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Commission Delegated Regulation (EU) 2017/654 of 19 December 2016 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

Type Delegated Regulation
Publication 2017-04-13
Last updated 2021-09-13
State In force
Department European Commission, GROW
Source EUR-Lex
articles 22
Reform history JSON API

3.3.4.   Total HC (THC) concentration initial contamination correction

For HC measurement, x

THC[THC-FID] shall be calculated by using the initial THC contamination concentration x THC[THC-FID]init from point 7.3.1.3 of Annex VI by means of equation (7-83):

| | |

| --- | --- | | Image omitted; see official source | (7-83) |

Where:

x

THC[THC-FID]cor = THC concentration corrected for contamination [mol/mol]

x THC[THC-FID]uncorr = THC uncorrected concentration [mol/mol]

x THC[THC-FID]init = initial THC contamination concentration [mol/mol]

3.3.5.   Flow-weighted mean concentration

In some points of this section, it may be necessary to calculate a flow-weighted mean concentration to determine the applicability of certain provisions. A flow-weighted mean is the mean of a quantity after it is weighted proportional to a corresponding flow rate. For example, if a gas concentration is measured continuously from the raw exhaust gas of an engine, its flow-weighted mean concentration is the sum of the products of each recorded concentration times its respective exhaust gas molar flow rate, divided by the sum of the recorded flow rate values. As another example, the bag concentration from a CVS system is the same as the flow-weighted mean concentration because the CVS system itself flow-weights the bag concentration.  A certain flow-weighted mean concentration of an emission at the emission limit value might be already expected based on previous testing with similar engines or testing with similar equipment and instruments.

3.4.   Chemical balances of fuel, intake air, and exhaust gas

3.4.1.   General

Chemical balances of fuel, intake air and exhaust gas may be used to calculate flows, the amount of water in their flows, and the wet concentration of constituents in their flows. With one flow rate of either fuel, intake air or exhaust gas, chemical balances may be used to determine the flows of the other two. For example, chemical balances along with either intake air or fuel flow to determine raw exhaust gas flow may be used.

3.4.2.   Procedures that require chemical balances

Chemical balances are required to determine the following:

  • (a) The amount of water in a raw or diluted exhaust gas flow, x H2Oexh, when the amount of water to correct for the amount of water removed by a sampling system is not measured;
  • (b) The flow-weighted mean fraction of dilution air in diluted exhaust gas, x dil/exh, when dilution air flow is not measured to correct for background emissions. It has to be noted that if chemical balances are used for this purpose, the exhaust gas is assumed to be stoichiometric, even if it is not.
3.4.3.   Chemical balance procedure

The calculations for a chemical balance involve a system of equations that require iteration. The initial values of up to three quantities shall be guessed: the amount of water in the measured flow, x H2Oexh, fraction of dilution air in diluted exhaust gas (or excess air in the raw exhaust gas), x dil/exh, and the amount of products on a C1 basis per dry mole of dry measured flow, x Ccombdry. Time-weighted mean values of combustion air humidity and dilution air humidity in the chemical balance may be used; as long as combustion air and dilution air humidity remain within tolerances of ± 0,0025 mol/mol of their respective mean values over the test interval. For each emission concentration, x, and amount of water x H2Oexh, their completely dry concentrations, x dry and x H2Oexhdry shall be determined. The fuel atomic hydrogen-to-carbon ratio, α, oxygen-to-carbon ratio, β and carbon mass fraction of fuel, w C shall also be used. For the test fuel, α and β or the default values in Table 7.3 may be used.

Use the following steps to complete a chemical balance:

  • (a) Measured concentrations such as, x CO2meas, x NOmeas, and x H2Oint, shall be converted to dry concentrations by dividing them by one minus the amount of water present during their respective measurements; for example: x H2OxCO2meas, x H2OxNOmeas, and x H2Oint. If the amount of water present during a ‘wet’ measurement is the same as the unknown amount of water in the exhaust gas flow, x H2Oexh, it has to be iteratively solved for that value in the system of equations. If only total NOx are measured and not NO and NO2 separately, good engineering judgement shall be used to estimate a split in the total NOx concentration between NO and NO2 for the chemical balances. The molar concentration of NOx, x NOx, may be assumed to be 75 % NO and 25 % NO2. For NO2 storage after-treatment systems, x NOx may be assumed to be 25 % NO and 75 % NO2. For calculating the mass of NOx emissions, the molar mass of NO2 for the effective molar mass of all NOx species, regardless of the actual NO2 fraction of NOx, shall be used;
- (b) Equations (7-82) to (7-99) in paragraph (d) of this point have to be entered into a computer program to iteratively solve for x

H2Oexh, x Ccombdry and x dil/exh. Good engineering judgment shall be used to guess initial values for x H2Oexh, x Ccombdry, and x dil/exh. Guessing an initial amount of water that is about twice the amount of water in the intake or dilution air is recommended. Guessing an initial value of x Ccombdry as the sum of the measured CO2, CO, and THC values is recommended. Guessing an initial x dil between 0,75 and 0,95, such as 0,8 is also recommended. Values in the system of equations shall be iterated until the most recently updated guesses are all within ± 1 % of their respective most recently calculated values;

- (c) The following symbols and subscripts are used in the equation system of paragraph (d) of this point where x unit is mol/mol:

Symbol Description x dil/exh Amount of dilution gas or excess air per mole of exhaust gas x H2Oexh Amount of H2O in exhaust per mole of exhaust gas x Ccombdry Amount of carbon from fuel in the exhaust per mole of dry exhaust gas x H2Oexhdry Amount of water in exhaust per dry mole of dry exhaust gas x prod/intdry Amount of dry stoichiometric products per dry mole of intake air x dil/exhdry Amount of dilution gas and/or excess air per mole of dry exhaust gas x int/exhdry Amount of intake air required to produce actual combustion products per mole of dry (raw or diluted) exhaust gas x raw/exhdry Amount of undiluted exhaust, without excess air, per mole of dry (raw or diluted) exhaust gas x O2intdry Amount of intake air O2 per mole of dry intake air; x O2intdry = 0,209445 mol/mol may be assumed x CO2intdry Amount of intake air CO2 per mole of dry intake air. x CO2intdry = 375 μmol/mol may be used, but measuring the actual concentration in the intake air is recommended x H2Ointdry Amount of the intake air H2O per mole of dry intake air x CO2int Amount of intake air CO2 per mole of intake air x CO2dil Amount of dilution gas CO2 per mole of dilution gas x CO2dildry Amount of dilution gas CO2 per mole of dry dilution gas. If air is used as diluent, x CO2dildry = 375 μmol/mol may be used, but measuring the actual concentration in the intake air is recommended x H2Odildry Amount of dilution gas H2O per mole of dry dilution gas x H2Odil Amount of dilution gas H2O per mole of dilution gas x [emission]meas Amount of measured emission in the sample at the respective gas analyzer x [emission]dry Amount of emission per dry mole of dry sample x H2O[emission]meas Amount of water in sample at emission-detection location. These values shall be measured or estimated according to point 9.3.2.3.1. x H2Oint Amount of water in the intake air, based on a humidity measurement of intake air K H2Ogas Water-gas reaction equilibrium coefficient. 3,5 or a different value might be calculated using good engineering judgement. α Atomic hydrogen-to-carbon ratio of the mixture of fuel(s) (CHαOβ) being combusted, weighted by molar consumption β Atomic oxygen-to-carbon ratio of the mixture of fuel(s) (CHαOβ) being combusted, weighted by molar consumption

At the end of the chemical balance, the molar flow rate is calculated as specified in points 3.5.3 and 3.6.3.

3.4.4.   NOx correction for humidity

All the NOx concentrations, including dilution air background concentrations, shall be corrected for intake-air humidity using equation (7-102) or (7-103):

  • (a) For compression-ignition engines x NOxcor = x NOxuncor · (9,953 · x H2O + 0,832) (7-102)
  • (b) For spark-ignition engines x NOxcor = x NOxuncor · (18,840 · x H2O + 0,68094) (7-103) Where: x NOxuncor = uncorrected NOx molar concentration in the exhaust gas [μmol/mol] x H2O = amount of water in the intake air [mol/mol]

3.5.   Measurement of gaseous emissions in raw exhaust gas

3.5.1.   Mass of gaseous emissions

To calculate the total mass per test of gaseous emission m gas [g/test], its molar concentration shall be multiplied by its respective molar flow and by exhaust gas molar mass; then integration over test cycle shall be performed [equation (7-104)]:
Image omitted; see official source (7-104)

Where:
M gas = molar mass of the generic gaseous emission [g/mol]
--- --- ---
ṅ exh = instantaneous exhaust gas molar flow rate on a wet basis [mol/s]
--- --- ---
x gas = instantaneous generic gas molar concentration on a wet basis [mol/mol]
--- --- ---
t = time [s]

Since equation (7-104) has to be solved by numerical integration, it is transformed in equation (7-105):
Image omitted; see official source ⇒Image omitted; see official source (7-105)

Where:
M gas = generic emission molar mass [g/mol]
| | | |

| --- | --- | --- | | ṅ exh i | = | instantaneous exhaust gas molar flow rate on a wet basis [mol/s] | | | | | | --- | --- | --- | | x gas i | = | instantaneous generic gas molar concentration on a wet basis [mol/mol] | | | | | | --- | --- | --- | | ƒ | = | data sampling rate [Hz] | | | | | | --- | --- | --- | | N | = | number of measurements [-] |

General equation may be modified according to which measurement system is used, batch or continuous sampling, and if a varying rather than a constant flow rate is sampled.

  • (a) For continuous sampling, in the general case of varying flow rate, the mass of the gaseous emission m gas [g/test] shall be calculated by means of equation (7-106): Image omitted; see official source (7-106) Where: M gas = generic emission molar mass [g/mol] ṅ exh i = instantaneous exhaust gas molar flow rate on a wet basis [mol/s] x gas i = instantaneous gaseous emission molar fraction on a wet basis [mol/mol] ƒ = data sampling rate [Hz] N = number of measurements [-]
  • (b) Still for continuous sampling but in the particular case of constant flow rate the mass of the gaseous emission m gas [g/test] shall be calculated by means of equation (7-107): Image omitted; see official source (7-107) Where: M gas = generic emission molar mass [g/mol] ṅ exh = exhaust gas molar flow rate on a wet basis [mol/s] Image omitted; see official source = mean gaseous emission molar fraction on a wet basis [mol/mol] Δt = time duration of test interval
  • (c) For the batch sampling, regardless the flow rate is varying or constant, equation (7-104) can be simplified by means of equation (7-108): Image omitted; see official source (7-108) Where: M gas = generic emission molar mass [g/mol] ṅ exh i = instantaneous exhaust gas molar flow rate on a wet basis [mol/s] Image omitted; see official source = mean gaseous emission molar fraction on a wet basis [mol/mol] ƒ = data sampling rate [Hz] N = number of measurements [-]

3.5.2.   Dry-to-wet concentration conversion

Parameters of this point are obtained from the results of the chemical balance calculated in point 3.4.3. The following relation exists between gas molar concentrations in the measured flow x gasdry and x gas [mol/mol] expressed on a dry and wet basis respectively [equations (7-109) and (7-110)]:
Image omitted; see official source (7-109)
Image omitted; see official source (7-110)

where:

| | | |

| --- | --- | --- | | x H2O | = | molar fraction of water in the measured flow on a wet basis [mol/mol] | | | | | | --- | --- | --- | | x H2Odry | = | molar fraction of water in the measured flow on a dry basis [mol/mol] |

For gaseous emissions a removed water correction shall be performed for the generic concentration x [mol/mol] by means of equation (7-111):
Image omitted; see official source (7-111)

Where:
x [emission]meas = molar fraction of emission in the measured flow at measurement location [mol/mol]
| | | |

| --- | --- | --- | | x H2O[emission]meas | = | amount of water in the measured flow at the concentration measurement [mol/mol] |

| | | |

| --- | --- | --- | | x H2Oexh | = | amount of water at the flowmeter [mol/mol] |

3.5.3.   Exhaust gas molar flow rate

The flow rate of the raw exhaust gas can be directly measured or can be calculated based on the chemical balance of point 3.4.3. Calculation of raw exhaust gas molar flow rate is performed from measured intake air molar flow rate or fuel mass flow rate. The raw exhaust gas molar flow rate can be calculated from the sampled emissions, ṅexh, based on the measured intake air molar flow rate, ṅint, or the measured fuel mass flow rate, ṁfuel, and the values calculated using the chemical balance in point 3.4.3. It shall be solved for the chemical balance in point 3.4.3 at the same frequency that ṅint or ṁfuel is updated and recorded.

  • (a) Crankcase flow rate. The raw exhaust gas flow can be calculated based on ṅint or ṁfuel only if at least one of the following is true about crankcase emission flow rate:
  • (i) The test engine has a production emission-control system with a closed crankcase that routes crankcase flow back to the intake air, downstream of intake air flow meter;
  • (ii) During emission testing open crankcase flow shall be routed to the exhaust gas according to point 6.10 of Annex VI;
  • (iii) Open crankcase emissions and flow are measured and added brake-specific emission calculations;
  • (iv) Using emission data or an engineering analysis, it can be demonstrated that neglecting the flow rate of open crankcase emissions does not adversely affect compliance with the applicable standards;
  • (b) Molar flow rate calculation based on intake air. Based on ṅint, exhaust gas molar flow rate ṅexh [mol/s] shall be calculated by means of equation (7-112): Image omitted; see official source (7-112) Where: ṅ exh = raw exhaust gas molar flow rate from which emissions are measured [mol/s] ṅ ind = intake air molar flow rate including humidity in intake air [mol/s] x int/exhdry = amount of intake air required to produce actual combustion products per mole of dry (raw or diluted) exhaust gas [mol/mol] x raw/exhdry = amount of undiluted exhaust gas, without excess air, per mole of dry (raw or diluted) exhaust gas [mol/mol] x H2Oexhdry = amount of water in exhaust gas per mole of dry exhaust gas [mol/mol]
  • (c) Molar flow rate calculation based on fuel mass flow rate Based on ṁfuel, ṅexh [mol/s] shall be calculated as follows: When conducting laboratory testing this calculation may only be used for discrete-mode NRSC and RMC [equation (7-113)]: Image omitted; see official source (7-113) Where: ṅ exh = raw exhaust gas molar flow rate from which emissions are measured ṁ fuel = fuel flow rate including humidity in intake air [g/s] w C = carbon mass fraction for the given fuel [g/g] x H2Oexhdry = amount of H2O per dry mole of measured flow [mol/mol] M C = molecular mass of carbon 12,0107 g/mol x Ccombdry = amount of carbon from fuel in the exhaust gas per mole of dry exhaust gas [mol/mol]
- (d) Exhaust gas molar flow rate calculation based on measured intake air molar flow rate, diluted exhaust gas molar flow rate, and dilute chemical balance

Exhaust gas molar flow rate ṅ exh [mol/s] may be calculated based on the measured intake air molar flow rate, ṅ int, the measured diluted exhaust gas molar flow rate, ṅ dexh, and the values calculated using the chemical balance in point 3.4.3. Note that the chemical balance must be based on diluted exhaust gas concentrations. For continuous-flow calculations, solve for the chemical balance in point 3.4.3 at the same frequency that ṅ int and ṅ dexh are updated and recorded. This calculated ṅ dexh may be used for the PM dilution ratio verification, the calculation of dilution air molar flow rate in the background correction in point 3.6.1 and the calculation of mass of emissions in point 3.5.1 for species that are measured in the raw exhaust gas. Based on diluted exhaust gas and intake air molar flow rate, exhaust gas molar flow rate, ṅ exh [mol/s] shall be calculated as follows: Image omitted; see official source (7-114) where ṅ exh = raw exhaust gas molar flow rate from which emissions are measured [mol/s]; x int/exhdry = amount of intake air required to produce actual combustion products per mole of dry (raw or diluted) exhaust gas [mol/mol]; x raw/exhdry = amount of undiluted exhaust gas, without excess air, per mole of dry (raw or diluted) exhaust gas [mol/mol]; x H2Oexh = amount of water in exhaust gas per mole of exhaust gas [mol/mol]; ṅ dexh = diluted exhaust gas molar flow rate from which emissions are measured [mol/s]; ṅ int = intake air molar flow rate including humidity in intake air [mol/s].

3.6.   Diluted gaseous emissions

3.6.1.   Emission mass calculation and background correction

The calculation of gaseous emissions mass m gas [g/test] as a function of molar emissions flow rates shall be calculated as follows:

  • (a) Continuous sampling, varying flow rate, shall be calculated by means of equation (7-106): Image omitted; see official source [see equation (7-106)] Where: M gas = generic emission molar mass [g/mol] ṅexhi = instantaneous exhaust gas molar flow rate on a wet basis [mol/s] xgasi = instantaneous generic gas molar concentration on a wet basis [mol/mol] f = data sampling rate [Hz] N = number of measurements [-]
- (b) Continuous sampling, constant flow rate, shall be calculated by means of equation (7-107):

Image omitted; see official source [see equation (7-107)] Where: M gas = generic emission molar mass [g/mol] ṅexh = exhaust gas molar flow rate on a wet basis [mol/s] Image omitted; see official source = mean gaseous emission molar fraction on a wet basis [mol/mol] Δt = time duration of test interval

  • (c) Batch sampling, regardless the flow rate is varying or constant, shall be calculated by means of equation (7-108): Image omitted; see official source [see equation (7-108)] Where: M gas = generic emission molar mass [g/mol] ṅexhi = instantaneous exhaust gas molar flow rate on a wet basis [mol/s] Image omitted; see official source = mean gaseous emission molar fraction on a wet basis [mol/mol] f = data sampling rate [Hz] N = number of measurements [-]
  • (d) In case of diluted exhaust gas calculated values for mass of the pollutants shall be corrected by subtracting the mass of background emissions, due to dilution air:
  • (i) Firstly, the molar flow rate of dilution air nairdil [mol/s] shall be determined over the test interval. This may be a measured quantity or a quantity calculated from the diluted exhaust gas flow and the flow-weighted mean fraction of dilution air in diluted exhaust gas,
Image omitted; see official source ;
  • (ii) The total flow of dilution air n airdil [mol] shall be multiplied by the mean concentration of background emission. This may be a time-weighted mean or a flow-weighted mean (e.g., a proportionally sampled background). The product of n airdil and the mean concentration of a background emission is the total amount of a background emission;
  • (iii) If the result is a molar quantity, it shall be converted to a mass of the background emission m bkgnd [g] by multiplying it by emission molar mass, M gas [g/mol];
  • (iv) Total background mass shall be subtracted from total mass to correct for background emissions;
  • (v) The total flow of dilution air may be determined by a direct flow measurement. In this case, the total mass of background shall be calculated, using the dilution air flow, n airdil. The background mass shall be subtracted from the total mass. The result shall be used in brake-specific emission calculations;
  • (vi) The total flow of dilution air may be determined from the total flow of diluted exhaust gas and a chemical balance of the fuel, intake air, and exhaust gas as described in point 3.4. In this case, the total mass of background shall be calculated, using the total flow of diluted exhaust gas, n dexh. Then this result shall be multiplied by the flow-weighted mean fraction of dilution air in diluted exhaust gas,
Image omitted; see official source .

Considering the two cases (v) and (vi), equations (7-115) and (7-116) shall be used: Image omitted; see official source or Image omitted; see official source (7-115) m gascor = m gas – m bkgnd (7-116) where: m gas = total mass of the gaseous emission [g] m bkgnd = total background masses [g] m gascor = mass of gas corrected for background emissions [g] M gas = molecular mass of generic gaseous emission [g/mol] x gasdil = gaseous emission concentration in dilution air [mol/mol] n airdil = dilution air molar flow [mol] Image omitted; see official source = flow-weighted mean fraction of dilution air in diluted exhaust gas [mol/mol] Image omitted; see official source = gas fraction of background [mol/mol] n dexh = total flow of diluted exhaust gas [mol]

3.6.2.   Dry-to wet concentration conversion

The same relations for raw gases (point 3.5.2) shall be used for dry-to-wet conversion on diluted samples. For dilution air a humidity measurement shall be performed with the aim to calculate its water vapour fraction x H2Odildry [mol/mol] by means of equation (7-96):

| | |

| --- | --- | | Image omitted; see official source | [(see equation (7-96)] |

Where:
x H2Odil = water molar fraction in the dilution air flow [mol/mol]

3.6.3.   Exhaust gas molar flow rate

  • (a) Calculation via chemical balance; The molar flow rate ṅ exh [mol/s] can be calculated based on fuel mass flow rate ṁ fuel by means of equation (7-113): Image omitted; see official source (see equation 7-113) Where: ṅ exh = raw exhaust gas molar flow rate from which emissions are measured ṁ fuel = fuel flow rate including humidity in intake air [g/s] w C = carbon mass fraction for the given fuel [g/g] x H2Oexhdry = amount of H2O per dry mole of measured flow [mol/mol] M C = molecular mass of carbon 12,0107 g/mol x Ccombdry = amount of carbon from fuel in the exhaust gas per mole of dry exhaust gas [mol/mol]
  • (b) Measurement The exhaust gas molar flow rate may be measured by means of three systems:
  • (i) PDP molar flow rate. Based upon the speed at which the Positive Displacement Pump (PDP) operates for a test interval, the corresponding slope a 1, and intercept, a 0 [-], as calculated with the calibration procedure set out in point 3.9.2, shall be used to calculate molar flow rate ṅ [mol/s] by means of equation (7-117): Image omitted; see official source (7-117) with: Image omitted; see official source (7-118) where: a 1 = calibration coefficient [m3/s] a 0 = calibration coefficient [m3/rev] p in, p out = inlet/outlet pressure [Pa] R = molar gas constant [J/(mol · K)] T in = inlet temperature [K] V rev = PDP pumped volume [m3/rev] f n.,PDP = PDP speed [rev/s]
  • (ii) SSV molar flow rate. Based on the C d versus R e # equation determined in accordance with point 3.9.4, the Sub-Sonic Venturi (SSV) molar flow rate during an emission test ṅ [mol/s] shall be calculated by means of equation (7-119): Image omitted; see official source (7-119) Where: p in = inlet pressure [Pa] A t = Venturi throat cross-sectional area [m2] R = molar gas constant [J/(mol · K)] T in = inlet temperature [K] Z = compressibility factor M mix = molar mass of diluted exhaust gas [kg/mol] C d = discharge coefficient of the SSV [-] C f = flow coefficient of the SSV [-]
  • (iii) CFV molar flow rate. To calculate the molar flow rate through one venturi or one combination of venturis, its respective mean C d and other constants, determined in accordance with point 3.9.5, shall be used. The calculation of its molar flow rate ṅ [mol/s] during an emission test shall be calculated by means of equation (7-120): Image omitted; see official source (7-120) Where: p in = inlet pressure [Pa] A t = Venturi throat cross-sectional area [m2] R = molar gas constant [J/(mol · K)] T in = inlet temperature [K] Z = compressibility factor M mix = molar mass of diluted exhaust gas [kg/mol] C d = discharge coefficient of the CFV [-] C f = flow coefficient of the CFV [-]

3.7.   Determination of particulates

3.7.1.   Sampling
- (a) Sampling from a varying flow rate:

If a batch sample from a changing exhaust gas flow rate is collected, a sample proportional to the changing exhaust gas flow rate shall be extracted. The flow rate shall be integrated over a test interval to determine the total flow. The mean PM concentration

Image omitted; see official source (which is already in units of mass per mole of sample) shall be multiplied by the total flow to obtain the total mass of PM m PM [g] by means of equation (7-121): Image omitted; see official source (7-121) Where: ṅi = instantaneous exhaust gas molar flow rate [mol/s] Image omitted; see official source = mean PM concentration [g/mol] Δti = sampling interval [s]

  • (b) Sampling from a constant flow rate If a batch sample from a constant exhaust gas flow rate is collected, the mean molar flow rate from which the sample is extracted shall be determined. The mean PM concentration shall be multiplied by the total flow to obtain the total mass of PM m PM[g] by means of equation (7-122): Image omitted; see official source (7-122) where: ṅ = exhaust gas molar flow rate [mol/s] Image omitted; see official source = mean PM concentration [g/mol] Δt = time duration of test interval [s] For sampling with a constant dilution ratio (DR), m PM [g] shall be calculated by means of equation (7-123): Image omitted; see official source (7-123) where: m PMdil = PM mass in dilution air [g] DR = dilution ratio [-] defined as the ratio between the mass of the emission m and the mass of diluted exhaust gas m dil/exh (DR = m/m dil/exh). The dilution ratio DR can be expressed as a function of x dil/exh [equation (7-124)]: Image omitted; see official source (7-124)

3.7.2.   Background correction

The same approach as that of point 3.6.1 shall be applied to correct the mass of PM for the background. Multiplying

Image omitted; see official source by the total flow of dilution air, the total background mass of PM (m PMbkgnd [g]) is obtained. Subtraction of total background mass from total mass gives background corrected mass of particulates m PMcor [g] [equation (7-125)]:
Image omitted; see official source (7-125)

where:
m PMuncor = uncorrected PM mass [g]
--- --- ---
Image omitted; see official source = mean PM concentration in dilution air [g/mol]
--- --- ---
n airdil = dilution air molar flow [mol]

3.8.   Cycle work and specific emissions

3.8.1.   Gaseous emissions

3.8.1.1.   Transient (NRTC and LSI-NRTC) test cycles and RMC

Reference is made to points 3.5.1 and 3.6.1 for raw and diluted exhaust gas respectively. The resulting values for power Pi [kW] shall be integrated over a test interval. The total work W act [kWh] shall be calculated by means of equation (7-126):
Image omitted; see official source (7-126)

Where:
Pi = instantaneous engine power [kW]
--- --- ---
ni = instantaneous engine speed [rpm]
--- --- ---
Ti = instantaneous engine torque [N·m]
--- --- ---
W act = actual cycle work [kWh]
--- --- ---
ƒ = data sampling rate [Hz]
--- --- ---
N = number of measurements [-]
--- --- ---
Δti = the measurement interval [s]

Where auxiliaries were fitted in accordance with Appendix 2 of Annex VI there shall be no adjustment to the instantaneous engine torque in equation (7-126). Where, according to points 6.3.2 or 6.3.3 of Annex VI to this regulation necessary auxiliaries that should have been fitted for the test are not installed, or auxiliaries that should have been removed for the test are installed, the value of Ti used in equation (7-126) shall be adjusted by means of equation (7-127):
Ti = Ti ,meas + Ti ,AUX (7-127)

Where:

  • T i,meas is the measured value of instantaneous engine torque
  • T i,AUX is the corresponding value of torque required to drive auxiliaries determined in accordance with point 7.7.2.3(b) of Annex VI.

The specific emissions e gas [g/kWh] shall be calculated in the following ways depending on the type of test cycle.
Image omitted; see official source (7-128)

where:
m gas = total mass of emission [g/test]
--- --- ---
W act = cycle work [kWh]

In case of the NRTC, for gaseous emissions other than CO2 the final test result e gas [g/kWh] shall be a weighted average from cold-start run and hot-start run calculated by means of equation (7-129):
Image omitted; see official source (7-129)

Where:

m cold is the gas mass emissions of the cold-start NRTC [g]

W act, cold is the actual cycle work of the cold-start NRTC [kWh]

m hot is the gas mass emissions of the hot-start NRTC [g]

W act, hot is the actual cycle work of the hot-start NRTC [kWh]

In case of the NRTC, for CO2 the final test result e CO2 [g/kWh] shall be calculated from the hot-start NRTC calculated by means of equation (7-130):
Image omitted; see official source (7-130)
Where:

m CO2, hot is the CO2 mass emissions of the hot-start NRTC [g]

W act, hot is the actual cycle work of the hot-start NRTC [kWh]

3.8.1.2.   Discrete-mode NRSC

The specific emissions e gas [g/kWh] shall be calculated by means of equation (7-131):
Image omitted; see official source (7-131)

where:
ṁ gas, i = mean emission mass flow rate for the mode i [g/h]
--- --- ---
Pi = engine power for the mode i [kW] calculated by adding to the measured power Pmeas [kW] the power required to drive auxiliaries PAUX [kW] determined in accordance with equation (6-8) of Annex VI (Pi = Pmeas + PAUX)
--- --- ---
WFi = weighting factor for the mode i [-]
--- --- ---
Nmode = number of modes in applicable discrete-mode NRSC

3.8.2.   Particulate emissions

3.8.2.1.   Transient (NRTC and LSI-NRTC) test cycles and RMC

The particulate specific emissions shall be calculated by transforming equation (7-128) into equation (7-132) where e gas [g/kWh] and m gas [g/test] are substituted by e PM [g/kWh] and m PM [g/test] respectively:
Image omitted; see official source (7-132)

Where:
m PM = total mass of particulates emission, calculated according to point 3.7.1 [g/test]
--- --- ---
W act = cycle work [kWh]

The emissions on the transient composite cycle (i.e. cold-start NRTC and hot-start NRTC) shall be calculated as shown in point 3.8.1.1.

3.8.2.2.   Discrete-mode NRSC

The particulate specific emission e PM [g/kWh] shall be calculated in the following way:

  • 3.8.2.2.1. For the single-filter method by means of equation (7-133):
Image omitted; see official source (7-133)

Where:
Pi = engine power for the mode i [kW] calculated by adding to the measured power Pmeas [kW] the power required to drive auxiliaries PAUX [kW] determined in accordance with equation (6-8) of Annex VI (Pi = Pmeas + PAUX).
--- --- ---
WFi = weighting factor for the mode i [-]
--- --- ---
ṁ PM = particulate mass flow rate [g/h]
--- --- ---
Nmode = number of modes in applicable discrete-mode NRSC
  • 3.8.2.2.2. For the multiple-filter method by means of equation (7-134):
Image omitted; see official source (7-134)

Where:
Pi = engine power for the mode i [kW] calculated by adding to the measured power Pmeas [kW] the power required to drive auxiliaries PAUX [kW] determined in accordance with equation (6-8) of Annex VI (Pi = Pmeas + PAUX).
| | | |

| --- | --- | --- | | WFi | = | weighting factor for the mode i [-] | | | | | | --- | --- | --- | | ṁ PM i | = | particulate mass flow rate at mode i [g/h] |

| | | |

| --- | --- | --- | | Nmode | = | number of modes in applicable discrete-mode NRSC |

For the single-filter method, the effective weighting factor, WF eff i, for each mode shall be calculated by means of equation (7-135):

| | |

| --- | --- | | Image omitted; see official source | (7-135) |

Where:

| | | |

| --- | --- | --- | | m smpldexh i | = | mass of the diluted exhaust gas sample passed through the particulate sampling filters at mode i [kg] | | | | | | --- | --- | --- | | m smpldexh | = | mass of the diluted exhaust gas sample passed through the particulate sampling filters [kg] | | | | | | --- | --- | --- | | ṁ eqdexhwet i | = | equivalent diluted exhaust gas mass flow rate at mode i [kg/s] | | | | | | --- | --- | --- | | Image omitted; see official source | = | average equivalent diluted exhaust gas mass flow rate [kg/s] |

The value of the effective weighting factors shall be within 0,005 (absolute value) of the weighting factors listed in Appendix 1 of Annex XVII.

3.8.3.   Adjustment for emission controls that are regenerated on an infrequent (periodic) basis

In case of engines, other than those of category RLL, equipped with exhaust after-treatment systems that are regenerated on an infrequent (periodic) basis (see point 6.6.2 of Annex VI), the specific emissions of gaseous and particulate pollutants calculated according to points 3.8.1 and 3.8.2 shall be corrected with either the applicable multiplicative adjustment factor or with the applicable additive adjustment factor. In the case that infrequent regeneration did not take place during the test the upward factor shall be applied (k ru,m or k ru,a). In the case that infrequent regeneration took place during the test the downward factor shall be applied (k rd,m or k rd,a). In the case of the discrete-mode NRSC, where the adjustment factors have been determined for each mode they shall be applied to each mode during the calculation of the weighted emission result.

3.8.4.   Adjustment for deterioration factor

The specific emissions of gaseous and particulate pollutants calculated according to points 3.8.1 and 3.8.2, where applicable inclusive of the infrequent regeneration adjustment factor according to point 3.8.3, shall also be adjusted by the applicable multiplicative or additive deterioration factor established according to the requirements of Annex III.

3.9.   Diluted Exhaust Flow (CVS) Calibration and Related Calculations

This section describes the calculations for calibrating various flow meters. Point 3.9.1 first describes how to convert reference flow meter outputs for use in the calibration equations, which are presented on a molar basis. The remaining points describe the calibration calculations that are specific to certain types of flow meters.

3.9.1.   Reference meter conversions

The calibration equations in this section use molar flow rate, ṅ ref, as a reference quantity. If the adopted reference meter outputs a flow rate in a different quantity, such as standard volume rate, V̇ stdref actual volume rate, V̇ actdref, or mass rate, ṁ ref, the reference meter output shall be converted to a molar flow rate by means of equations (7-136), (7-137) and (7-138), noting that while values for volume rate, mass rate, pressure, temperature, and molar mass may change during an emission test, they should be kept as constant as practical for each individual set point during a flow meter calibration:
Image omitted; see official source (7-136)
where:
ṅ ref = reference molar flow rate [mol/s]
--- --- ---
V̇ stdref = reference volume flow rate, corrected to a standard pressure and a standard temperature [m3/s]
--- --- ---
V̇ actref = reference volume flow rate, at the actual pressure and temperature [m3/s]
--- --- ---
ṁ ref = reference mass flow [g/s]
--- --- ---
p std = standard pressure [Pa]
--- --- ---
p act = actual pressure of the gas [Pa]
--- --- ---
T std = standard temperature [K]
| | | |

| --- | --- | --- | | T act | = | actual temperature of the gas [K] | | | | | | --- | --- | --- | | R | = | molar gas constant [J/(mol · K)] | | | | | | --- | --- | --- | | M mix | = | molar mass of the gas [g/mol] |

3.9.2.   PDP calibration calculations

For each restrictor position, the following values shall be calculated from the mean values determined in point 8.1.8.4 of Annex VI, as follows:

  • (c) A least-squares regression of PDP volume pumped per revolution, V rev, versus PDP slip correction factor, K s, shall be performed by calculating slope, a 1, and intercept, a 0, as described in Appendix 4;
  • (d) The procedure in subparagraphs (a) to (c) of this point shall be repeated for every speed that PDP is operated;
  • (f) For each speed at which the PDP is operated, the corresponding slope, a 1, and intercept, a 0, shall be used to calculate flow rate during emission testing as described in point 3.6.3(b).

3.9.3.   Venturi governing equations and permissible assumptions

This section describes the governing equations and permissible assumptions for calibrating a venturi and calculating flow using a venturi. Because a subsonic venturi (SSV) and a critical-flow venturi (CFV) both operate similarly, their governing equations are nearly the same, except for the equation describing their pressure ratio, r (i.e., r SSV versus r CFV). These governing equations assume one-dimensional isentropic inviscid compressible flow of an ideal gas. In point 3.9.3(d), other assumptions that may be made are described. If the assumption of an ideal gas for the measured flow is not allowed, the governing equations include a first-order correction for the behaviour of a real gas; namely, the compressibility factor, Z. If good engineering judgment dictates using a value other than Z = 1, an appropriate equation of state to determine values of Z as a function of measured pressures and temperatures may be used, or specific calibration equations may be developed based on good engineering judgment. It shall be noted that the equation for the flow coefficient, C f, is based on the ideal gas assumption that the isentropic exponent, γ, is equal to the ratio of specific heats, cp/cV. If good engineering judgment dictates using a real gas isentropic exponent, an appropriate equation of state to determine values of γ as a function of measured pressures and temperatures may be used, or specific calibration equations may be developed. Molar flow rate, ṅ [mol/s], shall be calculated by means of equation (7-139):
Image omitted; see official source (7-139)

Where:
C d = Discharge coefficient, as determined in point 3.9.3(a) [-]
| | | |

| --- | --- | --- | | C f | = | Flow coefficient, as determined in point 3.9.3(b) [-] | | | | | | --- | --- | --- | | A t | = | Venturi throat cross-sectional area [m2] | | | | | | --- | --- | --- | | p in | = | Venturi inlet absolute static pressure [Pa] | | | | | | --- | --- | --- | | Z | = | Compressibility factor [-] | | | | | | --- | --- | --- | | M mix | = | Molar mass of gas mixture [kg/mol] | | | | | | --- | --- | --- | | R | = | Molar gas constant [J/(mol · K)] | | | | | | --- | --- | --- | | T in | = | Venturi inlet absolute temperature [K] |

  • (a) Using the data collected in point 8.1.8.4 of Annex VI, C d is calculated by means of equation (7-140): Image omitted; see official source (7-140) Where: ṅ ref = reference molar flow rate [mol/s] Other symbols as per equation (7-139).
  • (b) C f shall be determined using one of the following methods:
  • (i) For CFV flow meters only, C fCFV is derived from Table 7.5 based on values for β (ratio of venturi throat to inlet diameters) and γ (ratio of specific heats of the gas mixture), using linear interpolation to find intermediate values: Table 7.5 C fCFV versus β and γ for CFV flow meters C fCFV β γ exh = 1,385 γ dexh = γ air = 1,399 0,000 0,6822 0,6846 0,400 0,6857 0,6881 0,500 0,6910 0,6934 0,550 0,6953 0,6977 0,600 0,7011 0,7036 0,625 0,7047 0,7072 0,650 0,7089 0,7114 0,675 0,7137 0,7163 0,700 0,7193 0,7219 0,720 0,7245 0,7271 0,740 0,7303 0,7329 0,760 0,7368 0,7395 0,770 0,7404 0,7431 0,780 0,7442 0,7470 0,790 0,7483 0,7511 0,800 0,7527 0,7555 0,810 0,7573 0,7602 0,820 0,7624 0,7652 0,830 0,7677 0,7707 0,840 0,7735 0,7765 0,850 0,7798 0,7828
  • (ii) For any CFV or SSV flow meter, equation (7-141) may be used to calculate C f: Image omitted; see official source (7-141) Where: γ = isentropic exponent [-]. For an ideal gas, this is the ratio of specific heats of the gas mixture, cp/cV r = pressure ratio, as determined in paragraph (c)(3) of this point β = ratio of venturi throat to inlet diameters
- (c) The pressure ratio r shall be calculated as follows:
  • (i) For SSV systems only, r SSV shall be calculated by means of equation (7-142): Image omitted; see official source (7-142) Where: Δp ssv = differential static pressure; venturi inlet minus venturi throat [Pa]
  • (ii) For CFV systems only, r CFV shall be calculated iteratively by means of equation (7-143): Image omitted; see official source (7-143)
  • (d) Any of the following simplifying assumptions of the governing equations may be made, or good engineering judgment may be used to develop more appropriate values for testing:
  • (i) For emission testing over the full ranges of raw exhaust gas, diluted exhaust gas and dilution air, the gas mixture may be assumed to behave as an ideal gas: Z = 1;
  • (ii) For the full range of raw exhaust gas a constant ratio of specific heats of γ = 1,385 may be assumed;
  • (iii) For the full range of diluted exhaust gas and air (e.g., calibration air or dilution air), a constant ratio of specific heats of γ = 1,399 may be assumed;
  • (iv) For the full range of diluted exhaust gas and air, the molar mass of the mixture, M mix [g/mol], may be considered as a function only of the amount of water in the dilution air or calibration air, x H2O, determined as described in point 3.3.2 and shall be calculated by means of equation (7-144): M mix = M air· (1 –x H2O) +M H2O· (x H2O) (7-144) Where: M air = 28,96559 g/mol M H2O = 18,01528 g/mol x H2O = amount of water in the dilution or calibration air [mol/mol]
  • (v) For the full range of diluted exhaust gas and air, a constant molar mass of the mixture, M mix, may be assumed for all calibration and all testing as long as assumed molar mass differs no more than ± 1 % from the estimated minimum and maximum molar mass during calibration and testing. This assumption may be made if sufficient control of the amount of water in calibration air and in dilution air is ensured, or if sufficient water is removed from both calibration air and dilution air. Table 7.6 provides for examples of permissible ranges of dilution air dew point versus calibration air dew point: Table 7.6 Examples of dilution air and calibration air dew points at which a constant M mix may be assumed If calibration T dew (°C) is ... the following constant M mix (g/mol) is assumed for the following ranges of T dew (°C) during emission tests [^E0044] dry 28,96559 dry to 18 0 28,89263 dry to 21 5 28,86148 dry to 22 10 28,81911 dry to 24 15 28,76224 dry to 26 20 28,68685 – 8 to 28 25 28,58806 12 to 31 30 28,46005 23 to 34 (1) Range valid for all calibration and emission testing over the atmospheric pressure range (80,000 to 103,325) kPa.

3.9.4.   SSV calibration

  • (a) Molar based approach. To calibrate an SSV flow meter the following steps shall be performed:
  • (i) The Reynolds number, Re #, for each reference molar flow rate, shall be calculated using the throat diameter of the venturi, d t [equation (7-145)]. Because the dynamic viscosity, μ, is needed to compute Re#, a specific viscosity model may be used to determine μ for calibration gas (usually air), using good engineering judgment [equation (7-146)]. Alternatively, the Sutherland three-coefficient viscosity model may be used to approximate μ (see Table 7.7): Image omitted; see official source (7-145) Where: d t = diameter of the SSV throat [m] M mix = mixture molar mass [kg/mol] ṅ ref = reference molar flow rate [mol/s] and, using the Sutherland three-coefficient viscosity model: Image omitted; see official source (7-146) Where: μ = Dynamic viscosity of calibration gas [kg /(m · s)] μ 0 = Sutherland reference viscosity [kg /(m · s)] S = Sutherland constant [K] T 0 = Sutherland reference temperature [K] T in = Absolute temperature at the venturi inlet [K] Table 7.7 Sutherland three-coefficient viscosity model parameters Gas [^E0045] μ 0 T0 S Temp range within ± 2 % error Pressure limit kg /(m · s) K K K kPa Air 1,716 × 10– 5 273 111 170 to 1 900 ≤ 1 800 CO2 1,370 × 10– 5 273 222 190 to 1 700 ≤ 3 600 H2O 1,12 × 10– 5 350 1,064 360 to 1 500 ≤ 10 000 O2 1,919 × 10– 5 273 139 190 to 2 000 ≤ 2 500 N2 1,663 × 10– 5 273 107 100 to 1 500 ≤ 1 600 (1) Tabulated parameters only for the pure gases, as listed, shall be used. Parameters to calculate viscosities of gas mixtures shall not be combined.
  • (ii) An equation for C d versus Re# shall be created, using paired values of (Re#, C d). C d is calculated according to equation (7-140), with C f obtained from equation (7-141), or any mathematical expression may be used, including a polynomial or a power series. Equation (7-147) is an example of a commonly used mathematical expression for relating C d and Re#; Image omitted; see official source (7-147)
  • (iii) A least-squares regression analysis shall be performed to determine the best-fit coefficients to the equation and calculate the equation's regression statistics, the standard estimate error SEE and the coefficient of determination r 2, in accordance with Appendix 3;
  • (iv) If the equation meets the criteria of SEE < 0,5 % n ref max (or ṁ refmax) and r 2 ≥ 0,995, the equation may be used to determine C d for emission tests, as described in point 3.6.3(b);
  • (v) If the SEE and r 2 criteria are not met, good engineering judgment may be used to omit calibration data points to meet the regression statistics. At least seven calibration data points shall be used to meet the criteria;
  • (vi) If omitting points does not resolve outliers, corrective action shall be taken. For example, another mathematical expression for the C d versus Re# equation shall be selected, leaks are to be checked, or the calibration process has to be repeated. If the process shall be repeated, tighter tolerances shall be applied to measurements and more time for flows to stabilize shall be allowed;

- (vii) Once the equation meets the regression criteria, the equation may be used only to determine flow rates that are within the range of the reference flow rates used to meet the C

d versus Re# equation's regression criteria.

3.9.5.   CFV calibration

Some CFV flow meters consist of a single venturi and some consist of multiple venturis, where different combinations of venturis are used to meter different flow rates. For CFV flow meters that consist of multiple venturis, either calibration of each venturi independently to determine a separate discharge coefficient, C

d, for each venturi, or calibration of each combination of venturis as one venturi may be performed. In the case where a combination of venturis is calibrated, the sum of the active venturi throat areas is used as A t, the square root of the sum of the squares of the active venturi throat diameters as d t, and the ratio of the venturi throat to inlet diameters is the ratio of the square root of the sum of the active venturi throat diameters (d

t)

to the diameter of the common entrance to all of the venturis (D). To determine the C

d for a single venturi or a single combination of venturis, the following steps shall be performed:

  • (a) With the data collected at each calibration set point an individual C d for each point shall be calculated using equation (7-140);

- (b) The mean and standard deviation of all the C

d values shall be calculated in accordance with equations (7-155) and (7-156);

  • (c) If the standard deviation of all the C d values is less than or equal to 0,3 % of the mean C d, then the mean C d shall be used in equation (7-120), and the CFV shall be used only down to the lowest r measured during calibration; r = 1 – (Δp/pin) (7-148)

- (d) If the standard deviation of all the C

d values exceeds 0,3 % of the mean C d, the C d values corresponding to the data point collected at the lowest r measured during calibration shall be omitted;

  • (e) If the number of remaining data points is less than seven, corrective action shall be taken by checking calibration data or repeating the calibration process. If the calibration process is repeated, checking for leaks, applying tighter tolerances to measurements and allowing more time for flows to stabilize, is recommended;

- (f) If the number of remaining C

d values is seven or greater, the mean and standard deviation of the remaining C d values shall be recalculated;

  • (g) If the standard deviation of the remaining C d values is less than or equal to 0,3 % of the mean of the remaining C d, that mean C d shall be used in equation (7-120) and the CFV values only down to the lowest r associated with the remaining C d shall be used;
  • (h) If the standard deviation of the remaining C d still exceeds 0,3 % of the mean of the remaining C d values, the steps set out in points (d) to (g) shall be repeated.

Appendix 1

Drift Correction

1.

Scope and frequency

The calculations in this Appendix shall be performed to determine if gas analyzer drift invalidates the results of a test interval. If drift does not invalidate the results of a test interval, the test interval's gas analyzer responses shall be corrected for drift according to this Appendix. The drift-corrected gas analyzer responses shall be used in all subsequent emission calculations. The acceptable threshold for gas analyzer drift over a test interval is specified in point 8.2.2.2 of Annex VI.

2.

Correction principles

The calculations in this Appendix utilize a gas analyzer's responses to reference zero and span concentrations of analytical gases, as determined sometime before and after a test interval. The calculations correct the gas analyzer's responses that were recorded during a test interval. The correction is based on an analyzer's mean responses to reference zero and span gases, and it is based on the reference concentrations of the zero and span gases themselves. Validation and correction for drift shall be performed as follows:

3. Drift validation

After applying all the other corrections–except drift correction–to all the gas analyzer signals, brake-specific emissions shall be calculated in accordance with point 3.8. Then all gas analyzer signals shall be corrected for drift according to this Appendix. Brake-specific emissions shall be recalculated using all of the drift-corrected gas analyzer signals. The brake-specific emission results shall be validated and reported before and after drift correction according to point 8.2.2.2 of Annex VI.

4. Drift correction

All gas analyzer signals shall be corrected as follows:

  • (a) Each recorded concentration, xi, shall be corrected for continuous sampling or for batch sampling,

Image omitted; see official source ;

  • (b) Correction for drift shall be calculated by means of equation (7-149): Image omitted; see official source (7-149) Where: xi driftcor = concentration corrected for drift [μmol/mol] x refzero = reference concentration of the zero gas, which is usually zero unless known to be otherwise [μmol/mol] x refspan = reference concentration of the span gas [μmol/mol] x prespan = pre-test interval gas analyzer response to the span gas concentration [μmol/mol] x postspan = post-test interval gas analyzer response to the span gas concentration [μmol/mol] xi or
Image omitted; see official source

= concentration recorded, i.e. measured, during test, before drift correction [μmol/mol] x prezero = pre-test interval gas analyzer response to the zero gas concentration [μmol/mol] x postzero = post-test interval gas analyzer response to the zero gas concentration [μmol/mol]

- (c) For any pre-test interval concentrations, concentrations determined most recently before the test interval shall be used. For some test intervals, the most recent pre-zero or pre-span might have occurred before one or more previous test intervals;
  • (d) For any post-test interval concentrations, concentrations determined most recently after the test interval shall be used. For some test intervals, the most recent post-zero or post-span might have occurred after one or more subsequent test intervals;

- (e) If any pre-test interval analyzer response to the span gas concentration, x

prespan, is not recorded, x prespan shall be set equal to the reference concentration of the span gas: x prespan = x refspan;

  • (f) If any pre-test interval analyzer response to the zero gas concentration, x prezero, is not recorded, x prezero shall be set equal to the reference concentration of the zero gas: x prezero = x refzero;
  • (g) Usually the reference concentration of the zero gas, x refzero, is zero: x refzero = 0 μmol/mol. However, in some cases it might be known that x refzero has a non-zero concentration. For example, if a CO2 analyzer is zeroed using ambient air, the default ambient air concentration of CO2, which is 375 μmol/mol, may be used. In this case, x refzero = 375 μmol/mol. When an analyzer is zeroed using a non-zero x refzero, the analyzer shall be set to output the actual xrefzero concentration. For example, if x refzero = 375 μmol/mol, the analyzer shall be set to output a value of 375 μmol/mol when the zero gas is flowing to the analyzer.

Appendix 2

Carbon Flow Check

1. Introduction

All but a tiny part of the carbon in the exhaust gas comes from the fuel, and all but a minimal part of this is manifest in the exhaust gas as CO2. This is the basis for a system verification check based on CO2 measurements. In the case of SI engines without control of excess air ratio λ or SI engines operating outside the range 0,97 ≤ λ ≤ 1,03, the procedure shall additionally include measurement of HC and CO.

The flow of carbon into the exhaust gas measurement systems is determined from the fuel flow rate. The flow of carbon at various sampling points in the emissions and particulate sampling systems is determined from the CO2 (or CO2, HC and CO) concentrations and gas flow rates at those points.

In this sense, the engine provides a known source of carbon flow, and observing the same carbon flow in the exhaust pipe and at the outlet of the partial flow PM sampling system verifies leak integrity and flow measurement accuracy. This check has the advantage that the components are operating under actual engine test conditions of temperature and flow.

Figure 7.1 shows the sampling points at which the carbon flows shall be checked. The specific equations for the carbon flows at each of the sample points are given in the following points.

Figure 7.1

Measuring points for carbon flow check

Image omitted; see official source

2.

Carbon flow rate into the engine (location 1)

The carbon mass flow rate into the engine qm Cf [kg/s] for a fuel CHαOε shall be calculated by means of equation (7-150):

| | |

| --- | --- | | Image omitted; see official source | (7-150) |

Where:
qm f = fuel mass flow rate [kg/s]
3.

Carbon flow rate in the raw exhaust gas (location 2)

3.1.   Based on CO2

The carbon mass flow rate in the exhaust pipe of the engine qm Ce [kg/s] shall be determined from the raw CO2 concentration and the exhaust gas mass flow rate by means of equation (7-151):
Image omitted; see official source (7-151)

where:
c CO2,r = wet CO2 concentration in the raw exhaust gas [%]
--- --- ---
c CO2,a = wet CO2 concentration in the ambient air [%]
--- --- ---
qm ew = exhaust gas mass flow rate on wet basis [kg/s]
--- --- ---
M e = molar mass of exhaust gas [g/mol]

If CO2 is measured on a dry basis it shall be converted to a wet basis in accordance with point 2.1.3 or point 3.5.2.

3.2.   Based on CO2, HC and CO

As an alternative to performing the calculation solely based upon CO2 in point 3.1, the carbon mass flow rate in the exhaust pipe of the engine qm

Ce [kg/s] shall be determined from the raw CO2, HC and CO concentration and the exhaust gas mass flow rate by means of equation (7-152):
Image omitted; see official source (7-152)

Where:

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