- average gas ratio
means the average Gas Energy Ratio calculated over a driving cycle;
- diesel mode
means the normal operating mode of a dual-fuel engine during which the engine does not use any gaseous fuel for any engine operating condition;
- dual-fuel engine
means an engine system that is designed to simultaneously operate with diesel fuel and a gaseous fuel, both fuels being metered separately, where the consumed amount of one of the fuels relative to the other one may vary depending on the operation;
- dual-fuel mode
means the normal operating mode of a dual-fuel engine during which the engine simultaneously uses diesel fuel and a gaseous fuel at some engine operating conditions;
- dual-fuel vehicle
means a vehicle that is powered by a dual-fuel engine and that supplies the fuels used by the engine from separate on-board storage systems;
- Gas Energy Ratio (GER)
means in case of a dual-fuel engine, the energy content of the gaseous fuel divided by the energy content of both fuels (diesel and gaseous), expressed as a percentage, the energy content of the fuels being defined as the lower heating value;
- qualified deteriorated component or system
(hereinafter “QDC”) means a component or system that has been intentionally deteriorated such as by accelerated ageing or by having been manipulated in a controlled manner and which has been accepted by the approval authority in accordance with the provisions set out in Annex 9B to UN/ECE Regulation No 49 for use when demonstrating the OBD performance of the engine system;’;
- service mode
means a special mode of a dual-fuel engine that is activated for the purpose of repairing, or of moving the vehicle from the traffic when operation in the dual-fuel mode is not possible;
- type 1A dual-fuel engine
means a dual-fuel engine that operates over the hot part of the WHTC test-cycle with an average gas ratio that is not lower than 90 per cent (GERWHTC ≥ 90 %), and that does not idle using exclusively diesel fuel, and that has no diesel mode;
- type 1B dual-fuel engine
means a dual-fuel engine that operates over the hot part of the WHTC test-cycle with an average gas ratio that is not lower than 90 per cent (GERWHTC ≥ 90 %), and that does not idle using exclusively diesel fuel in dual-fuel mode, and that has a diesel mode;
- type 2A dual-fuel engine
means a dual-fuel engine that operates over the hot part of the WHTC test-cycle with an average gas ratio between 10 per cent and 90 per cent (10 % < GERWHTC < 90 %) and that has no diesel mode or that operates over the hot part of the WHTC test-cycle with an average gas ratio that is not lower than 90 per cent (GERWHTC ≥ 90 %), but that idles using exclusively diesel fuel, and that has no diesel mode;
- type 2B dual-fuel engine
means a dual-fuel engine that operates over the hot part of the WHTC test-cycle with an average gas ratio between 10 per cent and 90 per cent (10 % < GERWHTC < 90 %) and that has a diesel mode or that operates over the hot part of the WHTC test-cycle with an average gas ratio that is not lower than 90 per cent (GERWHTC ≥ 90 %), but that can idle using exclusively diesel fuel in dual-fuel mode, and that has a diesel mode;
- type 3B dual-fuel engine
means a dual-fuel engine that operates over the hot part of the WHTC test-cycle with an average gas ratio that does not exceed 10 per cent (GERWHTC ≤ 10 %) and that has a diesel mode.’;
- Wobbe index (lower Wl or upper Wu)
means the ratio of the corresponding calorific value of a gas per unit volume and the square root of its relative density under the same reference conditions: WHgasρgasρair Which can also be expressed as WHgasρairρgas