Commission Delegated Regulation (EU) 2017/654 of 19 December 2016 supplementing Regulation (EU) 2016/1628 of the European Parliament and of the Council with regard to technical and general requirements relating to emission limits and type-approval for internal combustion engines for non-road mobile machinery

• m cor is the PM sample filter mass corrected for buoyancy

• m uncor is the PM sample filter mass uncorrected for buoyancy

• ρ air is the density of air in balance environment

• ρ weight is the density of calibration weight used to span balance

• ρ media is the density of PM sample filter

with

Image omitted; see official source	(6-28)

Where:

• p abs is the absolute pressure in balance environment

- M

mix is the molar mass of air in balance environment

- R is the molar gas constant.

• T amb is the absolute ambient temperature of balance environment

8.2.   Instrument validation for test

8.2.1.   Validation of proportional flow control for batch sampling and minimum dilution ratio for PM batch sampling

8.2.1.1.   Proportionality criteria for CVS

8.2.1.1.1.   Proportional flows

For any pair of flow meters, the recorded sample and total flow rates or their 1 Hz means shall be used with the statistical calculations in Appendix 3 of Annex VII. The standard error of the estimate, SEE, of the sample flow rate versus the total flow rate shall be determined. For each test interval, it shall be demonstrated that SEE was less than or equal to 3,5 % of the mean sample flow rate.

8.2.1.1.2.   Constant flows

For any pair of flow meters, the recorded sample and total flow rates or their 1 Hz means shall be used to demonstrate that each flow rate was constant within ± 2,5 % of its respective mean or target flow rate. The following options may be used instead of recording the respective flow rate of each type of meter:

• (a) Critical-flow venturi option. For critical-flow venturis, the recorded venturi-inlet conditions or their 1 Hz means shall be used. It shall be demonstrated that the flow density at the venturi inlet was constant within ± 2,5 % of the mean or target density over each test interval. For a CVS critical-flow venturi, this may be demonstrated by showing that the absolute temperature at the venturi inlet was constant within ± 4 % of the mean or target absolute temperature over each test interval;

• (b) Positive-displacement pump option. The recorded pump-inlet conditions or their 1 Hz means shall be used. It shall be demonstrated that the flow density at the pump inlet was constant within ± 2,5 % of the mean or target density over each test interval. For a CVS pump, this may be demonstrated by showing that the absolute temperature at the pump inlet was constant within ± 2 % of the mean or target absolute temperature over each test interval.

8.2.1.1.3.   Demonstration of proportional sampling

For any proportional batch sample such as a bag or PM filter, it shall be demonstrated that proportional sampling was maintained using one of the following, noting that up to 5 % of the total number of data points may be omitted as outliers.

Using good engineering judgment, it shall be demonstrated with an engineering analysis that the proportional-flow control system inherently ensures proportional sampling under all circumstances expected during testing. For example, CFVs may be used for both sample flow and total flow if it is demonstrated that they always have the same inlet pressures and temperatures and that they always operate under critical-flow conditions.

Measured or calculated flows and/or tracer gas concentrations (e.g. CO2) shall be used to determine the minimum dilution ratio for PM batch sampling over the test interval.

8.2.1.2.   Partial flow dilution system validation

For the control of a partial flow dilution system to extract a proportional raw exhaust gas sample, a fast system response is required; this is identified by the promptness of the partial flow dilution system. The transformation time for the system shall be determined in accordance with the procedure set out in point 8.1.8.6.3.2. The actual control of the partial flow dilution system shall be based on the current measured conditions. If the combined transformation time of the exhaust gas flow measurement and the partial flow system is ≤ 0,3 s, online control shall be used. If the transformation time exceeds 0,3 s, look-ahead control based on a pre-recorded test run shall be used. In this case, the combined rise time shall be ≤ 1 s and the combined delay time ≤ 10 s. The total system response shall be designed as to ensure a representative sample of the particulates, qm p,i (sample flow of exhaust gas into partial flow dilution system), proportional to the exhaust gas mass flow. To determine the proportionality, a regression analysis of qm p,i versus qm ew,i (exhaust gas mass flow rate on wet basis) shall be conducted on a minimum 5 Hz data acquisition rate, and the following criteria shall be met:

• (a) The correlation coefficient r ² of the linear regression between qm p,i and qm ew,i shall not be less than 0,95;

• (b) The standard error of estimate of qm p,i on qm ew,i shall not exceed 5 % of qm p maximum;

- (c) qm

p intercept of the regression line shall not exceed ± 2 % of qm p maximum.

Look-ahead control is required if the combined transformation times of the particulate system, t 50,P and of the exhaust gas mass flow signal, t 50,F are > 0,3 s. In this case, a pre-test shall be run and the exhaust gas mass flow signal of the pre-test be used for controlling the sample flow into the particulate system. A correct control of the partial dilution system is obtained, if the time trace of qm ew,pre of the pre-test, which controls qm p, is shifted by a ‘look-ahead’ time of t 50,P + t 50,F.

For establishing the correlation between qm p,i and qm ew,i the data taken during the actual test shall be used, with qm ew,i time aligned by t 50,F relative to qm p,i (no contribution from t 50,P to the time alignment). The time shift between qm ew and qm p is the difference between their transformation times that were determined in point 8.1.8.6.3.2.

8.2.2.   Gas analyzer range validation, drift validation and drift correction

8.2.2.1.   Range validation

If an analyzer operated above 100 % of its range at any time during the test, the following steps shall be performed:

8.2.2.1.1.   Batch sampling

For batch sampling, the sample shall be re-analyzed using the lowest analyzer range that results in a maximum instrument response below 100 %. The result shall be reported from the lowest range from which the analyzer operates below 100 % of its range for the entire test.

8.2.2.1.2.   Continuous sampling

For continuous sampling, the entire test shall be repeated using the next higher analyzer range. If the analyzer again operates above 100 % of its range, the test shall be repeated using the next higher range. The test shall be continued to be repeated until the analyzer always operates at less than 100 % of its range for the entire test.

8.2.2.2.   Drift validation and drift correction

If the drift is within ±1 %, the data can be either accepted without any correction or accepted after correction. If the drift is greater than ± 1 %, two sets of brake specific emission results shall be calculated for each pollutant with a brake-specific limit value and for CO2, or the test shall be voided. One set shall be calculated using data before drift correction and another set of data calculated after correcting all the data for drift in accordance with point 2.6 of Annex VII and Appendix 1 of Annex VII. The comparison shall be made as a percentage of the uncorrected results. The difference between the uncorrected and the corrected brake-specific emission values shall be within ± 4 % of either the uncorrected brake-specific emission values or the emission limit value, whichever is greater. If not, the entire test is void.

8.2.3.   PM sampling media (e.g. filters) preconditioning and tare weighing

Before an emission test, the following steps shall be taken to prepare PM sample filter media and equipment for PM measurements:

8.2.3.1.   Periodic verifications

It shall be made sure that the balance and PM-stabilization environments meet the periodic verifications in point 8.1.12. The reference filter shall be weighed just before weighing test filters to establish an appropriate reference point (see section details of the procedure in point 8.1.12.1). The verification of the stability of the reference filters shall occur after the post-test stabilisation period, immediately before the post-test weighing.

8.2.3.2.   Visual Inspection

The unused sample filter media shall be visually inspected for defects, defective filters shall be discarded.

8.2.3.3.   Grounding

Electrically grounded tweezers or a grounding strap shall be used to handle PM filters as described in point 9.3.4.

8.2.3.4.   Unused sample media

Unused sample media shall be placed in one or more containers that are open to the PM-stabilization environment. If filters are used, they may be placed in the bottom half of a filter cassette.

8.2.3.5.   Stabilization

Sample media shall be stabilized in the PM-stabilization environment. An unused sample medium can be considered stabilized as long as it has been in the PM-stabilization environment for a minimum of 30 min, during which the PM-stabilization environment has been within the specifications of point 9.3.4.  However, if a PM mass of 400 μg or more is expected, then the sample media shall be stabilised for at least 60 min.

8.2.3.6.   Weighing

The sample media shall be weighed automatically or manually, as follows:

• (a) For automatic weighing, the automation system manufacturer's instructions shall be followed to prepare samples for weighing; this may include placing the samples in a special container;

• (b) For manual weighing, good engineering judgment shall be used;

• (c) Optionally, substitution weighing is permitted (see point 8.2.3.10);

• (d) Once a filter is weighed it shall be returned to the Petri dish and covered.

8.2.3.7.   Buoyancy correction

The measured weight shall be corrected for buoyancy as described in point 8.1.13.2.

8.2.3.8.   Repetition

The filter mass measurements may be repeated to determine the average mass of the filter using good engineering judgement and to exclude outliers from the calculation of the average.

8.2.3.9.   Tare-weighing

Unused filters that have been tare-weighed shall be loaded into clean filter cassettes and the loaded cassettes shall be placed in a covered or sealed container before they are taken to the test cell for sampling.

8.2.3.10.   Substitution weighing

Substitution weighing is an option and, if used, involves measurement of a reference weight before and after each weighing of a PM sampling medium (e.g. filter). While substitution weighing requires more measurements, it corrects for a balance's zero-drift and it relies on balance linearity only over a small range. This is most appropriate when quantifying total PM masses that are less than 0,1 % of the sample medium's mass. However, it may not be appropriate when total PM masses exceed 1 % of the sample medium's mass. If substitution weighing is used, it shall be used for both pre-test and post-test weighing. The same substitution weight shall be used for both pre-test and post-test weighing. The mass of the substitution weight shall be corrected for buoyancy if the density of the substitution weight is less than 2,0 g/cm³. The following steps are an example of substitution weighing:

• (a) Electrically grounded tweezers or a grounding strap shall be used, as described in point 9.3.4.6;

• (b) A static neutralizer shall be used as described in point 9.3.4.6 to minimize static electric charge on any object before it is placed on the balance pan;

• (c) A substitution weight shall be selected that meets the specifications for calibration weights in point 9.5.2. The substitution weight shall also have the same density as the weight that is used to span the microbalance, and shall be similar in mass to an unused sample medium (e.g. filter). If filters are used, the weight's mass should be about (80 to 100) mg for typical 47 mm diameter filters;

• (d) The stable balance reading shall be recorded and then the calibration weight shall be removed;

• (e) An unused sampling medium (e.g. a new filter) shall be weighed, the stable balance reading recorded and the balance environment's dew point, ambient temperature, and atmospheric pressure recorded;

• (f) The calibration weight shall be reweighed and the stable balance reading recorded;

- (g) The arithmetic mean of the two calibration-weight readings that were recorded immediately before and after weighing the unused sample shall be calculated. That mean value shall be subtracted from the unused sample reading, then the true mass of the calibration weight as stated on the calibration-weight certificate shall be added. This result shall be recorded. This is the unused sample's tare weight without correcting for buoyancy;

• (h) These substitution-weighing steps shall be repeated for the remainder of the unused sample media;

• (i) The instructions given in points 8.2.3.7 to 8.2.3.9 shall be followed once weighing is completed.

8.2.4.   Post-test PM sample conditioning and weighing

Used PM sample filters shall be placed into covered or sealed containers or the filter holders shall be closed, in order to protect the sample filters against ambient contamination. Thus protected, the loaded filters have to be returned to the PM-filter conditioning chamber or room. Then the PM sample filters shall be conditioned and weighted accordingly.

8.2.4.1.   Periodic verification

It shall be assured that the weighing and PM-stabilization environments have met the periodic verifications in point 8.1.13.1. After testing is complete, the filters shall be returned to the weighing and PM-stabilisation environment. The weighing and PM-stabilisation environment shall meet the ambient conditions requirements in point 9.3.4.4, otherwise the test filters shall be left covered until proper conditions have been met.

8.2.4.2.   Removal from sealed containers

In the PM-stabilization environment, the PM samples shall be removed from the sealed containers. Filters may be removed from their cassettes before or after stabilization. When a filter is removed from a cassette, the top half of the cassette shall be separated from the bottom half using a cassette separator designed for this purpose.

8.2.4.3.   Electrical grounding

To handle PM samples, electrically grounded tweezers or a grounding strap shall be used, as described in point 9.3.4.5.

8.2.4.4.   Visual inspection

The collected PM samples and the associated filter media shall be inspected visually. If the conditions of either the filter or the collected PM sample appear to have been compromised, or if the particulate matter contacts any surface other than the filter, the sample may not be used to determine particulate emissions. In the case of contact with another surface; the affected surface shall be cleaned before proceeding.

8.2.4.5.   Stabilisation of PM samples

To stabilise PM samples, they shall be placed in one or more containers that are open to the PM-stabilization environment, which is described in point 9.3.4.3.A PM sample is stabilized as long as it has been in the PM-stabilization environment for one of the following durations, during which the stabilization environment has been within the specifications of point 9.3.4.3:

• (a) If it is expected that a filter's total surface concentration of PM will be greater than 0,353 μg/mm², assuming a 400 μg loading on a 38 mm diameter filter stain area, the filter shall be exposed to the stabilization environment for at least 60 minutes before weighing;

• (b) If it is expected that a filter's total surface concentration of PM will be less than 0,353 μg/mm², the filter shall be exposed to the stabilization environment for at least 30 minutes before weighing;

• (c) If a filter's total surface concentration of PM to be expected during the test is unknown, the filter shall be exposed to the stabilization environment for at least 60 minutes before weighing.

8.2.4.6.   Determination of post-test filter mass

The procedures in point 8.2.3 shall be repeated (points 8.2.3.6 through 8.2.3.9) to determine the post-test filter mass.

8.2.4.7.   Total mass

Each buoyancy-corrected filter tare mass shall be subtracted from its respective buoyancy-corrected post-test filter mass. The result is the total mass, m

total, which shall be used in emission calculations in Annex VII.

9.1.   Engine dynamometer specification

9.1.1.   Shaft work

An engine dynamometer shall be used that has adequate characteristics to perform the applicable duty cycle including the ability to meet appropriate cycle validation criteria. The following dynamometers may be used:

- (a) Eddy-current or water-brake dynamometers;

• (b) Alternating-current or direct-current motoring dynamometers;

• (c) One or more dynamometers.

9.1.2.   Transient (NRTC and LSI-NRTC) test cycles

Load cell or in-line torque meter may be used for torque measurements.

When using a load cell, the torque signal shall be transferred to the engine axis and the inertia of the dynamometer shall be considered. The actual engine torque is the torque read on the load cell plus the moment of inertia of the brake multiplied by the angular acceleration. The control system has to perform such a calculation in real time.

9.1.3.   Engine accessories

The work of engine accessories required to fuel, lubricate, or heat the engine, circulate liquid coolant to the engine, or to operate exhaust after-treatment systems shall be accounted for and they shall be installed in accordance with point 6.3.

9.1.4.   Engine fixture and power transmission shaft system (category NRSh)

Where necessary for the proper testing of an engine of category NRSh, the engine fixture for the test bench and power transmission shaft system for connection to the dynamometer rotating system specified by the manufacturer shall be used.

9.2.   Dilution procedure (if applicable)

9.2.1.   Diluent conditions and background concentrations

Gaseous constituents may be measured raw or dilute whereas PM measurement generally requires dilution. Dilution may be accomplished by a full flow or partial flow dilution system. When dilution is applied then the exhaust gas may be diluted with ambient air, synthetic air, or nitrogen. For gaseous emissions measurement the diluent shall be at least 288 K (15 °C). For PM sampling the temperature of the diluent is specified in points 9.2.2 for CVS and 9.2.3 for PFD with varying dilution ratio. The flow capacity of the dilution system shall be large enough to completely eliminate water condensation in the dilution and sampling systems. De-humidifying the dilution air before entering the dilution system is permitted, if the air humidity is high. The dilution tunnel walls may be heated or insulated as well as the bulk stream tubing downstream of the tunnel to prevent the precipitation of water-containing constituents from a gas phase to a liquid phase (‘aqueous condensation’).

Before a diluent is mixed with exhaust gas, it may be preconditioned by increasing or decreasing its temperature or humidity. Constituents may be removed from the diluent to reduce their background concentrations. The following provisions apply to removing constituents or accounting for background concentrations:

- (a) Constituent concentrations in the diluent may be measured and compensated for background effects on test results. See Annex VII for calculations that compensate for background concentrations;

• (b) The following changes to the requirements of sections 7.2, 9.3 and 9.4 are permitted for measuring background gaseous or particulate pollutants:
• (i) It shall not be required to use proportional sampling;
• (ii) Unheated sampling systems may be used;
• (iii) Continuous sampling may be used irrespective of the use of batch sampling for diluted emissions;
• (iv) Batch sampling may be used irrespective of the use of continuous sampling for diluted emissions.

• (c) To account for background PM the following options are available:
• (i) For removing background PM, the diluent shall be filtered with high-efficiency particulate air (HEPA) filters that have an initial minimum collection efficiency specification of 99,97 % (see Article 1(19) for procedures related to HEPA-filtration efficiencies);
• (ii) For correcting for background PM without HEPA filtration, the background PM shall not contribute more than 50 % of the net PM collected on the sample filter;
• (iii) Background correction of net PM with HEPA filtration is permitted without pressure restriction.

9.2.2.   Full flow system

Full-flow dilution; constant-volume sampling (CVS). The full flow of raw exhaust gas is diluted in a dilution tunnel. Constant flow may be maintained by maintaining the temperature and pressure at the flow meter within the limits. For non-constant flow the flow shall be measured directly to allow for proportional sampling. The system shall be designed as follows (see Figure 6.6):

• (a) A tunnel with inside surfaces of stainless steel shall be used. The entire dilution tunnel shall be electrically grounded. Alternatively non-conductive materials may be used for engine categories neither subject to PM nor PN limits;

• (b) The exhaust gas back-pressure shall not be artificially lowered by the dilution air inlet system. The static pressure at the location where raw exhaust gas is introduced into the tunnel shall be maintained within ± 1,2 kPa of atmospheric pressure;

• (c) To support mixing the raw exhaust gas shall be introduced into the tunnel by directing it downstream along the centreline of the tunnel. A fraction of dilution air maybe introduced radially from the tunnel's inner surface to minimize exhaust gas interaction with the tunnel walls;

• (d) Diluent. For PM sampling the temperature of the diluents (ambient air, synthetic air, or nitrogen as quoted in point 9.2.1) shall be maintained between 293 and 325 K (20 to 52 °C) in close proximity to the entrance into the dilution tunnel;

• (e) The Reynolds number, Re, shall be at least 4 000 for the diluted exhaust gas flow, where Re is based on the inside diameter of the dilution tunnel. Re is defined in Annex VII. Verification of adequate mixing shall be performed while traversing a sampling probe across the tunnel's diameter, vertically and horizontally. If the analyzer response indicates any deviation exceeding ± 2 % of the mean measured concentration, the CVS shall be operated at a higher flow rate or a mixing plate or orifice shall be installed to improve mixing;

• (f) Flow measurement preconditioning. The diluted exhaust gas may be conditioned before measuring its flow rate, as long as this conditioning takes place downstream of heated HC or PM sample probes, as follows:
• (i) Flow straighteners, pulsation dampeners, or both of these may be used;
• (ii) A filter may be used;
• (iii) A heat exchanger may be used to control the temperature upstream of any flow meter but steps shall be taken to prevent aqueous condensation;

• (g) Aqueous condensation. Aqueous condensation is a function of humidity, pressure, temperature, and concentrations of other constituents such as sulphuric acid. These parameters vary as a function of engine intake-air humidity, dilution-air humidity, engine air-to-fuel ratio, and fuel composition — including the amount of hydrogen and sulphur in the fuel. To ensure that a flow is measured that corresponds to a measured concentration, either aqueous condensation shall be prevented between the sample probe location and the flow meter inlet in the dilution tunnel or aqueous condensation shall be allowed to occur and humidity at the flow meter inlet measured. The dilution tunnel walls or bulk stream tubing downstream of the tunnel may be heated or insulated to prevent aqueous condensation. Aqueous condensation shall be prevented throughout the dilution tunnel. Certain exhaust gas components can be diluted or eliminated by the presence of moisture; For PM sampling, the already proportional flow coming from CVS goes through secondary dilution (one or more) to achieve the requested overall dilution ratio as shown in Figure 6.7 and set out in point 9.2.3.2;

• (h) The minimum overall dilution ratio shall be within the range of 5:1 to 7:1 and at least 2:1 for the primary dilution stage based on the maximum engine exhaust gas flow rate during the test cycle or test interval;

• (i) The overall residence time in the system shall be between 0,5 and 5 seconds, as measured from the point of diluent introduction to the filter holder(s);

• (j) The residence time in the secondary dilution system, if present, shall be at least 0,5 seconds, as measured from the point of secondary diluent introduction to the filter holder(s).

To determine the mass of the particulates, a particulate sampling system, a particulate sampling filter, a gravimetric balance, and a temperature and humidity controlled weighing chamber, are required.

Figure 6.6

Examples of full-flow dilution sampling configurations

Image omitted; see official source

9.2.3.   Partial flow dilution (PFD) system

9.2.3.1.   Description of partial flow system

A schematic of a PFD system is shown in Figure 6.7. It is a general schematic showing principles of sample extraction, dilution and PM sampling. It is not meant to indicate that all the components described in the Figure are necessary for other possible sampling systems that satisfy the intent of sample collection. Other configurations which do not match these schematics are allowed under the condition that they serve the same purpose of sample collection, dilution, and PM sampling.  These need to satisfy other criteria such as in points 8.1.8.6 (periodic calibration) and 8.2.1.2 (validation) for varying dilution PFD, and point 8.1.4.5 as well as Table 6.5 (linearity verification) and point 8.1.8.5.7 (verification) for constant dilution PFD.

As shown in Figure 6.7, the raw exhaust gas or the primary diluted flow is transferred from the exhaust pipe EP or from CVS respectively to the dilution tunnel DT through the sampling probe SP and the transfer line TL. The total flow through the tunnel is adjusted with a flow controller and the sampling pump P of the particulate sampling system (PSS). For proportional raw exhaust gas sampling, the dilution air flow is controlled by the flow controller FC1, which may use qm ew (exhaust gas mass flow rate on wet basis) or qm aw (intake air mass flow rate on wet basis) and qm f (fuel mass flow rate) as command signals, for the desired exhaust gas split. The sample flow into the dilution tunnel DT is the difference of the total flow and the dilution air flow. The dilution air flow rate is measured with the flow measurement device FM1, the total flow rate with the flow measurement device of the particulate sampling system. The dilution ratio is calculated from these two flow rates. For sampling with a constant dilution ratio of raw or diluted exhaust gas versus exhaust gas flow (e.g.: secondary dilution for PM sampling), the dilution air flow rate is usually constant and controlled by the flow controller FC1 or dilution air pump.

The dilution air (ambient air, synthetic air, or nitrogen) shall be filtered with a high-efficiency PM air (HEPA) filter.

Figure 6.7

Schematic of partial flow dilution system (total sampling type).

Image omitted; see official source

a	=	engine exhaust gas or primary diluted flow
---	---	---
b	=	optional
---	---	---
c	=	PM sampling

Components of Figure 6.7:

DAF	:	Dilution air filter
---	---	---
DT	:	Dilution tunnel or secondary dilution system
---	---	---
EP	:	Exhaust pipe or primary dilution system
---	---	---
FC1	:	Flow controller
---	---	---
FH	:	Filter holder
---	---	---
FM1	:	Flow measurement device measuring the dilution air flow rate
---	---	---
P	:	Sampling pump
---	---	---
PSS	:	PM sampling system
---	---	---
PTL	:	PM transfer line
---	---	---
SP	:	Raw or diluted exhaust gas sampling probe
---	---	---
TL	:	Transfer line

Mass flow rates applicable only for proportional raw exhaust gas sampling PFD:

• qm ew is the exhaust gas mass gas flow rate on wet basis

• qm aw is the intake air mass flow rate on wet basis

• qm f is the fuel mass flow rate

9.2.3.2.   Dilution

The temperature of the diluents (ambient air, synthetic air, or nitrogen as quoted in point 9.2.1) shall be maintained between 293 and 325 K (20 to 52 °C) in close proximity to the entrance into the dilution tunnel.

De-humidifying the dilution air before entering the dilution system is permitted. The partial flow dilution system has to be designed to extract a proportional raw exhaust gas sample from the engine exhaust gas stream, thus responding to excursions in the exhaust gas stream flow rate, and introduce dilution air to this sample to achieve a temperature at the test filter as prescribed by point 9.3.3.4.3. For this it is essential that the dilution ratio be determined such that the accuracy requirements of point 8.1.8.6.1 are fulfilled.

To ensure that a flow is measured that corresponds to a measured concentration, either aqueous condensation shall be prevented between the sample probe location and the flow meter inlet in the dilution tunnel or aqueous condensation shall be allowed to occur and humidity at the flow meter inlet measured. The PFD system may be heated or insulated to prevent aqueous condensation. Aqueous condensation shall be prevented throughout the dilution tunnel.

The minimum dilution ratio shall be within the range of 5:1 to 7:1 based on the maximum engine exhaust gas flow rate during the test cycle or test interval.

The residence time in the system shall be between 0,5 and 5 s, as measured from the point of diluent introduction to the filter holder(s).

To determine the mass of the particulates, a particulate sampling system, a particulate sampling filter, a gravimetric balance, and a temperature and humidity controlled weighing chamber, are required.

9.2.3.3.   Applicability

PFD may be used to extract a proportional raw exhaust gas sample for any batch or continuous PM and gaseous emission sampling over any transient (NRTC and LSI-NRTC) duty cycle, any discrete-mode NRSC or any RMC duty cycle.

The system may be used also for a previously diluted exhaust gas where, via a constant dilution-ratio, an already proportional flow is diluted (see Figure 6.7). This is the way of performing secondary dilution from a CVS tunnel to achieve the necessary overall dilution ratio for PM sampling.

9.2.3.4.   Calibration

The calibration of the PFD to extract a proportional raw exhaust gas sample is considered in point 8.1.8.6.

9.3.   Sampling procedures

9.3.1.   General sampling requirements

9.3.1.1.   Probe design and construction

A probe is the first fitting in a sampling system. It protrudes into a raw or diluted exhaust gas stream to extract a sample, such that it's inside and outside surfaces are in contact with the exhaust gas. A sample is transported out of a probe into a transfer line.

Sample probes shall be made with inside surfaces of stainless steel or, for raw exhaust gas sampling, with any non-reactive material capable of withstanding raw exhaust gas temperatures. Sample probes shall be located where constituents are mixed to their mean sample concentration and where interference with other probes is minimised. It is recommended that all probes remain free from influences of boundary layers, wakes, and eddies — especially near the outlet of a raw-exhaust meter tailpipe where unintended dilution might occur. Purging or back-flushing of a probe shall not influence another probe during testing. A single probe to extract a sample of more than one constituent may be used as long as the probe meets all the specifications for each constituent.

9.3.1.1.1.   Mixing chamber (category NRSh)

Where permitted by the manufacturer, a mixing chamber may be used when testing engines of category NRSh. The mixing chamber is an optional component of a raw gas sampling system and is located in the exhaust system between the silencer and the sample probe. The shape and dimensions of the mixing chamber and tubing before and after shall be such that it provides a well-mixed, homogenous sample at the sample probe location and so that strong pulsations or resonances of the chamber influencing the emissions results are avoided.

9.3.1.2.   Transfer lines

Transfer lines that transport an extracted sample from a probe to an analyzer, storage medium, or dilution system shall be minimized in length by locating analyzers, storage media, and dilution systems as close to the probes as practical. The number of bends in transfer lines shall be minimized and that the radius of any unavoidable bend shall be maximized.

9.3.1.3.   Sampling methods

For continuous and batch sampling, introduced in point 7.2, the following conditions apply:

- (a) When extracting from a constant flow rate, the sample shall also be carried out at a constant flow rate;

• (b) When extracting from a varying flow rate, the sample flow rate shall be varied in proportion to the varying flow rate;

• (c) Proportional sampling shall be validated as described in point 8.2.1.

9.3.2.   Gas sampling

9.3.2.1.   Sampling probes

Either single-port or multi-port probes are used for sampling gaseous emissions. The probes may be oriented in any direction relative to the raw or diluted exhaust gas flow. For some probes, the sample temperatures shall be controlled, as follows:

• (a) For probes that extract NOx from diluted exhaust gas, the probe's wall temperature shall be controlled to prevent aqueous condensation;

• (b) For probes that extract hydrocarbons from the diluted exhaust gas, a probe wall temperature is recommended to be controlled approximately 191 °C to minimise contamination.

9.3.2.1.1.   Mixing chamber (Category NRSh)

When used in accordance with point 9.3.1.1.1, the internal volume of the mixing chamber shall not be less than ten times the individual cylinder swept volume of the engine under test. The mixing chamber shall be coupled as closely as possible to the engine silencer and shall have a minimum inner surface temperature of 452 K (179 °C). The manufacturer may specify the design of the mixing chamber.

9.3.2.2.   Transfer lines

Transfer lines with inside surfaces of stainless steel, PTFE, Viton^TM, or any other material that has better properties for emission sampling shall be used. A non-reactive material capable of withstanding exhaust gas temperatures shall be used. In-line filters may be used if the filter and its housing meet the same temperature requirements as the transfer lines, as follows:

• (a) For NOx transfer lines upstream of either an NO2-to-NO converter that meets the specifications set out in point 8.1.11.5 or a chiller that meets the specifications set out in point 8.1.11.4 a sample temperature that prevents aqueous condensation shall be maintained;

• (b) For THC transfer lines a wall temperature tolerance throughout the entire line of (464 ± 11) K [(191 ± 11) °C] shall be maintained. If sampled from raw exhaust gas, an unheated, insulated transfer line may be connected directly to a probe. The length and insulation of the transfer line shall be designed to cool the highest expected raw exhaust gas temperature to no lower than 191 °C, as measured at the transfer line outlet. For dilute sampling a transition zone between the probe and transfer line of up to 0,92 m in length is allowed to transition the wall temperature to (464 ± 11) K [(191 ± 11) °C].

9.3.2.3.   Sample-conditioning components

9.3.2.3.1.   Sample dryers

9.3.2.3.1.1.   Requirements

Sample dryers may be used for removing moisture from the sample in order to decrease the effect of water on gaseous emissions measurement. Sample dryers shall meet the requirements set out in point 9.3.2.3.1.1 and in point 9.3.2.3.1.2. The moisture content 0,8 volume % is used in equation (7-13).

For the highest expected water vapour concentration Hm, the water removal technique shall maintain humidity at ≤ 5 g water/kg dry air (or about 0,8 volume % H2O), which is 100 % relative humidity at 277,1 K (3,9 °C) and 101,3 kPa. This humidity specification is equivalent to about 25 % relative humidity at 298 K (25 °C) and 101,3 kPa. This may be demonstrated by either:

• (a) measuring the temperature at the outlet of the sample dryer; or

• (b) measuring humidity at a point just upstream of the CLD; or

• (c) performing the verification procedure in point 8.1.12.

9.3.2.3.1.2.   Type of sample dryers allowed and procedure to estimate moisture content after the dryer

Either type of sample dryer described in this point may be used.

• (a) If an osmotic-membrane dryer upstream of any gaseous analyzer or storage medium is used, it shall meet the temperature specifications set out in point 9.3.2.2. The dew point, T dew, and absolute pressure, p total, downstream of an osmotic-membrane dryer shall be monitored. The amount of water shall be calculated as specified in Annex VII by using continuously recorded values of T dew and p total or their peak values observed during a test or their alarm set points. Lacking a direct measurement, the nominal p total is given by the dryer's lowest absolute pressure expected during testing.

• (b) A thermal chiller upstream of a THC measurement system for compression-ignition engines may not be used. If a thermal chiller upstream of an NO2-to-NO converter or in a sampling system without an NO2-to-NO converter is used, the chiller shall meet the NO2 loss-performance check specified in point 8.1.11.4. The dew point, T dew, and absolute pressure, p total, downstream of a thermal chiller shall be monitored. The amount of water shall be calculated as specified in Annex VII by using continuously recorded values of T dew and p total or their peak values observed during a test or their alarm set points. Lacking a direct measurement, the nominal p total is given by the thermal chiller's lowest absolute pressure expected during testing. If it is valid to assume the degree of saturation in the thermal chiller, T dew based on the known chiller efficiency and continuous monitoring of chiller temperature, T chiller may be calculated. If values of T chiller are not continuously recorded, its peak value observed during a test, or its alarm set point, may be used as a constant value to determine a constant amount of water in accordance with Annex VII. If it is valid to assume that T chiller is equal to T dew, T chiller may be used in lieu of T dew in accordance with Annex VII. If it is valid to assume a constant temperature offset between T chiller and T dew, due to a known and fixed amount of sample reheat between the chiller outlet and the temperature measurement location, this assumed temperature offset value may be factored in into emission calculations. The validity of any assumptions allowed by this point shall be shown by engineering analysis or by data.

9.3.2.3.2.   Sample pumps

Sample pumps upstream of an analyzer or storage medium for any gas shall be used. Sample pumps with inside surfaces of stainless steel, PTFE, or any other material having better properties for emission sampling shall be used. For some sample pumps, temperatures shall be controlled, as follows:

• (a) If a NOx sample pump upstream of either an NO2-to-NO converter that meets the requirements set out in point 8.1.11.5 or a chiller that meets the requirements set out in point 8.1.11.4 is used, it shall be heated to prevent aqueous condensation;

• (b) If a THC sample pump upstream of a THC analyzer or storage medium is used, its inner surfaces shall be heated to a tolerance of 464 ± 11 K (191 ± 11) °C.

9.3.2.3.3.   Ammonia scrubbers

Ammonia scrubbers may be used for any or all gaseous sampling systems to prevent NH3 interference, poisoning of NO2-to-NO converter, and deposits in the sampling system or analysers. Installation of the ammonia scrubber shall follow the manufacturer's recommendations.

9.3.2.4.   Sample storage media

In the case of bag sampling, gas volumes shall be stored in sufficiently clean containers that minimally off-gas or allow permeation of gases. Good engineering judgment shall be used to determine acceptable thresholds of storage media cleanliness and permeation. To clean a container, it may be repeatedly purged and evacuated and may be heated. A flexible container (such as a bag) within a temperature-controlled environment, or a temperature controlled rigid container that is initially evacuated or has a volume that can be displaced, such as a piston and cylinder arrangement, shall be used. Containers meeting the specifications in the following Table 6.6 shall be used.

Table 6.6

Gaseous Batch Sampling Container Materials

CO, CO2, O2, CH4, C2H6, C3H8, NO, NO2 [^E0009]	polyvinyl fluoride (PVF) [^E0010] for example TedlarTM, polyvinylidene fluoride [^E0010] for example KynarTM, polytetrafluoroethylene [^E0011] for example TeflonTM, or stainless steel [^E0011]
HC	polytetrafluoroethylene [^E0012] or stainless steel [^E0012]

As long as aqueous condensation in storage container is prevented.

[^E0010]: (²)

Up to 313 K (40 °C).

Up to 475 K (202 °C).

At 464 ± 11 K (191 ± 11 °C).

9.3.3.   PM sampling

9.3.3.1.   Sampling probes

PM probes with a single opening at the end shall be used. PM probes shall be oriented to face directly upstream.

The PM probe may be shielded with a hat that conforms with the requirements in Figure 6.8. In this case the pre-classifier described in point 9.3.3.3 shall not be used.

Figure 6.8

Scheme of a sampling probe with a hat-shaped pre-classifier

Image omitted; see official source

9.3.3.2.   Transfer lines

Insulated or heated transfer lines or a heated enclosure are recommended to minimize temperature differences between transfer lines and exhaust gas constituents. Transfer lines that are inert with respect to PM and are electrically conductive on the inside surfaces shall be used. It is recommended using PM transfer lines made of stainless steel; any material other than stainless steel will be required to meet the same sampling performance as stainless steel. The inside surface of PM transfer lines shall be electrically grounded.

9.3.3.3.   Pre-classifier

The use of a PM pre-classifier to remove large-diameter particles is permitted that is installed in the dilution system directly before the filter holder. Only one pre-classifier is permitted. If a hat shaped probe is used (see Figure 6.8), the use of a pre-classifier is prohibited.

The PM pre-classifier may be either an inertial impactor or a cyclonic separator. It shall be constructed of stainless steel. The pre-classifier shall be rated to remove at least 50 % of PM at an aerodynamic diameter of 10 μm and no more than 1 % of PM at an aerodynamic diameter of 1 μm over the range of flow rates for which it is used. The pre-classifier outlet shall be configured with a means of bypassing any PM sample filter so that the pre-classifier flow can be stabilized before starting a test. PM sample filter shall be located within 75 cm downstream of the pre-classifier's exit.

9.3.3.4.   Sample filter

The diluted exhaust gas shall be sampled by a filter that meets the requirements set out in points 9.3.3.4.1 to 9.3.3.4.4 during the test sequence.

9.3.3.4.1.   Filter specification

All filter types shall have a collection efficiency of at least 99,7 %. The sample filter manufacturer's measurements reflected in their product ratings may be used to show this requirement. The filter material shall be either:

• (a) Fluorocarbon (PTFE) coated glass fibre; or

• (b) Fluorocarbon (PTFE) membrane.

If the expected net PM mass on the filter exceeds 400 μg, a filter with a minimum initial collection efficiency of 98 % may be used.

9.3.3.4.2.   Filter size

The nominal filter size shall be 46,50 mm ± 0,6 mm diameter (at least 37 mm stain diameter). Larger diameter filters may be used with prior agreement of the approval authority. Proportionality between filter and stain area is recommended.

9.3.3.4.3.   Dilution and temperature control of PM samples

PM samples shall be diluted at least once upstream of transfer lines in case of a CVS system and downstream in case of PFD system (see point 9.3.3.2 relating to transfer lines).  Sample temperature shall be controlled to a 320 ± 5 K (47 ± 5 °C) tolerance, as measured anywhere within 200 mm upstream or 200 mm downstream of the PM filter media. The PM sample is intended to be heated or cooled primarily by dilution conditions as specified in point 9.2.1(a).

9.3.3.4.4.   Filter face velocity

A filter face velocity shall be between 0,90 and 1,00 m/s with less than 5 % of the recorded flow values exceeding this range. If the total PM mass exceeds 400 μg, the filter face velocity may be reduced. The face velocity shall be measured as the volumetric flow rate of the sample at the pressure upstream of the filter and temperature of the filter face, divided by the filter's exposed area. The exhaust system stack or CVS tunnel pressure shall be used for the upstream pressure if the pressure drop through the PM sampler up to the filter is less than 2 kPa.

9.3.3.4.5.   Filter holder

To minimize turbulent deposition and to deposit PM evenly on a filter, a 12,5° (from centre) divergent cone angle to transition from the transfer-line inside diameter to the exposed diameter of the filter face shall be used. Stainless steel for this transition shall be used.

9.3.4.   PM-stabilization and weighing environments for gravimetric analysis

9.3.4.1.   Environment for gravimetric analysis

This section describes the two environments required to stabilize and weigh PM for gravimetric analysis: the PM stabilization environment, where filters are stored before weighing; and the weighing environment, where the balance is located. The two environments may share a common space.

Both the stabilization and the weighing environments shall be kept free of ambient contaminants, such as dust, aerosols, or semi-volatile material that could contaminate PM samples.

9.3.4.2.   Cleanliness

The cleanliness of the PM-stabilization environment using reference filters shall be verified, as described in point 8.1.12.1.4.

9.3.4.3.   Temperature of the chamber

The temperature of the chamber (or room) in which the particulate filters are conditioned and weighed shall be maintained to within 295 ± 1 K (22 °C ± 1 °C) during all filter conditioning and weighing. The humidity shall be maintained to a dew point of 282,5 ± 1 K (9,5 °C ± 1 °C) and a relative humidity of 45 % ± 8 %. If the stabilization and weighing environments are separate, the stabilization environment shall be maintained at a tolerance of 295 ± 3 K (22 °C ± 3 °C).

9.3.4.4.   Verification of ambient conditions

When using measurement instruments that meet the specifications in point 9.4 the following ambient conditions shall be verified:

• (a) Dew point and ambient temperature shall be recorded. These values shall be used to determine if the stabilization and weighing environments have remained within the tolerances specified in point 9.3.4.3 for at least 60 min before weighing filters;

• (b) Atmospheric pressure shall be continuously recorded within the weighing environment. An acceptable alternative is to use a barometer that measures atmospheric pressure outside the weighing environment, as long as it can be ensured that the atmospheric pressure at the balance is always at the balance within ± 100 Pa of the shared atmospheric pressure. A means to record the most recent atmospheric pressure shall be provided when each PM sample is weighed.  This value shall be used to calculate the PM sample filter buoyancy correction in point 8.1.13.2.

9.3.4.5.   Installation of balance

The balance shall be installed as follows:

• (a) Installed on a vibration-isolation platform to isolate it from external noise and vibration;

• (b) Shielded from convective airflow with a static-dissipating draft shield that is electrically grounded.

9.3.4.6.   Static electric charge

Static electric charge shall be minimized in the balance environment, as follows:

• (a) The balance is electrically grounded;

- (b) Stainless steel tweezers shall be used if PM samples shall be handled manually;

- (c) Tweezers shall be grounded with a grounding strap, or a grounding strap shall be provided for the operator such that the grounding strap shares a common ground with the balance;

• (d) A static-electricity neutralizer shall be provided that is electrically grounded in common with the balance to remove static charge from PM samples.

9.4.   Measurement instruments

9.4.1.   Introduction

9.4.1.1.   Scope

This point specifies measurement instruments and associated system requirements related to emission testing. This includes laboratory instruments for measuring engine parameters, ambient conditions, flow-related parameters, and emission concentrations (raw or diluted).

9.4.1.2.   Instrument types

Any instrument mentioned in this Regulation shall be used as described in the Regulation itself (see Table 6.5 for measurement quantities provided by these instruments). Whenever an instrument mentioned in this Regulation is used in a way that is not specified, or another instrument is used in its place, the requirements for equivalency provisions shall apply as specified in point 5.1.1.  Where more than one instrument for a particular measurement is specified, one of them will be identified by the approval authority upon application as the reference for showing that an alternative procedure is equivalent to the specified procedure.

9.4.1.3.   Redundant systems

Data from multiple instruments to calculate test results for a single test may be used for all measurement instruments described in this point, with prior approval of the approval authority. Results from all measurements shall be recorded and the raw data shall be retained. This requirement applies whether or not the measurements are actually used in the calculations.

9.4.2.   Data recording and control

The test system shall be able to update data, record data and control systems related to operator demand, the dynamometer, sampling equipment, and measurement instruments. Data acquisition and control systems shall be used that can record at the specified minimum frequencies, as shown in Table 6.7 (this Table does not apply to discrete-mode NRSC testing).

Table 6.7

Data recording and control minimum frequencies

Applicable Test Protocol Section	Measured Values	Minimum Command and Control Frequency	Minimum Recording Frequency
7.6	Speed and torque during an engine step-map	1 Hz	1 mean value per step
7.6	Speed and torque during an engine sweep-map	5 Hz	1 Hz means
7.8.3	Transient (NRTC and LSI-NRTC) duty cycle reference and feedback speeds and torques	5 Hz	1 Hz means
7.8.2	Discrete-mode NRSC and RMC duty cycle reference and feedback speeds and torques	1 Hz	1 Hz
7.3	Continuous concentrations of raw analyzers	N/A	1 Hz
7.3	Continuous concentrations of dilute analyzers	N/A	1 Hz
7.3	Batch concentrations of raw or dilute analyzers	N/A	1 mean value per test interval
7.6 8.2.1	Diluted exhaust gas flow rate from a CVS with a heat exchanger upstream of the flow measurement	N/A	1 Hz
7.6 8.2.1	Diluted exhaust gas flow rate from a CVS without a heat exchanger upstream of the flow measurement	5 Hz	1 Hz means
7.6 8.2.1	Intake-air or exhaust gas flow rate (for raw transient measurement)	N/A	1 Hz means
7.6 8.2.1	Dilution air if actively controlled	5 Hz	1 Hz means
7.6 8.2.1	Sample flow from a CVS with a heat exchanger	1 Hz	1 Hz
7.6 8.2.1	Sample flow from a CVS without a heat exchanger	5 Hz	1 Hz mean

9.4.3.   Performance specifications for measurement instruments

9.4.3.1.   Overview

The test system as a whole shall meet all the applicable calibrations, verifications, and test-validation criteria specified in point 8.1, including the requirements of the linearity check of points 8.1.4 and 8.2. Instruments shall meet the specifications in Table 6.7 for all ranges to be used for testing. Furthermore, any documentation received from instrument manufacturers showing that instruments meet the specifications in Table 6.7 shall be kept.

9.4.3.2.   Component requirements

Table 6.8 shows the specifications of transducers of torque, speed, and pressure, sensors of temperature and dew point, and other instruments. The overall system for measuring the given physical and/or chemical quantity shall meet the linearity verification in point 8.1.4. For gaseous emissions measurements, analyzers may be used, that have compensation algorithms that are functions of other measured gaseous components, and of the fuel properties for the specific engine test. Any compensation algorithm shall only provide offset compensation without affecting any gain (that is no bias).

Table 6.8

Recommended performance specifications for measurement instruments

Measurement Instrument	Measured quantity symbol	Complete System Rise time	Recording update frequency	Accuracy [^E0013]	Repeatability [^E0013]
Engine speed transducer	n	1 s	1 Hz means	2,0 % of pt. or 0,5 % of max	1,0 % of pt. or 0,25 % of max
Engine torque transducer	T	1 s	1 Hz means	2,0 % of pt. or 1,0 % of max	1,0 % of pt. or 0,5 % of max
Fuel flow meter (Fuel totalizer)		5 s (N/A)	1 Hz (N/A)	2,0 % of pt. or 1,5 % of max	1,0 % of pt. or 0,75 % of max
Total diluted exhaust gas meter (CVS) (With heat exchanger before meter)		1 s (5 s)	1 Hz means (1 Hz)	2,0 % of pt. or 1,5 % of max	1,0 % of pt. or 0,75 % of max
Dilution air, inlet air, exhaust gas, and sample flow meters		1 s	1 Hz means of 5 Hz samples	2,5 % of pt. or 1,5 % of max	1,25 % of pt. or 0,75 % of max
Continuous gas analyzer raw	x	5 s	2 Hz	2,0 % of pt. or 2,0 % of meas.	1,0 % of pt. or 1,0 % of meas.
Continuous gas analyzer dilute	x	5 s	1 Hz	2,0 % of pt. or 2,0 % of meas.	1,0 % of pt. or 1,0 % of meas.
Continuous gas analyzer	x	5 s	1 Hz	2,0 % of pt. or 2,0 % of meas.	1,0 % of pt. or 1,0 % of meas.
Batch gas analyzer	x	N/A	N/A	2,0 % of pt. or 2,0 % of meas.	1,0 % of pt. or 1,0 % of meas.
Gravimetric PM balance	m PM	N/A	N/A	See 9.4.11	0,5 μg
Inertial PM balance	m PM	5 s	1 Hz	2,0 % of pt. or 2,0 % of meas.	1,0 % of pt. or 1,0 % of meas.

Accuracy and repeatability are all determined with the same collected data, as described in point 9.4.3, and based on absolute values. ‘pt.’ refers to the overall mean value expected at the emission limit; ‘max.’ refers to the peak value expected at the emission limit over the duty cycle, not the maximum of the instrument's range; ‘meas.’ refers to the actual mean measured over the duty cycle.

9.4.4.   Measurement of engine parameters & ambient conditions

9.4.4.1.   Speed and torque sensors

9.4.4.1.1.   Application

Measurement instruments for work inputs and outputs during engine operation shall meet the specifications in this point. Sensors, transducers, and meters meeting the specifications in Table 6.8 are recommended. Overall systems for measuring work inputs and outputs shall meet the linearity verifications in point 8.1.4.

9.4.4.1.2.   Shaft work

Work and power shall be calculated from outputs of speed and torque transducers according to point 9.4.4.1. Overall systems for measuring speed and torque shall meet the calibration and verifications in points 8.1.7 and 8.1.4.

Torque induced by the inertia of accelerating and decelerating components connected to the flywheel, such as the drive shaft and dynamometer rotor, shall be compensated for as needed, based on good engineering judgment.

9.4.4.2.   Pressure transducers, temperature sensors, and dew point sensors

Overall systems for measuring pressure, temperature, and dew point shall meet the calibration in point 8.1.7.

Pressure transducers shall be located in a temperature-controlled environment, or they shall compensate for temperature changes over their expected operating range. Transducer materials shall be compatible with the fluid being measured.

9.4.5.   Flow-related measurements

For any type of flow meter (of fuel, intake-air, raw exhaust gas, diluted exhaust gas, sample), the flow shall be conditioned as needed to prevent wakes, eddies, circulating flows, or flow pulsations from affecting the accuracy or repeatability of the meter. For some meters, this may be accomplished by using a sufficient length of straight tubing (such as a length equal to at least 10 pipe diameters) or by using specially designed tubing bends, straightening fins, orifice plates (or pneumatic pulsation dampeners for the fuel flow meter) to establish a steady and predictable velocity profile upstream of the meter.

9.4.5.1.   Fuel flow meter

Overall system for measuring fuel flow shall meet the calibration in point 8.1.8.1. In any fuel flow measurement it shall be accounted for any fuel that bypasses the engine or returns from the engine to the fuel storage tank.

9.4.5.2.   Intake-air flow meter

Overall system for measuring intake-air flow shall meet the calibration in point 8.1.8.2.

9.4.5.3.   Raw exhaust flow meter

9.4.5.3.1.   Component requirements

The overall system for measuring raw exhaust gas flow shall meet the linearity requirements in point 8.1.4. Any raw-exhaust meter shall be designed to appropriately compensate for changes in the raw exhaust gas' thermodynamic, fluid, and compositional states.

9.4.5.3.2.   Flow meter response time

For the purpose of controlling of a partial flow dilution system to extract a proportional raw exhaust gas sample, a flow meter response time faster than indicated in Table 6.8 is required. For partial flow dilution systems with online control, the flow meter response time shall meet the specifications of point 8.2.1.2.

9.4.5.3.3.   Exhaust gas cooling

This point does not apply to cooling of the exhaust gas due to the design of the engine, including, but not limited to, water-cooled exhaust manifolds or turbochargers.

Exhaust gas cooling upstream of the flow meter is permitted with the following restrictions:

• (a) PM shall not be sampled downstream of the cooling;

• (b) If cooling causes exhaust gas temperatures above 475 K (202 °C) to decrease to below 453 K (180 °C), HC shall not be sampled downstream of the cooling;

• (c) If cooling causes aqueous condensation, NOx shall not be sampled downstream of the cooling unless the cooler meets the performance verification in point 8.1.11.4;

• (d) If cooling causes aqueous condensation before the flow reaches a flow meter, dew point T dew and pressure p total shall be measured at the flow meter inlet. These values shall be used in emission calculations in accordance with Annex VII.

9.4.5.4.   Dilution air and diluted exhaust flow meters

9.4.5.4.1.   Application

Instantaneous diluted exhaust gas flow rates or total diluted exhaust gas flow over a test interval shall be determined by using a diluted exhaust flow meter. Raw exhaust gas flow rates or total raw exhaust gas flow over a test interval may be calculated from the difference between a diluted exhaust flow meter and a dilution air meter.

9.4.5.4.2.   Component requirements

The overall system for measuring diluted exhaust gas flow shall meet the calibration and verifications in points 8.1.8.4 and 8.1.8.5. The following meters may be used:

• (a) For constant-volume sampling (CVS) of the total flow of diluted exhaust gas, a critical-flow venturi (CFV) or multiple critical-flow venturis arranged in parallel, a positive-displacement pump (PDP), a subsonic venturi (SSV), or an ultrasonic flow meter (UFM) may be used. Combined with an upstream heat exchanger, either a CFV or a PDP will also function as a passive flow controller by keeping the diluted exhaust gas temperature constant in a CVS system;

• (b) For the Partial Flow Dilution (PFD) system the combination of any flow meter with any active flow control system to maintain proportional sampling of exhaust gas constituents may be used. The total flow of diluted exhaust gas, or one or more sample flows, or a combination of these flow controls may be controlled to maintain proportional sampling.

For any other dilution system, a laminar flow element, an ultrasonic flow meter, a subsonic venturi, a critical-flow venturi or multiple critical-flow venturis arranged in parallel, a positive-displacement meter, a thermal-mass meter, an averaging Pitot tube, or a hot-wire anemometer may be used.

9.4.5.4.3.   Exhaust gas cooling

Diluted exhaust gas upstream of a dilute flow meter may be cooled, as long as all the following provisions are observed:

• (a) PM shall not be sampled downstream of the cooling;

• (b) If cooling causes exhaust gas temperatures above 475 K (202 °C) to decrease to below 453 K (180 °C), HC shall not be sampled downstream of the cooling;

• (c) If cooling causes aqueous condensation, NOx shall not be sampled downstream of the cooling unless the cooler meets the performance verification in point 8.1.11.4;

• (d) If cooling causes aqueous condensation before the flow reaches a flow meter, dew point, T dew and pressure p total shall be measured at the flow meter inlet. These values shall be used in emission calculations in accordance with Annex VII.

9.4.5.5.   Sample flow meter for batch sampling

A sample flow meter shall be used to determine sample flow rates or total flow sampled into a batch sampling system over a test interval. The difference between two flow meters may be used to calculate sample flow into a dilution tunnel e.g. for partial flow dilution PM measurement and secondary dilution flow PM measurement. Specifications for differential flow measurement to extract a proportional raw exhaust gas sample is set out in point 8.1.8.6.1 and the calibration of differential flow measurement is given in point 8.1.8.6.2.

Overall system for the sample flow meter shall meet the calibration requirements set out in point 8.1.8.

9.4.5.6.   Gas divider

A gas divider may be used to blend calibration gases.

A gas divider shall be used that blends gases to the specifications of point 9.5.1 and to the concentrations expected during testing. Critical-flow gas dividers, capillary-tube gas dividers, or thermal-mass-meter gas dividers may be used. Viscosity corrections shall be applied as necessary (if not done by gas divider internal software) to appropriately ensure correct gas division. The gas-divider system shall meet the linearity verification set out in point 8.1.4.5. Optionally, the blending device may be checked with an instrument which by nature is linear, e.g. using NO gas with a CLD. The span value of the instrument shall be adjusted with the span gas directly connected to the instrument. The gas divider shall be checked at the settings used and the nominal value shall be compared to the measured concentration of the instrument.

9.4.6.   CO and CO2 measurements

A Non-dispersive infrared (NDIR) analyzer shall be used to measure CO and CO2 concentrations in raw or diluted exhaust gas for either batch or continuous sampling.

The NDIR-based system shall meet the calibration and verifications set out in point 8.1.9.1 or 8.1.9.2, as applicable.

9.4.7.   Hydrocarbon measurements

9.4.7.1.   Flame-ionization detector

9.4.7.1.1.   Application

A heated flame-ionization detector (HFID) analyzer shall be used to measure hydrocarbon concentrations in raw or diluted exhaust gas for either batch or continuous sampling. Hydrocarbon concentrations shall be determined on a carbon number basis of one, C1. Heated FID analyzers shall maintain all surfaces that are exposed to emissions at a temperature of 464 ± 11 K (191 ± 11 °C). Optionally, for NG and LPG fuelled and SI engines, the hydrocarbon analyzer may be of the non-heated flame ionization detector (FID) type.

9.4.7.1.2.   Component requirements

The FID-based system for measuring THC shall meet all of the verifications for hydrocarbon measurement in point 8.1.10.

9.4.7.1.3.   FID fuel and burner air

FID fuel and burner air shall meet the specifications of point 9.5.1. The FID fuel and burner air shall not mix before entering the FID analyzer to ensure that the FID analyzer operates with a diffusion flame and not a premixed flame.

9.4.7.1.4.   Reserved

9.4.7.1.5.   Reserved

9.4.7.2.   Reserved

9.4.8.   NOx measurements

Two measurement instruments are specified for NOx measurement and either instrument may be used provided it meets the criteria specified in point 9.4.8.1 or 9.4.8.2, respectively. The chemiluminescent detector shall be used as the reference procedure for comparison with any proposed alternate measurement procedure under point 5.1.1.

9.4.8.1.   Chemiluminescent detector

9.4.8.1.1.   Application

A chemiluminescent detector (CLD) coupled with an NO2-to-NO converter is used to measure NOx concentration in raw or diluted exhaust gas for batch or continuous sampling.

9.4.8.1.2.   Component requirements

The CLD-based system shall meet the quench verification set out in point 8.1.11.1. A heated or unheated CLD may be used, and a CLD that operates at atmospheric pressure or under a vacuum may be used.

9.4.8.1.3.   NO2-to-NO converter

An internal or external NO2-to-NO converter that meets the verification in point 8.1.11.5 shall be placed upstream of the CLD, while the converter shall be configured with a bypass to facilitate this verification.

9.4.8.1.4.   Humidity effects

All CLD temperatures shall be maintained to prevent aqueous condensation. To remove humidity from a sample upstream of a CLD, one of the following configurations shall be used:

• (a) A CLD connected downstream of any dryer or chiller that is downstream of an NO2-to-NO converter that meets the verification set out in point 8.1.11.5;

• (b) A CLD connected downstream of any dryer or thermal chiller that meets the verification set out in point 8.1.11.4.

9.4.8.1.5.   Response time

A heated CLD may be used to improve CLD response time.

9.4.8.2.   Non-dispersive ultraviolet analyzer

9.4.8.2.1.   Application

A non-dispersive ultraviolet (NDUV) analyzer is used to measure NOx concentration in raw or diluted exhaust gas for batch or continuous sampling.

9.4.8.2.2.   Component requirements

The NDUV-based system shall meet the verifications set out in point 8.1.11.3.

9.4.8.2.3.   NO2-to-NO converter

If the NDUV analyzer measures only NO, an internal or external NO2-to-NO converter that meets the verification set out in point 8.1.11.5 shall be placed upstream of the NDUV analyzer. The converter shall be configured with a bypass to facilitate this verification.

9.4.8.2.4.   Humidity effects

The NDUV temperature shall be maintained to prevent aqueous condensation, unless one of the following configurations is used:

• (a) An NDUV shall be connected downstream of any dryer or chiller that is downstream of an NO2-to-NO converter that meets the verification in point 8.1.11.5;

- (b) An NDUV shall be connected downstream of any dryer or thermal chiller that meets the verification in point 8.1.11.4.

9.4.9.   O2 measurements

A paramagnetic detection (PMD) or magneto pneumatic detection (MPD) analyzer shall be used to measure O2 concentration in raw or diluted exhaust gas for batch or continuous sampling.

9.4.10.   Air-to-fuel ratio measurements

A Zirconia (ZrO2) analyser may be used to measure air-to-fuel ratio in raw exhaust gas for continuous sampling. O2 measurements with intake air or fuel flow measurements may be used to calculate exhaust gas flow rate in accordance with Annex VII.

9.4.11.   PM measurements with gravimetric balance

A balance shall be used to weigh net PM collected on sample filter media.

The minimum requirement on the balance resolution shall be equal or lower than the repeatability of 0,5 microgram recommended in Table 6.8. If the balance uses internal calibration weights for routine spanning and linearity verifications, the calibration weights shall meet the specifications in point 9.5.2.

The balance shall be configured for optimum settling time and stability at its location.

9.4.12.   Ammonia (NH3) measurements

A FTIR (Fourier transform infrared) analyser, NDUV or laser infrared analyser may be used in accordance with Appendix 4.

9.5.   Analytical gases and mass standards

9.5.1.   Analytical gases