(ii)

The following section 4 is inserted: ‘4. CALCULATION OF THE EXHAUST GAS FLOW 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 (V 0 for PDP, K V for CFV, C d for SSV), as determined in section 2 of Appendix 5 to Annex III). 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 or ± 11 K for a SSV-CVS), see section 2.3 of Annex V). For the PDP-CVS system: m ed = 1,293 × V 0 × N P × (p b - p 1) × 273 / (101,3 × T) where: For the CFV-CVS system: m ed = 1,293 × t × K v × p p / T 0,5 where: For the SSV-CVS system m ed = 1,293 × QSSV where: Text of image QSSV = A0d2Cdpp √[1 T (rp 1,4286 - rp 1,7143) × (1 1 - rD4rp1,4286)] with: 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 ed,i = 1,293 × V 0 × N P,i × (p b - p 1) × 273 / (101,3 × T) where: N P,i = total revolutions of pump per time interval For the CFV-CVS system: m ed,i = 1,293 × Δt i × K V × p p / T 0,5 where: Δt i = time interval, s For the SSV-CVS system: med = 1,293 × QSSV × Δti where: Δt i = time interval, s The real time calculation shall be initialised with either a reasonable value for C d, such as 0,98, or a reasonable value of Q ssv. If the calculation is initialised with Q ssv, the initial value of Q ssv shall be used to evaluate Re. During all emissions tests, the Reynolds number at the SSV throat must be in the range of Reynolds numbers used to derive the calibration curve developed in section 2.4 of Appendix 5 to this Annex. 4.2. Determination of raw exhaust gas mass flow For calculation of the emissions in the raw exhaust gas and for controlling of a partial flow dilution system, it is necessary to know the exhaust gas mass flow rate. For the determination of the exhaust mass flow rate, either of the methods described in sections 4.2.2 to 4.2.5 may be used. 4.2.1. Response time For the purpose of emissions calculation, the response time of either method described below shall be equal to or less than the requirement for the analyzer response time, as defined in section 1.5 of Appendix 5 to this Annex. For the purpose of controlling of a partial flow dilution system, a faster response is required. For partial flow dilution systems with online control, a response time of ≤ 0,3 seconds is required. For partial flow dilution systems with look ahead control based on a pre-recorded test run, a response time of the exhaust flow measurement system of ≤ 5 seconds with a rise time of ≤ 1 second is required. The system response time shall be specified by the instrument manufacturer. The combined response time requirements for exhaust gas flow and partial flow dilution system are indicated in section 3.8.3.2. 4.2.2. Direct measurement method Direct measurement of the instantaneous exhaust flow may be done by systems such as: Precautions shall be taken to avoid measurement errors which will impact emission value errors. Such precautions include the careful installation of the device in the engine exhaust system according to the instrument manufacturers' recommendations and to good engineering practice. Engine performance and emissions shall especially not be affected by the installation of the device. The accuracy of exhaust flow determination shall be at least ± 2,5 % of reading or ± 1,5 % of engine's maximum value, whichever is the greater. 4.2.3. Air and fuel measurement method This involves measurement of the air flow and the fuel flow. Air flowmeters and fuel flowmeters shall be used that meet the total exhaust flow accuracy requirement of section 4.2.2. The calculation of the exhaust gas flow is as follows: qmew = qmaw + qmf 4.2.4. Tracer measurement method This involves measurement of the concentration of a tracer gas in the exhaust. A known amount of an inert gas (e.g. pure helium) shall be injected into the exhaust gas flow as a tracer. The gas is mixed and diluted by the exhaust gas, but shall not react in the exhaust pipe. The concentration of the gas shall then be measured in the exhaust gas sample. In order to ensure complete mixing of the tracer gas, the exhaust gas sampling probe shall be located at least 1 m or 30 times the diameter of the exhaust pipe, whichever is larger, downstream of the tracer gas injection point. The sampling probe may be located closer to the injection point if complete mixing is verified by comparing the tracer gas concentration with the reference concentration when the tracer gas is injected upstream of the engine. The tracer gas flow rate shall be set so that the tracer gas concentration at engine idle speed after mixing becomes lower than the full scale of the trace gas analyser. The calculation of the exhaust gas flow is as follows: Text of image qmew,i = qvt × ρe 60 × (cmix,i - ca) where: When the background concentration is less than 1 % of the concentration of the tracer gas after mixing (c mix.i) at maximum exhaust flow, the background concentration may be neglected. The total system shall meet the accuracy specifications for the exhaust gas flow, and shall be calibrated according to section 1.7 of Appendix 5 to this Annex. 4.2.5. Air flow and air-to-fuel ratio measurement method This involves exhaust mass calculation from the air flow and the air to fuel ratio. The calculation of the instantaneous exhaust gas mass flow is as follows: Text of image qmew,i = qmaw,i × (1 + 1 A/Fst × λi) with: Text of image A/Fst = 138,0 × (β + α 4 - ε 2 + γ) 12,011 × β + 1,00794 × α + 15,9994 × ε + 14,0067 × δ + 32,065 × γ Text of image λi = β × (100 - cCO × 10–4 2 - cHC × 10–4) + (α 4 × 1 - 2 × cCO × 10–4 3,5 × cCO2 1 + cCO × 10–4 3,5 × cCO2 - ε 2 - δ 2) × (cCO2 + cCO × 10–4) 4,764 × (β + α 4 - ε 2 + γ) × (cCO2 + cCO × 10–4 + cHC × 10–4) where: Note: β can be 1 for fuels containing carbon and 0 for hydrogen fuel. The air flowmeter shall meet the accuracy specifications of section 2.2 of Appendix 4 to this Annex, the CO2 analyser used shall meet the specifications of section 3.3.2 of Appendix 4 to this Annex and the total system shall meet the accuracy specifications for the exhaust gas flow. Optionally, air to fuel ratio measurement equipment such as a zirconia type sensor may be used for the measurement of the excess air ratio which meets the specifications of section 3.3.6 of Appendix 4 to this Annex.’ V 0 | = | 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 p 1 | = | pressure depression below atmospheric at pump inlet, kPa T | = | average temperature of the diluted exhaust gas at pump inlet over the cycle, K t | = | cycle time, s K v | = | calibration coefficient of the critical flow venturi for standard conditions, p p | = | absolute pressure at venturi inlet, kPa T | = | absolute temperature at venturi inlet, K A 0 | = | collection of constants and units conversions Text of image (m3 min) (K1 2 kPa) (1 mm2) = 0,006111 in SI units of d | = | diameter of the SSV throat, m C d | = | discharge coefficient of the SSV p p | = | absolute pressure at venturi inlet, kPa T | = | temperature at the venturi inlet, K r p | = | ratio of the SSV throat to inlet absolute, static pressure = Text of image 1 - ΔP PA rD | = | ratio of the SSV throat diameter, d, to the inlet pipe inner diameter = Text of image d D pressure differential devices, like flow nozzle, ultrasonic flowmeter, vortex flowmeter. q mew,i | = | instantaneous exhaust mass flow, kg/s q vt | = | tracer gas flow, cm3/min c mix.i | = | instantaneous concentration of the tracer gas after mixing, ppm ρ e | = | density of the exhaust gas, kg/m3 (cf. table 3) c a | = | background concentration of the tracer gas in the intake air, ppm A/F st | = | stoichiometric air to fuel ratio, kg/kg λ | = | excess air ratio c CO2 | = | dry CO2 concentration, % c CO | = | dry CO concentration, ppm c HC | = | HC concentration, ppm

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Source: EUR-Lex (Cellar) · retrieved 2026-11-10 · Text as adopted (Official Journal); later amendments are not incorporated in this text.