The present application relates to methods using a non-engine based test system to produce diesel exhaust for testing and/or regenerating diesel aftertreatment components.
Diesel powered engines are used to conduct a variety of tests on diesel engine aftertreatment devices, including aging and regeneration testing of diesel particulate filters. It is desirable to conduct such tests with a high level of precision at the lowest cost possible. Historically, the use of diesel engines to perform the above procedures has presented many disadvantages including inconsistent operability, intensive maintenance, and expensive operating costs. Methods are needed which overcome the foregoing deficiencies.
The present application provides a method for testing a component. The method comprises: providing a non-engine based test system comprising a combustor in fluid communication with the component; supplying diesel fuel and air to the combustor at a controlled air to fuel ratio (AFR) and under feed conditions effective to produce a feedstream flowpath effective to prevent substantial damage to the combustor; combusting at least a portion of the diesel fuel in the feed stream flowpath under combustion conditions effective to produce diesel exhaust comprising one or more particulates; and, exposing the component to the diesel exhaust under test conditions effective to produce a contaminated component comprising an amount of diesel contaminant particulates.
Numerous test methods have been used in the past to simulate aging and regeneration of diesel aftertreatment components. Diesel exhaust comprises particulates, which are believed to be unburned carbon particulates or “soot.” The particulates generally are removed from the exhaust using a diesel particulate filter.
In the past, a diesel particulate filter was aged by exposing the diesel particulate filter to diesel exhaust created by a diesel powered engine, thereby loading the filter with particulates from the diesel exhaust. The diesel powered engine generally was on a bench stand in the laboratory or on a motor vehicle. Examples of diesel powered engines used in such tests include but are not necessarily limited to the Cummins ISM (10.8 liter), the Navistar T444E (7.3 liter V-8), and the Detroit Diesel Series 60 PSA DW-12 (2.2L). The diesel powered engine had to be run at various high speed and load conditions cyclically for several hours in order to simulate aging of the diesel particulate filter. Higher temperatures could be generated using a diesel powered engine only by post injection or in-exhaust injection of fuel, rendering generation of temperatures up to 650° C. relatively expensive and fuel inefficient.
The present application substitutes a non-engine based exhaust component rapid aging system (NEBECRAS) for a diesel powered engine in such tests to produce diesel exhaust gas. The use of a NEBECRAS in place of a diesel powered engine lowers operating costs, reduces test variability, and increases control of the exhaust gas composition, pressure, mass flow rate, and temperature. The NEBECRAS also can be used to regenerate the diesel particulate filter.
Non-Engine Based Exhaust Component Rapid Aging System
U.S. patent application Publication No. 20030079520 describes a preferred NEBECRAS (the FOCAS® rig) for use in the present method(s). Briefly, the FOCAS® rig comprises: (1) an air supply system to provide air for combustion to the burner, (2) a fuel system to provide fuel to the burner, (3) a burner system to combust the air and fuel mixture and to provide the proper exhaust gas constituents, (4) a heat exchanger to control the exhaust gas temperature, (5) (optionally) an oil injection system, and (6) a computerized control system. The foregoing components are illustrated in
The FOCAS® rig was developed to evaluate the long term effects of individual variables on the long term performance of exhaust aftertreatment devices (i.e., a catalyst). The FOCAS® rig produces exhaust gas with a composition and temperature corresponding to that produced by the internal combustion engine of a motor vehicle.
The burner system in the FOCAS® rig is effective to substantially stoichiometrically combust at least a portion of fuel in the feedstream flowpath without substantial damage to the combustor. In a preferred embodiment, the combustor comprises a nozzle comprising a swirl plate which is effective even at a stoichiometric air to fuel ratio (AFR) of producing a feedstream flowpath comprising an air shroud effective to prevent flame from attaching to a nozzle supplying fuel and air to the combustor during combustion of fuel. The feedstream flowpath also preferably prevents flame from remaining in constant contact with an inner wall of the combustor during combustion of fuel.
Although the FOCAS® rig is a preferred NEBECRAS, it will be apparent to persons of ordinary skill in the art that any functional and effective non-engine based test system could be adapted for use in accordance with the principles described herein.
The NEBECRAS may be used to perform substantially any test which requires diesel exhaust and to test substantially any diesel engine exhaust component, preferably diesel engine exhaust aftertreatment comoponents. The NEBECRAS also may be used to regenerate substantially any particulate contaminated component. Preferred exhaust components for treatment and/or regeneration by the NEBECRAS include but are not necessarily limited to catalyzed and non-catalyzed diesel particulate filters (DPFs), lean NOx catalysts (LNTs), and diesel oxidation catalysts (DOCs).
The burner system in the FOCAS® rig may be used to generate stoichiometric, rich, and lean hot gas conditions without substantial damage to the combustor. In a preferred embodiment, the combustor of the FOCAS® rig comprises a feed member comprising a swirl plate which is effective even at a stoichiometric air to fuel ratio (AFR) of producing a feedstream flowpath comprising an air shroud effective to prevent flame from attaching to a feed member during combustion of fuel. The feedstream flowpath also preferably prevents flame from remaining in constant contact with an inner wall of the combustor during combustion of fuel.
The FOCAS® rig may be programmed to produce diesel exhaust or alternative exhaust compositions with increased or decreased amounts of a particular exhaust component or components, for example, to simulate diesel exhaust produced in cold climates, at high altitudes, during engine acceleration conditions (i.e., increased NOx production), during engine deceleration conditions (i.e., decreased NOx production), and combinations thereof. For example, an exhaust gas can be programmed to achieve fuel sulfur levels including but not necessarily limited to 15-ppm, 30-ppm, 50-ppm, 100-ppm, and 300-ppm, etc., depending on the desired particulate matter requirements of the exhaust gas.
A catalytic converter may be positioned with respect to the diesel particulate filter to assist in simulating a preferred diesel exhaust. For instance, the FOCAS® rig may include a NOx reducing catalyst upstream (or downstream) of the diesel particulate filter simulating a NOx reduced exhaust gas product contacting the filter. In the alternative, the FOCAS® rig may simply be programmed to simulate a NOx reduced exhaust gas without using a reducing catalyst.
The FOCAS® rig may be deactivated, the system may be cooled to ambient conditions in a matter of minutes, and then immediately after cooling (if desired), the system can be used to perform additional testing. The FOCAS® rig offers improved repeatability and reduced cool down time. The FOCAS® rig also offers relatively easy maintenance compared to diesel engines, which require periodic maintenance (oil changes, tune-ups) and time consuming repairs. The FOCAS® rig is relatively simple (with less moving parts and friction areas) and can operate with improved fuel economy when operated lean. These advantages make it highly desirable as a research and development tool.
Diesel Exhaust
Diesel fuel generally boils in a range of from about 140° C. to about 400° C., typically from about 150° C. to about 370° C. As explained above, diesel fuel generally produces a diesel exhaust comprising particulates. The accuracy of a given simulation using diesel exhaust depends, at least in part, on the exhaust gas composition.
The main components of diesel exhaust include but are not necessarily limited to carbon monoxide (CO), carbon dioxide (CO2), oxides of nitrogen (NOx), oxides of sulfur; hydrocarbons (HC); unburned carbon particulate matter; oxygen (O2); and/or nitrogen (N2). Other compounds also may be included in the exhaust gas depending on the desired test conditions. Preferred compounds comprise components selected from the group consisting of phosphorous, zinc, sulfur and combinations thereof. The quantity and composition of diesel exhaust during testing using diesel powered engines varies depending on a number of factors, including but not necessarily limited to: wear and tear on engine moving parts; quality of lubrication oil; uncontrolled lubrication oil consumption; quality of the diesel fuel; type of engine; engine tuning; fuel pump setting; the workload demand on the engine; engine temperature; and, engine maintenance.
Using a NEBECRAS in place of a diesel engine minimizes or eliminates the above factors, allowing more control over the quantity and composition of the diesel exhaust.
Under normal diesel engine operating conditions, carbon monoxide (CO), hydrocarbons (HC), and aldehydes are generated in the exhaust as the result of incomplete combustion of fuel. A significant portion of exhaust hydrocarbon also is derived from the engine lube oil. Nitrogen oxides (NOx) are generated from nitrogen and oxygen under the high pressure and temperature conditions in the engine cylinder. NOx consists mostly of nitric oxide (NO) and a small fraction of nitrogen dioxide (NO2). Sulfur dioxide (SO2) is generated from the sulfur present in diesel fuel and lubricant oil, and the concentration of SO2 in the exhaust gas depends on the sulfur content of the fuel and the lubricant oil. The FOCAS® rig is designed to burn any number of fuels to reproduce an exhaust product comprising any combination of the above listed components.
One of the main components of diesel exhaust is particulates, which generally comprise unburned carbon particulate matter comprising aggregates of dry particulates and wet particulates. The dry particulates generally comprise carbon, metal, adsorbed organic compounds (i.e., hydrocarbons), and varying amounts of sulfates, nitrates, and combinations thereof. Examples of adsorbed organic compounds are aldehydes, polycyclic aromatic hydrocarbons (also called PAH's), and combinations thereof. Unburned hydrocarbons, which generate a characteristic diesel odor, include but are not necessarily limited to aldehydes, such as formaldehyde, acrolein, and combinations thereof. Like carbon monoxide, the aldehydes are the product of incomplete combustion. The amount of sulfates in the diesel exhaust is directly related to the sulfur content of the diesel fuel. The dry particulates also may comprise trace elements, including but not necessarily limited to zinc, phosphorus, and cesium. Wet particulates generally comprise up to about 60 wt. % of the soluble organic fraction (hydrocarbons adsorbed and condensed on carbon particles), while the dry particulates are comprised mostly of dry carbon.
Diesel particulates are very fine. The primary (nuclei) carbon particles have an average diameter from about 0.01 microns to about 0.08 microns, while the aggregates have an average diameter from about 0.08 microns to about 1 microns. The actual composition of the diesel particulates depends, to some degree, on the particular engine used to produce the particulates and on its load and speed conditions. The actual composition of the particulates also depends on the thermodynamic conditions in the diesel exhaust and the particulate collection system being used. For example, under normal engine operating conditions, particles become coated with adsorbed and condensed high molecular weight organic compounds. These include unburned hydrocarbons, oxygenated hydrocarbons (ketones, esters, organic acids) and polynuclear aromatic hydrocarbons (PAH's).
The NEBECRAS is programmed to generate a diesel exhaust comprising a desired composition and average diameter of diesel particulates. Diesel exhaust produced at near stoichiometric conditions typically comprises the following components in the ranges given below:
Diesel Particulate Filter
A diesel particulate filter is any apparatus that collects and retains particulates from a diesel exhaust contacting the filter. In general, a diesel particulate filter consists of a porous substrate or ceramic fiber that traps the particulates but permits gases in the diesel exhaust to pass through. A suitable diesel particulate filter reduces the content of particulates in a diesel exhaust by about 50% or more in terms of grams per horsepower per hour (g/hp-hr), preferably by about 50% to about 90% g/hp-hr or more. A suitable diesel particulate filter traps particulates having an average diameter of about 100 nm or less.
Regarding regeneration methods, there are two basic types of diesel particulate filters, passive and active. Most passive diesel particulate filters remove particulates by collecting particles in the filter and oxidizing them during vehicle use, preferably substantially continuously. Active diesel particulate filters typically comprise one or more catalyst(s) effective to catalyze the oxidation of the particulates and/or aggregates at common engine exhaust temperatures.
Aging of Diesel Particulate Filters
Generally, diesel particulate filter aging is evidenced by a reduction in filtration efficiency. The reduction in filtration efficiency generally is due to multiple soot binding/regeneration cycles, which may lead to ash buildup in the diesel particulate filter. Aging also depends on numbers factors including but not necessarily limited to exposure time of the diesel particulate filter to the exhaust gas, the flowrate of the exhaust gas through the filter, the amount of pressure drop during use, the porosity of the filter, the filter materials used, and ambient humidity.
During aging of a diesel particulate filter, the flowrate generally is maintained at from about 0 to about 300 standard cubic feet per minute (scfm) and the exhaust temperature generally is maintained at from about 150° C. to about 650° C., typically from about 150° C. to about 300° C., for about 1 hour or more, and up to about 250 hours or more. Exposure times typically are determined according to the type of diesel particulate filter being tested, the components of the exhaust gas product, the desired aging conditions to be simulated, and combinations thereof.
Once desired aging requirements have been met, the diesel particulate filter is evaluated and/or regenerated.
Regeneration of the Diesel Particulate Filter
Regeneration of the diesel particulate filter involves removal of the particulate matter from the filter such that the final diesel exhaust, or the exhaust produced by passing the diesel exhaust through the diesel particulate filter, meets applicable EPA guidelines.
Generally, the exhaust gas temperature is increased to a temperature sufficiently high to autoignite and sustain combustion of the particulate matter on the filter. Regeneration temperatures generally are from about 300° C. to about 650° C., preferably about 350° C. or higher for catalyzed diesel particulate filter depending on catalyst formulation, and about 600° C. or higher for most uncatalyzed diesel particulate filters. The contaminant particulates generally must attain a minimum temperature of about 500° C. to about 650° C., preferably from about 550° C. to about 650° C., most preferably from about 585° C. to about 625° C. to autoignite and sustain combustion. The desired temperature is determined by factors including, but not necessarily limited to the type of diesel particulate filter being tested, the fuel sulfur levels, NOx levels, O2 levels, soot levels, and combinations thereof. The NEBECRAS produces diesel exhaust at temperatures of up to about 650° C., which is sufficiently high to desulfurize a component.
For rapid oxidation of the particulate matter, there must be sufficient free oxygen available, preferably from about 3 vol. % to 20 vol. % of the exhaust stream. The temperature and oxygen levels are maintained until the regeneration is complete, which typically requires about 20 minutes or less. During typical vehicle operation, active regeneration of the diesel particulate filter is needed regularly, depending on the engine, exhaust catalyst, and diesel particulate filter performance. The NEBECRAS may be programmed to reproduce a desired aging cycle and/or a desired regeneration cycle, alone or in combination, once or multiple times, as desired.
The regeneration preferably is effective to remove or oxidize a sufficient quantity of particulate matter from the diesel particulate filter to meet EPA Tier 1 Emission Standards for Passenger Cars and Light-Duty Trucks, FTP 75, g/mi:
1Useful life 120,000 miles/11 years for all HLDT standards and for THC standards for LDT (light duty truck)
Abbreviations:
THC-total hydrocarbons
NMHC-non-methane hydrocarbons
PM-particulate matter
LVW-loaded vehicle weight (curb weight + 300 lbs)
ALVW-adjusted LVW (the numerical average of the curb weight and the GVWR)
LLDT-light light-duty truck (below 6,000 lbs GVWR)
HLDT-heavy light-duty truck (above 6,000 lbs GVWR)
Preferably, the regeneration is effective to remove or oxidize a sufficient quantity of particulate matter to meet Tier 2 Emission Standards FTP 75, g/mi:
*average manufacturer fleet NOx standard is 0.07 g/mi
Abbreviations:
NMOG-non-methane organic gases
HCHO-formaldehyde
aBin deleted at end of 2006 model year (2008 for HLDTs)
bThe higher temporary NMOG, CO and HCHO values apply only to HLDTs and expire after 2008
cAn additional temporary bin restricted to MDPVs, expires after model year 2008
dOptional temporary NMOG standard of 0.195 g/mi (50,000) and 0.280 g/mi (120,000) applies for qualifying LDT4s and MDPVs only
eOptional temporary NMOG standard of 0.100 g/mi (50,000) and 0.130 g/mi (120,000) applies for qualifying LDT2s only
f50,000 mile standard optional for diesels certified to bin 10
Persons of ordinary skill in the art will recognize that many modifications may be made to the present application without departing from the spirit and scope of the application. The embodiment described herein is meant to be illustrative only and should not be taken as limiting the application, which is defined in the claims.
The present application is a continuation-in-part of U.S. patent application Ser. No. 10/213,890, filed Aug. 6, 2002, published May 1, 2003 as US 2003-0079520 b 1; (pending), incorporated herein by reference. The present application also is related to application Ser. No. 10/457,916, published Jan. 15, 2004 as US 2004-0007056 A1 (pending); application Ser. No. 10/439,146, published Feb. 12, 2004 as US 2004-0025580 A1 (pending); application Ser. No. 10/458,023, published Feb. 12, 2004 as US 2004-0028588 A1 (pending); and, application Ser. No. 10/847,034, filed May 17, 204 (pending).
Number | Date | Country | |
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Parent | 10213890 | Aug 2002 | US |
Child | 10917245 | Aug 2004 | US |