Work vehicle compression ignition power system with intake heat exchanger

The power system includes a compression ignition engine configured to combust intake gas; an intake arrangement configured to intake charge air; an exhaust arrangement to receive a first portion of the exhaust; an EGR arrangement to receive a second portion of the exhaust as EGR gas; a first mixer to selectively mix a first portion of the EGR gas and the charge air as mixed gas; an intake heat exchanger positioned upstream or downstream of the first mixer and respectively configured to receive one of the intake charge air or the mixed gas such that heat is exchanged with engine coolant; a second mixer positioned downstream of the first mixer and the intake heat exchanger and configured to selectively mix a second portion of the EGR gas and the mixed gas to form the intake gas; and an intake manifold configured to direct the intake gas into the engine.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Not applicable.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE DISCLOSURE

This disclosure generally relates to work vehicles, and more specifically to work vehicle power systems and methods.

BACKGROUND OF THE DISCLOSURE

Heavy work vehicles, such as used in the construction, agriculture, and forestry industries, typically include a power system with an internal combustion engine. For many work vehicles, the power system includes a diesel engine that may have higher lugging, pull-down, and torque characteristics for associated work operations. However, diesel and other types of fossil fuel-based engines may generate undesirable emissions.

Ethanol, derived from renewable resources such as corn or sugar cane, has been used as a fuel source to reduce greenhouse gas emissions. Typically, within the general consumer automotive markets, ethanol is blended into gasoline and used by spark ignited engines. However, this type of use and such engines are generally not suitable for use in heavy work applications.

SUMMARY OF THE DISCLOSURE

The disclosure provides a work vehicle compression ignition power system with an intake heat exchanger to facilitate ignition and support operation in a range of conditions.

In one aspect, the disclosure provides a power system for a work vehicle. The power system includes a compression ignition engine configured to receive and combust intake gas to generate mechanical power and exhaust; an intake arrangement configured to intake charge air; an exhaust arrangement configured to receive a first portion of the exhaust generated by the compression ignition engine; an EGR (exhaust gas recirculation) arrangement configured to receive a second portion of the exhaust generated by the compression ignition engine as EGR gas; a first mixer configured to selectively receive and mix a first portion of the EGR gas and the charge air as mixed gas; an intake heat exchanger positioned either upstream of the first mixer or downstream of the first mixer and respectively configured to receive one of the intake charge air or the mixed gas such that heat is exchanged between with engine coolant circulating in the intake heat exchanger and the one of the intake charge air or the mixed gas; a second mixer positioned downstream of the first mixer and the intake heat exchanger and configured to selectively receive and mix a second portion of the EGR gas and the mixed gas to form the intake gas; and an intake manifold configured to receive and direct the intake gas from the second mixer into the compression ignition engine for combustion.

The compression ignition engine is configured to operate with a low cetane fuel.

The compression ignition engine is configured to operate with fuel having a cetane value of less than 40.

The intake heat exchanger is positioned downstream of the first mixer such that the heat is exchanged between with engine coolant circulating in the intake heat exchanger and the mixed gas.

Under a first set of conditions, the intake heat exchanger is configured to heat the mixed gas.

Under a second set of conditions, the intake heat exchanger is configured to cool the mixed gas.

The power system further includes: a first EGR valve configured to control an amount of the first portion of the EGR gas directed to the first mixer; and a second EGR configured to control an amount of the second portion of the EGR gas directed to the second mixer.

The power system further includes a controller coupled to the first EGR valve and the second EGR valve and configured to control the first EGR valve and the second EGR valve such that the intake gas has a temperature such that, upon compression, the intake gas auto-ignites.

The intake arrangement includes at least one compressor configured to receive and compress the intake charge air upstream of the first mixer.

The exhaust arrangement includes at least one turbine driven by the first portion of the exhaust and rotationally coupled to drive the at least one compressor.

The intake arrangement includes two compressors and the exhaust arrangement includes two turbines that collectively form dual turbochargers.

The intake arrangement further includes an interstage cooler positioned in between the two compressors to cool the intake charge air.

The power system further includes a radiator configured to cool the engine coolant.

The EGR arrangement further includes an EGR cooler configured to cool the EGR gas upstream of the first mixer.

The EGR cooler and the intake heat exchangers are separate heat exchangers.

In a further aspect, the disclosure provides a work vehicle with a chassis; a drive assembly supported on the chassis; and a power system supported on the chassis and configured to power the drive assembly. The power system includes: a compression ignition engine configured to receive and combust intake gas to generate mechanical power and exhaust; an intake arrangement configured to intake charge air; an exhaust arrangement configured to receive a first portion of the exhaust generated by the compression ignition engine; an EGR (exhaust gas recirculation) arrangement configured to receive a second portion of the exhaust generated by the compression ignition engine as EGR gas; a first mixer configured to selectively receive and mix a first portion of the EGR gas and the charge air as mixed gas; an intake heat exchanger positioned either upstream of the first mixer or downstream of the first mixer to respectively configured to receive one of the intake charge air or the mixed gas such that heat is exchanged between with engine coolant circulating in the intake heat exchanger and the one of the intake charge air or the mixed gas; a second mixer positioned downstream of the first mixer and the intake heat exchanger and configured to selectively receive and mix a second portion of the EGR gas and the mixed gas to form the intake gas; and an intake manifold configured to receive and direct the intake gas from the second mixer into the compression ignition engine for combustion.

The compression ignition engine is configured to operate with a low cetane fuel.

The compression ignition engine is configured to operate with fuel having a cetane value of less than 40.

The intake heat exchanger is positioned downstream of the first mixer such that the heat is exchanged between with engine coolant circulating in the intake heat exchanger and the mixed gas. Under a first set of conditions, the intake heat exchanger is configured to heat the mixed gas; and under a second set of conditions, the intake heat exchanger is configured to cool the mixed gas.

DETAILED DESCRIPTION

The following describes one or more example embodiments of the disclosed power system and method, as shown in the accompanying figures of the drawings described briefly above. Various modifications to the example embodiments may be contemplated by one of skill in the art. Discussion herein may sometimes focus on the example application of power system in a tractor, but the disclosed power system is applicable to other types of work vehicles and/or other types of engine systems.

Work vehicles may include power systems that typically have diesel engines to produce torque in a wide range of applications, such as long-haul trucks, tractors, agricultural or construction vehicles, surface mining equipment, non-electric locomotives, stationary power generators and the like. Even though such engines may have advantageous energy and performance characteristics, diesel and other types of fossil fuel-based engines may generate undesirable emissions. In contrast, ethanol, derived from renewable resources such as corn or sugar cane, has been used as a fuel source to reduce greenhouse gas emissions. Typically, within the general consumer automotive markets, ethanol is blended into gasoline and used by spark ignited engines. However, this type of use and such engines are typically not suitable for in heavy work applications.

Generally, certain non-diesel fuels that have desirable sourcing, performance, and/or emission characteristics may have relatively low cetane numbers. A cetane number (or cetane value) is an indicator of the combustion speed of fuel and compression needed for ignition. The scale for measuring cetane numbers ranges from 0 to 100 with higher numbers indicating quicker ignition periods, thereby indicating lower temperatures and pressures required for combustion. In compression combustion engines (e.g., in diesel-type engines), ethanol is generally not used due to its relatively low cetane number (e.g., less than 5) that requires high temperatures for ignition. In other words, compression ignition engines that rely upon ethanol may encounter challenges in cold start and low load conditions in which the temperature is insufficient for reliable ignition. As examples, diesel fuel will reliably auto-ignite inside an engine cylinder at a temperature of about 500 to 600° C., while a fuel such as ethanol requires a temperature of about 850° C. in the cylinder to reliably auto-ignite.

According to examples discussed herein, a power system may include an engine that primarily operates on a low cetane fuel, such as ethanol and other alcohol-based fuels (e.g., methanol, propanol, etc.). Such power systems may include a heat exchanger that operates, under certain conditions, to increase the temperature of the intake air; and under other conditions, to reduce the temperature of the intake air, particularly when mixed with exhaust recirculation (EGR) gas. In some examples, the heating, cooling, and mixing of the charge air and the EGR gas as intake gas for the compression ignition engine may be controlled by a control system.

As discussed herein, an intake heat exchanger may be provided to use engine coolant, along with recirculated exhaust gas, to achieve the desired intake manifold temperatures required for a compression ignition engine to auto-ignite low cetane fuels. This may avoid and/or mitigate the use of excess EGR gas, thereby avoiding issues of control, stability, and undesirable emission characteristics. Such an arrangement and operation enable the use of a low cetane fuel with acceptable ignition and combustion performance in a diesel-type engine. The implementation of low cetane fuels may be facilitated by other aspects of the power system, as discussed in greater detail below.

Generally, as used herein, the term “low cetane fuel” may refer to a fuel with a cetane number (or value) less than that of diesel. For example, a low cetane fuel may have a cetane number of less than 40. One such example is ethanol with a cetane number of approximately 5.

Referring toFIG.1, in some embodiments, the disclosed power systems and methods that use low cetane fuels may be implemented with a work vehicle100embodied as a tractor. In other examples, the disclosed system and method may be implemented in other types of vehicles or machines, including stationary power systems and vehicles in the agricultural, forestry, and/or construction industries.

As shown, the work vehicle100may be considered to include a main frame or chassis102, a drive assembly104, an operator platform or cabin106, a power system108, and a controller110. As is typical, the power system108includes an internal combustion engine used for propulsion of the work vehicle100, as controlled and commanded by the controller110and implemented with the drive assembly104mounted on the chassis102based on commands from an operator in the cabin106and/or as automated within the controller110.

As described below, the power system108may include a number of systems and components to facilitate various aspects of operation. As noted, the engine of the power system108may be a compression ignition engine for combustion that may result in improvements in emissions, performance, efficiency, and capability. Moreover, the engine may utilize a low cetane fuel, as introduced above and discussed in greater detail below. Otherwise, the power system108may include an intake air arrangement to direct air into the engine and a fuel arrangement to direct fuel (or fuels) into the engine for mixing with the air for combustion, as well as optional additional systems, such as turbocharger and/or exhaust recirculation (EGR) arrangements. Although not shown or described in detail herein, the work vehicle100may include any number of additional or alternative systems, subsystems, and elements. Further details of the power system108are provided below.

As noted, the work vehicle100includes the controller110(or multiple controllers) to control one or more aspects of the operation, and in some embodiments, facilitate implementation of the power system108, including various components and control elements associated with the use of alcohol (e.g., ethanol) and ether. The controller110may be considered a vehicle controller and/or a power system controller or sub-controller. In one example, the controller110may be implemented with processing architecture such as a processor and memory. For example, the processor may implement the functions described herein based on programs, instructions, and data stored in memory.

As such, the controller110may be configured as one or more computing devices with associated processor devices and memory architectures, as a hard-wired computing circuit (or circuits), as a programmable circuit, as a hydraulic, electrical or electro-hydraulic controller, or otherwise. The controller110may be configured to execute various computational and control functionality with respect to the work vehicle100(or other machinery). In some embodiments, the controller110may be configured to receive input signals in various formats (e.g., as hydraulic signals, voltage signals, current signals, and so on), and to output command signals in various formats (e.g., as hydraulic signals, voltage signals, current signals, mechanical movements, and so on). The controller110may be in electronic, hydraulic, mechanical, or other communication with various other systems or devices of the work vehicle100(or other machinery). For example, the controller110may be in electronic or hydraulic communication with various actuators, sensors, and other devices within (or outside of) the work vehicle100, including any devices described below. In some embodiments, the controller110may be configured to receive input commands from, and to interface with, an operator via a human-vehicle operator interface that enables interaction and communication between the operator, the work vehicle100, and the power system108.

In some examples, the work vehicle100may further include various sensors that function to collect information about the work vehicle100and/or surrounding environment. Such information may be provided to the controller110for evaluation and/or consideration for operating the power system108. As examples, the sensors may include operational sensors associated with the vehicle systems and components discussed herein, including engine and transmission sensors; fuel and/or air sensors; temperature, flow, and/or pressure sensors; and battery and power sensors, some of which are discussed below. Such sensor and operator inputs may be used by the controller110to determine an operating condition (e.g., a load, demand, or performance requirement), and in response, generate appropriate commands for the various components of the power system108discussed below, particularly the control of alcohol (e.g., ethanol) and/or ether. Although not shown or described in detail herein, the work vehicle100may include any number of additional or alternative systems, subsystems, and elements.

Additional information regarding the power system108, particularly the components associated with fuel and gas flows are provided below. As introduced above and as will now be described in greater detail with reference toFIGS.2-4, the power system108uses a heat exchanger to heat and/or cool charge air and/or a mixture of charge air and EGR gas prior to introduction into the intake manifold of the engine. Such function may enhance ignition and combustion of the low cetane fuel, particularly at low temperature or low load conditions.

Reference is initially made toFIG.2, which is a schematic illustration of the power system108for providing power to the work vehicle100ofFIG.1, although the characteristics described herein may be applicable to a variety of machines. The configuration ofFIG.2is just one example of the power system108and example embodiments according to the disclosure herein may be provided in other configurations.

As introduced above, the power system108includes an engine120configured to combust a mixture of fuel from a fuel arrangement130and air from an air intake arrangement140to generate power for propulsion and various other systems, thereby generating an exhaust gas that is accommodated by an exhaust arrangement160. As also introduced above, various aspects of the power system108may be operated by the controller110(FIG.1) based on operator commands and/or operating conditions. In some examples, the controller110may be a dedicated power system controller or a vehicle controller.

As described in greater detail below, the engine120is primarily an engine that utilizes low cetane fuels, such as ethanol. Such an engine120may be similar to a diesel engine (i.e., compression ignition and combustion) in configuration and arrangement, except that other fuels are combusted instead of diesel. The engine120may have any number or configuration of piston-cylinder sets within an engine block. In the illustrated implementation, the engine120is an inline-6 (I-6) engine defining six piston-cylinder sets. In addition to those discussed below, the engine120may include any suitable feature, such as cooling systems, peripheries, drivetrain components, sensors, etc.

As noted above, the engine120is selectively provided fuel for combustion by the fuel arrangement130, particularly a low cetane fuel, such as ethanol. Generally, the fuel arrangement130may include any suitable components to facilitate operation (e.g., pumping, flow control, storage, injection, and the like) of the engine120and overall power system108.

As also noted above, the engine120is selectively provided air for combustion by the air intake arrangement140. The air intake arrangement140, in this example, includes an intake conduit142and an air intake manifold144. The air intake arrangement140directs fresh or ambient air through the air intake conduit142; and the air intake manifold directs at least a portion of that air into the air intake manifold144for introduction into the piston-cylinder sets of the engine block to be ignited with the fuel (e.g., ethanol) such that the resulting combustion products drive the mechanical output of the engine120. Additional details about the air intake arrangement140will be provided below.

The exhaust gas produced from the combustion process of the engine120may be received by the exhaust arrangement160, which includes an exhaust manifold162to receive and distribute the exhaust from the piston-cylinder sets. At least a portion of the exhaust gas is directed from the exhaust manifold162into an exhaust conduit164out of the work vehicle100, as described in greater detail below. Although not shown in detail, the exhaust gas may flow through one or more exhaust treatment components arranged proximate to the exhaust conduit164. Such exhaust treatment components may function to treat the exhaust gas passing therethrough to reduce undesirable emissions and may include components such as a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a selective catalytic reduction (SCR) system, and the like.

In this example, the power system108may include an exhaust gas recirculation (EGR) system170and a turbocharger180, each of which may have at least portions that may also be considered part of (or otherwise cooperate with) the air intake arrangement140and/or the exhaust arrangement160.

Generally, the EGR system170is configured to direct at least a first portion of exhaust gas back to the air intake arrangement140as EGR gas, i.e., such that a remaining, second portion of the exhaust gas is directed through the turbocharger180and out of the vehicle100(FIG.1) via the exhaust conduit164as vehicle exhaust, as noted above. Generally, as discussed in greater detail below, the EGR gas may be mixed with charge air (e.g., recirculated back to intake) in order to reduce the formation of NOx during combustion that may otherwise occur. Any suitable amount of exhaust gas may be recirculated (e.g., 10%-20%). The EGR system170may include one or more EGR valves172,174that operate to control the various flows of EGR gas and/or exhaust gas. Additional details regarding the EGR gas and/or EGR system170are provided below.

The turbocharger180generally functions to increase the amount of air subsequently directed into the engine120for improved engine efficiency and power output. In one example, the turbocharger180includes a turbine182that receives a portion (e.g., the second portion) of the exhaust gas, as introduced above. The turbocharger180further includes a compressor184that is driven by the turbine182. The compressor184functions to compress the ambient or charge air that enters the air intake arrangement140via the intake conduit142. Generally, the turbocharger180may be a variable-geometry turbocharger, a wastegate (WG) turbocharger, a fixed turbocharger, and/or any other suitable type of turbocharger.

Returning to the air intake arrangement140, the compressed charge air from the turbocharger compressor184may be directed into a first mixer146and mixed with at least a portion (e.g., a first portion) of the EGR gas from the EGR system170. As shown, the amount of compressed air directed into the first mixer146may be controlled by an air throttle valve148, and the amount of the first portion of EGR gas may be controlled the first EGR valve172. The relatively hot temperature of the first portion of EGR gas operates to increase the temperature of the charge air in the mixer146. The mixture of charge air and EGR gas (or “upstream first mixed gas”) is directed into an intake heat exchanger150.

In this example, the intake heat exchanger150is configured to direct engine coolant into proximity with the first mixed gas such that the fluids exchange heat with one another. In particular, the intake heat exchanger150may be a jacket water (or other coolant) heat exchanger150in which engine coolant is received by the intake heat exchanger150from the engine120, placed in proximity with the first mixed gas to facilitate the heat exchange (e.g., in adjacent passages or conduits), and then directed back to the engine120. In one example, the coolant may be water, although other fluids may be used, including glycol or a mixture of ethylene glycol and water.

Depending on the relative temperatures of the engine coolant and the first mixed gas, the intake heat exchanger150may operate as a cooler or a heater relative to the first mixed gas. In other words, when the engine coolant has a high temperature relative to the first mixed gas (e.g., on very cold days, at low loads, or at start-up), the intake heat exchanger150may operate as a heater for the first mixed gas; and when the engine coolant has a relatively low temperature relative to the first mixed gas (e.g., on warm days, at high loads, or after prolonged operation), the intake heat exchanger150may operate as a cooler for the first mixed gas. Additional information regarding the heating and/or cooling of the first mixed gas by the intake heat exchanger150will be provided below.

Briefly, the power system108may additionally include a second heat exchanger (or radiator)152to facilitate cooling of the engine120via circulation of the coolant over a cooling mechanism, such as air-cooled fins. The coolant of the second heat exchanger152may be on the same cooling circuit as the coolant of the first heat exchanger150, or the first and second heat exchangers150,152may be on separate cooling circuits.

Returning to the air intake arrangement140, downstream of the intake heat exchanger150, the first mixed gas (or “downstream first mixed gas”) is directed into a second mixer154, which selectively additionally receives a further portion (or second portion) of EGR gas. The amount of second portion of EGR gas directed to the second mixer154may be controlled by the second EGR valve174, which in turn may be commanded by the controller110(FIG.1). Generally, the second portion of EGR gas has a greater temperature than the downstream first mixed gas. As such, the resulting second mixed gas (or intake gas) may have a greater temperature than the downstream first mixed gas and a lower temperature than the second portion of EGR gas.

The second mixed gas (or intake gas) is directed to the intake manifold144, which as noted above, distributes the intake gas to the cylinders of the engine120for mixture, ignition, and combustion with fuel from the fuel arrangement130.

As noted above, the intake heat exchanger150may operate to warm the mixture of charge air and EGR gas during starting conditions. In other words, during these initial operating conditions, the coolant from the engine120may be at a higher temperature than the mixture of charge air and EGR gas. However, during typical operating conditions, the intake heat exchanger150may operate to cool the mixture of charge air and EGR gas. As one example collection of temperatures within the power system108, the ambient temperature of into the air intake arrangement140may be approximately 15° C., and upon the compression that increases the temperature, the charge air temperature upstream of the first mixer146may be approximately 170° C. The exhaust gas directed from the exhaust manifold162to the EGR system170may be approximately 650° C. Upon mixing the charge air and the EGR gas, the temperature of the resulting mixture upstream of the first heat exchanger150may be approximately 300°, and upon cooling in the intake heat exchanger150, the mixed charge air may have a temperature of approximately 100° C. Upon being further mixed with additional EGR gas at the second mixer154, the resulting intake gas directed to the intake manifold144is approximately 120° C., which is an advantageous temperature for ignition and combustion of the low cetane fuel of the fuel arrangement130. Generally, such temperatures, particularly for auto-ignition, may also depend on the compression ratio achieved in the piston-cylinder sets. For example, a compression ratio of around 15 may require an intake temperature of approximately 130° C., while a higher compression ratio of around 20 may require an intake temperature of approximately 115° C.

As such, the arrangement of this power system108provided improvements with respect to both high and low load operating conditions. For example, at low loads a mixed gas heat exchanger may heat the incoming charge air, which reduces the amount of hot EGR needed to reach the intake manifold temperature; and at high loads, additional EGR gas may be mixed with the charge air and flow with the charge air through the mixed gas cooler, thereby enabling higher rates of EGR at these higher load points (and lower NOx emission) while maintaining the desired intake manifold temperature.

Generally, operation of this power system108(as well as other power systems discussed herein) enables increased flexibility in the ranges of EGR that may be provided to the engine120while maintaining the desired intake air temperature. At idle and very low loads, when the engine exhaust temperature is lowest, a maximum rate of hot EGR may be needed to reach the intake air temperature requirement, which may reach up to 50% hot EGR. As the power increases and exhaust temperature rises, the rate of hot EGR will decrease. At some point (e.g., around 25% load), the EGR valve allowing EGR into the mixed gas cooler may be opened, thereby allowing EGR into the mixed gas cooler to increase the overall EGR percentage into the engine, which will lower the NOx emissions of the engine120. As power increases further, less hot EGR is needed and more EGR into the mixed gas cooler may be added to achieve an optimal balance point of fuel economy and NOx emissions. At high and peak loads, only the smallest amount of hot EGR is needed and the EGR into the mixed gas cooler will be limited by the engines peak cylinder pressure limit or boost pressure limit.

As introduced above, the controller110(FIG.1) may control operation of the engine120, including the fuel arrangement130and air intake arrangement140, as well as various other cooperating systems and components. In particular, the controller110may selectively command the nature of the air being directed into the air intake manifold to provide reliable ignition and combustion within the engine120under all appropriate conditions. Generally, the controller110(FIG.1) may be in communication with the various valves148,172,174, engine120, sensors, and other associated components to collect information about operation of the power system108and to implemented or command modification and/or maintenance of such operation.

The power system108depicted inFIG.2is merely one example of a power system that may utilize a heat exchanger for heating and/or cooling charge air and/or a mixture of charge air and EGR gas prior to introduction into the intake manifold for ignition and combustion. Additional examples of power system are depicted inFIGS.3and4.

Reference is now made toFIG.3, which is a schematic illustration of the power system208for providing power to a work vehicle, such as the work vehicle100ofFIG.1. Unless otherwise noted, the characteristics of the power system108discussed with reference toFIG.2are applicable to the power system208ofFIG.3.

As above, the power system208includes an engine220configured to combust a mixture of fuel from a fuel arrangement230and air from an air intake arrangement240to generate power for propulsion and various other systems, thereby generating an exhaust gas that is accommodated by an exhaust arrangement260. As also introduced above, various aspects of the power system208may be operated by the controller (e.g., controller110ofFIG.1) based on operator commands and/or operating conditions. Further, as above, the engine220is primarily an engine that utilizes low cetane fuels, such as ethanol provided fuel for combustion by the fuel arrangement230.

The air intake arrangement240, in this example, may include an intake conduit242and an air intake manifold244; and the exhaust arrangement260may include an exhaust manifold262and an exhaust conduit264. The power system208may include an exhaust gas recirculation (EGR) system270and dual turbochargers280, each of which may have at least portions that may also be considered part of (or otherwise cooperate with) the air intake arrangement240and/or the exhaust arrangement260.

Generally, the EGR system270is configured to direct at least a first portion of exhaust gas back to the air intake arrangement240as EGR gas while at least a second portion of the exhaust gas is directed through aspects of the dual turbochargers280and out of the vehicle via the exhaust conduit264as vehicle exhaust. The EGR system270may include one or more EGR valves272,274that operate to control the various flows of EGR gas and/or exhaust gas. Additional details regarding the EGR gas and/or EGR system270are provided below.

The dual turbochargers280, in this example, are formed by two sets of compressors284,286and turbines282,288. In particular, exhaust gas from the exhaust manifold262is directed through and drives turbine288and is subsequently directed through and drives turbine282before being directed out of the power system208via exhaust conduit264. Turbine282is coupled to and drives compressor284, and turbine288is coupled to and drives compressor286. As a result, the incoming intake air is compressed twice by the dual turbochargers280. In one example, the compressor286and turbine288may be considered a high-pressure turbocharger, and the compressor284and turbine282may be considered a low-pressure turbocharger. In some examples, a cooler256may be provided to cool the air between compressor284and compressor286.

Returning to the air intake arrangement240, the compressed charge air from the turbochargers280may be directed into a first mixer246and mixed with at least a portion (e.g., a first portion) of the EGR gas from the EGR system270. As shown, the amount of compressed air directed into the first mixer246may be controlled by an air throttle valve248, and the amount of the first portion of EGR gas may be controlled the first EGR valve272. The relatively hot temperature of the first portion of EGR gas operates to increase the temperature of the charge air in the mixer246. The mixture of charge air and EGR gas (or “upstream first mixed gas”) is directed into an intake heat exchanger250.

In this example, the intake heat exchanger250is configured to direct engine coolant into proximity with the first mixed gas such that the fluids exchange heat with one another. In particular, the intake heat exchanger250may be a jacket water (or other coolant) heat exchanger250in which engine coolant is received by the intake heat exchanger250from the engine220, placed in proximity with the first mixed gas to facilitate the heat exchange, and then directed back to the engine220. Depending on the relative temperatures of the engine coolant and the first mixed gas, the intake heat exchanger250may operate as a cooler or a heater relative to the first mixed gas. Briefly, the power system208may additionally include a second heat exchanger (or radiator)252to facilitate cooling of the engine220via circulation of the coolant over a cooling mechanism, such as air-cooled fins.

Returning to the air intake arrangement240, downstream of the intake heat exchanger250, the first mixed gas (or “downstream first mixed gas”) is directed into a second mixer254, which selectively additionally receives a further portion (or second portion) of EGR gas. The amount of second portion of EGR gas directed to the second mixer254may be controlled by the second EGR valve274, which in turn may be commanded by a controller (e.g., controller110ofFIG.1). Generally, the second portion of EGR gas has a greater temperature than the downstream first mixed gas. As such, the resulting second mixed gas (or intake gas) may have a greater temperature than the downstream first mixed gas and a lower temperature than the second portion of EGR gas. The second mixed gas (or intake gas) is directed to the intake manifold244, which as noted above, distributes the intake gas to the cylinders of the engine220for mixture, ignition, and combustion with fuel from the fuel arrangement230.

As noted above, the intake heat exchanger250may operate to warm the mixture of charge air and EGR gas during starting conditions. In other words, during these initial operating conditions, the coolant from the engine220may be at a higher temperature than the mixture of charge air and EGR gas. However, during typical operating conditions, the intake heat exchanger250may operate to cool the mixture of charge air and EGR gas. As one example collection of temperatures within the power system108, the ambient temperature of into the air intake arrangement240may be approximately 15° C., and upon compression by compressors284,286, the charge air temperature upstream of the first mixer246may be approximately 250° C. The exhaust gas directed from the exhaust manifold262to the EGR system370may be approximately 650° C. Upon mixing the charge air and the EGR gas, the temperature of the resulting mixture upstream of the first heat exchanger250may be approximately 300° C., and upon cooling in the intake heat exchanger250, the mixed charge air may have a temperature of approximately 100° C. Upon being further mixed with additional EGR gas at the second mixer254, the resulting intake gas directed to the intake manifold244is approximately 120° C., which is an advantageous temperature for ignition and combustion of the low cetane fuel of the fuel arrangement230. Generally, such temperatures, particularly for auto-ignition, may also depend on the compression ratio achieved in the piston-cylinder sets.

Reference is now made toFIG.4, which is a schematic illustration of a further power system308for providing power to a work vehicle, such as the work vehicle100ofFIG.1. Unless otherwise noted, the characteristics of the power system108discussed with reference toFIG.2are applicable to the power system308ofFIG.4.

As above, the power system308includes an engine320configured to combust a mixture of fuel from a fuel arrangement330and air from an air intake arrangement340to generate power for propulsion and various other systems, thereby generating an exhaust gas that is accommodated by an exhaust arrangement360. As also introduced above, various aspects of the power system308may be operated by the controller (e.g., controller110ofFIG.1) based on operator commands and/or operating conditions. Further, as above, the engine320is primarily an engine that utilizes low cetane fuels, such as ethanol provided for combustion by the fuel arrangement330.

The air intake arrangement340, in this example, may include an intake conduit342and an air intake manifold344; and the exhaust arrangement360may include an exhaust manifold362and an exhaust conduit364. The power system308may include an exhaust gas recirculation (EGR) system370and a turbocharger380, each of which may have at least portions that may also be considered part of (or otherwise cooperate with) the air intake arrangement340and/or the exhaust arrangement360.

Generally, the EGR system370is configured to direct at least a first portion of exhaust gas back to the air intake arrangement340as EGR gas while at least a second portion of the exhaust gas is directed through aspects of the dual turbochargers280and out of the vehicle via the exhaust conduit364as vehicle exhaust. The EGR system370may include one or more EGR valves374,358that operate to control the various flows of EGR gas and/or exhaust gas. In this example, the EGR system370may have two “paths,” e.g., a cooled path in which a first portion of EGR flow is directed through an EGR cooler356and a bypass path in which a second portion of EGR flow is directed around (and not through) the EGR cooler356. Valves358,374may be commanded (e.g., by controller110ofFIG.1) to control the amount of flow through and around the EGR cooler356. The EGR cooler356may be any suitable device configured to lower the temperature of the recirculated gas. Generally, the EGR cooler356includes one or more recirculated gas passages and one or more coolant passages, arranged such that heat may be transferred from the recirculated gas to a cooperating fluid (e.g., air or liquid). Additional details regarding the EGR gas and/or EGR system370are provided below.

The turbocharger380generally functions to increase the amount of air subsequently directed into the engine320for improved engine efficiency and power input. In one example, the turbocharger380includes a turbine382that receives a portion (e.g., the second portion) of the exhaust gas, as introduced above. The turbocharger380further includes a compressor384that is driven by the turbine382. The compressor384functions to compress the ambient or charge air that enters the air intake arrangement340via the intake conduit342. In other examples, the turbocharger380may be supplemented with dual turbochargers (e.g., similar to those discussed above with reference toFIG.3).

Returning to the air intake arrangement340, the compressed charge air from the turbocharger380may be directed into an intake heat exchanger350that is configured to direct engine coolant into proximity with the charge air such that the fluids exchange heat with one another. In particular, the intake heat exchanger350may be a jacket water (or other coolant) heat exchanger350in which engine coolant is received by the intake heat exchanger350from the engine320, placed in proximity with the charge air to facilitate the heat exchange, and then directed back to the engine320. Depending on the relative temperatures of the engine coolant and the charge air, the intake heat exchanger350may operate as a cooler or a heater relative to the charge air. As shown, the amount of compressed charge air directed into through the first heat exchanger350may be controlled by an air throttle valve348. In one example, the intake heat exchanger350and the EGR cooler356may have a common coolant circuit (e.g., with engine coolant), while in other examples, the intake heat exchanger350and the EGR cooler356may have separate coolant circuits. Briefly, the power system308may additionally include a second heat exchanger (or radiator)352to facilitate cooling of the engine320via circulation of the coolant over a cooling mechanism, such as air-cooled fins.

Downstream of the air intake heat exchanger350and the EGR cooler356, the cooled EGR gas and the intake charge air are mixed within a first mixer346The relatively hot temperature of the first portion of EGR gas operates to increase the temperature of the charge air in the mixer346. The mixture of charge air and EGR gas (or “first mixed gas”) is directed into a second mixer354. In effect, in this example, the EGR and charge intake air may be separately cooled prior to mixing in the first mixer346.

In addition to the first mixed gas, the second mixer354selectively additionally receives a further portion (or second portion) of EGR gas. The amount of second portion of EGR gas directed to the second mixer354may be controlled by the second EGR valve374, which in turn may be commanded by a controller (e.g., controller110ofFIG.1). Generally, the second portion of EGR gas has a greater temperature than the downstream first mixed gas. As such, the resulting second mixed gas (or intake gas) may have a greater temperature than the downstream first mixed gas and a lower temperature than the second portion of EGR gas. The second mixed gas (or intake gas) is directed to the intake manifold344, which as noted above, distributes the intake gas to the cylinders of the engine320for mixture, ignition, and combustion with fuel from the fuel arrangement330.

As noted above, the intake heat exchanger350may operate to warm the charge air during starting conditions. In other words, during these initial operating conditions, the coolant from the engine320may be at a higher temperature than the charge air. However, during typical operating conditions, the intake heat exchanger350may operate as to cool the charge air. As compared to other examples, the heat exchanger350in this example may use lower cost materials, such as aluminum, since the heat exchanger350does not process any portion of the EGR gas. Additionally, the heat exchanger350may be smaller than other examples, mounted on the engine120, and may obviate the use of a vehicle air to air charge cooler. In any event, the heat exchanger350, as above, provide an advantageous dual purpose of both heating the charge air at low loads and cooling the charge air at high loads.

As one example collection of temperatures within the power system308, the ambient temperature of into the air intake arrangement340may be approximately 15° C., and upon compression, the charge air temperature upstream of the first heat exchanger may be approximately 170° C. and cooled by the first heat exchanger350to approximately 100° C. The exhaust gas directed from the exhaust manifold362to the EGR system370may be approximately 650° C. Upon mixing the charge air and the EGR gas, the temperature of the resulting mixture upstream of the first heat exchanger350may be approximately 110° C. Upon being further mixed with additional EGR gas at the second mixer354, the resulting intake gas directed to the intake manifold344is approximately 120° C., which is an advantageous temperature for ignition and combustion of the low cetane fuel of the fuel arrangement330. Generally, such temperatures, particularly for auto-ignition, may also depend on the compression ratio achieved in the piston-cylinder sets.

Accordingly, the power systems discussed above provide the ability to use ethanol and other low cetane fuels in a diesel-type, compression ignition engine over a range of conditions, including cold starts and low load conditions. Overall, the power systems described herein result in a platform architecture that may provide improved fuel consumption, higher performance, and reduced criteria pollutants over a relatively wide temperature operating window. As noted, the heat exchanger may operate as a cooler at high loads and a heater at low loads. In particular, at relatively light loads, this may enable the use of less EGR gas than may otherwise be needed for this purpose at the second mixer, thereby enabling more efficient use of EGR gas through the engine and the resulting lower NOx emissions and advantageous ignition and combustion characteristics. This may also enable increased exhaust flow for the turbochargers.

As will be appreciated by one skilled in the art, certain aspects of the disclosed subject matter may be embodied as a method, system (e.g., a work vehicle control or power system included in a work vehicle), or computer program product. Accordingly, certain embodiments may be implemented entirely as hardware, entirely as software (including firmware, resident software, micro-code, etc.) or as a combination of software and hardware (and other) aspects. Furthermore, certain embodiments may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium.