WLTP-06-18-rev1e
WLTP
Open Issue Phase 1B
Issue: Generic formula for hydrocarbon density
ACEA Informal Document 04.03.2014
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Current Text of WLTP gtr
3.1.2. 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 273.15 K and 101.325 kPa:
Carbon monoxide (CO)
ρ = 1.25 g/l
Carbon dioxide (CO2)
ρ = 1.964 g/l
Nitrogen oxides (NOx)
ρ = 2.05 g/l
Nitrogen dioxide (NO2)
ρ = 2.05 g/l
Nitrous oxide (N2O) ρ = 1.964 g/l
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Current Text of WLTP gtr
(continued…)
Hydrocarbons:
for petrol (E0) (C1H1.85)
for petrol (E5) (C1H1.89O0.016
ρ = 0.619 g/l
ρ = 0.631 g/l
for diesel (B0) (C1H1.86)
ρ = 0.619 g/l
for diesel (B5) (C1H1.86O0.005)
ρ = 0.622 g/l
for LPG (C1H2.525)
for NG/biomethane (CH4)
ρ = 0.649 g/l
ρ = 0.714 g/l
for ethanol (E85) (C1H2.74O0.385) ρ = 0.932 g/l
The density for NMHC mass calculations shall be equal to that of total
hydrocarbons at 273.15 K and 101.325 kPa and is fuel-dependent.
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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.
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Generic formula:
𝛒𝐇𝐂 =
𝐌𝐖𝐂
𝐠
𝐠
𝐠
𝐇
𝐎
+ × 𝐌𝐖𝐇
+ × 𝐌𝐖𝐎 [
]
𝐂
𝐂
𝐦𝐨𝐥
𝐦𝐨𝐥
𝐦𝐨𝐥
𝐥
𝐕𝐌 [
]
𝐦𝐨𝐥
ρHC: density of total hydrocarbons [g/l]
MWC: molecular weight of carbon = 12.011 g/mol
MWH: molecular weight of hydrogen = 1.008 g/mol
MWO: molecular weight of oxygen = 15.999 g/mol
VM: molar volume for an ideal gas at 0°C and 101.325 kPa = 22.413 l/mol
H/C: ratio of hydrogen to carbon for a specific fuel CxHyOz
O/C: ratio of oxygen to carbon for a specific fuel CxHyOz
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40 CFR §86.144-94:
DensityHC = The density of hydrocarbon.
(A) For gasoline-fuel, diesel-fuel and methanol fuel;
DensityHC=16.33 g/ft3-carbon atom (0.5768 kg/m3-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;
DensityHC = 1.1771 x (12.011+H/C x1.008) g/ft3-carbon atom; 0.04157 x
(12.011 + H/C x 1.008) kg/m3-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.
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40 CFR §86.144-94:
DensityHC = The density of hydrocarbon.
(A) For gasoline-fuel, diesel-fuel and methanol fuel;
DensityHC=16.33 g/ft3-carbon atom (0.5768 kg/m3-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;
DensityHC = 1.1771 x (12.011+H/C x1.008) g/ft3-carbon atom; 0.04157 x
(12.011 + H/C x 1.008) kg/m3-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.
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Generic formula with physical constants:
𝛒𝐇𝐂 =
𝟏𝟐. 𝟎𝟏𝟏 +
𝐇
𝐎
× 𝟏. 𝟎𝟎𝟖 + × 𝟏𝟓. 𝟗𝟗𝟗
𝐂
𝐂
𝐠/𝐥
𝟐𝟐. 𝟒𝟏𝟑
Example petrol E(5): C1H1.89O0.016
𝛒𝐇𝐂
𝟏𝟐. 𝟎𝟏𝟏 + 𝟏. 𝟖𝟗 × 𝟏. 𝟎𝟎𝟖 + 𝟎. 𝟎𝟏𝟔 × 𝟏𝟓. 𝟗𝟗𝟗
=
𝐠/𝐥
𝟐𝟐. 𝟒𝟏𝟑
= 𝟎. 𝟔𝟑𝟐 𝐠/𝐥
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