WO2015137940A1

WO2015137940A1 - System and method for controlling emissions

Info

Publication number: WO2015137940A1
Application number: PCT/US2014/024536
Authority: WO
Inventors: Colin L. NORRIS; Paul D. BORISUK
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2014-03-12
Filing date: 2014-03-12
Publication date: 2015-09-17
Anticipated expiration: 2016-09-12

Abstract

A system and method are disclosed for controlling the emissions from an engine system, the method including determining the water vapor content of an intake flow into a combustion chamber of an engine, determining an operating mode and condition of the engine, identifying the appropriate combustion references associated with the operating mode and condition of the engine, interpolating command parameter settings from the identified combustion references, using the water vapor content of the intake flow, and adjusting one or more command parameters according to the interpolated command parameter settings. The system includes an engine, a humidity sensor in communication with an intake flow into the engine, at least one combustion reference associated with command parameters that affect a combustion process, and a controller in communication with the engine and the humidity sensor and structured to perform the operations of the method.

Description

SYSTEM AND METHOD FOR CONTROLLING EMISSIONS

TECHNICAL FIELD

[0001] The present disclosure generally relates to emission controls for internal combustion engine systems.

BACKGROUND

[0002] Modern internal combustion engines must meet stringent emission standards that include limits on the amount of soot, nitrogen oxides (hereafter "NO_x" to include nitric oxide (NO) and nitrogen dioxide (N0₂)), carbon monoxide, and other pollutants that may be emitted. Many engines now utilize aftertreatment systems to reduce engine-out emissions to allowable regulatory levels before release to the atmosphere, particularly lean-burn engine systems such as diesel engines. Such aftertreatment systems may include one or more of a diesel oxidation catalyst ("DOC"), three-way catalyst, lean NO_x catalyst, selective catalytic reduction ("SCR") catalyst, a filtration component, either catalyzed or uncatalyzed (e.g., a diesel particulate filter ("DPF")), and a cleanup catalyst (e.g., an ammonia oxidation catalyst). SCR systems may include the introduction of a reductant, such as anhydrous ammonia, aqueous ammonia, or water-based urea solution, into the exhaust system. Where urea is used, the ammonia produced by hydrolysis of the urea reacts with the NO_x emissions and is converted into nitrogen and water within a catalytic converter. Consequently, engine systems using SCR require the continuous addition of the reductant to control NO_x emissions, which in turn reduces other pollutants. Accordingly, there remains a need for further contributions in this area of technology.

SUMMARY

[0003] A system and method are disclosed for controlling the emissions from an engine system, the method including determining the water vapor content of an intake flow into a combustion chamber of an engine, determining an operating mode and condition of the engine, identifying the appropriate combustion references associated with the operating mode and condition of the engine, interpolating command parameter settings from the identified combustion references, using knowledge of the water vapor content of the intake flow, to control emissions generated by the engine, and adjusting one or more command parameters according to the interpolated command parameter settings. The system includes an engine including a combustion chamber in fluid communication with an intake manifold and an exhaust system, thereby enabling an intake flow into the combustion chamber via the intake manifold, a humidity sensor in communication with the intake flow, at least one combustion reference associated with command parameters that affect the combustion process within the engine in operation, and a controller in communication with the engine and the humidity sensor, the controller structured to perform the operations of the method.

[0004] This summary is provided to introduce a selection of concepts that are further described below in the illustrative embodiments. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a schematic block diagram of an embodiment of an engine system according to the present disclosure; and

[0006] FIG. 2 is a schematic flow diagram of a method for controlling emissions from an engine system according to the present disclosure.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0007] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the invention as illustrated therein as would normally occur to one skilled in the art to which the invention relates are contemplated herein.

[0008] Internal combustion engines generate emissions of pollutants during a combustion process by the oxidation of a hydrocarbon fuel. The pollutants generated may include such regulated emissions as NO_x, carbon monoxide, partial or unburned hydrocarbons, and particulate matter among others. For simplicity and unless specified otherwise, the term "emissions" hereinafter refers to any regulated pollutants emitted by an engine. One particular emission, NO_x, is generated during the combustion process by the oxidation of free nitrogen from the ambient air, particularly in the presence of excess amounts of oxygen. The formation of NO_x emissions increases significantly when the flame temperature of the combustion process exceeds the NO_x formation temperature, which is approximately 1500°C. Further, the lebngth of time that the combustion process is above the NO_x formation temperature affects the amount of NO_x and other emissions produced.

[0009] The presence of water vapor in the combustion process may reduce the formation of NO_x and other emissions. Because water vapor has a greater specific heat than nitrogen or oxygen, water vapor present in the combustion process absorbs more of the heat generated by the combustion process than air alone, thereby lowering the temperature of the combustion process, which reduces NO_x formation. Consequently, higher concentrations of water vapor present in the combustion process (i.e., higher relative humidity of the combustion gases) lower the NO_x emissions produced by the engine. Conversely, lower concentrations of water vapor present in the combustion process (i.e., lower relative humidity of the combustion gases) increase the NO_x emissions produced by the engine by lowering the specific heat of the air-fuel mixture, which results in higher flame temperatures exceeding the NO_x formation temperature. Moreover, the conditions affecting the formation of one type of emission also affect the formation of other emissions, such as carbon monoxide, partial or unburned hydrocarbons, and particulate matter.

[0010] Diesel engines tend to produce larger amounts NO_x emissions than gasoline engines because, while gasoline engines run on a nearly stoichiometric ratio of air to fuel, diesel engines generally run a lean air- fuel mixture, meaning the mixture includes much more oxygen than needed to burn the available fuel. Aftertreatment systems, such as SCR systems, may be combined with diesel engines to treat the exhaust gas generated by the combustion process to reduce the NO_x and other emissions into free nitrogen and water. However, SCR systems require the continuous addition of a reductant, commonly referred to as diesel exhaust fluid ("DEF"). Where urea is used as the DEF in a SCR system, the NO_x emissions are catalyzed into diatomic nitrogen, carbon dioxide, and water. Accordingly, a supply of DEF must be maintained and introduced into the flow of exhaust gas to control NO_x and other emissions to desired levels.

[0011] An engine system 100 may include an engine 10 fluidly coupled to an aftertreatment system 30 as shown in FIG. 1. The engine 10 may be any type of internal combustion engine, including at least a diesel, gasoline, or natural gas engine, and/or combinations thereof and may comprise a portion of a powertrain for a vehicle. Further, the engine 10 may comprise a portion of a stationary application such as a power generation or pumping application. The engine 10 may include a plurality of combustion cylinders or chambers 12 structured to enable and contain a combustion process, in which a mixture of fuel and air may be burned to produce motive power for the vehicle via the mechanics of the engine 10. The engine 10 may include a plurality of valves moveably connected to the combustion chambers 12 to control the flow of combustion gases into and exhaust gases out of the chambers 12. The engine 10 may further include a plurality of injectors in fluid communication with the chambers 12 to introduce a prescribed amount of fuel into the chambers 12 to enable the combustion process.

[0012] The engine 10 may include an intake manifold 20 in fluid communication with the chambers 12, such that the intake manifold 20 enables an intake flow of ambient air into each of the chambers 12 via the valves. The intake flow may include ambient air and other gases as described further herein. The engine 10 may further include an exhaust system 22 in fluid communication with the chambers 12, such that the exhaust system 22 enables the flow of post-combustion exhaust gases from each of the chambers 12 via the valves. The engine 10 may further include a compressor 18 fluidly connected to the intake manifold 20. The compressor 18 may be structured to draw in ambient air from the environment and force the induction of the air under pressure into the intake manifold. The compressor 18 may be a supercharger, in which the compressor 18 is driven by mechanical connection to the engine (e.g., by a belt connected to a crankshaft). Alternatively, the compressor 18 may be a turbocharger having a turbine 36, in which the compressor 18 is driven by exhaust gases routed through the turbine 36 as shown in FIG. 1. In at least one embodiment, the compressor 18 may include both a supercharger and a turbocharger in fluid communication with the intake manifold 20.

[0013] In at least one embodiment according to the present disclosure as shown in FIG. 1, the engine system 100 may include a controller 40 in communication with the engine 10, the controller 40 structured to perform certain operations, for example to reduce the emission of certain compounds from the engine 10 in operation. The controller 40 may be structured to control command parameters of the engine 10, which may include those parts of the engine 10 that may be controlled with an actuator activated by the controller 40. In certain embodiments, the controller 40 may be a portion of a processing subsystem including one or more computing devices having memory, processing, and communication hardware. The controller 40 may be a single device or a distributed device, and the functions of the controller 40 may be performed by hardware or software. The controller 40 may comprise digital circuitry, analog circuitry, or a hybrid combination of both of these types. The controller 40 may include one or more Arithmetic Logic Units (ALUs), Central Processing Units (CPUs), memories, limiters, conditioners, filters, format converters, or the like which are not shown to preserve clarity.

[0014] Further, the controller 40 may be programmable, an integrated state machine, or a hybrid combination thereof. In at least one embodiment, the controller 40 is programmable and executes algorithms and processes data in accordance with operating logic that is defined by programming instructions such as software or firmware. Alternatively or additionally, operating logic for the controller 40 may be at least partially defined by hardwired logic or other hardware. It should be appreciated that the controller 40 may be exclusively dedicated to reducing emissions from the engine 10 or may further be used in the regulation, control, and /or activation of one or more other subsystems or aspects of the engine system 100.

[0015] In certain embodiments, the controller 40 includes one or more modules structured to functionally execute the operations of the controller 40. The description herein including modules emphasizes the structural independence of the aspects of the controller 40, and illustrates one grouping of operations and responsibilities of the controller 40. Other groupings that execute similar overall operations are understood within the scope of the present application. Modules may be implemented in hardware and/or software on a non-transient computer readable storage medium, and modules may be distributed across various hardware or software components.

[0016] Certain operations described herein include operations to interpret one or more parameters. Interpreting, as utilized herein, includes receiving values by any method known in the art, including at least receiving values from a datalink or network communication, receiving an electronic signal (e.g., a voltage, frequency, current, or pulse-width modulation (PWM) signal) indicative of the value, receiving a software parameter indicative of the value, reading the value from a memory location on a non-transient computer readable storage medium, receiving the value as a run-time parameter by any means known in the art, and/or by receiving a value by which the interpreted parameter can be calculated, and/or by referencing a default value that is interpreted to be the parameter value.

[0017] The engine 10 may include a humidity sensor 42 in communication with the controller 40. The humidity sensor 42 may be structured to measure the water vapor content (i.e., absolute humidity) of the intake flow into the chambers 12 of the engine 10 at a location within the engine system 100 and to convert the measurement of humidity into a signal that can be interpreted by the controller 40, which may adjust the command parameters of the engine 10 accordingly. In at least one embodiment, the humidity sensor 42 may be in communication with the intake manifold 20 as shown in FIG. 1. Alternatively, the humidity sensor 42 may be in communication with an inlet to the compressor 18 as indicated by humidity sensor 42a. In another embodiment, the humidity sensor 42 may be in communication with the ambient air at or near the engine 10 as further shown in FIG. 1.

[0018] In at least one embodiment according to the present disclosure, the humidity sensor 42 may be a water vapor content measurement taken at a location remote from the engine 10. In such an embodiment, a signal carrying the water vapor content information for a selected location may be transmitted to the controller 40 via telematics, which includes sending, receiving and storing information via telecommunications. For example, the water vapor content measurement may be taken at a central location within a facility, and a signal carrying the water vapor content information may be transmitted to the engine 10 operating at or near the facility. In at least one embodiment, the humidity sensor 42 may be a virtual, proxy, inferential, or surrogate sensor. In such embodiments, the water vapor content may be determined analytically or empirically using information available from other sensor measurements and/or process parameters of the engine 10 to calculate the water vapor content of the intake flow.

[0019] In at least one embodiment according to the present disclosure, the engine system 100 may include an aftertreatment system 30, which may include catalytic and/or filtration components known in the art. Example aftertreatment systems 30 may include, without limitation, oxidation catalysts (e.g., a diesel oxidation catalyst ("DOC"), NO_x treatment components (e.g., three-way catalyst, lean NO_x catalyst, selective catalytic reduction ("SCR") catalyst, etc.), a filtration component (either catalyzed or uncatalyzed, e.g., a diesel particulate filter ("DPF"), and a cleanup catalyst (e.g., an ammonia oxidation catalyst). In certain embodiments, the aftertreatment system 30 is a SCR system structured to catalyze NO_x into diatomic nitrogen, carbon dioxide, and water using DEF as a reductant. The DEF may be stored and dispensed from a doser 34, having a finite capacity, in communication with the exhaust gas as shown in FIG. 1. The limited capacity of the doser 34, particularly where the engine 10 is used in a vehicle, means that the doser 34 must be periodically refilled with DEF. In at least one embodiment, the doser 34 may include more than one doser 34 having a finite combined capacity. In certain embodiments, the aftertreatment system 30 may be structured to catalyze other emissions in addition to NO_x, such as carbon monoxide and partial or unburned hydrocarbons.

[0020] As shown in FIG. 1, the engine 10 may include an exhaust gas regeneration ("EGR") system 32 that recirculates via the exhaust system 22 at least a portion of the exhaust gas generated in the combustion chambers 12 back into the chambers 12 via the intake manifold 20. A control valve within the EGR system 32, which may be in communication with the controller 40, may regulate and synchronize the flow of exhaust gas into the intake manifold 20. Introducing exhaust gas, which has a lower fraction of oxygen, into the chambers 12 lowers the combustion temperature of the combustion process, which may reduce the amount of emissions generated during combustion. Also, exhaust gas, being comprised of mostly carbon dioxide and water vapor, has a higher specific heat than the ambient air introduced into the chambers 12, thereby further lowering peak combustion temperatures and emissions formation. In such an embodiment, the humidity sensor 42 may be disposed within the intake manifold 20 at a location where the recirculated exhaust gas is sufficiently mixed with the ambient air introduced into the intake manifold 20. Consequently, the humidity sensor 42 measures the humidity resulting from the mixing of the water vapor in the ambient air and the water vapor in the exhaust gas.

[0021] In at least one embodiment of the present disclosure, the compressor 18 of the engine 10 may include a variable geometry turbocharger ("VGT") having the turbine 36. The VGT may enable exhaust gas recirculation under certain operating conditions by adjusting an aspect ratio of the VGT relative to the speed of the engine 10. The aspect ratio may be adjusted by opening and closing of inlet guide vanes. A small aspect ratio at high engine speeds may choke the intake flow into and exhaust gas flow out of the chambers 12, leading to high exhaust system pressures that may exceed the pressure of intake manifold (i.e., backpressure), thereby causing a portion of the exhaust gas to remain in the chambers 12 instead of exiting via the exhaust system 22. Though excessive engine backpressure may be detrimental to overall fuel efficiency, exhaust gas recirculation, at least during transient events (e.g., gear changes), may be sufficient to reduce emissions below regulatory requirements. [0022] The controller 40 may include a plurality of combustion references 44 associated with the command parameters that affect and control the combustion process within the engine 10. The combustion references 44 are tables of command parameter settings used by the controller 40 to determine and command the appropriate command parameter settings for a given operating condition of the engine 10. The command parameters may include subsystems or parts of the engine 10 that may be controlled with an actuator activated by the controller 40. As a non-limiting example, the command parameters may include pilot injection fueling and timing, main injection timing, post injection fueling and timing, fuel pressure, total charge flow into the intake manifold 20, EGR fraction, indicated torque- to-fuel ratio, maximum indicated torque, target NO_x, and target ammonia slip.

[0023] The combustion references 44 may be visualized as three-dimensional surfaces that define the relationship between a specific command parameter and a given engine operating conditions of the engine 10. The engine operating conditions may be defined by operating parameters. Operating parameters may include, but not be limited to, the ambient temperature, the humidity of the intake air, ambient pressure, and air density at the inlet of compressor 18. Accordingly, the combustion references 44 enable the controller 40 to adjust the command parameters to achieve the desired operation of the engine 10 based on the specific operating parameters that define the conditions under which the engine 10 is operating.

[0024] The controller 40 may further include combustion references 44 that are specific to certain operating modes of the engine 10. For example, the controller 40 may include different combustion references 44 for certain operating conditions depending on whether the engine 10 is in a normal steady- state (i.e., base) mode, an engine fault-based protection mode, a coolant temperature -based heat rejection reduction mode, or aftertreatment-based thermal management mode. These exemplary modes are not exclusive. Moreover, the controller 40 may include different combustion references 44 for a given compressor inlet density or ambient air pressure. The controller 40 may include more than one combustion reference 44 for a given command parameter depending on the current operating mode and/or operating conditions of the engine 10. Consequently, each mode and/or condition may have a set of combustion references 44 for a particular operating condition depending on the given operating mode of the engine 10.

[0025] An example a combustion reference 44 may include command parameter settings, such as main timing, for a given engine speed and load. In at least one embodiment, a proxy for the engine load may be included in the combustion reference 44, such as total fueling or torque demand. An alternative combustion reference 44 may include a prescribed torque-to-fuel ratio for a given engine speed and commanded torque. The controller 40 may interpolate between the combustion references 44 associated with a given mode and/or condition to determine the appropriate parameter settings for the current operating condition. By interpolating between combustion references 44, the controller 40 may set the command parameters to attain the desired performance criteria of the engine 10. As a non- limiting example, the desired performance criteria may be fuel efficiency and/or minimum emissions.

[0026] As a non- limiting example, the controller 40 may include a first set 144 of combustion references 44 for a base engine mode at different inlet air densities associated with engine operating altitude breakpoints (e.g., sea level, 5,000 feet (ft), and 10,000 ft) and at different humidity levels (e.g., 10%, 50%, and 90%) as measured by the humidity sensor 42. In operation, the controller 40 may interpret humidity level and altitude inputs, determine the appropriate command parameters settings, and adjust the command parameters accordingly to control the engine 10 by interpolating between the combustion references 44 comprising the first set 144 depending on the current altitude and humidity level. For instance, the controller 40 may interpolate a different main injection timing command parameter to account for a decreasing humidity level and an increasing altitude condition. The controller 40 may further include a second set 244 of combustion references 44 for a heat rejection engine mode at the same inlet air densities associated with the same altitude breakpoints (i.e., sea level, 5,000 ft, and 10,000 ft of altitude) and at the same humidity levels (i.e., 10%, 50%, and 90%). Under conditions where a rise in engine coolant temperature indicates that the engine 10 should change from the base mode to the heat rejection engine mode, the controller 40 may use the second set 244 of combustion references 44 to determine and adjust the appropriate command parameters by interpolating between the combustion references 44 comprising the second set 244 depending on the current altitude and humidity level. Moreover, in certain embodiments, the controller 40 may interpolate between the first set 144 and the second set 244 of combustion references 44 to determine and adjust the appropriate command parameters for operating conditions that fall between the breakpoints included in the combustion references 44. Accordingly, operation of the engine 10 may be continuously tuned to the current operating conditions and mode.

[0027] In at least one embodiment according to the present disclosure, the controller 40 may include one or more combustion references 44 that include water vapor content of the intake flow. In such an embodiment, the combustion references 44 enable the controller 40 to adjust one or more actuators associated with the appropriate command parameters to affect the combustion process, and thereby affect the generation of emissions, based on the humidity level of the intake flow introduced into the combustion chambers 12. Accordingly, the command parameters within the combustion references 44 may be preselected to reduce or maintain emissions levels as the water vapor content of the intake flow varies. The water vapor content of the intake flow may be measured using the humidity sensor 42. As described herein, the quantity of NO_x and other emissions generated by the combustion process within the combustion chambers 12 may increase as the amount of water vapor (i.e., humidity level) in the intake flow decreases. In such an embodiment, the combustion parameters of pilot injection fueling and timing, main injection timing, post injection fueling and timing, fuel pressure, total charge flow into the intake manifold 20, EGR fraction, indicated torque-to-fuel ratio, maximum indicated torque, target NO_x, and/or target ammonia slip may be adjusted to reduce NO_x and other emissions and/or engine power, while further limiting or maintaining the consumption of DEF. Conversely, at increased humidity levels emissions could be maintained at nominal levels while further reducing fuel consumption, thereby increasing the efficiency of the engine system 100 and reducing or maintaining the consumption of DEF. Consequently, the controller 40 may use input from the humidity sensor 42 to limit the formation of NO_x and other emissions in the engine 10 during operation by adjusting the command parameters in accordance with the combustion references 44 associated with the operating conditions of the engine 10 at the measured humidity level.

[0028] In certain embodiments, the engine system 100 reduces the amount of DEF required to maintain the emissions of NO_x from the engine system 100 within prescribed regulatory limits. Whereas conventional engines using SCR to meet regulatory emissions requirements depend upon the introduction of DEF into the exhaust gas to reduce the NO_x generated by such an engine system, the engine system 100 may reduce the amount of DEF required at a given engine operating condition by reducing the amount of NO_x emissions generated within the chambers 12, thereby lowering the operating costs of the engine system 100. Likewise, because the amount of DEF required at a given engine operating condition is reduced, the engine system 100 may enable a reduction of DEF doser capacity or, alternatively, reduce the frequency of replenishing the stored DEF for a given doser capacity. Reducing doser capacity may lower the cost of the engine system 100. Further, reducing the frequency of doser refilling may lower the operating costs of the engine system 100 by reducing the consumption of DEF, the maintenance labor to refill the doser capacity, and the maintenance downtime when the engine system 100 is not in operation. Consequently, the engine system 100 may be less costly to manufacturer and operate than conventional engine systems.

[0029] The schematic flow description that follows provides an illustrative embodiment of a method to control the emissions from an engine. Operations illustrated are understood to be exemplary only, and the operations may be combined or divided, and added or removed, as well as re-ordered in whole or part, unless stated explicitly to the contrary herein. Certain operations illustrated may be implemented by a computer executing a computer program product on a non-transient computer readable storage medium, where the computer program product comprises instructions causing the computer to execute one or more of the operations, or to issue commands to other devices to execute one or more of the operations.

[0030] As shown in FIG. 2, an example method 200 includes an operation 210 of determining the water vapor content of the intake flow into the chambers 12 of the engine 10. The water vapor content may be determined by measuring the humidity of the intake flow. Such a humidity measurement may be made interpreting the humidity sensor 42 in communication with the intake flow. The method 200 may include an operation 220 of determining the current operating mode and conditions of the engine 10. The method 200 may further include an operation 230 of identifying the appropriate combustion references 44 associated with the current operating mode and conditions of the engine 10 using the controller 40. The method 200 may further include an operation 240 of interpolating between the identified combustion references 44 to calculate suitable command parameter settings for control of emissions generated by the engine 10 at the determined water vapor content of the intake flow using the controller 40. The method 200 may further include an operation 250 of adjusting the command parameters to the calculated command parameter settings using the controller 40 to activate the command parameters. The operation 250 may include decreasing an amount of a diesel exhaust fluid introduced into an aftertreatment system of the engine as the water content of the intake flow increases. The operation 250 may further include introducing exhaust gas generated in the combustion chamber into the intake flow.

[0031] As is evident from the figure and text presented above, a variety of embodiments according to the present disclosure are contemplated. Such system embodiments may be employed in a variety of methods, processes, procedures, steps, and operations as a means of controlling the emissions from an engine. While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described. Those skilled in the art will appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method of controlling emissions generated by an engine, the method comprising:

determining a water vapor content of an intake flow into a combustion chamber of an engine; determining an operating mode and condition of the engine;

identifying one or more combustion references associated with the operating mode and condition of the engine, the combustion references including command parameter settings;

interpolating command parameter settings from the identified combustion references, using the water vapor content of the intake flow, to control emissions generated by operation of the engine; and adjusting one or more command parameters for operation of the engine according to the interpolated command parameter settings.

2. The method of claim 1, wherein the engine includes a controller structured to perform any one or more of the operations recited in claim 1.

3. The method of claim 1, wherein the water vapor content of the intake flow is determined in an intake manifold in fluid communication with the combustion chamber.

4. The method of claim 1, wherein the water vapor content of the intake flow is determined in an inlet of a compressor in fluid communication with the combustion chamber.

5. The method of claim 1, wherein the water vapor content of the intake flow is determined for the local ambient conditions at or near the engine.

6. The method of claim 1, wherein the water vapor content of the intake flow is determined from telematics information communicated to the engine.

7. The method of claim 1 , wherein the operation of adjusting one or more command parameters includes decreasing or maintaining an amount of a diesel exhaust fluid introduced into an aftertreatment system of the engine as the water vapor content of the intake flow increases.

8. The method of claim 7, wherein the aftertreatment system is a selective catalytic reduction system.

9. The method of claim 1 , wherein the operation of adjusting one or more command parameters includes introducing exhaust gas generated in the combustion chamber into the intake flow.

10. The method of claim 1 , wherein the one or more command parameters are selected from the group consisting of pilot injection fueling, pilot injection timing, main injection timing, post injection fueling, post injection timing, fuel pressure, total intake flow, exhaust gas recirculation fraction, indicated torque-to-fuel ratio, maximum indicated torque, target NO_x, and target ammonia slip.

1 1. A system for controlling emissions from an engine, the system comprising:

an engine including a combustion chamber in fluid communication with an intake manifold enabling an intake flow into the combustion chamber via the intake manifold;

a humidity sensor in communication with the intake flow;

at least one combustion reference associated with command parameters that affect the combustion process within the engine in operation; and

a controller in communication with the engine and the humidity sensor and structured to perform any one or more of operations including determining a water vapor content of the intake flow; determining an operating mode and condition of the engine; identifying the appropriate combustion references associated with the operating mode and condition of the engine; interpolating command parameter settings from the identified combustion references, using the water vapor content of the intake flow, to control emissions generated by operation of the engine; and adjusting one or more command parameters for operation of the engine according to the interpolated command parameter settings.

12. The system of claim 1 1, wherein the operation of adjusting one or more command parameters includes decreasing or maintaining an amount of a diesel exhaust fluid introduced into an aftertreatment system of the engine as the water vapor content of the intake flow increases.

13. The system of claim 1 1, wherein the operation of adjusting one or more command parameters includes introducing exhaust gas generated in the combustion chamber into the intake flow.

14. The system of claim 1 1, wherein the humidity sensor is in communication with the intake manifold.

15. The system of claim 1 1, the system further comprising:

a doser in fluid communication with an exhaust system that receives an exhaust flow from the combustion chamber, the doser structured to introduce a diesel exhaust fluid into the exhaust flow; and an aftertreatment system that receives the exhaust flow, the aftertreatment system structured to at least partially catalyze a portion of the emissions within the exhaust flow into nitrogen and water.

16. The system of claim 15, wherein the aftertreatment system is a selective catalytic reduction system.

17. The system of claim 1 1, the system further comprising a compressor in fluid communication with the combustion chamber and structured to compress the intake flow, the compressor including an inlet, wherein the humidity sensor is in communication with the inlet of the compressor.

18. The system of claim 17, wherein the compressor is a turbocharger in fluid communication with the exhaust flow, wherein a portion of an exhaust flow generated in the combustion chamber is directed through the turbocharger to generate torque to compress the intake flow.

19. The system of claim 17, wherein the turbocharger is a variable geometry turbocharger.

20. The system of claim 1 1, wherein the one or more command parameters are selected from the group consisting of pilot injection fueling and timing, main injection timing, post injection fueling, post injection timing, fuel pressure, total intake flow, exhaust gas recirculation fraction, indicated torque-to- fuel ratio, maximum indicated torque, target NO_x, and target ammonia slip.