1 WLTP Open Issue Phase 1B Issue: Generic formula for hydrocarbon density. ACEA Informal Document WLTP rev1e

The mass of gaseous compounds emitted by the vehicle during the test shall be determined by obtaining the product of the volumetric concentration of the gas in question and the volume of the diluted exhaust gas with due regard for the following densities under the reference conditions of K and kPa: Carbon monoxide (CO) ρ = 1.25 g/l Carbon dioxide (CO 2 ) ρ = g/l Nitrogen oxides (NO x ) ρ = 2.05 g/l Nitrogen dioxide (NO 2 ) ρ = 2.05 g/l Nitrous oxide (N 2 O) ρ = g/l Page 2 Current Text of WLTP gtr

3 Hydrocarbons: for petrol (E0) (C 1 H 1.85 ) ρ = g/l for petrol (E5) (C 1 H 1.89 O ρ = g/l for diesel (B0) (C 1 H 1.86 ) ρ = g/l for diesel (B5) (C 1 H 1.86 O ) ρ = g/l for LPG (C 1 H ) ρ = g/l for NG/biomethane (CH 4 ) ρ = g/l for ethanol (E85) (C 1 H 2.74 O ) ρ = g/l The density for NMHC mass calculations shall be equal to that of total hydrocarbons at K and kPa and is fuel-dependent. Page 3 Current Text of WLTP gtr (continued…)

4 Proposal: A generic formula for the density of total hydrocarbons should be added. The ratios of H/C and O/C for reference fuels shall be taken from Annex 3. These numbers have to be added to the actual draft. The density shall be rounded to three decimal places. Rationale: The density of total hydrocarbons (HC) of different types of fuel differ due to varying H/C and O/C ratios. This approach supports the simple adaption to future reference fuels or changes to the existing ones. A generic formula in combination with the nomination of the H/C and O/C ratios in Annex 3 results in clarification and standardization of the density values. This approach can also be the base for the calculation of the fuel consumption in Annex 7.6. Page 4

5 Generic formula: ρ HC : density of total hydrocarbons [g/l] MW C : molecular weight of carbon = g/mol MW H : molecular weight of hydrogen = g/mol MW O : molecular weight of oxygen = g/mol V M : molar volume for an ideal gas at 0°C and kPa = l/mol H/C: ratio of hydrogen to carbon for a specific fuel C x H y O z O/C: ratio of oxygen to carbon for a specific fuel C x H y O z Page 5

6 40 CFR § : Density HC = The density of hydrocarbon. (A) For gasoline-fuel, diesel-fuel and methanol fuel; Density HC =16.33 g/ft 3 -carbon atom ( kg/m 3 -carbon atom), assuming an average carbon to hydrogen ratio of 1:1.85, at 68 °F (20 °C) and 760 mm Hg (101.3 kPa) pressure. (B) For natural gas and liquefied petroleum gas-fuel; Density HC = x ( H/C x1.008) g/ft 3 -carbon atom; x ( H/C x 1.008) kg/m 3 -carbon atom), where H/C is the hydrogen to carbon ratio of the hydrocarbon components of the test fuel, at 68 °F (20 °C) and 760 mm Hg (101.3 kPa) pressure. Page 6

7 40 CFR § : Density HC = The density of hydrocarbon. (A) For gasoline-fuel, diesel-fuel and methanol fuel; Density HC =16.33 g/ft 3 -carbon atom ( kg/m 3 -carbon atom), assuming an average carbon to hydrogen ratio of 1:1.85, at 68 °F (20 °C) and 760 mm Hg (101.3 kPa) pressure. (B) For natural gas and liquefied petroleum gas-fuel; Density HC = x ( H/C x1.008) g/ft 3 -carbon atom; x ( H/C x 1.008) kg/m 3 -carbon atom), where H/C is the hydrogen to carbon ratio of the hydrocarbon components of the test fuel, at 68 °F (20 °C) and 760 mm Hg (101.3 kPa) pressure. Page 7

8 Generic formula with physical constants: Example petrol E(5): C 1 H 1.89 O Page 8