Abstract:
A system for a virtual frost sensor is disclosed including a method for operating the virtual frost sensor. The method includes determining a first temperature indicative of a fluid upstream of the component and determining a second temperature indicative of a fluid downstream of the component. The method also includes sensing at least one engine parameter and determining a first parameter as a function of the at least one engine parameter. The method further includes determining a third temperature indicative of a temperature associated with the engine component as a function of the first temperature, the second temperature, and the first parameter.

Description:
TECHNICAL FIELD 
   The present disclosure relates to a system for a virtual frost sensor system and, more particularly, to a method and apparatus for a virtual frost sensor. 
   BACKGROUND 
   Turbocharged and/or supercharged engine systems typically include a compressor and an air cooler upstream of one or more combustion chambers of an engine. Often, combustion air comprises a mixture of ambient air and recirculated exhaust gas in an attempt to reduce undesirable emissions produced during combustion. Usually, an air cooler is exposed to and utilizes ambient air to cool the combustion air heated by a compressor. Recirculated exhaust gas often includes considerable amounts of water vapor and, in relatively cold environments, the air cooler may lower the temperature of the combustion air below the freezing point of water resulting in frost developing on the inside wall surface of the air cooler. Frost may increase the pressure drop across the air cooler and may adversely and/or undesirably influence engine performance. 
   U.S. Pat. No. 3,596,263 (“the &#39;263 patent”) issued to Ciemochowski discloses an icing condition detection apparatus. The apparatus of the &#39;263 patent includes a first transducer sensing surface temperature of an air intake of a gas turbine engine, a second transducer sensing ambient air temperature, and a third transducer determining humidity. The signals produced by the first, second, and third transducers are delivered to a logic circuit that outputs a control signal to effect operation of a valve controlling exhaust gas recirculation. The logic circuit determines if the surface temperature of the air intake is below a freezing temperature for water and below a dew point of the ambient air. If so, the valve is opened to allow heated exhaust gases to be recirculated to the air intake of the gas turbine engine to increase the surface temperature of the air intake and thus reduce the formation of frost thereon. 
   Although the apparatus of the &#39;263 patent may determine when frost is likely to occur on the surface of the air intake, the apparatus includes a transducer disposed on the surface of the air intake that may decrease the integrity thereof and/or require a complicated mechanical arrangement. Additionally, by recirculating high temperature exhaust gas to heat the air intake surface, the apparatus of the &#39;263 patent may expose exhaust gas including a considerable amount of water vapor across a relatively cold surface thereby potentially increasing the formation of frost. Furthermore, if the recirculated exhaust gas includes after treatment to lower the temperature of the exhaust gas, e.g., to reduce particulates and/or to protect compressor components, the exhaust gas may have a relatively low temperature and may insufficiently heat the air intake surface. 
   The present disclosure is directed to overcoming one or more of the shortcomings set forth above. 
   SUMMARY OF THE INVENTION 
   In one aspect, the present disclosure is directed to a method for operating a virtual frost sensor with respect to an engine component. The method includes determining a first temperature indicative of a fluid upstream of the component and determining a second temperature indicative of a fluid downstream of the component. The method also includes sensing at least one engine parameter and determining a first parameter as a function of the at least one engine parameter. The method further includes determining a third temperature indicative of a temperature associated with the engine component as a function of the first temperature, the second temperature, and the first parameter. 
   In another aspect, the present disclosure is directed to a virtual frost sensor for an engine system having an air cooler. The virtual frost sensor includes first and second sensors configured to produce first and second signals indicative of first and second temperatures, respectively. The virtual frost sensor also includes a third sensor configured to produce a third signal indicative of at least one parameter of an engine system. The virtual frost sensor further includes a controller configured to receive the first, second, and third signals and determine a third temperature indicative of an inner wall temperature of the air cooler as a function of the first, second, and third signals. 
   In yet another aspect, the present disclosure is directed to a method for controlling exhaust gas recirculation with respect to an engine. The method includes sensing a first temperature indicative of ambient air downstream of an air filter and sensing a second temperature indicative of combustion air downstream of an air cooler. The method also includes sensing at least one parameter indicative of an operation of the engine and determining a third temperature indicative of a temperature of an inner wall of the air cooler as a function of the first temperature, second temperature, and the at least one parameter. The method further includes comparing the third temperature with a predetermined temperature and selectively limiting an amount of exhaust gas recirculated from downstream of the engine to the air cooler if the third temperature is less than the predetermined temperature. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of an exemplary engine system including a virtual frost sensor in accordance with the present disclosure; and 
       FIG. 2  is a schematic illustration of an exemplary control algorithm configured to be performed by the controller of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates an exemplary engine system  10 . Engine system  10  may include an engine  12  having a combustion chamber  14  and an inlet manifold  16 . Engine  12  may be configured to transform potential chemical energy, e.g., fuel, into mechanical energy, e.g., torque, via a combustion process, e.g., a two or four cycle piston-cylinder combustion arrangement. Exhaust gas may be directed from combustion chamber  14  toward an environment  20  for release thereto. A portion of the exhaust gas may selectively be directed to a mixer  24  via a valve  18 . Valve  18  may include a solenoid actuated variable output valve configured to divert a portion of the exhaust gas produced within combustion chamber  14  toward mixer  24 . Engine system  10  may also include an air filter  26  configured to filter air received from an environment  22  and direct the filtered air toward mixer  24 . Environments  20  and  22  may be the same or different environments and may, for example, include ambient air at any ambient condition. The recirculated exhaust gas, diverted via valve  18 , and the filtered air, directed from filter  26 , may be combined within mixer  24  to establish combustion air directed toward combustion chamber  14 . The combustion air may be compressed via a compressor  28 , directed through an air cooler  30  to reduce temperature, directed to inlet manifold  16 , and subsequently communicated to combustion chamber  14 . 
   It is contemplated that each of the components of engine system  10  described above may embody and/or include any conventional type of component known in the art, such as, for example, an internal combustion engine, e.g., a gasoline or diesel engine, an air filter including a fibrous fabric particulate filter, a gas mixing device, e.g., a pipe union, a heat exchanger, e.g., an air or liquid cooled heat exchanger, and/or a turbocharged or supercharged compressor system. Accordingly, such components are not described in greater detail. It is also contemplated that engine system  10  may include any quantity of additional components known in the art, such as, for example, one or more fans (not shown), an exhaust gas cooler, (not shown), an exhaust gas particulate filter (not shown), a muffler (not shown), and/or a catalytic converter (not shown). 
   Engine system  10  may further include a controller  32  configured to virtually sense frost within air cooler  30  and further configured to control valve  18  to selectively effect an amount of exhaust gas diverted toward mixer  24 . Controller  32  may include one or more microprocessors, a memory, a data storage device, a communications hub, and/or other components known in the art. It is contemplated that controller  32  may be integrated within a general control system capable of controlling additional functions of engine system  10 , e.g., selective control of engine  12 , and/or additional systems operatively associated with engine system  10 , e.g., selective control of a transmission system. Controller  32  may be configured to receive input signals from a plurality of sensors  34 ,  36 ,  38 ,  40 , perform one or more algorithms to determine appropriate output signals, and may deliver the output signals to valve  18 . It is contemplated that controller  32  may receive and deliver signals via one or more communication lines (not referenced) as is known in the art. 
   Sensors  34 ,  36 ,  38 ,  40  may include any conventional sensor configured to establish a signal indicative of a physical parameter. Specifically, sensor  34  may include a temperature sensor configured to produce a signal indicative of a temperature of the filtered air downstream of air filter  26 . Sensor  36  may include a temperature sensor configured to produce a signal indicative of a temperature of the combustion air directed toward inlet manifold  16 . Sensor  38  may include one or more sensors each configured to produce one or more signals indicative of various engine parameters, such as, for example, engine speed, fuel rate, coolant temperature, and/or any other parameter known in the art. Sensor  40  may include one or more sensors each configured to produce one or more signals indicative of various parameters of engine system  10 , such as for example, a mass flow rate, e.g., of exhaust gas directed toward mixer  24  or of combustion air directed toward air cooler  30 , temperature, e.g., compressor outlet temperature or ambient air temperature, pressure, e.g., ambient air pressure, and/or any other parameter of engine system  10 , as desired. It is contemplated that sensors  34 ,  36  may be disposed at any location respectively upstream and downstream of air cooler  30 , and are shown at particular locations for exemplary purposes only. 
     FIG. 2  illustrates an exemplary control algorithm  100 . Control algorithm  100  may be performed by controller  32  to virtually sense frost within air cooler  30  and determine an output  120 , as a function of the virtually sensed frost. Output  120  may influence the control and/or operation of valve  18  and, correspondingly, the amount of exhaust gas recirculated toward inlet manifold  16 . Control algorithm  100  may include receiving a plurality of inputs  102 ,  104 ,  106 , from sensors  34 ,  36 ,  38 ,  40 , performing a plurality of functional relations, e.g., algorithms, equations, subroutines, look-up maps, tables, and/or comparisons,  108 ,  110 ,  112 ,  114 ,  116 ,  118 , and establishing an output, e.g., output  120 , to influence the operation of valve  18 . 
   Inputs  102  and  104  may include a signal configured to be indicative of a temperature of filtered air downstream of air filter  26  and upstream of mixer  24  and a temperature of combustion air downstream of air cooler  30 , respectively. Additionally, input  106  may include one or more signals indicative of one or more engine parameters and/or engine system parameters, e.g., signals from sensors  38  and/or  40 . Inputs  102 ,  104 ,  106  may embody any signal, such as, for example, a pulse, a voltage level, a digital signal, a magnetic field, a digital input, a sound or light wave, and/or other signal format known in the art. 
   Functional relation  108  may be configured to determine a temperature of the ambient air directed from environment  22  through air filter  26 . Functional relation  108  may functionally relate the temperature of the filtered air, e.g., input  102 , with predetermined ambient temperatures. For example, functional relation  108  may multiply input  102  by a predetermined factor indicative of an effect air filter  26  may have on the temperature of ambient air directed therethrough. It is contemplated that functional relation  108  may include any mathematical relation, e.g., addition, subtraction, division, raising to powers, to functionally relate filtered air temperature and ambient air temperatures. It is also contemplated that the ambient air temperature may, alternatively, be determined via a sensor suitably disposed with respect to environment  22  and configured to produce a signal indicative of an ambient air temperature. 
   Functional relation  110  may be configured to determine a mass flow rate of combustion air directed toward or through air cooler  30 . Functional relation  110  may functionally relate the temperature of combustion air directed toward manifold  16 , e.g., input  104 , with one or more engine  12  or engine system  10  parameters, e.g., input  106 . For example, functional relation  110  may functionally relate combustion air temperature, engine speed, fuel consumption, valve timing, and/or ambient air pressure, within one or more predetermined relationships to determine the air cooler mass flow rate. It is contemplated that the air cooler mass flow rate may, alternatively, be determined via a sensor suitably disposed with respect to air cooler  30  and configured to produce a signal indicative of a mass flow rate thereof. 
   Functional relation  112  may be configured to determine a rated mass flow rate of air cooler  30 . Functional relation  112  may functionally relate one or more engine  12  and/or engine system  10  parameters, e.g., input  106 , with predetermined mass flow rates. For example, functional relation  112  may functionally relate engine speed, engine load, and one or more predetermined rated mass flow rates, within one or more predetermined relationships to determine the rated air cooler mass flow rate. It is contemplated that the rated air cooler mass flow rate may be indicative of the mass flow rate of combustion air directed toward or through air cooler  30  for a given engine speed and load. It is also contemplated that the rated air cooler mass flow rate may be determined as a function of empirically determined flow rates for given engine speeds and loads. 
   Functional relation  114  may be configured to determine a parameter indicative of a temperature factor for an inner wall of air cooler  30 . Specifically, the parameter may include a factor indicative of the effect the combustion air and the ambient air may have on a temperature of the inner surface wall of air cooler  30 , e.g., a wall surface exposed to the combustion air. The parameter may be indicative of a wall ratio and may be determined as a function of one or more parameters associated with air cooler  30 , such as, for example, space velocity, vehicle speed, fluid flow dynamics, heat exchange efficiency, and/or any other parameter known in the art to influence wall temperature within a heat exchange device. For example, functional relation  114  may functionally relate the air cooler mass flow rate and the rated air cooler mass flow rate with one or more predetermined parameters via one or more relational maps to establish the wall ratio. It is contemplated that functional relation  114  may include a three-dimensional map representative of, for example, k 1 (M ac /M rtd )−k 2 ; wherein k 1  and k 2  represent constants, M ac  represents the air cooler mass flow rate, and M rtd  represents the rated air cooler mass flow rate. It is contemplated that functional relation  114  may include any mathematical relation, e.g., linear or exponential, and that constants k 1  and/or k 2  may be any suitable constant, e.g., an empirically determined parameter. It is also contemplated that the wall ratio may be represented as a fractional relationship, e.g., the wall ratio may be a dimensionless parameter defined within a range, such as, for example, greater than or equal to zero and less than or equal to one. It is further contemplated that an established wall ratio may vary as a function of changing parameters associated with air cooler  30 . 
   Functional relation  116  may be configured to determine a temperature indicative of a surface wall temperature of air cooler  30 . Specifically, the wall temperature may be determined as a function of the ambient air temperature, the combustion air temperature, and the wall ratio. For example, functional relation  116  may functionally relate the ambient air temperature, e.g., the lowest temperature that the wall of the air cooler might include, with the wall ratio and the difference between the combustion temperature, e.g., the highest temperature that the wall of the air cooler might include, and the ambient air temperature. It is contemplated that functional relation  116  may include a mathematical relationship representative of, for example, T wall =T atm +W ratio (T man −T atm ); wherein T wall  represents the wall temperature, T atm  represents the ambient air temperature, W ratio  represents the wall ratio, and T man  represents the combustion air temperature. It is noted that the inner surface of the wall of air cooler  30  may include a temperature gradient from the inlet of air cooler  30  to the outlet of air cooler  30 . As such, it is contemplated that the wall temperature, determined within functional relation  116 , may be indicative of the lowest temperature point along such a temperature gradient. It is also contemplated that the temperature of the combustion air, as determined from input  104 , may be indicative of the temperature of the combustion air at the outlet of air cooler  30 . As such, the temperature of the combustion air may be determined at any location relative to the outlet of air cooler  30 . 
   Functional relations  108 ,  110 ,  112 ,  114 ,  116  may each include one or more relational maps that may be in the form of, for example, a two- or three-dimensional look-up table and/or one or more equations. Specifically, functional relations  108 ,  110 ,  112 ,  116  may each include an equation functionally relating respective input signals  102 ,  104 ,  106  with predetermined parameters, variables, values, and/or factors to determine specific parameters of engine system  10 , e.g., ambient air temperature, mass flow rate of air cooler  30 , and rated mass flow rate of engine system  10 . Additionally, functional relation  114  may include a relational map, e.g., one or more two- or three-dimensional maps, functionally relating air cooler mass flow rates and rated mass flow rates with predetermined parameters, variables, values, and/or factors to determine a specific wall ratio for air cooler  30 . It is contemplated that the wall ratio may be variable as a function of changing engine  12  and/or engine system  10  conditions, such as, for example, changing ambient temperature, changing engine parameters, and/or other variables associated with operating engine system  10 . It is also contemplated that interpolation and/or an equation may be used to relate air cooler mass flow rate and rated mass flow rate within the look-up tables associated with functional relation  114 . It is further contemplated that functional relations  108 ,  110 ,  112 ,  114 ,  116 , may each be populated with data determined from test equipment, data from predetermined relationships, data selected or desired by one or more operators, and/or data determined by any other suitable manner. 
   Functional relation  118  may be configured to compare the wall temperature with a predetermined value and may establish output  120  as a function thereof. Functional relation  118  may include one or more equations configured to functionally relate the wall temperature and the predetermined value to determine if the wall temperature is greater than the predetermined value and may establish output  120  as a function of thereof. For example, if the wall temperature is less than or equal to the predetermined value, output  120  may, via controller  32 , limit, e.g., prohibit or discontinue, exhaust gas recirculation by, for example, effecting valve  18  to close or remain closed. Similarly, if the wall temperature is greater than the predetermined value, output  120  may not, via controller  32 , limit exhaust gas recirculation. It is contemplated that output  120  may be configured as a flag criteria and, as such, may be configured to influence exhaust gas recirculation only when the wall temperature is less than or equal to the predetermined value. It is also contemplated that the predetermined value may be any value below which exhaust gas recirculation is desired to be limited, such as, for example, a value indicative of a freezing temperature of water, and may or may not include a margin of error, e.g., a percentage or fixed value increase to account for mathematical rounding discrepancies and/or other computational inaccuracies as is known in the art. As such, controller  32 , sensors  34 ,  36 ,  38 ,  40 , and control logic  100 , may virtually sense frost within air cooler  30  and influence control of engine system  10  to limit the recirculation of exhaust gas when frost may be likely within air cooler  30 . It is further contemplated that output  120  may influence the additional algorithms performed by controller  32 , e.g., output  120  may be an input into an algorithm configured to determine an output signal configured to effect movement of valve  18  and thus an amount of exhaust gas recirculation. 
   INDUSTRIAL APPLICABILITY 
   The disclosed system for a virtual frost sensor may be applicable to virtually sense the formation of frost with respect to an engine component. The disclosed system for a virtual frost sensor may virtually sense, e.g., predict, the formation of frost within an air cooler and may allow a controller to limit an amount exhaust gas recirculated as a function thereof. The operation of engine system  10  and, in particular, control algorithm  100  will be explained below. 
   Engine system  10  may be associated with and configured to provide power to any device known in the art, such as, for example, a mobile vehicle, a marine vessel, and/or a generator. Accordingly, engine system  10  may operate in varying and significantly different environments, including, for example, cold climates. In cold climates, an ambient temperature of atmospheric air might be approximately equal to or significantly lower than the freezing point of water. It is noted that the ambient air in cold climates typically includes small amounts of water vapor because of the effects of the dew point, however, exhaust gas produced as a by-product of a combustion process may include considerable amounts of water vapor. It is also noted that if water vapor contacts an object having a surface temperature below the freezing point, the water vapor is likely to freeze and form frost on the surface. 
   Referring to  FIG. 1 , air cooler  30  may be configured to reduce a temperature of combustion air downstream of compressor  28  and upstream of inlet manifold  16 . Air cooler  30  may be exposed to the ambient air associated with a cold climate and may, for example, utilize forced ambient air to cool the combustion air via a suitable heat exchanging device, e.g., an air cooler with fan forced air. As such, the wall surface of air cooler  30  exposed to the combustion air may include a temperature below a predetermined value, e.g., below a freezing temperature of water, and frost may form. The existence of frost may adversely and/or undesirably influence the operation of air cooler  30  and engine system  10  by, for example, increasing a pressure drop across air cooler  30 , reducing the amount of combustion air directed toward inlet manifold  16 , burdening compressor  28 , and/or increasing an amount of energy utilized to supply combustion air toward manifold  16  and subsequently to combustion chamber  14 . 
   Controller  32  may receive a plurality of inputs from sensors  34 ,  36 ,  38 ,  40 , perform one or more algorithms, e.g., control algorithm  100  and/or additional algorithms, and output a control signal to valve  18 . It is contemplated that the additional algorithms may be configured to determine operational output signals to control valve  18 , e.g., effect the degree and/or timing of the opening and/or closing of valve  18 , as a function of one or more parameters of engine  12 , engine system  10 , and/or predetermined or desired relationships. As such, control algorithm  100  may be integrated, e.g., as an input or a subroutine, within one or more of the additional algorithms, performed independently of the additional algorithms, and/or configured to limit exhaust gas recirculation by manipulating, e.g., overriding, an operational control signal for valve  18 . It is also contemplated that control algorithm  100  may prohibit exhaust gas recirculation by prohibiting valve  18  from opening, e.g., prohibiting controller  32  from communicating an output signal to valve  18  to move valve  18  from a closed position toward an open position, and may discontinue gas recirculation by moving valve  18  toward a closed position, e.g., influencing controller  32  to communicate an output signal to valve  18  to move valve  18  from an open position toward a closed position. It is contemplated that the additional algorithms configured to effect movement of valve  18  may determine an output signal as a function of any desired parameter, e.g., a parameter of engine  12 , engine system  10 , and/or a predetermined relationship. 
   Referring to  FIG. 2 , control algorithm  100  may receive input signals  102 ,  104 ,  106  indicative of the filtered air temperature, the combustion air temperature, and one or more engine  12  and/or engine system  10  parameters, respectively. Control algorithm  100  may determine, as a function of the received input signals, an ambient temperature,  108 , an air cooler mass flow rate,  110 , and a rated air cooler mass flow rate,  112 . Control algorithm  100  may also determine a wall ratio,  114 , as a function of the air cooler mass flow rate and the rated air cooler mass flow rate. Control algorithm  100  may further determine a wall temperature,  116 , as a function of the ambient temperature, the combustion air temperature, and the wall ratio, compare the wall temperature with a predetermined value,  118 , and establish output  120  as a function thereof. 
   For example, control algorithm  100  may determine the wall temperature to be substantially equal to 30° F. and may compare the wall temperature with a predetermined value substantially equal to 32° F. As such, control algorithm  100  may determine that frost is likely to occur within air cooler  30 , e.g., virtually sense frost within air cooler  30 , because 30° F. is less than 32° F. Accordingly, control valve  18  (see  FIG. 1 ) may be limited, if not already controlled to divert exhaust gas toward mixer  24 , or may be discontinued, if already controlled to divert exhaust gas toward mixer  24  to reduce an amount of water vapor directed through air cooler  30  and reduce the formation of frost therein. It is contemplated that controller  32  and control algorithm  100  may be performed with respect to any desired set of units, e.g., ° F. or ° C. It is also contemplated that control algorithm  100  may be performed continuously, periodically, with or without a uniform frequency, and/or singularly. It is further contemplated that control algorithm  100  may include a decision step (not shown) configured to determine whether control algorithm  100  should be performed, e.g., determine if the ambient temperature is below a freezing temperature for water. For example, such a decision step may decide that control algorithm  100  may not need to be performed because the ambient air temperature is significantly above the freezing temperature for water, e.g., engine system  10  is not operated within a significantly cold climate. 
   Because control algorithm  100  virtually determines frost with respect to an engine component surface, the integrity of the component may be preserved and/or a complex mechanical arrangement may not be necessary to determine a surface temperature. Additionally, by controlling the recirculation of exhaust gas as a function of the virtually sensed frost, control algorithm  100  may reduce the amount of frost formed on an engine component and thus may reduce adverse effects with respect to engine performance. 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed system for a virtual frost sensor. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents