WO2008039272A1

WO2008039272A1 - Hybrid engine exhaust gas temperature control system

Info

Publication number: WO2008039272A1
Application number: PCT/US2007/017654
Authority: WO
Inventors: Charles Rose; Maarten Verkiel
Original assignee: Caterpillar Inc.
Priority date: 2006-09-29
Filing date: 2007-08-08
Publication date: 2008-04-03
Also published as: US20080078166A1

Abstract

A power system is provided having a power source (16) operationally coupled to a generator (18). The power system also includes an exhaust passage (28) having at least one after-treatment device (32, 34) configured to release exhaust from the power source into the atmosphere. In addition, a controller (24) is configured to determine at least one exhaust passage condition indicative of an exhaust temperature and operate the generator in response to the determination.

Description

HYBRID ENGINE EXHAUST GAS TEMPERATURE CONTROL SYSTEM

Technical Field The present disclosure is directed to a hybrid engine and, more particularly, to a hybrid engine having the capability to control the exhaust gas temperature.

Background

Hybrid engines typically include an electric motor and an internal combustion engine. Internal combustion engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art may exhaust a complex mixture of air pollutants. The air pollutants are composed of solid particulate matter and gaseous compounds including nitrogen oxides. Due to increased attention on the environment, exhaust emission standards have become more stringent, and the amount of solid particulate matter and gaseous compounds emitted to the atmosphere from an engine is regulated depending on the type of engine, size of engine, and/or class of engine.

One method that has been implemented by engine manufacturers to comply with the regulation of these engine emissions includes the use of after- treatment devices such as nitrogen oxide absorbers, sulfur oxide absorbers, and hyrdocarbon catalysts. These devices operate by mixing a chemical catalyst with exhaust gas produced by the engine to transform much of the existing pollutants into harmless elements such as water and nitrogen. However, these devices require a predetermined temperature range for efficient operation. In some situations, the temperature of the exhaust flowing through the after-treatment devices may be too low for efficient operation. Without raising the temperature in these situations, the exhaust exiting an engine may not meet the emission regulations. In other situations, the overly high exhaust gas temperature may become hot enough to damage the after-treatment devices.

Several methods have been implemented to remedy this issue. One method includes using fuel burners or electric heaters to artificially raise the temperature of the after-treatment devices to within the predetermined efficiency range. Still, other methods include the use of an air or liquid cooler to cool the temperature of the exhaust gas in order to avoid damaging the after-treatment devices. While these methods may be effective, they can be inefficient, costly, and unreliable.

Yet another method that has been implemented is disclosed in U.S. patent no. 6,657,315, issued to Peters et al. (hereinafter the '315 patent). The '315 patent discloses a hybrid engine system including an internal combustion engine and an electric motor. When the engine temperature is below a predetermined threshold, the electric motor provides a negative torque to the internal combustion engine. By providing a negative torque on the engine, the engine load increases which in turn, increases the temperature of the exhaust gas passing through the after-treatment devices. When the engine temperature is above a predetermined threshold, an electric motor assists the internal combustion engine by providing a positive torque on the engine. By assisting the engine, the engine load decreases, which in turn decreases the exhaust gas temperature. The '315 method eliminates the inefficiencies and cost of using additional components to control the temperature of the exhaust gas.

Although the method disclosed in the '315 patent may eliminate the inefficiencies and costs associated with using additional components to control the exhaust gas temperature, the disclosed determination of the temperature of the exhaust passing through the after-treatment devices may not be accurate. In particular, the method indirectly determines the exhaust gas temperature by sensing the temperature of the engine. Due to inefficiencies in the hybrid engine system, the temperature of the engine may not reflect the temperature of the exhaust gas passing through the after-treatment devices. Because of this, the '315 method may allow the exhaust gas temperature to be outside of the preferred temperature range. This may lead to a reduction in the efficiency of the after-treatment devices. It may also lead to heat-related damage to the after-treatment devices.

The disclosed power system is directed to overcoming one or more of the problems set forth above.

Summary of the Invention In one aspect, the present disclosure is directed toward a power system. The power system includes a power source operationally coupled to a generator. The power system also includes an exhaust passage having at least one after-treatment device and configured to release exhaust from the power source into the atmosphere. The power system further includes a controller configured to determine at least one exhaust passage condition indicative of an exhaust temperature and operate the generator in response to the determination.

Consistent with a further aspect of the disclosure, a method is also provided for adjusting an exhaust gas temperature. The method includes sensing at least one power source condition indicative of an exhaust gas temperature. The method also includes either applying an additional load on a power source or assisting the power source in response to the sensed condition indicative of an exhaust gas temperature.

Brief Description of the Drawings

Fig. 1 is a diagrammatic illustration of an exemplary disclosed machine;

Fig. 2 is a diagrammatic illustration of an exemplary disclosed power train for used with the machine of Fig. 1; and Fig. 3 is a flow chart depicting an exemplary method of operating the power train of Fig. 2.

Detailed Description

Fig. 1 illustrates an exemplary machine 10 having multiple systems and components that cooperate to accomplish a task. The tasks performed by machine 10 may be associated with a particular industry such as mining, construction, farming, transportation, power generation, or any other industry known in the art. For example, machine 10 may embody a mobile or stationary machine such as the on-highway vocational vehicle depicted in Fig. 1, a bus, an off-highway haul truck, a generator, or any other type of mobile or stationary machine known in the art. Machine 10 may include one or more traction devices 12 operatively connected to and driven by a power train 14.

Traction devices 12 may embody wheels located on each side of machine 10 (only one side shown). Alternatively, traction devices 12 may include tracks, belts or other known traction devices. It is contemplated that any combination of the wheels on machine 10 may be driven and/or steered.

Power train 14 may be an integral package configured to generate and transmit power to traction devices 12, hydraulic pumps (not shown) for an excavator (not shown), or any other device requiring power from a power source. In particular, power train 14 may include a power source 16, which may be operably associated with a generator 18 and may drive generator 18 such that mechanical energy from power source 16 is converted into electric energy. Power train 14 may also include a motor 20 connected to receive power output from generator 18 and transmit the power output in a useful manner to traction devices 12. As shown in Fig. 2, power train 14 may further include a power storage device 22, which may store electrical energy produced by generator 18 or supply stored electrical energy to motor 20. Additionally, the components of power train 14 may be in communication with and controlled by a controller 24. It should be understood that, in an alternate embodiment, power train 14 may include a hydraulic pump (not shown), hydraulic motors (not shown), and an accumulator (not shown). It should also be understood that, in an alternate embodiment, power train 14 may include a flywheel (not shown) for storing energy. Additionally, power source 16 may include an internal combustion engine having multiple subsystems that cooperate to produce mechanical or electrical power output. For the purposes of this disclosure, power source 16 is depicted and described as a four-stroke diesel engine. One skilled in the art will recognize, however, that power source 16 may be any other type of internal combustion engine such as, for example, a gasoline or a gaseous fuel-powered engine. One of the subsystems included within power source 16 may be an exhaust system 26. Other subsystems included within power source 16 may be, for example, a fuel system, an air induction system, a lubrication system, a cooling system, or any other appropriate system (not shown). Exhaust system 26 may remove or reduce the amount of pollutants in the exhaust produced by power source 16 and release the treated exhaust into the. atmosphere. Exhaust system 26 may include an exhaust passage 28 which may be in fluid communication with an exhaust manifold 30 of power source 16. Exhaust system 26 may also include after-treatment devices fluidly connected along exhaust passage 28 such as a particulate filter 32 and/or a catalytic device 34.

Particulate filter 32 may be any general type of exhaust filter known in the art. Particulate filter 32 may include any type of filter media (not shown) known in the art, such as, for example, a ceramic foam, ceramic, sintered metal, metal foam, or silicon carbide, or silicon carbide foam type filter. The filter media (not shown) may assist in removing particulate matter like soot, soluble organic fraction (SOF), and other pollutants produced by power source 16. The filter media (not shown) may be situated horizontally, vertically, radially, or in any other configuration allowing for proper filtration. Additionally, the filter media (not shown) may be of a honeycomb, mesh, mat, or any other configuration that provides an appropriate surface area available for filtering of particulate matter. Furthermore, the filter media (not shown) may contain pores, cavities or spaces of a size that allows exhaust gas to flow through while substantially restricting the passage of particulate matter. In an alternate embodiment, the filter media (not shown) may contain heating elements capable of heating the filter media (not shown) and the exhaust during a regeneration process.

Catalytic device 34 may be disposed downstream of particulate filter 32, and may include components that function to treat exhaust as it flows from particulate filter 32. Specifically, exhaust emissions now substantially free of particulate matter may flow from particulate filter 32 through a catalyst medium (not shown) that is retained within a housing of catalytic device 34. It is contemplated that one or more catalyst mediums may alternatively be arranged to receive the gaseous emissions in series or parallel relation. The number of catalyst mediums within catalytic device 34 may be variable and depend on the back pressure, filtration, and size requirements of a particular application. It is contemplated that catalytic device 34 may alternatively be located upstream of particulate filter 32. The catalyst medium may include, for example, a foam material having a catalyst configured to react with the exhaust flow entering catalytic device 34. The foam material may be formed from sintered metallic particles such as, for example, alumina, titania, or any other high-temperature alloy. The foam material may also be formed from ceramic particles such as, for example, silicon carbide, cordierite, mullite, or any other ceramic particles known in the art. The foam material may be formed into a filter medium through a casting process, an injection molding process, or any other process that produces a porous material with a desired porosity. A catalyst may be incorporated throughout the foam material and may be configured to reduce an amount of nitrogen oxide in the flow of exhaust, to decrease an oxidation temperature of the particulate matter trapped by the particulate filtration medium, to reduce an amount of carbon monoxide in the flow of exhaust, and/or to reduce an amount of unburned hydrocarbons in the flow of exhaust. The catalyst may include, for example, an oxidation catalyst, an SCR catalyst, an HC-DeNOx catalyst, or any other appropriate type of catalyst. It is contemplated that the catalyst medium may alternatively include a wire mesh material having a catalyst coating. It is further contemplated that catalytic device 34 may be omitted, if desired, and a catalyst coating applied to particulate filter 32. Catalytic devices operate efficiently only within a certain temperature range. In addition, critical functions involving after-treatment devices such as the regeneration of particulate filter 32, require that the exhaust gas be above a threshold temperature. In order to monitor the temperature of the exhaust gas flowing through the after-treatment devices, a sensor 36 may be associated with exhaust passage 28 to sense a temperature of the exhaust gas. Sensor 36 may be any type of temperature sensor mounted within exhaust passage 28. For example, sensor 36 may embody a surface-type temperature sensor that measures a wall temperature of exhaust passage 28. Alternately, sensor 36 may be a gas-type temperature sensor that directly measures the temperature of the exhaust gas within exhaust passage 28. Sensor 36 may generate an exhaust gas temperature signal and send this signal to controller 24 via a communication line (not shown) as is known in the art. This temperature signal may be sent continuously, on a periodic basis, or only when prompted to do so by controller 24. In an alternate embodiment, it is contemplated that controller 24 may utilize other sensory input as a substitute for the temperature signal, if desired. Such input may be associated with various exhaust passage parameters, such as, for example, exhaust gas flow rate, exhaust gas pressure, or any other paxameter known in the art. Controller 24 may receive and analyze this input to derive the exhaust gas temperature.

Generator 18 may be any known AC or DC generator such as, permanent magnet, induction, switched-reluctance, or a hybrid combination of the above, and may also be sealed, brushless, and/or liquid cooled, for example, to provide a more durable design. Generator 18 may be operatively coupled to power source 16 via a crankshaft, or in any other manner known in the art, and may be configured to convert at least a portion of a power output of power source 16 to electrical energy. In an exemplary embodiment, generator 18 may be configured to both drive power source 16 and be driven by power source 16. In addition, generator 18 may be used to provide electric energy to power one or more electric motors 20. It may be contemplated that generator 18 can be configured to produce a direct current (DC) output or an alternating current (AC) output. It is also contemplated that AC or DC outputs may be converted with the use of a power converter (not shown) to produce a variety of current and/or voltage outputs for use by various components of machine 10.

Electric motor 20 may be operatively coupled to generator 18 and configured to provide a mechanical force for performing a task associated with machine 10. Electric motor 20 may be any known AC or DC motor such as, permanent magnet, induction, switched-reluctance, or a hybrid combination of the above,_and may also be sealed, brushless, and/or liquid cooled. Although referred to in the singular, electric motor 20 may be more than one electric motor. By virtue of receiving electric energy from generator 18 and/or power storage device 22, electric motor 20 may create a torque for driving traction devices 12. Although electric motor 20 is illustrated as a drive for one or more traction devices 12, it is contemplated that electric motor 20 may be used in any application of machine 10 that may require mechanical energy to operate.

Power storage device 22 may be any kind of known power storage device such as, for example, a battery and/or an ultra-capacitor, or flywheel. In an exemplary embodiment, power storage device 22 may store excess electric energy generated by generator 18 and/or provide any additional electric energy that may be needed when starting machine 10 and/or during operation of machine 10. For example, when machine 10 is operating in a low load condition, for example, it is neither traveling across the ground nor operating any of its implements (not shown), power source 16 may continue to run at a given engine speed or engine speed range. In such relatively low load conditions, it may be possible to operate machine 10 more efficiently, for example, and generator 18 can continue to convert mechanical energy into electric energy, which may be stored in power storage device 22. Alternatively, for a situation in which machine 10 is traveling across the ground at a given speed, and the operator commands a work implement to perform a task such as, for example, the operator commands a bucket containing a load of dirt to be raised while machine 10 remains moving, power storage device 22 may provide additional energy beyond the electric energy being generated by generator 18, and may prevent the engine from lugging down or stalling, and/or may prevent machine 10 from slowing down.

In addition to powering motor 20, both generator 18 and power storage device 22 may be used to power electric power consuming devices 38. Electric-power consuming devices 38 may include, for example, one or more of an air conditioning unit, a heating unit, a resistive grid, lights, appliances, personal electronics, pumps, motors, and other electronic engine components and accessories known in the art.

Controller 24 may embody a single microprocessor or multiple microprocessors that include a means for controlling the operation of power train 14. Numerous commercially available microprocessors can be configured to perform the functions of controller 24. It should be appreciated that controller 24 could readily embody a general machine microprocessor capable of controlling numerous machine functions or an engine microprocessor. Controller 24 may include a memory, a secondary storage device, a processor, and any other components for running an application. Various other circuits may be associated with controller 24 such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry.

Industrial Applicability

The disclosed exhaust treatment system may provide a reliable and inexpensive way to control the exhaust temperature in a hybrid engine system, hi particular, the disclosed exhaust treatment system may eliminate the need for inefficient, expensive, and unreliable peripheral devices by adjusting the engine load to produce the desired exhaust temperature necessary for the proper function of the after-treatment devices. The operation of the exhaust treatment system will now be explained.

As is illustrated by the method disclosed in Fig. 3, at step 100, sensor 36 may sense the temperature of the exhaust gas in exhaust passage 28. Sensor 36 may then transmit signals based on the exhaust gas temperature to controller 24. At step 102, controller 24 may receive the signals from sensor 36 and may determine whether the exhaust gas temperature is below a first predetermined threshold, e.g., 200 degrees Celsius. Controller 24 may make this determination by performing algorithms, referencing a look-up map, or follow other techniques well-known in the art.

Step 104 may be performed if controller 24 determines that the exhaust gas temperature is below the first predetermined threshold. During step 104, controller 24 may cause generator 18 to convert the kinetic energy produced by the spinning of the crankshaft (not referenced) of engine 16 into electric energy. When converting kinetic energy to electric energy, generator 18 may develop a resistive torque. The resistive torque works against the torque produced by engine 16 and ultimately adds to the existing load placed on engine 16. Applying the additional load on engine 16 requires engine 16 to increase fueling. The increased fueling may result in an increased exhaust temperature. It should be understood that if generator 18 is already applying a load on engine 16, then the load may be increased to raise the exhaust temperature.

By applying the load on engine 16, generator 18 may produce excess electrical energy. In step 106, generator 18 may distribute the excess electrical energy in one of a number of ways. For example, generator 18 may direct the excess electrical energy to battery 22. Charging battery 22 may be the most efficient use of the excess electrical energy because the excess energy produced by engine 16 can be stored for later use. However, if battery 22 is already fully charged, the excess electrical energy may be used to operate electrically actuated accessories 38. Such accessories may include an air conditioner, an electrically driven fan or pump, or any other electrically actuated device known in the art. If it is not preferred to operate electrically actuated devices, and battery 22 is fully charged, the excess electrical energy may be dissipated through a resistive grid (not shown). Once generator 18 has begun applying the load to engine 16, step

108 may be performed. At step 108, sensor 36 may sense the temperature of the exhaust gas in exhaust passage 28. Sensor 36 may then transmit signals based on the exhaust gas temperature to controller 24. At step 110, controller 24 may receive the signals from sensor 36 and may determine whether the exhaust gas temperature is still below the first predetermined threshold. Controller 24 may make this determination by performing algorithms, referencing a look-up map, or follow other techniques well-known in the art.

If controller 24 determines that the exhaust temperature is still below the first predetermined threshold, then generator 18 may continue applying the load. However, if controller 24 determines that the exhaust temperature is above the first threshold temperature, then step 112 may be performed. At step 112, generator 18 terminates the additional load. It should be understood that if generator 18 was applying a load to engine 16 before the disclosed method was performed, then the load may not be terminated. Instead, the load may be reduced to the level applied before the commencement of the disclosed method. Step 114 may be performed after step 112 is accomplished or if controller 24 determines that the exhaust temperature is above the first predetermined threshold. At step 114, controller 24 may receive the signals from sensor 36 and may determine whether the exhaust gas temperature is above a second predetermined threshold, e.g., 600 degrees Celsius. Controller 24 may make this determination by performing algorithms, referencing a look-up map, or follow other techniques well-known in the art. If controller 24 determines that the exhaust temperature is below the second predetermined threshold, then sensor 36 may continue to sense the exhaust gas temperature. However, if controller 24 determines that the exhaust temperature is above the second predetermined threshold, then step 116 may be performed. At step 116, controller 24 may cause battery 22 to assist engine 16 in powering vehicle 10. By using the electrical energy stored in battery 22 to help power vehicle 10, the load applied to engine 16 is reduced. Reducing the load on engine 16 allows engine 16 to reduce fueling. The reduced fueling may result in a decreased exhaust temperature. It should be understood that if battery 22 is already assisting engine 16 power vehicle 10, then the electrical energy supplied by battery 22 may be increased to lower the exhaust temperature.

Once battery 22 has begun supplying electrical energy, step 118 may be performed. At step 118, sensor 36 may sense the temperature of the exhaust gas in exhaust passage 28. Sensor 36 may then transmit signals based on the exhaust gas temperature to controller 24. At step 120, controller 24 may receive the signals from sensor 36 and may determine whether the exhaust gas temperature is still above the second predetermined threshold. Controller 24 may make this determination by performing algorithms, referencing a look-up map, or follow other techniques well-known in the art. If controller 24 determines that the exhaust temperature is still above the second predetermined threshold, then battery 22 may continue supplying the electrical energy stored in battery 22. However, if controller 24 determines that the exhaust temperature is below the second threshold temperature, then step 122 may be performed. At step 122, battery 22 may discontinue the supply of electrical energy. It should be understood that if battery 22 was supplying electrical energy before the disclosed method was performed, then the amount of electrical energy may be reduced to the level being supplied before the commencement of the disclosed method. Using the generator to apply an additional load on the engine or using the battery to assist the engine when the exhaust temperature is outside of the optimal range of the after-treatment devices provides an efficient, cost effective, and reliable method for complying with exhaust emissions regulations. Specifically, a significant portion of the energy produced when increasing the exhaust temperature can be harnessed rather than wasted by storing it in the battery for later use when the engine exhaust needs to be cooled. In addition, the configuration of the system does not require additional components that might add to the complexity and cost of the system. Furthermore, because the controller reacts to the actual temperature of the exhaust when it flows through the after-treatment devices, the system provides a reliable and accurate means to control the temperature of the exhaust.

It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed system without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. A power system, comprising: a power source (16) operationally coupled to a generator (18); an exhaust passage (28) including at least one after-treatment device (32, 34) and configured to release exhaust from the power source into the atmosphere; and a controller (24) configured to determine at least one exhaust passage condition indicative of an exhaust temperature and operate the generator in response to the determination.

2. The power system of claim 1, further including a sensor (36) located in the exhaust passage and configured to measure a temperature of the exhaust, wherein the controller is in communication with the sensor to receive a temperature signal.

3. The power system of claim 2, wherein the controller is configured to operate the generator in a manner that applies an additional load on the power source when the signal indicates the temperature of the exhaust gas being below a first threshold temperature.

4. The power system of claim 2, further including a power storage device (22), wherein the controller is configured to operate the power storage device in a manner that assists the power source when the signal indicates the temperature of the exhaust gas being above a second threshold temperature.

5. A method for adjusting an exhaust gas temperature, comprising: sensing at least one power source condition indicative of an exhaust gas temperature; and either applying an additional load on a power source (16) or assisting the power source in response to the sensed condition indicative of the exhaust gas temperature.

6. The method of claim 5, wherein applying the additional load on the power source further includes applying the additional load on the power source when the temperature of the exhaust gas is below a first threshold temperature.

7. The method of claim 6, further including storing electrical power produced by the application of the additional load on the power source.

8. The method of claim 6, further including operating electrical devices with excess electricity produced by the application of the additional load on the power source.

9. The method of claim 5, wherein assisting the power source further includes assisting the power source when the temperature of the exhaust gas is above a second threshold temperature.

10. The method of any of claims 5-9, further including determining the temperature of an exhaust gas and determining whether the temperature is within a predetermined temperature range.