ISO 16183:2002
(Main)Heavy duty engines — Measurement of gaseous emissions from raw exhaust gas and of particulate emissions using partial flow dilution systems under transient test conditions
Heavy duty engines — Measurement of gaseous emissions from raw exhaust gas and of particulate emissions using partial flow dilution systems under transient test conditions
ISO 16183 specifies methods for the measurement and evaluation of gaseous and particulate exhaust emissions from heavy-duty engines under transient conditions on a test bed. The procedures it defines can be applied to any transient test cycle that does not require extreme system response times; it can therefore be used as an option to the regulated measurement equipment (usually CVS-type systems) of certification test cycles (e.g. ETC and FTP), with the approval of the certification agency. ISO 16183 is applicable to heavy-duty engines for commercial vehicles primarily designed for road use, but can also be applied to passenger car engines and to engines used for non-road applications. The test equipment specified can also be applied to steady-state test cycles, however, if so, the calculation procedures will need to be replaced by those applicable to the particular test cycle.
Moteurs de poids lourds — Détermination, sur cycle transitoire, des émissions de polluants gazeux par mesure des concentrations dans les gaz d'échappement bruts et des émissions de particules en utilisant un système de dilution partielle
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 16183
First edition
2002-12-15
Heavy-duty engines — Measurement of
gaseous emissions from raw exhaust gas
and of particulate emissions using partial
flow dilution systems under transient test
conditions
Moteurs de poids lourds — Détermination, sur cycle transitoire, des
émissions de polluants gazeux par mesure des concentrations dans les
gaz d'échappement bruts et des émissions de particules en utilisant un
système de dilution partielle
Reference number
©
ISO 2002
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ii © ISO 2002 – All rights reserved
Contents Page
Foreword . iv
Introduction. v
1 Scope. 1
2 Normative references. 1
3 Terms, definitions, symbols and abbreviations. 1
4 Test conditions. 7
4.1 Engine test conditions. 7
4.2 Engines with charge air cooling . 8
4.3 Power. 8
4.4 Engine air intake system . 8
4.5 Engine exhaust system . 8
4.6 Cooling system. 8
4.7 Lubricating oil. 9
4.8 Test fuel. 9
5 Determination of gaseous and particulate components. 9
5.1 General . 9
5.2 Equivalence . 9
5.3 Accuracy . 11
5.4 Determination of exhaust gas mass flow . 11
5.5 Determination of gaseous components. 14
5.6 Particulate determination . 18
6 Measurement equipment for the gaseous components . 21
6.1 Analyser specifications . 21
6.2 Analysers . 22
6.3 Calibration. 24
6.4 Analytical system . 35
7 Measurement equipment for particulates. 44
7.1 Specifications . 44
7.2 Dilution and sampling system . 46
7.3 Calibration. 52
Annex A (normative) Determination of system equivalence. 55
Annex B (normative) Determination of system sampling error. 56
Annex C (normative) Carbon flow check . 58
Annex D (informative) Calculation procedure — Example . 60
Bibliography. 64
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
The main task of technical committees is to prepare International Standards. Draft International Standards adopted
by the technical committees are circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16183 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 5, Engine tests.
Annexes A, B and C form a normative part of this International Standard. Annex D is for information only.
iv © ISO 2002 – All rights reserved
Introduction
Today's emission measurement systems depend on the type of test cycle — steady-state or transient — and the
type of pollutant to be measured.
In a steady-state cycle, the mass of gaseous emissions is calculated from the concentration in the raw exhaust gas
and the exhaust flow of the engine, which can easily be determined. For particulate matter (PM), partial-flow
dilution systems, in which only a portion of the exhaust gas is diluted, are widely used.
In a transient cycle, real time exhaust flow determination is more difficult. Therefore, the constant volume sampling
(CVS) principle has been used for many years because exhaust mass flow measurement is not required with this
system. The total exhaust gas is diluted, the total flow as the sum of dilution air and exhaust gas volume is kept
virtually constant, and the emissions (both gaseous and PM) are measured in the diluted exhaust gas. The space
and cost requirements of such a system are considerably higher than for the partial-flow dilution systems used in
steady-state cycles. Nevertheless, raw exhaust measurement and partial flow systems can only be applied to
transients if sophisticated control systems and calculation algorithms are used.
The mass emission determination in a raw exhaust sample and the measurement of the exhaust gas mass flow
rate is a state-of-the-art procedure for light duty vehicle development on chassis dynamometers. There it is called
modal analysis. However, it is usually done in conjunction with the mass emission evaluation on a full-flow CVS
with bag analysis, where quality of the modal results can easily be verified by comparison with the CVS bag results.
For heavy-duty engines, the CVS system is a large and costly system.
The aim of this International Standard is to provide an optional, stand-alone measurement procedure. By the nature
of the transient mass emission calculation, small changes could result in large deviations of the final results, for
example, by a wrongly performed time alignment caused by a wrong response time determination or by a system
fault resulting in a change of the response time behaviour of the system. Therefore, the quality assurance
procedure of a carbon dioxide-based carbon balance check, in line with highly sophisticated verification procedures
for the partial flow particulate measurement, have been established in this International Standard.
NOTE CVS systems are covered in detail in various exhaust emissions regulations for both light- and heavy-duty vehicles
as well as by ISO 8178-1. They are therefore not included in this International Standard. Since they are considered to be the
reference systems for exhaust emission measurement on transient cycles, extensive studies have been commissioned by
ISO/TC 22/SC 5/WG 2 on the correlation between CVS systems and the systems covered by this International Standard, with
the results having been taken into consideration in its development.
INTERNATIONAL STANDARD ISO 16183:2002(E)
Heavy-duty engines — Measurement of gaseous emissions from
raw exhaust gas and of particulate emissions using partial flow
dilution systems under transient test conditions
1 Scope
This International Standard specifies methods for the measurement and evaluation of gaseous and particulate
exhaust emissions from heavy-duty engines under transient conditions on a test bed. The procedures it defines can
be applied to any transient test cycle that does not require extreme system response times; it can therefore be
used as an option to the regulated measurement equipment of certification test cycles — usually CVS-type
systems — with the approval of the certification agency [among certification test cycles in place are the European
transient cycle (ETC) and the US heavy-duty transient cycle (FTP)].
This International Standard is applicable to heavy-duty engines for commercial vehicles primarily designed for road
use, but can also be applied to passenger car engines and to engines used for non-road applications. The test
equipment specified in this International Standard can also be used in steady-state test cycles, however, if so, the
calculation procedures will need to be replaced by those applicable to the particular test cycle.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 5167-1, Measurement of fluid flow by means of pressure differential devices — Part 1: Orifice plates, nozzles
and Venturi tubes inserted in circular cross-section conduits running full
ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for
the determination of repeatability and reproducibility of a standard measurement method
ISO 8178-5:1998, Reciprocating internal combustion engines — Exhaust emission measurement — Part 5: Test
fuels
SAE paper 770141, Optimization of Flame Ionization Detector for the Determination of Hydrocarbons in Diluted
Automobile Exhaust, Glenn D. Reschke
SAE J 1936:1989, Chemical methods for the measurement of non-regulated diesel emissions
SAE J 1937:1995, Engine testing with low-temperature charge air-cooler systems in a dynamometer test cell
3 Terms, definitions, symbols and abbreviations
For the purposes of this International Standard, the following terms and definitions, and symbols and abbreviations
(see Table 1), apply.
3.1
particulate matter
PM
any material collected on a specified filter medium after diluting exhaust with clean filtered air to a temperature of
u 325 K (52 °C), as measured at a point immediately upstream of the filter; it is primarily carbon, condensed
hydrocarbons, and sulfates with associated water
NOTE Regulatory agencies choosing to use ISO 16183 could adapt this definition to their particular needs. For example,
US regulations after 2007 will define particulate matter at a temperature greater than 42 °C and less than 52 °C.
3.2
gaseous pollutant
gas considered to be polluting to the atmosphere: carbon monoxide, hydrocarbons or non-methane hydrocarbons,
or both these, oxides of nitrogen [expressed in nitrogen dioxide (NO ) equivalent], formaldehyde and methanol
3.3
partial-flow dilution method
process of separating a part of the raw exhaust from the total exhaust flow, then mixing it with an appropriate
amount of dilution air prior to the particulate sampling filter
3.4
full-flow dilution method
process of mixing dilution air with the total exhaust flow prior to separating a fraction of the diluted exhaust stream
for analysis
NOTE It is common in many full flow dilution systems to dilute this fraction of pre-diluted exhaust a second time to obtain
appropriate sample temperatures at the particulate filter.
3.5
specific emission
mass emission expressed in grams per kilowatt hour
3.6
steady-state test cycle
test cycle comprising a sequence of engine test modes in which the engine is given sufficient time to achieve
defined speed, torque and stability criteria at each mode
3.7
transient test cycle
test cycle comprising a sequence of normalized speed and torque values that vary relatively quickly with time
3.8
response time
difference in time between a rapid change of the component to be measured at the reference point and the
appropriate change in the response of the measuring system, whereby the change of the measured component is
at least 60 % FS (full scale) and takes place within less than 0,1 s
See Figure 1.
NOTE 1 The system response time, t , consists of the delay time to the system and of the rise time of the system.
NOTE 2 The response time can vary, depending on where the reference point for the change of the component to be
measured is defined: either at the sampling probe or directly at the port entrance of the analyser. For the purposes of this
International Standard, the sampling probe is defined as the reference point.
3.9
delay time
time between the change of the component to be measured at the reference point and a system response of 10 %
of the final reading, t
2 © ISO 2002 – All rights reserved
See Figure 1.
NOTE 1 For the gaseous components, this is basically the transport time of the measured component from the sampling
probe to the detector.
NOTE 2 The delay time can vary, depending on where the reference point for the change of the component to be measured
is defined: either at the sampling probe or directly at the port entrance of the analyser. For the purposes of this International
Standard, the sampling probe is defined as the reference point.
3.10
rise time
time between the 10 % and 90 % response of the final reading (t − t )
90 10
See Figure 1.
NOTE 1 This is the instrument response after the component to be measured has reached the instrument.
NOTE 2 The rise time can vary, depending on where the reference point for the change of the component to be measured is
defined: either at the sampling probe or directly at the port entrance of the analyser. For the purposes of this International
Standard, the sampling probe is defined as the reference point.
3.11
transformation time
time between the change of the component to be measured at the reference point and a system response of 50 %
of the final reading, t
See Figure 1.
NOTE 1 The transformation time is used for the signal alignment of different measurement instruments.
NOTE 2 The transformation time can vary, depending on where the reference point for the change of the component to be
measured is defined: either at the sampling probe or directly at the port entrance of the analyser. For the purposes of this
International Standard, the sampling probe is defined as the reference point.
Figure 1 — Definitions of system response
Table 1 — General symbols and abbreviations used in this International Standard
Symbol/Abbreviation Unit Meaning
A/F
— Stoichiometric air-to-fuel ratio
st
a
ppm (µl/l) or % by
c Concentration
volume
C
— Slip factor
c
d
m Exhaust pipe diameter
e
d
m Sampling probe diameter
p
d
m Particle diameter
PM
f Hz Data sampling rate
f
— Laboratory atmospheric factor
a
E CO quench of NO analyser
%
CO2 2 x
E
% Ethane efficiency
E
E Water quench of NO analyser
%
H2O x
E
% Methane efficiency
M
E Efficiency of NO converter
%
NOx x
Dynamic viscosity of exhaust gas
η Pa⋅s
H
g/kg Absolute humidity of the intake air
a
i — Subscript denoting an instantaneous measurement (e.g. 1 Hz)
k
— Fuel specific factor
f
k Humidity correction factor for NO for CI engines
—
h,D x
k Humidity correction factor for NO for SI engines
—
h,G x
k
— Dry to wet correction factor for the raw exhaust gas
w
λ — Excess air ratio
m
kg Mass of equivalent diluted exhaust gas over the cycle
edf
m
mg Particulate sample mass collected
f
m
g Mass of gaseous emissions (over the test cycle)
gas
m
g Mass of particulate emissions (over the test cycle)
PM
m
kg Exhaust sample mass over the cycle
se
m
kg Mass of diluted exhaust gas passing the dilution tunnel
sed
m
kg Mass of diluted exhaust gas passing the particulate collection filters
sep
M
g/kWh Specific emission of gaseous emissions
gas
M
g/kWh Specific emission of particulate emissions
PM
b
M
— Molecular mass of exhaust
r,e
M
— Molecular mass of exhaust component
r,gas
4 © ISO 2002 – All rights reserved
Table 1 (continued)
Symbol/Abbreviation Unit Meaning
n — Number of measurements
p kPa Saturation vapour pressure of the engine intake air
a
p kPa Total atmospheric pressure
b
p kPa Water vapour pressure after cooling bath
r
p kPa Dry atmospheric pressure
s
P
— Particle penetration
q kg/s Intake air mass flow rate on dry basis
mad
q kg/s Intake air mass flow rate on wet basis
maw
q kg/s Carbon mass flow rate in the raw exhaust gas
mCe
q kg/s Carbon mass flow rate into the engine
mCf
q kg/s Carbon mass flow rate in the partial-flow dilution system
mCp
q kg/s Diluted exhaust gas mass flow rate on wet basis
mdew
q kg/s Dilution air mass flow rate on wet basis
mdw
q kg/s Equivalent diluted exhaust gas mass flow rate on wet basis
medf
q kg/s Exhaust gas mass flow rate on wet basis
mew
q kg/s Sample mass flow rate extracted from dilution tunnel
mex
q kg/s Fuel mass flow rate
mf
q kg/s Sample flow of exhaust gas into partial-flow dilution system
mp
q l/min System flow rate of exhaust analyser system
vs
q cm /min Tracer gas flow rate
vt
r — Dilution ratio
d
r — Hydrocarbon response factor of the FID
h
r — Methanol response factor of the FID
m
r — Average sample ratio
s
ρ kg/m Exhaust gas density (wet, at 273 K and 101,3 kPa)
e
ρ kg/m Density of exhaust component (at 273 K and 101,3 kPa)
gas
ρ kg/m Particle density (at 273 K and 101 kPa)
PM
σ Standard deviation
T K Absolute temperature
T K Absolute temperature of the intake air
a
T K Exhaust gas temperature
e
t s Time between step input and 10 % of final reading
t s Time between step input and 50 % of final reading
t s Time between step input and 90 % of final reading
τ s Particle relaxation time
u — Ratio between densities of gas component and exhaust gas
V l Total volume of exhaust analyser system
s
Table 1 (continued)
Symbol/Abbreviation Unit Meaning
W kWh Actual cycle work of the respective test cycle
act
υ m/s Gas velocity in the exhaust pipe
e
υ m/s Gas velocity in the sampling probe
p
Symbols specific to fuel composition
w — Hydrogen content of fuel, % by mass
ALF
w — Carbon content of fuel, % by mass
BET
w — Sulfur content of fuel, % by mass
GAM
w — Nitrogen content of fuel, % by mass
DEL
w — Oxygen content of fuel, % by mass
EPS
α — Molar hydrogen ratio (H/C)
β — Molar carbon ratio (C/C)
γ — Molar sulfur ratio (S/C)
δ — Molar nitrogen ratio (N/C)
ε — Molar oxygen ratio (O/C)
Referring to a fuel C H O N S
β α ε δ γ
Symbols and abbreviations for chemical components
ACN — Acetonitrile
C1 — Carbon 1 equivalent hydrocarbon
CH — Methane
CHOH — Methanol
C H — Ethane
2 6
C H — Propane
3 8
CO — Carbon monoxide
CO — Carbon dioxide
DNPH — Dinitrophenyl hydrazine
DOP — Di-octylphtalate
HC — Hydrocarbons
HCHO — Formaldehyde
HO — Water
NMHC — Non-methane hydrocarbons
NO — Oxides of nitrogen
x
NO — Nitric oxide
NO — Nitrogen dioxide
PM — Particulate matter
RME — Rapeseed oil methyl ester
6 © ISO 2002 – All rights reserved
Table 1 (continued)
Symbol/Abbreviation Unit Meaning
Other abbreviations
CLD — Chemiluminescent detector
FID — Flame ionization detector
FTIR — Fourier transform infrared (analyser)
GC — Gas chromatograph
HCLD — Heated chemiluminescent detector
HFID — Heated flame ionization detector
HPLC — High pressure liquid chromatograph
NDIR — Non-dispersive infrared (analyser)
NMC — Non-methane cutter
% FS — Percentage of full scale
SIMS — Soft ionization mass spectrometer
St — Stokes number
a
“Parts per million (ppm)” is a deprecated unit, i.e. not accepted by the International System of Units, SI. It is used exceptionally in this
International Standard, immediately followed by the SI unit of equivalent value in parentheses, in order to correspond to other, closely related
and already published standards. The accepted SI form for the expression of a volume fraction is in units of microlitres per litre (µl/l), or,
−6
alternatively, as 10 or as a percentage by volume (% by volume); for mass fractions it is expressed in micrograms per gram (µg/g). See
ISO 31-0:1992, 2.3.3, and ISO 31-8-15:1992.
b
Formerly called molecular weight.
4 Test conditions
4.1 Engine test conditions
4.1.1 Test condition parameter
The absolute temperature (T ) of the engine air at the inlet to the engine, expressed in kelvin, and the dry
a
atmospheric pressure (p ), expressed in kilopascals, shall be measured, and the parameter f determined in
s a
accordance with the following provisions. In multi-cylinder engines having distinct groups of intake manifolds, such
as in a "vee" engine configuration, the average temperature of the distinct groups shall be taken.
a) For compression-ignition engines:
Naturally aspirated and mechanically supercharged engines
0,7
99 T
a
f=× (1)
a
p 298
s
Turbocharged engines, with or without cooling of the intake air
0,7
1,5
99 T
a
f=× (2)
a
p 298
s
b) For spark-ignition engines:
1,2
0,6
99
T
a
f=× (3)
a
p 298
s
4.1.2 Test validity
For a test to be recognized as valid, f shall be such that 0,96 u f u 1,06.
a a
4.2 Engines with charge air cooling
The charge air temperature shall be recorded and be within ± 5 K of the maximum charge air temperature specified
by the manufacturer at the speed of the declared maximum power and full load. The temperature of the cooling
medium shall be at least 293 K (20 °C).
If a test shop system or external blower is used, the charge air temperature shall be set to within ± 5 K of the
maximum charge air temperature specified by the manufacturer at the speed of the declared maximum power and
full load. Coolant temperature and coolant flow rate of the charge air cooler at the above set point shall not be
changed for the whole test cycle. The charge air cooler volume shall be based upon good engineering practice and
typical vehicle/machinery applications.
Optionally, the setting of the charge air cooler may be done in accordance with SAE J 1937.
4.3 Power
The basis of specific emissions measurement is uncorrected net or gross power, depending on the regulation.
Certain auxiliaries necessary only for the operation of the vehicle that can be mounted on the engine should be
removed for the test.
EXAMPLE Air compressor for brakes, power steering compressor, air conditioning compressor or pumps for hydraulic
actuators.
Where such auxiliaries have not been removed, the power absorbed by them shall be determined in order to adjust
the set values and calculate the work produced by the engine over the test cycle.
4.4 Engine air intake system
An engine air intake system shall be used presenting an air intake restriction within ± 300 Pa of the value specified
by the engine manufacturer for a clean air cleaner and in accordance with the respective regulation.
4.5 Engine exhaust system
A vehicle exhaust system or a test shop system shall be used presenting an exhaust backpressure within ± 650 Pa
of the value specified by the engine manufacturer and in accordance with the respective regulation. The exhaust
system shall conform to the requirements for exhaust gas sampling in 5.6.2 and 7.2.3, EP.
If the engine is equipped with an exhaust after-treatment device, the exhaust pipe shall have the same diameter as
found in-use for at least four pipe diameters upstream to the inlet of the beginning of the expansion section
containing the after-treatment device. The distance from the exhaust manifold flange or turbocharger outlet to the
exhaust after-treatment device shall be the same as in the vehicle configuration or within the distance
specifications of the manufacturer. The exhaust backpressure or restriction shall follow these same criteria, and
may be set with a valve. The after-treatment container may be removed during dummy tests and during engine
mapping and replaced with an equivalent container having an inactive catalyst support.
4.6 Cooling system
An engine cooling system with sufficient capacity to maintain the engine at normal operating temperatures
prescribed by the manufacturer shall be used.
8 © ISO 2002 – All rights reserved
4.7 Lubricating oil
The lubricating oil shall be as specified by the manufacturer; the specifications of the lubricating oil used for the test
shall be recorded and presented with the results of the test.
4.8 Test fuel
Fuel characteristics influence the engine exhaust gas emission. Therefore, the characteristics of the fuel used for
the test should be determined, recorded and declared with the results of the test. Where fuels designated as
reference fuels are used, the reference code and the analysis of the fuel shall be provided. For all other fuels, the
characteristics to be recorded shall be those listed in the appropriate universal data sheet of ISO 8178-5.
The fuel temperature shall be in accordance with the manufacturer's recommendations.
5 Determination of gaseous and particulate components
5.1 General
For the purpose of this International Standard, the gaseous components are measured in the raw exhaust gas on a
real time basis, and the particulates are determined using a partial-flow dilution system.
The instantaneous concentration signals of the gaseous components are used for the calculation of the mass
emissions by multiplication with the instantaneous exhaust mass flow rate. The exhaust mass flow rate may be
measured directly or calculated in accordance with 5.4.4 (intake air and fuel flow measurement), 5.4.5 (tracer
method) or 5.4.6 (intake air and air/fuel ratio measurement). Special attention shall be paid to the response times of
the different instruments. These differences shall be accounted for by time aligning the signals in accordance with
5.5.3.
For particulates, the exhaust mass flow rate signals given in 5.4 are used for controlling the partial-flow dilution
system in order that a sample proportional to the exhaust mass flow rate can be taken. The quality of
proportionality is checked by applying a regression analysis between sample and exhaust flow in accordance with
5.6.2.
The complete test set up is shown schematically in Figure 2.
5.2 Equivalence
The emission of gaseous and particulate components by the engine submitted for testing shall be measured in
accordance with clauses 6 and 7. These describe the recommended analytical systems for the gaseous emissions
(see clause 6) and the recommended particulate dilution and sampling systems (see clause 7).
Other systems or analysers may be accepted if they yield equivalent results. The determination of system
equivalency shall be based on a seven-sample pair (or larger) correlation study between the system under
consideration and one of the systems accepted by this International Standard. Results refers to the specific cycle
weighted emissions value. The correlation testing is to be performed at the same laboratory, on the same test cell,
and the same engine, and is preferably to be run concurrently. The test cycle to be used shall be the appropriate
cycle on which the engine will be run. The equivalency of the sample pair averages shall be determined by “t”-test
statistics as given in Annex A, obtained under these laboratory cell and engine conditions. Outliers shall be
determined in accordance with ISO 5725-2 and excluded from the database. The systems to be used for
correlation testing shall be declared prior to the test and shall be agreed upon by the parties involved.
For the introduction of a new system into the standard, the determination of equivalency shall be based upon the
calculation of repeatability and reproducibility in accordance with ISO 5725-2.
Key
Exhaust sample
Flow measurement
Signals for system control and computation
1 Fuel flow
2 Engine
3 Intake air flow
4 Exhaust gas analyser
5 Control unit
6 Partial-flow dilution system
7 Dilution air
8 Exhaust flow
a
Flow values
b
Flow control
c
Computation
Figure 2 — Schematic of measurement system
10 © ISO 2002 – All rights reserved
5.3 Accuracy
The equipment described in this International Standard shall be used for emissions tests of engines. This
International Standard does not specify particular flow, pressure or temperature measuring equipment. Instead,
only the accuracy requirements of such equipment necessary for conducting an emissions test are given. The
instruments shall be calibrated as required by internal audit procedures or by the instrument manufacturer.
The calibration of all measuring instruments shall be traceable to relevant national and international standards and
shall be in accordance with Table 2.
Table 2 — Permissible deviations of instruments
Number Measurement instrument Permissible deviation
1 Engine speed ± 2 % of reading or ± 1 % of engine's maximum value, whichever is greater
2 Torque ± 2 % of reading or ± 1 % of engine's maximum value, whichever is greater
3 Fuel consumption ± 2 % of engine's maximum value
4 Air consumption ± 2 % of reading or ± 1 % of engine's max. value, whichever is greater
5 Exhaust gas flow ± 2,5 % of reading or ± 1,5 % of engine's max. value, whichever is greater
6 Temperatures u 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
5.4 Determination of exhaust gas mass flow
5.4.1 Introduction
In order to calculate the emissions in the raw exhaust gas and control a partial-flow dilution system, it is necessary
to know the exhaust gas mass flow rate. For the determination of the exhaust mass flow rate, either of the methods
specified in 5.4.3 to 5.4.6 may be used.
5.4.2 Response time
For the purpose of emissions calculation, the response time of either method shall be less than or equal to the
requirement for the analyser response time, in accordance with 6.3.5.
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 u 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 u 5 s with a
rise time of u 1 s is required. The system response time shall be as specified by the instrument manufacturer. The
combined response time requirements for exhaust gas flow and partial-flow dilution systems are given in 5.6.3.
5.4.3 Direct measurement method
Direct measurement of the instantaneous exhaust flow may be done by systems including
pressure differential devices, such as flow nozzle (see ISO 5167-1),
ultrasonic flow meters, and
vortex flow meters.
Precautions shall be taken to avoid measurement errors that could have an impact on emission value errors. Such
precautions include the careful installation of the device in the engine exhaust system in accordance with the
instrument manufacturers' recommendations and good engineering practice. In particular, engine performance and
emissions shall not be affected by the installation of the device.
The flow meters shall meet the accuracy specifications of 5.3.
5.4.4 Air and fuel measurement method
This involves measurement of the air and fuel flows with suitable flow meters. The calculation of the instantaneous
exhaust gas flow is as follows:
q = q + q (4)
mew,i maw,i mf,i
(for wet exhaust mass)
The flow meters shall meet the accuracy specifications of 5.3, but shall be accurate enough to also meet the
accuracy specifications for the exhaust gas flow.
5.4.5 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 shall 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 analyser.
The calculation of the exhaust gas flow is as follows:
q × ρ
νte
q = (5)
miew,
60×−cc
()
mix,i a
where
q is the instantaneous exhaust mass flow, in kilograms per second;
mew,i
q is the tracer gas flow, in cubic centimetres per minute;
ν t
c is the instantaneous concentration of the tracer gas after mixing, in parts per million (microlitres per
mix,i
litre);
12 © ISO 2002 – All rights reserved
ρ is the density of the exhaust gas, in kilograms per cubic metre (cf. Table 3);
e
c is the background concentration of the tracer gas in the intake air, in parts per million (microlitres per
a
litre).
The background concentration of the tracer gas (c ) may be determined by averaging the background
a
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 (c ) at
mix,i
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 in
accordance with 6.3.8.
5.4.6 Air flow and air-to-fuel ratio measurement method
This 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:
1
qq=× 1+ (6)
miew, maw,i
A/F × λ
st i
with
αε
138,0×+βγ− +
AF/ = (7)
st
12,011×+βα1,007 94× + 15,999 4×ε+ 14,006 7×δ+ 32,065×γ
−4
21××c 0
CO
1 −
−4
cc××10 αε3,5 δ
−4 −4
CO CO2
β×−100 −cc× 10 + × −− × +c × 10
HC ()CO2 CO
−4
24 22
c × 10
CO
1 +
3,5 × c
CO2
λ = (8)
i
αε
−−44
4,764×+βγ− + ×cc+ × 10 +c × 10
()CO2 CO HC
where
A/F is the stoichiometric air-to-fuel ratio, in kilograms;
st
λ is the excess air ratio;
c is the dry CO concentration, in percent by volume;
CO2 2
c is the dry CO concentration, in parts per million (microlitres per litre);
CO
c is the HC concentration, in parts per million (microlitres per litre).
HC
NOTE β can be 1 for fuels containing carbon and 0 for hydrogen fuel.
The air flow meter shall meet the accuracy specifications of 5.3, the CO analyser used shall meet those of 6.1,
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 6.2.9.
5.5 Determination of gaseous components
5.5.1 General
The gaseous components emitted by the engine submitted for testing shall be measured in accordance with
clause 6. They shall be determined in the raw exhaust gas. Optionally, they may be determined in the diluted
exhaust gas of a fractional sampling type partial-flow dilution system used for particulate determination, in
accordance with 7.2.2. Data evaluation and calculation procedures given in 5.5.3 and 5.5.4 refer to raw emissions
measurement only. If, optionally, the diluted emissions measurement is used, the data evaluation and calculation
procedures shall be agreed by the parties involved.
5.5.2 Sampling for gaseous emissions
The gaseous emissions sampling probes shall 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, but sufficiently close to the engine to
ensure an exhaust gas temperature of at least 343 K (70 °C) 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 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 “vee” engine configuration, it is
recommended that the manifolds be combined upstream of the sampling probe. If this is not practical, it is
permissible to acquire a sample from the group with the highest CO emission. Other methods which have been
shown to correlate with these procedures may be used. For exhaust emission calculation, the total exhaust mass
flow shall be used.
If the engine is equipped with an exhaust after-treatment system, the exhaust sample shall be taken downstream of
the exhaust after-treatment system.
5.5.3 Data evaluation
For the evaluation of the gaseous emissions, the emission concentrations (HC, CO and NO ) and the exhaust gas
x
mass flow rate shall be recorded and stored with a sample rate of at least 2 Hz on a computer system. All other
data may be recorded with a sample rate of at least 1 Hz. For analog analysers, the response will be recorded, and
the calibration data may be applied online or offline during the data evaluation.
For calculation of the mass emission of the gaseous components, the traces of the recorded concentrations and
the trace of the exhaust gas mass flow rate shall be time-aligned by the transformation time. Therefore, the
response time of each gaseous emissions analyser and of the exhaust gas mass flow system shall be determined
in accordance with 6.3.5 and 5.4.2, respectively, and recorded.
5.5.4 Calculation of mass emission
5.5.4.1 General
The mass, expressed in grams per test, of the pollutants shall be determined by calculating the instantaneous
mass emissions from the concentrations of the pollut
...
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