Method and system for charge air cooler condensate control

Methods and systems are provided for controlling a condensate level in a charge air cooler. In one example, a method may include adjusting an air flow to a membrane in response to a condensate level in the charge air cooler.

FIELD

The present description relates generally to methods and systems for controlling a vehicle engine condensate level in a charge air cooler.

Turbocharged and supercharged engines may be configured to compress ambient air entering the engine in order to increase power. Because compression of the air may cause an increase in temperature of the air, a charge air cooler may be utilized to cool the heated air thereby increasing its density and further increasing the potential power of the engine. If the humidity of the ambient air is high and or the engine is equipped with exhaust gas recirculation (EGR), however, condensation (e.g., water droplets) may form on any internal surface of the charge air cooler that is cooler than the dew point of the compressed air. During conditions such as a hard vehicle acceleration, these water droplets may be blown out of the charge air cooler and into the combustion chambers of the engine resulting in engine misfire, loss of torque and engine speed, and incompletely burned fuel, for example.

One approach for reducing the amount of condensation entering the combustion chambers is disclosed in US Patent Application Publication 2008/0190079. In the cited reference, a liquid trap for collecting condensation is placed in fluid communication with an air intake conduit downstream of the air cooler. The liquid trap may be coupled to a collection tank having a liquid level sensor which stores the collected condensation. The sensor may indicate when the water level becomes high and the collection tank needs to be emptied. Such a system may require a drain valve which may eventually stick closed or stick open causing a loss of boost pressure and subsequent loss of power to the engine. Such a system may also require the collection tank to be drained to the surroundings exterior to the vehicle. The condensation may contain regulated emissions, however, and draining the tank to the vehicle surroundings may not be an available option.

In one example, the issues described above may be addressed by a method comprising adjusting a drying air flow directed to a membrane in a charge air cooler in response to a condensate level in the charge air cooler. In this way, a charge air cooler condensate level may be maintained by applying a drying air flow to a membrane configured to selectively remove water. As one example, a drying air flow to a membrane may be increased in order to reduce a charge air cooler condensate level in order to prevent an engine cylinder misfire.

DETAILED DESCRIPTION

The following figures represent a method and system for flowing a compressed gas mixture over a membrane positioned in a charge air cooler. The compressed gas mixture may deposit water (vapor or liquid) onto an inner portion of the membrane and the water may diffuse from the inner portion of the membrane to an outer portion of the membrane. A drying air flow may be directed to the outer portion of the membrane to draw water from the membrane to ambient air surrounding the charge air cooler.

The drying air flow may be provided by an air flow device. The air flow device may be adjusted in order to maintain a condensate level within the charge air cooler below a threshold level. As one example, the condensate level within the charge air cooler may be reduced in response to a decreasing engine combustion stability limit (e.g., decreasing likelihood of an engine misfire) by increasing the drying air flow rate. Methods and systems for controlling a charge air cooler condensate level are described below.

FIG. 1shows an example of an engine system, for example, an engine system generally at10. The engine system10may be a diesel engine, or a gasoline engine, or other type of engine that may utilize various components in accordance with the present disclosure. Specifically, internal combustion engine10comprises a plurality of cylinders11. Engine10is controlled by electronic engine controller12. Engine10includes a combustion chamber and cylinder walls with a piston positioned therein and connected to crankshaft20. The combustion chamber communicates with an intake manifold22and an exhaust manifold24via respective intake and exhaust valves.

Charge motion control device (CMCD)80may be located upstream of the intake manifold22. The CMCD80may restrict airflow to one or more of cylinders11for a variety of desired results, including but not limited to adjusting turbulence and burn rate. In the example ofFIG. 1, each CMCD80may include a valve plate with a cut-out section. Other designs of the valve plate are possible. Note that for the purposes of this disclosure the CMCD is in the “closed” position when it is fully activated and the valve plate may be fully tilted into the respective conduit of intake manifold190, thereby resulting in maximum air charge flow obstruction. Alternatively, the CMCD may be in the “open” position when deactivated and the valve plate may be fully rotated to lie substantially parallel with airflow (as depicted inFIG. 1), thereby considerably minimizing or eliminating airflow charge obstruction. The CMCD may principally be maintained in their “open” position and may only be activated “closed” when swirl conditions are desired. Each CMCD80may be adjusted via a rotating shaft to rotate the valve plate so that the valve plate is parallel to the flow direction when in the “open” position.

Intake manifold22communicates with throttle body30via throttle plate32. In one embodiment, an electronically controlled throttle can be used. In some embodiments, the throttle is electronically controlled and adjustable to periodically, or continuously, maintain a specified vacuum level in intake manifold22. While throttle body30is depicted as being downstream of a compressor device90b, it will be appreciated that the throttle body may be placed upstream or downstream of the compressor. The choice may depend partly on the specific EGR system or systems that is/are used. Alternatively, or additionally, a throttle body30may be placed in the air induction tube upstream of the compressor or in the exhaust line to raise exhaust pressure. This may be effective in helping to drive EGR, but may not be effective by increasing total system cost and increasing the pumping work of the engine.

The combustion chamber is also shown having fuel injectors34coupled thereto for delivering fuel in proportion to the pulse width of signal (fpw) from controller12. Fuel is delivered to the fuel injectors34by a conventional fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown). In the case of direct injection engines, as shown inFIG. 1, a high pressure fuel system is used such as a common rail system. However, there are several other fuel systems that could be used as well, including but not limited to EUI, HEUI, etc. Additionally or alternatively, fuel may be injected in the intake ports of the cylinders.

In the depicted embodiment, controller12is a conventional microcomputer, and includes a microprocessor unit40, input/output ports42, electronic memory44, which may be an electronically programmable memory in this particular example, random access memory46, keep alive memory48, and a conventional data bus.

Controller12may be configured to receive various signals from sensors coupled to engine10, which may include but may not be limited to: measurements of inducted mass airflow (MAF) from mass airflow sensor50; engine coolant temperature (ECT) from temperature sensor52; manifold pressure (MAP) from manifold pressure sensor56coupled to intake manifold22; a measurement of throttle position (TP) from a throttle position sensor (not shown) coupled to throttle plate32; and a profile ignition pickup signal (PIP) from Hall effect sensor60coupled to crankshaft20indicating engine speed. In some examples, the controller12may adjust one or more of high pressure EGR valve72, low pressure EGR valve155, throttle21, compressor recirculation valve27, and/or wastegate26to achieve a desired EGR dilution percentage of the intake air.

Engine10may include an exhaust gas recirculation (EGR) system to help lower NOx and other emissions. For example, engine10may include a high pressure EGR system in which exhaust gas is delivered to intake manifold22by a high pressure EGR passage70communicating with exhaust manifold24at a location upstream of an exhaust turbine90aof a compression device90, and communicating with intake manifold22at a location downstream of an intake compressor90bof the compression device90. A high pressure EGR valve assembly72may be located in high pressure EGR passage70. Exhaust gas may then travel from exhaust manifold24first through high pressure EGR passage70, and then to intake manifold22. The amount of EGR provided to the intake passage190, upstream of throttle body30and downstream of charge air cooler120, may be varied by the controller12via an EGR valve, such as high pressure EGR valve72. An EGR cooler (not shown) may be included in high pressure EGR tube70to cool re-circulated exhaust gases before entering the intake manifold. Cooling may be done using engine coolant, but an air-to-exhaust gas heat exchanger may also be used.

FIG. 1also shows a low pressure EGR system where EGR is routed from downstream of a turbine of a turbocharger to upstream of a compressor of a turbocharger through low pressure EGR passage157. A low pressure EGR valve155may control the amount of EGR provided to the intake passage190. In some embodiments, the engine may include both a high pressure EGR and a low pressure EGR system, as shown inFIG. 1. In other embodiments, the engine may include either a low pressure EGR system or a high pressure EGR system. When operable, the EGR system may increase the formation of condensate as it increases the water vapor concentration in the charge air, particularly when the charge air is cooled by the charge air cooler, as described in more detail below.

Further, drive pedal94is shown along with a driver's foot95. Pedal position sensor (pps)96measures the angular position of the driver actuated pedal. Further, engine10may also include exhaust air/fuel ratio sensors (not shown). For example, either a 2-state EGO sensor or a linear UEGO sensor can be used. Either of these may be placed in the exhaust manifold24, or downstream of the compression device90.

Compression device90may be a turbocharger or any other such device. The depicted compression device90may have a turbine90acoupled with the exhaust manifold24and a compressor90bcoupled with the intake manifold22via an intercooler120which may be an air-to-air heat exchanger, but could also be water cooled. Turbine90ais typically coupled to compressor90bvia a drive shaft92. The speed of turbine90amay controlled via wastegate26. A sequential turbocharger arrangement, single VGT, twin VGTs, or any other arrangement of turbochargers could be used and could include coolers within the compression device system, such as between two stages of compression.

An intake passage190may include an air intake control valve21. Additionally, the intake passage190may include a compressor bypass or recirculation valve (CRV)27configured to divert intake air around the compressor90b. The wastegate26and/or the CRV27may be controlled by the controller12to be opened when a lower boost pressure is desired, for example. For example, in response to compressor surge or a potential compressor surge event, the controller12may open the CRV27to decrease pressure at the outlet of the compressor90b. This may reduce or stop compressor surge. Additionally or alternatively, the CRV27and/or the wastegate26may be opened to decrease a pressure in the charge air cooler and as a result, reduce condensate formation in the charge air cooler. The effect of pressure on condensation will be discussed in further detail below.

Further, the intake passage190may include a charge air cooler120(e.g., an intercooler) fluidically coupled to the compressor90band the engine10. The compressor may be upstream of the charge air cooler to provide a compressed gas mixture to the charge air cooler. The charge air cooler may be used to decrease the temperature of the turbocharged or supercharged compressed gas mixture. The charge air cooler120may be an air-to-air cooler or a liquid-to-air cooler.

As explained above, condensate may accumulate in the charge air cooler and be swept to the engine, where it can cause combustion instability. As will be described in more detail below, the charge air cooler may include a membrane100to selectively transfer water vapor and/or condensate within the charge air cooler to outside of the charge air cooler without allowing charge air to leak from the charge air cooler.

The membrane100may be used to control condensate levels in the charge air cooler via capillary pores of varying diameter. The membrane may comprise an inner portion and an outer portion, wherein the inner portion comprises smaller capillary pores interacting with a compressed gas mixture and the outer portion, and the outer portion comprises larger capillary pores interacting with a drying air flow and the inner portion. The membrane100may have a relatively high water permeability, and be unaffected by compounds such as acids and particulates, as disclosed by U.S. Pat. No. 8,511,072. The membrane100may be constructed from stainless steel, alumina, and/or other corrosion resistant material.

The membrane100may be dried via a drying air flow shown by an incoming flow122and an outgoing flow124. As a result, the drying air flow may dry the outer portion of membrane100through an evaporative action. The drying air flow may be provided to the charge air cooler via an air movement device in some examples. An air movement device may comprise one or more of a fan, an air pump, and an air duct positioned to direct ram air to the outer portion of the membrane. In some embodiments, the air duct may include a flow control valve. Additionally or alternatively, the fan and the air duct may exist together simultaneously, wherein they may be operated concurrently or sequentially.

Additionally or alternatively, the membrane100may be located in a low pressure EGR loop, in the pre-charge air cooler duct work, in the charge air cooler inlet tank, and/or other suitable location. In some examples, the membrane may be located in the charge air cooler replacing one or more heat exchanger finned cooling tubes included within the charge air cooler.

Thus, the system ofFIG. 1illustrates a charge air cooler configured to cool a compressed gas mixture in the charge air cooler. The charge air cooler includes a membrane over which the compressed gas mixture passes, depositing water vapor on an inner surface of the membrane. A drying air flow passes over an outer surface of the membrane and evaporates water from the membrane, without mixing with the compressed gas mixture.

FIG. 2includes system200illustrating a charge air cooler including one or more membranes, such as membrane100, to manage condensate formation. The charge air cooler120may be used to cool compressed gas flowing downstream of a compressor (e.g., compressor90b). Condensate may form in the charge air cooler120if a dew point within the cooler120is below a dew point of the compressed gas mixture. The membrane100may be used to separate water from the compressed gas mixture without permitting the compressed gas to escape through the membrane.

The compressed gas mixture210(e.g., including one or more of O2, CO2, N2, EGR, etc.), represented by dashed lines as it flows through the charge air cooler, may travel through a mixed gas stream passageway212(which may be the intake passage190ofFIG. 1in one example). The mixed gas stream pathway flows into a charge air cooler inlet tank214, wherein the compressed gas mixture is able to spread across the length of the charge air cooler inlet tank which may be equal to the length of the charge air cooler120. As depicted, the mixed gas stream passageway may divide into a plurality of passageways in the charge air cooler120. One or more membranes (e.g., membrane100) may be positioned within the charge air cooler to collect fluid (e.g., water) from the compressed gas mixture. In one example, a plurality of membranes may be interspersed along the mixed gas stream passageway212. In another example, shown inFIG. 2, one or more of the cooling tubes215of the charge air cooler may be comprised of the membrane100. In a further example, the membrane may be located in the charge air cooler inlet tank or other suitable location.

The compressed gas mixture flows through the charge air cooler120and passes over membrane(s)100. An inner portion of membrane100absorbs water from the compressed gas mixture without absorbing the compressed gas mixture and an outer portion of membrane100expels the water to ambient, which may be expedited via a drying air flow provided by an air movement device220. Water diffuses from the inner portion of the membrane to the outer portion of the membrane. The drying air flow and the compressed gas mixture do not mix, as membrane100maintains the ambient air outside the charge air cooler and the compressed gas mixture inside the charge air cooler separately. The air movement device220directs the drying air towards the charge air cooler. The drying air removes water from the outer surface of the membrane100, without mixing with the compressed gas mixture.

Water diffusing from the outer portion of the membrane to the drying air may be based on two mechanisms. One mechanism is the diffusion of water from an area of higher concentration (e.g., the saturated membrane) to an area of lower concentration (e.g., the drying air flow). As the membrane becomes increasingly saturated with water, it is more likely to transfer the water to the drying air. The second mechanism is through pressure. A pressure within the charge air cooler is relatively high, and thus is typically higher than the pressure of the drying air flow. Therefore, the high pressure water in the membrane may be kinetically favored to diffuse to the low pressure drying air flow. The high pressure compressed gas mixture does not flow through the membrane and into the low pressure drying air due to the structure of the membrane, described in further detail below.

A drier compressed gas mixture may exit through an outlet tank216, into the mixed gas stream passageway212, and flow into the engine intake22(not shown). The drier compressed gas mixture comprises less water than the compressed gas mixture at the inlet of the charge air cooler, particularly when the drying air flow is directed towards the charge air cooler membranes.FIG. 2is an illustration of a charge air cooler comprising a membrane that may manage condensate levels in the charge air cooler according to engine operating parameters.FIGS. 3A-Dfurther illustrate the structure of the membrane along with the drying air flow source, placement, and mode of action.

FIGS. 3A-Dillustrate various air movement devices or air duct locations providing a drying air flow to the charge air cooler.FIG. 3Dfurther illustrates the structure of the membrane. As mentioned above, an alternative embodiment may exist where the drying air flow may be provided by both the air movement device and the air duct. Further, embodiments may exist where the drying air flow may only be provided by the air movement device or the air duct.

FIGS. 3A and 3Billustrate respective systems300aand300b. Systems300aand300bdepict an air movement device305(e.g., a fan or an air pump) positioned to direct drying air flow parallel and angled to a membrane, respectively. The membrane may be positioned in a charge air cooler (e.g., charge air cooler120), or other suitable location.FIG. 3Cshows system300cillustrating an air duct310directing a drying air via a bend320. The drying air flow through the air duct may be provided by ambient air (e.g., ram air). Additionally or alternatively, the air duct may include a control valve to control the drying air flow to the charge air cooler. As mentioned above, the air movement device305may be electrically operated. Further, the air movement device may be configured to adjust the angle at which the drying air flow impinges on the membrane, such as by adjusting the angle of the fan blades. Membrane100collects water from a compressed gas mixture as it flows through a mixed gas stream passageway212. As the drying air flow is blown over the membrane, water molecules, represented by relatively large circles320, diffuse from the membrane in the mixed gas stream pathway212to the drying air flow.

FIG. 3Drepresents a detailed view of the structure of membrane100. Arrows depict the flow of water through the membrane and into the drying air flow (not shown). As a result, the compressed gas mixture may be to the left of the membrane and the drying air flow may be to the right of the membrane with respect toFIG. 3D. As the compressed gas mixture flows through a mixed gas stream passageway, water is absorbed onto the smaller capillary pores350of the membrane100. The smaller capillary pores350of the membrane prevent the compressed gas mixture from flowing through the membrane. Water captured by the membrane moves toward the larger capillary pores360on the outer surface of the membrane. The smaller capillary pores350may have a diameter between 3 nm to 10 nm and the larger capillary pores360may have a diameter between 11 nm to 100 nm. Additionally or alternatively, the larger capillary pores360may have a diameter of 3 nm to 10 nm, however, the larger capillary pores360remain larger in diameter when compared to the smaller capillary pores350. As the drying air flow passes over the membrane, the outer surface of the membrane is dried, therein enabling water to move from the inner surface to the outer surface. This action permits the inner surface of the membrane to further absorb water from the compressed gas mixture. The drying air flow need not be unidirectional to the movement of water in the membrane, but instead may be perpendicular, opposing, or a combination thereof (e.g., angled) to the direction of water movement in the membrane. Additionally or alternatively, the membrane may comprise of a material capable of selectively absorbing water and preventing a gas from flowing through the material. The water diffuses through the material to the outer surface (e.g., dry side) and evaporates upon interacting with a drying air flow.

Thus, the membrane described above with respect toFIGS. 1-3Dprovides a mechanism to manage condensate levels in an engine component, such as a charge air cooler. In some examples, the condensate in the charge air cooler may be managed according to a combustion stability limit of an engine fluidically coupled to the charge air cooler. The combustion stability limit may represent the level of water vapor and/or condensate within the charge air inducted into the cylinders that the engine may tolerate without experiencing degraded combustion. The combustion stability limit may be exceeded if a condensate level in the charge air cooler is greater than a threshold condensation level and the condensate is swept into the engine, where it over-dilutes the combustion mixture in the cylinders.FIG. 4describes a method for managing a level of condensate within the charge air cooler based on the combustion stability limit.

FIG. 4is a flow chart illustrating an example method400for controlling a condensate level in a charge air cooler. During certain instances, the method may include adjusting a drying air flow to a charge air cooler membrane in order to maintain a condensate level according to a combustion stability limit.

Method400will be described herein with reference to components and systems depicted inFIGS. 1-2, particularly, regarding charge air cooler120, membrane(s)100, engine10, air movement device220, and compressor90b. Method400may be carried out by a controller (e.g., controller12) according to computer-readable media stored thereon. It should be understood that the method400may be applied to other systems of a different configuration without departing from the scope of this disclosure.

Method400may begin at402, wherein engine operating conditions may be estimated and/or measured. The engine operating conditions may include, but are not limited to an engine speed, an engine load, an engine temperature, an EGR temperature and mass flow, a dilution demand, an air intake temperature and humidity, charge air cooler temperature, and a commanded air/fuel ratio. The dilution demand may be based on the current engine operating parameters (e.g., engine speed and/or engine load). The dilution demand may be additionally or alternatively determined based on a variety of factors, including but not limited to NOxformation, engine temperature, and air/fuel ratio. The engine dilution demand may also be determined by an optimal fuel economy for the engine.

At404, a condensate level in the charge air cooler may be estimated based on air humidity, air temperature, EGR rate, EGR temperature, air/fuel ratio and/or a pressure in the charge air cooler. Condensate may form in the charge air cooler when a temperature of the charge air cooler is below a dew point temperature of a gas mixture flowing through the charge air cooler. Physical traits affecting the dew point of the gas mixture may include humidity, EGR rate and water vapor content, and pressure of the gas mixture. As the total water vapor concentration, and/or pressure increase, the dew point of the gas mixture increases, thereby increasing the likelihood of condensate formation in the charge air cooler. Determining the air humidity may include determining the air humidity based on signals from a humidity sensor located upstream of the charge air cooler in an air intake passage (e.g., intake passage190). Likewise, determining the EGR water vapor content may include determining the EGR water vapor content based on signals determining the EGR rate and engine air-fuel ratio.

At406, the method400includes determining if the estimated condensate formation in the charge air cooler is greater than a threshold condensate level. The threshold condensate level may be based on a combustion stability limit. As explained above, the combustion stability limit represents how much dilution (e.g., water vapor and/or condensate) may be ingested by the engine before knock, misfire, or other unstable combustion events occur. The combustion stability limit may be based on current operating parameters, including engine speed and load, EGR rate, and spark timing. Further, the combustion stability limit may be based on one or more of a degraded combustion and/or misfire potential for the current operating conditions. The threshold estimated condensate level may be correlated with the combustion stability limit, as the amount of condensate the engine is able to tolerate increases as the combustion stability limit increases. If the estimated condensate is greater than the threshold condensate level, then method400proceeds to408to maintain current engine operating parameters. The method may exit.

In some embodiments, the threshold condensate level may be adjusted proportionally to the combustion stability limit, wherein as the combustion stability limit increases, the threshold condensate level increases. The combustion stability limit may vary based on an engine dilution demand being satisfied. As the engine dilution demand is increasingly satisfied, the combustion stability limit may decrease.

Returning to406, if it is determined that the estimated condensate formation in the charge air cooler is greater than the threshold condensate level, then the method proceeds to410activate or adjust an air movement device. As explained above, the air movement device may include a fan and/or an air pump. When the estimated condensate formation in the charge air cooler exceeds the threshold, the fan or air pump may be activated to direct a drying air flow to the one or more membranes of the charge air cooler. In some examples, if the fan or air pump is already activated, the far or air pump may be adjusted based on the estimated condensate formation. The air movement device adjustment may be based on a model or measurement. The model may include increasing a drying air flow from the air movement device to a maximum amount for a predetermined duration of time (e.g., setting a fan to 2000 rpm for 5 minutes). The measurement may include adjusting a drying air flow from the air movement device and a duration of operation based on the estimated condensate level in the charge air cooler, wherein as the estimated condensate level in the charge air cooler increases, the drying air flow from the air movement device and the duration of operation also increase. Upon initiating and/or adjusting the air movement device, the method400proceeds to412determine if a second estimated condensate level is greater than the threshold condensate level.

The second estimated condensate level may be estimated similar to examples discussed above. Additionally or alternatively, the second estimated condensate level may account for the adjustment in drying air flow from the initiated/adjusted air movement device. A drying amount between the drying air flow and the membrane(s) may be measured by a mass over time (e.g., kg/hr). The drying rate may be based on the drying air flow provided by the air movement device and the condensate level in the charge air cooler. Therefore, the second estimated condensate level may equal a difference between an estimated condensate forming in the charge air cooler and the rate of drying between the drying air flow and the membrane(s). For example, if an estimated condensate forming in a charge air cooler is 2 kg/hr and a rate of drying between a drying air flow and a membrane is 1.8 kg/hr, then the second estimated condensate level is 0.2 kg/hr.

If the second estimated condensate level is not greater than the threshold condensate level, then the method proceeds to414maintain or disable/adjust the air movement device. Maintaining the air movement device may be based on the drying rate between the drying air flow and the membrane(s) being a desired drying rate, wherein the desired drying rate may provide sufficient drying to reduce the condensate level in the charge air cooler to below the threshold condensate level. The air movement device may be disabled based on the condensate level in the charge air cooler being less than a lower threshold condensate level (e.g., lower than the threshold condensate level), which may be no estimated condensate in some examples.

Returning to412, if the second estimated condensate level is greater than the threshold condensate level then the method may proceed to416adjust engine operating parameters, wherein the adjusting may include advancing the intake camshaft, increasing charge motion, adjusting spark, or disabling/reducing EGR. The controller may determine that a maximum drying rate between the drying air flow and the membrane(s) is not sufficient to reduce the condensate level in the charge air cooler to below the threshold condensate level. In other words, the rate of newly forming condensate is too high for the maximum drying rate to reduce to a condensate level below the threshold condensate level. As a result, the controller may adjust engine operating parameters including one or more of advancing the intake camshaft, increasing charge motion, adjusting spark, and reducing or disabling EGR (e.g., the EGR valves are moved to a partially or fully closed position). EGR and water vapor strongly affect flame speed and knocking Increased water content in a combustion mixture slows the flame speed and reduces knocking tendency. As a result, the controller may advance the intake camshaft, increase charge motion, and/or adjust spark in anticipation of condensate being blown to the engine to prevent engine knock and misfire. As an example, spark timing may be advanced proportionally to an amount of condensate, wherein as the amount of condensate increase, the spark timing advancement increases. Further, the controller may disable or reduce EGR to reduce condensate formation in the charge air cooler and/or decrease dilution of the charge air. Additionally or alternatively, advancing the intake camshaft, increasing charge motion, adjusting spark, and disabling or reducing EGR may be performed simultaneously. Further, the engine adjustments may include an ignition system adding re-strikes to reduce the possibility of misfire. The method may exit.

The method described above with respect toFIG. 4provides a method for selectively routing a drying air flow to a charge air cooler membrane(s). Routing the drying air flow to the charge air cooler membrane(s) comprises initiating/adjusting an air movement device. The air movement device may be initiated/adjusted based on a condensate level in the charge air cooler. If an estimated condensate level with the charge air cooler exceeds a threshold condensate level, then a drying air flow supplied from the air movement device may be increased.

The method also provides for adjusting engine operating parameters when a maximum drying rate between the drying air flow and the membrane(s) does not reduce the condensate level in the charge air cooler to a level below the threshold condensate level. The adjusting may include advancing the intake cam, increasing charge motion, adjusting spark, reducing/disabling EGR, or a combination thereof.

Now turning toFIG. 5, plot500illustrates a variety of engine conditions and their effects on one another as engine operating conditions change. The x-axis represents time and the y-axis represents the respective engine condition being measured. Graph502represents a charge air cooler condensate with lines504and506respectively representing a threshold condensate level and a lower threshold condensate level, graph508represents a drying air flow, graph510represents an EGR flow rate, and graph512represents a charge motion, for example.

Plot500will be described herein with reference to components and systems depicted inFIG. 1, particularly, membrane100, charge air cooler120, and engine10. Plot500may be measured by a controller (e.g., controller12) according to computer-readable media stored thereon.

Prior to T1, the charge air cooler condensate increases as the EGR flow rate increases, as shown by graphs502and510respectively. Charge motion control device is at a commanded position for the operating conditions, such as maximum opening for lowest pumping and the drying air flow remains disabled, as shown by graphs512and508respectively. At T1, the condensate level in the charge air cooler exceeds the threshold condensate level. Accordingly, the air movement device is initiated (e.g., a fan is turned on) and a drying air flow is directed towards the charge air cooler membrane(s). Charge motion control device remains open and the EGR flow rate continues to increase.

After T1and prior to T2, the drying air flow is relatively high and is able to reduce the charge air cooler condensate level to an amount below the threshold condensate level despite the increasing EGR flow rate. As the drying air flow begins to decrease, the condensate level approaches the lower threshold condensate level and the drying air flow decreases (e.g. a fan speed decreases). The lower threshold condensate level may represent an amount of condensate that the engine is able to ingest under current operating conditions without causing combustion instability, and as such the controller may signal to disable or adjust the drying air flow when the lower threshold condensate level is reached. The EGR flow rate continues to fluctuate. The charge motion control device remains open due to the air movement device reducing the charge air cooler condensate level to a level below the threshold condensate level independent of an engine operating parameter adjustment.

At T2, the air movement device is disabled. In some examples, the air movement device may be maintained or adjusted, as described above. The charge air cooler condensate level has decreased below the lower threshold condensate level. The EGR flow rate begins to increase. The EGR flow rate may begin to increase due to an increase in engine load. Charge motion control device remains open. After T2and prior to T3, the charge air cooler condensate level increases, possibly due to the increase in the EGR flow rate. Spark timing remains open and the drying air flow is disabled.

At T3, the charge air cooler condensate level exceeds the threshold condensate level and as a result, the air movement device supplies a drying air flow. After T3and prior to T4, the charge motion control device is activated (e.g., charge motion control device80is closed) in response to a rate of drying between the maximum drying air flow and the membrane(s) not drying the condensate level to a level below the threshold condensate level. Additionally, the EGR flow rate is reduced to decrease a rate of condensate formation in the charge air cooler and allow the membrane(s) to dry. The length of time the charge motion control device is activated may be equal to the length of time the charge air cooler condensate level remains above the threshold condensate level, wherein the charge motion control device returns to an open position simultaneous to the charge air cooler condensate level decreasing to a level below the threshold condensate level.

At T4, the charge air cooler condensate level reaches the lower threshold condensate level and as a result, the air movement device is disabled. Charge motion control device remains open and the EGR flow rate is constant. After T4, the charge air cooler condensate level increases due to the air movement device being disabled. The EGR flow rate is constant and the charge motion control device is open.

FIG. 5provides an illustration for the method described above with respect toFIG. 4. In this way, a membrane placed in a charge air cooler coupled with an air movement device may control a condensate level in the charge air cooler. A drying air flow provided by the air movement device may be adjusted based on an engine combustion stability limit. By doing this, the condensate level may be maintained to prevent engine combustion degradation and/or an engine misfire. One or more engine operating parameters may be maintained so long as the air movement device is able to maintain the charge air cooler condensate level at a level below a threshold condensate level. Additionally or alternatively, the engine operating parameters may be adjusted in response to the air movement device being unable to maintain the charge air cooler condensate level at a level below the threshold condensate level. The adjustments may include advancing intake cam timing, increasing charge motion, adjusting spark, and reducing or disabling an EGR flow rate. In some examples, the adjustments may be done concurrently (as shown) or separately (not shown).

The technical effect of incorporating a membrane in a charge air cooler is to provide an engine with greater control over condensate levels within an intake system. The membrane(s) in the charge air cooler may be used to maintain a condensation level in the charge air cooler to meet a combustion stability limit.

In an embodiment, method for an engine comprises adjusting a drying air flow directed to a membrane in a charge air cooler in response to a condensate level in the charge air cooler. Additionally or alternatively, the threshold is based on a combustion stability limit of the engine. The method, additionally or alternatively, may further include adjusting the threshold based on the combustion stability limit, wherein the adjusting includes decreasing the threshold as an engine dilution demand is met. The method, additionally or alternatively, may include increasing the drying air flow in response to a condensate level greater than a threshold condensate level, decreasing the drying air flow in response to a condensate level less than the threshold condensate level.

The method, additionally or alternatively, may further include cooling a compressed gas mixture in the charge air cooler, the compressed gas mixture passing over the membrane and depositing water vapor on an inner surface of the membrane, and wherein the drying air flow passes over an outer surface of the membrane and evaporates water from the membrane, without mixing with the compressed gas mixture. Additionally or alternatively, the adjusting includes increasing the drying air flow in response to a combustion stability limit decrease.

An embodiment of a system comprises a charge air cooler upstream of an engine and a membrane separating a charge air path from an exterior of the charge air cooler, a plurality of smaller capillary pores through an inner portion of the membrane in fluid communication with the charge air path, and a plurality of larger capillary pores through an outer portion of the membrane in fluid communication with the exterior of the charge air cooler. The system, additionally or alternatively, may include a compressor upstream of the charge air cooler to provide a compressed gas mixture to the charge air path and an air movement device supplying a drying air flow to the outer portion of the membrane. The air movement device may comprise one or more of a fan, an air pump, and an air duct positioned to direct ram air to the outer portion of the membrane. Additionally or alternatively, the system may include an intake passage fluidically coupling the compressor, the charge air cooler, and the engine. The system may further include a controller with computer-readable instructions for adjusting the air movement device in response to a desired drying rate of the membrane.

The system, additionally or alternatively, may further include that the inner portion of the membrane absorbs water from a compressed gas mixture without absorbing gas from the compressed gas mixture, the water diffuses from the inner portion to the outer portion of the membrane, and the drying air flow evaporates the water from the outer portion of the membrane, without mixing with the compressed gas mixture. The plurality of smaller capillary pores may have a diameter between 3 nm to 10 nm and the larger capillary pores have a diameter between 11 nm to 100 nm. The charge air cooler may comprise a plurality of cooling tubes defining the charge air path, and wherein one or more of the cooling tubes is comprised of the membrane.

Another method for an engine comprises flowing a compressed gas mixture over a membrane positioned in a charge air cooler, the compressed gas mixture depositing water onto an inner portion of the membrane, the water diffusing from the inner portion of the membrane to an outer portion of the membrane, and directing a drying air flow to the outer portion of the membrane to draw water from the membrane to ambient air surrounding the charge air cooler. The method may further include directing the drying air flow comprises directing the drying air flow via one or more of a fan, an air pump, and an air duct.

The method, additionally or alternatively, may include adjusting a drying air flow rate, wherein the adjusting includes increasing the drying air flow rate responsive to an estimated condensate level in the charge air cooler exceeding a threshold condensate level, the threshold condensate level based on a misfire potential of one or more cylinders of the engine. The method may further include adjusting one or more engine operating parameters in response to the condensate level in the charge air cooler exceeding the threshold condensate level even after the drying air flow rate is increased. The method may further include adjusting the one or more engine operating parameters comprises adjusting one or more of an EGR flow rate, intake cam advance and charge motion level, and spark timing.

In an embodiment, method for an engine comprises adjusting a drying air flow directed to a membrane in response to a condensate level in a charge air cooler. The method, additionally or alternatively, may include a threshold based on a combustion stability limit of the engine, wherein adjusting the threshold based on the combustion stability limit, wherein the adjusting includes decreasing the threshold as an engine dilution demand is met. The adjusting may include increasing the drying air flow in response to a condensate level greater than a threshold condensate level, decreasing the drying air flow in response to a condensate level less than the threshold condensate level. Additionally or alternatively, the method may include the charge air cooler comprising cooling passages lined with the membrane, the charge air cooler cooling a compressed gas mixture, the compressed gas mixture passing over the membrane and depositing water vapor on an inner surface of the membrane, and wherein the drying air flow passes over an outer surface of the membrane and evaporates water from the membrane, without mixing with the compressed gas mixture. The adjusting may include increasing the drying air flow in response to a combustion stability limit decrease. Additionally or alternatively, the method may include estimating the condensate level based on an air humidity sensor measurement and an estimate of water vapor concentration contributed by EGR based on air fuel ratio and EGR rate of one or more of an intake air and an EGR flow.

In an embodiment, a system of an engine comprising a charge air cooler upstream of the engine, a membrane separating a charge air path from an exterior of the charge air cooler, a plurality of smaller capillary pores through an inner portion of the membrane in fluid communication with the charge air path, and a plurality of larger capillary pores through an outer portion of the membrane in fluid communication with the exterior of the charge air cooler. The system, additionally or alternatively, may include a compressor upstream of the charge air cooler to provide a compressed gas mixture to the charge air path and an air movement device supplying a drying air flow to the outer portion of the membrane, wherein an intake passage fluidically couples the compressor, the charge air cooler, and the engine.

Additionally or alternatively, the system may include the air movement device comprising one or more of a fan, an air pump, and an air duct positioned to direct ram air to the outer portion of the membrane. The system may further include a controller with computer-readable instructions for adjusting the air movement device in response to a desired drying rate of the membrane. The system, additionally or alternatively, may include the inner portion of the membrane absorbing water from a compressed gas mixture without absorbing gas from the compressed gas mixture, the water diffusing from the inner portion to the outer portion of the membrane, and the drying air flow evaporating the water from the outer portion of the membrane, without mixing with the compressed gas mixture. The system may further include the plurality of smaller capillary pores have a diameter between 3 nm to 10 nm and the larger capillary pores have a diameter between 11 nm to 100 nm. Additionally or alternatively, the system may include the charge air cooler comprising a plurality of cooling tubes defining the charge air path, and wherein one or more of the cooling tubes comprises the membrane

Another method for an engine comprises flowing a compressed gas mixture over a membrane positioned in a charge air cooler, the compressed gas mixture depositing water onto an inner portion of the membrane, the water diffusing from the inner portion of the membrane to an outer portion of the membrane, and directing a drying air flow to the outer portion of the membrane to draw water from the membrane to ambient air surrounding the charge air cooler. Additionally or alternatively, the method may further include directing the drying air flow comprises directing the drying air flow via one or more of a fan, an air pump, and an air duct.

The method, additionally or alternatively, may further include adjusting a drying air flow rate, wherein the adjusting includes increasing the drying air flow rate responsive to an estimated condensate level in the charge air cooler exceeding a threshold condensate level, the threshold condensate level based on a misfire potential of one or more cylinders of the engine. Additionally or alternatively, the method may comprise adjusting one or more engine operating parameters in response to the condensate level in the charge air cooler exceeding the threshold condensate level even after the drying air flow rate is increased. The adjusting may include adjusting the one or more engine operating parameters comprises adjusting one or more of an EGR flow rate, cam timing, charge motion level, and spark timing.