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h)) to pass, before setting valve A back to "bypass"
and close valve D:
g) set aside stained filter for analysis, clamp clean filter
into holder;
h) the chosen sample sizes shall be such as to be within
the range of 12 kg to 21 kg of exhaust gas per square
metre of filter, and shall include samples which are
either at the value of 16.2 kg of kxhaust gas per
square metre of filter or lie above and below that
The stained filter specimens obtained as outlined in 2.5.3
shdl be analysed using a reflectorneter as specified in 2.3.
The backing material used shall be black with an absolute
reflectance of less than 3 per cent. The absolute reflectance
reading R, of each stained filter shall be used to calculate the
reduction in reflectance by
where R, is the absolute reflectance of clean filter material.
The masses of the various samples shall be calculated by
where P and T are, respectively, the sample pressure in
pascals and the temperature in kelvin, measured imnediately
upstream of the volume meter. V is the measured sample
volume in cubic metres.
For each engine condition in the case that the sample
sizes lmge above and below the reference value, the vaciaus
values of SN' and W shall be plotted as SN' versus log W/A,
where A is the filter stain area (m2). Using a least squares
straight line fit, the value of SN' for W/A = 16.2 kglm2 shall
be estimated and reported as the Smoke Number (SN) for that
engine mode. Where sampling at the reference size value only
is employed, the reported SN shall be the arithmetic average
of the various individual values of SN'.
4. REPORTING OF DATA TO THE
CERTIFICATING AUTHORITY
The measured data shall be reported to the certificating
authority. In addition the following data shall be reported for
each test:
a) sample temperature;
b) sample pressure;
c) actual sample volume at sampling conditions;
d) actual sample flow rate at sampling conditions; and
e) leak and deanliness checks substantiation bee 2.5.2).
APPENDIX 3. INSTRUMENTATION AND MEASUREMENT TECHNIQUES
FOR GASEOUS EMISSIONS
Note.- The procedures specged in this appendix are
concerned with the acquisition of representative exhaust
samples and their transmission to, and analysis by, the
emissions measuring system The procedures do not apply to
engines employing afterburning. The methods proposed are
representative of the best readily available and most
established practice.
Variations in the procedure contained in this appendix
shall only be allowed after prior application to and approval
by the certificating authority.
2. DEFINITIONS
Where the following expressions are used in this appendix,
they have the meanings ascribed to them below:
Accuracy. The closeness with which a measurement
approaches the true value established independently.
Airfluel ratio. The mass rate of airflow through the hot
section of the engine divided by the mass rate of fuel flow to
tlle engine.
Noise. Random variation in instrument output not associated
with characteristics of the sample to which the instrument
is responding, and distinguishable from its drift
characteristics.
Non-dispersive in*-ned analyser. An instrument that by
absorption of infra-red energy selectively measures specific
components.
Parts per malion (pprn). The unit volume concentration
of a gas per million unit volume of the gas mixture of which
it is a part.
Parts per million carbon (ppmC). The mole fraction of
hydrocarbon multiplied by lo6 measured on a methaneequivalence
basis. Thus, 1 ppm of methane is indicated as
1 ppmC. To convert ppm concentration of any hydrocarbon
to an equivalent pprnC value, multiply pprn concentration by
the number of carbon atoms per molecule of the gas. For
example, 1 ppm propane translates as 3 ppmC hydrocarbon;
1 ppm hexane as 6 ppmC hydrocarbon.
Reference gas. A mixture of gases of specified and
known composition used as the basis for interpreting insuument
response in terms of the concentration of the gas to
which the instrument is responding.
Calibration gas. A high accuracy reference gas to be used Repeatability. The closeness with which a measurement
for alignment, adjustment and periodic checks of instruments. upon a given, invariant sample can be reproduced in shorttam
repetitions of the measurement with no intervening
Concentrution. The volume fraction of the component of instrument adjustment.
interest in the gas mixture - expressed as volume percentage
or as parts per million. Resolution. The smallest change in a measurement which
Exhaust n o d . In the exhaust emissions sampling of gas Can be detected*
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