Reducing agent supply systems and processes

Abstract

Metering module (214; 112), comprising: an inlet manifold (216) configured to selectively receive reducing agent from a pump (212); an outlet manifold (228) configured to selectively supply the reducing agent to a nozzle (230); a first branch (218) coupled to the inlet manifold and the outlet manifold, the first branch being configured to selectively supply the reducing agent to the outlet manifold from the inlet manifold, the first branch having a first flow restrictor (226) configured to limit the reducing agent when the reducing agent is supplied to the outlet manifold;and a second branch (220) coupled to the inlet manifold and the outlet manifold, wherein the second branch is configured to selectively supply the reducing agent from the inlet manifold to the outlet manifold separately from the first branch, wherein the second branch has a second flow restrictor (226) configured to limit the reducing agent when the reducing agent is supplied to the outlet manifold.

Description

TECHNICAL FIELDThe present application relates generally to the field of aftertreatment systems for internal combustion engines.BACKGROUNDIn internal combustion engines, such as diesel engines, nitrogen oxide (NO x-) compounds may be emitted in the exhaust gas. To reduce NO x- emissions, a selective catalytic reduction (SCR) process may be used to convert the NO x- compounds into neutral compounds such as diatomic nitrogen, water, or carbon dioxide using a catalyst and a liquid reducing agent. The catalyst may be enclosed in a catalyst chamber of an exhaust system, such as that of a vehicle or a power generation unit. A liquid reductant such as anhydrous ammonia, aqueous ammonia, diesel exhaust fluid (DEF), or aqueous urea is typically introduced into the exhaust flow upstream of the catalyst chamber.To introduce the liquid reductant into the exhaust flow for the SCR process, an SCR system may dose or otherwise introduce the liquid reductant through a dosing module, wherein the dosing module evaporates or sprays the liquid reductant into an exhaust pipe of the exhaust system upstream of the catalyst chamber. An amount of the liquid reductant sprayed into the exhaust pipe is metered by controlling a valve or a pump that provides the liquid reductant to the valve.In some applications, the liquid reductant is provided to the valve by the pump at a fixed or variable pressure. In these applications, the amount of liquid reductant sprayed into the exhaust pipe may be varied by changing the valve position. In other applications, a fixed displacement pump is controlled by varying a number of pump strokes to directly meter the amount of liquid reductant sprayed into the exhaust pipe without the use of a valve. However, none of these approaches provide multiple flow paths, each having a individually controllable valve and an orifice that provides the reductant to a common outlet at a target flow rate such that an adjusted flow rate can be achieved by controlling the valves. Therefore, none of these approaches provide for control of a turndown ratio (e.g., ratio of maximum flow rate to minimum flow rate, etc.) by adding and removing flow paths, openings, or valves.Further metering modules are known from US 2016 / 0298568 A1 and DE 10 2009 016 810 A1.SUMMARYA dosing module according to the present invention is given in claim 1. A reducing agent supply system according to the present invention is set out in claim 9. A combined manifold according to the present invention is set out in claim 16. Further preferred embodiments are set out in the dependent claims.In one embodiment, a dosing module includes an intake manifold, an exhaust manifold, a first branch, and a second branch. The intake manifold is configured to selectively receive reductant from a pump. The exhaust manifold is configured to selectively provide the reductant to a nozzle. The first branch is coupled to the intake manifold and the exhaust manifold. The first branch is configured to selectively provide the reductant from the intake manifold to the exhaust manifold. The first branch includes a first flow restrictor configured to limit the reductant when the reductant is provided to the exhaust manifold. The second branch is coupled to the intake manifold and the exhaust manifold. The second branch is configured to selectively provide the reductant from the intake manifold to the exhaust manifold separately from the first branch. The second branch includes a second flow restrictor configured to limit the reductant when the reductant is provided to the exhaust manifold.In another embodiment, a reductant delivery system includes a tank, a nozzle, a first pump, an intake manifold, an exhaust manifold, and a first branch. The tank is configured to contain reductant. The nozzle is configured to selectively provide the reductant into an exhaust conduit. The first pump is configured to selectively draw the reductant from the tank. The intake manifold is configured to selectively receive the reductant from the first pump. The exhaust manifold is configured to selectively provide the reductant to the nozzle. The first branch is coupled to the intake manifold and the exhaust manifold. The first branch is configured to selectively provide the reductant from the intake manifold to the exhaust manifold. The first branch includes a first valve and a first restrictor. The first valve may be operated between an open position where reductant is provided from the intake manifold to the exhaust manifold through the first branch and a closed position where reductant is not provided from the intake manifold to the exhaust manifold through the first branch. The first flow restrictor is configured to limit the reductant as the reductant is provided to the exhaust manifold through the first branch.In yet another embodiment, a combined manifold includes an intake manifold, an exhaust manifold, a first branch, and a second branch. The intake manifold is configured to selectively receive reductant from a pump. The exhaust manifold is configured to selectively provide the reductant to a nozzle. The first branch is coupled to the intake manifold and the exhaust manifold. The first branch is configured to selectively provide the reductant from the intake manifold to the exhaust manifold. The first branch includes a first flow restrictor configured to limit the reductant when the reductant is provided to the exhaust manifold. The second branch is coupled to the intake manifold. The second branch is configured to receive the reductant from a tank and selectively provide the reductant to the intake manifold such that the reductant is provided to the pump via the intake manifold. The intake manifold, the exhaust manifold, the first branch, and the second branch are structurally integrated.BRIEF DESCRIPTION OF THE DRAWINGSThe details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, aspects and advantages of the disclosure will become apparent from the specification, drawings and claims to which: FIG. 1 is a schematic block diagram of an example aftertreatment system including an example reductant delivery system for an exhaust system; FIG. 2 is a block diagram of an example reductant delivery system for an aftertreatment system, such as the aftertreatment system shown in FIG. 1 ; FIG. 3 is a cross-sectional view of an example manifold for a dosing module for a reductant delivery system for an aftertreatment system, such as the reductant delivery system shown in FIG. 2 ; FIG. 4 is a block diagram of an example reductant delivery system for an aftertreatment system, such as the aftertreatment system shown in FIG. 1, utilizing the manifold shown in FIG. 3 ; FIG. 5 is a block diagram of an example controller for a reductant delivery system for an aftertreatment system, such as the reductant delivery system shown in FIG. 2 ; FIG. 6 is a flow chart for an example process for executing a dosing command by a reductant delivery system for an aftertreatment system, such as the reductant delivery system shown in FIG. 2 ; and FIG. 7 is a graph depicting various flow and pressure difference curves for various pump configurations.It should be noted that some or all of the figures are schematic diagrams for purposes of illustration. The figures are provided for the purpose of illustrating one or more implementations with explicit understanding that they are not used to limit the scope or meaning of the claims.DETAILED DESCRIPTIONFollowing are more detailed descriptions of implementations of methods, apparatus, and systems for reductant delivery in an aftertreatment system and various concepts related thereto. The various concepts introduced above and described in detail below may be implemented in any of numerous ways, as the described concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for purposes of illustration.I. OVERVIEWInternal combustion engines (e.g., diesel engines, etc.) produce exhaust gases that are frequently treated in an aftertreatment system. The treatment often includes treating (e.g., dosed admixing, etc.) the exhaust gases with a reductant. The metered addition of the exhaust gases is usually effected by providing the exhaust gases with pressurized reducing agent. This reductant is typically metered by a pulsing mechanism that basically provides inconsistent flow (e.g., through the use of a variable valve and fixed displacement pump, etc.). To mitigate this inconsistent flow, aftertreatment systems with accumulators or pressure regulators may be employed so that the aftertreatment system is customized for a specific application. Additionally, this inconsistent flow may cause excessive separation of the reductant (e.g., by crystallization, etc.) into nozzles or lances, making the nozzles or lances undesirable.The implementations described herein relate to a reductant delivery system that uses a dosing module having a plurality of branches, each of the branches including an independently controllable valve and a flow restrictor such that the valve controls the flow of reductant through the flow restrictor. By controlling the individual valves, an exhaust conduit may receive one (e.g., custom, etc.) The flow rate of the reducing agent may be provided by the dosing module. The reductant delivery system is capable of achieving smooth, continuous flow without the use of accumulators or pressure regulators, and the pressure within the dosing module does not fluctuate with changes in nozzle or injector response. In addition to controlling the valves that provide relatively inaccurate control of the flow rate of reductant provided to the exhaust conduit, the reductant delivery system may control a speed of the pump or use a bypass mechanism to provide relatively accurate control of the flow rate of reductant provided to the exhaust conduit.The reductant delivery system is capable of custom-making the dosing module to mitigate the effects of pressure losses arising from, for example, head height and line length. In addition, the reductant delivery system is capable of being customized for different aftertreatment systems, for example, by the exchange of flow restrictors or pumps and / or by the incorporation of more or fewer branches. In this way, the reductant delivery system is advantageous from the standpoint of manufacturing the aftertreatment system because the reductant delivery system enables adaptation to many different configurations of the aftertreatment system with relatively simple changes to the reductant delivery system, as opposed to using different reductant delivery systems with different aftertreatment systems, which is cost intensive and inefficient.The reductant delivery system uses a feedback control process that compares a target flow rate of reductant provided to the exhaust conduit with a measured flow rate of reductant provided to the exhaust conduit. In contrast to this control process, many dispensers use control processes. These control processes lack the ability to correct overdosage or underdosage. These dispensers overcome this deficiency by constantly providing excess reductant. However, this results in unnecessary reducing agent consumption, making these open-loop dispensers undesirable.II. SURVEY OF AFTERTREATMENT SYSTEMFIG. 1 illustrates an aftertreatment system 100 including an example reductant delivery system 110 for an exhaust system 190. The exhaust system 190 receives exhaust gases from an internal combustion engine (e.g., an internal combustion engine having a thirty-eight liter displacement, an internal combustion engine having a one hundred twenty liters displacement, etc.). The aftertreatment system 100 includes a particulate filter (e.g., a diesel particulate filter (DPF) 102), the reductant delivery system 110, a decomposition chamber 104 (e.g., reactor, etc.), an SCR catalyst 106, and a sensor 150.The DPF 102 is configured to remove particulate matter, such as soot, from exhaust gas flowing in the exhaust system 190. The DPF 102 includes an inlet through which the exhaust enters and an outlet through which the exhaust exits after substantially filtering particulate matter from the exhaust and / or converting particulate matter to carbon dioxide. In some implementations, the DPF 102 may be omitted.The decomposition chamber 104 is configured to convert a reductant such as urea or diesel exhaust fluid (DEF) into ammonia. The decomposition chamber 104 includes a reductant delivery system 110 having a dosing module 112 (e.g., doser, etc.) configured to dose the reductant into the decomposition chamber 104. In some implementations, the reductant is injected upstream of the SCR catalyst 106. The reductant droplets then pass through the processes of evaporation, photolysis, and hydrolysis to form gaseous ammonia within the exhaust system 190. The decomposition chamber 104 includes an inlet in fluid communication with the DPF 102 to receive the exhaust gas containing NO x- emissions, and an outlet through which exhaust gas, NO x- emissions, ammonia, and / or reductant flow to the SCR catalyst 106.The decomposition chamber 104 includes the dosing module 112 attached to the decomposition chamber 104 such that the dosing module 112 may dose the reductant into the exhaust gases flowing into the exhaust system 190. The dosing module 112 may include an insulator 114 disposed between a portion of the dosing module 112 and the portion of the decomposition chamber 104 on which the dosing module 112 is mounted. The dosing module 112 is fluidly coupled to one or more reductant sources 116. In some implementations, a pump 118 may be used to apply pressure to the reductant from the reductant sources 116 for delivery to the dosing module 112.The dosing module 112 is also fluidly coupled to one or more air sources 115. The air sources 115 may be, for example, an air intake or air storage device (e.g., a tank, etc.). A pump 117 (e.g., a lift pump, etc.) is used to pressurize the air from the air sources 115 for delivery to the dosing module 112 (e.g., via pressure lines, etc.). The dosing module 112 mixes the air from the air sources 115 and the reductant from the reductant sources 116 and delivers the air-reductant mixture to the decomposition chamber 104 via a static dosing lance assembly 119. The static dosing lance assembly 119 may be configured to distribute the air-reductant mixture in a desired path or dispersion pattern in the decomposition chamber 104. The static dosing lance assembly 119 may include a single dosing lance or a plurality of dosing lances such that the dosing module 112 may be customized for a target application.The dosing module 112, the pump 117, and the pump 118 are also electrically or communicatively coupled to a controller 120. The controller 120 is configured to control the dosing module 112 to dose the air-reductant mixture into the decomposition chamber 104. The controller 120 may also be configured to control the pump 117 and / or the pump 118. For example, the controller 120 may control the pump 117 and the pump 118 to obtain a target mixture of air and reductant provided to the decomposition chamber 104 via the static dosing lance assembly 119.The controller 120 may include a microprocessor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc., or combinations thereof. The controller 120 may include memory including, but not limited to, an electronic, optical, magnetic, or other data storage or transmission device capable of providing program instructions to a processor, an ASIC, an FPGA, etc. The memory may include a memory chip, an electrically erasable programmable read-only memory (EEPROM), an erasable programmable read-only memory (EPROM), a flash memory, or any other suitable memory from which the controller 120 may read instructions. The instructions may include code from any suitable programming language.The SCR catalyst 106 is configured to contribute to the reduction of NO x- emissions by accelerating a NO x- reduction process between the ammonia and the NO x of the exhaust gas in diatomic nitrogen, water, and / or carbon dioxide. The SCR catalyst 106 includes an inlet in fluid communication with the decomposition chamber 104 from which exhaust gas and reductant is received, and an outlet in fluid communication with an end of the exhaust system 190.The exhaust system 190 may further include an oxidation catalyst (e.g., a diesel oxidation catalyst (DOC)) in fluid communication with the exhaust system 190 (e.g., downstream of the SCR catalyst 106 or upstream of the DPF 102) to oxidize hydrocarbons and carbon monoxide in the exhaust gas.In some implementations, the DPF 102 may be downstream of the decomposition chamber 104. For example, the DPF 102 and the SCR catalyst 106 may be combined into a single unit. In some implementations, the dosing module 112 may instead be positioned downstream of a turbocharger or upstream of a turbocharger.The sensor 150 may be coupled to the exhaust system 190 to detect a state of the exhaust gas flowing through the exhaust system 190. In some implementations, the sensor 150 may include a portion disposed in the exhaust system 190; for example, a tip of the sensor 150 may extend into a portion of the exhaust system 190. In other implementations, the sensor 150 may receive exhaust gas through another conduit, such as through one or more sample tubes extending out of the exhaust system 190. While the sensor 150 is shown positioned downstream of the SCR catalyst 106, it should be appreciated that the sensor 150 may be positioned at any other position of the exhaust system 190 - including upstream of the DPF 102, within the DPF 102, between the DPF 102 and the decomposition chamber 104, within the decomposition chamber 104, between the decomposition chamber 104 and the SCR catalyst 106, within the SCR catalyst 106, or downstream of the SCR catalyst 106. Additionally, two or more sensors 150 may be used to detect a condition of the exhaust gas, such as two, three, four, five, or six sensors 150, with each sensor 150 located at one of the aforementioned positions of the exhaust system 190.EXAMPLE OF REDUCING AGENT DELIVERY SYSTEMFIG. 2 illustrates a reductant delivery system 200, such as the reductant delivery system 110 shown in FIG. 1, according to an example embodiment. As will be described in more detail herein, the reductant delivery system 200 performs reductant and air dosing and provides a reductant-air mixture to a nozzle or lance, such as the static dosing lance assembly 119. The reductant delivery system 200 includes electronic controllers that separately control a number of valves that each independently dose the reductant so that a target amount (e.g., a target flow rate, a target pressure, etc.) of the reductant may be provided by the reductant delivery system 200. The reductant delivery system 200 may be used in a continuous dosing application where intermittent flow of reductant to an exhaust conduit is not advantageous. In these applications, additional atomizing mechanisms (e.g., air atomizing mechanisms, thermal atomizing mechanisms, mechanical atomizing mechanisms, etc.) may be employed (e.g., within an exhaust conduit, etc.).The reductant delivery system 200 includes a tank 202 (e.g., reserve tank, main tank, etc.) storing the reductant and a pump 204 (e.g., reserve pump, main pump, etc.). The pump 204 is configured to draw the reductant from the tank 202 and provide a target amount of the reductant. The pump 204 electronically communicates with and is controlled by a controller 206 as illustrated by the dashed-dotted lines in FIG. 2. For example, the controller 206 may control the speed of an impeller of the pump 204.The reductant delivery system 200 also includes a day tank 208 (e.g., critical tank, etc.) that receives the reductant from the pump 204, a filter 210 (e.g., reductant filter, particulate filter, screen filter, mesh filter, etc.) that receives the reductant from the day tank 208 and filters the reductant, and a pump 212 (e.g., day pump, critical pump, etc.). The pump 212 is configured to draw the reductant from the day tank 208 through the filter 210 and provide a target amount of the reductant from the pump 212. The pump 212 electronically communicates with and is controlled by the controller 206. For example, the controller 206 may control the speed of an impeller of the pump 212. Pump 212 is a variable speed or no pressure flow pump. In an exemplary embodiment, reductant delivery system 200 does not include accumulators or pressure regulators, and is thus capable of achieving continuous flow with line pressure that does not fluctuate due to injector behavior.The day tank 208 and the pump 212 are configured to provide the reductant to the reductant delivery system 200 without the use of the pump 204 and the tank 202. For example, the day tank 208 may receive the reductant from the tank 202 such that the day tank 208 is filled with the reductant, and the reductant may be subsequently or simultaneously provided to the pump 212. The pump 212 may be configured to draw the reductant from the day tank 208 only when the day tank 208 includes a threshold amount (e.g., a minimum amount, etc.) of the reductant. The day tank 208 and the pump 212 may function to store an amount (e.g., seventy-five liters, five hundred liters, one thousand liters, two thousand liters, etc.) of reductant in the event the reductant may no longer be provided from the tank 202 (e.g., when the pump 204 is no longer operable, etc.). In this way, the day tank 208 and the pump 212 may be advantageous in mission critical applications (e.g., emergency flow diesel generators, dual fuel boilers, etc.).The reductant delivery system 200 also includes a dosing module 214, such as the dosing module 112 shown in FIG. 1. The dosing module 214 includes an intake manifold 216 that receives the reductant from the pump 212. The intake manifold 216 is configured to distribute the reductant (e.g., uniform, balanced, etc.) to a plurality of branches (e.g., flow paths, etc.). In FIG. 2, the dosing module 214 is shown to include a first branch 218, a second branch 220, and a third branch 222. The first branch 218, the second branch 220, and the third branch 222 each include a valve 224 (e.g., electronically controllable valve, solenoid valve, electronic ball valve, etc.) that receives the reductant from the intake manifold 216, and a flow restrictor 226 (e.g., nozzle, etc.) that selectively receives the reductant from the valve 224 and provides the reductant to an exhaust manifold 228.Each of the valves 224 may be operated (e.g., configured to rotate between, etc.) a first position (e.g., an open position, etc.) and a second position (e.g., a closed position, etc.) independently of the other valves 224. It should be appreciated that the dosing module 214 may include two, four, six, or more branches similar to the first branch 218, the second branch 220, and the third branch 222. In this way, reductant delivery system 200 may be flexibly deployed for relatively easy installation into a plurality of aftertreatment systems by simply adding or removing branches and / or by changing the configuration of valves 224 and / or flow restrictors 226.By connecting to each of the first branch 218, the second branch 220, and the third branch 222, the intake manifold 216 and the exhaust manifold 228 reduce the complexity of the piping and the costs associated with the reductant delivery system 200 and help optimize the responsiveness of the dosing module 214. Although not shown, the dosing module 214 may include a purge valve (e.g., bleed valve, bleed valve, etc.) that prevents positive pressure in the intake manifold 216 and / or aids in draining the dosing module 214 (e.g., for servicing the dosing module 214).The reductant delivery system 200 also includes a nozzle 230 that receives the reductant from the exhaust manifold 228. Reductant delivery system 200 also includes an air delivery system 232 that includes an air pump 234, an air supply 235 (e.g., air inlet, air tank, etc.), and a valve 236 that receives air from air supply 235. In addition to receiving the reductant from the exhaust manifold 228, the nozzle 230 also separately receives the air from the valve 236. The valve 236 electronically communicates with the controller 206 such that the controller 206 may control the valve 236 to provide a target amount of air to the nozzle 230. The nozzle 230 is configured to combine the reductant from the exhaust manifold 228 and the air from the valve 236 into a reductant-air mixture and provide the reductant-air mixture to an exhaust conduit 238, such as the decomposition chamber 104 shown in FIG. 1.Each of the valves 224 electronically communicates with the controller 206 and may be individually actuated by the controller 206. Each of the valves 224 individually controls (e.g., modulates, etc.) a flow of the reductant through one of the first branch 218, the second branch 220, and the third branch 222. By controlling the valves 224, the controller 206 is able to control (e.g., modulate, regulate, etc.) how much reductant is provided to the individual flow restrictors 226. Each of the flow restrictors 226 has a configuration (e.g., physical structure, etc.) that provides a target amount of reductant to the exhaust manifold 228 based on a diameter of an opening (e.g., opening, passage, etc.) defined in the flow restrictor 226. For example, the orifice with restrictor 226 may have a diameter of 0.33 millimeters, 0.4 millimeters, 0.65 millimeters, and other similar diameters. Further, the restrictor 226 may include multiple openings having the same or different diameters.In an example application, each of the flow restrictors 226 may have a different diameter opening and be configured to provide a different target amount of reductant to the exhaust manifold 228. For example, the restrictor 226 of the first branch 218 may be configured to provide the reductant to the exhaust manifold 228 at a first flow rate; the restrictor 226 of the second branch 220 may be configured to provide the reductant to the exhaust manifold 228 at a second flow rate greater than the first flow rate; and the restrictor 226 of the third branch 222 may be configured to provide the reductant to the exhaust manifold 228 at a third flow rate greater than the second flow rate. This example is illustrated in Table 1 below. TABLE 1: EXAMPLE OF VARIOUS FLOW RESTRICTORS 226. TABLE 1: EXAMPLE OF VARIOUS FLOW RESTRICTORS 226.First branch 218D 1Q 1Second branch 220D 2; D 2 >D 1Q 2 >Q 1Third branch 222D 3, D 3 >D 2 >D 1Q 3 >Q 2 >Q 1By controlling valves 224 and knowing the target amounts of reductant provided by each of flow restrictors 226, controller 206 may achieve a target total amount of reductant provided to exhaust manifold 228 and ultimately nozzle 230. The controller 206 uses the valves 224 to achieve a "coarse" or relatively inaccurate control over the target total amount of reductant provided to the nozzle 230. However, the controller 206 also uses the pump 212 to achieve a "fine" or relatively precise control of the target total amount of reductant provided to the nozzle 230. For example, a speed of the pump 212 related to an amount of reductant provided by the pump 212 may be varied by the controller 206 (e.g., from one thousand revolutions per minute (U / min) to five thousand U / min, etc.) to provide a target amount of reductant to the first branch 218, the second branch 220, and the third branch 222 within which the valves 224 are controlled to achieve the target total amount of reductant provided to the nozzle 230 by knowing the configurations of the flow restrictors 226 by the controller 206. Control over the target total amount of reductant provided to the nozzle 230 may be changed smoothly so that the reductant provided to the nozzle 230 is not substantially interrupted.Reductant delivery system 200 also includes at least one sensor 240 that can communicate with both intake manifold 216 and exhaust manifold 228. The at least one sensor 240 is configured to measure a difference in a parameter (e.g., pressure, temperature, flow rate, quality, etc.) between the intake manifold 216 and the exhaust manifold 228. The at least one sensor 240 may electronically communicate with the controller 206 and is configured to provide a sensed parameter related to the difference of the parameter to the controller 206. In an example embodiment, the at least one sensor 240 measures a difference between a first pressure within the intake manifold 216 and a second pressure within the exhaust manifold 228, and provides the difference to the controller 206. For example, the controller 206 may use this difference to determine a flow of reductant from the nozzle 230. To determine this, the controller 206 may use knowledge of the reductant specific gravity and temperature (e.g., determined by a sensor coupled to the controller 206, programmed into the controller 206, etc.) and knowledge of the orifice diameter of each of the flow restrictors 226 (e.g., programmed into the controller 206, etc.).In some applications, the at least one sensor 240 includes a first sensor that measures a parameter within the intake manifold 216 and a second sensor that measures a parameter within the exhaust manifold 228, and the two sensors provide the measured parameters to the controller 206, which in turn calculates the difference between them. In one application, the at least one sensor 240 includes a first sensor configured to measure one parameter (e.g., pressure, etc.) within the intake manifold 216, and a second sensor configured to measure another parameter (e.g., temperature, etc.) within the exhaust manifold 228. The difference may be a pressure difference between the intake manifold 216 and the exhaust manifold 228. By controlling the pressure differential using valves 224, reductant delivery system 200 may account for head height and line length insensitivity.Reductant delivery system 200 also includes a sensor 242 that can communicate with a conduit between valve 236 and nozzle 230. The sensor 242 is configured to measure a parameter (e.g., pressure, temperature, flow rate, quality, etc.) between the valve 236 and the nozzle 230. The sensor 242 can electronically communicate with the controller 206 and is configured to provide a sensed parameter related to the parameter to the controller 206. In an exemplary embodiment, sensor 242 measures a pressure of the air between valve 236 and nozzle 230 and provides the pressure to controller 206.FIG. 3 illustrates a combined manifold 300 for a reductant delivery system, such as reductant delivery system 200 shown in FIG. 2, and another reductant delivery system 400 shown in FIG. 4. The combined manifold 300 includes the intake manifold 216, which receives the reductant through an inlet 302 that receives the reductant from the pump 212. The combined manifold 300 also includes the valves 224 in fluid communication with the intake manifold 216. The combined manifold 300 includes the first branch 218, the second branch 220, the third branch 222, and a fourth branch 304. As described in FIG. 2, the first branch 218, the second branch 220, the third branch 222, and the fourth branch 304 each include a restrictor 226. The combined manifold 300 also includes the exhaust manifold 228 that selectively receives the reductant from each of the first branch 218, the second branch 220, the third branch 222, and the fourth branch 304.As shown in FIG. 3, the combined manifold 300 also includes a purging leg 306 coupled to the exhaust manifold 228 and a valve 224 coupled to the intake manifold 216. The flushing leg 306 does not include the flow restrictor 226. The combined manifold 300 also includes an outlet 308 that provides the reductant from the exhaust manifold 228, including the purge leg 306, to the nozzle 230, as shown in FIG. 4. The valve 224 of the purge leg 306 is configured to selectively purge the reductant from the intake manifold 216 by providing the reductant through the valve 224 to the purge leg 306 and into the exhaust manifolds 228.The combined manifold 300 further includes an intake branch 310 coupled to an intake inlet 312 and including a valve 224 coupled to the intake manifold 216. The suction branch 310 does not include the restrictor 226. The intake inlet 312 receives the reductant directly from the day tank 208 via the filter 210. The valve 224 of the intake branch 310 is configured to be controlled to selectively provide the reductant to the pump 212 via the intake manifold 216. In this way, valve 224 may provide reductant to pump 212 to intake pump 212 (e.g., to fill pump 212 with the reductant before pump 212 provides the reductant to intake manifold 216 via port 302, etc.).The combined manifold 300 also includes a first sensor port 314 coupled to the intake manifold 216 and a second sensor port 316 coupled to the exhaust manifold 228. The first sensor terminal 314 and the second sensor terminal 316 are configured to be coupled to at least one of the sensors 240. As mentioned above, at least sensor 240 may be distributed to a first sensor coupled to intake manifold 216 and a second sensor coupled to exhaust manifold 228. In these applications, the first sensor terminal 314 may be coupled to the first sensor and the second sensor terminal 316 may be coupled to the second sensor.In some implementations, the combined manifold 300 further includes a reductant passage 318 having an inlet 320 and an outlet 322. The inlet 320 receives the reductant from the day tank 208 via the filter 210. Outlet 322 provides reductant from reductant passage 318 to pump 212. Reductant passage 318 is separate from intake branch 310. Reductant passage 318 does not include valve 224 and thus continuously provides reductant to pump 212 such that reductant is always ready to pump 212 for provision to intake manifold 216. The intake branch 310 supplements the reductant passage 318 by providing additional reductant to the pump 212 to allow the pump 212 to intake.As shown in FIG. 3, the intake manifold 216, the exhaust manifold 228, the first branch 218, the second branch 220, the third branch 222, the fourth branch 304, the purge leg 306, the intake branch 310, and the reductant passage 318 are structurally integrated into the combined manifold 300. To achieve this integrated structure, the combined manifold 300 may be machined from a billet or cast from a mold, for example.FIG. 4 also illustrates that the valves 224 of the fourth branch 304, the purge leg 306, and the intake branch 310 may communicate with and be controlled by the controller 206 as described with respect to the valves 224 of the first branch 218, the second branch 220, and the third branch 222.FIG. 5 illustrates the controller 206 according to an example embodiment. The controller 206 includes an input / output (I / O) interface 500 and a processing circuit 502. I / O interface 500 enables interaction between processing circuit 502 and pump 204, pump 212, valves 224, air pump 234, valve 236, at least one sensor 240, and sensor 242. The processing circuit 502 includes a processor 504 and a memory 506. The memory 506 may include, but is not limited to, an electronic, optical, magnetic, or any other memory or transmission device capable of providing a processor 504 with program instructions. The memory 506 may include a memory chip, EEPROM, EPROM, flash memory, or other suitable memory from which the module can read instructions. The instructions may include code from any suitable programming language.The memory 506 includes a number of modules (e.g., microprocessors, ASIC, FPGAs, etc.). As shown in FIG. 5, the memory 506 includes a first pump module 508, a second pump module 510, a first branch module 512, a second branch module 514, a third branch module 516, and a sensor module 518. The first pump module 508 is configured to control the interactions between the controller 206 and the pump 204. The second pump module 510 is configured to control the interactions between the controller 206 and the pump 212. The first branch module 512 is configured to control the interactions between the controller 206 and the valve 224 of the first branch 218. The second branch module 514 is configured to control the interactions between the controller 206 and the valve 224 of the second branch 220. The third branch module 516 is configured to control the interactions between the controller 206 and the valve 224 of the third branch 222.Although not shown, reductant delivery system 200 may also include a filter between tank 202 and pump 204. Although not shown, reductant delivery system 200 may include a bypass line connected between day tank 208 and pump 212 and between day tank 208 and filter 210. Use of this bypass line may be controlled by a valve controllable by the controller 206 to cause the reductant to bypass the day tank 208. Such a bypass may be advantageous in high demand applications or when the day tank 208 is empty.IV. EXAMPLE CONTROL SYSTEM FOR THE EXAMPLE REDUCTANT DELIVERY SYSTEMFIG. 6 illustrates a process 600 for executing a dosing command by a reductant delivery system, such as reductant delivery system 200. The process 600 meters the reductant provided to the exhaust conduit 238. Process 600 is a control process that compares a target parameter (e.g., flow rate, etc.) of the reductant provided to the exhaust conduit with a measured parameter of the reductant provided to the exhaust conduit 238. In contrast to this control process, many dispensers use control processes that are unable to correct overdosage or underdosage. These open-loop dispensers overcome this deficiency by continuously providing excess reductant causing unnecessary reductant consumption and making these open-loop dispensers undesirable.The process 600 includes, at block 602, receiving a dosing command by the controller 206 (e.g., by the processor 504, etc.). For example, a dosing command may be received by the controller 206 from the controller 120 of the aftertreatment system 100. The dosing command may include, for example, a dosing amount (e.g., a target volume of reductant, a target flowrate of reductant, a target pressure of reductant, etc.) to be provided to the exhaust conduit 238. The process 600 further includes, at block 604, determining, by the controller 206 (e.g., by the processor 504, etc.), a target flow rate of the reductant to be provided to the exhaust conduit 238. For example, if the dosing command includes a target volume of reductant, the controller 206 may match the target volume of reductant with a target flow rate of reductant to be provided to the exhaust conduit 238.The process 600 also includes adjusting, at block 606, the positions of the valves 224 of the first branch 218, the second branch 220, and the third branch 222 by the controller 206 (e.g., first branch module 512, by the second branch module 514, by the third branch module 516, etc.). The positions of the valves 224 are adjusted based on the target reductant flow rate determined by the controller 206.The target reductant flow rate, Q Target; the maximum reductant flow rate, Q 1, possible by the flow restrictor 226 of the first branch 218; the maximum reductant flow rate, Q 2, possible by the flow restrictor 226 of the second branch 220; and the maximum reductant flow rate, Q 3, possible by the flow restrictor 226 of the third branch 222 are known to the controller 206. For example, Q Target may be received from an external system (e.g., from a motor control unit, etc.), and Q 1, Q 2, and Q 3 may be programmed into the controller 206. By controlling which valves 224 are open and thus which flow restrictors 226 receive the flow and provide the flow to the exhaust manifold 228, the controller 206 controls a turndown ratio of the dosing module 214. In an exemplary embodiment, the dosing module 214 is capable of achieving a turndown ratio of six to one.In an exemplary application, valves 224 are either fully open such that reductant is provided by corresponding flow restrictor 226 at a maximum flow rate, or fully closed such that reductant is not provided by corresponding flow restrictor 226. In this application, only one of the valves 224 is opened at a time. The open valve 224 is selected based on the comparison between the maximum flow rates of the reductant through the flow restrictors 226 and the target flow rate of the reductant.Equations 1-5 illustrate an example application of the controller 206 where the valve 224 of the first branch 218 is opened or remains open and the valves 224 of the second branch 220 and the third branch 222 are closed or remains closed.Equations 6-10 illustrate an example application of the controller 206 where the valve 224 of the second branch 220 is opened or remains open and the valves 224 of the first branch 218 and the third branch 222 are closed or remains closed. In other applications where Q Target is equal to Q 1 the valve 224 of the first branch 218 is opened or remains open and the valves 224 of the second branch 220 and the third branch 222 are closed or remains closed.Equations 11-15 illustrate an example application of the controller 206 where the valve 224 of the third branch 222 is opened or remains open and the valves 224 of the first branch 218 and the second branch 220 are closed or remains closed. In other applications where Q Target is equal to Q 2 the valve 224 of the second branch 220 is opened or remains open and the valves 224 of the first branch 218 and the third branch 222 are closed or remain closed.In other applications, more than one of the valves 224 may be simultaneously opened so that the open valves 224 cooperate to provide Q Target. Equations 16-20 illustrate an example calculation performed by the controller 206 at block 606 to determine a relative position (e.g., where a value of one is fully open and a value of zero is fully closed, etc.), a, of the valve 224 of the first branch 218; a relative position, b, of the valve 224 of the second branch 220; and a relative position, c, of the valve 224 of the third branch 222 based on the target reductant flow rate, Q Target; the maximum reductant flow rate Q 1, which is possible by the flow restrictor 226 of the first branch 218; the maximum reductant flow rate Q 2, which is possible by the flow restrictor 226 of the second branch 220; and the maximum flow rate of reducing agent Q 3, which is possible by flow restrictor 226 of third branch 222. Equation 21 illustrates an example set of values for a, b, and c. Other similar computations may be performed by the controller 206 in block 606 such that other values of a, b, and c may be obtained.In some applications, the positions of the valves 224 are selected based on characteristics (e.g., maximum flow rates, control level, generated swirl, generated turbulence, etc.) of the flow restrictors 226. For example, the maximum flow rates of the flow restrictors 226 may be programmed (e.g., hard-coded, pre-coded, etc.) into the controller 206 (e.g., within the first branch module 512, within the second branch module 514, within the third branch module 516, etc.). In some applications, the positions of the valves 224 are determined based on a minimum level of control of the valves 224. For example, the valve 224 of the first branch 218 may have a minimum control of 0.1 such that a position with a higher degree of accuracy (e.g., 0.01, 0.001, etc.) may not be exactly reached. In an example where the valves 224 have different minimum control degrees (e.g., the minimum control degree of the valve 224 of the first branch 218 is 0.1 and the minimum control degree of the valve 224 of the second branch 220 is 0.01, etc.), the controller 206 may select the position of the valve 224 of the first branch 218 and the valve 224 of the second branch 220 to achieve the reductant target flow rate determined in block 604 as precisely as possible, considering the minimum control degrees of the valves 224. By adjusting the positions of the valves 224, the controller 206 achieves a "coarse" or relatively inaccurate control of the target reductant flow rate. By adjusting the positions of the valves 224 at this location, the controller 206 uses the feedforward control.The process 600 also includes adjusting, at block 608, the speed (e.g., U / min, etc.) of the pump 212 by the controller 206 (e.g., by the second pump module 510, etc.). By adjusting the speed of the pump 212, the controller 206 achieves a "fine" or relatively precise control of the target reductant flow rate. For example, the controller 206 may set the speed of the pump 212 to two thousand U / min. Additionally, the controller 206 may adjust the speed of the pump 212 according to a speed curve or function. In this way, the speed of the pump 212 may gradually increase to a maximum speed and / or the speed of the pump 212 may be modulated.By adjusting the speed of the pump 212 at this location, the controller 206 uses the feedforward control. Additionally or alternatively, instead of varying the speed of the pump 212 to provide relatively precise control of the target reductant flow rate, other mechanisms could be used. For example, a valve connected to a bypass flow path could be opened, whereby a portion of the reductant provided by the pump 212 can bypass one of the valves 224 and flow restrictors 226 and be provided directly into the exhaust manifold 228.The process 600 also includes, at block 610, measuring, by the controller 206 (e.g., by the sensor module 518, etc.), a pressure difference between a pressure measured in the exhaust manifold 228 and a pressure measured in the intake manifold 216 (e.g., measured by the at least one sensor 240, etc.). For example, the measured pressure difference may be between six and three bar. At block 612, the process 600 includes comparing the measured pressure difference to a target pressure difference by the controller 206 (e.g., by the sensor module 518, etc.). In an example embodiment, the target pressure difference is programmed into the controller 206 and selected based on the target flow rate. For example, the controller 206 may determine that at a target flow rate of twenty five milliliters per second, the target pressure difference is 5.3 bar. According to this example, the controller 206 may compare the target pressure difference of 5.3 bar to a measured pressure difference of 4.8 bar and determine that the measured pressure difference is less than the target pressure difference by 0.5 bar. In another example, the controller 206 may determine that the measured pressure difference corresponds to about one hundred eight percent of the target pressure difference. Additionally, the controller 206 may determine a flow rate of the reductant provided to the exhaust conduit 238 by knowing the measured pressure difference.The process 600 may also include adjusting, by the controller 206 (e.g., by the second pump module 510, etc.), the speed of the pump 212 based on the comparison between the measured pressure difference and the target pressure difference at block 614. For example, if the measured pressure difference is greater than the target pressure difference, the controller 206 may reduce the speed of the pump 212. In another example, the controller 206 may increase the speed of the pump 212 when the measured pressure difference is less than the target pressure difference. If the controller 206 determines that the measured pressure difference is equal to the target pressure difference or is within a threshold (e.g., five percent of the target pressure difference, three percent of the target pressure difference, etc.) of the target pressure difference, the speed of the pump 212 may not be changed by the controller 206. By adjusting the speed of the pump 212 at this location, the controller 206 uses the reverse control.The process 600 may also include adjusting, at block 616, the positions of the valves 224 of the first branch 218, the second branch 220, and the third branch 222 by the controller 206 (e.g., by the first branch module 512, by the second branch module 514, by the third branch module 516, etc.) based on the comparison between the measured pressure differential and the target pressure differential. For example, if the measured pressure difference is greater than the target pressure difference, the controller 206 may close or partially close each of the valves 224. In another example, the controller 206 may open or partially open each of the valves 224 when the measured pressure difference is less than the target pressure difference. If the controller 206 determines that the measured pressure difference is equal to or is within a threshold of the target pressure difference, the positions of the valves 224 may not be changed by the controller 206. By adjusting the positions of the valves 224 at this location, the controller 206 uses a reverse control.The process 600 may be implemented to achieve, for example, five percent accuracy (e.g., plus or minus accuracy, etc.) with respect to the measured pressure difference and the target pressure difference when the target pressure difference is greater than one bar. With this accuracy, for example, process 600 may be configured to provide the reductant at a flow rate between one milliliter per second and twelve milliliters per second with an accuracy of five percent through nozzle 230 of exhaust conduit 238. If the process 600 is implemented with a multiple of the flow restrictors 226 that provide the reductant into the exhaust manifold 228, the accuracy of the process 600 is not significantly degraded.FIG. 7 illustrates numerous flow and pressure difference curves for pump 212. Each of the curves may be achieved by different configurations (e.g., different sizes, different rated powers, etc.) of the pump 212. The controller 206 is programmed with the curve corresponding to the configuration of the pump 212. In this way, the controller 206 may determine the flow rate or pressure differential by knowing the flow rate or pressure differential. In process 600, when the target flow rate is determined in block 604, the controller 206 may determine the target pressure difference by using the corresponding ones.V. CONSTRUCTION OF EXEMPLARY EMBODIMENTSAlthough this document contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. In contrast, various features described in the context of a single implementation may also be implemented in multiple implementations separately or in any suitable sub-combination. Additionally, although features may be described as acting in certain combinations and also initially claimed as such, one or more features from a claimed combination may in some cases be excluded from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.As used herein, the terms "substantially," "about," and similar terms are intended to have a broad meaning that is consistent with common and accepted use by those skilled in the art to which this disclosure pertains. It will be apparent to those skilled in the art having the benefit of this disclosure that these terms are intended to allow a description of certain features described and claimed without limiting the scope of these features to the exact numerical ranges provided. Accordingly, these terms are to be construed to indicate that insubstantial or insubstantial modifications or alterations to the described and claimed subject matter are to be considered within the scope of the invention as recited in the appended claims.The terms "coupled," "connected," and the like, as used herein, mean directly or indirectly connecting two components together. Such a connection can be made in a location-bound (e.g. permanent) or movable (e.g. removable or releasable) manner. Such joining may be achieved by integrally forming the two components or the two components and all additional intermediate components together as a unitary body, the two components or the two components and any additional intermediate components being secured together.The terms "fluidly coupled" or "in fluid communication" and the like, as used herein, mean that the two components or objects have a path formed between the two components or objects in which a fluid, for example, water, air, gaseous reductant, gaseous ammonia, etc., can flow, either with or without intervening components or objects. Examples of fluid couplings or configurations for enabling fluid communication may include tubes, channels, or any other suitable components for enabling a fluid to flow from one component to another.It is important to note that the structure and arrangement of the system shown in the various exemplary implementations are merely illustrative and not restrictive. It is desired that all changes and modifications that fall within the spirit and / or scope of the described implementations be protected. It should be understood that some features are not mandatory, and that implementations lacking the various features may be considered to be within the scope of the application, the scope being defined by the following claims. When the phrase "part" or "portion" is used, the element may include a part / portion and / or the entire element, unless specifically stated otherwise.

Claims

A dosing module (214; 112) comprising: an intake manifold (216) configured to selectively receive reductant from a pump (212); an exhaust manifold (228) configured to selectively provide the reductant to a nozzle (230); a first branch (218) coupled to the intake manifold and the exhaust manifold, the first branch configured to selectively provide the reductant to the exhaust manifold from the intake manifold, the first branch comprising a first flow restrictor (226) configured to restrict the reductant when the reductant is provided to the exhaust manifold; and a second branch (220) coupled to the intake manifold and the exhaust manifold, the second branch configured to selectively provide the reductant from the intake manifold to the exhaust manifold separately from the first branch, the second branch including a second flow restrictor (226) configured to restrict the reductant when the reductant is provided to the exhaust manifold.The dosing module of claim 1, wherein: the first branch (228) further comprises a first valve (224) actuatable between a first position in which the first branch provides the reductant to the exhaust manifold from the intake manifold and a second position in which the first branch does not provide the reductant to the exhaust manifold from the intake manifold; and the second branch (228) further comprises a second valve (224) actuatable between a first position in which the second branch provides the reductant to the exhaust manifold from the intake manifold and a second position in which the second branch does not provide the reductant to the exhaust manifold from the intake manifold.The metering module of claim 1 or claim 2, wherein: the first restrictor (226) comprises a first orifice having a first diameter; the second restrictor (226) comprises a second orifice having a second diameter; and the first diameter is different than the second diameter.The dosing module of claim 1, further comprising: a first valve (224) actuatable between a first position in which the first branch (218) provides the reductant to the exhaust manifold (228) from the intake manifold (216) and a second position in which the first branch does not provide the reductant to the exhaust manifold from the intake manifold; at least one sensor (240) coupled to the intake manifold and the exhaust manifold, the at least one sensor configured to measure a first pressure in the intake manifold and a second pressure in the exhaust manifold; A controller (206) communicatively coupled to the pump (212), the first valve (224), and the at least one sensor (240), the controller comprising: a first module programmed to receive a measurement of the first pressure and a measurement of the second pressure from the at least one sensor and compare the measurement of the first pressure and the measurement of the second pressure to determine a pressure difference; a second module programmed to determine a measured flow rate of the reductant based on the pressure difference; a third module programmed to receive a dosing command; a fourth module programmed to determine a target flow rate of the reductant based on the dosing command; a fifth module programmed to compare the measured flow rate to the target flow rate; and a sixth module programmed to control a speed of the pump and / or operation of the first valve based on a comparison between the measured flow rate and the target flow rate.The dosing module of any one of claims 1 to 4, further comprising a purging leg (306) coupled to the intake manifold (216) and the exhaust manifold (228), the purging leg configured to provide the reductant from the intake manifold to the exhaust manifold selectively separately from the first branch (218) and the second branch (220), the purging leg not comprising a flow restrictor configured to restrict the reductant when the reductant is provided to the exhaust manifold.The dosing module of any of claims 1 to 4, further comprising an intake branch (310) coupled to the intake manifold (216), the intake branch configured to receive the reductant from a tank (208) and selectively provide the reductant to the intake manifold such that the reductant is provided to the pump (212) via the intake manifold.The dosing module of any one of claims 1 to 4, wherein the inlet manifold (216), the outlet manifold (228), the first branch (218), and the second branch (220) are structurally integrated into a combined manifold (300).The dosing module of claim 7, further comprising a reductant passage (318) structurally integrated with the combined manifold (300), the reductant passage configured to receive the reductant from a tank (208) and selectively provide the reductant to the pump (212).A reductant delivery system (200) comprising: a tank (208) configured to contain reductant; a nozzle (230) configured to selectively provide the reductant into an exhaust conduit (238); a first pump (212) configured to selectively draw the reductant from the tank; an intake manifold (216) configured to selectively receive the reductant from the first pump; an exhaust manifold (228) configured to selectively provide the reductant to the nozzle; a first branch (216) coupled to the intake manifold and the exhaust manifold, the first branch configured to selectively provide the reductant from the intake manifold to the exhaust manifold, the first branch comprising: a first valve (224) operable between an open position in which the reductant from the intake manifold is provided to the exhaust manifold through the first branch and a closed position in which the reductant from the intake manifold is not provided to the exhaust manifold through the first branch; and a first flow restrictor (226) configured to restrict the reductant when the reductant is provided to the exhaust manifold through the first branch; and a second branch (220) coupled to the intake manifold (216) and the exhaust manifold (228), the second branch configured to selectively provide the reductant to the exhaust manifold from the intake manifold, the second branch comprising: a second valve (224) operable between an open position in which the reductant is provided to the exhaust manifold from the intake manifold through the second branch and a closed position in which the reductant is not provided to the exhaust manifold from the intake manifold through the second branch; and a second flow restrictor (226) configured to restrict the reductant when the reductant is provided to the exhaust manifold through the second branch.The reductant delivery system of claim 9, further comprising: an air supply (235) configured to supply air; a second pump (234) configured to selectively draw the air from the air supply to provide the air to the nozzle (230); wherein the nozzle (230) is configured to mix the reductant from the exhaust manifold (228) and the air from the second pump (234) to form a reductant-air mixture; and wherein the nozzle is configured to provide the reductant-air mixture into the exhaust conduit (238).The reductant delivery system of claim 9 or claim 10, further comprising at least one sensor (240) coupled to the intake manifold and the exhaust manifold, wherein the at least one sensor is configured to measure a first pressure in the intake manifold and a second pressure in the exhaust manifold.The reductant delivery system of claim 11, further comprising a controller (206) communicatively coupled to the first pump (212), the first valve (224), and the at least one sensor (240), the controller comprising: a first module programmed to receive a measurement of the first pressure and a measurement of the second pressure from the at least one sensor and compare the measurement of the first pressure and the measurement of the second pressure to determine a pressure difference; and a second module programmed to determine a measured flow rate of the reductant based on the pressure difference.The reductant delivery system of claim 12, wherein the controller (206) further comprises: a third module programmed to receive a dosing command; a fourth module programmed to determine a target flow rate of the reductant based on the dosing command; and a fifth module programmed to compare the measured flow rate to the target flow rate.The reductant delivery system of claim 13, wherein the controller (206) further comprises a sixth module programmed to control a speed of the first pump (212) based on the comparison between the measured flow rate and the target flow rate.The reductant delivery system of claim 14, wherein the controller (206) further comprises a seventh module programmed to control the first valve based on the comparison between the measured flow rate and the target flow rate.A combined manifold (300) comprising: an intake manifold (216) configured to selectively receive reductant from a pump (212); an exhaust manifold (228) configured to selectively provide the reductant to a nozzle (230); a first branch (218) coupled to the intake manifold and the exhaust manifold, the first branch configured to selectively provide the reductant to the exhaust manifold from the intake manifold, the first branch comprising a first flow restrictor (226) configured to restrict the reductant when the reductant is provided to the exhaust manifold; and a second branch (220) coupled to the intake manifold, the second branch configured to receive the reductant from a tank and selectively provide the reductant to the intake manifold such that the reductant is provided to the pump via the intake manifold; wherein the intake manifold, the exhaust manifold, the first branch, and the second branch are structurally integrated.The combined manifold of claim 16, wherein the first branch (218) further comprises a first valve (224) actuatable between a first position, in which the first branch provides the reductant from the intake manifold (216) to the exhaust manifold (228), and a second position, in which the first branch does not provide the reductant from the intake manifold to the exhaust manifold.The combined manifold of claim 16 or claim 17, further comprising a purge leg (306) structurally integrated with the intake manifold, the exhaust manifold, the first branch, and the second branch, the purge leg coupled to the intake manifold and the exhaust manifold, the purge leg configured to selectively provide the reductant from the intake manifold to the exhaust manifold separately from the first branch and separately from the second branch, the purge leg not comprising a flow restrictor configured to limit the reductant when the reductant is provided to the exhaust manifold.The combined manifold of claim 16 or claim 17, further comprising a reductant passage (318) structurally integrated with the intake manifold, the exhaust manifold, the first branch, and the second branch, wherein the reductant passage is configured to receive the reductant from the tank (208) and provide the reductant to the pump (212), and the reductant passage is separate from the intake manifold and the exhaust manifold.

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