UN R49 — Supplement 9 to the 06 series of amendments

In an application for type approval of hydrogen engines, hydrogen must be the fuel the engine is designed to run on primarily. Requirements for dual-fuel hydrogen engines are not yet established under this Regulation. Paragraph 4.6.2. now also names grade D (type I or II) of ISO standard ISO 14687, in the case of hydrogen. Under paragraph 8.3.3.3., tests of hydrogen fuelled engines may be conducted with the applicable market fuels. At the manufacturer’s request, the reference fuels described in Annex 5 may be used. Annex 5 has a new fuel type “Hydrogen”, with limits such as 99.97 per cent mole fraction for the hydrogen fuel index.

For hydrogen fuelled engines, new paragraph 4.12.3.3.8. requires letters after the national symbol in the approval mark to show the fuel type and working principle. T is for a PI engine and TD for a CI engine approved and calibrated for gaseous hydrogen. U is for a PI engine and UD for a CI engine approved and calibrated for liquefied hydrogen. Annex 1 and the addenda to Annexes 2A and 2C now list Hydrogen (T), Hydrogen (TD), Hydrogen (U) and Hydrogen (UD). Table 2 of Annex 3 has a new row “Hydrogen fuelled engine” that refers to paragraph 4.12.3.3.8. The fuel type list of Annex 4, paragraph 5.2.3.6., now has (e) Petrol and (f) Hydrogen.

For type approval of hydrogen engines, the emission measurement system must comply with the highest exhaust water content expected during emission testing (para. 5.1.6.1.). The temperatures of all sample gas carrying components, except sample dryers, must stay at least 10 K above the local sample gas dew point. New note *** of Table 1 (para. 5.3.) applies to engines where all the fuels used have a molar carbon to hydrogen ratio of 0. For these engines, CH4 measurement is not required, and THC may be measured instead of NMHC, with the same limit. The WHSC and WHTC tables in the addenda to Annexes 2A and 2C have a similar new note ***. Annex 6 now does not apply to engines and vehicles where all of the fuels used have a molar carbon to hydrogen ratio of 0.

Annex 4 adds the molar carbon ratio β: 1 for fuels containing carbon, 0 for fuels with a molar carbon to hydrogen ratio of 0. Equations (31), (32) and (41) now include β, and paragraph 8. of Annex 4 now lists H2 for hydrogen. Equations 15, (18), (19) and (32) are not applicable if one of the fuels used has a molar carbon to hydrogen ratio of 0. For hydrogen engines, the carbon balance method of paragraph 8.4.1.7. must not be applied to determine the exhaust gas mass flow. The sentences on air flow meter and analyzer linearity and on air to fuel ratio measurement equipment, such as a zirconia type sensor, were deleted. If all fuels used have a molar carbon to hydrogen ratio of 0, new paragraph 3.3. of Annex 12 sets the CO2 mass to zero.

The CO analyser interference limit is 2 per cent of the mean CO concentration expected during testing or 20 ppm, whichever is larger. To test a hydrogen fuelled engine, the carbon flow check should be done on a diesel fuelled engine before the hydrogen engine is installed. Appendix 7 now covers a “Laser Infrared Analyser” instead of a “Laser Diode Spectrometer (LDS)”. Its infrared laser can be, for example, a tunable diode laser (TDL) or a quantum cascade laser (QCL). For the laser analyser in an analyser cabinet and for the FTIR, the sample path must be heated to between 383 and 464 K. Before, the value was 463 ± 10 K.

Under paragraph 6.2., the CO2 mass based method may be omitted if at least one fuel has a molar carbon to hydrogen ratio of 0. Many CO2 items, for example 10.1.9.4. and 10.1.9.20., now have a condition on the molar carbon to hydrogen ratio of the fuels used. Item 10.1.1.11. adds hydrogen as a type of engine, and item 10.1.9.5. now asks for the CH4 mass for natural gas fuelled engines only. If all fuels have a molar carbon to hydrogen ratio of 0, the manufacturer may choose to measure only THC, CO, NOx and PM number. Lambda and optionally air mass flow must then be measured as well, to enable the data consistency check. If all fuels have a molar carbon to hydrogen ratio of 0, the data consistency check uses the formula in paragraph 8.4.1.6. of Annex 4.

The CO OTL for PI engines (Annex 9A, Table 2) does not apply if all fuel has a molar carbon to hydrogen ratio of 0. In the monitoring tables of Annex 9B, Appendix 3, the columns “Diesel” and “Gas” become “CI engine” and “PI engine”. The low fuel level table of Annex 9B, paragraph 5.2.3., now uses the columns “Liquid fuel storage” and “Gaseous fuel storage”. Annex 9B adds the abbreviations CI and PI, and the DPF abbreviation now includes other soot particle filters.