"APPENDIX 1
MEASUREMENT AND SAMPLING PROCEDURES
1. MEASUREMENT AND SAMPLING PROCEDURES (NRSC TEST)
Gaseous and particulate components emitted by the engine submitted for testing shall be measured by the methods described in Annex VI. The methods of Annex VI describe the recommended analytical systems for the gaseous emissions (Section 1.1) and the recommended particulate dilution and sampling systems (Section 1.2).
1.1. Dynamometer specification
An engine dynamometer with adequate characteristics to perform the test cycle described in Annex III, Section 3.7.1 shall be used. The instrumentation for torque and speed measurement shall allow the measurement of the power within the given limits. Additional calculations may be necessary. The accuracy of the measuring equipment must be such that the maximum tolerances of the figures given in point 1.3 are not exceeded.
1.2. Exhaust gas flow
The exhaust gas flow shall be determined by one of the methods mentioned in sections 1.2.1 to 1.2.4.
1.2.1. Direct measurement method
Direct measurement of the exhaust flow by flow nozzle or equivalent metering system (for detail see ISO 5167:2000).
NOTE: Direct gaseous flow measurement is a difficult task. Precautions must be taken to avoid measurement errors that will impact emission value errors.
1.2.2. Air and fuel measurement method
Measurement of the airflow and the fuel flow.
Air flow-meters and fuel flow-meters with the accuracy defined in Section 1.3 shall be used.
The calculation of the exhaust gas flow is as follows:
GEXHW = GAIRW + GFUEL (for wet exhaust mass)
1.2.3. Carbon balance method
Exhaust mass calculation from fuel consumption and exhaust gas concentrations using the carbon balance method (Annex III, Appendix 3).
1.2.4. Tracer measurement method
This method involves measurement of the concentration of a tracer gas in the exhaust.
A known amount of an inert gas (e.g. pure helium) shall be injected into the exhaust gas flow as a tracer. The gas is mixed and diluted by the exhaust gas, but must not react in the exhaust pipe. The concentration of the gas shall then be measured in the exhaust gas sample.
In order to ensure complete mixing of the tracer gas, the exhaust gas sampling probe shall be located at least 1 m or 30 times the diameter of the exhaust pipe, whichever is larger, downstream of the tracer gas injection point. The sampling probe may be located closer to the injection point if complete mixing is verified by comparing the tracer gas concentration with the reference concentration when the tracer gas is injected upstream of the engine.
The tracer gas flow rate shall be set so that the tracer gas concentration at engine idle speed after mixing becomes lower than the full scale of the trace gas analyzer.
The calculation of the exhaust gas flow is as follows:
where
GEXHW
|
=
|
instantaneous exhaust mass flow (kg/s)
|
GT
|
=
|
tracer gas flow (cm3/min)
|
concmix
|
=
|
instantaneous concentration of the tracer gas after mixing, (ppm)
|
ρEXH
|
=
|
density of the exhaust gas (kg/m3)
|
conca
|
=
|
background concentration of the tracer gas in the intake air (ppm)
|
The background concentration of the tracer gas (conc
a) may be determined by averaging the background concentration measured immediately before and after the test run.
When the background concentration is less than 1% of the concentration of the tracer gas after mixing (conc
mix.) at maximum exhaust flow, the background concentration may be neglected.
The total system shall meet the accuracy specifications for the exhaust gas flow and shall be calibrated according to Appendix 2, Section 1.11.2
1.2.5. Air flow and air to fuel ratio measurement method
This method involves exhaust mass calculation from the air flow and the air to fuel ratio. The calculation of the instantaneous exhaust gas mass flow is as follows:
with A / F
st = 14,5
where
A/Fst= stoichiometric air/fuel ratio (kg/kg)
λ= relative air /fuel ratio
concCO2
= dry CO2 concentration (%)
concCO
= dry CO concentration (ppm)
concHC
= HC concentration (ppm)
NOTE: The calculation refers to a diesel fuel with a H/C ratio equal to 1.8.
The air flowmeter shall meet the accuracy specifications in Table 3, the CO2 analyzer used shall meet the specifications of clause 1.4.1, and the total system shall meet the accuracy specifications for the exhaust gas flow.
Optionally, air to fuel ratio measurement equipment, such as a zirconia type sensor, may be used for the measurement of the relative air to fuel ratio in accordance with the specifications of clause 1.4.4.
1.2.6. Total dilute exhaust gas flow
When using a full flow dilution system, the total flow of the dilute exhaust (GTOTW) shall be measured with a PDP or CFV or SSV (Annex VI, Section 1.2.1.2.) The accuracy shall conform to the provisions of Annex III, Appendix 2, Section 2.2.
1.3. Accuracy
The calibration of all measurement instruments shall be traceable to national or international standards and comply with the requirements listed in Table 3.
Table 3. Accuracy of Measuring Instruments
No.
|
Measuring Instrument
|
Accuracy
|
1
|
Engine speed
|
± 2% of reading or ± 1% of engine's max. value whichever is larger
|
2
|
Torque
|
± 2% of reading or ± 1% of engine's max. value whichever is larger
|
3
|
Fuel consumption
|
± 2% of engine's max. value
|
4
|
Air consumption
|
± 2% of reading or ± 1% of engine's max. value whichever is larger
|
5
|
Exhaust gas flow
|
± 2,5% of reading or ± 1,5% of engine's max. value whichever is larger
|
6
|
Temperatures ≤ 600 K
|
+ 2 K absolute
|
7
|
Temperatures > 600 K
|
± 1% of reading
|
8
|
Exhaust gas pressure
|
± 0,2 kPa absolute
|
9
|
Intake air depression
|
± 0,05 kPa absolute
|
10
|
Atmospheric pressure
|
± 0,1 kPa absolute
|
11
|
Other pressures
|
± 0,1 kPa absolute
|
12
|
Absolute humidity
|
± 5% of reading
|
13
|
Dilution air flow
|
± 2% of reading
|
14
|
Diluted exhaust gas flow
|
± 2% of reading
|
1.4. Determination of the gaseous components
1.4.1. General analyser specifications
The analysers shall have a measuring range appropriate for the accuracy required to measure the concentrations of the exhaust gas components (section 1.4.1.1). It is recommended that the analysers be operated in such a way that the measured concentration falls between 15% and 100% of full scale.
If the full scale value is 155 ppm (or ppm C) or less or if read-out systems (computers, data loggers) that provide sufficient accuracy and resolution below 15% of full scale are used, concentrations below 15% of full scale are also acceptable. In this case, additional calibrations are to be made to ensure the accuracy of the calibration curves - Annex III, Appendix 2, section 1.5.5.2.
The electromagnetic compatibility (EMC) of the equipment shall be on a level as to minimize additional errors.
1.4.1.1. Measurement error
The analyzer shall not deviate from the nominal calibration point by more than ± 2% of the reading or ± 0.3% of full scale, whichever is larger.
NOTE: For the purpose of this standard, accuracy is defined as the deviation of the analyzer reading from the nominal calibration values using a calibration gas (≡ true value)
1.4.1.2. Repeatability
The repeatability, defined as 2,5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, must be no greater than ± 1% of full scale concentration for each range used above 155 ppm (or ppm C) or ± 2% of each range used below 155 ppm (or ppm C).
1.4.1.3. Noise
The analyser peak-to-peak response to zero and calibration or span gases over any 10-second period shall not exceed 2% of full scale on all ranges used.
1.4.1.4. Zero drift
The zero drift during a one-hour period shall be less than 2% of full scale on the lowest range used. The zero response is defined as the mean response, including noise, to a zero gas during a 30-second time interval.
1.4.1.5. Span drift
The span drift during a one-hour period shall be less than 2% of full scale on the lowest range used. Span is defined as the difference between the span response and the zero response. The span response is defined as the mean response, including noise, to a span gas during a 30-second time interval.
1.4.2. Gas drying
The optional gas drying device must have a minimal effect on the concentration of the measured gases. Chemical dryers are not an acceptable method of removing water from the sample.
1.4.3. Analysers
Sections 1.4.3.1 to 1.4.3.5 of this Appendix describe the measurement principles to be used. A detailed description of the measurement systems is given in Annex VI.
The gases to be measured shall be analysed with the following instruments. For non-linear analysers, the use of linearizing circuits is permitted.
1.4.3.1. Carbon monoxide (CO) analysis
The carbon monoxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type.
1.4.3.2. Carbon dioxide (CO2) analysis
The carbon dioxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type.
1.4.3.3. Hydrocarbon (HC) analysis
The hydrocarbon analyser shall be of the heated flame ionization detector (HFID) type with detector, valves, pipework, etc, heated so as to maintain a gas temperature of 463 K (190oC) ± 10 K.
1.4.3.4. Oxides of nitrogen (NOx) analysis
The oxides of nitrogen analyser shall be of the chemiluminescent detector (CLD) or heated chemiluminescent detector (HCLD) type with a NO2/NO converter, if measured on a dry basis. If measured on a wet basis, a HCLD with converter maintained above 328 K (55oC) shall be used, provided the water quench check (Annex III, Appendix 2, section 1.9.2.2) is satisfied.
For both CLD and HCLD, the sampling path shall be maintained at a wall temperature of 328 K to 473 K ( 55oC to 200oC) up to the converter for dry measurement, and up to the analyzer for wet measurement.
1.4.4. Air to fuel measurement
The air to fuel measurement equipment used to determine the exhaust gas flow as specified in section 1.2.5 shall be a wide range air to fuel ratio sensor or lambda sensor of Zirconia type.
The sensor shall be mounted directly on the exhaust pipe where the exhaust gas temperature is high enough to eliminate water condensation.
The accuracy of the sensor with incorporated electronics shall be within:
± 3% of reading
|
λ < 2
|
± 5% of reading
|
2 ≤ λ
|
< 5
|
± 10% of reading
|
5 ≤ λ
|
To fulfil the accuracy specified above, the sensor shall be calibrated as specified by the instrument manufacturer.
1.4.5. Sampling for gaseous emissions
The gaseous emissions sampling probes must be fitted at least 0,5 m or three times the diameter of the exhaust pipe - whichever is the larger - upstream of the exit of the exhaust gas system as far as applicable and sufficiently close to the engine as to ensure an exhaust gas temperature of at least 343 K (70oC) at the probe.
In the case of a multi-cylinder engine with a branched exhaust manifold, the inlet of the probe shall be located sufficiently far downstream so as to ensure that the sample is representative of the average exhaust emissions from all cylinders. In multi-cylinder engines having distinct groups of manifolds, such as in a ‧V‧-engine configuration, it is permissible to acquire a sample from each group individually and calculate an average exhaust emission. Other methods which have been shown to correlate with the above methods may be used. For exhaust emissions calculation the total exhaust mass flow of the engine must be used.
If the composition of the exhaust gas is influenced by any exhaust after-treatment system, the exhaust sample must be taken upstream of this device in the tests of stage I and downstream of this device in the tests of stage II. When a full flow dilution system is used for the determination of the particulates, the gaseous emissions may also be determined in the diluted exhaust gas. The sampling probes shall be close to the particulate sampling probe in the dilution tunnel (Annex VI, section 1.2.1.2, DT and Section 1.2.2, PSP). CO and CO2 may optionally be determined by sampling into a bag and subsequent measurement of the concentration in the sampling bag.
1.5. Determination of the particulates
The determination of the particulates requires a dilution system. Dilution may be accomplished by a partial flow dilution system or a full flow dilution system. The flow capacity of the dilution system shall be large enough to completely eliminate water condensation in the dilution and sampling systems, and maintain the temperature of the diluted exhaust gas between 315 K (42oC) and 325 K (52oC) immediately upstream of the filter holders. De-humidifying the dilution air before entering the dilution system is permitted, if the air humidity is high. Dilution air pre-heating above the temperature limit of 303 K (30 oC) is recommended, if the ambient temperature is below 293 K (20oC). However, the diluted air temperature must not exceed 325 K (52oC) prior to the introduction of the exhaust in the dilution tunnel.
NOTE: For steady-state procedure, the filter temperature may be kept at or below the maximum temperature of 325 K (52oC) instead of respecting the temperature range of 42oC - 52oC.
For a partial flow dilution system, the particulate sampling probe must be fitted close to and upstream of the gaseous probe as defined in Section 4.4 and in accordance with Annex VI, section 1.2.1.1, figure 4-12 EP and SP.
The partial flow dilution system has to be designed to split the exhaust stream into two fractions, the smaller one being diluted with air and subsequently used for particulate measurement. From that it is essential that the dilution ratio be determined very accurately. Different splitting methods can be applied, whereby the type of splitting used dictates to a significant degree the sampling hardware and procedures to be used (Annex VI, section 1.2.1.1).
To determine the mass of the particulates, a particulate sampling system, particulate sampling filters, a microgram balance and a temperature and humidity controlled weighing chamber are required.
For particulate sampling, two methods may be applied:
—
|
the single filter method uses one pair of filters (1.5.1.3. of this Appendix) for all modes of the test cycle. Considerable attention must be paid to sampling times and flows during the sampling phase of the test. However, only one pair of filters will be required for the test cycle,
|
—
|
the multiple filter method dictates that one pair of filters (section 1.5.1.3. of this Appendix) is used for each of the individual modes of the test cycle. This method allows more lenient sample procedures but uses more filters.
|
1.5.1. Particulate sampling filters
1.5.1.1. Filter specification
Fluorocarbon coated glass fibre filters or fluorocarbon based membrane filters are required for certification tests. For special applications different filter materials may be used. All filter types shall have a 0,3 µm DOP (di-octylphthalate) collection efficiency of at least 99% at a gas face velocity between 35 and 100 cm/s. When performing correlation tests between laboratories or between a manufacturer and an approval authority, filters of identical quality must be used.
1.5.1.2. Filter size
Particulate filters must have a minimum diameter of 47 mm (37 mm stain diameter). Larger diameter filters are acceptable (section 1.5.1.5.).
1.5.1.3. Primary and back-up filters
The diluted exhaust shall be sampled by a pair of filters placed in series (one primary and one back-up filter) during the test sequence. The back-up filter shall be located no more than 100 mm downstream of, and shall not be in contact with, the primary filter. The filters may be weighed separately or as a pair with the filters placed stain side to stain side.
1.5.1.4. Filter face velocity
A gas face velocity through the filter of 35 to 100 cm/s shall be achieved. The pressure drop increase between the beginning and the end of the test shall be no more than 25 kPa.
1.5.1.5. Filter loading
The recommended minimum filter loadings for the most common filter sizes are shown in the following table. For larger filter sizes, the minimum filter loading shall be 0,065 mg/1000 mm2 filter area.
Filter Diameter (mm)
|
Recommended stain diameter (mm)
|
Recommended minimum loading (mg)
|
47
|
37
|
0,11
|
70
|
60
|
0,25
|
90
|
80
|
0,41
|
110
|
100
|
0,62
|
For the multiple filter method, the recommended minimum filter loading for the sum of all filters shall be the product of the appropriate value above and the square root of the total number of modes.
1.5.2. Weighing chamber and analytical balance specifications
1.5.2.1. Weighing chamber conditions
The temperature of the chamber (or room) in which the particulate filters are conditioned and weighed shall be maintained to within 295 K (22oC) ± 3K during all filter conditioning and weighing. The humidity shall be maintained to a dew point of 282,5 (9,5oC) ± 3K and a relative humidity of 45 ± 8%.
1.5.2.2. Reference filter weighing
The chamber (or room) environment shall be free of any ambient contaminants (such as dust) that would settle on the particulate filters during their stabilisation. Disturbances to weighing room specifications as outlined in section 1.5.2.1 will be allowed if the duration of the disturbances does not exceed 30 minutes. The weighing room should meet the required specifications prior to personnel entrance into the weighing room. At least two unused reference filters or reference filter pairs shall be weighed within four hours of, but preferably at the same time as the sample filter (pair) weighing. They shall be the same size and material as the sample filters.
If the average weight of the reference filters (reference filter pairs) changes between sample filter weighing by more than 10 μg, then all sample filters shall be discarded and the emissions test repeated.
If the weighing room stability criteria outlined in section 1.5.2.1 is not met, but the reference filter (pair) weighing meet the above criteria, the engine manufacturer has the option of accepting the sample filter weights or voiding the tests, fixing the weighing room control system and re-running the test.
1.5.2.3. Analytical balance
The analytical balance used to determine the weights of all filters shall have a precision (standard deviation) of 2 (μg and a resolution of 1 μg (1 digit = 1 μg) specified by the balance manufacturer.
1.5.2.4. Elimination of static electricity effects
To eliminate the effects of static electricity, the filters shall be neutralized prior to weighing, for example, by a Polonium neutralizer or a device of similar effect.
1.5.3. Additional specifications for particulate measurement
All parts of the dilution system and the sampling system from the exhaust pipe up to the filter holder, which are in contact with raw and diluted exhaust gas, must be designed to minimize deposition or alteration of the particulates. All parts must be made of electrically conductive materials that do not react with exhaust gas components, and must be electrically grounded to prevent electrostatic effects.
2. MEASUREMENT AND SAMPLING PROCEDURES (NRTC TEST)
2.1. Introduction
Gaseous and particulate components emitted by the engine submitted for testing shall be measured by the methods of Annex VI. The methods of Annex VI describe the recommended analytical systems for the gaseous emissions (Section 1.1) and the recommended particulate dilution and sampling systems (Section 1.2).
2.2. Dynamometer and test cell equipment
The following equipment shall be used for emission tests of engines on engine dynamometers:
2.2.1. Engine Dynamometer
An engine dynamometer shall be used with adequate characteristics to perform the test cycle described in Appendix 4 to this Annex. The instrumentation for torque and speed measurement shall allow the measurement of the power within the given limits. Additional calculations may be necessary. The accuracy of the measuring equipment must be such that the maximum tolerances of the figures given in Table 3 are not exceeded.
2.2.2. Other Instruments
Measuring instruments for fuel consumption, air consumption, temperature of coolant and lubricant, exhaust gas pressure and intake manifold depression, exhaust gas temperature, air intake temperature, atmospheric pressure, humidity and fuel temperature shall be used, as required. These instruments shall satisfy the requirements given in Table 3:
Table 3. Accuracy of Measuring Instruments
No.
|
Measuring Instrument
|
Accuracy
|
1
|
Engine speed
|
± 2% of reading or ± 1% of engine's max. value, whichever is larger
|
2
|
Torque
|
± 2% of reading or ± 1% of engine's max. value, whichever is larger
|
3
|
Fuel consumption
|
± 2% of engine's max. value
|
4
|
Air consumption
|
± 2% of reading or ± 1% of engine's max. value, whichever is larger
|
5
|
Exhaust gas flow
|
± 2,5% of reading or ± 1,5% of engine's max. value, whichever is larger
|
6
|
Temperatures ≤ 600 K
|
+ 2K absolute
|
7
|
Temperatures > 600 K
|
± 1% of reading
|
8
|
Exhaust gas pressure
|
± 0,2 kPa absolute
|
9
|
Intake air depression
|
± 0,05 kPa absolute
|
10
|
Atmospheric pressure
|
± 0,1 kPa absolute
|
11
|
Other pressures
|
± 0,1 kPa absolute
|
12
|
Absolute humidity
|
± 5% of reading
|
13
|
Dilution air flow
|
± 2% of reading
|
14
|
Diluted exhaust gas flow
|
± 2% of reading
|
2.2.3. Raw Exhaust Gas Flow
For calculating the emissions in the raw exhaust gas and for controlling a partial flow dilution system, it is necessary to know the exhaust gas mass flow rate. For determinating the exhaust mass flow rate, either of the methods described below may be used.
For the purpose of emissions calculation, the response time of either method described below shall be equal to or less than the requirement for the analyzer response time, as defined in Appendix 2, Section 1.11.1.
For the purpose of controlling a partial flow dilution system, a faster response is required. For partial flow dilution systems with online control, a response time of ≤ 0,3 s is required. For partial flow dilution systems with look ahead control based on a pre-recorded test run, a response time of the exhaust flow measurement system of ≤ 5 s with a rise time of ≤ 1 s is required. The system response time shall be specified by the instrument manufacturer. The combined response time requirements for exhaust gas flow and partial flow dilution system are indicated in Section 2.4.
Direct measurement method
Direct measurement of the instantaneous exhaust flow may be done by systems, such as:
—
|
pressure differential devices, like flow nozzle, (for details see ISO 5167: 2000)
|
Precautions shall be taken to avoid measurement errors, which will impact emission value errors. Such precautions include the careful installation of the device in the engine exhaust system according to the instrument manufacturers' recommendations and to good engineering practice. Especially, engine performance and emissions must not be affected by the installation of the device.
The flowmeters shall meet the accuracy specifications of Table 3.
Air and fuel measurement method
This involves measurement of the airflow and the fuel flow with suitable flowmeters. The calculation of the instantaneous exhaust gas flow is as follows:
G
EXHW
= G
AIRW
+ G
FUEL
(for wet exhaust mass)
The flowmeters shall meet the accuracy specifications of Table 3, but shall also be accurate enough to also meet the accuracy specifications for the exhaust gas flow.
Tracer measurement method
This involves measurement of the concentration of a tracer gas in the exhaust.
A known amount of an inert gas (e.g. pure helium) shall be injected into the exhaust gas flow as a tracer. The gas is mixed and diluted by the exhaust gas, but must not react in the exhaust pipe. The concentration of the gas shall then be measured in the exhaust gas sample.
In order to ensure complete mixing of the tracer gas, the exhaust gas sampling probe shall be located at least 1 m or 30 times the diameter of the exhaust pipe, whichever is larger, downstream of the tracer gas injection point. The sampling probe may be located closer to the injection point if complete mixing is verified by comparing the tracer gas concentration with the reference concentration when the tracer gas is injected upstream of the engine.
The tracer gas flow rate shall be set so that the tracer gas concentration at engine idle speed after mixing becomes lower than the full scale of the trace gas analyzer.
The calculation of the exhaust gas flow is as follows:
where
G
EXHW
= instantaneous exhaust mass flow (kg/s)
G
T
= tracer gas flow (cm3/min)
conc
mix
= instantaneous concentration of the tracer gas after mixing (ppm)
ρ
EXH
= density of the exhaust gas (kg/m3)
conc
a
= background concentration of the tracer gas in the intake air (ppm)
The background concentration of the tracer gas (conc
a) may be determined by averaging the background concentration measured immediately before the test run and after the test run.
When the background concentration is less than 1% of the concentration of the tracer gas after mixing (conc
mix.) at maximum exhaust flow, the background concentration may be neglected.
The total system shall meet the accuracy specifications for the exhaust gas flow, and shall be calibrated according to Appendix 2, paragraph 1.11.2
Air flow and air to fuel ratio measurement method
This involves exhaust mass calculation from the airflow and the air to fuel ratio. The calculation of the instantaneous exhaust gas mass flow is as follows:
with A / F
st = 14,5
where
A/Fst= stoichiometric air/fuel ratio (kg/kg)
λ= relative air /fuel ratio
concCO2
= dry CO2 concentration (%)
concCO
= dry CO concentration (ppm)
concHC
= HC concentration (ppm)
NOTE: The calculation refers to a diesel fuel with a H/C ratio equal to 1.8.
The air flowmeter shall meet the accuracy specifications in Table 3, the CO2 analyzer used shall meet the specifications of section 2.3.1, and the total system shall meet the accuracy specifications for the exhaust gas flow.
Optionally, air to fuel ratio measurement equipment, such as a zirconia type sensor, may be used for the measurement of the excess air ratio in accordance with the specifications of section 2.3.4.
2.2.4. Diluted Exhaust Gas Flow
For calculation of the emissions in the diluted exhaust gas, it is necessary to know the diluted exhaust gas mass flow rate. The total diluted exhaust gas flow over the cycle (kg/test) shall be calculated from the measurement values over the cycle and the corresponding calibration data of the flow measurement device (V
0 for PDP, K
V for CFV, C
d for SSV): the corresponding methods described in Appendix 3, section 2.2.1 shall be used. If the total sample mass of particulates and gaseous pollutants exceeds 0,5% of the total CVS flow, the CVS flow shall be corrected or the particulate sample flow shall be returned to the CVS prior to the flow measuring device.
2.3. Determination of the gaseous components
2.3.1. General Analyser Specifications
The analysers shall have a measuring range appropriate for the accuracy required to measure the concentrations of the exhaust gas components (section 1.4.1.1). It is recommended that the analysers be operated in such a way that the measured concentration falls between 15% and 100% of full scale.
If the full scale value is 155 ppm (or ppm C) or less, or if read-out systems (computers, data loggers) that provide sufficient accuracy and resolution below 15% of full scale are used, concentrations below 15% of full scale are also acceptable. In this case, additional calibrations are to be made to ensure the accuracy of the calibration curves - Annex III, Appendix 2, section 1.5.5.2.
The electromagnetic compatibility (EMC) of the equipment shall be of a level such as to minimize additional errors.
2.3.1.1. Measurement error
The analyzer shall not deviate from the nominal calibration point by more than ± 2% of the reading or ± 0,3% of full scale, whichever is larger.
NOTE: For the purpose of this standard, accuracy is defined as the deviation of the analyzer reading from the nominal calibration values using a calibration gas (≡ true value).
2.3.1.2. Repeatability
The repeatability, defined as 2,5 times the standard deviation of 10 repetitive responses to a given calibration or span gas, must be no greater than ± 1% of full scale concentration for each range used above 155 ppm (or ppm C) or ± 2% for each range used below 155 ppm (or ppm C).
2.3.1.3. Noise
The analyser peak-to-peak response to zero and calibration or span gases over any 10-second period shall not exceed 2% of full scale on all ranges used.
2.3.1.4. Zero drift
The zero drift during a one-hour period shall be less than 2% of full scale on the lowest range used. The zero response is defined as the mean response, including noise, to a zero gas during a 30-second time interval.
2.3.1.5. Span drift
The span drift during a one-hour period shall be less than 2% of full scale on the lowest range used. Span is defined as the difference between the span response and the zero response. The span response is defined as the mean response, including noise, to a span gas during a 30-second time interval.
2.3.1.6. Rise Time
For raw exhaust gas analysis, the rise time of the analyzer installed in the measurement system shall not exceed 2,5 s.
NOTE: Only evaluating the response time of the analyzer alone will not clearly define the suitability of the total system for transient testing. Volumes, and especially dead volumes, through out the system will not only affect the transportation time from the probe to the analyzer, but also affect the rise time. Also transport times inside of an analyzer would be defined as analyzer response time, like the converter or water traps inside of a NOx analyzers. The determination of the total system response time is described in Appendix 2, Section 1.11.1.
2.3.2. Gas Drying
Same specifications as for NRSC test cycle apply (Section 1.4.2) as described here below.
The optional gas drying device must have a minimal effect on the concentration of the measured gases. Chemical dryers are not an acceptable method of removing water from the sample.
2.3.3. Analysers
Same specifications as for NRSC test cycle apply (Section 1.4.3) as described here below.
The gases to be measured shall be analysed with the following instruments. For non-linear analysers, the use of linearizing circuits is permitted.
2.3.3.1. Carbon monoxide (CO) analysis
The carbon monoxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type.
2.3.3.2. Carbon dioxide (CO2) analysis
The carbon dioxide analyser shall be of the non-dispersive infra-red (NDIR) absorption type.
2.3.3.3. Hydrocarbon (HC) analysis
The hydrocarbon analyser shall be of the heated flame ionization detector (HFID) type with detector, valves, pipework, etc, heated so as to maintain a gas temperature of 463 K (190oC) ± 10 K.
2.3.3.4. Oxides of nitrogen (NOx) analysis
The oxides of nitrogen analyser shall be of the chemiluminescent detector (CLD) or heated chemiluminescent detector (HCLD) type with a NO2/NO converter, if measured on a dry basis. If measured on a wet basis, a HCLD with converter maintained above 328 K (55oC shall be used, provided the water quench check (Annex III, Appendix 2, section 1.9.2.2) is satisfied.
For both CLD and HCLD, the sampling path shall be maintained at a wall temperature of 328 K to 473 K ( 55oC to 200oC) up to the converter for dry measurement, and up to the analyzer for wet measurement.
2.3.4. Air to fuel measurement
The air to fuel measurement equipment used to determine the exhaust gas flow as specified in section 2.2.3 shall be a wide range air to fuel ratio sensor or lambda sensor of Zirconia type.
The sensor shall be mounted directly on the exhaust pipe where the exhaust gas temperature is high enough to eliminate water condensation.
The accuracy of the sensor with incorporated electronics shall be within:
± 3 % of reading
|
λ < 2
|
± 5 % of reading
|
2 ≤
|
λ < 5
|
± 10% of reading
|
5 ≤ λ
|
To fulfil the accuracy specified above, the sensor shall be calibrated as specified by the instrument manufacturer.
2.3.5. Sampling of Gaseous Emissions
2.3.5.1. Raw exhaust gas flow
For calculation of the emissions in the raw exhaust gas the same specifications as for NRSC test cycle apply (Section 1.4.4), as described here below.
The gaseous emissions sampling probes must be fitted at least 0,5 m or three times the diameter of the exhaust pipe -whichever is the larger - upstream of the exit of the exhaust gas system as far as applicable and sufficiently close to the engine as to ensure an exhaust gas temperature of at least 343 K (70oC) at the probe.
In the case of a multicylinder engine with a branched exhaust manifold, the inlet of the probe shall be located sufficiently far downstream so as to ensure that the sample is representative of the average exhaust emissions from all cylinders. In multicylinder engines having distinct groups of manifolds, such as in a ‧V‧-engine configuration, it is permissible to acquire a sample from each group individually and calculate an average exhaust emission. Other methods which have been shown to correlate with the above methods may be used. For exhaust emissions calculation the total exhaust mass flow of the engine must be used.
If the composition of the exhaust gas is influenced by any exhaust after-treatment system, the exhaust sample must be taken upstream of this device in the tests of stage I and downstream of this device in the tests of stage II.
2.3.5.2. Diluted exhaust gas flow
If a full flow dilution system is used, the following specifications apply.
The exhaust pipe between the engine and the full flow dilution system shall conform to the requirements of Annex VI.
The gaseous emissions sample probe(s) shall be installed in the dilution tunnel at a point where the dilution air and exhaust gas are well mixed, and in close proximity to the particulates sampling probe.
Sampling can generally be done in two ways:
—
|
the pollutants are sampled into a sampling bag over the cycle and measured after completion of the test;
|
—
|
the pollutants are sampled continuously and integrated over the cycle; this method is mandatory for HC and NOx.
|
The background concentrations shall be sampled upstream of the dilution tunnel into a sampling bag, and shall be subtracted from the emissions concentration according to Appendix 3, Section 2.2.3.
2.4. Determination of the participates
Determination of the particulates requires a dilution system. Dilution may be accomplished by a partial flow dilution system or a full flow dilution system. The flow capacity of the dilution system shall be large enough to completely eliminate water condensation in the dilution and sampling systems, and maintain the temperature of the diluted exhaust gas between 315 K (42oC) and 325 K (52oC) immediately upstream of the filter holders. De-humidifying the dilution air before entering the dilution system is permitted, if the air humidity is high. Dilution air pre-heating above the temperature limit of 303 K (30 oC) is recommended if the ambient temperature is below 293 K (20 C). However, the diluted air temperature must not exceed 325 K (52oC) prior to the introduction of the exhaust in the dilution tunnel.
The particulate sampling probe shall be installed in close proximity to the gaseous emissions sampling probe, and the installation shall comply with the provisions of Section 2.3.5.
To determine the mass of the particulates, a particulate sampling system, particulate sampling filters, microgram balance, and a temperature and humidity controlled weighing chamber, are required.
Partial flow dilution system specifications
The partial flow dilution system has to be designed to split the exhaust stream into two fractions, the smaller one being diluted with air and subsequently used for particulate measurement. For this it is essential that the dilution ratio be determined very accurately. Different splitting methods can be applied, whereby the type of splitting used dictates to a significant degree the sampling hardware and procedures to be used (Annex VI, section 1.2.1.1).
For the control of a partial flow dilution system, a fast system response is required. The transformation time for the system shall be determined by the procedure described in Appendix 2, Section 1.11.1.
If the combined transformation time of the exhaust flow measurement (see previous Section) and the partial flow system is less than 0,3 s, online control may be used. If the transformation time exceeds 0,3 s, look ahead control based on a pre-recorded test run must be used. In this case, the rise time shall be ≤ 1 s and the delay time of the combination ≤ 10 s.
The total system response shall be designed as to ensure a representative sample of the particulates, G
SE
, proportional to the exhaust mass flow. To determine the proportionality, a regression analysis of G
SE
versus G
EXHW
shall be conducted on a minimum 5 Hz data acquisition rate, and the following criteria shall be met:
—
|
The correlation coefficient r2 of the linear regression between GSE and GEXHW shall be not less than 0,95.
|
—
|
The standard error of estimate of GSE on GEXHW shall not exceed 5% of GSE maximum.
|
—
|
GSE intercept of the regression line shall not exceed ± 2% of GSE maximum.
|
Optionally, a pre-test may be run, and the exhaust mass flow signal of the pre-test be used for controlling the sample flow into the particulate system ("look-ahead control"). Such a procedure is required if the transformation time of the particulate system, t
50,P or/and the transformation time of the exhaust mass flow signal, t
50,F are > 0,3 s. A correct control of the partial dilution system is obtained, if the time trace of G
EXHW,pre of the pre-test, which controls G
SE
, is shifted by a "look-ahead" time of t
50,P + t
50,F.
For establishing the correlation between G
SE
and G
EXHW
the data taken during the actual test shall be used, with G
EXHW
time aligned by t50,F relative to G
SE
(no contribution from t
50,P to the time alignment). That is, the time shift between G
EXHW
and G
SE
is the difference in their transformation times that were determined in Appendix 2, Section 2.6.
For partial flow dilution systems, the accuracy of the sample flow G
SE
is of special concern, if not measured directly, but determined by differential flow measurement:
G
SE
= G
TOTW
- G
DILW
In this case an accuracy of ± 2% for G
TOTW
and G
DILW
is not sufficient to guarantee acceptable accuracies of G
SE
. If the gas flow is determined by differential flow measurement, the maximum error of the difference shall be such that the accuracy of G
SE
is within ± 5% when the dilution ratio is less than 15. It can be calculated by taking root-mean-square of the errors of each instrument.
Acceptable accuracies of G
SE
can be obtained by either of the following methods:
(a)
|
The absolute accuracies of GTOTW and GDILW are ± 0,2% which guarantees an accuracy of GSE of ≤ 5% at a dilution ratio of 15. However, greater errors will occur at higher dilution ratios.
|
(b)
|
Calibration of GDILW relative to GTOTW is carried out such that the same accuracies for GSE as in (a) are obtained. For the details of such a calibration see Appendix 2, Section 2.6.
|
(c)
|
The accuracy of GSE is determined indirectly from the accuracy of the dilution ratio as determined by a tracer gas, e.g. CO2. Again, accuracies equivalent to method (a) for GSE are required.
|
(d)
|
The absolute accuracy of GTOTW and GDILW is within ± 2% of full scale, the maximum error of the difference between GTOTW and GDILW is within 0,2%, and the linearity error is within ± 0.2% of the highest GTOTW observed during the test.
|
2.4.1. Particulate Sampling Filters
2.4.1.1. Filter specification
Fluorocarbon coated glass fibre filters or fluorocarbon based membrane filters are required for certification tests. For special applications different filter materials may be used. All filter types shall have a 0,3 µm DOP (di-octylphthalate) collection efficiency of at least 99% at a gas face velocity between 35 and 100 cm/s. When performing correlation tests between laboratories or between a manufacturer and an approval authority, filters of identical quality must be used.
2.4.1.2. Filter size
Particulate filters must have a minimum diameter of 47 mm (37 mm stain diameter). Larger diameter filters are acceptable (section 2.4.1.5.).
2.4.1.3. Primary and back-up filters
The diluted exhaust shall be sampled by a pair of filters placed in series (one primary and one back-up filter) during the test sequence. The back-up filter shall be located no more than 100 mm downstream of, and shall not be in contact with, the primary filter. The filters may be weighed separately or as a pair with the filters placed stain side to stain side.
2.4.1.4. Filter face velocity
A gas face velocity through the filter of 35 to 100 cm/s shall be achieved. The pressure drop increase between the beginning and the end of the test shall be no more than 25 kPa.
2.4.1.5. Filter loading
The recommended minimum filter loadings for the most common filter sizes are shown in the following table. For larger filter sizes, the minimum filter loading shall be 0,065 mg/1000 mm2 filter area.
Filter Diameter (mm)
|
Recommended stain diameter (mm)
|
Recommended minimum loading (mg)
|
47
|
37
|
0,11
|
70
|
60
|
0,25
|
90
|
80
|
0,41
|
110
|
100
|
0,62
|
2.4.2. Weighing Chamber and Analytical Balance Specifications
2.4.2.1. Weighing chamber conditions
The temperature of the chamber (or room) in which the particulate filters are conditioned and weighed shall be maintained to within 295 K (22oC) ±3K during all filter conditioning and weighing. The humidity shall be maintained to a dewpoint of 282,5 (9,5oC) ± 3 K and a relative humidity of 45 ± 8%.
2.4.2.2. Reference filter weighing
The chamber (or room) environment shall be free of any ambient contaminants (such as dust) that would settle on the particulate filters during their stabilisation. Disturbances to weighing room specifications as outlined in section 2.4.2.1 will be allowed if the duration of the disturbances does not exceed 30 minutes. The weighing room should meet the required specifications prior to personnel entrance into the weighing room. At least two unused reference filters or reference filter pairs shall be weighed within four hours of, but preferably at the same time as the sample filter (pair) weighing. They shall be the same size and material as the sample filters.
If the average weight of the reference filters (reference filter pairs) changes between sample filter weighing by more than 10µg, then all sample filters shall be discarded and the emissions test repeated.
If the weighing room stability criteria outlined in section 2.4.2.1 are not met, but the reference filter (pair) weighing meet the above criteria, the engine manufacturer has the option of accepting the sample filter weights or voiding the tests, fixing the weighing room control system and re-running the test.
2.4.2.3. Analytical balance
The analytical balance used to determine the weights of all filters shall have a precision (standard deviation) of 2 (µg and a resolution of 1 µg (1 digit = 1 µg) specified by the balance manufacturer.
2.4.2.4. Elimination of static electricity effects
To eliminate the effects of static electricity, the filters shall be neutralized prior to weighing, for example, by a Polonium neutralizer or a device having similar effect.
2.4.3. Additional Specifications for Particulate Measurement
All parts of the dilution system and the sampling system from the exhaust pipe up to the filter holder, which are in contact with raw and diluted exhaust gas, must be designed to minimize deposition or alteration of the particulates. All parts must be made of electrically conductive materials that do not react with exhaust gas components, and must be electrically grounded to prevent electrostatic effects.”