saej215v002
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3.10Abbreviations Used
°C—Degrees Celsius
CHA—Continuous hydrocarbon analyzer
conc—Concentration
cm—Centimeters
diam—Diameter
Exh—Exhaust
FID—Flame ionization detector
g—Gram(s)
h—Hour
H2—Hydrogen
HC—Hydrocarbon
He—Helium
Hg—Mercury
ID—Internal diameter
kg—Kilogram
L—Liter(s)
m—Meter(s)
max—Maximum
min—Minimum, minute(s)
mL—Milliliter(s)
kW—Kilowatt
N2—Nitrogen
O2—Oxygen
OD—Outside diameter
ppm—Parts per million
ppmc—Parts per million carbon
s—Second(s)
%—Percent
4.Section—This report is divided into the following sections:
3. Definition of Terms and Abbreviations
5. Equipment
6. Instrument Operating Procedures
7. Engine Test Procedure
8. Information to be Recorded
9. Calculations, Data Analysis, and Report
10. Supplementary Discussion
5.Equipment
5.1Instruments—The Continuous Hydrocarbon Analyzers (CHA) recommended for measuring unburned
hydrocarbons in diesel exhaust can be of a positive pressure burner type (Figure 1) or a reduced pressure burner type (Figure 2). In both systems, a fraction of the engine exhaust stream flows through a heated sampling line and filters to the sample pump inlet. The sample stream is split with a fraction of the exhaust stream sample diverted to the burner. The sample split is made upstream of the pump inlet in the reduced pressure system and downstream of the pump outlet in the positive pressure system. The burner in both systems (Figures 1 and 2) is a flame ionization detector; the system components are described in 5.2. The system employed should be capable of measuring hydrocarbons over a range of 10 to 6000 ppmc and have the ability to follow rapid changes in hydrocarbon concentration. The response of the total sampling system to diesel exhaust should be at least 90% of full scale within 20 s for a 100% of full scale step input to the system.
FIGURE 1—CHA POSITIVE PRESSURE BURNER
FIGURE 2—CHA REDUCED PRESSURE BURNER
5.2Component Description—The following components are utilized in the CHA of Figures 1 and 2. All parts are
common to both systems unless otherwise stated.
5.2.1Pressure regulators, R1 and R2, pressure gages, G1 and G2, and capillary tubes or restrictors, C1 and C2,
to control air and fuel flows to CHA detector burner. C1 and C2 should be maintained at constant temperature ±2 °C.
O PTIONAL—Flow controllers and flowmeters may be used in place of R1, R2, G1, and G2.
5.2.2Flame ionization detector, FID, capable of operating in the range of 175 to 200 °C.
5.2.3Electrometer, E, coupled to a recorder, meter, or other comparable readout device may be used.
5.2.4Constant temperature oven, O, for detector and sampling system components, capable of operating in the
range of 175 to 200 °C and holding temperature ±2 °C.
5.2.5Stainless steel probe, SP, to obtain sample from the exhaust system. A closed end, multihole static probe
extending at least 80% across the exhaust pipe is recommended. The total area of the holes should be equal to or less than the cross-sectional area of the probe. A typical hole ID used is 0.15875 cm. The probe location should be governed by the purpose of the test. For routine measurements, the probe should be located in the exhaust line at a distance of 1 to 3 m from the exhaust manifold outlet flange or the outlet of the turbocharger. Longer distances can be used if the results are equivalent to those obtained at the specified 1 to 3 m distance.
5.2.6Heat prefilter, F1, in line to remove soot and reduce acoustical effects in sample flow (optional). Spun Pyrex1
glass is one example of a suitable filter material.
5.2.7Sampling line, SL, must be heated to maintain the gas temperature to ±10 °C of the oven compartment
temperature and never less than 175 °C during sampling. Construction of the line should be of stainless steel and/or Teflon.1
A 0.635 cm OD or 0.9525 cm OD line is recommended. A response time of 20 s or less is desired. To test
response, inject span gas sample at the stack inlet (F1) and measure the time elapsed before a deflection of 90% of stabilized response is observed on the readout meter or recorder. The gases used to check response should give a deflection of at least 50% of full scale.
5.2.8Temperature readout, T1, of sample stream entering oven compartment (minimum temperature 175 °C). 5.2.9Suitable valving, SV1, for selecting sample, span gas, or air zero gas flow to the system. The valve(s) should
be in the oven compartment or heated.
O PTIONAL—Use external pump to supply sufficient heated clean air to flush the entire system when not calibrating or sampling.
5.2.10Valves, V1 and V2, and gages, G3 and G4, to regulate calibration gas and air zero gas.
5.2.11Coils, H1 and H2, to preheat calibration gas and air zero gas.
O PTIONAL—Introduce gases into sampling line near probe inlet.
5.2.12Filter, F2, to remove particulates. A 7 cm diam glass fiber type filter disc or equivalent is suitable. Filter
should be readily accessible and changed daily or more frequently as needed.
1.Registered trademark.
5.2.13Regulating valve, V3, (reduced pressure system only) to control pressure in sample line.
5.2.14Sample pump, P1, and motor, M1. In the positive pressure system, the pump head must be heated to oven
temperature. In the reduced pressure system, the pump and motor are outside the oven. The pump used in the positive pressure system should not affect the emission concentration or composition.
5.2.15Capillary tubing or restrictor, C3, to control sample flow to the detector.
5.2.16Pressure gage, G5, to measure in sample line. Pressure tap should be located near the capillary line (C3)
takeoff and designed to minimize velocity effects.
5.2.17Pressure regulator valve, V4, to control pressure in sample line and flow to detector. This valve could be
connected across the detector in the vacuum system. The valve should be maintained at a temperature above the dew point.
O PTIONAL—Use a fixed restrictor and vary the pump speed to control the pressure.
5.2.18Vacuum gage, G6, (reduced pressure system only) to measure pressure in detector or cannister.
O PTIONAL—Combine with G5 and use one gage to measure pressure drop across detector
5.2.19Surge tank, S1, (reduced pressure system only) to stabilize flow tank, if required, should be sized for system.
A 1 to 2 L tank is suggested for 10 L/min sample flow.
5.2.20Flowmeter, FL1, (reduced pressure system) to measure sample bypass flow. Maintain above dew point.
Flowmeter is optional on positive pressure system.
5.2.21Vacuum regulator, V5, (reduced pressure system only) to control vacuum in detector.
5.2.22Oven temperature readout, T2, thermocouple or equivalent.
6.Instrument Operating Procedures—Follow the instrument manufacturer's startup and operating procedure
for the particular type CHA. In addition, the following minimum calibration and instrument checks should be included.
6.1Calibration and Instrument Checks
6.1.1I NITIAL—The following instrument checks may have been determined by the manufacturer or user. If not,
they should be evaluated prior to instrument use.
6.1.1.1Optimize Detector Response
a.Set burner fuel and air settings as prescribed by the manufacturer. Ignite the burner. Set sample flows
recommended by the manufacturer.
b.Set the oven temperature at 175 to 200 °C. Allow system to reach equilibrium. This usually takes at
least 1/2 to 2 h.
c.Determine the optimum burner fuel flow for maximum response. Introduce a constant continuous
concentration of propane in N2. Use about 500 ppmc hydrocarbon concentration or a concentration
that would be a mid-point in the normal operating range. Vary burner fuel flow and determine peak
response. Select an operating flow that gives maximum response and the least variation in response
with minor flow variations. Normally, there is a plateau in the region of peak response Figure 3. Use
best judgment in selecting optimum fuel flow.
FIGURE 3—EFFECT OF HYDROGEN FLOW
d.Determine optimum air flow. Set burner fuel flow as determined in 6.1.1.1(c) and vary air flow.
Although less critical than burner fuel flow, nonoptimized conditions may reduce quantitative accuracy.
If air flow is too low, response is low. High air flow may result in increased noise. A typical curve is shown on Figure 4. Select desired air flow and, if it is significantly different than that used in 6.1.1.1(c), repeat step (c).
e.Measure optimum flows accurately and record.
FIGURE 4—EFFECT OF AIR FLOW
6.1.1.2Determine Oxygen Response Curve of CHA—Variation in oxygen concentration in diesel exhaust (excess
air) causes variation in detector response. The magnitude of this oxygen effect has to be determined and minimized.
a.Ignite burner and set flows as determined in 6.1.1.1. Set oven temperature as in 6.1.1.1 and allow at
least 1/2 h after heatup for system to reach equilibrium.
b.Introduce air zero gas and zero the analyzer and span the analyzer with propane in air.
c.Determine oxygen response by introducing propane calibration gases in the following carrier gases:
100% N2, 95% N2/5% O2, 90% N2/10% O2, air.
The concentration level of the propane should equal the expected upper HC level, or a nominal
concentration of 350 ppm ± 50 ppm. The HC concentration should be known within ±1% of the true
value. (See 10.1.) The oxygen values of the mixtures should be 5% ± 1%, 10% ± 1%, and air.
Recheck zero and gain after each calibration gas is used. If either has changed more than 1% of full
scale deflection rezero and/or adjust gain and repeat the test.
https://www.wendangku.net/doc/56941493.html,ing propane in air as the baseline for O2 correction, plot a curve of oxygen correction versus the
percent of oxygen in the sample Figure 5.
FIGURE 5—FID OXYGEN INTERFERENCE
If correction is less than ±2% over the normal operating range of the diesel, no O2 correction need be
applied to the observed HC concentrations.
If the correction is greater than ±2%, apply an O2 correction to all measured values as follows:
Corrected ppmc = (observed ppmc) x O2 correction
(Eq. 1)
e.Check the effect of O2 by using a propane concentration typical of the expected lower HC level that will
be encountered during engine tests, or about 100 ppmc, whichever is smaller. If the measured results
are significantly different from the known values, apply the O2 correction factor determined in
6.1.1.2(d).
f.If the oxygen response correction in 6.1.1.2(d) and (e) is greater than 4% over the normal O2 range
encountered in diesel exhaust (Figure 5), see 10.2.
6.1.1.3Determine Linearity of CHA
a.Ignite burner. Set flows as determined in 6.1.1.1 and 6.1.1.2.
b.Set temperatures as in 6.1.1.1 and allow at least 1/2 h after heatup for system to reach equilibrium and
set instrument gain with propane in air.
https://www.wendangku.net/doc/56941493.html,ing propane in air, vary the HC concentration over the operating range using HC concentrations of
about 1/3, 2/3, and full scale as a minimum. If more than one attenuation range is used, establish
linearity by checking at least two points other than zero for each additional range used. If the response
is not linear within ±2% of full scale, check calibrations and/or analyzer.
6.1.1.4System Operating Temperature
a.The initial operating temperature recommended is 175 to 200 °C.
b.The optimum system operating temperature should be checked as discussed in 10.3.
6.1.2 AND 6.1.3 SAMPLE PRESSURE CONTROL SYSTEM CHECKS—The accuracy of the sample back
pressure regulator and control system should be checked by connecting a typical span gas and adequate pressure gage to the sample inlet connection on the instrument module or in place of the sample probe.
Vary the span gas supply pressure over the range anticipated at the exhaust stack probe location. If the response varies by more than 2%, adjust or replace pressure regulator valve V4 to maintain constant line pressure (indicated on G5).
6.1.2M ONTHLY—The following checks are to be made monthly or more frequently if there is any doubt regarding
accuracy of HC values.
6.1.2.1Ignite burner. Set air, fuel, and sample rates as determined in 6.1.1.1 and 6.1.1.2.
6.1.2.2Set system temperatures as determined in 6.1.1.4. Allow at least 1/2 h after heat-up for the system to
come to equilibrium.
6.1.2.3Introduce air zero gas and zero the analyzer.
6.1.2.4Check oxygen effect on response by introducing calibration gases of propane in air, propane in nitrogen,
and propane in 90% N2/10% ± 1% O2. The hydrocarbon concentration should be known to within ±1% of true value.
6.1.2.5Recheck zero after measuring each calibrating gas. If zero varies by more than 1% of full scale, rezero
and repeat step 6.1.2.4.
6.1.2.6Compare oxygen response values with previous curves. Any significant (±10%) change in response
reflects a change in the burner operating characteristics; that is, air, fuel, or sample flow rates. Check for leaks or plugged capillaries and remeasure flows. If change in response cannot be resolved, establish a new oxygen response curve as per 6.1.1.2.
6.1.2.7Check calibration curve or response data as per 6.1.1.3(c).
6.1.3D AILY—Prior to daily testing, carry out the following:
6.1.3.1Ignite burner, set air, fuel, and sample rates as determined in 6.1.1.1 and 6.1.1.2.
6.1.3.2Insert clean filters.
6.1.3.3Set system temperatures as determined in 6.1.1.4. Allow at least 1/2 h after heat-up for the system to
come to equilibrium.
6.1.3.4Introduce air zero gas and zero the analyzer.
6.1.3.5Introduce HC span gas (propane in air) appropriate to anticipated operating range. (See 10.4). Check
agreement with calibration curve. (N O TE—Sample flow for air zero gas and calibration gas should be the same as exhaust sample flow.) If this value does not agree with calibration curve, adjust instrument gain so that response agrees with calibration curve. If sufficient time has been allowed to stabilize the instrument and the change in gain or response is more than 5% of full scale, then recheck oxygen interference and linearity per 6.1.1.2 and 6.1.1.3(c).
6.1.3.6Conduct analyses—Recheck zero after each analysis. If zero changes by more than 2% or more of
measured value, rezero and repeat test.
C AUTION—Do not mistake HC hangup for zero change. Check for contamination in line and probe at
normal instrument operating conditions by drawing in either clean air or air zero gas. A reading of 20 ppmc or more indicates that the probe and/or line should be cleaned or replaced.
6.1.3.7At the conclusion of the test, backflush the system to clean out the sampling line preferably with
hydrocarbon-free air or nitrogen.
7.Engine Test Procedure—The following test procedure is recommended for emission measurements at
steady-state operating conditions. The engine operating cycle is not dictated by this procedure and the engine break-in, pretest conditioning, and measurement procedure may be modified depending on the purpose of the test; that is, emission certification or routine laboratory development test.
7.1Engine Break-In Procedure—The engine shall be run-in according to the manufacturer's recommendation. 7.2Emission Measurement Procedure
7.2.1Connect sample line to instrument and check for leaks by blocking off end of sample line or probe. A leakage
rate greater than 1% of the system flow recommended by the manufacturer shall be corrected before proceeding. Install probe in exhaust system and connect to sample line if not done so, to check for leaks.
Check for contamination in line at normal instrument operating conditions (see 6.1.3.6).
7.2.2Start the engine and warm it up. Complete warm-up at rated speed and full load for 10 min or until all
temperatures and pressures have reached equilibrium.
7.2.3Operate for at least 20 min in each mode for emission stabilization, allowing last 5 min for emission
measurement.
7.2.4Measure hydrocarbon emission as follows:
7.2.4.1Follow daily instrument procedure (see 6.1.3.)
7.2.4.2Analyze exhaust for at least 5 min during each mode.
7.2.4.3Check and reset zero and span after each mode; if either changed more than 2% of measured response,
repeat the mode.
7.2.5C HART R EADING —HC determination as follows:
7.2.5.1Locate last 3 min of each test and average the chart reading over this 3 min period.
7.2.5.2Determine the concentration of hydrocarbons as ppmc at each point by Equation 2 or the calibration curve from 5.1.1.1(c).
(Eq. 2)7.2.5.3
Correct concentration obtained in 7.2.5.2 for oxygen effect as determined in 6.1.1.2.7.2.5.4
Additional mass calculations may be required, depending on the purpose of the https://www.wendangku.net/doc/56941493.html,rmation to be Recorded—The following information should be included as part of the recorded data for
each test performed.
8.1Test number
8.2
Engine or vehicle tested:
a.
Identification number.b.Brief description including type precombustion or direct inject (PC or DI), naturally aspirated or
turbocharged (NA or TC), 2- or 4-cycle, bore, and stroke.8.3
Date.8.4
Instrument operator and test engineer or vehicle operator.8.5
Starting and finishing time.8.6
Analyzer identification.8.7
Ambient temperature, start, and finish of testing.8.8
Number of engine conditions tested.8.9Atmospheric pressure, start, and finish of testing.
8.10Relative humidity, start, and finish of testing.
8.11Fuel used, identification number, and type (No. 1 or No. 2 diesel, etc.).
8.12Lube oil used, identification number, and type.
8.13Oven temperature.
8.14Sample line temperature.
8.15Burner fuel and flow rate and/or pressure.
8.16Air flow rate and/or pressure.
HC conc.Measured response Span gas response/ppmc in span gas
----------------------------------------------------------------------------------------------------=
8.17Sample flow rate, pressure, and/or pressure drop in capillary.
8.18Engine data at test point.
8.19Analysis data at each test point.
8.20Recorder chart notations:
a.
Items 8.1, 8.2, 8.3, and 8.4.b.
Identify zero traces calibration or span traces, steady-state test point identification, start, and finish of each condition.c.
Instrument range used at each test point.d.
Time of analysis.e.
Remarks.9.Calculations, Data Analysis, and Report—Data from Section 8 should be checked for any obvious errors.
The exhaust gas concentration of hydrocarbons as measured in this procedure are determined by Equation 3:
(Eq. 3)where:
(O 2 corr) = Oxygen correction determined in 6.1.1.2
Mass calculations can be made using the ppmc and the calculated or measured engine exhaust flow rate (see Equation 4):
(Eq. 4)
10.Supplementary Discussion
10.1Calibration Gases—There are several suppliers of the calibration gases used in this procedure. The gases
can be obtained with an analysis by the supplier indicating an accuracy of 1% or better. However, it is recommended that internal cross checks be made on all incoming standards. If a difference greater than 1% is indicated, comparison with a reference standard is advised. Chromatographic checks as appropriate to check total HC content are recommended.
10.2Reducing the Oxygen Effect on Response—The oxygen correction should be reduced to attain the limits
described in 6.1.1.2. The oxygen effect on response for a particular FID burner design may depend on:
a.
The type of burner fuel used, for example, H 2, 40% H 2/60% N 2, or 40% H /60% He.b.
The sample flow rate into the burner.c.The air and fuel rate to the burner.
The oxygen effect may be reduced by changing one or more of the previous variables. The effect of these variables should be investigated in the order previously mentioned using the procedures described in 6.1.1.1and 6.1.1.2. It is recommended that a different detector be obtained if the oxygen correction factor over the normal oxygen range found in diesel exhaust exceeds 10%.
HC conc., ppmc Measured diesel response Span gas response/ppmc in the span gas
--------------------------------------------------------------------------------------------------------------(O 2 corr)HC, g/h = 2.87 (102–) · (Mass exh, kg/m)
10.3Determination of Optimum System Operating Temperature—A 175 to 200 °C system temperature is
recommended as a satisfactory initial operating temperature. CHA operating temperatures ranging 175 to 200°C have been used by various researchers. An optimum temperature can be determined by the following procedure:
10.3.1Select an engine that will produce emissions in the range of 300 to 800 ppmc when operating on No. 2 diesel
fuel.
10.3.2Connect CHA for emission analysis.
10.3.3Follow normal CHA startup procedures and set system temperatures at 175 °C.
10.3.4Start engine and set engine for a steady-state, part-load condition. Check emissions. If emissions are
varying or are not in the 300 to 800 ppmc range, adjust necessary engine or instrument variables to obtain stable emission level.
10.3.5Measure emissions for at least 5 min. Check span gas and zero and determine HC value as in Section 9. 10.3.6Increase system temperatures by 25 °C increments up to 200 °C. At each temperature allow system to
equilibrate and repeat 10.3.5.
NOTE—Span gas response may change due to temperature effect on the detector. Do not adjust flows. 10.3.7Based on the results of the tests, select the lowest temperature that yields the highest HC response.
10.3.8O PTIONAL—Use a constant concentration HC generator using hexadecane or diesel fuel in place of engine in
10.3.1.
10.4Span Gas—The calibration gas used in daily testing should be propane in air. The concentration of this span
gas should be known in ppmc with an accuracy of ±2% or better. The span gas should produce a response of at least 75% full deflection of the readout instrument when operating at the same conditions as the engine emission test. It is recommended that cross checks be made on all incoming gases before use. These checks can be against established internal calibration gases or NIST standard gases.
PREPARED BY THE SAE MOTOR VEHICLE COUNCIL
Rationale—Standard is no longer needed.
Relationship of SAE Standard to ISO Standard—Not applicable.
Application—The method presented is the current recommendation for the use of flame ionization detectors to determine the hydrocarbon content of diesel engine exhaust, or exhaust of vehicles using diesel engines, when operating at steady-state. The requirements of the associated sampling system and a general procedure for a continuous measuring method are presented.
Reference Section—There are no referenced publications specified herein.
Developed by the SAE Motor Vehicle Council