Directive 2005/55/EC of the European Parliament and of the Council (repealed)Show full title

4. CALCULATION OF THE GASEOUS EMISSIONS

4.1. Determination of the diluted exhaust gas flow

The total diluted exhaust gas flow over the cycle (kg/test) shall be calculated from the measurement values over the cycle and the corresponding calibration data of the flow measurement device (V₀ for PDP or K_V for CFV, as determined in Annex III, Appendix 5, Section 2). The following formulae shall be applied, if the temperature of the diluted exhaust is kept constant over the cycle by using a heat exchanger (± 6 K for a PDP-CVS, ± 11 K for a CFV-CVS, see Annex V, Section 2.3).

For the PDP-CVS system:

M_TOTW = 1,293 × V₀ × N_p × (p_B – p₁) × 273 / (101,3 × T)

where:

M_TOTW

=

mass of the diluted exhaust gas on wet basis over the cycle, kg

V₀

=

volume of gas pumped per revolution under test conditions, m³/rev

N_P

=

total revolutions of pump per test

p_B

=

atmospheric pressure in the test cell, kPa

p₁

=

pressure depression below atmospheric at pump inlet, kPa

T

=

average temperature of the diluted exhaust gas at pump inlet over the cycle, K

For the CFV-CVS system:

M_TOTW = 1,293 × t × K_v × p_A / T^0,5

where:

M_TOTW

=

mass of the diluted exhaust gas on wet basis over the cycle, kg

t

=

cycle time, s

K_v

=

calibration coefficient of the critical flow venturi for standard conditions

p_A

=

absolute pressure at venturi inlet, kPa

T

=

absolute temperature at venturi inlet, K

If a system with flow compensation is used (i.e. without heat exchanger), the instantaneous mass emissions shall be calculated and integrated over the cycle. In this case, the instantaneous mass of the diluted exhaust gas shall be calculated as follows:

For the PDP-CVS system:

M_TOTW,i = 1,293 × V₀ × N_p,i × (p_B – p₁) × 273 / (101,3 × T)

where:

M_TOTW,i

=

instantaneous mass of the diluted exhaust gas on wet basis, kg

N_p,i

=

total revolutions of pump per time interval

For the CFV-CVS system:

M_TOTW,i = 1,293 × Δt_i × K_v × p_A / T^0,5

where:

M_TOTW,i

=

instantaneous mass of the diluted exhaust gas on wet basis, kg

Δt_i

=

time interval, s

If the total sample mass of particulates (M_SAM) and gaseous pollutants exceeds 0,5 % of the total CVS flow (M_TOTW), the CVS flow shall be corrected for M_SAM or the particulate sample flow shall be returned to the CVS prior to the flow measuring device (PDP or CFV).

4.2. NO_x correction for humidity

As the NO_x emission depends on ambient air conditions, the NO_x concentration shall be corrected for ambient air humidity with the factors given in the following formulae:

(a)

for diesel engines:

(b)

for gas engines:

where:

H_a

=

humidity of the intake air water per kg dry air

in which:

R_a

=

relative humidity of the intake air, %

p_a

=

saturation vapour pressure of the intake air, kPa

p_B

=

total barometric pressure, kPa

4.3. Calculation of the emission mass flow

4.3.1. Systems with constant mass flow

For systems with heat exchanger, the mass of the pollutants (g/test) shall be determined from the following equations:

• 

  [(1)]

• 

  [(2)]

• 

  [(3)]

• 

  [(4)]

• 

  [(5)]

• 

  [(6)]

• 

  [(7)]

where:

NO_{x conc}, CO_conc, HC_conc (1), NMHC_conc

=

average background corrected concentrations over the cycle from integration (mandatory for NO_x and HC) or bag measurement, ppm

M_TOTW

=

total mass of diluted exhaust gas over the cycle as determined in Section 4.1, kg

K_H,D

=

humidity correction factor for diesel engines as determined in Section 4.2

K_H,G

=

humidity correction factor for gas engines as determined in Section 4.2

Concentrations measured on a dry basis shall be converted to a wet basis in accordance with Annex III, Appendix 1, Section 4.2.

The determination of NMHC_conc depends on the method used (see Annex III, Appendix 4, Section 3.3.4). In both cases, the CH₄ concentration shall be determined and subtracted from the HC concentration as follows:

(a)

GC method

(b)

NMC method

where:

HC(wCutter)

=

HC concentration with the sample gas flowing through the NMC

HC(w/oCutter)

=

HC concentration with the sample gas bypassing the NMC

CE_M

=

methane efficiency as determined per Annex III, Appendix 5, Section 1.8.4.1

CE_E

=

ethane efficiency as determined per Annex III, Appendix 5, Section 1.8.4.2

4.3.1.1. Determination of the background corrected concentrations

The average background concentration of the gaseous pollutants in the dilution air shall be subtracted from measured concentrations to get the net concentrations of the pollutants. The average values of the background concentrations can be determined by the sample bag method or by continuous measurement with integration. The following formula shall be used.

where:

conc

=

concentration of the respective pollutant in the diluted exhaust gas, corrected by the amount of the respective pollutant contained in the dilution air, ppm

conc_e

=

concentration of the respective pollutant measured in the diluted exhaust gas, ppm

conc_d

=

concentration of the respective pollutant measured in the dilution air, ppm

DF

=

dilution factor

The dilution factor shall be calculated as follows:

(a)

for diesel and LPG fuelled gas engines

(b)

for NG-fuelled gas engines

where:

CO_{2, conce}

=

concentration of CO₂ in the diluted exhaust gas, % vol

HC_conce

=

concentration of HC in the diluted exhaust gas, ppm C1

NMHC_conce

=

concentration of NMHC in the diluted exhaust gas, ppm C1

CO_conce

=

concentration of CO in the diluted exhaust gas, ppm

F_S

=

stoichiometric factor

Concentrations measured on dry basis shall be converted to a wet basis in accordance with Annex III, Appendix 1, Section 4.2.

The stoichiometric factor shall be calculated as follows:

where:

x, y

=

fuel composition C_xH_y

Alternatively, if the fuel composition is not known, the following stoichiometric factors may be used:

F_S (diesel)

=

13,4

F_S (LPG)

=

11,6

F_S (NG)

=

9,5

4.3.2. Systems with flow compensation

For systems without heat exchanger, the mass of the pollutants (g/test) shall be determined by calculating the instantaneous mass emissions and integrating the instantaneous values over the cycle. Also, the background correction shall be applied directly to the instantaneous concentration value. The following formulae shall be applied:

• 

  [(1)]

• 

  [(2)]

• 

  [(3)]

• 

  [(4)]

• 

  [(5)]

• 

  [(6)]

• 

  [(7)]

where:

conc_e

=

concentration of the respective pollutant measured in the diluted exhaust gas, ppm

conc_d

=

concentration of the respective pollutant measured in the dilution air, ppm

M_TOTW,i

=

instantaneous mass of the diluted exhaust gas (see Section 4.1), kg

M_TOTW

=

total mass of diluted exhaust gas over the cycle (see Section 4.1), kg

K_H,D

=

humidity correction factor for diesel engines as determined in Section 4.2

K_H,G

=

humidity correction factor for gas engines as determined in Section 4.2

DF

=

dilution factor as determined in Section 4.3.1.1

4.4. Calculation of the specific emissions

The emissions (g/kWh) shall be calculated for all individual components in the following way:

(diesel and gas engines)

(diesel and gas engines)

(diesel and LPG fuelled gas engines)

(NG fuelled gas engines)

(NG fuelled gas engines)

where:

W_act

=

actual cycle work as determined in Section 3.9.2, kWh

(1)

Based on C1 equivalent.