# 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 2.1.3: Dry-to-wet concentration conversion

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

If the emissions are measured on a dry basis, the measured concentration c d on dry basis shall be converted to the concentration c w on a wet basis by means of equation (7-3):
c w = k w × c d
(7-3)
where:
k w dry-to-wet conversion factor [-]
c d emission concentration on a dry basis [ppm] or [% vol]
For complete combustion, the dry-to-wet conversion factor for raw exhaust gas is written as k w,a [-] and shall be calculated by means of equation (7-4):
k w,a = 1 − 1,2442 × H a + 111,19 × w H × q m f, i q m ad, i 773,4 + 1,2442 × H a + q m f, i q m ad, i × k f × 1000 1 − p r p b
(7-4)
where:
H a intake air humidity [g H2O/kg dry air]
qm f, i instantaneous fuel flow rate [kg/s]
qm ad, i instantaneous dry intake air flow rate [kg/s]
p r water pressure after cooler [kPa]
p b total barometric pressure [kPa]
w H hydrogen content of the fuel [% mass]
k f combustion additional volume [m3/kg fuel]
with:
k f = 0,055594 × w H + 0,0080021 × w N + 0,0070046 × w o
(7-5)
where:
w H hydrogen content of fuel [% mass]
w N nitrogen content of fuel [% mass]
w O oxygen content of fuel [% mass]
In equation (7-4), the ratio p r/p b may be assumed:
1 1 − p r p b = 1,008
(7-6)
For incomplete combustion (rich fuel air mixtures) and also for emission tests without direct air flow measurements, a second method of k w,a calculation is preferred:
k w,a = 1 1 + α × 0,005 × c CO2 + c CO − K w1 1 − p r p b
(7-7)
where:
c CO2 concentration of CO2 in the raw exhaust gas, on a dry basis [per cent vol]
c CO concentration of CO in the raw exhaust gas, on a dry basis [ppm]
p r water pressure after cooler [kPa]
p b total barometric pressure [kPa]
α molar to carbon hydrogen ratio [-]
k w1 intake air moisture [-]
k w1 = 1,608 × H a 1000 + 1,608 × H a
(7-8)

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Source: https://www.legislation.gov.uk/eur/2017/654/annex/VII/division/2/division/2.1/division/2.1.3 (the official version)
Page: https://openlegislation.uk/eu-regulation-2017-654/annex-VII/division-2/division-2.1/division-2.1.3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.