Appendix 2

United Kingdom

Emission test procedure requirements for dual-fuel engines

General

This point defines the additional requirements and exceptions of this Annex to enable emission testing of dual-fuel engines independent whether these emissions are solely exhaust emissions or also crankcase emissions added to the exhaust emissions according to point 6.10 of Annex VI. In the case that no additional requirement or exception is listed, the requirements of this Regulation shall apply to dual-fuel engines in the same way as they apply to any other approved engine types or engine families under Regulation (EU) 2016/1628.

Emission testing of a dual-fuel engine is complicated by the fact that the fuel used by the engine can vary between pure liquid fuel and a combination of mainly gaseous fuel with only a small amount of liquid fuel as an ignition source. The ratio between the fuels used by a dual-fuel engine can also change dynamically depending of the operating condition of the engine. As a result special precautions and restrictions are necessary to enable emission testing of these engines.

Test conditions

Section 6 of Annex VI shall apply.

Test procedures

Section 7 of Annex VI shall apply.

Measurement procedures

Section 8 of Annex VI shall apply except as set out in this Appendix.

A full-flow dilution measurement procedure for dual-fuel engines is illustrated in Figure 6.6 of Annex VI (CVS system).

This measurement procedure ensures that the variation of the fuel composition during the test will mainly influence the hydrocarbon measurement results. F1This shall be compensated via one of the methods described in point 7.

Raw gaseous/partial flow measurement illustrated in Figure 6.7 of Annex VI may be used with some precautions regarding exhaust gas mass flow determination and calculation methods.

Measurement equipment

Section 9 of Annex VI shall apply.

Particle number emissions measurement

Appendix 1 of Annex VI shall apply.

Emission calculation

The emission calculation shall be performed according to Annex VII except as set out in this section. The additional requirements set out in point 7.1 shall apply for mass-based calculations and the additional requirements set out in point 7.2 shall apply for molar-based calculations.

The emission calculation requires knowledge of the composition of the fuels being used. When a gaseous fuel is supplied with a certificate confirming the properties of the fuel (e.g. gas from bottles) it is acceptable to use the composition specified by the supplier. Where the composition is not available (e.g. pipeline fuel) the fuel composition shall be analysed at least prior to and after the engine emission test is conducted. More frequent analysis shall be permitted and the results used in the calculation.

Where the gas energy ratio (GER) is used it shall be consistent with the definition in Article 3(2) of Regulation (EU) 2016/1628 and the specific provisions on total hydrocarbon (HC) limits for fully and partially gaseous-fuelled engines in Annex II of that Regulation. The average value of GER over the cycle shall be calculated by one of the following methods:

(a)

For hot-start NRTC and RMC NRSC by dividing the sum of the GER at each measurement point by the number of measurement points;
(b)

For discrete-mode NRSC by multiplying the average GER for each test mode by the corresponding weighting factor for that mode and calculating the sum for all modes. The weighting factors shall be taken from Appendix 1 of Annex XVII for the applicable cycle.

7.1.

Mass-based emission calculation

Section 2 of Annex VII shall apply except as set out in this section.

7.1.1.

Dry/wet correction

7.1.1.1.

Raw exhaust gas

Equations (7-3) and (7-4) of Annex VII shall be used to calculate the dry/wet correction.

The fuel specific parameters shall be determined in accordance with point 7.1.5.

7.1.1.2.

Diluted exhaust gas

Equation (7-3) with either equation (7-25) or (7-26) of Annex VII shall be used to calculate the wet/dry correction.

The molar hydrogen ratio α of the combination of the two fuels shall be used for the dry/wet correction. This molar hydrogen ratio shall be calculated from the fuel consumption measurement values of both fuels in accordance with point 7.1.5.

7.1.2.

NO_x correction for humidity

The NO_x humidity correction for compression ignition engines as specified in equation (7-9) of Annex VII shall be used.

7.1.3.

Partial flow dilution (PFS) and raw gaseous measurement

7.1.3.1.

Determination of exhaust gas mass flow

The exhaust gas mass flow shall be determined using a raw exhaust flow meter as described in point 9.4.5.3 of Annex VI.

Alternatively the airflow and air to fuel ratio measurement method according to equations (7-17) to (7-19) of Annex VII may be used only if α, γ, δ and ε values are determined according to point 7.1.5.3. The use of a zirconia-type sensor to determine the air fuel ratio is not allowed.

In the case of testing engines subject to steady-state test cycles only the exhaust gas mass flow may be determined by the air and fuel measurement method in accordance with equation (7-15) of Annex VII.

7.1.3.2.

Determination of the gaseous components

Point 2.1 of Annex VII shall apply except as set out in this section.

The possible variation of fuel composition will influence all the u_gas factors and molar component ratios used in the emission calculations. One of the following approaches shall be used to determine u_gas factors and molar component ratios at the choice of the manufacturer.

(a)

The exact equations in point 2.1.5.2 or 2.2.3 of Annex VII shall be applied to calculate instantaneous values of u_gas using the instantaneous proportions of liquid and gaseous fuel (determined from instantaneous fuel consumption measurements or calculations) and instantaneous molar component ratios determined in accordance with point 7.1.5; or,
(b)
When the mass-based calculation in section 2 of Annex VII is used for the specific case of a dual-fuel engine operated on gas and diesel fuel, tabulated values may be used for the molar component ratios and u_gas values. These tabulated values shall be applied as follows:
1. (i)
  
  For engines operated on the applicable test cycle with an average gas energy ratio greater than or equal to 90 % (GER ≥ 0,9) the required values shall be those for the gaseous fuel taken from Tables 7.1 or 7.2 of Annex VII.
2. (ii)
  
  For engines operated on the applicable test cycle with an average gas energy ratio between 10 % and 90 % (0,1 < GER < 0,9) the required values shall be assumed to be represented by those for a mixture of 50 % gaseous fuel and 50 % diesel fuel taken from Tables 8.1 and 8.2.
3. (iii)
  
  For engines operated on the applicable test cycle with an average gas energy ratio less than or equal to 10 % (GER ≤ 0,1) the required values shall be those for diesel fuel taken from taken from Tables 7.1 or 7.2 of Annex VII.
4. (iv)
  
  For the calculation of HC emissions the u_gas value of the gaseous fuel shall be used in all cases irrespective of the average gas energy ratio (GER).

Table 8.1

Molar component ratios for a mixture of 50 % gaseous fuel and 50 % diesel fuel (mass %)

Gaseous fuel	α	δ	ε
CH₄	2,8681	0	0,0040
G_R	2,7676	0	0,0040
G₂₃	2,7986	0,0703	0,0043
G₂₅	2,7377	0,1319	0,0045
Propane	2,2633	0	0,0039
Butane	2,1837	0	0,0038
LPG	2,1957	0	0,0038
LPG Fuel A	2,1740	0	0,0038
LPG Fuel B	2,2402	0	0,0039

7.1.3.2.1.

Mass per test of a gaseous emission

In the case that the exact equations are applied to calculate instantaneous values of u _gas in accordance with paragraph 7.1.3.2(a) then, when calculating the mass per test of a gaseous emission for transient (NRTC and LSI-NRTC) test cycles and RMC, u _gas shall be included in the summation in equation (7-2) of point 2.1.2 of Annex VII by means of equation (8-1):

m_{gas} = \frac{1}{f} \times k_{h} \times k \times \sum_{N}^{i = 1} (u_{gas, i} \times q_{mew, i} \times c_{gas, i})

(8-1)

Where:

u _gas, _i

is the instantaneous value of u_gas

The remaining terms of the equation are as set out in point 2.1.2 of Annex VII.

Table 8.2

Raw exhaust gas u gas values and component densities for a mixture of 50 % gaseous fuel and 50 % diesel fuel (mass %)

Gaseous fuel	Gas
Depending on fuel.
At λ = 2, dry air, 273 K, 101,3 kPa.
u accurate within 0,2 % for mass composition of: C = 58 – 76 %; H = 19 – 25 %; N = 0 – 14 % (CH₄, G₂₀, G₂₃, and G₂₅).
NMHC on the basis of CH_2,93 (for total HC the u _gas coefficient of CH₄ shall be used).
u accurate within 0,2 % for mass composition of: C₃ = 27 – 90 %; C4 = 10 – 73 % (LPG Fuels A and B)
	ρ _e	NO_x	CO	HC	CO₂	O₂	CH₄
				ρ _{gas [kg/m} ³ _]
		2,053	1,250	^f1	1,9636	1,4277	0,716
				u _gas ^f2
CNG/LNG^f3	1,2786	0,001606	0,000978	0,000528^f4	0,001536	0,001117	0,000560
Propane	1,2869	0,001596	0,000972	0,000510	0,001527	0,001110	0,000556
Butane	1,2883	0,001594	0,000971	0,000503	0,001525	0,001109	0,000556
LPG^f5	1,2881	0,001594	0,000971	0,000506	0,001525	0,001109	0,000556

7.1.3.3.

Particulate determination

For the determination of particulate emissions with the partial dilution measurement method the calculation shall be performed according to the equations in point 2.3 of Annex VII.

The requirements of point 8.2.1.2 of Annex VI shall apply for controlling the dilution ratio. In particular, if the combined transformation time of the exhaust gas flow measurement and the partial flow system exceeds 0,3 s, look-ahead control based on a pre-recorded test run shall be used. In this case, the combined rise time shall be ≤ 1 s and the combined delay time ≤ 10 s. Except in the case that the exhaust gas mass flow is measured directly the determination of exhaust gas mass flow shall use values of α, γ, δ and ε determined in accordance with point 7.1.5.3.

The quality check according to point 8.2.1.2 of Annex VI shall be performed for each measurement.

7.1.3.4.

Additional requirements regarding the exhaust gas mass flow meter

The flow meter referred to in points 9.4.5.3 and 9.4.5.4 of Annex VI shall not be sensitive to the changes in exhaust gas composition and density. The small errors of e.g. pitot tube or orifice-type of measurement (equivalent with the square root of the exhaust gas density) may be neglected.

7.1.4.

Full flow dilution measurement (CVS)

Point 2.2 of Annex VII shall apply except as set out in this section.

The possible variation of the fuel composition will mainly influence the tabulated hydrocarbon u_gas value. The exact equations shall be applied for the calculation of the hydrocarbon emissions using the molar component ratios determined from the fuel consumption measurements of both fuels according to point 7.1.5.

7.1.4.1.

Determination of the background corrected concentrations

To determine the stoichiometric factor, the molar hydrogen ratio α of the fuel shall be calculated as the average molar hydrogen ratio of the fuel mix during the test according to point 7.1.5.3.

Alternatively the F_s value of the gaseous fuel may be used in equation (7-28) of Annex VII.

7.1.5.

Determination of molar component ratios

7.1.5.1.

General

This section shall be used for the determination of molar component ratios when the fuel mix is known (exact method).

7.1.5.2.

Calculation of the fuel mixture components

Equations (8-2) to (8-7) shall be used to calculate the elemental composition of the fuel mixture:

q _mf = q _mf1 + q _mf2	(8-2)
$w_{H} = \frac{w_{H1} \times q_{m f1} + w_{H2} \times q_{m f2}}{q_{m f1} + q_{m f2}}$	(8-3)
$w_{C} = \frac{w_{C1} \times q_{m f1} + w_{C2} \times q_{m f2}}{q_{m f1} + q_{m f2}}$	(8-4)
$w_{S} = \frac{w_{S1} \times q_{m f1} + w_{S2} \times q_{m f2}}{q_{m f1} + q_{m f2}}$	(8-5)
$w_{N} = \frac{w_{N1} \times q_{m f1} + w_{N2} \times q_{m f2}}{q_{m f1} + q_{m f2}}$	(8-6)
$w_{O} = \frac{w_{O1} \times q_{m f1} + w_{O2} \times q_{m f2}}{q_{m f1} + q_{m f2}}$	(8-7)

where:

q _m _f1

is the fuel mass flow rate of fuel 1 [kg/s]

q _m _f2

is the fuel mass flow rate of fuel 2 [kg/s]

w _H

is the hydrogen content of fuel [% mass]

w _C

is the carbon content of fuel [% mass]

w _S

is the sulphur content of fuel [% mass]

w _N

is the nitrogen content of fuel [% mass]

w _O

is the oxygen content of fuel [% mass]

F27.1.5.3.

Calculation of the molar ratios of H, C, S, N and O related to C for the fuel mixture

The calculation of the atomic ratios (especially the H/C-ratio α) is given in Annex VII by means of equations (8-8) to (8-11):

$α = 11,9164 \times \frac{w_{H}}{w_{C}}$	(8-8)
$γ = 0,37464 \times \frac{w_{S}}{w_{C}}$	(8-9)
$δ = 0,85752 \times \frac{w_{N}}{w_{C}}$	(8-10)
$ε = 0,75072 \times \frac{w_{O}}{w_{C}}$	(8-11)

where:

w _H

is the hydrogen content of fuel, mass fraction [g/g] or [% mass]

w _C

is the carbon content of fuel, mass fraction [g/g] or [% mass]

w _S

is the sulphur content of fuel, mass fraction [g/g] or [% mass]

w _N

is the nitrogen content of fuel, mass fraction [g/g] or [% mass]

w _O

is the oxygen content of fuel, mass fraction [g/g] or [% mass]

is the molar hydrogen ratio (H/C)

is the molar sulphur ratio (S/C)

is the molar nitrogen ratio (N/C)

is the molar oxygen ratio (O/C)

referring to a fuel CΗ αΟεΝδ S γ

7.2.

Molar-based emission calculation

Annex VII section 3 shall apply except as set out in this section.

7.2.1.

NO_x correction for humidity

Equation (7-102) of Annex VII (correction for compression ignition engines) shall be used.

7.2.2.

Determination of exhaust gas mass flow when not using a raw exhaust flow meter

Equation (7-112) of Annex VII (molar flow rate calculation based on intake air) shall be used. Equation (7-113) of Annex VII (molar flow rate calculation based on fuel mass flow rate) may alternatively be used only when conducting an NRSC test.

7.2.3.

Molar component ratios for determination of the gaseous components

The exact approach shall be used to determine the molar component ratios using the instantaneous proportions of liquid and gaseous fuel determined from instantaneous fuel consumption measurements or calculations. The instantaneous molar component ratios shall be input in the equations (7-88), (7-90), and (7-91) of Annex VII for the continuous chemical balance.

The determination of the ratios shall be either performed according to point 7.2.3.1 or point 7.1.5.3.

Gaseous fuels, either blended or sourced from a land line, may contain significant amounts of inert constituents such as CO₂ and N₂. The manufacturer shall either include these constituents in the atomic ratio calculations described in point 7.2.3.1 or point 7.1.5.3 as applicable, or, alternatively, the manufacturer shall exclude the inert constituents from the atomic ratios and allocate them appropriately to the chemical balance intake air parameters x _O2int, x _CO2int, and x _H2Oint in point 3.4.3 of Annex VII.

7.2.3.1.

Determination of molar component ratios

Instantaneous molar component ratios of the number of hydrogen, oxygen, sulphur, and nitrogen atoms to carbons atoms in the mixed fuel for the dual-fuel engines may be calculated by means of equations (8-12) to (8-15):

$α (t) = \frac{\frac{ṁ_{liquid} (t) \times w_{H,liquid}}{M_{H}} + \frac{ṁ_{gas} (t) \times w_{H,gas}}{M_{H}}}{\frac{ṁ_{liquid} (t) \times w_{C,liquid}}{M_{C}} + \frac{ṁ_{gas} (t) \times w_{C,gas}}{M_{C}}} = \frac{M_{C} \times [(ṁ_{liquid} (t) \times w_{H,liquid}) + (ṁ_{gas} (t) \times w_{H,gas})]}{M_{H} \times [(ṁ_{liquid} (t) \times w_{C,liquid}) + (ṁ_{gas} (t) \times w_{C,gas})]}$	(8-12)
$β (t) = \frac{\frac{ṁ_{liquid} (t) \times w_{O,liquid}}{M_{O}} + \frac{ṁ_{gas} (t) \times w_{O,gas}}{M_{O}}}{\frac{ṁ_{liquid} (t) \times w_{C,liquid}}{M_{C}} + \frac{ṁ_{gas} (t) \times w_{C,gas}}{M_{C}}} = \frac{M_{C} \times [(ṁ_{liquid} (t) \times w_{O,liquid}) + (ṁ_{gas} (t) \times w_{O,gas})]}{M_{O} \times [(ṁ_{liquid} (t) \times w_{C,liquid}) + (ṁ_{gas} (t) \times w_{C,gas})]}$	(8-13)
$γ (t) = \frac{\frac{ṁ_{liquid} (t) \times w_{S,liquid}}{M_{S}} + \frac{ṁ_{gas} (t) \times w_{S,gas}}{M_{S}}}{\frac{ṁ_{liquid} (t) \times w_{C,liquid}}{M_{C}} + \frac{ṁ_{gas} (t) \times w_{C,gas}}{M_{C}}} = \frac{M_{C} \times [(ṁ_{liquid} (t) \times w_{S,liquid}) + (ṁ_{gas} (t) \times w_{S,gas})]}{M_{S} \times [(ṁ_{liquid} (t) \times w_{C,liquid}) + (ṁ_{gas} (t) \times w_{C,gas})]}$	(8-14)
$δ (t) = \frac{\frac{ṁ_{liquid} (t) \times w_{N,liquid}}{M_{N}} + \frac{ṁ_{gas} (t) \times w_{N,gas}}{M_{N}}}{\frac{ṁ_{liquid} (t) \times w_{C,liquid}}{M_{C}} + \frac{ṁ_{gas} (t) \times w_{C,gas}}{M_{C}}} = \frac{M_{C} \times [(ṁ_{liquid} (t) \times w_{N,liquid}) + (ṁ_{gas} (t) \times w_{N,gas})]}{M_{N} \times [(ṁ_{liquid} (t) \times w_{C,liquid}) + (ṁ_{gas} (t) \times w_{C,gas})]}$	(8-15)

Where:

w _i, _fuel

the mass fraction of the element of interest, C, H, O, S, or N, of liquid or gaseous fuel;

ṁ_liquid (t)

the instantaneous mass flow rate of the liquid fuel at time t, [kg/hr];

ṁ_gas (t)

the instantaneous mass flow rate of the gaseous fuel at time t, [kg/hr];

In cases where exhaust gas mass flow rate is calculated based on the mixed fuel rate then w _C in equation (7-113) of Annex VII shall be calculated by means of equation (8-16):

w_{C} = \frac{ṁ_{liquid} \times w_{C,liquid} + ṁ_{gas} \times w_{C,gas}}{ṁ_{liquid} + ṁ_{gas}}

(8-16)

Where:

w _C

the mass fraction of the carbon in the diesel or gaseous fuel;

ṁ_liquid

the mass flow rate of the liquid fuel, [kg/hr];

ṁ_gas

the mass flow rate of the gaseous fuel, [kg/hr].

7.3.

CO₂ determination

Annex VII shall apply except when the engine is tested on transient (NRTC and LSI-NRTC) test cycles or RMC using raw gas sampling.

7.3.1

CO₂ determination when testing on transient (NRTC and LSI-NRTC) test cycles or RMC using raw gas sampling

Calculation of CO₂ emissions from measurement of CO₂ in the exhaust gas in accordance with Annex VII shall not apply. Instead the following provisions shall apply:

The measured test-averaged fuel consumption shall be determined from the sum of the instantaneous values over the cycle and shall be used as the base for calculating the test averaged CO₂ emissions.

The mass of each fuel consumed shall be used to determine, in accordance with section 7.1.5, the molar hydrogen ratio and the mass fractions of the fuel mix in the test.

The total corrected fuel mass of both fuels m _fuel,corr [g/test] and CO₂ mass emission coming from the fuel m _{CO2, fuel} [g/test] shall be determined by means of equations (8-17) and (8-18).

$m_{fuel,corr} = m_{fuel} - (m_{THC} + \frac{A_{C} + a \times A_{H}}{M_{CO}} {xm}_{CO} + \frac{W_{GAM} + W_{DEL} + W_{EPS}}{100} \times m_{fuel})$	(8-17)
$m_{{CO}_{2} fuel} = \frac{M_{{CO}_{2}}}{A_{C} + a + A_{H}} \times m_{fuel,corr}$	(8-18)

Where:

m _fuel

total fuel mass of both fuels [g/test]

m _THC

mass of total hydrocarbon emissions in the exhaust gas [g/test]

m _CO

mass of carbon monoxide emissions in the exhaust gas [g/test]

w _GAM

sulphur content of the fuels [per cent mass]

w _DEL

nitrogen content of the fuels [per cent mass]

w _EPS

is the oxygen content of the fuels [per cent mass]

is the molar hydrogen ratio of the fuels (H/C) [-]

A _C

is the atomic mass of Carbon: 12,011 [g/mol]

A _H

is the atomic mass of Hydrogen: 1,0079 [g/mol]

M _CO

is the molecular mass of Carbon monoxide: 28,011 [g/mol]

M _CO2

is the molecular mass of Carbon dioxide: 44,01 [g/mol]

The CO₂ emission resulting from urea m _CO2,urea [g/test] shall be calculated by means of equation (8-19):

m_{{CO}_{2},urea} = \frac{c_{urea}}{100} \times \frac{M_{CO2}}{M_{CO {({NH}_{2})}_{2}}} \times m_{urea}

(8-19)

Where:

c _urea

urea concentration [per cent]

m _urea

total urea mass consumption [g/test]

M _CO(NH2)2

Molecular mass of urea: 60,056 [g/mol]

Then the total CO₂ emission m _CO2 [g/test] shall be calculated by means of equation (8-20):

m_CO2 = m_CO2,fuel + m_CO2,urea

(8-20)

The total CO₂ emission calculated by means of equation (8-20) shall be used in the calculation of brake specific CO₂ emissions, e_CO2 [g/kWh] in section 2.4.1.1 or 3.8.1.1 of Annex VII. Where applicable, the correction for CO₂ in the exhaust gas arising from CO₂ in the gaseous fuel shall be performed in accordance with Appendix 3 to Annex IX.

Annotations

Textual amendments

F1: Substituted by Commission Delegated Regulation (EU) 2018/989 of 18 May 2018 amending and correcting Delegated Regulation (EU) 2017/654 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 (Text with EEA relevance).
F2: Inserted by Commission Delegated Regulation (EU) 2018/989 of 18 May 2018 amending and correcting Delegated Regulation (EU) 2017/654 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 (Text with EEA relevance).

Footnotes

f1: Depending on fuel.
f2: At λ = 2, dry air, 273 K, 101,3 kPa.
f3: u accurate within 0,2 % for mass composition of: C = 58 – 76 %; H = 19 – 25 %; N = 0 – 14 % (CH₄, G₂₀, G₂₃, and G₂₅).
f4: NMHC on the basis of CH_2,93 (for total HC the u _gas coefficient of CH₄ shall be used).
f5: u accurate within 0,2 % for mass composition of: C₃ = 27 – 90 %; C4 = 10 – 73 % (LPG Fuels A and B)