Method for drive cycle simulation using non-engine based test system

Related Applications

The present application is a continuation-in-part of U.S. patent application Ser. No. 10/213,890, filed Aug. 6, 2002, now U.S. Pat. No. 7,140,874 incorporated herein by reference. This application is related to co-pending U.S. patent application Ser. No. 11/470,471 filed Sep. 6, 2006; U.S. patent application Ser. No. 11/420,393 filed May 25, 2006; U.S. patent application Ser. No. 11/326,983 filed Jan. 6, 2006; U.S. patent application Ser. No. 10/917,230 filed Aug. 12, 2004; U.S. patent application Ser. No. 10/917,245 filed Aug. 12, 2004; U.S. patent application Ser. No. 10/918,330 filed Aug. 12, 2004; U.S. patent application Ser. No. 10/847,034 filed May 17, 2004; U.S. patent application Ser. No. 10/458,023 filed Jun. 10, 2003; U.S. patent application Ser. No. 10/439,146 filed May 15, 2003, now U.S. Pat. No. 6,983,545 B2; and U.S. patent application Ser. No. 10/457,916 filed Jun. 10, 2003.

The present application relates in general to a method of using a non-engine based test system to perform emissions testing.

Vehicle based systems for performing emissions testing using Federal Test Procedures (FTP) have several disadvantages, such as driver variability and long vehicle soak times (12 hours). More precise and efficient alternative methods would be advantageous to perform FTP test procedures used in research and development work.

The present application provides a method for simulating at least one drive cycle of a vehicle using a non-engine based test system. The method comprises: providing a non-engine based test system comprising a combustor in fluid communication with a catalytic converter from the vehicle; supplying fuel and air to said combustor at an air to fuel ratio (AFR) and under conditions effective to produce a feedstream flowpath; substantially stoichiometrically combusting at least a portion of the fuel in the feedstream flowpath under conditions effective to simulate at least one drive cycle of the vehicle and to produce a simulated drive cycle exhaust product for the vehicle, the conditions being effective to prevent substantial damage to the combustor; and, collecting and analyzing the simulated drive cycle exhaust product.

FIG. 1 is a schematic diagram of the FOCAS® rig, a preferred non-engine based exhaust component rapid aging system (NEBECRAS) for use herein, described in U.S. Patent Application Publication No. 20030079520, published May 1, 2003, incorporated herein by reference.

FIG. 2 is an FTP 75 Drive Cycle Trace.

The FTP 75 vehicle emissions test was developed in approximately 1975 to measure emissions from vehicles using a chassis dynamometer. The drive trace for the FTP test is shown in FIG. 2 . In order to perform emissions testing, a vehicle is set up on a chassis dynamometer, and the specified test procedures are performed to obtain emissions values that can be used to certify a vehicle for sale. The FTP-75 test is an emissions tests procedure and is defined in the Code of Federal Regulations (CFR 40, Part 86).

The use of a vehicle-based apparatus to perform FTP test procedures creates some disadvantages, particularly in research and development work. A primary disadvantage is inefficiency. During aging (typically accelerated aging on an engine), the test stand must be brought down and the catalytic converter must be removed and installed on the test vehicle. The vehicle then is driven over the drive cycle by a human driver, and is soaked (or turned off) overnight for test preparation. Due to the time required for all of the vehicle systems to cool down to approved ambient conditions, only one cold-start FTP test can be performed per day using a vehicle-based system.

Another disadvantage of vehicle-based testing is a lack of precision. One source of reduced precision is the use of a human driver to simulate the drive cycle. Humans are susceptible to driving the test differently from day to day. Another source of reduced precision is the many variables that affect overall emissions from a vehicle. Variations exist from vehicle-to-vehicle, and day to day on the same vehicle.

The present application solves the foregoing problems by using a non-engine based test system to perform drive cycle testing. A preferred non-engine based test system is an exhaust component rapid aging system (NEBECRAS) and a method for using same to simulate vehicle-based FTP test procedures.

A preferred NEBECRAS for use in the method is the “FOCAS® rig,” described in U.S. Patent Application Publication No. 20030079520, published May 1, 2003, incorporated herein by reference. 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) an oil injection system, and (6) a computerized control system. The foregoing components are illustrated in FIG. 1 and described in detail in U.S. Patent Application Publication No. 20030079520, which has been incorporated herein by reference, and will not be described in detail herein.

The FOCAS® rig was developed to evaluate the long term effects of the individual variables on the long term performance of the catalyst. The FOCAS® rig is capable of producing a simulated exhaust gas with a composition and temperature corresponding to that produced by the internal combustion engine of a motor vehicle.

Referring now to the drawings and initially to FIG. 1 , a schematic diagram of the system is shown. An air blower 30 draws ambient air through an inlet air filter 20 and exhausts a pressurized stream of air. The air blower 30 and the mass air flow sensor 50 may be of any conventional design which will be well known to a person of ordinary skill in the art. In a preferred embodiment the air blower 30 is an electric centrifugal blower, such as a Fuji Electric Model VFC404A Ring Blower, and the mass air flow sensor 50 is an automotive inlet air flow sensor such as a Bosh Model Number 0280214001 available from most retail automotive parts stores. The volume of air supplied is set by adjusting a bypass valve 40 to produce a desired flow rate of air, which is measured by a mass flow sensor 50 .

The exhaust from the burner 60 is routed to a heat exchanger 70 . The heat exchanger 70 may be of any conventional design which will be well known to a person of ordinary skill in the art. In a preferred embodiment the heat exchanger 70 consists of two sections. The upstream section consists of a water jacketed tube. The downstream section is a vertical cross flow shell and tube heat exchanger. The vertical cross flow design minimizes steam formation and steam trapping within the cooling tubes. The heat exchanger 70 is provided with an inlet water line 80 and an outlet water line 90 which supply and drain cooling water to cool the exhaust gas to a temperature simulating that which is present at the inlet to the catalytic converter of a typical motor vehicle.

The exhaust gas is next routed to an oil injection section 110 ( FIG. 1 ). The oil injection section provides an atomized oil spray comprising oil droplets with a sufficiently small diameter to vaporize and oxidize the oil before it reaches the catalyst. The oil injection system may be located anywhere downstream from the burner.

A data acquisition and control system preferably provides a means to control ignition, air assist to the fuel injector, auxiliary air, fuel feed, blower air feed, oil injection, etc. (discussed more fully below). An example of a suitable control system would be a proportional integral derivative (PID) control loop, for example, for controlling fuel metering.

In a preferred embodiment, the data acquisition and control system is provided with a computer program to control the system and to acquire and process the signals from the measured parameters. The computer program can be written in a variety of different ways, which will be well known to persons versed in the art. The controller preferably is provided with a closed-loop fan control to maintain catalyst inlet temperature, preferably at from about −50.degree. C. to about +50.degree. C. about a setpoint temperature, preferably from about −5.degree. C. to about +5.degree. C. about a setpoint temperature. The setpoint temperature is dictated by the cycle being simulated.

The control system for the FOCAS.TM. Rig consists of a Lab VIEW-programmed PC equipped with a touch screen monitor and a multi-function DAQ card, connected to an SCXI chassis holding two SCXI 1120 multiplexing modules, one feed-through panel, and an SCXI 1160 “relay module” to monitor and record system information, and to control system electronics. Using the computer interface, the operator can switch power to the blowers and fuel pump, as well as control the air assisted fuel injectors, burner spark, oil injection, and auxiliary air, all with the touch of a finger.

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 preferred, 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 Federal Test Procedure (FTP) uses the Urban Dynamometer Driving Schedule (UDDS). The UDDS is the result of more than ten years of effort by various groups to translate the Los Angeles smog-producing driving conditions to chassis dynamometer operations, and is a nonrepetitive drive cycle covering 7.5 miles in 1372 seconds with an average speed of 19.7 mph. Its maximum speed is 56.7 mph.

As seen in FIG. 1 , the current FTP drive cycle consists of a cold-start, 505-second, cold transient phase (Bag 1 ), followed immediately by an 864-second stabilized phase (Bag 2 ). Following the stabilized phase, the vehicle is allowed to soak for 10 minutes with the engine turned off before proceeding with a hot-start, 505-second, hot transient phase (Bag 3 ) to complete the test. The drive cycle is 1874 seconds, for a distance of 11.04 miles, at an average speed of 21.2 miles per hour.

In order to perform the drive cycle using the non-engine based test system, the following features are controlled:

1) the exhaust flowrate is varied, typically in the range of from 0 to about 200 standard cubic feet per minute (scfm), to simulate the exhaust flowrates of the test vehicle throughout the FTP; 2) the exhaust gas temperature is varied, typically in the range of from about 20 to about 900° C., to simulate the exhaust gas temperatures at the catalyst inlet throughout the FTP; and, 3) the exhaust gas stoichiometry is varied, typically in the range of from about 10 to about 40 AFR, preferably from about 10 to about 20 AFR, to simulate the exhaust gas stoichiometry of the vehicle throughout the FTP.

Ideally, the FOCAS system exhaust gas mixture contains similar concentrations of hydrocarbons, carbon monoxide, and oxides of nitrogen as seen in the vehicle exhaust at any time during the FTP test. An idealized exhaust gas mixture could be created for research and development work by metering/doping the exhaust gas to create the proper component balance to match the vehicle exhaust throughout operation over the test cycle. The suitable idealized exhaust gas mixture would vary, with an example of a suitable idealized exhaust gas mixture (near stoichiometric) comprising the following components in the following ratios:

The non-engine based test system software controls all of the above parameters simultaneously throughout the simulated FTP, and is programmable to simulate any desired set of test conditions.

Throughout the test cycle, the exhaust is collected, diluted, and thoroughly mixed with filtered background air to a known constant volume flowrate using a positive displacement pump. This procedure is known as Constant Volume Sampling (CVS). A proportional sample of the dilute exhaust is collected in a sample bag for analysis at the end of the test. The emissions are mathematically weighted to represent the average of several 7.5 mile trips made from cold and hot starts. A summary of suitable cycle duration, driving distance, and average speed is given in the following Table:

Duration, Distance, Average Speed, Segment seconds miles mph Transient Phase 505 3.60 25.7 Stabilized Phase 867 3.90 16.2 UDDS Total 1372 7.50 19.7 (FTP CYCLE IS UDDS + HOT-START TRANSIENT 505)

Exhaust emissions from the FTP cover the effects of vehicle and emission control system warm-up as the vehicle is operated over the cycle. The “stabilized” phase produces emissions from a fully warmed up or stabilized vehicle and emission control system. “Hot-start” or “hot transient” phase emissions result when the vehicle is started after the vehicle and emission control systems have stabilized during operation, and are then soaked (turned off) for 10 minutes.

Weighted total emissions from the FTP at 68° F. to 86° F. ambient temperature conditions are regulated by the EPA. The only regulated pollutant for the FTP at cold conditions (20° F.) is carbon monoxide (CO). Tier 1 cold-CO level for passenger cars is 10.0 g/mile. The California LEVII emissions standards for 2004 light-duty passenger cars, intermediate life—50,000 miles (the standards which the test vehicle was certified to) are:

NMOG: 0.04 g/mile CO:  1.7 g/mile NO x : 0.07 g/mile

The weighted total mass equivalent emissions for the EPA FTP-75 are calculated as required in the U.S. EPA regulations (40 CFR 86.144-90) using the following equation:

=

The non-engine based test system, preferably a FOCAS® system, can be used for thermal aging. As a result, the burner may be deactivated at a predetermined age, the system may be cooled to ambient conditions in a matter of minutes, and then immediately after cooling, the system can be used to perform multiple simulated FTP's. The non-engine based test system can then be returned to aging, making the entire emissions test procedure very time-efficient. These advantages make it highly desirable as a research and development tool.

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.