Patent Application
20120192547
The present disclosure generally relates to exhaust gas treatment systems. More particularly, a dual circuit secondary air system cooperates with a diesel particulate filter regeneration device to improve emissions control.
This section provides background information related to the present disclosure which is not necessarily prior art.
Exhaust aftertreatment systems may include a diesel particulate filter for treating the exhaust of a diesel engine. In many applications, it may be beneficial to periodically regenerate or oxidize soot trapped within the diesel particulate filter. A regeneration device such as a burner may be positioned upstream of the diesel particulate filter. The burner is typically provided with a fuel such as a hydrocarbon, a supply of oxygen and one or more igniters. Combustion of the fuel within the burner increases the energy of the exhaust entering the diesel particulate filter. Oxidation of the soot trapped within the filter occurs during the regeneration process.
Some vehicles are equipped with compressors associated with engine superchargers or turbochargers. In some instances, the output from the compressor provides a secondary air supply to a nozzle useful for atomizing the fuel within the regeneration device. Because the compressor output is typically directly related to engine speed, the flow of compressed air to the nozzle varies greatly during engine operation. As such, an exhaust aftertreatment system properly designed for operation at relatively low to moderate engine speeds may not optimally function at an upper range of engine speeds.
For example, at high engine speeds, the output flow rate from the compressor is high. The resistance to air flow through the nozzle of the burner may be significant. A resistance to flow at the outlet of the compressor may undesirably load the compressor and increase the operating temperature of the compressor. Control systems may be required to assure that the compressor temperature does not exceed a predetermined maximum temperature. A maximum output pressure may be set. By limiting the compressor output, the flow rate of secondary air through the burner nozzle may be insufficient to heat the high volume of exhaust flowing through the burner. An undesirably low temperature at the diesel particulate filter inlet may result. Therefore, a need in the art may exist to provide a modified secondary air system for use with an exhaust gas aftertreatment system.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
An exhaust treatment system for an engine includes a regeneration device being in receipt of exhaust from the engine and positioned upstream of a diesel particulate filter. A compressor provides a source of compressed air. An air/fuel nozzle is coupled to the regeneration device, in receipt of a fuel supply as well as the compressed air. The fuel and compressed air are forced through an orifice of the nozzle to atomize the fuel. A bypass line provides compressed air from the compressor to the regeneration device without passing through the orifice of the nozzle. A valve is operable to allow compressed air to flow through the bypass line when a predetermined condition exists.
A method of treating exhaust from an engine includes compressing air using energy from the engine. A regeneration device is positioned upstream from a diesel particulate filter. Exhaust is passed through the regeneration device and the diesel particulate filter. The method includes providing a fuel and compressed air from the compressor to an air/fuel nozzle coupled to the regeneration device and providing a parallel path for compressed air from the compressor to the regeneration device bypassing the air/fuel nozzle to reduce the load on the compressor.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.
Example embodiments will now be described more fully with reference to the accompanying drawings.
An air/fuel nozzle 34 is mounted to regeneration device 28 and plumbed in communication with a fuel delivery system 36 and a secondary air system 38. Fuel delivery system 36 includes a fuel tank 40, a fuel filter 42, a fuel pump 44 and a fuel block 46 interconnected by a fuel line 48. Operation of the components of fuel system 36 selectively provides hydrocarbons to air/fuel nozzle 34.
Secondary air system 38 includes a secondary air filter 50 and a MAF sensor 52. A compressor 54 is in receipt of air that has passed through secondary air filter 50 and MAF sensor 52. Compressor 54 may be a portion of one of a supercharger or a turbocharger. A supercharger 55 is shown including an input 56 driven by engine 12 via a flexible member 58.
Secondary air system 38 also includes a recirculation loop 60 having a bypass air throttle 62 in receipt of compressed air from an outlet 64 of compressor 54. Air passing through bypass air throttle 62 is cooled by flowing through an intercooler 66. An outlet of intercooler 66 is in communication with an inlet 68 of compressor 54.
Secondary air system 38 also includes dual supply circuit 69 having a primary passageway 70 providing compressed air from compressor outlet 64 to air/fuel nozzle 34. A secondary passageway 72 is provided to allow communication between outlet 64 of compressor 54 and a primary combustion zone 76 of regeneration device 28. Air passing through secondary passageway 72 bypasses air/fuel nozzle 34. A check valve 78 and a control valve 80 are positioned within secondary passageway 72 to control the flow of fluid passing therethrough.
Regeneration device 28 includes a housing 90 circumferentially surrounding a combustion tube 92. Combustion tube 92 includes a first portion 94 defining primary combustion zone 76, a second portion 96 defining a secondary combustion zone 98 and a necked portion 100 having a reduced diameter interconnecting first portion 94 and second portion 96. An aperture 102 extends through housing 90 and first portion 94 to provide access to primary combustion zone 76. As shown in
A modified air/fuel nozzle 34′ is shown in
Air/fuel nozzle 34′ also includes a shroud 140 surrounding housing 124. Second air inlet 122 provides air to an annular cavity 142 formed between housing 124 and shroud 140. The air provided via secondary passageway 72 passes through a swirler 144 and exits air/fuel nozzle 34′ at an aperture 146. Aperture 146 is substantially larger than orifice 130 thereby producing a greatly reduced delta pressure across air/fuel nozzle 34′ than the secondary air passing through orifice 130. Aperture 146 is aligned with orifices 130 and 136 to allow fuel and both sources of secondary air to exit air/fuel nozzle 34′ and enter primary combustion zone 76. The manner in which air from secondary passageway 72 travels through cavity 142 and across housing 124 provides cooling and shielding from the heat generated within primary combustion zone 76.
In operation, engine 12 is operable across a wide range of speeds and loads. At low to moderate engine speed and load operating conditions, bypass air throttle 62 may be controlled to recirculate a portion of the secondary air output from compressor 54 with the remainder of the output from the compressor being provided to and passing through primary passageway 70. At this time, control valve 80 is closed and secondary air does not pass through secondary passage 72. During the low to moderate load operation, the load on compressor 54 based on the restriction to secondary air flow through air/fuel nozzle 34 is moderate. As such, compressor 54 is not prone to overheating during these operation modes.
A controller 160 actively controls bypass air throttle 62. Controller 160 may also receive and manipulate data provided by a first temperature sensor 162 located upstream of regeneration device 28, a second temperature sensor 164 located downstream of regeneration device 28 and upstream of diesel particulate filter 30 and a third temperature sensor 166 positioned downstream of diesel particulate filter 30. A pressure differential sensor 168 may output a signal indicative of the pressure differential across diesel particulate filter 30. Controller 160 may utilize the information provided by the sensors described above as well as MAF sensor 52. Other information may be available from the vehicle controller such as signals indicative of engine speed, ambient temperature, vehicle speed, engine coolant temperature, oxygen content and any number of other vehicle parameters.
Based on the information provided to controller 160, regeneration device 28 may be selectively operated to regenerate diesel particulate filter 30 when the appropriate set of conditions are present. In one example, regeneration occurs when sensor 168 indicates a pressure differential greater than a predetermined value exists across diesel particulate filter 30. At this time, fuel block 46 is controlled to allow fuel to pass through fuel line 48 to air/fuel nozzle 34. Bypass air throttle 62 is controlled to provide sufficient supply of secondary air to primary passageway 70. Coil 106 and coil 112 may be energized to initiate combustion by generating a spark at primary igniter 104 and secondary igniter 110.
During engine operation at relatively high speed and/or load, the output from compressor 54 may be too large to pass the entire flow rate through primary passageway 70 without greatly increasing the load on compressor 54. As the pressure within secondary passageway increases to a predetermined magnitude, control valve 80 opens to allow secondary air to pass through secondary passageway 72. As previously mentioned, control valve 80 may be a passive pressure relief valve having a predetermined crack pressure or alternatively may be solenoid actuated via control module 160 as an on/off valve. Valve 80 may be actively controlled to vary the pressure by selectively controlling the valve to a number of positions between a fully open position and a fully closed position.
It should be appreciated that valve 80 may allow air to pass through secondary passageway 72 regardless of the energization state of primary igniter 104 and secondary igniter 110.
Use of secondary passageway 72 and control valve 80 substantially expands the total flow operating range. As shown in traces 174, 176, droplet size ranges from 10 to 14 SMD throughout a flow rate of approximately 13 to 40 g/s. Furthermore, the pressure drop across air/fuel nozzle 34 very gradually increases from 10 kPa to approximately 20 kPa as total flow ranges from 13 g/s to 40 g/s.
With the operation range of regeneration device 28 being expanded to a total flow ranging from approximately 7 g/s through 40 g/s, light off may be achieved within primary combustion zone 76 throughout substantially the entire operating range of engine 12 from idle speed to wide open throttle. Viewed another way, a common air/fuel nozzle 34 may be implemented within a number of different systems having different engines, superchargers or compressors. The cracking pressure or control of valve 80 may be varied to assure proper flow through both primary passageway 70 and secondary passageway 72.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
This patent application claims the benefit of U.S. Provisional Patent Application No. 61/437,896, filed Jan. 31, 2011, the entire teachings and disclosure of which are incorporated herein by reference thereto.
| Number | Date | Country | |
|---|---|---|---|
| 61437896 | Jan 2011 | US |
