UN R49 — Supplement 2 to the 07 series of amendments

New paragraph 3.5. covers applications for type approval of engines fuelled with hydrogen. Hydrogen must be the fuel the engine is designed to run on primarily. Requirements for dual-fuel hydrogen engines have not yet been established under this Regulation. Paragraph 4.6.2. now names grade D (type I or II) of ISO standard ISO 14687 for hydrogen. Paragraph 8.3.3.3. adds hydrogen to the fuels for which all these tests may be conducted with the applicable market fuels. Annex 5 has new technical data for the fuel type hydrogen, with a limit of 99.97 % mole fraction for the hydrogen fuel index.

New paragraph 4.12.3.3.8. requires letters after the national symbol in the approval mark of hydrogen fuelled engines. For an engine approved and calibrated for gaseous hydrogen, the letter is T for a PI engine and TD for a CI engine. For an engine approved and calibrated for liquefied hydrogen, the letter is U for a PI engine and UD for a CI engine. Table 2 of Annex 3 refers hydrogen fuelled engines to paragraph 4.12.3.3.8. Annex 1 adds Hydrogen (T), Hydrogen (TD), Hydrogen (U) and Hydrogen (UD) to the fuel entries in paragraphs 3.2.2.2. and 3.2.17.1. The addenda to Annexes 2A, 2B and 2C add the same entries to the category of engine in paragraph 1.1.5.

New paragraph 5.1.6.1. requires that the emission measurement system for hydrogen engines complies with the highest exhaust water content expected during emission testing. All sample gas carrying components, except for sample dryers, must stay at least 10 K above the sample gas dew point at their position. Paragraph 5.2.3.6. adds hydrogen to the fuel types, and paragraph 8. adds H2 for hydrogen to the molar ratios of the fuel. The fuel composition is now CβHαOεNδSγ, with β=1 for fuels containing carbon and β=0 for fuels with a molar carbon to hydrogen ratio of 0. Table 5 has new u values for hydrogen. For a hydrogen fuelled engine, the carbon flow check should be performed on a diesel fuelled engine before the hydrogen fuelled engine is installed.

Equations 15, 18, 19 and 32 are not applicable if one of the fuels used has a molar carbon to hydrogen ratio of 0. Equations 13 to 17 are not applicable in the case that water injection is used. Equations 31, 32 and 41 now include the molar carbon ratio β, and λi is calculated by equation 32 or measured by a lambda sensor. 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 sentence that required the air flow meter, analyzers and total system to meet the linearity requirements of paragraph 9.2. is removed. The requirement for air to fuel ratio measurement equipment such as a zirconia type sensor (9.3.2.7.) is also removed.

A new note to Table 1 in paragraph 5.3. 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 NMHC, with the NMHC limit. Similar notes in the test result tables of the addenda to Annexes 2A, 2B and 2C also say that CO2 measurement is not required. Annex 6 does not apply to engines and vehicles where all of the fuels used have a molar carbon to hydrogen ratio of 0. New Annex 12 paragraph 3.3. sets the CO2 mass to zero if all fuels used have this ratio of 0; former 3.3. is now 3.4. In Annex 9A Table 2, the CO OTL for positive ignition engines is not applicable if this ratio of all the fuel used is 0.

The CO2 mass based method may be omitted if at least one fuel used has a molar carbon to hydrogen ratio of 0 (6.2.). The pass/fail decision is still made on the basis of the results of the work based method. Several CO2 entries (10.1.8.4. to 10.1.12.4.) now add conditions on the molar carbon to hydrogen ratio of the fuels used. The CH4 mass entry (10.1.9.5.) is now for natural gas fuelled engines only, instead of P.I. engines only. For engines where all the fuels used have this ratio of 0, the manufacturer may choose to measure only THC, CO, NOX and PM number. In this case, lambda and optionally air mass flow must be measured as well to enable the data consistency check.

Paragraph A.7.2.1. now covers a “Laser Infrared Analyser” instead of a “Laser Diode Spectrometer (LDS)”. The sample path of the cabinet-installed laser analyser and of the FTIR is now heated to set points between 383 and 464 K. Before this supplement, it was heated to 463 ± 10 K. Paragraph 8.2. says that equation D.15 in Annex D to ISO Standard 8178-4:2020 should be used to calculate the saturation vapour pressure. Table 7 adds linearity requirements for the humidity measurement device. The CO analyser interference check (9.3.9.1.) now limits the response to 2 % of the mean expected CO concentration or 20 ppm, whichever is larger.