1、 SURFACE VEHICLE STANDARD J2992 APR2015 Issued 2015-04 FTIR Gas Analyzer Performance Evaluation / Qualification for Automotive Testing RATIONALE Over the past several decades, manufacturers have made great strides in reducing emissions and improving fuel efficiency of the modern internal combustion
2、engine. Integral to these improvements has been the use of various emissions monitoring equipment to test, verify and certify the improvements. As industry compliance standards become ever more stringent, the need for new capabilities has forced automotive emissions engineers to utilize alternate te
3、chnologies for monitoring gaseous emissions. The Fourier Transform Infrared (FTIR) gas analyzer is one example of a technology that shows much promise in meeting the needs of the modern emissions engineer. As use of FTIR analyzers become more wide-spread in both R heavy duty on road; non road, stati
4、onary, and marine diesel; large and small non road and stationary spark or compression ignition engines; vehicles such as automobiles and motorcycles; and others as stated in the final document. EPA Title 40: Protection of Environment, Chapter 1, Subchapter D, Part 136 Appendix B - Definition and Pr
5、ocedure for the Determination of the Method Detection Limit Federal Register Volume 76, No. 179 / Thursday, September 15, 2011 / Rules and Regulations Updates for PART 1065 Engine Testing Procedures: Pages 57437 57470. SAE INTERNATIONAL J2992 Issued APR2015 Page 5 of 38 3. DEFINITIONS 3.1 TERMS 3.1.
6、1 Electronic Code of Federal Regulations eCFR is the latest revisions of the EPA methods are stored and available for public access. 3.1.2 Flow Weighted Mean Concentration FWMC is the concentration value that is expected during the actual engine testing. Flow-weighted mean is the mean of a quantity
7、after it is weighted proportional to the corresponding flow rate. For example, if a gas concentration is measured continuously from the raw exhaust of an engine, its flow-weighted mean concentration is the sum of the products of each recorded concentration value times its respective exhaust flow rat
8、e, divided by the sum of the recorded exhaust flow rates. Refer to EPA Part 1065.602 for information needed to estimate as well as how to calculate flow-weighted means. While EPA Part 1065 references FWMC, this document will reference the Concentration Range that is specified by the specific instrum
9、ent manufacturer in order to ensure that the FTIR will span the ranges that will be required for each particular engine test. 3.1.3 Range Range as defined in this document is the concentration values in PPM or % on a volume basis, listed from Low to High over which the FTIR instrument is valid. The
10、range is depicted in form of 0 100 in this document. Multiple ranges can be used in the case of a widely varying process and the performance verification must be tested at each of the specified ranges if they are to be used together. 3.1.4 Rise Time Time it takes the FTIR response to rise / increase
11、 from 10% up to 90% of the final reading (t10 t90). 3.1.5 Fall Time Time it takes the FTIR response to fall / decrease from 90% down to 10% of the final reading (t90 t10). 3.1.6 Signal to Noise Ratio SNR is a combination of signal strength and detector noise. Since FTIRs are detector noise limited t
12、he noise component is generally attributed to the detector which is constant for constant time, so by increasing the signal or light intensity there is then a direct increase in SNR. 3.1.7 Tracer Gas A gas component that is used as an “internal standard” to verify that the gas sample is reaching the
13、 FTIR as well as to provide accurate dilution rates if needed. This component is generally not present in the emissions being tested or is present in very low concentrations and it must not be retained by the sampling system. Examples include SF6, CH4, NO, and CO2. 3.1.8 Standard The use of the Term
14、 “standard” in EPA Part 1065 refers to the particular EPA Standard that provides the regulated species as well as the maximum limit for the type of engine that is being tested. For instance see 40CFR Part 86 for Light Duty (passenger vehicles), Heavy Duty Engines, Light Duty Trucks, etc. The relevan
15、t emission values are defined by the actual standard part for each category. 3.1.9 Standard Usage Flow Rate Refers to the sample flow rate going to the FTIR analyzer. SAE INTERNATIONAL J2992 Issued APR2015 Page 6 of 38 3.2 ABBREVIATIONS The abbreviations used in the document have the following meani
16、ngs in both capital and lower case. AU = Absorbance Unit CFR = Code of Federal Regulations eCFR = Electronic Code of Federal Regulations FWMC = Flow Weighted Mean Concentration LPM = Liters Per Minute NONMHC = Non-oxygenated non-methane hydrocarbons SEE = Standard Error of the Estimate SNR = Signal
17、to Noise Ratio 4. INSTRUMENTATION 4.1 Gas Blending System A gas blending system consists of either (1) a gas divider which has fixed intervals for blending with a matrix gas or (2) a series of mass flow controllers and / or fixed orifices. 4.2 Fourier Transform Infrared Spectrometer (FTIR) The FTIR
18、must be capable of at least 1Hz data acquisition. Contact the instrument manufacturer or use published data to determine what the differences are between instrument detectors, other components as well as different instrument manufacturers to ensure the FTIR will meet the needs of the test. 4.3 Calib
19、ration Cylinders a. Certified dual component cylinders for calibration linearity testing is a single analyte in N2 or Air balance gas as described by EPA (see reference later in document). b. Certified multi-component cylinder is a mixed blend of analytes (as well as a reference tracer gas component
20、) in N2 or Air balance as described by EPA (see reference later in document). 4.4 Extractive Techniques In both cases shown below, it is prudent to install a heated filter at or near the probe end to reduce the amount of particulate matter or volatiles condensing in the lines or on the FTIR mirrors.
21、 4.4.1 Pushing Gas into the Analyzer Example Schematic Layout of Sample Extraction via Pushing the gas sample through the FTIR. Blue lines indicate no heating required while red lines require heating to 191 C 5 C. See Figure 1. SAE INTERNATIONAL J2992 Issued APR2015 Page 7 of 38FTIRProbeCellN2 Purge
22、Span & Zero Overflow Gas LineHeated Sample LineSample PumpBackflushVENTDrainSpan GasesZero Gas (N2)Heated FilterShut off for Leak CheckFigure 1 - Sample extraction via pushing of the gas 4.4.2 Pulling Gas into the Analyzer Example Schematic Layout of Sample Extraction via Pulling the gas sample thro
23、ugh the FTIR. Blue lines indicate no heating required while red lines require heating to 191 C 5 C. See Figure 2. FTIRProbe CellSpan GasesZero Gas (N2)N2 PurgeSpan & Zero Overflow Gas LineHeated Sample LineVENTSample PumpDrainBackflushHeated FilterShut off for Leak CheckFigure 2 - Sample extraction
24、via pulling of the gas 4.5 Experimental Considerations 4.5.1 FTIR Calibrations are pressure sensitive a. Pushing a sample through the FTIR allows for the internal pressure to be at or near ambient pressure. b. Pulling a sample through the FTIR lowers the overall internal pressure. c. In order to red
25、uce calibration errors due to pressure, the gas reaching the FTIR gas sampling cell should be within 10% of the pressure at which the calibration method was created. 4.5.2 FTIR Calibrations are temperature sensitive In order to reduce calibration errors due to temperature, the gas reaching the gas c
26、ell should be at 191C 5 C or within 5 C of temperature at which the calibration was created. SAE INTERNATIONAL J2992 Issued APR2015 Page 8 of 38 4.5.3 Span Gas Line The Span & Zero overflow gas line is shown above as a dual core heated line but the lines can be completely separate. 4.5.4 Standard Sa
27、mpling Component Considerations All of the mechanical components required to deliver a Hot / Wet sample to the FTIR without loss of any engine exhaust emissions components as well as components required for verification testing, such as heated lines, filter, pump, probe, by-pass, flushing, etc. a. /
28、RZIORZVVWHPVDVUHIHUHQFHGKHUHLQDUHIRUIORZUDWHVOSPZKLOHKLJKIORZVVWHPVUeference flow rates 30 lpm. b. Avoid all cold spots prior to the gas sample entering the FTIR and maintain the gas temperature within 191 C 5 C. c. In order to reduce analysis errors it is suggested that the gas cell temperature sho
29、uld be kept at 191 5 C or within 5 C of the calibration temperature. d. In order to reduce analysis errors it is suggested that the gas cell internal pressure should be kept within 10% of the calibration method pressure. Note that for gas components with very narrow lines such as CO and CO2 the gas
30、cell pressure might need to be held to within 5% of the calibration method in order to reduce calibration errors. 4.5.4.1 Particulates in the gas stream a. The particulate filter location can be either inside or outside of the analyzer but it must be heated b. To avoid less frequent gas cell cleanin
31、gs, place a second heated filter at or near entrance to the FTIR. 4.5.4.2 Filter considerations: a. Filter must be used to avoid particulate matter or volatiles collecting on the optics of the gas cell. b. Must be heated. c. Must not retain any components that are to be certified by the FTIR 1. Filt
32、er and filter material should be tested to ensure minimum adsorption of the component of interest by running the sampling system and measuring the system response time. 2. Sample system validation for component retention must be performed as part of the system performance tests as listed below in th
33、is document. 3. Must allow for maximum throughput to avoid sample retention. 4. Borosilicate glass or Quartz is generally a good filter material to use especially when working with NH3 analysis. d. Must be changed on a regular basis using good engineering practice 1. For example, monitoring the pres
34、sure or flow rate across the sample train on a daily basis prior to use is a good way to determine if the filters are plugged. 2. If the pressure or flow rate drops by more than 10% of the initial set up value then replace the filters. SAE INTERNATIONAL J2992 Issued APR2015 Page 9 of 38 e. Coarse fi
35、lter placed at or near the probe 1. Greatly reduces particulate matter deposition within the lines 2. Need to monitor flow rate or pressure closely to determine clogging of filter 3. Should be at least 1 pore size or smaller f. Fine filter placed at or near the FTIR or pump (if on the inlet of the F
36、TIR) 1. Greatly reduces particulate matter deposition on the FTIR gas cell mirrors and windows 2. Requires more frequent sample line backflush or cleaning 3. Need to monitor retention of any of the components as particulate matter builds up 4. Should be at least 0.1 pore size or smaller to reduce th
37、e deposition of particulate matter on the gas cell windows. g. Use good engineering judgment with respect to sizing the particulate filter. 1. Contact the instrument manufacturer for input on system requirements. Too coarse of a filter will require more frequent cleaning of the analyzer gas cell. 4.
38、5.4.3 Sample line considerations: a. Maintain gas sample temperature within 191 C 5 C at all times to avoid condensation of sample gas component b. Line material must minimize component retention as well as avoid reactions or diffusion 1. Stainless steel (SS) electropolished, SS corrugated, SilcoNer
39、t coated and Per-Fluro Alkoxy (PFA) are the preferred line material when working with components such as ammonia that have a tendency to adhere to the walls of the sampling lines. 2. Lines should be cleaned on a regular basis to avoid particulate matter build up which can result in reaction with the
40、 gas molecules that are being monitored. c. Flow rates should be high enough to ensure that the analyte does not adhere to the sample line wall d. Should be as short as possible to reduce sample delay time 4.5.4.4 Sample Pump considerations a. Use oil free pumps and make sure to recondition the pump
41、 following the pump manufacturers recommendations for maximum run time b. Wetted material should be stainless steel, Teflon, Teflon coated or ceramic to avoid component retention c. If sample pump is placed upstream of FTIR 1. The pump head must be heated to 191 C 5 C 2. A fine filter can be used at
42、 the inlet side of the pump 3. Heated line must connect the outlet of pump to FTIR d. If sample pump is placed downstream of FTIR 1. If the pump head is not heated then a coalescing filter or some other configuration is needed to make sure all condensing liquids are removed before the gas stream ent
43、ers the pump. 2. If the pump is an air jet type, then a coalescing filter is only required if additional dry analyzers are included in the stream or if a flow measurement is made just upstream of the air jet exhaust. SAE INTERNATIONAL J2992 Issued APR2015 Page 10 of 38 5. INSTRUMENT FUNCTION VALIDAT
44、ION PERFORMANCE This section is based upon the Instrument Manufacturers suggested time scale but at a minimum would need to be performed and documented upon initial installation of the equipment and after any maintenance performed which would affect the sample train or the FTIR light path. 5.1 Valid
45、ate the System Hardware Parameters a. The FTIR and sampling system must be powered up and running properly. 1. The detector must be cooled to the manufacturers specified running temperature, the FTIR sample cell and the sampling system and lines must be heated to 191 C 5 C. 2. Dry N2 or Zero Air mus
46、t be flowing through the gas cell using a span port if one is available or a diverter valve placed at the outlet of the sample pump or gas cell inlet. 3. Use the manufacturers specified flow rate or best engineering practice 4. Dry N2 or Zero Air should be flowing through the optical purge compartme
47、nts or a vacuum must be pulled on these components to remove the ambient air interferents. b. The full sampling system should be checked for cold spots. Use good engineering practices to determine if cold spots exist. x For example a known amount of NH3 blended with ambient air can be pulled through
48、 the entire system. A cold spot exists if the known amount of NH3 does not reach the FTIR c. Use the established T50 timing for the sampling system with respect to NH3 as the test parameter pass or fail. A reference tracer gas such as CO2 may also be used with the NH3 to ensure delivery of gas throu
49、gh the full sampling system. d. With the sample gas flowing check that the sample cell pressure is within 10% of the method pressure (see Section 5.5.4 for Note on CO and CO2). 5.2 Verify the System Hardware Parameters a. See Section 6.1 above for relevant parameters b. Verify FTIR and Sampling System Temperature Settings c. Verify FTIR and Sampling System Pressure Settings 5.3 Validate the System Signal a. Validate the
