UN R49 — Supplement 12 to the 05 series of amendments

Tables A and B of paragraph 1.1. now have H2 columns under positive-ignition engines and under compression-ignition engines. New footnote f of Table B says that the measurement of CH4 and CO2 is not required. Footnote f also lets the manufacturer, technical service or Type Approval Authority measure THC instead of non-methane hydrocarbons. The definition of “gas engine” (para. 2.1.37.) now includes positive-ignition engines fuelled with H2. In an application for type approval of hydrogen engines, hydrogen must be the fuel the engine is designed to run on primarily (para. 3.5.1.). Requirements for dual-fuel hydrogen engines are not yet established under this Regulation.

For hydrogen fuelled engines, new paragraph 4.6.3.3. requires one or more letters after the national symbol in the approval mark. The letters distinguish the fuel type and the working principle for which the approval was granted. 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. The Annex 1 information document and the Annex 2A communication now list hydrogen fuels with the letters T, TD, U and UD, for example “Hydrogen (TD)”.

New paragraph 4. of Annex 5 gives the technical data of the hydrogen reference fuels for testing compression-ignition or positive ignition engines. The new table gives limits, for example 99.97 per cent mole fraction for the hydrogen fuel index and 300 μmol/mol for total non-hydrogen gases. Paragraph 4.1.1. now also applies to hydrogen fuel: the parent engine meets the requirements on the reference fuel specified in Annex 5. New paragraph 8.3.2.6. lets conformity of production tests of hydrogen fuelled engines use the applicable market fuels. At the manufacturer’s request, the reference fuels described in Annex 5 may be used. Paragraph 2.2.5. now also lists the standard ISO 14687-2019 “Hydrogen fuel quality – Product specification”.

Under paragraph 5.1.10.1., in a type approval of hydrogen engines, the emission measurement system must comply with the highest exhaust water content expected during testing. For hydrogen engines, sample gas carrying components, except sample dryers, must stay at least 10 K above the local sample gas dew point. New note b of Table 1 says that the smoke limit does not apply to engines fuelled with hydrogen as shown in paragraph 4.6.3.3. New note d of Table 2 covers engines where all the fuels used have a molar carbon to hydrogen ratio of 0. For these engines, the measurement of CH4 is not required, and THC may be measured instead of non-methane hydrocarbons with the same limit. Annexes 2A and 2B have a new footnote with the same text as note d.

Paragraph 2.2.4. now says that the molar carbon ratio β is 1 for carbon based fuels and 0 for hydrogen fuel. In Annex 4A, the formulas for the stoichiometric air to fuel ratio and for λi now include β. Appendix 6, paragraph 2.4., has a new molecular mass formula with β, and the molar ratios refer to a fuel Cβ Hα Oδ Nε Sγ. If one of the fuels used has a molar carbon to hydrogen ratio of 0, λi and some dry/wet correction formulas do not apply. Appendix 1, paragraph 5., has a new list of fuel molar ratios, with H2 for hydrogen. Table 6 has new ugas values for hydrogen in raw exhaust.

The CO analyzer interference check of Annex 4A, Appendix 5, has a new limit for the analyzer response. The response must not be more than 2 per cent of the mean CO concentration expected during testing or 20 ppm, whichever is larger. Before this supplement, the limit was 1 per cent of full scale for ranges at or above 300 ppm, or 3 ppm below 300 ppm. Appendix 2 now also requires the ETC test run-in for hydrogen fuelled engines, not only for NG and LPG fuelled engines. For a hydrogen fuelled engine test, the carbon flow check should be done on a diesel fuelled engine before the hydrogen engine is installed.

In Annex 1, several items now say “compression-ignition (C.I.)” and “positive-ignition (P.I.)” instead of “diesel” and “gas”. In Annex 1, Appendix 1, the C.I./P.I. wording is in paragraph 9.3.1.; a RegVault Note, not part of the official text, explains this placement. Paragraphs 7.2.1. and 7.2.2. and the OBD requirements of Annex 9A now say “CI” and “PI” engines instead of “diesel” and “gas” engines. In the monitoring tables of Annex 9B, Appendix 3, “Diesel” and “Gas” become “CI engine” and “PI engine”. The low fuel level table of Annex 9B now uses “Liquid fuel storage” and “Gaseous fuel storage”, not “Diesel” and “Gas”. Annex 9B also adds the abbreviations CI and PI, and the DPF abbreviation now includes other soot particle filters.