Patent ID: 12258898

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no way intended to limit the present disclosure, its application, or uses. It should also be understood that steps within a method may be executed in different order without altering the principles of the present disclosure.

Referring toFIG.1, an exemplary engine system10generally includes a diesel engine12, an alternator14(or generator in some applications), a turbocharger16, and an exhaust aftertreatment system18. The exhaust aftertreatment system18is disposed downstream from a turbocharger16for treating exhaust gases from the diesel engine12before the exhaust gases are released to atmosphere. The exhaust aftertreatment system18can include one or more additional components, devices, or systems operable to further treat exhaust fluid flow to achieve a desired result. In the example ofFIG.1, exhaust aftertreatment system18includes a heating system20, a diesel oxidation catalyst (DOC)22, a diesel particulate filter device (DPF)24, and a selective catalytic reduction device (SCR)26. The exhaust aftertreatment system18includes an upstream exhaust conduit32that receives a heater assembly28therein, an intermediate exhaust conduit34in which the DOC22and DPF24are provided, and a downstream exhaust conduit36in which the SCR26is disposed.

It should be understood that the engine system10illustrated and described herein is merely exemplary, and thus other components such as a NOx adsorber or ammonia oxidation catalyst, among others, may be included, while other components such as the DOC22, DPF24, and SCR may not be employed. Further, although a diesel engine12is shown, it should be understood that the teachings of the present disclosure are also applicable to a gasoline engine and other fluid flow applications. Therefore, the diesel engine application should not be construed as limiting the scope of the present disclosure. Such variations should be construed as falling within the scope of the present disclosure.

The heating system20includes a heater assembly28disposed upstream from the DOC22, and a heater control module30for controlling operation of the heater assembly28. Heater assembly28can include one or more electric heaters wherein each electric heater includes at least one resistive heating element. The heater assembly28is disposed within an exhaust fluid flow pathway in order to heat the fluid flow during operation. Heater control module30typically includes a control device adapted to receive input from the heater assembly28. Examples of controlling the operation of heater assembly28can include turning the heater assembly on and off, modulating power to the heater assembly28as a single unit and/or modulating power to separate subcomponents, such as individual or groups of resistive heating elements, if available, and combinations thereof.

In one form, the heater control module30includes a control device. The control device is in communication with at least one electric heater of the heater assembly28. The control device is adapted to receive at least one input including but not limited to an exhaust fluid flow, mass velocity of an exhaust fluid flow, flow temperature upstream of the at least one electric heater, flow temperature downstream of the at least one electric heater, power input to the at least one electric heater, parameters derived from physical characteristics of the heating system, and combinations thereof. The at least one electric heater can be any heater suitable to heat an exhaust fluid. Example electric heaters include but are not limited to a band heater, a bare wire resistive heating element, a cable heater, a cartridge heater, a layered heater, a strip heater, a tubular heater, and combinations thereof. The physical characteristics may include, by way of example, resistance wire diameter, MgO (insulation) thickness, sheath thickness, conductivity, specific heat and density of the materials of construction, heat transfer coefficient, and emissivity of the heater and fluid conduit, among other geometrical and application related information.

The system ofFIG.1includes the DOC22disposed downstream from the heater assembly28. The DOC22serves as a catalyst to oxidize carbon monoxide and any unburnt hydrocarbons in the exhaust gas. In addition, the DOC22converts nitric oxide (NO) into nitrogen dioxide (NO2). The DPF24is disposed downstream from the DOC22to assist in removing diesel particulate matter (PM) or soot from the exhaust gas. The SCR26is disposed downstream from the DPF24and, with the aid of a catalyst, converts nitrogen oxides (NOx) into nitrogen (N2) and water. A urea water solution injector27is disposed downstream from the DPF24and upstream from the SCR26for injecting urea water solution into the stream of the exhaust gas. When urea water solution is used as the reductant in the SCR26, NOx is reduced into N2, H2O and CO2.

In one form of the present disclosure, data from the engine system10described above is used in a mathematical model to predict various temperatures, including heater temperature, exhaust inlet temperature, and exhaust outlet temperature, among others, without the use of physical sensors. These models have been developed for both transient and non-transient systems and are applicable to a variety of heater types and fluid flow applications. Accordingly, the various forms provided herein of a tubular heater and an engine exhaust should not be construed as limiting the scope of the present disclosure. Further, the specific reference to a “heater sheath” temperature is merely exemplary and the calculated temperature may be for any component of any type of heater such as a band heater, a bare wire resistive heating element, a cable heater, a cartridge heater, a layered heater, a strip heater, or a tubular heater, among others. A “layered heater” has been previously defined in U.S. Pat. No. 7,196,295, which is commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety.

Referring toFIG.2, a tubular heater is used as an example type of heater used in the heater assembly28and is illustrated and generally indicated by reference numeral40. The tubular heater40comprises a resistive heating element42disposed within a sheath44, and an insulation material46disposed therebetween, such as by way of example, a compacted magnesium oxide (MgO). The tubular heater40also may include power pins50and seals52.

The present disclosure provides for a control system and methods of controlling an electric heater that generally include a device/apparatus that uses inputs, such as mass flow or flow velocity, flow temperature either upstream or downstream of the heater, heater power input, and parameters derived from physical characteristics of the system, to then modulate power to the heater based on these inputs. In order to calculate values for the system depending on a set of known variables, a variety of equations are disclosed herein. It should be understood that these equations are merely exemplary and should not be construed as limiting the scope of the present disclosure.

For example, in order to calculate the temperature of the sheath44without the use of physical sensors in an application such as a diesel exhaust as set forth above, mass flow rate, inlet temperature, and power to the heater40are used, along with heat transfer equations, for a variety of heater configurations. In one form, Equation 1 below is used to calculate the temperature of the sheath44(Ts):

Ts=EQUATION⁢1Tout+(kWAs)KD⁢{C2·C·Pr0.36(PrPrs)0.25[Dμ⁢(STST-D)⁢(Min+MfuelAc)]m}where:Ac=heater cross-sectional area;As=sheath area;C=a first constant based on Reynolds number (Re) and Table 1 shown below;C2=offset based on number of heater elements;D=heater element diameter;K=thermal conductivity of air;kW total heater power;Mfuel=mass flow rate of fuel;Min=inlet mass air flow (MAF) rate;m=a second constant based on Reynolds number (Re) and Table 1 shown below;Pr=Prandtl number of air taken at gas temperature;Prs=Prandtl number of air taken at sheath temperature;ST=transverse distance between elements;Tout=heater outlet temperature; andμ=viscosity of air.

TABLE 1ReD,maxC (“C1”)m10-1000.800.40100-1000(Single cylinder(Single cylinderapprox.)approx.)1000-200k0.270.63Single Cylinder40-40000.6830.466NL123456C20.700.800.860.890.900.92ReD,max=Reynolds number for a given diameter and velocity maximum;NL=Number of elements; andC2=When evaluating element1, use NL=1; when evaluating 6 elements,NLstarts at 0.7 and increases to 0.92 as each element is analyzed.

Further, in this Equation 1, radiation effects have not been incorporated, however, may be incorporated while remaining within the scope of the present disclosure.

In addition to heater sheath44temperature, an outlet temperature after each element within the fluid flow stream (seeFIG.3) can be calculated/modeled, thus reducing the need for additional temperature sensors. In one form, the outlet temperature is calculated according to Equation 2 below:

Tout,1=2·m.·CP·Tin,1+h·As(2⁢Ts-Tin,1)2·m.·CP+h·AsEQUATION⁢2where:As=sheath surface area;Cp=specific heat of air at constant pressure;h=convective heat transfer coefficient;{dot over (m)}=mass flow rate;Tout,1=outlet temperature after heating element1;Tin,1=inlet temperature of heating element1; andTs=sheath temperature.

Therefore, using Equation 2, temperatures can be predicted without the use of physical sensors throughout a fluid flow system. As a further advantage, using the equations as set forth herein results in a quicker response time due to the lag time associated with physical sensors, and especially in transient systems. Better accuracy and quicker response times also allows for using heaters that operate at higher temperatures, therefore providing improved performance and decreasing safety margins. Moreover, a failure mode of a physical sensor is removed by the present disclosure.

Because Equation 1 is for steady state, a further underlying equation is used for virtual sensing as disclosed herein, namely, Equation 3:

Ts=EQUATION⁢3Tout+Tin2+(CP·m.(Tout+Tin)As)KD⁢{C2·C·Pr0.36(PrPrs)0.25[Dμ⁢(STST-D)⁢(Min+MfuelAc)]m}where:Ac=heater cross-sectional area;As=sheath area;C=constant based on Reynolds number (Re) and Table 1;C2=offset based on number of heater elements;Cp=specific heat of air at constant pressure;D=heater element diameter;K=thermal conductivity of air;Mfuel=mass flow rate of fuel;Min=inlet mass air flow (MAF) rate;m=constant based on Reynolds number (Re) and Table 1;{dot over (m)}=mass flow rate;Pr=Prandtl number of air taken at gas temperature;Prs=Prandtl number of air taken at sheath temperature;ST=transverse distance between elements;Tin=heater inlet temperature;Tout=heater outlet temperature; andμ=viscosity of air.

Generally, so as to not be limited to the specific equations disclosed herein, Tsis determined by a system of equations using inputs of set point, mass flow, and inlet temperature to calculate system temperatures.

The present disclosure further provides for predictive/proactive control of the heater40. For example, system data such as torque demand, pedal position, and increased manifold absolute pressure (MAP)/boost/engine timing can be converted into a mass flow rate, which can then be provided to the control system to determine desired heater power in advance of when the power is needed, rather than relying on a delayed response to a physical sensor.

One variation of the present disclosure takes into account radiation effects according to Equation 4:

Q=ε·σ·vf(Th+Tse)EQUATION⁢4where:Q=radiation density;Th=absolute heater temperature;Tse=absolute sensor temperature;Vf=view factor (portion of heater radiation that strikes sensor);ε=emissivity; andσ=Stefan-Boltzmann constant.

Furthermore, the heater can be fully mathematically quantified such that the system frequency response of all materials comprising the heater can be determined from mass air flow (MAF) rate, heater inlet temperature, and applied power. The frequency response of the heater to changing engine and exhaust conditions or general system disruptions can be reduced, allowing the heater to have a faster feedback response. This then improves control over heater element temperature, allowing the heater to have a higher watt density (watts per unit length, watts per unit area, or watts per unit volume) and better durability, as temperature fluctuations are reduced. System representations can be simplified into a form the control microprocessor can utilize with reduced effort. Further, the present disclosure can simplify a relatively complex math process into tabulated form to reduce processing power and defined expected states. It should be understood that a variety of methods of obtaining mass air flow may be employed, such as by way of example, MAP and combining inlet air mass flow with fuel consumption. Accordingly, as used herein, the term “mass flow” shall be construed to include these and other methods of obtaining mass air flow.

Generally, the present disclosure takes inputs from a variety of devices, such as by way of example, engine, exhaust, electrical power, and heater, executes various algorithms, and then generates output such as actual power consumption, exhaust temperature, heater temperature, diagnostics, and exhaust mass flow. The engine inputs/parameters may include exhaust temperature and exhaust flow; and the heater inputs/parameters may include heater power, geometry, and coefficients. The system model may include a heater model, wire temperature and sheath temperature, and at least one control algorithm. The outputs may then include exhaust temperature, exhaust flow, and diagnostics.

In still another form, the virtual sensing system functions in a diagnostic mode to compare a response of the heater40to a known applied power to determine if the overall exhaust aftertreatment system18is degrading, has reduced efficiency, or if there is a defect in the exhaust aftertreatment system18. In addition, the virtual sensing system may allow for the removal of a catalyst inlet temperature sensor, thus reducing the cost and complexity of the overall exhaust aftertreatment system18. If the catalyst inlet temperature sensor remains in the exhaust aftertreatment system18, its output can be compared to the calculated/predicted heater outlet temperature provided by the virtual sensing system and any mismatch therebetween can trigger a diagnostic trouble code within an engine control unit (ECU). Furthermore, the virtual sensor system of the present disclosure can be integrated with a model-based design (e.g., Simulink) to improve transient performance and allow better characterization of the heater system. Furthermore, a model-based design can adjust parameters/characterization of the virtual sensor system based on a specific application other than the diesel exhaust application as used herein.

The use of a virtual sensor system further reduces the uncertainty of knowing the actual resistive element (e.g., wire) temperature and allows safety margins to be reduced, increased watt density and less heater surface area, thus resulting in a more efficient and less costly heater.

The control system as disclosed herein may also control power to the heater by a calculated, or virtual temperature of the resistive heating element, such as a resistive wire. Reference is made to copending application titled “Advanced Two-Wire Heater System for Transient Systems,” which has been incorporated herein by reference. In some applications such as a tubular heater, controlling by virtual wire temperature overcomes the thermal inertia of the insulation and sheath. This results in less temperature variation on the wire, which improves reliability. Such an approach also reduces the cyclic load on a power source, allowing for smoother power delivery and less strain on the power source.

The present disclosure further provides for an engine system10including a control system for the heating system of the exhaust system as previously described. The control device is adapted to receive engine inputs selected from the group consisting of engine parameters, exhaust parameters, electrical power output, heater parameters, and the device is operable to generate output selected from the group consisting of power consumption, exhaust temperature, heater temperature, diagnostics, exhaust mass flow rate, and combinations thereof. The control system is further operable to diagnose degrading engine system components. In this example, the control system is in communication with an engine control unit and adapted to trigger a diagnostic trouble code when a determined parameter is mismatched with a preset parameter.

Referring toFIG.4, the present disclosure further includes a method100of predicting temperature of at least one location in a fluid flow system having a heater disposed in a heating system for heating fluid. The method includes obtaining a mass flow rate of fluid flow of the fluid flow system110, obtaining at least one of a fluid outlet temperature and a fluid inlet temperature of the heater120, obtaining power provided to the heater130, and calculating temperature at the at least one location based on a model of the fluid flow system and the obtained mass flow rate and fluid outlet and inlet temperatures140. The at least one location can be on a heating element of the at least one electric heater of the heating assembly. The model can include the temperature prediction models as previously described above. The process can further be integrated with a model-based design.

Referring toFIG.5, the present disclosure further provides another method200of predicting outlet temperature after each of a plurality of resistive heating elements in a heater system disposed in a fluid flow system for heating fluid. The method includes obtaining a mass flow rate of fluid flow of the fluid flow system210, obtaining a fluid inlet temperature to at least one resistive heating element220, obtaining power provided to each resistive heating element and characteristics of the fluid flow system that relate power input to each resistive heating element to power transferred to the fluid flow230, and calculating the outlet temperature based on a model of the fluid flow system240.

As used herein, the term “model” should be construed to mean an equation or set of equations, a tabulation of values representing the value of a parameter at various operating conditions, an algorithm, a computer program or a set of computer instructions, a signal conditioning device or any other device that modifies the controlled variable (e.g., power to the heater) based on predicted/projected/future conditions, wherein the prediction/projection is based on a combination of a priori and in-situ measurements.

Accordingly, a variety of different forms of heaters, sensors, control systems, and related devices and methods have been disclosed herein for use in fluid flow systems. Many of the different forms can be combined with each other and may also include additional features specific to the data, equations, and configurations as set forth herein. Such variations should be construed as falling within the scope of the present disclosure.

The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.