ANNEX VI
34.Sections 1 to 6 read as follows:
‘1.INTRODUCTION
This Annex describes the procedure for the Type IV test in accordance with section 5.3.4 of Annex I.
This procedure describes a method for a determination of the loss of hydrocarbons by evaporation from the fuel systems of vehicles with positive-ignition engines.
2.DESCRIPTION OF TEST
The evaporative emission test (Figure VI. 1) is designed to determine hydrocarbon evaporative emissions as a consequence of diurnal temperatures fluctuation, hot soaks during parking, and urban driving. The test consists of these phases:
test preparation including an urban (Part One) and extra-urban (Part Two) driving cycle,
hot soak loss determination,
diurnal loss determination.
Mass emissions of hydrocarbons from the hot soak and the diurnal loss phases are added up to provide an overall result for the test.
3.VEHICLE AND FUEL
3.1. Vehicle
3.1.1.The vehicle must be in good mechanical condition and have been run in and driven at least 3 000 km before the test. The evaporative emission control system must be connected and have been functioning correctly over this period and the carbon canister(s) must have been subject to normal use, neither undergoing abnormal purging nor abnormal loading.
3.2. Fuel
3.2.1.The appropriate reference fuel must be used, as defined in Annex IX to this Directive.
4.TEST EQUIPMENT FOR EVAPORATIVE TEST
4.1. Chassis dynamometer
The chassis dynamometer must meet the requirements of Annex III.
4.2. Evaporative emission measurement enclosure
The evaporative emission measurement enclosure must be a gas-tight rectangular measuring chamber able to contain the vehicle under test. The vehicle must be accessible from all sides and the enclosure when sealed must be gas tight in accordance with Appendix 1. The inner surface of the enclosure must be impermeable and non-reactive to hydrocarbons. The temperature conditioning system must be capable of controlling the internal enclosure air temperature to follow the prescribed temperature versus time profile throughout the test, and an average tolerance of ± 1 K over the duration of the test.
The control system must be tuned to provide a smooth temperature pattern that has a minimum of overshoot, hunting, and instability about the desired long-term ambient temperature profile. Interior surface temperatures must not be less than 278 oK (5 oC) nor more than 320 oK (55 oC) at any time during the diurnal emission test.
Wall design must be such as to promote good dissipation of heat. Interior surface temperatures must not be below 293 oK (20 oC), nor above 325 oK (52 oC) for the duration of the hot soak test.
To accommodate the volume changes due to enclosure temperature changes, either a variable-volume or fixed-volume enclosure may be used.
4.2.1. Variable-volume enclosure
The variable-volume enclosure expands and contracts in response to the temperature change of the air mass in the enclosure. Two potential means of accommodating the internal volume changes are movable panel(s), or a bellows design, in which an impermeable bag or bags inside the enclosure expand(s) and contracts(s) in response to internal pressure changes by exchanging air from outside the enclosure. Any design for volume accommodation must maintain the integrity of the enclosure as specified in Appendix 1 over the specified temperature range.
Any method of volume accommodation must limit the differential between the enclosure internal pressure and the barometric pressure to a maximum value of ± 5 hPa.
The enclosure must be capable of latching to a fixed volume. A variable volume enclosure must be capable of accommodating a ± 7 % change from its ‘nominal volume’ (see Appendix 1 section 2.1.1), taking into account temperature and barometric pressure variation during testing.
4.2.2. Fixed-volume enclosure
The fixed-volume enclosure must be constructed with rigid panels that maintain a fixed enclosure volume, and meet the requirements below.
4.2.2.1.The enclosure must be equipped with an outlet flow stream that withdrawns air at a low, constant rate from the enclosure throughout the test. An inlet flow stream may provide make-up air to balance the outgoing flow with incoming ambient air. Inlet air must be filtered with activated carbon to provide a relatively constant hydrocarbon level. Any method of volume accommodation must maintain the differential between the enclosure internal pressure and the barometric pressure between 0 and -5 hPa.
4.2.2.2.The equipment must be capable of measuring the mass of hydrocarbon in the inlet and outlet flow streams with a resolution of 0,01 gram. A bag sampling system may be used to collect a proportional sample of the air withdrawn from and admitted to the enclosure. Alternatively, the inlet and outlet flow streams may be continuously analysed using an on-line FID analyser and integrated with the flow measurements to provide a continuous record of the mass hydrocarbon removal.
4.3. Analytical systems
4.3.1. Hydrocarbon analyser
4.3.1.1.The atmosphere within the chamber is monitored using a hydrocarbon detector of the flame ionization detector (FID) type. Sample gas must be drawn from the mid-point of one side wall or roof of the chamber and any bypass flow must be returned to the enclosure, preferably to a point immediately downstream of the mixing fan.
4.3.1.2.The hydrocarbon analyser must have a response time to 90 % of final reading of less than 1,5 seconds. Its stability must be better than 2 % of full scale at zero and at 80 % ± 20 % of full scale over a 15-minute period for all operational ranges.
4.3.1.3.The repeatability of the analyser expressed as one standard deviation must be better than 1 % of full scale deflection at zero and at 80 % ± 20 % of full scale on all ranges used.
4.3.1.4.The operational ranges of the analyser must be chosen to give best resolution over the measurement, calibration and leak checking procedures.
4.3.2. Hydrocarbon analyser data recording system
4.3.2.1.The hydrocarbon analyser must be fitted with a device to record electrical signal output either by strip chart recorder or other data processing system at a frequency of at least once per minute. The recording system must have operating characteristics at least equivalent to the signal being recorded and must provide a permanent record of results. The record must show a positive indication of the beginning and end of the hot soak or diurnal emission test (including beginning and end of sampling periods along with the time elapsed between start and completion of each test).
Figure VI.1
Evaporative emission determination
4.4. Fuel tank heating (only applicable for gasoline canister load option)
4.4.1.The fuel in the vehicle tank(s) must be heated by a controllable source of heat; for example a heating pad of 2 000 W capacity is suitable. The heating system must apply heat evenly to the tank walls beneath the level of the fuel so as not to cause local overheating of the fuel. Heat must not be applied to the vapour in the tank above the fuel.
4.4.2.The tank heating device must make it possible to heat the fuel in the tank evenly by 14 oK from 289 oK (16 oC) within 60 minutes, with the temperature sensor position as in 5.1.1. The heating system must be capable of controlling the fuel temperature to ± 1,5 oK of the required temperature during the tank heating process.
4.5. Temperature recording
4.5.1.The temperature in the chamber is recorded at two points by temperature sensors which are connected so as to show a mean value. The measuring points are extended approximately 0,1 m into the enclosure from the vertical centre line of each side wall at a height of 0,9 ± 0,2 m.
4.5.2.The temperatures of the fuel tank(s) are recorded by means of the sensor positioned in the fuel tank as in 5.1.1 in the case of use of the gasoline canister load option (5.1.5).
4.5.3.Temperatures must, throughout the evaporative emission measurements, be recorded or entered into a data processing system at a frequency of at least once per minute.
4.5.4.The accuracy of the temperature recording system must be within ± 1,0 oK and the temperature must be capable of being resolved to ± 04, oK.
4.5.5.The recording or data processing system must be capable of resolving time to ± 15 seconds.
4.6. Pressure recording
4.6.1.The difference Δp between barometric pressure within the test area and the enclosure internal pressure must, throughout the evaporative emission measurements, be recorded or entered into a data processing system at a frequency of at least once per minute.
4.6.2.The accuracy of the pressure recording system must be within ± 2 hPa and the pressure must be capable of being resolved to ± 0,2 hPa.
4.6.3.The recording or data processing system must be capable of resolving time to ± 15 seconds.
4.7. Fans
4.7.1.By the use of one or more fans or blowers with the SHED door(s) open it must be possible to reduce the hydrocarbon concentration in the chamber to the ambient hydrocarbon level.
4.7.2.The chamber must have one or more fans or blowers of likely capacity 0,1 to 0,5 m3s-1 with which to thoroughly mix the atmosphere in the enclosure. It must be possible to attain an even temperature and hydrocarbon concentration in the chamber during measurements. The vehicle in the enclosure must not be subjected to a direct stream of air from the fans or blowers.
4.8. Gases
4.8.1.The following pure gases must be available for calibration and operation:
purified synthetic air (purity: < 1 ppm C1 equivalent ≤ 1 ppm CO2 ≤ 400 ppm CO2, ≤ 0,1 ppm NO); oxygen content between 18 % and 21 % by volume,
hydrocarbon analyser fuel gas (40 % ± 2 % hydrogen, and balance helium with less than 1 ppm C1 equivalent hydrocarbon, less than 400 ppm CO2),
propane (C3H8), 99,5 % minimum purity,
butane (C4H10), 98 % minimum purity,
nitrogen (N2), 98 % minimum purity.
4.8.2.Calibration and span gases must be available containing mixtures of propane (C3H8) and purified synthetic air. The true concentrations of a calibration gas must be within ± 2 % of stated figures. The accuracy of the diluted gases obtained when using a gas divider must be to within ± 2 % of the true value. The concentrations specified in Appendix 1 may also be obtained by the use of a gas divider using synthetic air as the diluent gas.
4.9. Additional equipment
4.9.1.The absolute humidity in the tests area must be measurable to within ± 5 %.
5.TEST PROCEDURE
5.1. Test preparation
5.1.1.The vehicle is mechanically prepared before the test as follows:
the exhaust system of the vehicle must not exhibit any leaks,
the vehicle may be steam cleaned before the test,
in the case of use of the gasoline canister load option (5.1.5) the fuel tank of the vehicle must be equipped with a temperature sensor to enable the temperature to be measured at the mid-point of the fuel in the fuel tank when filled to 40 % of its capacity,
additional fittings, adapters of devices may be fitted to the fuel system in order to allow a complete draining of the fuel tank. For this purpose it is not necessary to modify the shell of the tank,
the manufacturer may propose a test method in order to take into account the loss of hydrocarbons by evaporation coming only from the fuel system of the vehicle.
5.1.2.The vehicle is taken into the test area where the ambient temperature is between 293 oK and 303 oK (20 and 30 oC).
5.1.3.The ageing of the canister(s) has to be verified. This may be done by demonstrating that it has accumulated a minimum of 3 000 km. If this demonstration is not given, the following procedure is used. In the case of a multiple canister system each canister must undergo the procedure separately.
5.1.3.1.The canister is removed from the vehicle. Special care must be taken during this step to avoid damage to components and the integrity of the fuel system.
5.1.3.2.The weight of the canister must be checked.
5.1.3.3.The canister is connected to a fuel tank, possibly an external one, filled with reference fuel, to 40 % volume of the fuel tank(s).
5.1.3.4.The fuel temperature in the fuel tank must be between 283 oK (10 oC) and 287 oK (14 oC).
5.1.3.5.The (external) fuel tank is heated from 288 oK to 318 oK (15 o to 45 oC) (1 oC increase every 9 minutes).
5.1.3.6.If the canister reaches breakthrough before the temperature reaches 318 oK (45 oC), the heat source must be turned off. Then the canister is weighed. If the canister did not reach breakthrough during the heating to 318 oK (45o oC), the procedure from 5.1.3.3 must be repeated until breakthrough occurs.
5.1.3.7.Breakthrough may be checked as is described in 5.1.5 and 5.1.6 of this Annex, or with the use of another sampling and analytical arrangement capable of detecting the emission of hydrocarbons from the canister at breakthrough.
5.1.3.8.The canister must be purged with 25 ± 5 litres per minute with the emission laboratory air until 300 bed volume exchanges are reached.
5.1.3.9.The weight of the canister must be checked.
5.1.3.10.The steps of the procedure in 5.1.3.4 to 5.1.3.9 must be repeated nine times. The test may be terminated prior to that, after not less than three ageing cycles, if the weight of the canister after the last cycles has stabilized.
5.1.3.11.The evaporative emission canister is reconnected and the vehicle restored to its normal operating condition.
5.1.4.One of the methods specified in 5.1.5 and 5.1.6 must be used to precondition the evaporative canister. For vehicles with multiple canisters, each canister must be preconditioned separately.
5.1.4.1.Canister emissions are measured to determine breakthrough.
Breakthrough is here defined as the point at which the cumulative quantity of hydrocarbons emitted is equal to 2 grams.
5.1.4.2.Breakthrough may be verified using the evaporative emission enclosure as described in 5.1.5 and 5.1.6 respectively. Alternatively, breakthrough may be determined using an auxiliary evaporative canister connected downstream of the vehicle's canister. The auxiliary canister must be well purged with dry air prior to loading.
5.1.4.3.The measuring chamber must be purged for several minutes immediately before the test until a stable background is obtained. The chamber air mixing fan(s) must be switched on at this time.
The hydrocarbon analyser must be zeroed and spanned immediately before the test.
5.1.5. Canister loading with repeated heat builds to breakthrough
5.1.5.1.The fuel tank(s) of the vehicle(s) is (are) emptied using the fuel tank drain(s). This must be done so as not to abnormally purge or abnormally load the evaporative control devices fitted to the vehicle. Removal of the fuel cap is normally sufficient to achieve this.
5.1.5.2.The fuel tank(s) is (are) refilled with test fuel at a temperature of between 283 oK to 287 oK (10 to 14 oC) to 40 % ± 2 % of the tank's normal volumetric capacity. The fuel cap(s) of the vehicle must be fitted at this point.
5.1.5.3.Within one hour of being refuelled the vehicle must be placed, with the engine shut off, in the evaporative emission enclosure. The fuel tank temperature sensor is connected to the temperature recording system. A heat source must be properly positioned with respect to the fuel tank(s) and connected to the temperature controller. The heat source is specified in 4.4. In the case of vehicles fitted with more than one fuel tank, all the tanks must be heated in the same way as described below. The temperatures of the tanks must be identical to within ± 1,5 oK.
5.1.5.4.The fuel may be artificially heated to the starting diurnal temperature of 293 oK (20 oC) ± 1 oK.
5.1.5.5.When the fuel temperature reaches at last 292 oK (19 oC), the following steps must be taken immediately: the purge blower must be turned off; enclosure doors closed and sealed; and measurement initiated of the hydrocarbon level in the enclosure.
5.1.5.6.When the fuel temperature of the fuel tank reaches 293 oK (20 oC) a linear heat build of 15 oK (15 oC) begins. The fuel must be heated in such a way that the temperature of the fuel during the heating conforms to the function below to within ± 1,5 oK. The elapsed time of the heat build and temperature rise is recorded.
Tr = T0 + 0,2333 x t
where:
=
required temperature (K);
=
initial temperature (K);
=
time from start of the tank heat build in minutes.
5.1.5.7.As soon as breakthrough occurs or when the fuel temperature reaches 308 oK (35 oC), whichever occurs first, the heat source is turned off, the enclosure doors unsealed and opened, and the vehicle fuel tank cap(s) removed. If breakthrough has not occurred by the time the fuel temperature 308 oK (35 oC), the heat source is removed from the vehicle, the vehicle removed from the evaporative emission enclosure and the entire procedure outlined in 5.1.7 repeated until breakthrough occurs.
5.1.6. Butane loading to breakthrough
5.1.6.1.If the enclosure is used for the determination of the breakthrough (see 5.1.4.2) the vehicle must be placed, with the engine shut off, in the evaporative emission enclosure.
5.1.6.2.The evaporative emission canister must be prepared for the canister loading operation. The canister must not be removed from the vehicle, unless access to it in its normal location is so restricted that loading can only reasonably be accomplished by removing the canister from the vehicle. Special care must be taken during this step to avoid damage to the components and the integrity of the fuel system.
5.1.6.3.The canister is loaded with a mixture composed of 50 % butane and 50 % nitrogen by volume at a rate of 40 grams butane per hour.
5.1.6.4.As soon as the canister reaches breakthrough, the vapour source must be shut off.
5.1.6.5.The evaporative emission canister must then be reconnected and the vehicle restored to its normal operating condition.
5.1.7. Fuel drain and refill
5.1.7.1.The fuel tank(s) of the vehicle(s) is (are) emptied using the fuel tank drain(s). This must be done so as not to abnormally purge or abnormally load the evaporative control devices fitted to the vehicle. Removal of the fuel cap is normally sufficient to achieve this.
5.1.7.2.The fuel tank(s) is (are) refilled with test fuel at a temperature of between 291 oK ± 8 oK (18 ± 8 oC) to 40 ± 2 % of the tank's normal volumetric capacity. The fuel cap(s) of the vehicle must be fitted at this point.
5.2. Preconditioning drive
5.2.1.Within one hour from the completing of canister loading in accordance with 5.1.5 or 5.1.6 the vehicle is placed on the chassis dynamometer and driven through one Part One and two Part Two driving cycles of Type I test as specified in Annex III. Exhaust emissions are not sampled during this operation.
5.3. Soak
5.3.1.Within five minutes of completing the preconditioning operation specified in 5.2.1 the engine bonnet must be completely closed and the vehicle driven off the chassis dynamometer and parked in the soak area. The vehicle is parked for a minimum of 12 hours and a maximum of 36 hours. The engine oil and coolant temperatures must have reached the temperature of the area or within ± 3 oK of it at the end of the period.
5.4. Dynamometer test
5.4.1.After conclusion of the soak period the vehicle is driven through a complete Type I test drive as described in Annex III (cold start urban and extra urban test). Then the engine is shut off. Exhaust emissions may be sampled during this operation but the results must not be used for the purpose of exhaust emission type-approval.
5.4.2.Within two minutes of completing the Type I test drive specified in 5.4.1 the vehicle is driven a further conditioning drive consisting of one urban test cycle (hot start) of a Type I test. Then the engine is shut off again. Exhaust emissions need not be sampled during this operation.
5.5. Hot soak evaporative emissions test
5.5.1.Before the completion of the conditioning drive the measuring chamber must be purged for several minutes until a stable hydrocarbon background is obtained. The enclosure mixing fan(s) must also be turned on at this time.
5.5.2.The hydrocarbon analyser must be zeroed and spanned immediately prior to the test.
5.5.3.At the end of the conditioning drive the engine bonnet must be completely closed and all connections between the vehicle and the test stand disconnected. The vehicle is then driven to the measuring chamber with a minimum use of the accelerator pedal. The engine must be turned off before any part of the vehicle enters the measuring chamber. The time at which the engine is switched off is recorded on the evaporative emission measurement data recording system and temperature recording begins. The vehicle's windows and luggage compartments must be opened at this stage, if not already opened.
5.5.4.The vehicle must be pushed or otherwise moved into the measuring chamber with the engine switched off.
5.5.5.The enclosure doors are closed and sealed gas-tight within two minutes of the engine being switched off and within seven minutes of the end of the conditioning drive.
5.5.6.The start of a 60 ± 0,5 minute hot soak period begins when the chamber is sealed. The hydrocarbon concentration, temperature and barometric pressure are measured to give the initial readings CHC,i Pi and Ti for the hot soak test. These figures are used in the evaporative emission calculation, section 6. The ambient SHED temperature T must not be less than 296 oK and no more than 304 oK during the 60-minute hot soak period.
5.5.7.The hydrocarbon analyser must be zeroed and spanned immediately before the end of the 60 ± 0,5 minute test period.
5.5.8.At the end of the 60 ± 0,5 minute test period the hydrocarbon concentration in the chamber must be measured. The temperature and the barometric pressure are also measured. These are the final readings CHC,f, Pf and Tf for the hot soak test used for the calculation in section 6.
5.6. Soak
5.6.1.The test vehicle must be pushed or otherwise moved to the soak area without use of the engine and soaked for not less than 6 hours and not more than 36 hours between the end of the hot soak test and the start of the diurnal emission test. For at least 6 hours of this period the vehicle must be soaked at 293 oK ± 2 oK (20 oC ± 2 oC).
5.7. Diurnal test
5.7.1.The test vehicle must be exposed to one cycle of ambient temperature according to the profile specified in Appendix 2 with a maximum deviation of ± 2 oK at any time. The average temperature deviation from the profile, calculated using the absolute value of each measured deviation, must not exceed 1 oK. Ambient temperature must be measured at least every minute. Temperature cycling begins when time tstart = 0, as specified in 5.7.6.
5.7.2.The measuring chamber must be purged for several minutes immediately before the test until a stable background is obtainable. The chamber mixing fan(s) must also be switched on at this time.
5.7.3.The test vehicle, with the engine shut off and the test vehicle windows and luggage compartment(s) opened must be moved into the measuring chamber. The mixing fan(s) must be adjusted in such a way as to maintain a minimum air circulation of 8 km/h under the fuel tank of the test vehicle.
5.7.4.The hydrocarbon analyser must be zeroed and spanned immediately before the test.
5.7.5.The enclosure doors must be closed and gas-tight sealed.
5.7.6.Within 10 minutes of closing and sealing the doors, the hydrocarbon concentration, temperature and barometric pressure are measured to give the initial readings CHC,i, Pf and Tf for the diurnal test. This is the point where time tStart = 0.
5.7.7.The hydrocarbon analyser must be zeroed and spanned immediately before the end of the test.
5.7.8.The end of the emission sampling period occurs 24 hours ± 6 minutes after the beginning of the initial sampling, as specified in 5.7.6. The time elapsed is recorded. The hydrocarbon concentration, temperature and barometric pressure are measured to give the final readings CHC,i, Pf and Tf for the diurnal test used for the calculation in section 6. This completes the evaporative emission test procedure.
6.CALCULATION
6.1.The evaporative emission tests described in section 5 allow the hydrocarbon emissions from the diurnal and hot soak phases to be calculated. Evaporative losses from each of theses phases is calculated using the initial and final hydrocarbon concentrations, temperatures and pressures in the enclosure, together with the net enclosure volume.
The formula below is used:
where:
=
hydrocarbon mass in grams
=
mass of hydrocarbon exiting the enclosure, in the case of fixed-volume enclosures for diurnal emission testing (grams).
=
mass of hydrocarbon entering the enclosure, in the case of fixed-volume enclosures for diurnal emission testing (grams).
=
measured hydrocarbon concentration in the enclosure (ppm (volume) C1 equivalent),
=
net enclosure volume in cubic metres corrected for the volume of the vehicle, with the windows and the luggage compartment open. If the volume of the vehicle is not determined a volume of 1,42 m3 is subtracted.
=
ambient chamber temperature, in oK,
=
barometric pressure in kPA,
=
hydrogen to carbon ration,
=
1,2 · (12 + H/C);
where:
is the initial reading,
is the final reading,
is taken to be 2,33 for diurnal test losses,
is taken to be 2,20 for hot soak losses.
6.2. Overall results of test
The overall hydrocarbon mass emission for the vehicle is taken to be:
Mtotal = MDI + MHS
where:
=
overall mass emissions of the vehicle (grams),
=
HYDROCARBON MASS EMISSION FOR DIURNAL TEST (GRAMS),
=
HYDROCARBON MASS EMISSION FOR THE HOT SOAK (GRAMS).’