Coolant flow control system and method

A coolant flow control system includes a fluid cooling device, a coolant bypass circuit, and a controller. The controller is configured to generate a control signal indicative of a desired flow of coolant through the coolant bypass circuit as a function of the projected rate of change in the cooling device temperature gradient.

TECHNICAL FIELD

The present disclosure relates generally to a system and method for controlling coolant flow to a fluid cooling device. Specifically, the present invention relates to controlling coolant flow through an engine aftercooler.

BACKGROUND

As engine emissions requirements become stricter and horsepower ratings increase, aftercoolers on internal combustion engines are required to reject increased heat. The increased heat rejection and a high level of transient operation may cause thermal stress in the aftercoolers. When an engine is operated at a high load for any extended period of time, the aftercooler eventually reaches a steady state thermal condition characterized by a substantially constant temperature gradient through the depth of the aftercooler core. This temperature gradient, combined with the differences in Coefficient of Thermal Expansion (CTE) of the various materials within the core, induces stresses in the core. Changes in engine power and charge-air flow interrupt this balance resulting in a new temperature gradient and a new distribution of stress. A rapid change of the temperature within the core as the core adjusts to the new thermal conditions drives large changes in stress. An increased rate and magnitude of these thermal shock cycles may decrease the life of the aftercooler.

Reducing the overall temperature in which the aftercooler must work is effective in reducing stresses, but may negatively impact engine performance, or result in an increase in aftercooler size. Aftercoolers may also be produced with materials capable of withstanding the stresses inherent in their operation. While higher strength constituent materials are available, many aftercoolers have copper as one of their prime constituents due to its superior heat transfer properties. Many aftercoolers are assembled with a brazing process, a factor that compounds Copper's low mechanical strength. These braze joints are difficult to produce consistently and their fatigue characteristics (or behavior) are difficult to predict. Designing aftercoolers with the proper constraints such that changes in temperature and the corresponding thermal expansion do not set up resulting stresses may also be costly.

Aftercooler bypass circuits and flow control valves are known to those skilled in the art as a means to control the intake manifold air temperature for increased engine performance or reduced engine emissions, while providing the proper level of cooling for the engine block. For example, U.S. Pat. No. 4,697,551 to Larsen, et al, discloses a system with a proportional radiator shuttle valve to allow all or some of the engine coolant to flow through the radiator or alternatively through a radiator bypass flow conduit to the aftercooler. A quick-acting proportional aftercooler shuttle valve can allow mixing of cool coolant from the radiator which bypasses the aftercooler with coolant through the aftercooler.

SUMMARY

In one aspect of the disclosure a coolant flow control system is described. The coolant flow control system includes a fluid cooling device, a coolant bypass circuit, and a controller. The fluid cooling device includes a temperature gradient. The controller is configured to generate a control signal indicative of a desired flow of coolant through the coolant bypass circuit as a function of a projected rate of change in the temperature gradient.

In another aspect of the disclosure, an alternative embodiment a coolant flow control system is described. The alternative embodiment of the coolant flow control system includes a fluid cooling device, a coolant bypass circuit, a coolant bypass valve, an engine, an engine speed sensor,

In another aspect of the present disclosure, a system to control the coolant flow through an aftercooler on an engine is described. The system includes an engine speed sensor, an air temperature sensor, a first coolant temperature sensor, a second coolant temperature sensor, and a controller. The controller is adapted to receive signals from the engine speed sensor, the air temperature sensor, the first coolant temperature sensor, and the second coolant temperature sensor, and generate a signal indicative of the desired position of the bypass valve as a function of the signals.

In another aspect of the present disclosure, a second alternative embodiment of a method to control coolant flow through an aftercooler with a coolant bypass valve on an engine is described. The method includes determining the current surface temperature at one or more locations on the aftercooler and determining the surface temperature at one or more previous times of at least one of the one or more locations on the aftercooler. The desired position of the coolant bypass valve is determined as a function of the current surface temperature at one or more locations on the aftercooler and the surface temperature at one or more previous times of at least one of the one or more locations on the aftercooler.

In another aspect of the present disclosure, an alternative embodiment of a system to control the coolant flow through an aftercooler on an engine is described. The system includes a bypass valve, at least one aftercooler surface temperature sensor and a controller. The controller includes a memory component. Previous aftercooler surface temperatures are stored in the memory component. The controller is adapted receive a signal from the at least one aftercooler sensor and to generate a signal indicative of a desired bypass valve position as a function of the signal and previous surface temperatures stored in the memory component.

DETAILED DESCRIPTION

Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding reference numbers will be used throughout the drawings to refer to the same or corresponding parts.

FIG. 1illustrates an exemplary embodiment of a coolant flow control system100. The coolant flow control system100may include a cooling device102, a fluid source104, a fluid intake conduit106, a fluid destination108, a fluid exit conduit110, a coolant source112, a coolant input conduit114, a coolant output conduit116, a coolant bypass circuit118, and a controller124.

Fluid (not shown) may flow from the fluid source104, through the intake conduit106to the cooling device102, through the cooling device102to the exit conduit110, and through the exit conduit110to the fluid destination108. Coolant (not shown) may flow from the coolant source112, through the input conduit114to the cooling device102, through the cooling device102to the output conduit116, and through the output conduit110to the coolant source112. Heat may be transferred from the fluid to the coolant while the fluid and the coolant flow through the cooling device102as would be known to a person skilled in the art now and in the future.

Fluid may include any substance that is able to flow. Intake fluid may include matter in a liquid state, matter in a gas state, and matter in a vapor state. Intake fluid may include for example atmospheric air, a water based mixture, and oils.

Coolant may include any substance that is able to flow and change state. Coolant may include matter in a liquid state, matter in a gas state, and matter in a vapor state. Coolant may include for example atmospheric air, a water based mixture, and oils.

The cooling device102may include any device through which the coolant and the fluid flow, and in which heat is transferred from the fluid to the coolant. Cooling devices may include but are not limited to aftercoolers, radiators, oil coolers, and air coolers. The cooling device102includes a temperature gradient (not shown). The temperature gradient of the cooling device102may include the rate of change in temperature of portions, areas and components of the cooling device102in relation to displacement from a given reference point. The temperature gradient may be three-dimensional. It is desirable to have minimal or no changes in the temperature gradient, and that any changes in the temperature gradient occur gradually. In mathematical terms the temperature gradient may be defined by the equation:

∇T=(∂T∂x,∂T∂y,∂T∂z)(Eq.⁢1)
Where T is temperature, and x, y, and z are three dimensional space coordinates of the cooling device102. Changes in the temperature gradient will be minimal or non-existent if the change in temperature in relation to location is minimal or non-existent.

In one embodiment, a change in the temperature gradient may be projected through monitoring the surface temperature of the cooling device102. In an alternative embodiment a change in the temperature gradient may be projected by monitoring the temperature of the coolant entering the cooling device102, the coolant exiting the cooling device102, the fluid entering the cooling device102, and the fluid exiting the cooling device102. Other methods known to a person skilled in the art now or in the future may also be used to project a change in the temperature gradient. Methods of controlling changes in the temperature gradient may include controlling the flow of coolant through the cooling device102.

The fluid source104may include the atmosphere204. In this embodiment the fluid includes air from the atmosphere. The air may be compressed before flowing into the cooling device102. Other embodiments may include tanks, or other sources of the fluid as would be known by one skilled in the art now or in the future.

The intake conduit106may include any natural or artificial channel through which fluid is conveyed from the fluid source104to the cooling device102. The exit conduit110may include any natural or artificial channel through which fluid is conveyed from the cooling device102to the fluid destination108. The input conduit114may include any natural or artificial channel through which coolant is conveyed from the coolant source112to the cooling device102. The output conduit116may include any natural or artificial channel through which fluid is conveyed from the cooling device102to the coolant source112. Conduits may include a pipe, an air duct, flexible tubing, and any other device or combination of devices that would be known by a person skilled in the art now or in the future.

The fluid destination108may include any location the fluid flows to after flowing through the cooling device102. The fluid may be cooler after flowing through the cooling device102, and the fluid destination108may include a machine or a part of a machine. For example, the fluid destination108may include a machine air system, a machine hydraulic system, an engine air system, an engine oil system, an engine coolant system, and an engine combustion system. In one embodiment, the fluid destination108may include the air intake manifold of an internal combustion engine.

The coolant source112may include any location of a supply of coolant. For example, the coolant source112may include a coolant supply tank on an engine208or a machine. In another embodiment the coolant source112may include the coolant system through which coolant circulates on an engine208or a machine. In still another embodiment the coolant source112may include atmospheric air or an alternative supply of air. The coolant source112may include any source of the coolant which flows through the cooling device102that would be known by a person skilled in the art now or in the future.

In the depicted embodiment, the coolant returns to the coolant source112after flowing through the cooling device102. In alternative embodiments, the coolant may flow to a destination other than the coolant source112after flowing through the cooling device102.

The coolant bypass circuit118may include any physical interconnection of elements through which the coolant may flow. The bypass circuit118may permit a portion the coolant to flow around the cooling device102, decreasing the volume of coolant flowing through the cooling device102.

The coolant bypass circuit118may include a bypass valve120, and a check valve122. The bypass valve120may control the flow of fluid which flows through the bypass circuit118and the cooling device102. The bypass valve120may include a variable position bypass valve. In an alternative embodiment the bypass valve120may include an open/close position valve. The check valve122may include any device which allows coolant to flow in only one direction. The check valve122may be positioned in the bypass circuit118such that coolant may flow into the bypass circuit118and around the cooling device102, but is unable to flow in the opposite direction.

The controller124may include a processor (not shown) and a memory component (not shown). The processor may be microprocessors or other processors as known in the art. In some embodiments the processor may be made up of multiple processors. The processor may execute instructions for control of the bypass circuit118, such as the methods described below in connection withFIGS. 3 and 4. Such instructions may be read into or incorporated into a computer readable medium, such as the memory component or provided external to processor. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement a steering method. Thus embodiments are not limited to any specific combination of hardware circuitry and software.

The term “computer-readable medium” as used herein refers to any medium or combination of media that participates in providing instructions to processor for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks. Volatile media includes dynamic memory. Transmission media includes coaxial cables, copper wire and fiber optics, and can also take the form of acoustic or light waves, such as those generated during radio-wave and infra-red data communications.

The memory component may include any form of computer-readable media as described above. The memory component may include multiple memory components.

In the illustrated embodiment, the controller124is enclosed in a single housing. In an alternative embodiment, the controller124may include a plurality of components operably connected and enclosed in a plurality of housings. The controller124may be located on-board an engine208(depicted inFIG. 2). In another embodiment, the controller124may be located on-board a vehicle (not shown). In still other embodiments the controller may be located in a plurality of operably connected locations including on-board an engine208, on-board a vehicle, and remotely.

The controller124may be configured to generate a control signal indicative of a desired flow of coolant through the coolant bypass circuit118as a function of a projected rate of change in the temperature gradient. In one embodiment, the control signal may include a signal indicative of a desirable position of the bypass valve120. In other embodiments the control signal may be indicative of any parameter which would indicate a desired flow of coolant through the bypass circuit118known by a person skilled in the art now or in the future. The controller124may be operably coupled to the bypass valve120to deliver a control signal to the bypass valve120.

FIG. 2illustrates an alternative exemplary embodiment of a coolant flow control system200. The coolant flow control system200may include an aftercooler202, an intake air duct206, an engine208, an exit air duct210, a coolant tank212, an aftercooler supply line214, an aftercooler discharge line216, an aftercooler bypass circuit218, a controller224, an air compressor232and a temperature gradient change projection system. Although not shown as distinct element inFIG. 2, elements of the temperature gradient change projection system are shown and will be described further below.

Air from an atmosphere204may flow through the intake air duct206and the air compressor232to the aftercooler202. The air may flow through the aftercooler202to the exit air duct210. The air may flow through the exit air duct210to an intake air manifold of the engine208. Coolant from the coolant tank212may flow through the aftercooler supply line214to the aftercooler202. The coolant may flow through the aftercooler202into the aftercooler discharge line214. The coolant may flow through the aftercooler discharge line214to the coolant tank212. Heat may be transferred from the air to the coolant while the air and the coolant flow through the aftercooler202.

The aftercooler202may include any device which provides an air-to-liquid heat exchanger operable to cool the air flowing from the atmosphere, through the air compressor232, and through the intake air duct206. The aftercooler202may include one or more materials with different Coefficients of Thermal Expansion. The aftercooler202may include a temperature gradient. A temperature gradient change projection system, described in greater detail below, may project a change in the temperature gradient.

The intake air duct206may operably connect the atmosphere204to the aftercooler202such that air flows from the atmosphere to the aftercooler202. The intake air duct206may include any pipe, tube, or passage through which a fluid, including a gas, may be conveyed from the atmosphere204to the aftercooler202that would be known to one skilled in the art now or in the future. The intake air duct206may include metallic tubing and an air compressor232.

The air compressor232may include a turbine. The turbine may include a turbocharger powered by the flow of exhaust gases from the engine208. In an alternative embodiment the turbine may be powered by mechanical or electrical energy from the engine208or another power source. Examples include turbines powered by gears or belts driven by the engine208, and turbines powered by one or more electrical motors. The air compressor may include any device which compresses air known to one skilled in the art now or in the future. The intake air duct206may include more than one air compressor232.

The exit air duct210may operably connect the aftercooler202to the engine208such that air flows from the aftercooler202to the engine208. The exit air duct210may include any pipe, tube, or passage through which a fluid, including a gas, may be conveyed from the aftercooler202to the engine208that would be known to one skilled in the art now or in the future. The exit air duct210may include metallic tubing. Air may flow through the exit air duct210to the intake manifold of the engine208.

The engine208may be an internal combustion engine or any type power source that requires an air supply to operate known to one skilled in the art now or in the future.

The coolant tank212may include any receptacle known by one skilled in the art now or in the future operable to hold fluids. The coolant tank212may be physically attached to the engine208, or may be an integral part of the engine208. In another embodiment the coolant tank212may be located remotely from the engine208. The coolant tank212may be operably connected to the aftercooler202such that coolant from the coolant tank212may flow to and through the aftercooler202. In one embodiment, the coolant tank212may also be operably connected to the engine208such that coolant from the coolant tank212flows to and through the engine208.

The aftercooler supply line214may operably connect the coolant tank212to the aftercooler202. The aftercooler supply line214may include any conduit, channel, or pipe operable to convey fluids known to one skilled in the art now or in the future.

The aftercooler supply line may include a coolant pump240. The coolant pump240may include any device or machine for transferring a gas or liquid from a source or container through tubes or pipes to another container or receiver. The coolant pump240may be operable to pump coolant from the coolant tank212through the aftercooler supply line214to the aftercooler202. The coolant pump may be operable to pump coolant from the coolant tank212through the aftercooler bypass circuit218. The coolant pump240may include a SCAC coolant pump242(separate circuit aftercooler coolant pump). The coolant pump240may be geared or belt driven by the engine208and the rate of coolant pumped by the coolant pump240may be a direct function of engine208speed. In an alternative embodiment, the coolant pump240may include a variable output pump. For example the coolant pump240may include a variable displacement pump with an adjustable swashplate. In another embodiment the coolant pump240may include a pump driven by an power source such as an electric motor wherein the rate of coolant pumped by the coolant pump240is independent of engine208speed.

The aftercooler discharge line216may operably connect the aftercooler202to the coolant tank212such that coolant flows from the aftercooler202and discharges into the coolant tank212. The aftercooler discharge line216may include any conduit, channel, or pipe operable to convey fluids known to one skilled in the art now or in the future.

The aftercooler bypass circuit218may be operable to selectively allow coolant to flow from the aftercooler supply line214to the coolant tank212without flowing through the aftercooler202. The aftercooler bypass circuit218may allow a portion of the coolant flowing through the aftercooler supply line214to flow to the coolant tank212without flowing through the aftercooler202, or alternatively the aftercooler bypass circuit218may allow all of the coolant flowing through the aftercooler supply line214to flow to the coolant tank212without flowing through the aftercooler202. The aftercooler bypass circuit218may include any conduit, channel, or pipe operable to convey fluids known to one skilled in the art now or in the future.

The aftercooler bypass circuit218may include a bypass valve220. The bypass valve220may include any valve operable to control the flow of fluid through the aftercooler bypass circuit218and the aftercooler202known to one skilled in the art now or in the future. In one embodiment the bypass valve220may include a variable position electronically actuated valve operably to vary the size of an orifice the coolant must flow through to enter the aftercooler bypass circuit218. In an alternative embodiment the bypass valve220may be mechanically or hydraulically actuated. In another embodiment the bypass valve220may include a valve with two positions, open and close. The bypass valve220may be operably coupled to the controller224to receive a bypass valve actuation signal indicative of a desired bypass valve position. The bypass valve220may be configured to generate a signal indicative of the valve position.

The check valve222may be operable to prevent coolant entering the aftercooler bypass circuit218from the aftercooler supply line214from flowing back into the aftercooler supply line214and then through the aftercooler. The check valve222may include any device for limiting flow in a piping system to a single direction known by one skilled in the art now and in the future.

The controller224may include one or more housings operably connected. The housings may be located on the engine208, remotely from the engine208, or both on the engine208and remotely. The controller224may include instructions in the memory component to generate a control signal indicative of a desired flow of coolant through the aftercooler bypass circuit218as a function of a projected rate of change of the temperature gradient. The controller224may be operable to implement the methods described in relation toFIG. 3andFIG. 4.

The temperature gradient change projection system may include one or more of an engine speed sensor226, an engine load sensor228, an intake air temperature sensor236, an exit air temperature sensor238, an input coolant temperature sensor244, an output coolant temperature sensor246, and the controller224.

The engine speed sensor226may be configured to generate an engine speed signal indicative of the rotational speed of the crankshaft or flywheel on the engine208. The engine speed sensor226may include any device known by one skilled in the art now or in the future that will generate a signal indicative of the rotational speed of the engine208crankshaft or flywheel.

The engine load sensor228may be configured to generate a signal indicative of the engine208load. The engine load sensor228may include a virtual sensor. The virtual sensor may include a device or combination of devices that may estimate the engine load using mathematical models in conjunction with physical sensors. For example, the virtual sensor may include a fuel flow sensor230configured to generate a signal indicative of the fuel flow in the engine208, the engine speed sensor226, and the controller224. The controller224may be configured to determine the engine208load as a function of the fuel flow signal and the engine speed signal. In another embodiment the virtual sensor may estimate engine208load as a function of other signals from other sensors. In still other embodiments the engine load sensor228may directly measure engine208load through a physical property of the engine208. For example, when the engine208is connected to a driveline, strain gauges may be attached to the driveshaft to directly measure torque. The controller224may calculate engine208load as a function of the driveline torque measurement and engine208parasitics. Another non-limiting example of engine load sensor228, may include an engine208connected to and driving an electric generator. A voltage sensor and a current sensor may measure the electrical power being produced by the generator. The controller224may calculate engine208load as a function of the generator voltage, the generator current, engine208parasitics, and mechanical power losses between the engine208and the generator. The engine load sensor228may include any device or combination of devices known by one skilled in the art now or in the future that may generate a signal indicative of engine208load.

The intake air temperature sensor236may include any device configured to generate an intake air temperature signal indicative of the temperature of the air entering the aftercooler202after exiting the air compressor232known by one skilled in the art now or in the future.

The exit air temperature sensor238may include any device configured to generate an exit air temperature signal indicative of the temperature of the air exiting the aftercooler202before entering the engine218known by one skilled in the art now or in the future.

The input coolant temperature sensor244may include any device configured to generate an input coolant temperature signal indicative of the temperature of the coolant entering the aftercooler202known by one skilled in the art now or in the future.

The output coolant temperature sensor246may include any device configured to generate an output coolant temperature signal indicative of the temperature of the coolant exiting the aftercooler202known by one skilled in the art now or in the future.

The controller224may be operably coupled to the engine speed sensor226to receive the engine speed signal. The controller224may be operably coupled to the engine load sensor228to receive the engine load signal. The controller224may be operably coupled to the intake air temperature sensor236to receive the intake air temperature signal. The controller224may be operably coupled to the exit air temperature sensor238to receive the exit air temperature signal. The controller224may be operably coupled to the input coolant temperature sensor244to receive the input coolant temperature signal. The controller224may be operably coupled to the output coolant temperature sensor246to receive the output coolant temperature signal. The controller224may be configured to project a change in the temperature gradient as a function of the engine speed signal, the engine load signal, the intake air temperature signal, the exit air temperature signal, the input coolant temperature signal, and the output coolant temperature signal, as described below in relation toFIG. 3.

In an alternative embodiment, the temperature gradient change projection system may include aftercooler temperature sensors234, and the controller224. Aftercooler temperature sensors234may include multiple sensors configured to generate multiple signals indicative of the temperature at multiple locations on the aftercooler202surface. The controller224may be configured to receive the temperature signals. The controller224may be configured to project a change in the temperature gradient as a function of the temperature signals, as described below in relation toFIG. 4.

INDUSTRIAL APPLICABILITY

When the temperatures of the coolant and fluid flowing through the cooling device102rise and fall rapidly, the cooling device102may be subject to thermal stress cycles which cause material fatigue and reduce functional life. For example, when an engine208is operated at high load for an extended period of time, the aftercooler202may reach a steady state thermal condition characterized by a substantially constant temperature gradient through the depth of the aftercooler202core. When the engine208load fluctuates rapidly, the aftercooler202may be subject to thermal stress cycles due to rapid changes in the temperature gradient and differences in the Coefficient of Thermal Expansion of the various materials in the aftercooler202core. The coolant control flow method300may reduce these stress cycles by reducing changes in the temperature gradient, and thus extend aftercooler202life.

Referring now toFIG. 3, a coolant flow control method300is depicted. A rate of change in the temperature gradient of the aftercooler202may be projected by calculating the difference318between an estimated heat input314to the aftercooler202and an estimated heat output316from the aftercooler202. The controller224may calculate the difference318and generate a bypass valve actuation signal326to control the flow of coolant through the aftercooler bypass circuit218.

The heat input314to the aftercooler202may include the amount of heat energy that is transferred from the air as it flows through the aftercooler202. The amount of heat energy transferred from the air as it flows through the aftercooler202may be estimated as a function of the flow rate of the air as it enters the aftercooler202, the intake air temperature signal306, and the exit air temperature signal308.

In an embodiment where the air compressor232is a turbocharger, powered by exhaust gas flow from the engine208, the flow rate of air as it enters the aftercooler202may be estimated as a function of engine speed302and engine load304. The controller224may estimate the flow rate of air entering the aftercooler202as a function of the engine speed signal302, the engine load signal304, and experimental data stored in the memory component. In an alternative embodiment the controller224may estimate the flow rate of air entering the aftercooler202as a function of the engine speed signal302; the engine load304; and geometrical, structural, and functional data on the intake air duct206stored in the memory component.

In alternative embodiments where the air compressor232may have an alternative power source, such as an electric motor or mechanical gearing to the engine, other factors such as current into the motor or motor speed may be used to calculate the flow rate of air into the aftercooler202.

In another alternative embodiment an air pressure sensor may be located in the intake air duct206configured to generate an air intake pressure signal indicative of the air pressure as the air flows into the aftercooler202. The controller may be configured to calculate the flow rate of the air as it enters the aftercooler202as a function of the air intake pressure signal.

The heat output316from the aftercooler202may include the amount of heat energy that is transferred to the coolant as it flows through the aftercooler202. The amount of heat energy transferred to the coolant as it flows through the aftercooler202may be estimated as a function of the flow rate of the coolant as it enters the aftercooler202, the input coolant temperature signal310, and the output coolant temperature signal312.

In an embodiment where the coolant pump242is a constant displacement pump, and the pump speed is directly related to engine speed302(such as a pump geared or belt driven by the engine208), the flow rate of coolant as it enters the aftercooler202may be estimated as a function of engine speed302. The controller224may estimate the flow rate of coolant entering the aftercooler202as a function of the engine speed signal302, and experimental data stored in the memory component. In an alternative embodiment the controller224may estimate the flow rate of coolant entering the aftercooler202as a function of the engine speed signal302; and geometrical, structural, and functional data on the aftercooler supply line214stored in the memory component.

In alternative embodiments where the coolant pump242has a variable displacement other factors such as the swashplate angle may be used to calculate the flow rate of coolant into the aftercooler202.

In embodiments where the coolant pump242speed is not dependent on the engine speed302, another method of calculating pump speed or pump output may be used.

In another alternative embodiment a coolant pressure sensor may be located in the aftercooler supply line214configured to generate an coolant input pressure signal indicative of the coolant pressure as the coolant flows into the aftercooler202. The controller may be configured to calculate the flow rate of the coolant as it enters the aftercooler202as a function of the coolant input pressure signal.

The controller224may be configured to determine a desired flow of coolant through the aftercooler bypass circuit318as a function of the difference318between the heat input314and the heat output, and method start parameters320. The controller224may be configured to generate a control signal indicative of the desired flow of coolant through the aftercooler bypass circuit318. The control signal may include a bypass valve actuation signal326. The controller224may be configured to generate the bypass valve actuation signal326as a function of a desired bypass valve position322and the current bypass valve position324. The desired bypass valve position322may be a function of the difference318and method start parameters320. The desired bypass valve position322may be indicative of a desired flow of coolant through the aftercooler bypass circuit318.

Method start parameters320may include any parameters that indicate the engine208has reached a steady state operation level. In an alternative embodiment method start parameters may include other desirable states of operation. The controller224may determine that the engine208has reached a steady state or some other desirable state of operation such that it is desirable to limit the rate of change of the temperature gradient. The controller224may determine that the engine208has reached a steady or other desirable state by any method known to one skilled in the art now or in the future.

Referring now toFIG. 4, an alternative embodiment of the coolant flow control method400is depicted. A projected rate of change of the temperature gradient may be a function of cooling device surface temperatures432and previous cooling device surface temperatures434.

The controller124may be configured to receive temperature signals indicative of the cooling device surface temperatures432. In the embodiment depicted inFIG. 2, the signals may include the temperature signals generated by the aftercooler temperature sensors234.

The controller124may receive the temperature signals at intervals and may store previous temperature signals in the memory component. The previous temperature signals may be indicative of cooling device previous surface temperatures434.

A projected rate of change of the temperature gradient may be a function of the difference418between cooling device surface temperatures432and cooling device previous surface temperatures434. The controller124may be configured calculate the difference418as a function of the cooling device surface temperatures432and the previous cooling device surface temperatures434.

A desired flow of coolant through the coolant bypass circuit118may be determined as a function of the difference418. The desired flow of coolant through the coolant bypass circuit118may be indicative of a desired bypass valve position422. The controller124may be configured to determine the desired bypass valve position422as a function of the difference418and method start parameters420.

The controller124may be configured to generate a control signal indicative of the desired flow of coolant through the coolant bypass circuit118as a function of the desired bypass valve position422and the current bypass valve position424. The control signal indicative of the desired flow of coolant through the coolant bypass circuit118may include a bypass valve actuation signal426.

The bypass valve actuation signal426may actuate the bypass valve120. The actuation of the bypass valve120may generate a coolant flow change428through the coolant bypass circuit118. The coolant flow change428may generate a decrease in the rate of temperature gradient change430.

From the foregoing it will be appreciated that, although specific embodiments have been described herein for purposes of illustration, various modifications or variations may be made without deviating from the spirit or scope of inventive features claimed herein. Other embodiments will be apparent to those skilled in the art from consideration of the specification and figures and practice of the arrangements disclosed herein. It is intended that the specification and disclosed examples be considered as exemplary only, with a true inventive scope and spirit being indicated by the following claims and their equivalents.