Exhaust burner control for reducing fuel consumption

Abstract

An exhaust control system for a vehicle includes at least one temperature sensor positioned within an exhaust system of the vehicle, the at least one temperature sensor configured to generate a measurement signal indicative of at least one of an inlet temperature and an outlet temperature of a diesel oxidation catalyst (DOC). An exhaust control module is configured to turn on an exhaust burner to heat exhaust gas flowing through the exhaust system, determine a total stored heat within the DOC based in part on the measurement signal, turn off the exhaust burner after turning on the exhaust burner based on an upper threshold of the total stored heat, and turn on the exhaust burner after turning off the exhaust burner based on a lower threshold of the total stored heat, wherein the lower threshold is less than the upper threshold.

Description

Technical Field

[0001] This disclosure relates to exhaust control systems and methods, and more specifically to systems and methods for controlling the temperature of a selective reduction catalyst (SCR) and the airflow entering the exhaust system.

[0002] introduction

[0003] The information provided in this section is for the purpose of generally presenting the context of this disclosure. The work of the currently named inventors (within the scope described in this section) and aspects of the description that may not otherwise conform to the prior art at the time of filing are neither expressly nor implicitly acknowledged as prior art relative to this disclosure.

[0004] Air is drawn into the engine through the intake manifold. The air is mixed with fuel from one or more fuel injectors to form an air / fuel mixture. This air / fuel mixture is burned in one or more cylinders of the engine. The combustion of the air / fuel mixture produces torque.

[0005] Exhaust gases produced by the combustion of an air / fuel mixture are discharged from the cylinders into the exhaust system. Exhaust gases from engines that burn diesel fuel with excess air may include particulate matter (PM) and gases. These exhaust gases include nitrogen oxides (NOx), such as nitric oxide (NO) and nitrogen dioxide (NO2). Exhaust treatment systems can be used to reduce the amount of NOx and PM in exhaust gases.

[0006] Exhaust treatment systems may include diesel oxidation catalysts (DOC). DOC removes hydrocarbons and / or carbon oxides from exhaust gases. Exhaust treatment systems may also include diesel particulate filters (DPF) to remove particulate matter (PM) from exhaust gases. Exhaust treatment systems may also include selective catalytic reduction (SCR) catalysts. Diesel exhaust fluid (DEF) injectors inject DEF (e.g., a urea-water solution) into a decomposition tube or reactor located upstream of the SCR catalyst. When the DEF encounters hot exhaust gases in the decomposition tube, the water portion undergoes evaporation and the urea undergoes decomposition to form ammonia. The ammonia (NH3) supplied by the DEF is adsorbed by the SCR catalyst. When ammonia is present on the surface of the SCR catalyst and the catalyst is hot, NOx in the exhaust gases reacts with the ammonia to form nitrogen (N2). In this way, the amount of NOx emitted by the engine is reduced. Summary of the Invention

[0007] An exhaust control system for a vehicle includes at least one temperature sensor located within the vehicle's exhaust system, the at least one temperature sensor configured to generate a measurement signal indicating at least one of an inlet temperature and an outlet temperature of a diesel oxidation catalyst (DOC). An exhaust control module is configured to activate an exhaust combustor to heat exhaust flowing through the exhaust system, determine the total heat stored within the DOC based in part on the measurement signal, deactivate the exhaust combustor after activating it based on an upper limit threshold of the total heat stored, and activate the exhaust combustor after deactivating it based on a lower limit threshold of the total heat stored, wherein the lower limit threshold is less than the upper limit threshold.

[0008] Among other features, the exhaust control module is configured to determine the total stored heat within the DOC based on a DOC-based thermal storage tank model. The exhaust control module is configured to determine the total stored heat within the DOC based on H... DOC = M*C*T to determine the total stored heat in the DOC, where H DOC M is the total stored heat within the DOC, C is the mass of the DOC, C is the heat capacity of the DOC, and T is the temperature associated with the DOC. The at least one temperature sensor includes a first temperature sensor located at the inlet of the DOC and a second temperature sensor located at the outlet of the DOC, and the temperature associated with the DOC corresponds to the average of the temperatures measured by the first and second temperature sensors.

[0009] Among other features, the exhaust control module is configured to activate the exhaust combustor before engine start. After activating the exhaust combustor based on a lower threshold of total stored heat, the exhaust control module is configured to deactivate the exhaust combustor based on an upper threshold of total stored heat. The exhaust control module is configured to detect cold start conditions and activate the exhaust combustor before engine start in response to detecting cold start conditions. The exhaust control module is configured to increase the engine idle speed when the exhaust combustor is activated. The upper threshold of total stored heat includes a first upper threshold and a second upper threshold less than the first upper threshold. The exhaust control module is configured to detect cold start conditions and selectively operate the exhaust combustor according to one of the first and second upper thresholds based on whether a cold start condition is detected.

[0010] A method for controlling an exhaust control system for a vehicle includes: generating at least one measurement signal indicating at least one of an inlet temperature and an outlet temperature of a diesel oxidation catalyst (DOC); activating an exhaust combustor to heat exhaust gas flowing through the exhaust system; determining, in part, the total heat stored in the DOC based on the at least one measurement signal; after activating the exhaust combustor, deactivating the exhaust combustor based on an upper limit threshold of the total heat stored; and after deactivating the exhaust combustor, activating the exhaust combustor based on a lower limit threshold of the total heat stored, wherein the lower limit threshold is less than the upper limit threshold.

[0011] Among other features, the method also includes determining the total stored heat within the DOC based on a DOC-based thermal storage tank model. The method also includes determining the total stored heat within the DOC based on H... DOC =M*C*T determines the total stored heat in the DOC, where H DOC M is the total stored heat within the DOC, C is the mass of the DOC, C is the heat capacity of the DOC, and T is the temperature associated with the DOC. The method further includes generating the at least one measurement signal using a first temperature sensor located at the inlet of the DOC and a second temperature sensor located at the outlet of the DOC, wherein the temperature associated with the DOC corresponds to the average of the temperatures measured by the first and second temperature sensors.

[0012] Among other features, the method further includes activating the exhaust combustor before engine start. The method also includes activating the exhaust combustor based on a lower threshold of total stored heat, and then deactivating it based on an upper threshold of total stored heat. The method further includes detecting a cold start condition and activating the exhaust combustor before engine start in response to detecting the cold start condition. The method also includes increasing the engine idle speed when the exhaust combustor is activated. The upper threshold of total stored heat includes a first upper threshold and a second upper threshold less than the first upper threshold. The method further includes: detecting a cold start condition; and selectively operating the exhaust combustor according to one of the first and second upper thresholds based on whether a cold start condition is detected.

[0013] Other areas of applicability of this disclosure will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure. Attached Figure Description

[0014] This disclosure will be more fully understood through detailed embodiments and accompanying drawings, wherein:

[0015] Figure 1A This is a functional block diagram of an example engine system;

[0016] Figure 1B An example of hysteresis control for exhaust combustors is shown;

[0017] Figure 2 This is a functional block diagram of an example exhaust control system; and

[0018] Figure 3 This is a flowchart of an example multi-layer threshold control method for exhaust combustors.

[0019] In the accompanying drawings, reference numerals may be used repeatedly to identify similar and / or identical elements. Detailed Implementation

[0020] The control module directs the injection of diesel exhaust fluid (DEF) upstream of the selective catalytic reduction (SCR) catalyst in the exhaust system. The SCR catalyst receives exhaust gas from the vehicle's engine. The exhaust gas includes nitrogen oxides (NOx). The DEF contains urea and water. Heat from the exhaust gas decomposes the urea from the DEF into ammonia (NH3). The SCR catalyst stores the ammonia. The ammonia reacts with NOx in the exhaust gas, thereby reducing the amount of NOx released from the SCR catalyst.

[0021] Engines can produce high levels of NOx during startup. However, the amount of ammonia stored in the SCR (and stored by the SCR) during startup may be low. The exhaust temperature during engine startup may be too low for the DEF injected into the decomposer to be processed into ammonia. Therefore, after engine startup, the vehicle's NOx output may be relatively high.

[0022] The SCR catalyst can be heated using an exhaust combustor before and / or during engine start-up. The combustor burns air and fuel to heat the SCR catalyst. Combustion can be initiated by a spark plug or another type of ignition device. By preparing the SCR catalyst to store ammonia, which reacts with NOx faster than without performing a heating process, heating the SCR catalyst can reduce the vehicle's NOx output after engine start-up. In some cases, DEF injection can be initiated before engine start-up to further reduce the vehicle's NOx output after engine start-up.

[0023] Therefore, in some cases, the exhaust combustor can be used to preheat the SCR catalyst (i.e., before engine start). Conversely, the exhaust combustor can be used during engine start-up under cold start conditions (i.e., upon receiving an engine start signal under cold start conditions). Under cold start conditions, it is desirable to heat the SCR catalyst and other components of the exhaust treatment system as quickly as possible. Thus, the exhaust combustor can be controlled to heat the exhaust system to a relatively high temperature to ensure that it is not shut off during cold start conditions before the SCR catalyst is sufficiently heated.

[0024] After a cold start, the engine can continue to operate at low load for a period of time, producing relatively cold exhaust and causing the SCR catalyst to operate at a suboptimal temperature. Furthermore, using an exhaust combustor to heat the exhaust becomes necessary; however, the use of an exhaust combustor consumes additional fuel, thus reducing fuel economy and increasing carbon dioxide emissions.

[0025] The exhaust combustor control system and method according to this disclosure are configured to regulate the exhaust combustor to minimize fuel consumption and maintain the SCR catalyst temperature for optimizing NOx conversion during low-load operation. For example, one or more components of the exhaust system (e.g., one or a combination of diesel oxidation catalyst (DOC), diesel particulate filter (DPF), etc.) are modeled as a heat storage tank, and an indicator (e.g., enthalpy) of the total stored heat within the heat storage tank is calculated based on various system inputs. The exhaust combustor is selectively activated based on the calculated enthalpy and one or more thresholds. For example, hysteresis control is implemented to shut off the exhaust combustor when the calculated enthalpy reaches an upper threshold and to activate the exhaust combustor when the calculated enthalpy reaches a lower threshold.

[0026] Although an exhaust burner has been described, the principles of this application can also be implemented using other types of exhaust heaters, including but not limited to high-power electric heaters.

[0027] Now refer to Figure 1A The diagram presents a functional block diagram of an example engine system 100. Engine 102 generates propulsion torque for the vehicle. Although engine 102 is shown and will be discussed as a diesel engine, engine 102 could be another suitable type of engine. One or more electric motors (or electric generators) can additionally generate propulsion torque. For example, air is drawn into engine 102 through intake manifold 104. One or more fuel injectors (such as fuel injector 110) inject fuel mixed with air to form an air / fuel mixture. The air / fuel mixture is burned within cylinders (such as cylinder 114) of engine 102.

[0028] Exhaust gas is discharged from engine 102 to exhaust system 120. The exhaust gas may include particulate matter (PM) and exhaust gases (e.g., emission gases). The exhaust gas includes nitrogen oxides (NOx), such as nitric oxide (NO) and nitrogen dioxide (NO2). Exhaust system 120 includes a treatment system that reduces the respective amounts of NOx and PM in the exhaust gas.

[0029] Exhaust system 120 includes diesel oxidation catalyst (DOC) 122, diesel particulate filter 126, and one or more selective catalytic reduction (SCR) catalysts, such as SCR catalyst 124-1 and SCR catalyst 124-2 (collectively, “SCR catalyst 124”). SCR catalyst 124-1 may, for example, comprise iron zeolite or another suitable type of SCR catalyst. SCR catalyst 124-2 may comprise copper zeolite or another suitable type of SCR catalyst. In various embodiments, SCR catalysts 124-1 and 124-2 may be implemented within the same housing.

[0030] Exhaust gas flows from engine 102 to DOC 122. Exhaust gas exiting DOC 122 flows to DPF 126. DPF 126 filters particulate matter from the exhaust gas. In various embodiments, DPF 126 and DOC 122 may be implemented within the same housing. While an example is provided where DPF 126 is located downstream of DOC 122, DPF 126 may alternatively be located upstream of DOC 122. Exhaust gas flows from DPF 126 to SCR catalyst 124.

[0031] Diesel exhaust fluid (DEF) injector 130 injects DEF upstream of SCR catalyst 124 in exhaust system 120. For example, DEF injector 130 may inject DEF into decomposer 131, where water in the injected DEF evaporates and urea is decomposed and hydrolyzed into NH3. Decomposer 131 may also be referred to as a reactor. For example only, decomposer 131 may be located between DOC 122 and SCR catalyst 124. DEF comprises urea (e.g., CO(NH2)2) and water. DEF is stored in DEF tank 132 prior to injection. DEF pump 134 draws DEF from DEF tank 132 and pumps DEF to DEF injector 130.

[0032] The exhaust control module 138 controls the actuation (e.g., opening and closing) of the DEF injector 130 and thus controls the injection of DEF into the exhaust system 120. The exhaust control module 138 can also control the operation of the DEF pump 134 to maintain a predetermined pressure of DEF input to the DEF injector 130, such as... Figure 2 It is described in more detail in the text.

[0033] When the engine is running, normal burner and DEF control can be used. When the engine is running, urea from the DEF injected by DEF injector 130 reacts with hot exhaust gas to produce ammonia, which is then supplied to the SCR catalyst 124. The heat causes water in the DEF to evaporate, and ammonia (NH3) is supplied to the SCR catalyst 124.

[0034] SCR catalyst 124 stores (i.e., adsorbs) ammonia supplied by DEF. SCR catalyst 124 catalyzes the reaction between the stored ammonia and NOx passing through SCR catalyst 124. The amount of ammonia stored by SCR catalyst 124 can be referred to as the current storage level. The percentage of NOx input to SCR catalyst 124 removed from the exhaust gas via reaction with ammonia can be referred to as the NOx conversion efficiency. NOx conversion efficiency is a function of the current storage level of SCR catalyst 124. By way of example only, NOx conversion efficiency can increase with increasing current storage level of SCR catalyst 124, and vice versa.

[0035] However, the current storage capacity of the SCR catalyst 124 is limited to the maximum amount of ammonia. This maximum amount of ammonia is referred to as the maximum storage capacity of the SCR catalyst 124. Maintaining the current storage capacity of the SCR catalyst 124 close to the maximum storage capacity ensures the removal of the maximum possible amount of NOx from the exhaust gas. In other words, maintaining the current storage capacity close to the maximum storage capacity ensures the achievement of the maximum possible NOx conversion efficiency. However, there is an inverse relationship between the maximum storage capacity and the temperature of the SCR catalyst 124. More specifically, the maximum storage capacity decreases as the SCR temperature increases during engine operation, and vice versa. The reaction of ammonia with NOx produces nitrogen and water. Other components of the exhaust gas, such as oxygen (O2) may also participate in the reaction between ammonia and NOx.

[0036] One or more sensors 150, such as one or more NOx sensors, one or more temperature sensors, one or more oxygen sensors, and / or one or more other types of sensors, can be implemented in the exhaust system 120. For example, a temperature sensor can measure the temperature of the SCR catalyst 124. In various embodiments, the temperature of the SCR catalyst 124 can be estimated based on one or more exhaust temperatures. Other example types of sensors include mass airflow (MAF) sensors, recirculated exhaust flow (EFR) sensors, intake air temperature (IAT) sensors, coolant temperature sensors, manifold absolute pressure (MAP) sensors, engine speed (RPM) sensors, exhaust pressure sensors, and / or one or more other suitable sensors.

[0037] The burner 154 may also be connected upstream of the exhaust system 120, such as DOC 122 and DPF 126. The burner 154 may include a fuel injector 158, a spark plug 162, and an air pump 166. While an example of a burner 154 including a spark plug is provided, this application is also applicable to other types of igniters and ignition devices. When activated, the air pump 166 pumps air into the combustion chamber (within the flame jacket 156) and into the exhaust system 120. The fuel injector 158 injects fuel (e.g., diesel fuel) into the combustion chamber. The fuel mixes with the air from the air pump 166. The spark plug 162 generates a spark within the combustion chamber. The spark ignites the air and fuel from the fuel injector 158 and the air pump 166. The flame jacket 156 is configured to protect the flame within the combustion chamber from being blown out, such as by the exhaust gas from the engine 102 during engine operation.

[0038] The combustion of air and fuel produces hot gases, which can be used to heat one or more components of the exhaust system 120 and / or for one or more other purposes. The exhaust control module 138 controls fuel injection by the fuel injector 158, spark generation by the spark plug 162, and the operation of the air pump 166. In various embodiments, the exhaust control module 138 can control the speed of the air pump 166 regardless of whether the burner 154 is receiving fuel for combustion. When receiving fuel, the exhaust control module 138 can control the speed of the air pump 166 to achieve a desired air-fuel ratio. If the burner 154 is operating while the engine is running, the exhaust control module 138 can operate the burner 154 across the full range of air-fuel ratios required for stable combustion.

[0039] Air pump 166 also pumps air to air valve (V) 170. Air valve 170 regulates the airflow to a second position (such as around flame jacket 156). The air flowing around flame jacket 156 can cool flame jacket 156 and increase its lifespan. In various embodiments, the second position can be between flame jacket 156 and exhaust pipe 172 connected to burner 154. Alternatively, air valve 170 can output air directly from air pump 166 to exhaust pipe 172. Exhaust control module 138 also controls the actuation of air valve 170.

[0040] When engine 102 is running, engine control module (ECM) 174 controls the torque output of engine 102. ECM 174 also controls the starting and stopping of engine 102. ECM 174 can start engine 102, for example, in response to user actuation of one or more user input devices (such as a combination of one or more user input devices of the vehicle, such as an ignition button or switch and / or a remote key). ECM 174 can stop engine 102, for example, in response to user actuation of one or more user input devices of the vehicle (e.g., an ignition button or switch) and / or one or more user input devices of the remote key.

[0041] As described above, the exhaust control module 138 controls the injection of DEF by the DEF injector 130. For example only, the exhaust control module 138 can control the timing and rate of DEF injection. By controlling the DEF injection, the exhaust control module 138 controls the ammonia supply to the SCR catalyst 124 and the current storage level of the SCR catalyst 124. The exhaust control module 138 can determine a target supply rate for ammonia to the SCR catalyst 124, determine a target DEF injection rate to achieve the target supply rate, and control the DEF to be injected at the target DEF injection rate.

[0042] In response to engine start-up, vehicle NOx emissions may be relatively high. In some examples, the SCR catalyst 124 can be preheated before engine start-up when engine 102 is off. Preheating before engine start-up is achieved by operating the combustor 154 before engine start-up. The exhaust control module 138 can control the combustor 154 (by adding fuel via fuel injector 158 and / or air from air pump 166) to preheat, for example, using a lean air / fuel mixture. During preheating, air valve 170 can be closed so that no air flows through air valve 170 to the second position. When engine 102 is running after start-up, exhaust control module 138 can partially or fully open air valve 170 so that air flows from air pump 166 to the second position.

[0043] If the temperature of the SCR catalyst 124 exceeds a predetermined temperature during the warm-up period before engine start, the exhaust control module 138 can initiate DEF injection. The predetermined temperature corresponds to a temperature above which DEF can decompose into ammonia. Warming the SCR catalyst 124 allows for a reduction in NOx emissions after engine start because DEF injection can begin earlier after engine start. DEF injection before engine start can further reduce NOx emissions after engine start.

[0044] At the start of a cold start, the combustor 154 can be operated to heat the SCR catalyst 124 as quickly as possible. In this way, during cold start conditions, the combustor 154 will not be shut off until the SCR catalyst 124 is sufficiently heated. However, after a cold start, the engine 102 can continue to operate at low load for a period of time, producing relatively cold exhaust and causing the SCR catalyst 124 to operate at a suboptimal temperature. Furthermore, using the combustor 154 to heat the exhaust consumes additional fuel, thereby reducing fuel economy and increasing carbon dioxide production.

[0045] According to this application, the exhaust control module 138 is configured to implement multi-layer threshold hysteresis control of the burner 154 based on the calculation of the total stored heat (e.g., enthalpy) within DOC 122 and / or DPF 126. For example, the exhaust control module 138 is configured to control the burner 154 (i.e., selectively turn the burner on and off) by calculating the enthalpy of DOC 122 in response to a heat storage tank model based on DOC 122 and various measurement signals indicating the exhaust temperatures at the inputs and outputs of DOC 122, DPF 126, etc. For example, signal 176 (from sensor 178) indicates the temperature at the inlet of DOC 122, and signal 180 (from sensor 182) indicates the temperature at the outlet of DOC 122.

[0046] Burner 154 is turned on until the total stored heat in DOC 122 reaches a first (upper) threshold, then the burner is turned off. Burner 154 is turned off until the total stored heat in DOC 122 decreases to a second (lower) threshold, then the burner is turned on. Although the total stored heat in DOC 122 is described below, in other examples, the principles of this disclosure can be applied to the calculation of the total stored heat in DOC 122 and DPF 126 (or a portion of DPF 126), or the total stored heat in any other combination of components of DPF 126 or exhaust system 120.

[0047] In this way, burner 154 is controlled to maintain the total stored heat in DOC 122 between an upper and lower threshold. At higher temperatures, NOx conversion increases, along with fuel production and CO2 production. Conversely, at lower temperatures, NOx conversion decreases, along with fuel production and CO2 production. In other words, if burner 154 shuts off earlier, the average temperature of DOC 122 and DPF 126 decreases (corresponding to a lower temperature for SCR catalyst 124). Therefore, while lowering the temperature saves fuel and reduces CO2 emissions, NOx conversion in SCR catalyst 124 becomes less efficient. The upper and lower thresholds for total stored heat, according to this disclosure, are selected to balance NOx conversion, fuel consumption, and CO2 production.

[0048] In one example, it can be based on H DOC =M*C*T (Equation 1) to calculate the total stored heat H in DOC 122. DOC (in kJ), where M is the mass (kg) of DOC 122, C is the heat capacity (kJ / kg-K) of DOC 122, and T is the temperature (K) associated with DOC 122. For example, temperature T can be calculated as the average of the temperature at the inlet and outlet of DOC 122.

[0049] Figure 1BAn example of hysteresis control of burner 154 according to this disclosure is shown. For example, exhaust control module 138 is configured (e.g., using a heat storage tank model of DOC 122 and Equation 1) to calculate the total stored heat of DOC 122 and generate a hysteresis control output 184 to turn burner 154 on and off based on the total stored heat and upper and lower threshold values. By way of example only, hysteresis control output 184 is a binary control signal with a value of "1" to turn burner 154 on and a value of "0" to turn burner 154 off. In this example, the upper threshold is 1360 kJ and the lower threshold is 1300 kJ. When burner 154 is on and total stored heat increases, hysteresis control output 184 is shown as a solid line. Conversely, when burner 154 is off and total stored heat decreases, hysteresis control output 184 is shown as a dashed line.

[0050] The hysteresis control output 184 is initially set to 1 (e.g., before and / or during startup) to turn on burner 154. When burner 154 turns on, the total stored heat increases and reaches an upper threshold, as shown in 186. The hysteresis control output 184 then transitions from 1 to 0 to turn off burner 154, and the total stored heat begins to decrease, as shown in 188. The total stored heat decreases until it reaches a lower threshold, and the hysteresis control output 184 transitions from 0 to 1 to turn on burner 154, as shown in 190. The total stored heat then begins to increase from the lower threshold to the upper threshold. In this way, exhaust control module 138 controls burner 154 such that the total stored heat is maintained between the upper and lower thresholds.

[0051] The upper and lower threshold values ​​are shown as examples only, and other values ​​for the upper and lower threshold values ​​can be used. In some examples, the upper threshold value may vary based on operating conditions. For example, a first upper threshold value may be used when cold start conditions are detected (e.g., engine coolant is below a predetermined threshold, such as 35°C). The first upper threshold value may be selected to be high enough to ensure that the combustor 154 is open for a sufficient period of time to heat the exhaust to the desired temperature. The exhaust control module 138 may then use a second upper threshold value for a predetermined period of time after the cold start. The second upper threshold value is less than the first upper threshold value.

[0052] When no cold start condition is detected (e.g., during a "hot" start condition), the exhaust control module 138 may optionally use a third upper limit threshold at startup. For example, a cold start condition may not be detected when the coolant temperature and / or other indicators suggest that the engine 102 has recently been running (corresponding to a warm start or hot start). A hot start condition may be met, for example, when the engine has only been shut off for less than a predetermined period of time (e.g., less than 20 minutes). The third upper limit threshold may be greater than the second upper limit threshold but less than the first upper limit threshold.

[0053] In this way, the exhaust control module 138 can operate based on two or three upper limit thresholds. In some examples, the lower limit threshold can also vary.

[0054] In some examples, the exhaust control module 138 may also be configured to increase the idle speed of the engine 102 when the combustor 154 is turned on during cold start operation. Increasing the idle speed of the engine 102 increases the exhaust flow to move the heat generated by the combustor 154 downstream, thereby preventing the combustor 154 from overheating and optimizing NOx conversion.

[0055] In the example above, after a cold start and when the engine 102 is not operating under sustained low load conditions, the exhaust can reach a temperature sufficient to prevent the burner 154 from opening. For example, during normal operation of the engine 102, even when the burner 154 is off, the total stored heat calculated by DOC 122 can remain above the lower threshold. In this way, the burner 154 operates only when necessary.

[0056] Figure 2 This is a functional block diagram of an example exhaust control system 200 including an exhaust control module 138 and a burner 154. The DEF control module 204 determines a target DEF injection rate, for example, based on a target (ammonia) supply rate to the SCR catalyst 124, and controls the opening and closing of the DEF injector 130 to control the injection and achieve the target DEF injection rate. The DEF control module 204 can use pulse width modulation (PWM) control or another suitable type of control to control the DEF injector 130.

[0057] Temperature control module 220 controls the operation of components such as air pump 166, air valve 170, fuel injector 158, and spark plug 162. According to this application, temperature control module 220 is configured to control burner 154 based on the total stored heat (e.g., enthalpy) of DOC 122 calculated according to a heat storage tank model 224 of DOC 122. For example, temperature control module 220 includes a hysteresis control module 228 configured to generate a hysteresis control output 184 to selectively turn burner 154 on and off based on the total stored heat (e.g., calculated according to Equation 1, signals 176 and 180 indicating the inlet and outlet temperatures of DOC 122, respectively) and upper and lower threshold values, as described in more detail above.

[0058] The starting module 240 generates a start signal indicating that the engine 102 has been started. In some examples, the starting module 240 may selectively generate a start signal indicating an upcoming engine start (i.e., before the engine 102 is started). An engine status signal indicates whether the engine 102 is running (on), started (activated), or off (shut down). The ECM 174 can set the engine status signal and output it to other modules. When the start signal is generated, the temperature control module 220 activates the air pump 166. Additionally, the temperature control module 220 initiates fuel injection via the fuel injector 158 and begins providing a spark to ignite the air and fuel. Furthermore, the temperature control module 220 opens the air valve 170 to a predetermined open position, causing some air from the air pump 166 to flow to a second position, such as around the flame shield 156.

[0059] Figure 3 This is a flowchart depicting an example multi-layer threshold hysteresis control method 300 for an exhaust combustor. As described above, method 300 can be performed at engine start and / or before engine start. For example, method 300 can be performed using only the relevant components of the exhaust control module 138 and the exhaust system 120.

[0060] Method 300 is configured to operate burner 154 until an upper limit threshold is reached, shut down burner 154 when the upper limit threshold is reached, and restart burner 154 when a lower limit threshold is reached. In this example, method 300 operates based on whether a cold start condition is met, according to a first upper limit threshold and a second upper limit threshold. In other examples, method 300 may operate based on only one upper limit threshold, more than two upper limit thresholds, more than one lower limit threshold, etc.

[0061] At 302, method 300 models one or more components (e.g., DOC 122) as a heat storage tank. For example, the model may be stored in the exhaust control module 138 and / or another location within the engine system 100. In other examples, all or part of the model may be stored and / or executed at a location outside the engine system 100 (e.g., at a remote server, in a cloud computing system, etc.).

[0062] At 304, method 300 optionally determines whether a cold start condition has been detected. For example, method 300 determines whether the engine coolant temperature is below a threshold, or whether the engine has been shut down for a predetermined period of time. If yes, method 300 proceeds to 308 and selects a first upper limit threshold. If no, method 300 selects a second upper limit threshold at 312. In some examples, method 300 may terminate if no cold start condition is detected, and the engine may start according to normal operating parameters (e.g., without operating combustor 154).

[0063] At 316, method 300 (e.g., exhaust control module 138) activates combustor 154. In some examples, method 300 may increase engine idle speed to increase exhaust flow when combustor 154 is activated. At 320, method 300 determines whether the total stored heat in DOC 122 has reached an upper limit threshold. For example, method 300 calculates the total stored heat in DOC 122 based on heat storage tank model 224 (e.g., using Equation 1) and compares the calculated total stored heat with the upper limit threshold. If yes, method 300 proceeds to 324. If no, method 300 continues to update the calculated total stored heat to determine whether the total stored heat in DOC 122 has reached the upper limit threshold.

[0064] At 324, method 300 shuts down burner 154. At 328, method 300 determines whether the total stored heat has reached the lower threshold. If yes, method 300 proceeds to 316 to turn on burner 154. If no, method 300 continues to update the calculated total stored heat to determine whether the total stored heat of DOC 122 has reached the lower or upper threshold.

[0065] In this way, method 300 controls burner 154 so that the total stored heat in DOC 122 is maintained between an upper threshold and a lower threshold.

[0066] The foregoing description is merely illustrative in nature and is in no way intended to limit this disclosure, its application, or its use. The broad teachings of this disclosure can be implemented in many forms. Therefore, while this disclosure includes specific examples, its true scope should not be limited, as other modifications will become apparent upon examination of the drawings, description, and the following claims. It should be understood that one or more steps within the method may be performed in a different order (or simultaneously) without altering the principles of this disclosure. Furthermore, while each embodiment is described above as having certain features, any one or more of those features described relative to any embodiment of this disclosure may be implemented in and / or combined with features of any other embodiment, even if such combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the arrangement of one or more embodiments relative to each other remains within the scope of this disclosure.

[0067] Spatial and functional relationships between components (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “joined,” “linked,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “set.” Unless explicitly described as “direct,” when describing the relationship between a first component and a second component in the above disclosure, the relationship may be a direct relationship where no other intervening components exist between the first and second components, or an indirect relationship (spatially or functionally) where one or more intervening components exist between the first and second components. As used herein, at least one of the phrases A, B, and C should be interpreted as meaning logically (A or B or C) by using a non-exclusive logical OR, and should not be interpreted as meaning “at least one of A, at least one of B, and at least one of C.”

[0068] In a diagram, the direction of the arrows, as indicated by the arrows, typically illustrates the flow of information of interest (such as data or instructions). For example, when components A and B exchange various types of information, but the information sent from component A to component B is relevant to the diagram, the arrow can point from component A to component B. This unidirectional arrow does not imply that no other information is being sent from component B to component A. Furthermore, for information sent from component A to component B, component B can send a request for that information to component A or receive confirmation of that information.

[0069] In this application, including the following definitions, the term "module" or "controller" may be replaced by the term "circuit". The term "module" may refer to, be part of, or include the following: application-specific integrated circuit (ASIC); digital, analog, or mixed-signal analog / digital discrete circuit; digital, analog, or mixed-signal analog / digital integrated circuit; combinational logic circuit; field-programmable gate array (FPGA); processor circuitry (shared, dedicated, or grouped) that executes code; memory circuitry (shared, dedicated, or grouped) that stores code executed by the processor circuitry; other suitable hardware components that provide the aforementioned functionality; or some or all of the above, such as those located in a system-on-a-chip.

[0070] This module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces connected to a local area network (LAN), the Internet, a wide area network (WAN), or a combination thereof. The functionality of any given module in this disclosure may be distributed across multiple modules connected via the interface circuits. For example, multiple modules may allow for load balancing. In another example, a server (also known as a remote or cloud) module may perform some functions on behalf of a client module.

[0071] The term "code" as used above can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, data structures, and / or objects. The term "shared processor circuitry" encompasses a single processor circuitry that executes some or all of the code from multiple modules. The term "group processor circuitry" encompasses processor circuitry that, in combination with additional processor circuitry, executes some or all of the code from one or more modules. Reference to multiple processor circuitry encompasses multiple processor circuitry on a discrete die, multiple processor circuitry on a single die, multiple cores of a single processor circuitry, multiple threads of a single processor circuitry, or a combination of the above. The term "shared memory circuitry" includes a single memory circuitry that stores some or all of the code from multiple modules. The term "group memory circuitry" encompasses memory circuitry that, in combination with additional memory, stores some or all of the code from one or more modules.

[0072] The term "memory circuit" is a subset of the term "computer-readable medium." As used herein, the term "computer-readable medium" does not cover transient electrical or electromagnetic signals propagated through a medium (such as on a carrier wave); therefore, the term "computer-readable medium" can be considered tangible and non-transient. Non-limiting examples of non-transient tangible computer-readable media are non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only memory circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital magnetic tape or hard disk drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0073] The apparatus and methods described in this application can be implemented, in part or in whole, by a special-purpose computer created by configuring a general-purpose computer to perform one or more specific functions embodied in a computer program. The function blocks, flowchart components, and other elements described above serve as software specifications that can be translated into computer programs by the routine work of skilled technicians or programmers.

[0074] A computer program includes processor-executable instructions stored on at least one non-transitory, tangible, computer-readable medium. A computer program may also include or depend on stored data. A computer program may encompass a basic input / output system (BIOS) that interacts with the hardware of a special-purpose computer, device drivers that interact with specific devices of the special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0075] Computer programs may include: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Notation); (ii) assembly code; (iii) object code generated from source code by a compiler; (iv) source code executed by an interpreter; and (v) source code compiled and executed by a just-in-time (JIT) compiler, etc. As an example only, source code may come from languages ​​including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, etc. Fortran, Perl, Pascal, Curl, oCaml, HTML5 (Hypertext Markup Language, 5th Revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Visual Lua, MATLAB, SIMULINK and It is written using the syntax of the language.

Claims

1. An exhaust control system for a vehicle, the exhaust control system comprising: At least one temperature sensor, located within the exhaust system of the vehicle, wherein the at least one temperature sensor is configured to generate a measurement signal indicating at least one of the inlet temperature and outlet temperature of the diesel oxidation catalyst (DOC); and An exhaust control module configured to activate an exhaust burner to heat the exhaust gas flowing through the exhaust system. The total stored heat within the DOC is determined in part based on the measurement signal. After the exhaust burner is turned on, it is turned off based on the upper limit threshold of the total stored heat. After the exhaust burner is shut down, the exhaust burner is turned on based on a lower threshold of the total stored heat, wherein the lower threshold is less than the upper threshold. When a cold start condition is detected, the upper limit threshold of the total stored heat is set to a first upper limit threshold, and When no cold start condition is detected, the upper limit threshold of the total stored heat is set to a second upper limit threshold that is less than the first upper limit threshold.

2. The exhaust control system of claim 1, wherein the exhaust control module is configured to determine the total stored heat in the DOC based on a thermal storage tank model of the DOC.

3. The exhaust control system according to claim 2, wherein the exhaust control module is configured to... To determine the total stored heat within the DOC, and wherein H DOC M is the total stored heat in the DOC, C is the mass of the DOC, T is the heat capacity of the DOC, and T is the temperature associated with the DOC.

4. The exhaust control system of claim 3, wherein the at least one temperature sensor comprises a first temperature sensor located at the inlet of the DOC and a second temperature sensor located at the outlet of the DOC, and wherein the temperature associated with the DOC corresponds to the average of the temperatures measured by the first temperature sensor and the second temperature sensor.

5. The exhaust control system of claim 1, wherein the exhaust control module is configured to turn on the exhaust burner before the engine is started.

6. The exhaust control system of claim 1, wherein after the exhaust burner is turned on based on the lower threshold of the total stored heat, the exhaust control module is configured to turn off the exhaust burner based on the upper threshold of the total stored heat.

7. The exhaust control system of claim 1, wherein the exhaust control module is configured to detect cold start conditions and, in response to detecting the cold start conditions, to activate the exhaust combustor before engine start.

8. The exhaust control system according to claim 1, wherein the exhaust control module is configured to increase the engine idle speed when the exhaust burner is turned on.

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