# 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, Division 3.6.3: Exhaust gas molar flow rate

Extent: E+W+S+N.I.

(a) Calculation via chemical balance;
The molar flow rate ṅ exh [mol/s] can be calculated based on fuel mass flow rate ṁ fuel by means of equation (7-113):
ṅ exh = ṁ fuel × w C × 1 + x H2Oexhdry M C × x Ccombdry
(see equation 7-113)
Where:
ṅ exh raw exhaust gas molar flow rate from which emissions are measured
ṁ fuel fuel flow rate including humidity in intake air [g/s]
w C carbon mass fraction for the given fuel [g/g]
x H2Oexhdry amount of H2O per dry mole of measured flow [mol/mol]
M C molecular mass of carbon 12,0107 g/mol
x Ccombdry amount of carbon from fuel in the exhaust gas per mole of dry exhaust gas [mol/mol]
(b) Measurement
The exhaust gas molar flow rate may be measured by means of three systems:
(i) PDP molar flow rate. Based upon the speed at which the Positive Displacement Pump (PDP) operates for a test interval, the corresponding slope a 1 , and intercept, a 0 [-], as calculated with the calibration procedure set out in point 3.9.2, shall be used to calculate molar flow rate ṅ [mol/s] by means of equation (7-117):
ṅ = ƒ n,PDP × p in × V rev R × T in
(7-117)
with:
V rev = a 1 f n,PDP × p out − p in p in + a 0
(7-118)
where:
a 1 calibration coefficient [m3/s]
a 0 calibration coefficient [m3/rev]
p in, p out inlet/outlet pressure [Pa]
R molar gas constant [J/(mol · K)]
T in inlet temperature [K]
V rev PDP pumped volume [m3/rev]
f n.,PDP PDP speed [rev/s]
(ii) SSV molar flow rate. Based on the C d versus R e # equation determined in accordance with point 3.9.4, the Sub-Sonic Venturi (SSV) molar flow rate during an emission test ṅ [mol/s] shall be calculated by means of equation (7-119):
ṅ = C d × C f × A t × p in Z × M mix × R × T in
(7-119)
Where:
p in inlet pressure [Pa]
A t Venturi throat cross-sectional area [m2]
R molar gas constant [J/(mol · K)]
T in inlet temperature [K]
Z compressibility factor
M mix molar mass of diluted exhaust gas [kg/mol]
C d discharge coefficient of the SSV [-]
C f flow coefficient of the SSV [-]
(iii) CFV molar flow rate. To calculate the molar flow rate through one venturi or one combination of venturis, its respective mean C d and other constants, determined in accordance with point 3.9.5, shall be used. The calculation of its molar flow rate ṅ [mol/s] during an emission test shall be calculated by means of equation (7-120):
ṅ = C d × C f × A t × p in Z × M mix × R × T in
(7-120)
Where:
p in inlet pressure [Pa]
A t Venturi throat cross-sectional area [m2]
R molar gas constant [J/(mol · K)]
T in inlet temperature [K]
Z compressibility factor
M mix molar mass of diluted exhaust gas [kg/mol]
C d discharge coefficient of the CFV [-]
C f flow coefficient of the CFV [-]

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Source: https://www.legislation.gov.uk/eur/2017/654/annex/VII/division/3/division/3.6/division/3.6.3 (the official version)
Page: https://openlegislation.uk/eu-regulation-2017-654/annex-VII/division-3/division-3.6/division-3.6.3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.