WO2009058338A1

WO2009058338A1 - System and method for electrically regenerating a particulate filter assembly of a generator set

Info

Publication number: WO2009058338A1
Application number: PCT/US2008/012330
Authority: WO
Inventors: Kent M. Mckee
Original assignee: Caterpillar Inc.
Priority date: 2007-11-02
Filing date: 2008-10-31
Publication date: 2009-05-07
Also published as: AU2008319348A1; DE112008002964T5; US20090113874A1

Abstract

A method of operating a generator set (10) includes steps of operating an internal combustion engine (12) of the generator set (10) and driving an electrical generator (14) of the generator set (10) with the internal combustion engine (12). The method also includes a step of determining if an excess amount of electrical power is sufficient to regenerate a particulate filter assembly (24) positioned downstream of the internal combustion engine (12). The excess electrical power includes a difference between electrical power produced by the electrical generator (14) and electrical power requested by a load requestor (18). The particulate filter assembly (24) is regenerated if it is determined that the excess electrical power is sufficient for regeneration by energizing at least one electrical heating element (48) using the excess electrical energy. The regeneration is delayed if a predetermined criteria is satisfied.

Description

SYSTEM AND METHOD FOR ELECTRICALLY REGENERATING A PARTICULATE FILTER ASSEMBLY OF A GENERATOR SET

Technical Field

The present disclosure relates generally to regenerating a particulate filter assembly of a generator set, and more particularly to electrically regenerating the particulate filter assembly using excess electrical energy produced by a generator of the generator set.

Background

With the rapid growth of demand for electricity combined with a need for uninterrupted power, the utilization of generator sets has become much more widespread. Generator sets are available in a wide range of power ratings and are commonly used in a variety of environments, including hospitals and other industries that rely upon a steady source of power, and environments where commercially generated electricity is not available. Generator sets typically consist of an internal combustion engine coupled with an electrical generator for generating electrical power and, as such, produce various particulates and emissions. Governmental regulations that initially applied to exhaust emissions of on-highway and off-highway machines are now extending to stationary applications, such as generator sets. Exhaust aftertreatment systems used in on-highway and off-highway machines typically include a particulate filter. Particulate filters, such as diesel particulate filters, generally consist of a ceramic honeycomb structure that is surrounded by a non-permeable skin layer and include numerous channels that are blocked at alternate ends. This structure forces exhaust gas to flow through the porous walls between the channels, leaving particulate matter deposited on the walls. Periodically, or once a substantial amount of particulate matter is collected within the particulate filter, it must be regenerated to prevent excess blockage. The process of oxidizing or burning off the accumulated particulate matter from the filter is referred to generally as regeneration.

One method for regenerating a diesel particulate filter of a generator set is disclosed in U.S. Published Application No. 2004/0226287. Specifically, a regeneration sequence is invoked immediately after an engine of the generator set is stopped, thus taking advantage of an already preheated particulate filter. An air pump is used to convect heat from a commercially available electrical regeneration system to the particulate filter in order to provide the supplemental heat required to regenerate the particulate filter. Although this method may prove effective, it does not contemplate the use of excess electrical power produced by a generator of the generator set to heat the particulate filter to a regeneration level. In addition, no strategy is discussed to measure the excess electrical power provided and either delay or initiate regeneration. Furthermore, this reference does not address the problem of a clogged filter in need of regeneration while the generator set is operating.

The present disclosure is directed to one or more of the problems set forth above.

Summary of the Disclosure

In one aspect, a method of operating a generator set includes steps of operating an internal combustion engine of the generator set and driving an electrical generator of the generator set with the internal combustion engine. The method also includes a step of determining if an excess amount of electrical power is sufficient to regenerate a particulate filter assembly positioned downstream of the internal combustion engine. The excess electrical power includes a difference between electrical power produced by the electrical generator and electrical power requested by a load requestor. The particulate filter assembly is regenerated, if it is determined that the excess electrical power is sufficient for regeneration, by energizing at least one electrical heating element using the excess electrical energy. The regeneration is delayed if a predetermined criteria is satisfied, such as the excess electrical power is insufficient for regeneration.

In another aspect, a generator set includes an internal combustion engine and a particulate filter assembly positioned downstream of the internal combustion engine. The particulate filter assembly includes at least one electrical heating element. An electrical generator is driven by the internal combustion engine and produces electrical power exceeding an amount requested by a load requestor. An electronic controller is configured to determine if the excess amount of electrical power is sufficient to regenerate the particulate filter assembly. The electronic controller is further configured to initiate regeneration of the particulate filter assembly, if it is determined that the excess electrical power is sufficient for regeneration, by causing the excess electrical power to energize the at least one electrical heating element. The electronic controller is further configured to delay regeneration if a predetermined criteria is satisfied, such as the excess electrical power is insufficient for regeneration.

In yet another aspect, a computer usable medium having computer readable program code thereon for operating a generator set includes computer readable program code for determining a regeneration timing for a particulate filter assembly positioned downstream of an internal combustion engine. The computer usable medium also includes computer readable program code for determining if an excess amount of electrical power is sufficient to regenerate the particulate filter assembly. The excess electrical power includes a difference between electrical power produced by an electrical generator and electrical power requested by a load requestor. The computer usable medium also includes computer readable program code for causing the excess electrical power to energize at least one electrical heating element of the particulate filter assembly to regenerate the particulate filter assembly, if it is determined that the excess electrical power is sufficient for regeneration. The computer usable medium also includes computer readable program code for delaying regeneration if a predetermined criteria is satisfied, such as the excess electrical power is insufficient for regeneration.

Brief Description of the Drawings

Figure 1 is a block diagram of a generator set according to the present disclosure; and

Figure 2 is a flow chart of one embodiment of a method for operating the generator set of Figure 1 according to the present disclosure.

Detailed Description

An exemplary embodiment of a generator set 10 is shown generally in Figure 1. The generator set 10 includes an engine, such as an internal combustion engine 12, and an electrical generator 14. The internal combustion engine 12 may utilize diesel, gas, or one of various other fuels. The engine 12 includes a crankshaft 16 that is rotated by internal components of the engine 12 to produce mechanical power at a certain engine speed, such as, for example, 1500 or 1800 revolutions per minute (RPMs).

The electrical generator 14 is mechanically coupled to the engine crankshaft 16 and, therefore, driven by the crankshaft 16 to produce electrical power, such as, for example, AC power, at a frequency that is determined by the engine speed. For example, electrical power may be produced at a standard frequency of 50 or 60 Hz. The electrical generator 14 provides electrical power to a load requestor 18, via an electrical transmission line 20, at a voltage, frequency, and power rating selected to suit the connected load. It should be appreciated that generator sets, such as generator set 10, are available in a wide range of such ratings. In addition to the internal combustion engine 12 and electrical generator 14, the generator set 10 may also include an exhaust conduit 22 for transporting an exhaust stream from the internal combustion engine 12 and into the ambient air. A particulate filter assembly 24, such as a diesel particulate filter assembly, may be disposed along the exhaust outlet 22 as part of an exhaust aftertreatment system for the internal combustion engine 12. Particulate filters, such as particulate filter assembly 24, may consist of one or more filter sections for removing particulate matter from the exhaust stream by physical filtration. Other features, including, but not limited to, a starter motor, a battery, and an electrical ground may also be provided with the generator set 10. It should also be appreciated that the generator set 10 may also include an automatic starting and stopping circuit for use with backup power source applications. For example, the generator set 10 may detect whether electrical power has been lost and, if it has, the internal combustion engine 12 is started and electrical power is provided to the load requestor 18 until the main source of electrical power has been restored.

An electronic controller 26 (hereinafter referred to as the "main controller") is also provided for controlling and monitoring operation of the generator set 10 and various components of the generator set 10, including the internal combustion engine 12 and electrical generator 14. The main controller 26 may be of standard design and includes a processor 28, such as, for example, a central processing unit (CPU), a memory 30, and an input/output circuit that facilitates communication internal and external to the main controller 26. The processor 28 controls operation of the main controller 26 by executing operating instructions, such as, for example, computer readable program code stored in memory, wherein operations may be initiated internally or externally to the main controller 26. A control scheme may be utilized that monitors outputs of systems or devices, such as, for example, sensors, actuators, or control units, via the input/output circuit to control inputs to various other systems or devices. The memory 30 may comprise temporary storage areas, such as, for example, cache, virtual memory, or random access memory (RAM), or permanent storage areas, such as, for example, read-only memory (ROM), removable drives, network/internet storage, hard drives, flash memory, memory sticks, or any other known volatile or non-volatile data storage devices located internally or externally to the main controller 26. One skilled in the art will appreciate that any computer-based system utilizing similar components is suitable for use with the present disclosure.

An engine controller 32 may also be provided and may be in communication with the main controller 26 via a communication line 34, which may include a wireless connection. The engine controller 32 may be similar to the main controller 26 in both function and design, and may control various aspects of the operation of internal combustion engine 12. For example, the engine controller 32 may control the quantity of fuel injected into each cylinder during each engine cycle, and the ignition timing. In addition, the engine controller 32 may control or include an engine speed regulator. Further, the internal combustion engine 12 may include various sensors, such as, for example, engine speed sensors, load sensors, temperature sensors, and pressure sensors, in communication with the engine controller 32. A generator controller 36 may control and monitor operation of the electrical generator 14 and may be in communication with the main controller 26 via a wired or wireless communication line 38. The generator controller 36 may also be similar in function and design to the main controller 26 and may monitor and process input from various sensors of the electrical generator 14. Although the generator set 10 is shown having a specific set of controllers, it should be appreciated that other embodiments may include only the main controller 26, only the generator controller 36 and engine controller 32, or the main 26 and one of the generator controller 36 and the engine controller 32. Various additional controllers may also be provided. A pressure sensor 40 may be disposed along the exhaust conduit 22, such as, for example, upstream of the particulate filter assembly 24, for detecting a pressure along the exhaust conduit 22. In addition, a temperature sensor 42 may be positioned at or near the particulate filter assembly 24 to sense a temperature of the one or more filter sections of the particulate filter assembly 24. Each of the pressure sensor 40 and the temperature sensor 42, and any additional sensors deemed appropriate, may be in communication with the main controller 26 via communication lines 44 and 46. Monitoring one or both of these sensors 40 and 42 may provide an indication of a load of the particulate filter assembly 24 and, therefore, whether or not the particulate filter assembly 24 needs regeneration. It should be appreciated that a "load" of the particulate filter assembly 24 may represent an accumulation of particulate matter within the particulate filter assembly 24.

The particulate filter assembly 24 may be provided with at least one electrical heating element 48 for facilitating regeneration. The electrical heating element 48 is based on the principle of resistance heating, with a current flowing through an electrically conductive material to heat the trapped particulate matter within the particulate filter assembly 24 to a temperature at which it combusts or vaporizes. The electrical heating element 48 is connected to a voltage source, namely the electrical generator 14, via an electrical transmission line 50. Electrical power generated by the electrical generator 14 may be supplied to the electrical heating element 48 periodically, or as a function of certain parameters, such as, for example, exhaust gas backpressure sensed by pressure sensor 40 or particulate filter temperature determined by temperature sensor 42. The supply of electrical power from the electrical generator 14 to the electrical heating element 48 may be interrupted after a period of time sufficient to initiate the regeneration process.

Specifically, the main controller 26 may be configured to determine when the particulate filter assembly 24 needs regeneration and, in response, direct the electrical generator 14 to energize, or supply electrical power to, the electrical heating element 48 of the particulate filter assembly 24 to facilitate regeneration. After a period of time sufficient to begin regeneration, the electronic controller 26 may instruct the electrical generator 14 to cease supplying electrical power to the electrical heating element 48 and, thereby, de- energize the electrical heating element 48.

It should be appreciated by those skilled in the art that the particulate filter assembly 24, including the at least one electrical heating element 48, may include any one of a variety of configurations. According to one embodiment, the particulate filter assembly 24 may include a plurality of filter sections. A plurality of heating elements, each similar to electrical heating element 48, may also be provided. Each heating element may be positioned adjacent one of the plurality of filter sections and, when energized, may cause regeneration of the adjacent filter section. It should be appreciated that a desirable control scheme for the embodiment may include the regeneration of one filter section at a time, such as in a sequential manner, and may require less electrical power at one time than required for a regeneration of the entire particulate filter assembly 24.

Industrial Applicability Referring to Figure 1, a typical generator set 10 includes an internal combustion engine 12 for driving an electrical generator 14. The electrical generator 14 provides electrical power to a load requestor 18, via an electrical transmission line 20, at a voltage, frequency, and power rating selected to suit the connected load. In addition, the generator set 10 includes an exhaust conduit 22 in communication with an exhaust stream of the internal combustion engine 12. A particulate filter assembly 24, including at least one electrical heating element 48, is disposed along the exhaust conduit 22 to reduce particulate matter emissions from the internal combustion engine 12. Particulate filters, such as particulate filter assembly 24, generally consist of a ceramic honeycomb structure that is surrounded by a non-permeable skin layer and include numerous channels that are blocked at alternate ends. This structure forces exhaust gas to flow through the porous walls between the channels, leaving particulate matter deposited on the walls. Periodically, or once a substantial amount of particulate matter is collected within the particulate filter assembly 24, it should be regenerated to prevent blockage.

Utilizing the generator set 10 and method for electrically regenerating a particulate filter assembly, such as particulate filter assembly 24, according to the present disclosure may help to improve the performance and extend the life of the particulate filter assembly 24 while utilizing excess electrical power produced by the electrical generator 14. Turning to Figure 2, there is shown a flow chart 60 representing an exemplary method of regenerating the particulate filter assembly 24 of the generator set 10 of Figure 1. The method may be implemented in whole, or in part, by the main controller 26, in combination with the engine controller 32 and the generator controller 36, of the generator set 10. Each of the controllers 26, 32, and 36 may include a computer usable medium having computer readable code thereon for implementing the method, which may run continuously, at a predetermined frequency, or may be initiated by an operator.

The method begins at a START, Box 62. From Box 62, the method proceeds to Box 64, which includes the step of monitoring a load or accumulation amount of the particulate filter assembly 24. Specifically, the main controller 26 may monitor one or both of a pressure sensor 40 and a temperature sensor 42 to determine the load of the particulate filter assembly 24.

Alternatively, the electronic controller 26 may be configured to estimate the load of the particulate filter assembly 24 based on the internal combustion engine 12 operating at a constant speed. It should be appreciated that there exist many alternatives for determining a load or accumulation of the particulate filter assembly 24.

From Box 64, the method proceeds to Box 66. At Box 66, the main controller 26 determines if regeneration of the particulate filter assembly 24 is necessary. It may be desirable to regenerate the particulate filter assembly 24 periodically or, alternatively, when a first predetermined threshold is reached, such as when a particularly high load or accumulation is detected at Box 64. It should be appreciated that numerous methods for determining when regeneration is necessary are contemplated, and many different accumulation thresholds may be selected.

If regeneration is deemed necessary, the method proceeds to Box 68. If, however, the main controller 26 determines that regeneration is not necessary, the method may return to Box 64, where the load of the particulate filter assembly 24 is continually monitored or monitored at a predetermined frequency. At Box 68, the main controller 26, in communication with the generator controller 36, calculates an excess amount of electrical power produced by the electrical generator 14. The excess amount of electrical power includes a difference between electrical power produced by the electrical generator 14 and electrical power requested by the load requestor 18. It should be appreciated that generator sets, such as generator set 10, are typically sized to accommodate the highest anticipated starting, peak, and running loads and, therefore, usually produce, or are capable of producing, excess electrical power, which may or may not be used.

Once the amount of excess electrical power is calculated at Box 68, the method proceeds to Box 70. At Box 70, the main controller 26 determines if the amount of excess electrical power is sufficient for regeneration. Specifically, the main controller 26 compares the amount of excess electrical power calculated at Box 68 to an amount of electrical power necessary for regeneration. According to one embodiment, the amount of electrical power necessary for regeneration may include the requisite power for regenerating the entire particulate filter assembly 24. Alternatively, the electrical power necessary for regeneration may only include the power necessary for regenerating one of a plurality of filter sections of the particulate filter assembly 24, such as by energizing one of a plurality of heating elements.

If the excess electrical power is sufficient for regeneration, as determined at Box 70, the method proceeds to Box 72. At Box 72, the main controller 26 instructs the electrical generator 14, via generator controller 36, to provide the excess electrical power to the electrical heating element 48. The excess electrical power energizes the electrical heating element 48, thereby heating the trapped particulate matter to a temperature at which it combusts or vaporizes. It should be appreciated that, if multiple heating elements are used, the main controller 26 may be configured to communicate with each of the heating elements and manage regeneration of the particulate filter assembly 24 according to a predetermined strategy.

If the main controller 26 determines that the amount of excess electrical power is insufficient for regeneration, the method proceeds to Box 74. At Box 74, the main controller 26 may determine if an override mode is in effect. The override mode may be optional, and may offer the ability to regenerate the particulate filter assembly 24 even if a sufficient amount of excess electrical power is not available. For example, it may be desirable to regenerate the particulate filter assembly 24 if regeneration has not occurred for an extended period of time. Alternatively, regeneration may be desirable if the load of the particulate filter assembly 24 has reached a second predetermined threshold, such as when extreme blockage is detected, or if the performance of the particulate filter assembly 24 is compromised.

If the override mode is in effect, the method proceeds to Box 76. Box 76 includes a step of limiting the electrical power available to the load requestor 18. It should be appreciated that the main controller 26, and/or the generator controller 36, may only limit the electrical power to the load requestor 18 for a time period necessary to initiate regeneration of the particulate filter assembly 24, at Box 72.

If the override mode is not in effect, the method proceeds to Box 78, which includes the step of delaying regeneration. The main controller 26 may delay regeneration when a predetermined criteria is satisfied, such as when a determination at Box 70 is made that the excess electrical power is insufficient for regeneration. It should be appreciated that one or more additional criteria may also be required. The regeneration may be delayed for a predetermined period of time or, alternatively, indefinitely. Ultimately, the method returns to Box 68 to recalculate the amount of excess electrical power produced by the electrical generator 14. When a sufficient amount of excess electrical power is available, the method will eventually proceed to Box 72, which includes regeneration of the particulate filter assembly 24, as described above. After the particulate filter assembly 24 is regenerated, the method proceeds to an END, at Box 80.

It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.

Claims

1. A method of operating a generator set ( 10), comprising: operating an internal combustion engine (12) of the generator set (10); driving an electrical generator (14) of the generator set (10) with the internal combustion engine (12); determining if an excess amount of electrical power is sufficient to regenerate a particulate filter assembly (24) positioned downstream of the internal combustion engine (12), wherein the excess electrical power includes a difference between electrical power produced by the electrical generator (14) and electrical power requested by a load requestor (18); regenerating the particulate filter assembly (24) if it is determined that the excess electrical power is sufficient for regeneration by energizing at least one electrical heating element (48) using the excess electrical power; and delaying regeneration if a predetermined criteria is satisfied.

2. The method of claim 1, further including determining when to regenerate the particulate filter assembly (24) at least in part by monitoring a load of the particulate filter assembly (24).

3. The method of claim 2, wherein the monitoring step includes sensing a pressure across the particulate filter assembly (24).

4. The method of claim 2, wherein the monitoring step includes sensing a temperature of the particulate filter assembly (24).

5. The method of claim 1, wherein the regenerating step includes limiting the amount of electrical power available to the load requestor (18) if a sum of the electrical power requested by the load requestor (18) and electrical power required by the regenerating step exceeds the electrical power produced by the electrical generator (14).

6. A generator set (10), comprising: an internal combustion engine (12); a particulate filter assembly (24) positioned downstream of the internal combustion engine (12), wherein the particulate filter assembly (24) includes at least one electrical heating element (48); an electrical generator (14) driven by the internal combustion engine (12), wherein the electrical generator (14) produces electrical power exceeding an amount requested by a load requestor (18); an electronic controller (26) configured to determine if the excess amount of electrical power is sufficient to regenerate the particulate filter assembly (24) and initiate regeneration of the particulate filter assembly (24) if it is determined that the excess electrical power is sufficient for regeneration by causing the excess electrical power to energize the at least one electrical heating element (48); and wherein the electronic controller (26) is further configured to delay regeneration if a predetermined criteria is satisfied.

7. The generator set (10) of claim 6, wherein the electronic controller (26) is further configured to determine when to regenerate the particulate filter assembly (24) at least in part by monitoring a load of the particulate filter assembly (24).

8. The generator set (10) of claim 7, further including a pressure sensor (40) disposed upstream of the particulate filter assembly (24), wherein the electronic controller (26) is further configured to determine the particulate filter load based on a pressure value of the pressure sensor (40).

9. The generator set (10) of claim 7, further including a temperature sensor (42) positioned to detect a temperature of the particulate filter assembly (24), wherein the electronic controller (26) is further configured to determine the particulate filter load based on a temperature value of the temperature sensor (42).

10. The generator set (10) of claim 6, wherein the electronic controller (26) is further configured to limit the amount of electrical power available to the load requestor (18) during the regeneration if a sum of the electrical power requested by the load requestor (18) and electrical power required by the regeneration exceeds the electrical power produced by the electrical generator (14).