Appendix 4 F1

United Kingdom

Determination of emissions

INTRODUCTION

This appendix describes the procedure to determine the instantaneous mass and particle number emissions [g/s; #/s] that shall be used for the subsequent evaluation of a test trip and the calculation of the final emission result as described in Appendices 5 and 6.

SYMBOLS

per cent

smaller than

#/s

number per second

molar hydrogen ratio (H/C)

molar carbon ratio (C/C)

molar sulphur ratio (S/C)

molar nitrogen ratio (N/C)

Δ t _t,i

transformation time t of the analyser [s]

Δ t _t,m

transformation time t of the exhaust mass flow meter [s]

molar oxygen ratio (O/C)

r _e

density of the exhaust

r _gas

density of the exhaust component ‘ gas ’

excess air ratio

l _i

instantaneous excess air ratio

A/F _st

stoichiometric air-to-fuel ratio [kg/kg]

°C

degrees centigrade

c _CH4

concentration of methane

c _CO

dry CO concentration [%]

c _CO2

dry CO ₂ concentration [%]

c _dry

dry concentration of a pollutant in ppm or per cent volume

c _gas,i

instantaneous concentration of the exhaust component ‘ gas ’ [ppm]

c _HCw

wet HC concentration [ppm]

c _HC(w/ NMC ₎

HC concentration with CH ₄ or C ₂ H ₆ flowing through the NMC [ppmC ₁ ]

c _HC(w/oNMC)

HC concentration with CH ₄ or C ₂ H ₆ bypassing the NMC [ppmC ₁ ]

c _i,c

time-corrected concentration of component i [ppm]

c _i,r

concentration of component i [ppm] in the exhaust

c _NMHC

concentration of non-methane hydrocarbons

c _wet

wet concentration of a pollutant in ppm or per cent volume

E _E

ethane efficiency

E _M

methane efficiency

gramme

g/s

gramme per second

H _a

intake air humidity [g water per kg dry air]

number of the measurement

kilogram

kg/h

kilogramme per hour

kg/s

kilogramme per second

k _w

dry-wet correction factor

metre

m _gas,i

mass of the exhaust component ‘ gas ’ [g/s]

q _m _aw,i

instantaneous intake air mass flow rate [kg/s]

q _m,c

time-corrected exhaust mass flow rate [kg/s]

q _m _ew,i

instantaneous exhaust mass flow rate [kg/s]

q _m _f,i

instantaneous fuel mass flow rate [kg/s]

q _m,r

raw exhaust mass flow rate [kg/s]

cross-correlation coefficient

r ²

coefficient of determination

r _h

hydrocarbon response factor

rpm

revolutions per minute

second

u _gas

u value of the exhaust component ‘gas’

TIME CORRECTION OF PARAMETERS

For the correct calculation of distance-specific emissions, the recorded traces of component concentrations, exhaust mass flow rate, vehicle speed, and other vehicle data shall be time corrected. To facilitate the time correction, data which are subject to time alignment shall be recorded either in a single data recording device or with a synchronised timestamp following point 5.1 of Appendix 1. The time correction and alignment of parameters shall be carried out by following the sequence described in points 3.1 to 3.3.

3.1.

Time correction of component concentrations

The recorded traces of all component concentrations shall be time corrected by reverse shifting according to the transformation times of the respective analysers. The transformation time of analysers shall be determined according to point 4.4 of Appendix 2:

c _i,c (t – Δt _t,i ) = c _i,r (t)

where:

c _i,c

is the time-corrected concentration of component i as function of time t

c _i,r

is the raw concentration of component i as function of time t

Δt _t,i

is the transformation time t of the analyser measuring component i.

3.2.

Time correction of exhaust mass flow rate

The exhaust mass flow rate measured with an exhaust flow meter shall be time corrected by reverse shifting according to the transformation time of the exhaust mass flow meter. The transformation time of the mass flow meter shall be determined according to point 4.4.9 of Appendix 2:

q _m,c (t – Δt _t,m ) = q _m _,r (t)

where:

q _m,c

is the time-corrected exhaust mass flow rate as function of time t

q _m,r

is the raw exhaust mass flow rate as function of time t

Δt _t,m

is the transformation time t of the exhaust mass flow meter.

In case the exhaust mass flow rate is determined by ECU data or a sensor, an additional transformation time shall be considered and obtained by cross-correlation between the calculated exhaust mass flow rate and the exhaust mass flow rate measured following point 4 of Appendix 3.

3.3.

Time alignment of vehicle data

Other data obtained from a sensor or the ECU shall be time-aligned by cross-correlation with suitable emission data (e.g. component concentrations).

3.3.1.

Vehicle speed from different sources

To time align vehicle speed with the exhaust mass flow rate, it is first necessary to establish one valid speed trace. In case vehicle speed is obtained from multiple sources (e.g. the GPS, a sensor or the ECU), the speed values shall be time aligned by cross-correlation.

3.3.2.

Vehicle speed with exhaust mass flow rate

Vehicle speed shall be time aligned with the exhaust mass flow rate by means of cross-correlation between the exhaust mass flow rate and the product of vehicle velocity and positive acceleration.

3.3.3.

Further signals

The time alignment of signals whose values change slowly and within a small value range, e.g. ambient temperature, can be omitted.

COLD START

The cold start period covers the first 5 minutes after initial start of the combustion engine. If the coolant temperature can be reliably determined, the cold start period ends once the coolant has reached 343 K (70 °C) for the first time but no later than 5 minutes after initial engine start. Cold start emissions shall be recorded.

EMISSION MEASUREMENTS DURING ENGINE STOP

Any instantaneous emissions or exhaust flow measurements obtained while the combustion engine is deactivated shall be recorded. In a separate step, the recorded values shall afterward be set to zero by the data post processing. The combustion engine shall be considered as deactivated if two of the following criteria apply: the recorded engine speed is < 50 rpm; the exhaust mass flow rate is measured at < 3 kg/h; the measured exhaust mass flow rate drops to < 15 % of the steady-state exhaust mass flow rate at idling.

CONSISTENCY CHECK OF VEHICLE ALTITUDE

In case well-reasoned doubts exist that a trip has been conducted above of the permissible altitude as specified in point 5.2 of Annex IIIA and in case altitude has only been measured with a GPS, the GPS altitude data shall be checked for consistency and, if necessary, corrected. The consistency of data shall be checked by comparing the latitude, longitude and altitude data obtained from the GPS with the altitude indicated by a digital terrain model or a topographic map of suitable scale. Measurements that deviate by more than 40 m from altitude depicted in the topographic map shall be manually corrected and marked.

CONSISTENCY CHECK OF GPS VEHICLE SPEED

The vehicle speed as determined by the GPS shall be checked for consistency by calculating and comparing the total trip distance with reference measurements obtained from either a sensor, the validated ECU or, alternatively, from a digital road network or topographic map. It is mandatory to correct GPS data for obvious errors, e.g. by applying a dead reckoning sensor, prior to the consistency check. The original and uncorrected data file shall be retained and any corrected data shall be marked. The corrected data shall not exceed an uninterrupted time period of 120 s or a total of 300 s. The total trip distance as calculated from the corrected GPS data shall deviate by no more than 4 % from the reference. If the GPS data do not meet these requirements and no other reliable speed source is available, the test results shall be voided.

CORRECTION OF EMISSIONS

8.1.

Dry-wet correction

If the emissions are measured on a dry basis, the measured concentrations shall be converted to a wet basis as:

c _wet = k _w · c _dry

where:

c _wet

is the wet concentration of a pollutant in ppm or per cent volume

c _dry

is the dry concentration of a pollutant in ppm or per cent volume

k _w

is the dry-wet correction factor

The following equation shall be used to calculate k _w :

$k_{w} = (\frac{1}{1 + α \times 0,005 \times (c_{{CO}_{2}} + c_{CO})}) \times 1,008$

where:

$k_{w1} = \frac{1,608 \times H_{a}}{1000 + (1,608 \times H_{a})}$

where:

H _a

is the intake air humidity [g water per kg dry air]

c _CO2

is the dry CO ₂ concentration [%]

c _CO

is the dry CO concentration [%]

is the molar hydrogen ratio.

8.2.

Correction of NOx for ambient humidity and temperature

NO _x emissions shall not be corrected for ambient temperature and humidity.

DETERMINATION OF THE INSTANTANEOUS GASEOUS EXHAUST COMPONENTS

9.1.

Introduction

The components in the raw exhaust gas shall be measured with the measurement and sampling analysers described in Appendix 2. The raw concentrations of relevant components shall be measured in accordance with Appendix 1. The data shall be time corrected and aligned in accordance with point 3.

9.2.

Calculating NMHC and CH ₄ concentrations

For methane measurement using a NMC-FID, the calculation of NMHC depends on the calibration gas/method used for the zero/span calibration adjustment. When a FID is used for THC measurement without a NMC, it shall be calibrated with propane/air or propane/N ₂ in the normal manner. For the calibration of the FID in series with a NMC, the following methods are permitted:

(a)

the calibration gas consisting of propane/air bypasses the NMC;
(b)

the calibration gas consisting of methane/air passes through the NMC.

It is strongly recommended to calibrate the methane FID with methane/air through the NMC.

In method (a), the concentrations of CH ₄ and NMHC shall be calculated as follows:

$c_{{CH}_{4}} = \frac{c_{HC (w ∕ oNMC)} \times (1 - E_{M}) - c_{HC (w ∕ NMC)}}{(E_{E} - E_{M})}$

$c_{NMHC} = \frac{c_{HC (w ∕ NMC)} - c_{HC (w ∕ oNMC)} \times (1 - E_{E})}{r_{h} \times (E_{E} - E_{M})}$

In case (b), the concentration of CH ₄ and NMHC shall be calculated as follows:

$c_{{HC}_{4}} = \frac{c_{HC (w ∕ NMC)} \times r_{h} \times (1 - E_{M}) - c_{HC (w ∕ oNMC)} \times (1 - E_{E})}{r_{h} \times (E_{E} - E_{M})}$

$c_{NMHC} = \frac{c_{HC (w ∕ oNMC)} \times (1 - E_{M}) - c_{HC (w ∕ NMC)} \times r_{h} \times (1 - E_{M})}{(E_{E} - E_{M})}$

where:

c _HC(w/oNMC)

is the HC concentration with CH ₄ or C ₂ H ₆ bypassing the NMC [ppmC ₁ ]

c _HC(w/NMC)

is the HC concentration with CH ₄ or C ₂ H ₆ flowing through the NMC [ppmC ₁ ]

r _h

is the hydrocarbon response factor as determined in point 4.3.3(b) of Appendix 2

E _M

is the methane efficiency as determined in point 4.3.4(a) of Appendix 2

E _E

is the ethane efficiency as determined in point 4.3.4(b) of Appendix 2.

If the methane FID is calibrated through the cutter (method b), then the methane conversion efficiency as determined in point 4.3.4(a) of Appendix 2 is zero. The density used for NMHC mass calculations shall be equal to that of total hydrocarbons at 273,15 K and 101,325 kPa and is fuel-dependent.

10.

DETERMINATION OF EXHAUST MASS FLOW

10.1.

Introduction

The calculation of instantaneous mass emissions according to points 11 and 12 requires determining the exhaust mass flow rate. The exhaust mass flow rate shall be determined by one of the direct measurement methods specified in point 7.2 of Appendix 2. Alternatively, it is permissible to calculate the exhaust mass flow rate as described in points 10.2 to 10.4.

10.2.

Calculation method using air mass flow rate and fuel mass flow rate

The instantaneous exhaust mass flow rate can be calculated from the air mass flow rate and the fuel mass flow rate as follows:

q _mew,i = q _maw,i + q _mf,i

where:

q _m _ew,i

is the instantaneous exhaust mass flow rate [kg/s]

q _m _aw,i

is the instantaneous intake air mass flow rate [kg/s]

q _m _f,i

is the instantaneous fuel mass flow rate [kg/s].

If the air mass flow rate and the fuel mass flow rate or the exhaust mass flow rate are determined from ECU recording, the calculated instantaneous exhaust mass flow rate shall meet the linearity requirements specified for the exhaust mass flow rate in point 3 of Appendix 2 and the validation requirements specified in point 4.3 of Appendix 3.

10.3.

Calculation method using air mass flow and air-to-fuel ratio

The instantaneous exhaust mass flow rate can be calculated from the air mass flow rate and the air-to-fuel ratio as follows:

$q_{mew,i} = q_{maw,i} \times (1 + \frac{1}{A ∕ F_{st} \times λ_{i}})$

where:

$A ∕ F_{st} = \frac{138,0 \times (1 + \frac{α}{4} - \frac{ε}{2} + γ)}{12,011 + 1,008 \times α + 15,9994 \times ε + 14,0067 \times δ + 32,0675 \times γ}$

$λ_{i} = \frac{(100 - \frac{c_{CO} \times 10^{- 4}}{2} - c_{HCw} \times 10^{- 4}) + (\frac{α}{4} \times \frac{1 - \frac{2 \times c_{CO} \times 10^{- 4}}{3,5 \times c_{{CO}_{2}}}}{1 + \frac{c_{CO} \times 10^{- 4}}{3,5 \times c_{{CO}_{2}}}} - \frac{ε}{2} - \frac{δ}{2}) \times (c_{{CO}_{2}} + c_{CO} \times 10^{- 4})}{4,764 \times (1 + \frac{α}{4} - \frac{ε}{2} + γ) \times (c_{{CO}_{2}} + c_{CO} \times 10^{- 4} + c_{HCw} \times 10^{- 4})}$

where:

q _m _aw,i

is the instantaneous intake air mass flow rate [kg/s]

A/F _st

is the stoichiometric air-to-fuel ratio [kg/kg]

l _i

is the instantaneous excess air ratio

c _CO2

is the dry CO ₂ concentration [%]

c _CO

is the dry CO concentration [ppm]

c _HCw

is the wet HC concentration [ppm]

is the molar hydrogen ratio (H/C)

is the molar carbon ratio (C/C)

is the molar sulphur ratio (S/C)

is the molar nitrogen ratio (N/C)

is the molar oxygen ratio (O/C).

Coefficients refer to a fuel C _β H _α O _ε N _δ S _γ with β = 1 for carbon-based fuels. The concentration of HC emissions is typically low and may be omitted when calculating l _i .

If the air mass flow rate and air-to-fuel ratio are determined from ECU recording, the calculated instantaneous exhaust mass flow rate shall meet the linearity requirements specified for the exhaust mass flow rate in point 3 of Appendix 2 and the validation requirements specified in point 4.3 of Appendix 3.

10.4.

Calculation method using fuel mass flow and air-to-fuel ratio

The instantaneous exhaust mass flow rate can be calculated from the fuel flow and the air-to-fuel ratio (calculated with A/F _st and l _i according to point 10.3) as follows:

q _mew,i = q _mf,i × (1 + A / F _st × λ _i )

The calculated instantaneous exhaust mass flow rate shall meet the linearity requirements specified for the exhaust gas mass flow rate in point 3 of Appendix 2 and the validation requirements specified in point 4.3 of Appendix 3.

11.

CALCULATING THE INSTANTANEOUS MASS EMISSIONS

The instantaneous mass emissions [g/s] shall be determined by multiplying the instantaneous concentration of the pollutant under consideration [ppm] with the instantaneous exhaust mass flow rate [kg/s], both corrected and aligned for the transformation time, and the respective u value of Table 1. If measured on a dry basis, the dry-wet correction according to point 8.1 shall be applied to the instantaneous component concentrations before executing any further calculations. If applicable, negative instantaneous emission values shall enter all subsequent data evaluations. All significant digits of intermediate results shall enter the calculation of the instantaneous emissions. The following equation shall be applied:

m _gas,i = u _gas · c _gas,i · q _mew,i

where:

m _gas,i

is the mass of the exhaust component ‘ gas ’ [g/s]

u _gas

is the ratio of the density of the exhaust component ‘ gas ’ and the overall density of the exhaust as listed in Table 1

c _gas,i

is the measured concentration of the exhaust component ‘ gas ’ in the exhaust [ppm]

q _m _ew,i

is the measured exhaust mass flow rate [kg/s]

gas

is the respective component

number of the measurement.

Table 1

Raw exhaust gas u values depicting the ratio between the densities of exhaust component or pollutant [kg/m ³ ] and the density of the exhaust gas [kg/m ³ ] ^f1

Fuel	ρ _e [kg/m ³ ]	Component or pollutant i
Depending on fuel.
At l = 2, dry air, 273 K, 101,3 kPa.
u values accurate within 0,2 % for mass composition of: C = 66 – 76 %; H = 22 – 25 %; N = 0 – 12 %.
NMHC on the basis of CH _2,93 (for THC the u _gas coefficient of CH ₄ shall be used).
u accurate within 0,2 % for mass composition of: C ₃ = 70 – 90 %; C ₄ = 10 – 30 %.
u _gas is a unitless parameter; the u _gas values include unit conversions to ensure that the instantaneous emissions are obtained in the specified physical unit, i.e. g/s.
		NO _x	CO	HC	CO ₂	O ₂	CH ₄
		ρ _gas [kg/m ³ ]
		2,053	1,250	^f2	1,9636	1,4277	0,716
		u _gas ^f3
Diesel (B7)	1,2943	0,001586	0,000966	0,000482	0,001517	0,001103	0,000553
Ethanol (ED95)	1,2768	0,001609	0,000980	0,000780	0,001539	0,001119	0,000561
CNG ^f4	1,2661	0,001621	0,000987	0,000528 ^f5	0,001551	0,001128	0,000565
Propane	1,2805	0,001603	0,000976	0,000512	0,001533	0,001115	0,000559
Butane	1,2832	0,001600	0,000974	0,000505	0,001530	0,001113	0,000558
LPG ^f6	1,2811	0,001602	0,000976	0,000510	0,001533	0,001115	0,000559
Petrol (E10)	1,2931	0,001587	0,000966	0,000499	0,001518	0,001104	0,000553
Ethanol (E85)	1,2797	0,001604	0,000977	0,000730	0,001534	0,001116	0,000559

12.

CALCULATING THE INSTANTANEOUS PARTICLE NUMBER EMISSIONS

This section will define future requirements for calculating instantaneous particle number emissions, once their measurement becomes mandatory.

13.

DATA REPORTING AND EXCHANGE

The data shall be exchanged between the measurement systems and the data evaluation software by a standardised reporting file as specified in point 2 of Appendix 8. Any pre-processing of data (e.g. time correction according to point 3 or the correction of the GPS vehicle speed signal according to point 7) shall be done with the control software of the measurement systems and shall be completed before the data reporting file is generated. If data are corrected or processed prior to entering the data reporting file, the original raw data shall be kept for quality assurance and control. Rounding of intermediate values is not permitted. Instead, intermediate values shall enter the calculation of instantaneous emissions [g/s; #/s] as reported by the analyser, flow-measuring instrument, sensor or the ECU.

Annotations

Textual amendments

F1: Inserted by Commission Regulation (EU) 2016/427 of 10 March 2016 amending Regulation (EC) No 692/2008 as regards emissions from light passenger and commercial vehicles (Euro 6) (Text with EEA relevance).

Footnotes

f1: u _gas is a unitless parameter; the u _gas values include unit conversions to ensure that the instantaneous emissions are obtained in the specified physical unit, i.e. g/s.
f2: Depending on fuel.
f3: At l = 2, dry air, 273 K, 101,3 kPa.
f4: u values accurate within 0,2 % for mass composition of: C = 66 – 76 %; H = 22 – 25 %; N = 0 – 12 %.
f5: NMHC on the basis of CH _2,93 (for THC the u _gas coefficient of CH ₄ shall be used).
f6: u accurate within 0,2 % for mass composition of: C ₃ = 70 – 90 %; C ₄ = 10 – 30 %.