Patent Publication Number: US-8968666-B2

Title: Electrically heated catalyst with waste heat recovery

Description:
FIELD 
     The present disclosure relates to waste heat recovery systems, and more specifically to waste heat recovery systems as applied to exhaust systems of a vehicle. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     A waste heat recovery system may be applied to an exhaust system of a vehicle to recover energy that would be otherwise emitted from the exhaust system. The waste heat recovery system may convert thermal energy obtained from the exhaust system to electrical energy, which may then be used operate electrical components and/or motor(s) of the vehicle. 
     A waste heat recovery system may include, for example, a heat exchanger or coil in which a coolant passes. The coil may be located within and receive thermal energy from an exhaust system. The coolant is then passed through an expander, where thermal energy within the coolant may be converted to mechanical energy. The coolant is then pumped through and further cooled by a condenser prior to again being cycled through the heat exchanger. 
     In addition to having the heat exchanger, the exhaust system may also include a catalytic converter. The catalytic converter may be located, for example, upstream from the heat exchanger and be used to reduce emissions of an internal combustion engine (ICE). For example, a three-way catalytic converter reduces nitrogen oxide, carbon monoxide and hydrocarbons within an exhaust system. The three-way catalytic converter converts nitrogen oxide to nitrogen and oxygen, converts carbon monoxide to carbon dioxide, and oxidizes unburnt hydrocarbons (HC) to produce carbon dioxide and water. 
     An average catalyst light-off temperature at which a catalytic converter typically begins to function is approximately 200-350° C. As a result, a catalytic converter does not function or provides minimal emission reduction during a warm up period that occurs upon a cold startup of the ICE. Exhaust system temperatures are less than the catalyst light-off temperature during an engine cold start. During the warm up period, HC emissions may not be effectively processed by the catalytic converter. 
     SUMMARY 
     A catalytic converter is provided and includes an inlet end, an outlet end and a catalyst body. The inlet end is configured to receive an exhaust gas from an engine. An outlet end is configured to output the exhaust gas. A catalyst body includes partitioning members disposed between the inlet end and the outlet end. The catalyst body includes exhaust channels and fluid channels. The exhaust channels are configured to guide the exhaust gas from the inlet end to the outlet end. The fluid channels are configured to receive a fluid from and return the fluid to a waste heat recovery circuit. Each of the exhaust channels and each of the fluid channels includes respective ones of the partitioning members. 
     In other features, a catalytic converter is provided and includes an inlet end, an outlet end, a catalyst body and electrodes. The inlet end is configured to receive an exhaust gas from an engine. The outlet end is configured to output the exhaust gas. The catalyst body is disposed between the inlet end and the outlet end. The catalyst body includes exhaust channels and fluid channels. The exhaust channels are configured to guide the exhaust gas from the inlet end to the outlet end. The fluid channels are configured to receive a fluid from and return the fluid to a waste heat recovery circuit. The electrodes are connected to the catalyst body and pass current through the catalyst body. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of an engine system incorporating a waste heat recovery system in accordance with the preset disclosure; 
         FIG. 2  is a functional block diagram illustrating a side view of an electrically heated catalytic converter in accordance with the preset disclosure; 
         FIG. 3  is a functional block diagram illustrating an end view of the electrically heated catalytic converter of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of a portion of a catalyst body of the electrically heated catalytic converter of  FIG. 2 ; 
         FIG. 5  is a perspective view of a manifold in accordance with the preset disclosure; 
         FIG. 6  is a recovery efficiency versus temperature plot; 
         FIG. 7  is a functional block diagram of an engine control module incorporating a thermal control module in accordance with the present disclosure; and 
         FIG. 8  illustrates a method of operating a waste heat recovery system in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , an engine system  10  is shown. The engine system  10  includes an internal combustion engine (ICE)  12 , an exhaust system  14 , a waste heat recovery (WHR) system  16 , and an engine control module (ECM)  18 . The exhaust system  14  includes a WHR catalytic converter (CC)  20  and may include a secondary CC  22 . The WHR CC  20  may be, for example, a three-way CC and includes a catalyst body  24  configured for WHR. If the secondary CC  22  is included, the WHR CC  20  may be referred to as a close coupled catalyst and the secondary CC  22  may be referred to as an underfloor catalyst. The WHR CC  20  may be connected at various locations along the exhaust system  14 . 
     Although the engine system  10  is shown as a gasoline engine system having a spark ignition engine (the ICE  12 ), the engine system  10  is provided as an example. The WHR system  16  may be implemented on various other engine systems including diesel engine systems. The engine system  10  may be an alcohol-based engine system, such as a methanol, ethanol, and/or E85 based engine system. 
     The ICE  12  combusts an air and fuel mixture to produce drive torque. Air enters the ICE  12  by passing through an air filter  25 . Air passes through the air filter  25  and may be drawn into a turbocharger  26 . The  26  when included compresses the fresh air. The greater the compression, the greater the output of the ICE  12 . The compressed air may pass through an air cooler (not shown) before entering an intake manifold  28 . 
     Air within the intake manifold  28  is distributed into cylinders  30 . Fuel is injected into the cylinders  30  by fuel injectors  32 . Spark plugs  34  ignite air/fuel mixtures in the cylinders  30 . Combustion of the air/fuel mixtures creates exhaust. The exhaust exits the cylinders  30  into the exhaust system  14 . 
     The exhaust system  14  includes the WHR CC  20 , the ECM  18 , an exhaust manifold  36 , and may include an air pump (not shown). As an example, the catalyst body of the WHR CC  20  and the secondary CC  22  may each include a three-way catalyst (TWC). The TWCs may reduce nitrogen oxides NOx, oxidize carbon monoxide (CO) and oxidize unburnt hydrocarbons (HC) and volatile organic compounds. The TWCs oxidize the exhaust based on a post combustion air/fuel ratio. The amount of oxidation increases the temperature of the exhaust. The ECM  18  includes a thermal control module  40 , which controls temperatures of the exhaust system  14  and operation of the WHR system  16 . 
     Optionally, an EGR valve (not shown) re-circulates a portion of the exhaust back into the intake manifold  28 . The remainder of the exhaust is directed into the turbocharger  26  to drive a turbine. The turbine facilitates the compression of the fresh air received from the air filter  25 . Exhaust flows from the turbocharger  26  to the WHR CC  20 . 
     The engine system  10  may be a hybrid electric vehicle system and include a hybrid control module (HCM)  42  and one or more electric motor(s)  44 . The HCM  42  may be part of the ECM  18  or may be a stand-alone control module, as shown. The HCM  42  controls operation of the electric motor(s)  44 . The electric motor(s)  44  may supplement and/or replace power output of the ICE  12 . The electric motor(s)  44  may be used to adjust speed of the ICE  12  (i.e. rotating speed of a crankshaft  46  of the ICE  12 ). The electric motor(s)  44  may be connected to the ICE  12  via a belt/pulley system, via a transmission, one or more clutches, and/or via other mechanical connecting devices. The ECM  18  and/or HCM  42  may control operation of the electric motor(s)  44  and/or a starter  48  to rotate the crankshaft  46 . 
     The WHR system  16  includes a WHR circuit  50  that includes the WHR CC  20 , an expander  52 , a condenser  54 , a WHR pump  56 , and a valve  58 . Fluid lines  60  (e.g., hoses) are connected between the WHR CC  20 , the expander  52 , the condenser  54 , the WHR pump  56 , and the valve  58 . A fluid is circulated in the WHR circuit  50  via the WHR pump  56 , which directs the fluid from the condenser  54  through the valve  58  and to the WHR CC  20 , the fluid is then directed to the expander  52  and back to the condenser  54 . The fluid may be a coolant (e.g., hydrocarbon refrigerant). The fluid may include, for example, Butane, Pentane and/or other suitable fluid. The fluid may not be a conductive fluid, such as water (H 2 0) or ethanol to prevent electrical current passing from the WHR CC  20  to other components of the engine system  10  and/or a corresponding vehicle. The fluid from the expander  52  may be in a gaseous state when received by the condenser  54  and be in a liquid state when exiting the condenser  54 . 
     The fluid is used to transfer thermal energy from the WHR CC  20  to the expander  52 , where the thermal energy may be converted to mechanical energy and then later converted to electrical energy. The mechanical energy from the expander  52  may be supplied to, for example, the electric motor(s)  44 . The electrical energy may be supplied to a valvetrain of the ICE  12 , a power supply, and/or to other electrical components in the engine system  10  and/or in the vehicle. The expander  52  may include a motor, which converts the thermal energy of a pressurized fluid to a mechanical output torque {dot over (ω)}. The output torque {dot over (ω)} may be provided to, for example, an engine, a generator, or a starter. 
     The ECM  18  and/or the thermal control module  40  may control operation of the WHR system  16  via the WHR pump  56  and the valve  58 . Fluid may be permitted to circulate and/or prevented from circulating in the WHR circuit  50  by powering ON and OFF the WHR pump  56  and/or by controlling an OPEN or CLOSED state of the valve  58 . The rate and/or pressure at which the fluid circulates through the WHR circuit  50  may also be controlled by adjusting speed of the WHR pump  56  and/or opening of the valve  58 . 
     The WHR CC  20  includes the catalyst body  24 , which may be electrically-heated in certain conditions, as described below. Current may be supplied to the WHR CC  20  from a power source  62 . The supply of current to the WHR CC  20  is controlled by the ECM  18  and/or thermal control module  40 . The catalyst body  24  is configured to receive the exhaust gas from the exhaust system  14  and to receive the fluid passing through the WHR circuit  50 . This is described further below. 
     The ECM  18 , the thermal control module  40 , and/or the HCM  42  control the ICE  12 , the WHR system  16 , the electric motor(s)  44 , the starter  48  and current supplied to the catalyst body  24  based on sensor information. The sensor information may be obtained directly via sensors and/or indirectly via algorithms and tables stored in memory  70 . Some example sensors  80  for determining exhaust flow levels, exhaust temperature levels, exhaust pressure levels, catalyst temperatures, oxygen levels, intake air flow rates, intake air pressure, intake air temperature, vehicle speed, engine speed, EGR, etc. are shown. Exhaust flow sensors  82 , exhaust temperature sensors  83 , exhaust pressure sensors  85 , catalyst temperature sensors  86 , oxygen sensors  88 , an EGR sensor  90 , an intake air flow sensor  92 , an intake air pressure sensor  94 , an intake air temperature sensor  96 , vehicle speed sensor  98  and an engine speed sensor  99  are shown. The thermal control module  40  may control operation of the WHR pump  56 , the valve  58 , the power source  62 , the expander  52  and/or other components of the WHR system  16  based on the information from the sensors  80 . 
     In  FIGS. 2-4 , side and end views of the WHR CC  20  and a cross-sectional view of the catalyst body  24  are shown. The WHR CC  20  includes the catalyst body  24  (or substrate  24 ), electrodes  100 ,  102 , a WHR manifold  104 , and may include an insulator  106 . The substrate  24  is formed of a thermally and electrically conductive material, such as siliconized-silicon carbide (Si—SiC), a ceramic composite material, and/or other suitable material(s). This allows thermal energy to pass from the exhaust gas and/or the substrate  24  to the fluid and also permits electrical heating of the substrate  24 . The substrate  24  may have a resistance and/or impedance that is less than a first predetermined resistance and/or impedance and greater than a second predetermined resistance and/or impedance. The first predetermined resistance and/or impedance is set to allow a predetermined amount of current to flow through and heat the substrate  24 . The first predetermined resistance and/or impedance may be set to direct a high or predetermined percentage of the current supplied to the first electrode  100  to pass through the substrate  24  and the fluid and to the second electrode  102 . The second predetermined resistance and/or impedance is set to prevent a short between the electrodes  100 ,  102  and/or to limit the amount of current flowing through the substrate  24 . 
     Heating of the substrate  24  heats the exhaust gas and the fluid passing through the substrate  24 . The electrodes  100 ,  102  are connected to a catalyst heating system  110 , which may include the ECM  18 , the power source  62  and a switch  112 . The power source  62  may be a high-voltage power source, for example, having an output voltage of greater than or equal to 100V. The substrate  24  is electrically heated via the electrodes  100 ,  102 . Current is supplied from the power source  62  via the switch  112  to the first electrode  100 . The current passes through the substrate  24  to the second electrode  102  and heats the substrate  24  to a temperature greater than or equal to a light-off temperature. 
     The substrate  24  may include, for example, a TWC deposited on the substrate  24 . The TWC may include catalyst metals, such as platinum, rhodium, palladium, and/or other catalyst metals. The catalyst metals may be sparsely located across surface areas of the substrate  24  and may be, for example, embedded into an alumina washcoat of the substrate  24 . The washcoat may be non-conductive and/or have a high-resistance and/or high-impedance as to minimize electrical current flow in the washcoat. 
     The substrate  24  may have a honeycomb configuration with partitioning members  114  that form walls of exhaust channels  116  and fluid channels  118  included in the substrate  24 . The exhaust channels  116  and fluid channels  118  extend parallel to each other between an inlet end  120  and an outlet end  122  of the substrate  24 . The exhaust channels  116  allow the exhaust gas from the ICE  12  to pass from the inlet end  120  to the outlet end  122 . 
     The fluid channels  118  may include receive and return channel pairs. Each of the channel pairs includes a receive channel  124  and a return channel  126 . The receive channel  124  and the return channel  126  may be connected to each other and/or be formed together as a single channel. The channel pairs extend along the substrate  124  from the inlet end  120  to the outlet end  122  to efficiently absorb thermal energy from the substrate  24 . 
     Each of the receive channels has a first end  130  and a second end  132 . The first end  130  may be at the outlet end  122  of the substrate  24  and receive the fluid from the WHR manifold  104 . The second end  132  may be at the inlet end  120  of the substrate  24  and may be blocked from receiving the exhaust gas by an end plug  134 . 
     The return channel  126  may include a first end  136  and a second end  138 . The first end  136  may be at the inlet end  120  of the substrate  24  and may also be blocked from receiving the exhaust gas via the end plug  134 . The end plug  134  may be inserted into the receive channel  124  and the return channel  126  at the inlet end  120  of the substrate  24 . A single end plug may be included for each channel pair. The fluid flows in the return channel  126  in an opposite direction than in the receive channel  124 . 
     The end plugs are on an opposite end of the substrate  24  as the WHR manifold  104 . Although the end plugs are shown at the inlet end  120  and the WHR manifold  104  is shown at the outlet end  122 , the end plugs may be at the outlet end  122  and the WHR manifold  104  may be at the inlet end  120 . The second end  138  may be at the outlet end  122  of the substrate  24  and return the fluid received by the receive channel  124  back to the WHR manifold  104 . 
     Each member (e.g., the member  140 ) of the substrate  124  that is located between a receive channel and a return channel of the channel pairs may not extend fully to the inlet end  120 . These members may be shorter in length than other members of the substrate  24  that extend fully from the inlet end  120  to the outlet end  122 . This allows the fluid to pass from the receive channel to the return channel across a respective end plug (e.g., the end plug  134 ). 
     Referring now also to  FIG. 5 , the WHR manifold  104  is shown. The WHR manifold  104  may include exhaust channels (not shown), fluid (receive and return) channels  152 ,  154 , channel couplers  155 , fluid connectors  156 ,  158 , etc. Although the exhaust channels of the WHR manifold  104  are not shown in  FIG. 5 , the exhaust channels are similar to the exhaust channels  116  of the substrate  24 . The WHR manifold  104  receives the fluid from the WHR circuit  150  and/or valve  58  of  FIG. 1  via the first fluid (or receive) connector  156  and directs the fluid from the first fluid connector  156  to the receive channels  152 . The first fluid connector  156  is connected to the WHR circuit  150 . The receive channels  152  then direct the fluid to the receive channels (e.g., the receive channel  124 ) of the substrate  24 . The receive channels  152  may include (i) an intake manifold  160  with an input that is connected to the first fluid connector  156  and (ii) multiple outputs connected to respective ones of the receive channels  152 . 
     The fluid then passes from the receive channels of the substrate  24  through the return channels (e.g., the return channel  126 ) of the substrate  24  and into the return channels  154 . The fluid is directed from the return channels  154  to the second fluid connector  158  (return connector) after which the fluid is directed to the expander  52  of  FIG. 1 . The return channels  154  may include (i) an output manifold  164  that includes multiple inputs connected to respective ones of the return channels  154  and (ii) an output connected to the second fluid connector  158 . The second fluid connector  158  is connected to the WHR circuit  150 . 
     The channel couplers  155  may be located between the channels of the WHR manifold  104  and the channels (e.g., channels  116 ,  118 ) of the substrate  24  depending on the configurations of the substrate  24  and the WHR manifold  104 . The channel couplers  155  may be non-conductive and recessed within the WHR manifold  104  and/or the substrate  24 . The channel couplers  155  may prevent electrical current from passing between (i) the substrate  24  and/or channels of the substrate  24  and (ii) the channels  152 ,  154 . In one implementation, the channel couplers  155  are not included and the channels of the substrate  24  abut the channels  152 ,  154 . In this implementation the channels of the substrate  24  may directly receive the fluid from and directly return the fluid to the channels of the WHR manifold  104 . In another implementation, the channel couplers are included to isolate the WHR manifold  104  from the conductive materials of the substrate  24 . 
     The WHR manifold  104  may include a manifold body  166  that includes the exhaust channels (not shown in  FIG. 5 ) and the fluid channels  152 ,  154 . The manifold body  166  may have a honeycomb structure similar to that of the substrate  24 . This allows the exhaust and fluid channels of the WHR manifold  104  to be aligned with respective channels of the substrate  24 . In one implementation, the manifold body  166  is formed of a non-conductive material(s), such as cordierite, to prevent electrical current passing from the substrate  24  to the WHR manifold  104  and/or other components of the engine system  10 . A TWC may be deposited on the manifold body  166  or the manifold body  166  may perform as a pass through device (i.e. the exhaust gas is not oxidized, treated, and/or chemically changed in the manifold body  166 ). In one implementation, the manifold body  166  is formed of a conductive material, such as Si—SiC, and is separated from the substrate  24  via the insulator  106  or other suitable current insulating device(s). 
     The insulator  106  may be included between the substrate  24  and the WHR manifold  104  to prevent passage of current from the electrodes  100 ,  102  to the WHR manifold  104  via the substrate  24  and/or channels of the substrate  24 . The insulator  106  may be included to electrically isolate the WHR manifold  104 , channels  152 ,  154 , and/or connectors  156 ,  158  from the substrate  24 . Inclusion of the insulator  106  depends on the configurations of the substrate  24  and the WHR manifold  104 . For example, if the substrate  24  and the WHR manifold  104  are formed of conductive materials, the insulator  106  may be included. If the manifold body  166  is formed of non-conductive materials, the insulator  106  may not be included. 
     The insulator  106  may have a honeycomb structure and include channels extending between the respective channels of the substrate  24  and respective channels of the WHR manifold  104 . The insulator  106  is formed of non-conductive material(s), which may include cordierite. 
     The substrate  24 , the manifold body  166 , the insulator  106 , and/or channel couplers  155  may have similar expansion and contraction properties to exhibit similar changes during heating and cooling transitions. This allows the channels of each of the substrate  24 , the manifold body  166 , and the insulator  106  to remain in alignment with each other. Alignment between (i) the channels of the substrate  24 , the manifold body  166 , and the insulator  106  and (ii) the channel couplers  155  is also maintained. By having similar expansion and contraction properties, cracking is prevented in the substrate  24 , the manifold body  166 , the insulator  106 , and/or channel couplers  155 . The substrate  24 , the manifold body  166 , the insulator  106 , and/or the channel couplers  155  may be adhered to each other using an adhesive. The insulator  106  and/or adhesive may be formed of a flexible material to: maintain alignment of the channels of the substrate  24 , the manifold body  166 , the insulator  106 , and/or channel couplers  155 ; prevent cracking; and maintain integrity and continuity of the fluid channels from the inlet end  120  to the connectors  156 ,  158 . 
     As another technique to prevent current from passing from the electrodes  100 ,  102  through the substrate  24  and the WHR manifold  104  to other components of the WHR circuit  150 , the connectors  156 ,  158  may be non-conductive and/or include insulators and/or current isolators. This electrically separates the catalyst heating system  110  from components of the WHR circuit  150  and/or other components of the engine system  10  and/or vehicle. 
     By using the substrate  24  of the WHR CC  20  to recover thermal energy from the exhaust system  14 , a high percentage of energy in the exhaust system  14  is recoverable. Forming the substrate  24  of Si—SiC and/or other similar material(s) provides an efficient heat source for the transfer of thermal energy. 
     In  FIG. 6 , a recovery efficiency versus temperature plot is shown. The higher the temperature of the heat source, the higher the grade of the heat source and the more efficient the waste heat recovery system. Higher substrate temperatures yield higher WHR efficiencies. The maximum efficiency Eff max  of a heat source may be determined, for example, using equation 1, where T amb  is ambient temperature and T s  is source temperature or temperature of the substrate  24 . 
                     Eff   max     =     1   -       T   amb       T   s                 (   1   )               
Waste heat recovery may be measured as an amount of energy Q recovered using, for example, equation 2, where m is mass of the substrate  24  including particulate, exhaust and/or fluid in the substrate  24 , c the specific heat of the substrate  24 , and ΔT is the change in temperature of the substrate  24  over a period in which the energy Q is recovered. The specific heat c of the substrate  24  may be, for example, 880 Joules/Kilogram (kg)·1° Kelvin (K) (or J/kgK).
 
 Q=m·c·ΔT   (2)
 
     As an example, as low as 10% of thermal energy in a catalyst body may be converted back to electrical energy at low temperatures (temperatures less than 100° C.). As high as 80% of thermal energy in a catalyst body may be converted back to electrical energy at high temperatures (temperatures greater than 600° C.). 
     By incorporating WHR channels (the channels of the substrate  24 ) in the WHR CC  20 , improved exhaust packaging is provided in comparison to traditional exhaust systems on which WHR techniques have been applied. A separate heat exchanger, for example, downstream of a TWC is not needed. 
     Referring again to  FIGS. 2 and 3 , the catalyst heating system  110  assists light-off of the catalyst on the substrate  24  during, for example, cold starts. Since the substrate  24  includes fluid channels and corresponding fluid flowing therein, mass of the substrate  24  is increased over a catalyst body without fluid channels. The catalyst heating system  110  accounts for the increased mass and quickly increases the temperature of the substrate  24  and the catalyst up to the light-off temperature by passing an electrical current between the electrodes  100 ,  102  and through the substrate  24  and the fluid in the substrate  24 . 
     The electrodes  100 ,  102  may be connected to opposite exterior sides  170 ,  172  of the substrate  24  and may be shaped similar to the substrate  24  to extend over a predetermined exterior surface area of the substrate  24 . Although the electrodes  100 ,  102  are shown as being exterior to the substrate  24 , the electrodes  100 ,  102  may be mounted within the substrate  24 . The electrodes  100 ,  102  may each have a cross-sectional area that is semi-circular in shape, as shown. By electrically heating the substrate  24 , the increased mass of the substrate  24  is overcome and emissions are minimized. The catalyst heating system  110  may be used to provide an exhaust system that satisfies partial zero emissions vehicle (PZEV) requirements. A PZEV has zero evaporative emissions. 
     Referring now also to  FIG. 7 , the ECM  18  is shown. The ECM  18  includes the thermal control module  40  and may also include a vehicle speed module  180  and an engine speed module  182 . The vehicle speed module  180  determines speed of a vehicle based on information from, for example, the vehicle speed sensor  98  and generates a vehicle speed signal S VEH  ( 200 ). The engine speed module  182  determines speed of the ICE  12  based on information from, for example, the engine speed sensor  99  and generates an engine speed signal S ENG  ( 202 ). 
     The thermal control module  40  includes an engine monitoring module  184 , a catalyst monitoring module  186 , a first comparison module  188 , a second comparison module  190 , a mode selection module  192 , a temperature module  194 , and a WHR module  196 . The thermal control module  40  operates in electrical heating and WHR modes. During the electrical heating mode, current is supplied to the electrodes  100 ,  102  and flow of the fluid in the WHR circuit  150  is restricted and/or prevented. During the WHR mode, the fluid is permitted to circulate through the WHR circuit  150 . This flow may be unrestricted and/or increased over the flow of the fluid during the electrical heating mode. 
     The WHR system  16  of  FIG. 1  may be operated using numerous methods, an example method is provided by the method of  FIG. 8 . In  FIG. 8 , a method of operating the WHR system  16  is shown. Although the following tasks are primarily described with respect to the implementations of  FIGS. 1-5  and  7 , the tasks may be easily modified to apply to other implementations of the present disclosure. The tasks may be iteratively performed. The method may begin at  300 . 
     At  302 , sensor signals are generated. The sensor signals may include exhaust flow signals, exhaust temperature signals, exhaust pressure signals, catalyst temperature signals, an oxygen signal, an intake air flow signal, an intake air pressure signal, an intake air temperature signal, a vehicle speed signal, an engine speed signal, an EGR signal, etc., which may be generated by the above-described sensors  80  and  104 - 110  of  FIG. 1 . 
     At  304 , the thermal control module  40  and/or the engine monitoring module  184  determines states of the ICE  12 . The engine monitoring module  184  may generate an engine monitoring signal Engine ( 203 ) based on the engine speed signal S ENG , a fuel supply signal FUEL ( 204 ) and/or an ignition enable signal SPARK ( 206 ). The engine monitoring signal Engine indicates state of the ICE  12  including whether the engine is ON or OFF, whether fuel and/or spark are enabled, and/or speed of the ICE  12 . The thermal control module  40  may proceed to  206  when the engine is ON. 
     At  306 , the thermal control module  40  determines whether temperature T CAT  ( 208 ) of the substrate  24  and/or active volume PV ACTIVE  ( 210 ) of the substrate  24  is less than predetermined value(s). The catalyst monitoring module  186  may estimate the temperature T CAT  of the substrate  24  and/or the active volume PV ACTIVE  using a thermal model and based on engine parameters and/or exhaust temperatures, some of which are described below with respect to equations 3 and 4. Although a thermal model is provided below, other suitable thermal model(s), table(s) and/or equation (s) may be used to estimate the temperature T CAT  and/or the active volume PV ACTIVE . Also, depending upon the sophistication of the thermal control module  40  and corresponding system, one or more of the parameters used in equations 3 and 4 may not be included in determining the temperature T CAT  of the substrate  24 . 
     The catalyst monitoring module  186  may directly determine the temperature of the substrate  24  via a temperature sensor of the substrate  24  and/or estimate the temperature T CAT  based on ICE parameters ENGPARS ( 212 ) and exhaust system parameters EXHPARS ( 214 ). The thermal model may include equations, such as equations 3 and 4, which include example ICE parameters and exhaust system parameters. 
     
       
         
           
             
               
                 
                   
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                                 AMB 
                               
                               , 
                               CAM 
                               , 
                               SPK 
                             
                           
                         
                       
                       } 
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     F Rate  is exhaust flow rate through the WHR CC  20 , which may be a function of mass air flow and fuel quantity supplied to the cylinders  30 . The mass air flow may be determined by a mass air flow sensor, such as the intake air flow sensor  92 . S ENG  is speed of the ICE  12  (i.e. rotational speed of the crankshaft  46 ). DC is duty cycle of the ICE  12 . C Mass  is mass of the substrate  24 . C IMP  is resistance or impedance of the substrate  24 . The values C Mass  and C IMP  may account for mass, resistance and/or impedance of the fluid in the substrate  24 . E RunTime  is time that the ICE  12  is activated (ON). E Load  is current load on the ICE  12 . T EXH  may refer to a temperature of the exhaust system  14 , and based on one or more of the temperature sensors  104 - 110 . T amb  is ambient temperature. CAM is cam phasing of the CIE. SPK is spark timing. The temperature signals and the active catalyst volume signal PV ACTIVE  may be based on one or more of the engine system parameters provided in equations 3 and 4 and/or other engine system parameters, such as mass C MASS  of the substrate  24 . 
     The first comparison module  188  may generate a first comparison signal COMP 1  ( 216 ) based on the temperature T CAT  and a catalyst light-off temperature T CLO  ( 217 ) (e.g., 250° C.). The second comparison module  190  may generate a second comparison signal COMP 2  ( 218 ) based on the active catalyst volume PV ACTIVE  and a first predetermined active catalyst volume PV PRED1  ( 220 ). The predetermined active catalyst volume PV PRED1  may be, for example, 30-40% of the volume of the substrate  24 . The mode selection module  192  generates a mode signal MODE ( 222 ) based on the first and second comparison signals COMP 1 , COMP 2 , the engine monitoring signal Engine, the speed of the vehicle S VEH  and/or the engine speed S ENG . 
     The thermal control module  40  and/or the mode selection module  192  may proceed to  308  when one or both of the comparison signals COMP 1 , COMP 2  is, for example, LOW, otherwise the thermal control module  40  may proceed to task  311 . This indicates that temperature of the substrate  24  is less than the light-off temperature or a predetermined temperature and/or the active volume of the substrate  24  is less than a predetermined volume. 
     At  308 , the catalyst heating system  110  electrically heats the substrate  24 . The thermal control module  40  and/or the temperature module  194  generates a power signal POW ( 224 ), which may be provided to the power source  62  and/or the switch  112  to control current supplied to the electrodes  100 ,  102 . 
     At  310 , the thermal control module  40  and/or the WHR module  196  restricts and/or prevents the fluid to flow through the WHR circuit  150  including the fluid channels of the substrate  24 . The WHR module  196  may generate signals PUMP ( 226 ), VALVE ( 228 ) to control speed of the WHR pump  56  and/or state of the valve  58 . The thermal control module  40  may return to task  202  subsequent to task  310 . 
     At  311 , the thermal control module  40  determines whether temperature T CAT  of the substrate  24  and/or active volume PV ACTIVE  of the substrate  24  is greater than predetermined value(s). The catalyst monitoring module  186  may estimate the temperature T CAT  of the substrate  24  and/or the active volume PV ACTIVE  using the thermal model of equations 3 and 4 or other suitable thermal model(s), table(s) and/or equation (s). The first comparison module  188  may generate the first comparison signal COMP 1  based on the temperature T CAT  and a predetermined temperature T PRED  ( 230 ). The predetermined temperature may be greater than or equal to the light-off temperature T CLO . The second comparison module  190  may generate the second comparison signal COMP 2  based on the active catalyst volume PV ACTIVE  and a second predetermined active catalyst volume PV PRED2  ( 232 ). The second predetermined active catalyst volume PV PRED2  may be greater than or equal to the first predetermined active catalyst volume PV PRED1 . 
     The thermal control module  40  and/or the mode selection module  192  may proceed to  312  when one or both of the comparison signals COMP 1 , COMP 2  is, for example, HIGH, otherwise the thermal control module  40  may return to task  302 . 
     In one implementation, task  311  is not performed and task  312  is performed subsequent to task  310 . At  312 , the thermal control module  40  and/or the temperature module  194  deactivates the catalyst heating system  110 . This may include, for example, switching OFF the switch  112  and/or preventing electrical current to be supplied to the electrodes  100 ,  102 . 
     At  314 , the WHR module  196  permits the fluid to circulate through the WHR circuit  150  including the fluid channels of the substrate  24 . This fluid flow may not be restricted. The WHR module  196  adjusts the signals PUMP, VALVE to control the flow rate and pressure of the fluid circulating through the WHR circuit  150 . The WHR module  196  may adjust the signals to adjust the fluid flow rate and pressure based on the temperature T CAT . The thermal control module  40  may return to task  302  subsequent to task  314 . 
     The above-described tasks are meant to be illustrative examples; the tasks may be performed sequentially, synchronously, simultaneously, continuously, during overlapping time periods or in a different order depending upon the application. Also, any of the tasks may not be performed or skipped depending on the implementation and/or sequence of events. 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. 
     As used herein, the term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term module may include memory (shared, dedicated, or group) that stores code executed by the processor. 
     The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared, as used above, means that some or all code from multiple modules may be executed using a single (shared) processor. In addition, some or all code from multiple modules may be stored by a single (shared) memory. The term group, as used above, means that some or all code from a single module may be executed using a group of processors. In addition, some or all code from a single module may be stored using a group of memories. 
     The apparatuses and methods described herein may be implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on a non-transitory tangible computer readable medium. The computer programs may also include stored data. Non-limiting examples of the non-transitory tangible computer readable medium are nonvolatile memory, magnetic storage, and optical storage.