Patent Publication Number: US-2023151784-A1

Title: Method and system for radiator fan operation for charge air cooler ice elimination

Description:
FIELD 
     The present description relates to methods and systems to reduce ice formation in a Charge Air Cooler. 
     BACKGROUND/SUMMARY 
     Turbo charged engines utilize a Charge Air Cooler (CAC) to cool compressed air from the turbocharger, before it enters the engine. Ambient air from outside the vehicle flows across the CAC to cool compressed intake air passing through the passages of the CAC. Condensate may form and freeze in the CAC when the ambient air temperature decreases and the intake air cools below the water freezing point. Sources of the condensate may include both ambient humidity and combustion products recirculated through the crankcase ventilation system into the air intake system upstream of the CAC. Condensate may then be drawn into the engine during acceleration (or tip-in) increasing a likelihood of misfire, and in some examples, increasing a likelihood of engine hydrolock. 
     Other attempts to address ice formation include specialized hardware and/or software actions to increase the temperature of ambient airflow to the CAC. Examples of solutions include active grille shutters or permanent CAC blockers. However, during drive cycles involving prolonged idling in cold environments, such interventions may not sufficiently control CAC condensate freezing. 
     The inventors herein have recognized potential opportunities using the engine coolant system. In one example, the issues described above may be addressed by a method for a vehicle, comprising: operating a radiator fan of the vehicle in a first direction to cool an engine of the vehicle, and reversing a direction of rotation of the radiator fan to blow heated air to a charge air cooler of the vehicle, the charge air cooler arranged proximate a radiator of the vehicle. In this way, the temperature of the CAC may be increased and the potential for ice formation in the CAC reduced. 
     The radiator fan operation may be adjusted based on a drive condition and an engine idle condition. In an example, the radiator fan may be operated in the first direction during the engagement of one or more gears of a transmission of the vehicle. 
     In an example, the first direction of rotation may be maintained so long as the ambient conditions and engine operating conditions are such that engine cooling is desired. Example conditions for maintaining engine cooling may include engine temperature above a threshold and ambient air temperature above a threshold. The direction of rotation of the radiator fan may be reversed for a threshold duration of time in response to an engine idle condition being present for greater than a threshold duration. In this way, the radiator fan operation may be adjusted to maintain engine cooling or CAC warming based on the conditions of the vehicle operation, enhancing engine performance in cold ambient conditions. 
     It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  and  FIG.  1 B  show isometric and perspective views, respectively, of a turbo charged engine system. 
         FIG.  2 A  shows a method for operating a radiator fan in a turbo charged engine system according to a first operation mode. 
         FIG.  2 B  shows a method for operating a radiator fan in a turbo charged engine system according to a second operation mode. 
         FIG.  3    shows a timing diagram for an example prophetic operation of a radiator fan in a turbo charged engine system. 
     
    
    
     DETAILED DESCRIPTION 
     The following description relates to systems and methods for operating an engine coolant radiator fan for charge air cooler (CAC) ice elimination. For example, a method for decreasing ice formation in the CAC may rely on a combination of control logic, electrical components, and air shrouds to blow warm air at the CAC. The radiator fan operation may be adjusted to alternately cool an engine or warm the CAC of a turbo charged engine, such as the turbo charged engine system of  FIGS.  1 A and  1 B . An engine controller may be configured to perform a control routine, such as the routines of  FIGS.  2 A and  2 B , to adjust the radiator fan based on an engine temperature, an ambient temperature, and an engine idle condition. By blowing warm air at the charge air cooler, moisture in the CAC may be minimized and incidence of ice formation in the CAC may be reduced, especially in drive cycles that include extended periods of idle in cold ambient conditions. Reduced ice formation in the CAC may result in fewer incidences of water contaminating engine oil and less likelihood of water entering the intake system through vaporization from the oil, reducing likelihoods of engine misfire and hydrolock. Example radiator fan operations in response to engine temperature, engine speed, and ambient temperature are described with reference to  FIG.  3   . 
       FIGS.  1 A and  1 B  show isometric and front perspective views, respectively, of an embodiment of an engine system. The engine system may be utilized to warm a CAC to decrease the formation of ice. This may occur, for example, on surfaces of heat exchange passages within the charge air cooler when the surfaces are at a temperature less than the freezing point of the ambient air entering the CAC.  FIGS.  1 A and  1 B  are shown approximately to scale. 
     In the illustrated example of  FIGS.  1 A and  1 B , an engine system  100  is depicted. The engine system  100  includes an engine  102 , an engine coolant radiator  106 , a CAC  104  arranged proximate the radiator, and an engine coolant radiator fan  108  captured between the radiator and the engine. In one embodiment, the engine  102  is a turbo charged engine coupled to a boosted air cooling path and an engine cooling loop of a vehicle (not shown). In one example, the vehicle may have a conventional internal combustion engine fueled by gasoline or diesel. In another example, the vehicle may be a hybrid vehicle with multiple sources of torque available for propulsion. The engine system may be controlled at least partially by a controller  170  (shown schematically), and by input from a vehicle operator (not shown). An axis system  162  is given in  FIGS.  1 A and  1 B . The engine system is described in general with respect to  FIG.  1 A  and common elements are similarly numbered in  FIG.  1 B . 
     In the isometric view of  FIG.  1 A , ambient air is introduced to the engine system  100  at intake passage  142  and is filtered in an airbox  110 . An intake hose  114  coupled to the airbox  110  directs filtered air to a compressor (not shown) of the turbocharger system. The compressor may be a suitable intake-air compressor, such as a motor-driven or driveshaft driven supercharger compressor. In one embodiment, the compressor and turbine may be coupled within a twin scroll turbocharger. In another embodiment, the turbocharger may be a variable geometry turbocharger (VGT), where turbine geometry is actively varied as a function of engine speed and other operating conditions. 
     The hot compressed air, e.g., boosted air, exiting the compressor through hose  154  enters the CAC  104  via CAC intake  150 . The hose  154  is coupled to the CAC intake  150  by a coupler  152 . In one example, the CAC may be an air-to-air heat exchanger, as shown in  FIGS.  1 A- 1 B . The CAC  104  may include a plurality of heat exchange passages  156  that run across the CAC along the y-axis. In some examples, the heat exchange passages may be formed from aluminum tubes. Boosted air direction of flow through the aluminum tubes is indicated by arrow  176 . The heat exchange passages  156  provide a conduit for boosted air to be cooled by ambient cross-flow passing through a plurality of gaps  158  between the heat exchange passages  156 . In an example, the ambient air flows between the gaps  158 , perpendicular to the heat exchange passages, along the x-axis, which is indicated by an arrow  178 . The ambient air passing over the aluminum tubes cools the surfaces of the heat exchange passages  156 , cooling the boosted air flowing within the aluminum tubes. In another example, the CAC may be an air-to-liquid heat exchanger. A hose  116  is coupled to the CAC  104  by coupler  138 . Cooled compressed air exiting the CAC  104  at CAC outlet  140  is directed to the engine air intake valve (not shown) via hose  116 . The CAC  104  is coupled to the radiator  106  by a first and a second fastener  147   a ,  147   b  (e.g., bolt, washer). 
     Engine system  100  further includes a cooling system that circulates coolant through engine  102  to absorb waste heat and distributes the heated coolant to radiator  106  via a plurality of coolant lines including at least upper coolant lines  126 ,  128  and lower coolant line  129 . In particular,  FIG.  1 A  shows the radiator  106  positioned between and coupled to the radiator fan  108  and the CAC  104 . The radiator fan  108  is on the interior (e.g., rear facing) of the radiator  106 . The rear of the vehicle is indicated by arrow  180 . The CAC  104  is on the exterior (e.g., front facing) side of the radiator  106 . The front of the vehicle is indicated by arrow  180 . The radiator  106  circulates engine coolant from engine  102  to radiator  106  via upper coolant lines  126 ,  128  and back to engine  102  via lower coolant line  129 . In one example, an engine-driven water pump circulates coolant through passages in the engine block, head, etc., to absorb engine heat, which is then transferred via the radiator  106  to ambient air. A coolant reservoir  112  may collect and distribute (e.g., to the radiator) coolant via one more coolant lines  127 . Coolant may be distributed to the radiator  106  via coolant line  168 . An oil reservoir  118  may supply lubricant to the components of the engine system  100 . 
     The radiator fan  108  may provide airflow assistance and augment an airflow through under-hood components. The radiator  106  is coupled to the radiator fan  108  by first and second fasteners  146   a ,  146   b  (e.g., bolt, washer). The radiator fan  108  may be operated when the vehicle is moving and the engine  102  is running to provide cooling airflow assistance across radiator  106 . Radiator fan  108  may draw a cooling airflow into an under-hood compartment (not shown) through an opening at the front-end of the vehicle, for example, through a grille (not shown). In another example, the radiator fan may be operated when the vehicle is not moving, e.g., engine idling, engine off. In one example, the radiator fan  108  may rotate in a first direction of rotation or a second, reverse direction of rotation based on engine operating conditions. In one example, the radiator fan may rotate in a first direction of rotation (e.g., forward) when one or more conditions are met. The radiator fan may rotate in the second, reverse direction of rotation when one or more other conditions are met. As such, radiator fan  108  activation and operation mode (e.g., forward or reverse direction of rotation) may be based on ambient and operating conditions (e.g., ambient temperature, ambient humidity, engine temperature, transmission engagement status, engine speed) and associated thresholds. In one example, radiator fan  108  may be operated in the reverse direction of rotation, drawing airflow through the radiator  106  to blow heated air toward the CAC  104 . In one example, radiator fan  108  may be operated in a reverse direction of rotation after operating in the forward direction in during the same vehicle operating cycle. A housing of radiator fan  108 , referred to as air shrouds  109 , channels airflow axially (e.g., indicated by arrow  178 ) to minimize radial airflow spread. In this way, more airflow produced by the operation of the radiator fan  108  is directed by the air shrouds  109  towards the intended engine component, such as the CAC  104  or the engine  102 . 
     In one example, radiator fan  108  may be an electrically actuated engine cooling and CAC warming fan. For example, radiator fan activation and operation (e.g., direction of rotation, speed) may be controlled via an electrical input from an alternator  132  and a system battery  130 . The controller  170  may command activation and/or a change in speed (e.g., rotational speed) of radiator fan  108  based on various ambient and engine conditions. In one example, the controller  170  may control the radiator fan  108  via an actuator  124 . The system battery  130  may be coupled to a battery cable  144 . The system battery  130  may provide electric power to components of engine  102  via wire  160 . The wire  160  is in electronic communication with alternator  132 . The electrical system includes a positive terminal wire  134  and negative terminal wire  136 . 
     Radiator fan  108 , when activated, may be capable of operation at different speeds and directions of rotation (e.g., polarity). For example, radiator fan  108  may include each of a lower speed setting and a higher (e.g., faster) speed setting, such that all blades of the radiator fan may spin or rotate collectively at a slower speed or a faster speed, respectively. The radiator fan may also be deactivated and its rotation may be stopped when surplus airflow is not desired and/or when the direction of rotation may be changed (e.g., forward, reverse). In alternate embodiments, radiator fan  108  may operate at a single speed irrespective of the direction of the rotation. It will be appreciated that though  FIGS.  1 A and  1 B  depict a single radiator fan  108 , other example vehicles may include additional radiator fans (e.g., cooling fans coupled to the radiator). 
     The controller  170  may be communicatively coupled to various components of engine system  100  to carry out the control routines and actions described herein. For example, as shown in  FIG.  1 A , the controller  170  may be a microcomputer, including a processor  172  and memory  174 , e.g., for executable programs and calibration values, one or more input/output ports, and a data bus. The controller  170  may receive input from a plurality of sensors, which may include user inputs and/or sensors (such as transmission gear position, gas pedal input, exhaust manifold temperature, air-fuel ratio, vehicle speed, engine speed, mass airflow through the engine, boost pressure, ambient temperature, ambient humidity, intake air temperature, etc.), cooling system sensors (such as coolant temperature, radiator fan speed, passenger compartment temperature, ambient humidity, etc.), charge air cooler sensors, coolant pump speed, and others. The controller may also send a plurality of control signals to various engine actuators (e.g., actuator  124  for control of the radiator fan  108 ) in order to adjust engine operation based on signals received from the sensors. For example, radiator fan rotation speed and/or direction may be controlled by the controller  170  responsive to one or more engine operating conditions and/or input from the one or more sensors, such as ambient temperature sensor  121 , engine temperature sensor  122 , and engine speed sensor  123 . The speed and/or direction (e.g., operation mode) of the radiator fan may also be based on the conditions exceeding one or more thresholds, as described below in reference to  FIG.  2 A ,  FIG.  2 B , and  FIG.  3   . 
       FIG.  1 B  shows a perspective view of the engine system  100 .  FIG.  1 B  shows CAC  104  coupled to the exterior facing side of the radiator  106  at fasteners  147   a ,  147   b , positioning the CAC on the front end of the engine system. In one example, the CAC  104  is vertically smaller than the radiator  106 . In another example, the CAC is spaced away from the radiator, with a space longitudinally between and fully separating the CAC  104  and the radiator  106 . The radiator  106  is coupled to exterior facing (or vehicle front end facing) side of the radiator fan  108  at fasteners  146   a ,  146   b , positioning the radiator between the CAC and the radiator fan. In one example, the radiator fan  108  is directly longitudinally behind the radiator  106 . The engine  102  is behind the radiator fan  108 . Fresh coolant is directed into a first radiator tube  164  of the radiator  106  via coolant line  168 . A second radiator tube  166  collects spent coolant. Spent coolant is directed away from the radiator  106  via lower coolant line  129  (in  FIG.  1 A ). Components of the electrical system are shown including system battery  130 , positive terminal wire  134 , negative terminal wire  136 , and battery cable  144 . 
     In one example, ambient air may enter at intake passage  142  and be directed into the turbocharger compressor for compression. Hot compressed air flows from the compressor entering the CAC  104  at CAC intake  150 . The hot compressed air flows through the CAC  104  along the y-axis from left to right, as indicated by arrow  176 , via the plurality of heat exchange passages  156 , exiting the CAC  104  as cooled compressed air via CAC outlet  140 . Cooled compressed air is directed to the air intake manifold (not shown) of the engine  102  via hose  116 . 
     Condensate may form and accumulate in the CAC when the ambient air temperature decreases, and may freeze when the condensate cools below the water freezing point. Condensate may collect in the CAC, and then be drawn into the engine at once during acceleration (or tip-in) increasing the chance of engine misfire and reducing engine performance. Thus, as elaborated herein with reference to  FIGS.  2 A,  2 B, and  3   , under certain conditions the temperature at the CAC may be increased by adjusting the operation of the radiator fan such that frozen condensate formation and engine misfire events are reduced. 
     Now turning to  FIG.  2 A , an example method  200  is shown for adjusting operation of a radiator fan based on an engine temperature, an ambient temperature, and select engine idle conditions. The radiator fan may be included in an engine system such as the engine system  100  of  FIGS.  1 A- 1 B . In one example, the radiator fan may be adjusted from a first direction, e.g., a normal mode, to a second, reverse, direction, e.g., a cold mode, based on a determination of increased potential for ice formation in the CAC. In  FIG.  2 B , an example method  250  is shown for adjustment of the radiator fan following a determination to adjust the fan operation from the first direction to the second direction. Instructions for carrying out method  200  and the rest of the methods included herein may be executed by a controller based on instructions stored on a memory of the controller and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference to  FIG.  1 A . The controller may employ engine actuators of the engine system to adjust engine operation, according to the methods described below. 
     At  202 , the method  200  includes estimating and/or measuring engine operating conditions. These include, for example, engine speed and load, transmission engagement status, torque demand, boost, manifold pressure (MAP), manifold aircharge temperature (MCT), air-fuel ratio (lambda), fuel alcohol content, barometric pressure, ambient conditions (e.g., ambient air temperature, pressure, humidity, etc.), engine pre-ignition history, etc. 
     At  204 , the method  200  includes determining the status of the radiator fan, e.g., on or off. This may include the controller directly retrieving the status of the radiator fan, e.g., power supply of the radiator fan. The controller may operate the radiator fan during engagement of one or more gears of a transmission of the vehicle, in one example. In another example, the controller may operate the radiator fan if engine cooling is desired. In an example, a radiator fan powered on may operate in a normal mode as a default setting. In an example, the radiator fan operating in normal mode may include the fan blades rotating in an orientation to direct airflow toward the engine. In an example, the radiator fan operating in normal mode draws ambient air through the radiator to flow cooled air in the direction of the engine. In one example, normal radiator fan operation may include a preset and/or calibrated radiator fan speed (e.g., rotations per minute (RPM)). In another example, normal radiator fan operation may include a range of speeds based on engine temperature. 
     If it is determined that the radiator fan is not on, the method  200  may continue to  206 . At  206 , the method  200  includes maintaining nominal settings. In one example, operating at nominal conditions includes operating the engine at low speed-loads and low engine temperature, e.g., engine warm up. 
     Returning to  204 , if it is determined that the radiator fan is on, the method  200  may continue to  208 . At  208 , the method  200  includes determining if the engine temperature is greater than a first threshold. In one example, the first threshold may be a preset non-zero temperature threshold. The controller may determine the engine temperature by a signal received from a sensor, such as the engine temperature sensor  122  of  FIG.  1 A , and compare the temperature to the first threshold. As one example, a first threshold may be a temperature within 5% of the optimal operating temperature, as determined by engine testing. If the engine temperature is above the first threshold, the method continues to  210 . 
     At  210 , the method  200  includes maintaining normal mode radiator fan operation. In an example, maintaining normal mode radiator fan operation may include making no adjustment from the normal mode setting of radiator fan operation, e.g., the direction of rotation to cool the engine of the vehicle. In another example, maintaining normal radiator fan operation may include maintaining the normal mode direction of rotation while allowing for adjustments to operation settings of that mode, such as adjusting the radiator fan speed based on engine operating conditions such as temperature. 
     Returning to  208 , if the engine temperature is not above a threshold temperature, the method  200  continues to  212 . At  212 , the method includes determining if the ambient temperature is above a second threshold. In one example, the second threshold may be a preset non-zero temperature threshold that is different from the first threshold. In one example, the second threshold is set to an ambient temperature sufficiently warm to mitigate ice formation in the CAC. 
     The controller may determine the ambient temperature by a sensor, such as the ambient temperature sensor  121  of  FIG.  1 A , and compare the temperature to the second threshold, e.g., an ambient temperature threshold. In one example, the ambient temperature threshold may include an air temperature above the freezing point of water e.g., greater than 0° C. In other examples, additional or alternative ambient conditions may be included in the method, such as ambient humidity and/or other weather conditions. If the ambient temperature is above the second threshold, the method continues to  210  where normal fan operation is maintained as described above. If the ambient temperature is not above the second threshold, the method continues to  214 . 
     At  214 , the method includes determining whether an engine idle condition is present for greater than a third threshold. The third threshold may be a preset non-zero idle duration of time. In one example, prolonged idling may increase ice formation in the CAC by reducing the flow of hot compressed air from the turbocharger. In one example, the engine idle condition includes feedback controlling the idle speed to a set engine idle speed by adjusting engine output torque, such as through air and/or fuel and/or spark control. In an example, the engine may be transitioned into or out of idling based on various factors such as pedal position, braking, vehicle speed, and engine speed. In an example, the controller may control the vehicle in idle mode when the engine speed decreases below an idle threshold speed, e.g., as measured by the sensor  122  of  FIG.  1 A . In another example, the controller may exit the engine idle condition based on driver demanded torque. In one example, a duration of the engine idle condition may be compared to a preset non-zero engine idle duration threshold. In one example, the third threshold may be set based on a lookup table of ambient temperatures and associated idling durations. As an example, the idling threshold, e.g., third threshold may be set to 60 seconds at an ambient temperature of −5° C. In another example, the third threshold may be set to 20 seconds at an ambient temperature of −25° C. If it is determined that the vehicle is in the engine idle condition for less than the third threshold, the method continues to  210  to maintain normal mode fan operation. If it is determined that the vehicle is in the engine idle condition for greater than the third threshold, the method continues to  216 . 
     At  216 , the method includes operation of the radiator fan in a cold mode. In one example, operating the radiator fan in the cold mode may include reversing the normal direction of airflow to flow air ambient air warmed by the engine coolant radiator toward the CAC, e.g., CAC  104  of  FIGS.  1 A- 1 B . In one example, the radiator fan may be operated in a reverse direction of rotation after operating in the forward direction in during the same vehicle operating cycle. When operating, the radiator fan may direct air current in one orientation (e.g., forward, reverse). In one example, the radiator fan may flow air toward the engine (e.g., forward) or toward the CAC (e.g., reverse). Therefore, in one example, the decision to operate the radiator fan in the cold mode may be made by sequentially ruling out a first condition where the engine is too warm to reverse airflow, a second condition where the ambient temperature is sufficiently warm such that reversing the airflow is not demanded, or a third condition where the vehicle idles only briefly. In one example, the first, second and third conditions are the conditions described in steps  208 ,  212 , and  214  of the method  200 . In an example, an additional condition may include in response to increasing humidity in the CAC operating the radiator ran in a reversed direction. In this way, the decision to operate the radiator fan in the cold mode may be made based on whether the engine system can support a deviation from normal fan operation and whether there is an increased potential for ice formation. The adjustment of the fan to cold mode operation is described in  FIG.  2 B . 
     Turning to  FIG.  2 B , a method  250  for controlling the transition between radiator fan modes is described. The method begins at  252  where a transition to cold mode is described. It may be understood that an abrupt change from a first direction to a second direction may be undesirable for cooling system components. Thus, at  252 , the method  250  includes four interim steps to transition the fan from operating in the normal mode to operating in the cold mode. First, at  252   a , the radiator fan speed may be reduced to stop by tapering the fan speed to zero. In one example, the rate of radiator fan speed reduction may be a preset rate and/or a rate calibrated to bring the fan from a known speed to zero RPM. In one example, the radiator fan speed may be reduced at a preset rate for a preset duration. Next, at  252   b , the radiator fan direction may be set to a cold mode. The cold mode fan orientation reverses the normal airflow of the radiator fan. In one example, the cold mode orients the fan to flow air in the direction towards the CAC. The radiator fan in cold mode draws ambient air through the radiator to direct warmed air in the direction of the CAC. The method then includes setting a new speed at  252   c . In one example, a cold mode speed may be a rate of radiator fan rotation. In one example, the cold mode speed may be less than the normal mode speed, e.g., 50% of normal mode speed, and in another example, the cold mode speed may be the same as the normal mode speed. In one example, the cold mode speed may be determined based on the ambient conditions, e.g., faster speeds at colder ambient air temperatures. The method  250  then includes increasing the speed of the radiator fan to the new set speed at  252   d . In one example, the fan speed may ramp up at a preset rate. 
     With the radiator fan operating in cold mode, the method  250  continues to  254 . In one example, the method  250  includes maintaining operation of the reversed direction of rotation for a threshold duration. Thus, at  254 , the method  250  includes determining whether the radiator fan operation in cold mode has been maintained for greater than a threshold duration. In one example, a threshold duration of time may be a preset non-zero duration of time. In one example, a threshold duration of time may be a fixed calibratable duration. In one example, the threshold duration of time may be variable and determined during operation based on signals received from an ambient temperature sensor, such as ambient temperature sensor  121  of  FIG.  1 A . In one example, a lookup table of ambient temperatures and associated durations to prevent ice formation based on engine testing may be accessed to determine the threshold duration. In one example, a threshold duration of time may be longer during colder ambient conditions. If it is determined that the radiator fan operation in cold mode has been maintained for greater than a threshold duration of time, the method continues to  260 , where normal fan operation may be resumed. 
     In one example, normal fan operation may include the fan blades rotating in such a manner as to flow air in the direction of the engine, drawing ambient air into the engine compartment, past the radiator, to the engine block. In the normal mode, ambient air may be cooled by passing through the radiator. As described above, an abrupt change to the direction of airflow from the radiator may be undesirable for cooling system components. Thus, the method continues to  262  where a transition from cold mode to normal mode is included. 
     At  262 , the method  250  includes four interim steps to transition the fan from operating in cold mode to operating in normal mode. At  262   a , the rotational speed of the radiator fan may be slowed to stop, e.g., tapered to zero RPM. In one example, the rate of radiator fan speed reduction may be a preset and/or calibrated rate. In one example, the radiator fan speed may be reduced at a preset rate for a preset duration. At  262   b , the radiator fan direction may be set to normal mode, restoring the normal, e.g., default, orientation of the radiator fan drawing ambient air through the radiator and directing cooled airflow toward the engine. At  262   c , the method  250  includes setting a normal mode speed. In one example, a normal mode speed may be a rate of radiator fan rotation. In one example, the normal mode speed may be a preset and/or calibrated speed. In one example, there may be a single normal mode fan speed. In another example, the normal mode speed may be determined based on the ambient conditions, e.g., faster speeds at colder ambient air temperatures. In another example, the normal mode fan speed may be determined based on engine operating conditions, e.g., engine coolant temperature. At  262   d , the method  250  includes increasing the speed of the radiator fan to the set speed. In one example, the fan speed may ramp up at a preset rate. 
     From 262 the method  250  may return to the method  200  of  FIG.  2 A , where the controller may continue to evaluate the engine system and ambient conditions with respect to radiator fan operation. 
     Returning to  254 , if it is determined that the radiator fan operation in cold mode has been maintained for less than a threshold duration of time the method continues to  256 . In one example, the method  250  includes terminating the maintaining operation of the radiator fan in cold mode in response to an override condition. Thus, at  256 , the method includes the checking override conditions. In an example, there may be conditions where it is not advantageous to flow air in the direction of the CAC and away from the engine. As an example, override conditions may be thresholds, e.g., temperature thresholds, set for sensors that indicate of engine overheating. An override condition may include engine temperature, engine coolant temperature, and/or ambient temperature increasing above a threshold temperature, respectively. 
     At  258 , the method includes determining whether one or more override conditions are met. Determining whether one or more override conditions are met may include receiving signals from one or more sensors, e.g., engine coolant sensor, engine temperature sensor, exhaust temperature sensor, and comparing the signal received to a corresponding threshold. If no override conditions are met, the method may return to  254 . If one or more override conditions are met, the method continues to  260 , where maintained operation of cold mode terminates and normal mode fan operation resumes. 
     In an example of the method, the radiator fan operation in cold mode may be maintained for a preset duration of time, as described above. In another example, the radiator fan operation in cold mode may be maintained for a duration based on signals received from one or more sensors of the engine system. For example, a CAC intake temperature sensor (e.g., positioned proximate the CAC intake  150  of  FIGS.  1 A- 1 B ) may detect the temperature of the air entering the CAC. The CAC intake temperature sensor may signal to the controller to maintain cold mode fan operation until CAC intake temperature increases above a threshold temperature. In another example of the method, a CAC humidity sensor (e.g., positioned proximate the CAC outlet  140  of  FIGS.  1 A- 1 B ) may detect the humidity of the air exiting the CAC intake passage. The CAC humidity sensor may signal to the controller to maintain the cold mode fan operation until the humidity increases above a threshold humidity indicating reduced likelihood of ice formation in the CAC. 
       FIG.  3    shows a timing diagram  300  for an example prophetic operation of a radiator fan in a turbo charged system, according to the method  200  of  FIG.  2 A  and the method  250  of  FIG.  2 B . The timing diagram  300  illustrates an adjustment of the operation of a radiator fan to reduce the accumulation of frozen condensate in a CAC during cold ambient weather conditions based on an engine temperature condition, an ambient temperature condition, and an engine idle condition. The horizontal (x-axis) denotes time and the vertical markers t0-t7 identify relevant times in the methods of  FIGS.  2 A and  2 B  of the operation the radiator fan. As elaborated in timing diagram  300 , an engine temperature is indicated at graph  302 . In the example, the engine temperature is determined based on a signal received from an engine temperature sensor, such as engine temperature sensor  122  of  FIG.  1 A . An engine speed is indicated at graph  304 . In the example, the controller may use feedback from an engine speed sensor, such as the engine speed sensor  123  of  FIG.  1 A  to transition between and/or maintain a drive condition and an engine idle condition. At graph  306 , an ambient temperature is indicated by ambient temperature sensor, such as the ambient temperature sensor of  121  of  FIG.  1 A . CAC intake temperature is indicated at graph  308 , as measured by a CAC temperature sensor. CAC humidity is indicated at graph  310 , as measured by a CAC humidity sensor. Radiator fan mode, e.g., forward, off, reverse, is indicated at graph  312 . Radiator fan mode is determined by the engagement or disengagement of a radiator fan actuator, determined based on engine operating conditions and adjusted by the controller. The radiator fan actuator is engaged the forward direction when the radiator fan is in the normal mode. The radiator fan is engaged in the reverse direction when the radiator fan is in cold mode. The radiator fan is disengaged when the radiator fan is powered off. Graph  314  indicates a speed of radiator fan blade rotation, determined based on engine operating conditions and adjusted by the controller. The graphs  302 ,  304 ,  306 ,  308 ,  310 , and  314  show an increase upwards along the y-axis. 
     Prior to t0, the engine is powered off. At t0, the engine is powered on. From period t0 to t1, the engine system warms and the driver requests increase torque by depressing an accelerator pedal. The engine system is operating in cold ambient conditions, such that for the duration of the example timing diagram  300 , the ambient temperature remains below a temperature threshold  320 . For example, the temperature threshold  320  is calibrated to the temperature where water freezes (e.g., 0° C.). Graph  302  shows engine temperature increasing toward the engine temperature threshold  316  between t0 and t1. For example, the engine temperature threshold is a lower limit of a desirable engine operating temperature range calibrated to the engine system (e.g., 90° C.). Graph  304  shows engine speed increasing as vehicle is operating in a drive condition. The CAC intake temperature increases above ambient temperature (e.g., a CAC temperature threshold  322 ) and the CAC humidity decreases below ambient humidity  324  as the engine system warms. Between t0 and t1, the radiator fan mode is off (e.g. radiator fan actuator disengaged, fan blade rotation speed zero) as engine temperature has not surpassed the engine temperature threshold  316 . 
     At t1, in response to the engine temperature increasing above the engine temperature threshold  316  (graph  302 ), the radiator fan is operated in the forward (normal) mode (graph  312 ). The fan blade rotation speed (graph  314 ) ramps to high, e.g., 1200 RPM. In response to the fan operation in normal mode, the CAC humidity declines following t1 and stabilizes from t1-t2. Also from t1-t2, the CAC intake temperature (graph  308 ) remains relatively stable from t1-t2 due to the warming effect of the engine. The engine temperature (graph  302 ) remains relatively stable from t1-t2 due to the cooling effect of the radiator fan operating in normal mode. From t2-t3, the engine speed reduces in response to a decrease in demand for torque and approaches an engine idle condition threshold  318 . For example, the engine idle condition threshold is 600 RPM. As engine speed decreases, engine temperature (graph  302 ) conditions remain relatively stable and the radiator fan operation is maintained in the forward mode (graph  312 ). CAC intake temperature (graph  308 ) declines and CAC humidity (graph  310 ) increases as the turbo speed ramps down, reducing heating of compressed air to the CAC intake. 
     At t3, the engine speed drops below the idle condition threshold  318 , indicating control of the vehicle in the engine idling condition. An engine idling condition threshold duration of time extends between t3-t4. Between t3-t4, in response to the engine idling, the engine temperature (graph  302 ) decreases below the engine temperature threshold (e.g., 190° C.). In response to the reduction of compressed air flowing from the compressor into the CAC, the CAC intake temperature decreases below the threshold  322  and the CAC humidity increases above ambient humidity  324 . As the timeline approaches t4, the ambient and engine operating conditions are conducive to the formation of ice. 
     At t4, the vehicle has idled for greater than the threshold duration of time. In response to the vehicle having been in the engine idle condition (e.g., below the idle condition threshold  318 ) for greater than the threshold duration of time, the controller adjusts the radiator fan operation to cold mode. From t4 to t5, the adjustment of the radiator fan is made according to the method  250 . Radiator speed (graph  314 ) is reduced to zero. With radiator speed at zero, the radiator fan mode (graph  312 ) is first disengaged to off and then engaged into reverse. The radiator fan rotation speed ramps to a cold mode fan speed. In this example, an ambient temperature at 0° C. sets the cold mode fan speed to 600 RPM, or approximately half the speed of the normal mode. 
     At t5, the radiator fan operates in cold mode drawing ambient air through the radiator. From t5-t6, the air warms as it passes through the radiator, raising the temperature of the CAC (graph  308 ) and reducing the formation of ice. The humidity of the CAC (graph  310 ) decreases as the CAC is warmed. In this example, the radiator fan operates in cold mode for a preset threshold duration of time (t5-t6). While the radiator fan operates in cold mode, the controller may check override conditions. For example, with the airflow from the radiator fan directed away from the engine, the engine temperature (graph  302 ) increases, but remains below the engine temperature threshold  316  for the duration of t5-t6. 
     At t6, the radiator fan has operated in the cold mode for the threshold duration of time. In response, the controller adjusts the radiator fan operation to normal mode. From t6-t7, the adjustment of the radiator fan is made according to the method  250  of  FIG.  2 B . Radiator fan speed (graph  314 ) is reduced to zero. With radiator fan speed at zero, the radiator fan mode (graph  312 ) is first disengaged to off and then engaged in forward. The radiator fan speed ramps to the normal mode set speed, which in this example is high (e.g., 1200 RPM). 
     At t7, the radiator fan is operating in normal mode. Also at t7, the driver increases vehicle speed, resulting in the engine speed rising above the idle condition threshold  318 , indicating the vehicle operating in the drive condition. In the drive condition, the CAC intake temperature increases and the CAC humidity decreases as the turbo charger spools and feeds warm compressed air to the CAC. 
     In this way, radiator fan operations may be controlled in response to engine operating conditions and ambient conditions. By adjusting the radiator fan operation based on engagement of one or more gears of the transmission, engine temperature, ambient temperature, and vehicle idling, an engine cooling system may cool or warm components of the vehicle system. Adjusting an operation of a radiator fan in this way allows for adequate engine cooling during driving operations, while reducing condensate ice formation in a CAC during engine idle. For example, the condensate is reduced because the CAC may be maintained sufficiently warm to prevent condensate formation without or with the use of active grille shutters or permanent CAC blockers additional robustness during drive cycles with extended periods of idle. The technical effect of reducing condensate ice formation in the CAC is that engine performance may be enhanced during cold ambient conditions. 
       FIGS.  1 A and  1 B  show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example. 
     The disclosure also provides support for a method for a vehicle, comprising: operating a radiator fan of the vehicle in a first direction to cool an engine of the vehicle, and reversing a direction of rotation of the radiator fan to blow heated air to a charge air cooler of the vehicle, the charge air cooler arranged proximate to a radiator of the vehicle. In a first example of the method, the operating of the radiator fan in the first direction is during engagement of one or more gears of a transmission of the vehicle. In a second example of the method, optionally including the first example, the method further comprises maintaining operation of the reversed direction of rotation for a threshold duration. In a third example of the method, optionally including one or both of the first and second examples, the threshold duration is a duration of time. In a fourth example of the method, optionally including one or more or each of the first through third examples, reversing the direction is in response to an engine idle condition being present for greater than a non-zero idle duration. In a fifth example of the method, optionally including one or more or each of the first through fourth examples, reversing the direction is in response to engine temperature less than an engine temperature threshold. In a sixth example of the method, optionally including one or more or each of the first through fifth examples, reversing the direction is in response to ambient temperature less than an ambient temperature threshold. In a seventh example of the method, optionally including one or more or each of the first through sixth examples, reversing the direction is in response to the radiator fan operating in the first direction. In an eighth example of the method, optionally including one or more or each of the first through seventh examples, the method further comprises terminating the maintaining operation in response to an override condition. In a ninth example of the method, optionally including one or more or each of the first through eighth examples, reversing the direction is in response to increasing humidity. 
     The disclosure also provides support for a method for operating a vehicle, comprising: operating a radiator fan of the vehicle in a first direction to cool an engine of the vehicle, the radiator positioned between the engine and a charge air cooler, and operating the radiator fan of the vehicle in a second, reverse, direction to blow heated air to the charge air cooler of the vehicle in response to an idle condition where an increased potential for ice formation is determined. In a first example of the method, determining an increased potential for ice formation is based on an engine temperature, an ambient air temperature, and an engine idle condition. In a second example of the method, optionally including the first example, the method further comprises: transitioning between operating the radiator fan of the vehicle in the first direction and the second direction, the transitioning including reducing a speed of the radiator fan to zero, setting a direction of rotation of the radiator fan, setting a new speed of the radiator fan, and increasing the speed of the radiator fan to the new set speed. 
     The disclosure also provides support for a system for a vehicle, comprising: a turbocharger, a cooling system having a temperature sensor, a charge air cooler positioned at a front end of the vehicle, the charge air cooler coupled to the turbocharger, a radiator fan, and a radiator positioned between the charge air cooler and the radiator fan, a controller having instructions stored therein that, when executed, cause the controller to operate the radiator fan in a first direction to cool an engine of the vehicle in response to the temperature sensor, and reverse a direction of rotation of the radiator fan to a second direction to blow heated air to the charge air cooler of the vehicle in response to select engine idle conditions. In a first example of the system, the controller further includes instructions to maintain operation of the second direction of rotation for a threshold duration. In a second example of the system, optionally including the first example, the select engine idle conditions include engine idle during ambient temperature less than an ambient temperature threshold. In a third example of the system, optionally including one or both of the first and second examples, the controller further includes instructions for terminating the maintained operation in response to an override condition. In a fourth example of the system, optionally including one or more or each of the first through third examples, the charge air cooler is vertically smaller than the radiator. In a fifth example of the system, optionally including one or more or each of the first through fourth examples, the charge air cooler is spaced away from the radiator, with a space longitudinally between and fully separating the charge air cooler and the radiator. In a sixth example of the system, optionally including one or more or each of the first through fifth examples, the radiator fan is directly longitudinally behind the radiator. 
     Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations, and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system, where the described actions are carried out by executing the instructions in a system including the various engine hardware components in combination with the electronic controller. 
     It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed four, and other engine types. Moreover, unless explicitly stated to the contrary, the terms “first,” “second,” “third,” and the like are not intended to denote any order, position, quantity, or importance, but rather are used merely as labels to distinguish one element from another. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. As used herein, the term “approximately” is construed to mean plus or minus five percent of the range unless otherwise specified. 
     The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.