purification device, such as a three-way catalytic converter).

[0046] As will be explained below in Fig. As elaborated in section 6, tuning may involve first determining the degree of leanness in the high-power cylinders to provide a level of engine airflow that allows condensate to be blown off, and then adjusting the degree of richness in the low-power cylinders to provide a stoichiometric overall air-fuel ratio in the exhaust gases. In other words, the degree of leanness in the low-power cylinders may be the limiting factor. However, in alternative examples, tuning may involve first determining the degree of richness required to address combustion stability issues (such as a tendency to misfire) in the low-power cylinders, and then adjusting the degree of leanness in the high-power cylinders to provide a stoichiometric overall air-fuel ratio in the exhaust gases. In other words, the degree of richness in the low-power cylinders may be the limiting factor.

[0047] In one example, cylinders receiving more than a threshold amount of condensate are run rich, with a degree of richness and a spark advance amount based on the number of cylinders receiving more condensate than the threshold amount and the number of cylinders receiving less condensate than the threshold amount. Conversely, cylinders receiving less than the threshold amount of condensate are run lean, with a degree of leanness based on the number of cylinders receiving more condensate than the threshold amount and the number of cylinders receiving less condensate than the threshold amount. Thus, the sum of the lean and rich operating conditions of a given cylinder bank can be set and maintained at or near stoichiometry to maintain emissions.Both the degree of richness in the rich-running cylinders and the degree of leanness in the lean-running cylinders can also be based on a difference between the amount of condensate received and the threshold amount. An example of a fuel injection setting is given with reference to... Fig. 9 shown.

[0048] At 320, the routine includes adjusting a power engine actuator based on both the increased power engine airflow (as well as the reduced torque output of the lean cylinders and the slightly increased torque output of the rich cylinders) to maintain power engine torque (rich for best torque (RBT) only increases torque by 1-2%). This allows the power engine airflow to be increased without increasing the power engine torque. The adjusted power engine torque actuator may include the spark timing and / or the variable cam timing and / or the alternator load. While the power engine airflow is increased, in one example, the spark timing in the rich-running cylinders may be advanced (e.g., advanced from the nominal MBT) because they are likely to have slower combustion due to water absorption.As such, the slowing of combustion means that the MBT is advanced from a nominal position under standard test conditions. Simultaneously, spark advance can be maintained in the lean-running cylinders (e.g., maintained at the MBT). The richer air-fuel ratio also helps suppress knocking in the rich-running cylinders as the rate of condensate absorption decreases and the accumulated condensate is consumed. Here, spark advance is used to slightly reduce torque when needed. In an alternative example, spark advance can be advanced in all engine cylinders during condensate venting, with more spark advance applied to the rich-running cylinders (the weak cylinders) and less spark advance applied to the lean-running cylinders (the strong cylinders).

[0049] It is recognized that, in an alternative example, condensate draining can be performed opportunistically during a tip-in, with the increased engine airflow potentially resulting from the driver's tip-in. In such an embodiment, adjustments to the engine torque actuator may not be required simultaneously, and it may be permissible for the engine torque output to increase to meet the driver's increased torque demand. However, even during opportunistic draining, where the engine airflow is increased to or above the blow-off threshold in response to a tip-in, the controller can adjust the fuel delivery to each cylinder based on each cylinder's water absorption sensitivity.While the engine airflow is increased in response to a tip-in from the operator, the cylinders with higher water absorption sensitivity can be specifically enriched, while the cylinders with lower water absorption sensitivity can be leaned out, maintaining an overall exhaust air-fuel ratio at or around stoichiometry.

[0050] To compensate for uneven condensate flow and / or differences in water absorption sensitivity between cylinders, the controller can, during condensate flow, supply some cylinders with a lean mixture while others are supplied with a rich mixture, maintaining an air-fuel ratio in the engine's exhaust gases that oscillates around stoichiometry. Specifically, each cylinder can be fueled based on its water absorption sensitivity. Consequently, cylinders with higher water absorption sensitivity can be enriched, while those with lower sensitivity can be leaned out. Furthermore, the richer cylinders can be operated with additional spark advance to compensate for the slower combustion rate.Enrichment also helps reduce knocking as condensate consumption decreases, as the engine consumes the condensate. A knock sensor output can confirm that the intake has ended, indicating to the controller that normal operating conditions can be restored. In an example where water intake sensitivity correlates with uneven condensate distribution between cylinders, each cylinder can be fueled based on the amount of condensate received in that cylinder. Cylinders receiving more than a threshold amount of condensate will be enriched and their ignition timing advanced further, while cylinders receiving less than a threshold amount of condensate will be leaned out and their ignition timing advanced less.This means that to increase engine airflow without increasing engine torque, the ignition timing can be advanced for both the richly fueled and lean-fueled cylinders, with more advance for the richly fueled cylinders than for the lean-fueled cylinders. If the lean cylinder is running at a particularly lean stoichiometric mixture, such as an AFR of 15:1, at least some advance may be necessary because the combustion rate can be slow.

[0051] At 324, the condensate level in the CAC can be reassessed to determine whether sufficient drainage has occurred. Specifically, it can be determined whether the condensate level is below a threshold level, or more precisely, below a lower threshold level. The lower threshold level may reflect a lower limit for condensate storage in the CAC. Furthermore, the lower threshold level may include some leeway for hysteresis.

[0052] In an alternative example, instead of determining whether the condensate level has dropped sufficiently, it can be determined whether the condensate uptake in the cylinders has decreased (due to the condensate being consumed and no further condensate being taken in). For example, a knock signal output from a knock sensor can be analyzed. As discussed above, the rich running of the weak cylinders helps to reduce the knock tendency as condensate consumption decreases, just as the engine consumes the condensate. Based on the knock signal for the combustion events in the rich-running (and pre-ignition) cylinders, a controller can determine when all the condensate has been consumed. In response to an increase in the knock signal and knock frequency associated with the rich-running cylinders, it can be determined, for example, that condensate uptake in the cylinders has ceased.Accordingly, the rich running of the cylinders can be adjusted, as discussed below.

[0053] If the condensate level is still above the threshold level (or the knock frequency of the rich cylinders is below a threshold), the routine at 326 includes maintaining fuel delivery to each cylinder based on the cylinder's water absorption sensitivity while increasing the engine airflow to drain the condensate to the engine intake. In one example, rich running of some cylinders and lean running of some cylinders can continue for a few seconds while increasing the engine airflow, without increasing engine torque, to complete the draining process.

[0054] If it is determined that the condensate level is below the (lower) threshold level (or the rich cylinder knock frequency is above the threshold), then routine 328 includes stopping the discharge of condensate from the CAC to the engine inlet. This involves reducing the engine airflow back to a level based on the operator's torque request and stopping the fuel supply to the cylinders based on their water absorption sensitivity (or condensate absorption rates). Specifically, stoichiometric fuel supply to the engine cylinders can be resumed. Alternatively, an alternative nominal fuel supply to the cylinders can be resumed to provide a nominal combustion air-fuel ratio to the cylinders based on the engine operating conditions.Furthermore, the nominal spark timing control can be resumed. The spark timing control can, for example, be fed back to the MBT.

[0055] In Fig. 6. Routine 600 represents a procedure for determining the degree of richness of the weak cylinders and for adjusting the degree of leanness of the strong cylinders accordingly. As such, the routine can be described as follows: Fig. 6 as part of the routine after Fig. 3, specifically at 316-318, are executed.

[0056] At 602, the strong cylinders, which exhibit lower water absorption sensitivity, can be identified. The data for the strong cylinders can be obtained, for example, from the in Fig. The reference table disclosed in 5 can be accessed. At 604, a degree of leanness required to increase the engine airflow to a blow-off level with a deterioration of the combustion stability of the high-power cylinders can be determined. Based on the "power" of the cylinders, the number of high-power cylinders, and further based on the amount of air and / or condensate expected to flow into the cylinder, a degree of leanness of the lean fuel injection can be determined, for example. In one example, the controller can display a figure such as the Fig. after Fig. 8, is used to determine the degree of leanness required for the cylinder based on its "power," with the required degree of leanness increasing as the "power" of the strong cylinders increases. At 606, based on the determined degree of leanness, a degree of richness required to provide an overall exhaust air-fuel ratio at or around stoichiometry is calculated. Then, at 608, the required richness is distributed among the remaining "weak" cylinders, which have a higher sensitivity to water absorption. The required richness can be distributed evenly, with each of the strong cylinders receiving fuel with the same degree of richness. Alternatively, the required richness can be distributed unevenly, with each of the strong cylinders receiving a fuel injection having a richness based on the power of that cylinder.The controller can display a mapping, such as the . Fig. after Fig. 8, to use to determine the degree of richness required for each strong cylinder based on its respective ‘weakness’, with the degree of richness increasing as the ‘weakness’ of the weak cylinders increases, and further based on the target richness to maintain a stoichiometric exhaust gas.

[0057] The engine could be, for example, a 4-cylinder in-line engine, which at the time of discharge has one weak cylinder and three strong cylinders. Based on the weakness of the weak cylinder, a rich mixture of 0.95 lambda can be used for the weak cylinder, while the remaining strong cylinders operate at 1.017 lambda, so that the in-line engine essentially operates at 1.0 lambda. Alternatively, the lean mixture can be unevenly distributed, with a first strong cylinder operating at 1.015, a second strong cylinder at 1.0125, and a third cylinder at 1.0135. As another example, based on the weakness of the weak cylinder, a rich mixture of an AFR of 10:1 can be determined. Accordingly, the remaining strong cylinders can each receive an equal lean mixture of an AFR of 16:1 to provide an overall stoichiometric exhaust (i.e., an AFR of 14:1).Alternatively, the lean mixture can be distributed unevenly, with a first strong cylinder operating at an AFR of 16:1, a second strong cylinder operating at an AFR of 15:1, and a third cylinder operating at an AFR of 15.5.

[0058] In this way, the routine allows after Fig. 3 (and Fig. 6) Condensate removal with reduced combustion problems. By running the cylinders with higher water absorption sensitivity rich and with additional spark advance, the combustion stability of the cylinders most prone to misfiring when absorbing condensate is reduced. Simultaneously running the cylinders with lower water absorption sensitivity lean allows for increased engine airflow to facilitate condensate removal from the CAC while maintaining an overall exhaust air-fuel ratio around stoichiometric. This provides emissions benefits because the stoichiometric environment keeps the exhaust catalyst active and able to convert exhaust emissions.

[0059] It is recognized that in an alternative embodiment according to Fig. 6. The degree of fatness of the weak cylinders, which have a higher sensitivity to water absorption, is determined first ( Fig. 5) based on the “weakness” of the cylinders ( Fig. 8) the number of weak cylinders and furthermore based on the combustion stability of the cylinders. A degree of leanness of the lean-running cylinders can then be adjusted based on the degree of richness to provide an overall air-fuel ratio of the exhaust gases at or around the stoichiometry.

[0060] In one example, in response to increased condensate levels, one or more engine cylinders are run lean, increasing engine airflow without increasing engine torque to drain condensate from an intercooler to the engine cylinders. The engine cylinders can be selected for lean operation based on their sensitivity to water absorption. Here, the cylinders may receive unequal amounts of condensate. An air-fuel combustion ratio for each engine cylinder is set during the draining process based on the amount of condensate received and each cylinder's water absorption sensitivity. The cylinders receiving unequal amounts of condensate may include those receiving condensate based on engine speed-load conditions, engine geometry, cylinder position, and firing order.Increasing the engine airflow without increasing the engine torque may involve enlarging the opening of an intake throttle valve while advancing the spark timing for at least the rich-running cylinders. Adjusting the combustion air-fuel ratio of the cylinders on a cylinder-by-cylinder basis during emptying may involve operating a first engine cylinder, which has a water absorption sensitivity higher than a threshold, at a combustion air-fuel ratio richer than stoichiometry, and operating a second engine cylinder, which has a water absorption sensitivity lower than a threshold, at a combustion air-fuel ratio leaner than stoichiometry.The degree of richness of the first engine cylinder can be adjusted based on the degree of leanness of the second engine cylinder in order to maintain an overall air-fuel ratio of the exhaust gases at or around stoichiometry.

[0061] In another example, in response to increased condensate levels during operator tip-in, the engine airflow is increased to meet the torque demand, with condensate being opportunistically drained from the charge air cooler to the engine cylinders. Because the cylinders receive unequal amounts of condensate, the combustion air-fuel ratio for each engine cylinder is set on a cylinder-by-cylinder basis during the draining process, based on the amount of condensate received and each cylinder's water absorption sensitivity.

[0062] In another example, a power machine system comprises a power machine containing one or more cylinders and an intake manifold, a compressor coupled upstream of an intake throttle valve, an intercooler coupled downstream of the compressor, an accelerator pedal to receive a torque request from the operator, and a controller with computer-readable instructions.The instructions may include code to increase the opening of the intake throttle valve to increase airflow to the intake manifold while maintaining engine torque, in response to an amount of condensate stored in the charge air cooler that is higher than a threshold; and to supply fuel to each engine cylinder based on its respective water absorption sensitivities, while maintaining an exhaust air-fuel ratio at or around stoichiometry.The fuel mixture can include a rich mixture for the first cylinder, which is more sensitive to water absorption, and a lean mixture for the second cylinder, which is less sensitive to water absorption. The rich mixture and the lean mixture are adjusted to maintain the exhaust gas air-fuel ratio at or around stoichiometry. The richer cylinders can be operated with a higher level of spark advance to maintain torque during condensate absorption and improve robustness against knocking as the condensate absorption rate decreases as a function of the total stored condensate and the rate of condensate consumption by the engine.Maintaining engine torque can also involve advancing the ignition timing, adjusting (e.g., advancing or retarding) variable camshaft timing, and / or adjusting (e.g., increasing) an alternator load while increasing engine airflow. As such, the engine airflow is increased from an initial setting to a blow-off setting, the blow-off setting being based on the amount of condensate stored in the charge air cooler.

[0063] In another example, the engine process involves the uneven flow of condensate from an intercooler to the engine cylinders and the compensation of this uneven flow by running the cylinders receiving more condensate rich and the cylinders receiving less lean, while maintaining an overall exhaust gas air-fuel ratio at stoichiometry. The process further involves increasing the engine airflow to direct the condensate from the intercooler to an engine intake, the increase in engine airflow generating the uneven condensate flow. That is, the increased airflow empties the condensate from the CAC, which is then distributed unevenly along the engine cylinders due to the physical shape of the intake manifold.Increasing engine airflow can involve adjusting the leanness of the lean-running cylinders to raise the engine airflow level above a threshold, allowing condensate from the intercooler to flow to the engine cylinders. To increase engine airflow, the opening of an air intake throttle valve can be enlarged based on the leanness level. The amount of condensate flowing to each engine cylinder depends on the engine speed, engine geometry, cylinder position within the engine block, and / or the firing order of the cylinders.The controller can operate the cylinders that receive more condensate than a threshold amount in a rich mixture, with the degree of richness based on the number of cylinders receiving more condensate than the threshold amount and the number of cylinders receiving less condensate than the threshold amount. The controller can also operate the cylinders that receive less condensate than the threshold amount in a lean mixture, with the degree of leanness further based on the number of cylinders receiving more condensate than the threshold amount and the number of cylinders receiving less condensate than the threshold amount.

[0064] In Fig. Figure 4 shows an example routine 400 for draining the condensate from a CAC while adjusting the timing of the fuel injection of the engine cylinders. This procedure allows at least some engine cylinders to operate in a lean stratified mode during condensate draining, providing sufficient mass airflow to absorb the condensate. The reason a controller might choose to operate one or more engine cylinders in the lean stratified mode, if available, is that this operation would allow the overall lean operation of the "lean" or "stronger" cylinders, and consequently, incrementally increase airflow and condensate draining.Operating in lean stratified mode can involve running the entire engine in a completely lean stratified mode, or operating some cylinders in lean stratified mode while the other cylinders operate in a rich mode, thus maintaining an overall exhaust gas air-fuel ratio oscillating around stoichiometry. As such, operating the entire engine in lean stratified mode may only be possible for a short period until catalyst efficiency drops. After the entire engine has operated in lean stratified mode, a period of rich operation may be necessary to restore catalyst efficiency. The total period of lean stratified operation would be determined by the catalyst's oxygen storage capacity.By increasing the engine airflow while adjusting the timing of the cylinder fuel injection, the condensate can be drained without increasing the frequency of misfires or other combustion problems.

[0065] In 402, as in 302, the routine includes estimating and / or measuring the engine operating conditions, which include, but are not limited to, the driver's torque request (based on a pedal position), engine speed (Ne) and load, ECT, boost pressure, ambient temperature, MAF, MAP, EGR quantity, air-fuel ratio (A / F), ambient humidity, ambient pressure, BP, engine temperature, exhaust catalyst temperature, CAC conditions (intake and exhaust temperature, intake and exhaust pressure, flow velocity through the CAC, etc.).

[0066] In procedure 404, as in procedure 304, the routine involves determining the level (or quantity) of the condensate stored in the CAC. As in Fig. As discussed in section 3, the condensate level can be estimated based on the air mass flow rate, ambient temperature, CAC outlet temperature, CAC pressure, ambient pressure, EGR quantity, and / or input from a humidity sensor. Condensate levels can be modeled in 406 (as in 306) based on a model that calculates the rate of condensate formation within the CAC based on the ambient temperature, CAC outlet temperature, mass flow rate, EGR, humidity, etc. Alternatively, in 408 (as in 308), condensate levels can be mapped to the CAC outlet temperature and a ratio of CAC pressure to ambient pressure, or to the CAC outlet temperature and the engine load.

[0067] At 410, the determined condensate level can be compared to a threshold level to determine whether the draining conditions have been met. The threshold level can be an upper threshold for condensate storage. If the condensate level is not higher than the threshold level, then at 412 it can be determined that the draining conditions have not been met, and a draining cycle is not initiated. Furthermore, the fuel injection timing can be maintained on a (first) fuel injection timing that provides a homogeneous cylinder-air-fuel charge, which is ignited by a spark.

[0068] If the condensate level is higher than the threshold level, then in 414, the routine in response to the condensate level in the charge air cooler includes adjusting the fuel injection timing while increasing the engine airflow to a level greater than that requested by a vehicle operator. Specifically, the fuel injection timing can be switched from the first injection timing, which provides a homogeneous cylinder-air-fuel charge ignited by a single spark, to a second injection timing, which provides at least a somewhat stratified cylinder-air-fuel charge ignited by a single spark.

[0069] In particular, the fuel injection timing can be set to operate one or more engine cylinders in a lean stratified mode. As elaborated below, this can involve operating some cylinders in lean stratified mode while other cylinders operate at stoichiometry, resulting in an overall lean exhaust air-fuel ratio, or operating all cylinders in lean stratified mode, resulting in an overall lean exhaust air-fuel ratio. By operating at least a lean mixture temporarily, a manifold airflow velocity can be increased to or above a blow-off level sufficient to initiate condensate evacuation, but not high enough to cause misfiring and poor combustion.In yet another example, operating some cylinders in lean stratified mode can involve operating some cylinders lean while other cylinders are operated rich, so that an overall air-fuel ratio of the exhaust gases (such as that received at an exhaust three-way catalytic converter) is at or around the stoichiometry (e.g., oscillating around the stoichiometry).

[0070] Adjusting the fuel injection timing from the first timing to the second timing may, for example, in 416, involve setting the number of fuel injections per cylinder combustion event. The adjustment may also, for example, in 418, involve switching from the first injection timing, which includes an intake stroke injection, to the second injection timing, which includes a compression stroke injection. As the intake stroke injection is used here, it may include any of an early intake stroke injection (e.g., one that begins late in the exhaust stroke and ends early in the intake stroke), a mid-intake stroke injection (e.g., one that begins and ends in the intake stroke), and a late intake stroke injection (e.g., one that begins in the intake stroke and ends in the compression stroke), with the compression stroke injection including a late compression stroke injection.

[0071] In one example, the controller can change the fuel injection timing from a single intake stroke fuel injection to split fuel injection, which includes at least one compression stroke injection. The number of multiple injections can be based on the condensate level. As the condensate level exceeds the threshold, the controller can, for example, adjust the fuel injection timing to increase the number of fuel injections per engine cycle and to increase the ratio of fuel delivered during a compression stroke to that delivered during an intake stroke. The split ratio can also be determined by the required lean mixture. The intake injection (the intake stroke injection) can, for example,can be used to plan for an overall lean operation, while compression injection can be used close to the spark ignition to maintain a relatively combustible mixture around the spark plug.

[0072] The adjustment of the fuel injection timing may further involve setting the injection timing of all cylinders, with the timing of the "strong" cylinders, which have a lower sensitivity to water absorption (or those that absorb less condensate), set to the lean stratified mode, while the injection timing of the "weak" cylinders, which have a higher sensitivity to water absorption (or those that absorb more condensate), is set to a rich mode, so that an overall exhaust gas air-fuel ratio is maintained at or around stoichiometry, with at least the rich cylinders being operated with additional spark advance.

[0073] As with reference to Fig. As discussed in section 3, the water absorption sensitivity of the cylinders can be determined beforehand during the testing of the power machine and entered into a reference table (such as the table according to Fig. 5) be stored in the controller's memory.

[0074] In an alternative example, adjusting the fuel injection timing, instead of operating cylinders with lower water absorption sensitivity in lean stratified mode while cylinders with higher water absorption sensitivity operate in rich mode, maintaining an overall exhaust air-fuel ratio around stoichiometry, could involve operating cylinders with lower water absorption sensitivity in lean stratified mode while cylinders with higher water absorption sensitivity operate in stoichiometric mode, maintaining an overall exhaust air-fuel ratio lean. By not operating the weaker cylinders in a lean mode, the likelihood of misfires caused by condensate absorption in the weaker cylinders is reduced.

[0075] As such, the injection timing of the lean stratified mode can be adjusted for the selected cylinders, providing a richer air-fuel ratio near the spark plug, while maintaining an overall lean air-fuel ratio within the cylinder. Providing a richer air-fuel ratio around the spark plug enables more stable combustion. Conversely, providing an overall lean combustion air-fuel ratio in the cylinders increases the manifold airflow sufficiently to allow for condensate drainage.

[0076] At 422, a degree of leanness in the lean stratified mode can be set to increase the engine airflow to or above the blow-off level that allows condensate to be drained. That is, by operating in lean stratified mode, the engine airflow level is increased based on the condensate level in the charge air cooler. The engine airflow level is then increased to a blow-off level necessary to drain the condensate from the charge air cooler. Increasing the airflow velocity raises the airflow velocity for drawing the condensate out of the CAC, which then drains the condensate into the engine.

[0077] The degree of leanness can also be based on the sensitivity of the cylinders to receiving condensate. This is because the condensate cannot pass uniformly from the CAC into the engine cylinders. Specifically, more condensate may be released during an initial section of the drain cycle, while less may be released during a later section. To address this uneven condensate release, the controller can monitor the firing order of the cylinders so that those cylinders receiving more condensate during the initial section of the drain cycle (e.g., immediately after draining has started or earlier in the cylinder firing order) are set to have a lower degree of leanness, while those cylinders receiving more condensate during the later section of the drain cycle (e.g.,sometime after the draining process has started, or later in the firing order of the cylinders), which are more likely to receive less condensate, are adjusted to have a higher degree of leanness.

[0078] Certain cylinders may be more prone to condensate retention. By estimating the transport delay time for the condensate to travel from the CAC to the "prone" cylinders, and further based on how much condensate has accumulated (e.g., modeled or measured) and how much has been consumed, the controller can estimate the number of affected combustion cycles and the decay rate to adjust accordingly. Alternatively, the controller can use the knock sensor output as feedback to determine when the condensate has been cleared and when the air, fuel, and spark control should return to normal levels. For example, the completion of condensate absorption can be determined in response to an increase in knock frequency in rich-running cylinders.

[0079] The degree of richness in the remaining cylinders is then adjusted based on the degree of leanness, so that an overall air-fuel ratio of the exhaust gases is maintained around stoichiometry. By providing stoichiometric exhaust gas to a downstream exhaust aftertreatment device, an exhaust catalyst can be kept catalytically active, resulting in improved emissions performance.

[0080] As will be explained below in Fig. As detailed in section 7, the tuning process may involve first determining the degree of leanness required to operate the high-performance cylinders in lean stratified mode, and then adjusting the degree of richness in the low-performance cylinders to provide a stoichiometric overall air-fuel ratio in the exhaust gases (or, if required, a lean air-fuel ratio in the exhaust gases). In other words, the degree of leanness in the low-performance cylinders may be the limiting factor. This is because operation in lean stratified mode may require a threshold degree of leanness. Consequently, it may be necessary for the high-performance cylinders to operate at a degree of leanness that lies within the limit of the lean stratified mode. The degree of leanness may also be determined by the increase in airflow required to scavenge condensate and maintain torque output.

[0081] At 424, as at 324, the condensate level in the CAC can be reassessed to determine whether sufficient drainage has occurred. Specifically, it can be determined whether the condensate level is below a threshold level, specifically below a lower threshold level. The lower threshold level may reflect a lower threshold for condensate storage in the CAC. Furthermore, the lower threshold level may include some margin for hysteresis. If the condensate level is still above the threshold level, the routine at 426 includes resuming engine operation with the injection timing switched to the secondary timing, which provides lean stratified combustion with spark. In one example, operation of at least some cylinders in lean stratified mode may be continued for a few seconds to complete drainage.

[0082] If it is determined that the condensate level is below the (lower) threshold level, then routine 428 includes stopping the drainage of the condensate from the CAC to the engine intake. This involves reverting the fuel injection timing to the initial injection timing and resuming homogeneous combustion of the cylinder-air-fuel charge with spark ignition.

[0083] In Fig. 7. Routine 700 represents a procedure for determining the degree of leanness of the high-performance cylinders and adjusting the degree of richness of the low-performance cylinders accordingly. As such, the routine can be described as follows: Fig. 7 as part of the routine after Fig. 4 are executed, specifically at 422.

[0084] At 702, the strong cylinders, which exhibit lower water absorption sensitivity, can be identified. The data for the strong cylinders can be obtained, for example, from the in Fig. The reference table disclosed in Section 5 can be accessed. At 704, a (minimum) degree of leanness required to operate the high-power cylinders in lean stratified mode can be determined. Based on the cylinder's power, for example, a degree of leanness for a lean fuel injection can be determined. In one example, the controller can display a figure such as the Fig. after Fig. 8, is used to determine the required degree of leanness for the cylinder based on its "strength," with the required degree of leanness increasing as the "strength" of the strong cylinders increases. At 706, the determined degree of leanness is compared to a limit of the lean stratified mode. The determined degree of leanness can be compared, for example, to a lower lean threshold or a limit of operation in the lean stratified mode. If the determined degree of leanness is not within the limit (for example, it is richer than the limit), then routine 707 involves readjusting the determined degree of leanness so that it is at the limit of the lean stratified mode.After readjustment, or if the specified leanness level is already within the lean stratified mode limit, at 708, a richness level required to provide the target air-fuel ratio of the exhaust gases (e.g., overall at or around stoichiometry, or overall leaner than stoichiometry) is calculated based on the specified leanness level. Then, at 710, the required richness is distributed among the remaining "weak" cylinders, which are more susceptible to water absorption. The required richness can be distributed evenly, with each of the weak cylinders receiving fuel with the same richness level. Alternatively, the required richness can be distributed unevenly, with each of the weak cylinders receiving a fuel injection with a richness level based on its specific weakness. The controller can display a map, such as...B. the . Fig. after Fig. 8. Use to determine the degree of richness required for each weak cylinder based on its respective "weakness," with the degree of richness increasing as the "weakness" of the weak cylinders increases, and further based on the target richness to provide the overall target air-fuel ratio of the exhaust gases. Similarly, it can be used to determine the degree of richness required for each weak cylinder based on its respective "weakness," with the degree of richness increasing as the "weakness" of the weak cylinders increases, and further based on the target richness to provide the overall target air-fuel ratio of the exhaust gases. Fig. The additional spark can be mapped to the weakness of the weak cylinders, whereby the tendency of the cylinders to receive condensate can be used to estimate the spark advance required to restore combustion to the optimal phase position.

[0085] The engine could be, for example, a 4-cylinder in-line engine, which at the time of exhaust has one high-performance cylinder and three low-performance cylinders. Based on the high-performance cylinder's power output, a lean mixture of 1.3 lambda can be determined. As such, this value can fall within the limit of the lean stratified mode (of 1.5 lambda). Accordingly, to provide an overall stoichiometric exhaust gas (AFR = 1.0), the remaining low-performance cylinders can each receive an equal rich mixture of 0.9 lambda. Alternatively, the rich mixture can be unevenly distributed, with a first low-performance cylinder operating at 0.8 lambda, a second low-performance cylinder operating at 0.9 lambda, and a third low-performance cylinder operating at 1.0 lambda. In another example, based on the high-performance cylinder's power output, an AFR lean mixture of 16:1 can be determined.As such, this value can lie within a lean stratified mode limit (of an AFR of 17:1). In another example, depending on the combustion chamber design of the engine, a lean stratified limit of an AFR of ~30:1 can be applied because the compression injection near the spark plug is rich enough for combustion, while the overall air-fuel ratio remains very lean. Accordingly, to provide an overall stoichiometric exhaust (an AFR of 14:1), the remaining weak cylinders can each receive an equal richness of an AFR of 11:1. Alternatively, the richness can be unevenly distributed, with a first weak cylinder operating at an AFR of 10.5:1, a second weak cylinder operating at an AFR of 11.0:1, and a third weak cylinder operating at an AFR of 11.0:1.

[0086] In this way, the routine allows after Fig. 4 (and Fig. 7) Condensate removal with reduced combustion problems. By temporarily operating at least the cylinders with lower water absorption sensitivity in a lean stratified mode, the manifold airflow velocity can be increased sufficiently to blow the condensate out of the cylinders without causing misfires. By optionally adjusting the fuel injection timing of the cylinders most prone to misfire to run rich, combustion problems in these cylinders can be reduced during the removal process. Emission benefits can be achieved by maintaining the overall exhaust air-fuel ratio around stoichiometry.

[0087] In one example, a controller can drain the condensate from an intercooler while temporarily switching cylinder combustion to a lean stratified mode, with the degree of leanness based on the amount of condensate in the intercooler and the firing order of the cylinders during the draining process. This temporary switch to lean stratified combustion can involve switching combustion in (only) a first cylinder, which has a lower sensitivity to water absorption, to lean stratified mode.While combustion in the first cylinder is switched to lean stratified mode, combustion in a second cylinder, which is more sensitive to water absorption, can optionally be switched to rich mode and operated with a further advanced spark arrangement. This maintains an overall exhaust gas air-fuel ratio around stoichiometry, with the spark arrangement maintaining the optimal combustion rate. A degree of leanness can be set to provide engine airflow higher than a threshold level (e.g., a blow-off level), where the threshold level is based on the amount of condensate in the charge air cooler.The degree of leanness can further be based on a lean limit of the lean stratified mode, with the degree of leanness being adjusted so that it remains within the limit, and the degree of enrichment then being adjusted based on the degree of leanness to provide stoichiometric exhaust gas. The degree of leanness and / or the duration of operation in the lean stratified mode can be increased as the amount of condensate increases above a threshold quantity. The temporary switch to the lean stratified mode can also include the switch from a homogeneous mode, in which fuel is injected at least in one intake stroke, to the lean stratified mode, in which fuel is injected at least in one compression stroke.Furthermore, the controller can perform split fuel injection and increase the number of fuel injections per engine cycle based on the amount of condensate in the charge air cooler.

[0088] In another example, the power engine system comprises a power engine containing one or more cylinders, a compressor coupled upstream of an intake throttle valve, an intercooler coupled downstream of the compressor, a direct fuel injector for injecting fuel into a fuel cylinder, and a controller with computer-readable instructions. The computer may contain code to, while an accelerator pedal position is maintained, adjust the timing of the power engine's fuel injection in response to a condensate level in the intercooler exceeding a threshold, to operate one or more cylinders in a lean stratified mode until the condensate level falls below the threshold.The adjustment may involve operating cylinders with lower water absorption sensitivity in lean stratified mode, while cylinders with higher water absorption sensitivity are operated in stoichiometric mode, maintaining an overall air-fuel ratio of the exhaust gases lean for a period determined by the oxygen storage capacity of the catalyst, followed by a rich period of operation after the condensate has been consumed to return to oxygen storage equilibrium and efficiency in the catalyst.Furthermore, the adjustment can include operating the cylinders that have a lower sensitivity to water absorption in the lean stratified mode, while the cylinders that have a higher sensitivity to water absorption are operated in a rich mode, maintaining an overall air-fuel ratio of the exhaust gases around stoichiometry.

[0089] In Fig. 9 represents the Fig. This represents an exemplary operation for draining the condensate, where the fuel injection and the combustion-air-fuel ratios of the cylinders are individually adjusted based on their respective water absorption sensitivities. This approach allows for condensate drainage with a reduced incidence of cylinder misfires. Fig. Graphic 902 shows the condensate levels in the CAC, graphic 904 the position of the intake throttle valve, graphic 905-906 the changes in fuel injection, graphic 908 the overall air-fuel ratio of the exhaust gases (sampled near an exhaust aftertreatment device), graphic 910 the settings of the spark timing control, and graphic 912 the engine torque. Graphic 914 shows the output of a knock sensor, while graphic 916 shows the airflow of the intake manifold.

[0090] Before t1, condensate can accumulate in the charge air cooler during engine operation (see diagram 902). Before t1, the engine can operate with fuel injection into each cylinder, set to provide stoichiometric cylinder combustion (see block 905 with respect to the dashed line), and with spark timing control on the MBT (see diagram 910). The throttle opening (see diagram 904) and the fuel injection quantity can be adjusted to provide an engine airflow corresponding to a torque output (see diagram 912) that meets the driver's torque demand. Furthermore, before t1, the engine cannot knock.

[0091] At t1, the condensate levels can reach an upper threshold 901, triggering the drain conditions. At t1, in response to the increased condensate level, the cylinder fuel supply can be adjusted so that one or more engine cylinders run leaner than stoichiometry. In the example shown, three cylinders can run lean while one cylinder runs rich (see blocks 906 with respect to the dashed line). The controller can maintain fuel injection into the lean cylinders while increasing the engine airflow to the cylinders to provide the target lean mixture.In particular, the degree of leanness of the lean-running cylinders can be adjusted so that the level of the engine airflow (the MAP, graphic representation 916) is increased to or above a threshold level 917 at which the condensate can be drawn from the charge air cooler and discharged into the engine intake. The throttle valve opening can be increased to increase the engine airflow and provide the required degree of leanness. As such, the water absorption sensitivity of the cylinders may change.Therefore, the controller can advantageously select the high-performance cylinders, which exhibit lower sensitivity to water absorption, for lean operation (to provide the increased engine airflow), while selecting the remaining low-performance cylinders, which exhibit higher sensitivity to water absorption, for rich operation (to allow control of the air-fuel ratio). Furthermore, because the increased engine airflow can cause condensate to flow from the CAC into the engine, but unevenly to the engine cylinders (with some receiving more condensate than others), the uneven condensate flow can be compensated for by adjusting the cylinder fuel delivery based on the inherent variation in cylinder sensitivity to water absorption.

[0092] Specifically, the weaker cylinders (here, one cylinder), which have a higher sensitivity to water absorption, can be run rich, while the remaining strong cylinders (here, three cylinders), which have a lower sensitivity to water absorption, can be run lean. The degree of leanness of the strong cylinders can be adjusted based on the condensate level in the CAC to increase the level of engine airflow (the graphic 916) above the threshold 917. The degree of richness of the remaining cylinders is then adjusted based on the degree of leanness of the weaker cylinders to maintain an overall exhaust air-fuel ratio (overall AFR) at the stoichiometry (see the dashed line).In the example shown, the degree of leanness of the strong cylinders is set unevenly, with each cylinder being adjusted based on its strength; the stronger the cylinder, the higher the degree of tolerated leanness (see the three hatched blocks below the dashed stoichiometry line).

[0093] To maintain the engine's torque output while the cylinders are operating with different fuel mixtures, and to reduce the knocking frequency of the weaker cylinders that absorb condensate, the rich-running cylinders can also be operated with a spark timing advance pre-set by the MBT, as shown in diagram 910. Simultaneously, the lean-running cylinders can be operated with the nominal spark timing maintained, as shown in the dashed diagram 911. In alternative examples, the rich cylinders can have more spark advance, while the lean cylinders have less.

[0094] As such, engine operation with fuel supply according to 906 can continue for a number of engine cycles, during which the condensate level may begin to fall from the upper threshold 901. At t2, the condensate level may be at or below the lower threshold 903, indicating that the condensate has been sufficiently drained from the CAC. Furthermore, due to the consumption of condensate in the engine, the rich-running (weak) cylinders may begin to knock. As shown in graph 914, just before t2, the knock frequency of the rich cylinders may increase, and the output of a knock sensor coupled to the rich cylinders may frequently exceed a knock threshold 915. In response to the sudden increase in the knock frequency, the controller may infer that condensate consumption has been completed.Accordingly, at t2, the original settings of the engine airflow, fuel supply, and ignition timing control can be resumed. Specifically, the throttle valve opening can be reduced to a nominal position based on the engine's operating conditions. Furthermore, the spark timing control can be reset to the MBT. Finally, engine operation can be resumed with fuel supply according to 905 (stoichiometric cylinder combustion).

[0095] It is recognized that, while the above example actively increases the engine airflow in response to the condensate level without increasing the engine torque to allow for draining, in an alternative example the condensate can be drained opportunistically during a tip-in, while taking advantage of the increased engine airflow of the tip-in. In response to a tip-in occurring at (or shortly after) t1, the opening of the inlet throttle valve can be increased (Figure 904) to provide the engine airflow required to meet the increased torque demand. Furthermore, the spark timing control on the MBT can be maintained (see the dashed segment 911) so that the engine torque can be increased based on the driver demand (see the dashed segment 913).While the condensate is being drained opportunistically, fuel injection into the cylinders can be adjusted on a cylinder-by-cylinder basis (according to 906) so that combustion stability issues in each cylinder can be addressed when condensate is absorbed during draining. At t2, the engine airflow can be reduced in response to pedal release.

[0096] In this way, the condensate can be drained without impairing combustion in the engine cylinder, while reducing the frequency of misfires caused by the intake.

[0097] In Fig. 10 represents a Fig. This represents an exemplary operation for draining the condensate, where the timing of the fuel injection and the combustion mode of the cylinders are adjusted to provide an engine airflow that allows the condensate to be blown off without increasing the occurrence of cylinder misfires. Fig. Figure 1002 in the graphical representation shows the air-fuel ratio of the engine cylinders, with the air-fuel ratios on the right side of the y-axis representing an increasing degree of richness, while those on the left side of the y-axis represent an increasing degree of leanness. A range of leanness required for cylinder operation in a lean stratified mode is shown in Figure 1004 (the hatched block).

[0098] In the example shown, the engine is a four-cylinder in-line engine with three low-power cylinders (W1-W3) and one high-power cylinder (S1). In response to increased condensate levels, condensate drainage may be required. In this regard, it may be necessary to operate one or more engine cylinders in a lean stratified mode to provide the engine airflow required to blow off the condensate. In the example shown, the high-power cylinder S1, which has the lower sensitivity to water absorption, can be selected for operation in the lean stratified mode.

[0099] Based on the condensate level in the CAC (Coolant Accumulator), the leanness level for cylinder S1 is determined. This leanness level can fall within the limit of 1004 for the lean stratified mode and is therefore permissible. Consequently, cylinder S1 operates in lean stratified mode with the determined leanness level. Simultaneously, the weaker cylinders W1-3 operate in a rich mode with a richness level set based on the leanness of cylinder S1, ensuring that the overall air-fuel ratio of the exhaust gases remains within the stoichiometric range. Here, the richness level of cylinders W1-3 is adjusted based on their "weakness," with the less weaker cylinders W1 and W2 receiving less enrichment and the weaker cylinder W3 receiving more enrichment.By operating the S1 in lean stratified mode, the increased engine airflow can be used to expel condensate, while lean operation is employed in the cylinder that tolerates the most condensate intake, thus reducing the potential for misfires. Simultaneously, rich operation is used in the cylinders that do not tolerate condensate intake well, improving combustion stability in these cylinders and further reducing the potential for misfires.

[0100] As such, the degree of richness in the weaker cylinders can be adjusted within a range. If a weaker cylinder in particular is run too rich, this could lead to late combustion, which, upon the addition of condensate, could result in misfiring. Consequently, the weaker cylinders with the lowest water absorption are likely to run richest, with the weakest cylinder receiving the most condensate running least rich, possibly after the RBT (rich for best torque), while still maintaining the stoichiometric overall air-fuel ratio at the catalytic converter.

[0101] In an alternative example, it may be determined that the leanness level of the strong cylinders (here, S1', shown in dashed lines) lies outside the limit 1004 of the lean stratified mode. Specifically, the required leanness may be less than the minimum amount of lean needed to operate in the lean stratified mode (see S1' outside the hatched block 1004). In such a scenario, the leanness level of S1' is adjusted so that it lies within or on the limit of the lean stratified mode. As indicated by the arrow, the leanness level for S1' may, for example, be increased further than necessary, so that the leanness falls within the leanness required for operation in the lean stratified mode.To compensate for the added leanness, the richness level of one or more of the weaker engine cylinders can be increased. In the example shown, as indicated by the arrow, the richness level of W3 can be increased to compensate for the increase in the leanness of S1'.

[0102] In another example, in response to a condensate level in an intercooler, a controller can adjust the fuel injection of each engine cylinder based on each cylinder's water absorption sensitivity to increase engine airflow above a threshold level while maintaining an overall exhaust air-fuel ratio around stoichiometry. This adjustment can involve leaning out one or more engine cylinders with lower water absorption sensitivity by setting a degree of leanness to increase engine airflow above the threshold level, and enriching the remaining engine cylinders with higher water absorption sensitivity by setting a degree of richness based on the degree of leanness to maintain the exhaust air-fuel ratio around stoichiometry.The adjustment can be made in response to a condensate level in the charge air cooler exceeding a threshold value. The threshold value (the threshold airflow level) above which the engine airflow is increased can be based on the difference between the condensate level in the charge air cooler and the threshold value. Consequently, as the condensate level in the charge air cooler increases, the lean-running cylinders can be lean-running more strongly to further increase the engine airflow level. The rich-running cylinders can then be rich-running correspondingly to maintain a stoichiometric overall air-fuel ratio in the exhaust gases.

[0103] In this way, condensate can be periodically removed from an intercooler by blowing it off to the engine cylinders. Adjusting the fuel supply to each cylinder during condensate drainage and the spark advance for the cylinders receiving the majority of the condensate, based on each cylinder's sensitivity to water absorption and / or the amount of condensate absorbed, can compensate for variations in cylinder combustion stability and the occurrence of misfires. By running the cylinders more susceptible to condensate-induced combustion problems richer than stoichiometric, the combustion stability of these cylinders during drainage is improved.By operating the other cylinders, which are less susceptible to combustion problems caused by condensate, at a leaner than stoichiometric mixture, an overall stoichiometric environment can be provided in the exhaust gas, improving engine performance and reducing emissions. Adjusting the fuel injection timing so that at least one or more high-performance cylinders operate in a lean stratified mode allows for a sufficiently increased level of engine airflow to initiate condensate drainage. Using a stratified injection mode that maintains a rich environment near a cylinder's spark plug improves combustion stability. This enables the complete drainage of condensate while reducing combustion problems associated with condensate absorption.

[0104] It is stated that the exemplary control and estimation routines contained herein can be used with various configurations of the power engine and / or vehicle system. The specific routines described here may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, the various actions, operations, and / or functions illustrated may be performed in the illustrated order, performed in parallel, or, in some cases, omitted. Likewise, the order of processing is not necessarily required to achieve the features and benefits of the example execution methods described here, but it is provided for ease of illustration and description.One or more of the illustrated actions, operations, and / or functions can be performed repeatedly, depending on the specific strategy used. 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 power-machine control system.

[0105] It is clear that the configurations and routines disclosed herein are exemplary and that these specific embodiments are not to be considered limiting, as numerous variations are possible. The above technique can be applied, for example, to V-6, 1-4, 1-6, V-12, Boxer-4, and other types of power engines. The subject matter of this 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.

[0106] The following claims specifically describe certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or its equivalent. Such claims should be understood as including one or more such elements and neither requiring nor excluding two or more such elements. Further combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application.Such claims, whether their scope is broader than, narrower than, equal to, or different from the scope of the original claims, are also considered to be included in the subject matter of the present disclosure.

Claims

[1] Power engine process comprising the following: in response to a condensate level in an intercooler (80, 166), adjusting the timing of the fuel injection while the engine airflow is increased to a level greater than requested by a vehicle operator (132), wherein adjusting the timing of the fuel injection includes switching from a first injection timing control providing a homogeneous cylinder-air-fuel charge ignited by a spark to a second injection timing control providing a stratified cylinder-air-fuel charge ignited by a spark. [2] Power engine method according to claim 1, wherein the first injection timing control comprises an intake stroke injection and wherein the second injection timing control comprises a compression stroke injection. [3] Engine method according to claim 2, wherein the intake stroke injection comprises an early intake stroke injection or a mid-intake stroke injection or a late intake stroke injection and wherein the compression stroke injection comprises a late compression stroke injection. [4] Power engine method according to claim 3, wherein adjusting the timing of the fuel injection further comprises adjusting a number of fuel injections per combustion event. [5] Engine method according to claim 4, wherein adjusting the number of fuel injections comprises switching from a single intake stroke fuel injection to a split fuel injection comprising at least one compression stroke injection. [6] Engine method according to claim 1, wherein adjusting the timing of the fuel injection comprises increasing the number of fuel injections per engine cycle when the condensate level exceeds a threshold (901) and increasing the ratio of fuel supplied in a compression stroke to an intake stroke. [7] Power engine method according to claim 1, wherein the increased power engine airflow level is based on the condensate level in the charge air cooler (80, 166). [8] Power engine method according to claim 1, comprising in response to a condensate level in the charge air cooler (80, 166) in response to the fact that the condensate level is greater than a threshold level (901). [9] Power engine method according to claim 1, wherein the adjustment to increase the power engine airflow level comprises adjusting to increase the power engine airflow level to a blow-off level required to empty condensate from the charge air cooler (80, 166). [10] Power machine method comprising the following: Draining condensate from an intercooler (80, 166) while cylinder combustion is temporarily switched to a lean stratified mode, wherein a degree of leanness is based on a quantity of condensate in the intercooler (80, 166) and a firing order of the cylinders (30) during the draining, wherein the temporary switch to the lean stratified mode comprises switching from a homogeneous mode in which the fuel is injected at least in one intake stroke to the lean stratified mode in which the fuel is injected at least in one compression stroke. [11] Power engine method according to claim 10, wherein temporarily switching the cylinder combustion to a lean stratified mode comprises switching the combustion in a first cylinder which has a lower sensitivity to water absorption to the lean stratified mode. [12] Engine method according to claim 11, further comprising, while the combustion in the first cylinder is switched to the lean stratified mode, switching the combustion in a second cylinder, which has a higher sensitivity to water absorption, to a rich mode, so that an overall air-fuel ratio of the exhaust gas is maintained around stoichiometry. [13] Engine method according to claim 12, wherein the degree of leaning can be adjusted to provide an engine airflow that is higher than a threshold level (901), wherein the threshold level (901) is based on the amount of condensate in the charge air cooler (80, 166). [14] Power engine method according to claim 13, wherein the degree of leaning is further based on a leanness limit of the lean stratified mode, wherein the degree of leaning is adjusted to be within the limit, and wherein the degree of enrichment is adjusted based on the degree of leaning to provide a stoichiometric exhaust gas. [15] Power engine method according to claim 11, wherein the degree of leaning and / or the duration of operation in the lean stratified mode increases with an increase in the amount of condensate above a threshold amount. [16] Engine method according to claim 13, wherein the temporary switch to the lean stratified mode further comprises performing split fuel injection and increasing a number of fuel injections per engine cycle based on the amount of condensate at the charge air cooler (80, 166). [17] Power engine system comprising the following: a power engine (10) containing one or more cylinders (30); a compressor (162) coupled upstream of an inlet throttle valve (21); an intercooler (80, 166) coupled downstream of the compressor (162); a direct fuel injection nozzle (66) for injecting fuel into an engine cylinder (30); and a controller (12) with computer-readable instructions for: while an accelerator pedal position is maintained, in response to a condensate level at the charge air cooler (80, 166) that is higher than a threshold (901), Adjusting the timing control of the fuel injection of the engine (10) to operate one or more cylinders (30) in a lean stratified mode until the condensate level is below the threshold (901). [18] Power engine system according to claim 17, wherein the setting comprises operating the cylinders (30) that have a lower sensitivity to water absorption in the lean stratified mode, while the cylinders (30) that have a higher sensitivity to water absorption are operated in a stoichiometric mode, wherein an overall air-fuel ratio of the exhaust gas is kept lean, or operating the cylinders (30) that have a lower sensitivity to water absorption in the lean stratified mode, while the cylinders (30) that have a higher sensitivity to water absorption are operated in a rich mode, wherein an overall air-fuel ratio of the exhaust gas is kept around stoichiometry.

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