Fuel-Independent exhaust emission indices and equivalent limits up to Euro 7 with application to CFD combustion modelling

• Two emission indices are proposed: per kg of fuel and per kg of CO 2 . • The new indices are ideal in CFD emission studies as they don’t require engine power. • Facilitating studies on pollutant emissions that do not rely on experimental methods. • A validated equation to convert the standardised emission limits into the new ones. • The emission limits for the proposed indices don’t depend on the fuel nature. The primary purpose of the present work is to support alternative fuels in meeting pollutant emissions regulations. To reach this target, two complementary emission indices to the one utilised in Euro V-VI-7 are proposed: per kg of fuel and per kg of CO 2 , instead of per kWh; the main reason is that it would be ideal to pave the way of numerical simulations (CFD) or analytical methods to determine the pollutant emissions of several fuels used in the same engine, because the CFD in the combustion chamber is unable to assess kW of final engine power (delivered power). This research presents a procedure for determining the new indices, in line with the methodology of the latest review of the UN Regulation, and establishes their equivalent limits to those of the Euro-V, Euro-VI, and Euro-7 standards. These limits are deduced through two independent paths: one experimental and the other based on an equation; in this way, an easy algebraic expression to translate exhaust pollutant emission limits has been validated using advanced biofuels and their blends with diesel fuel. Experimental results confirm that the equivalent limits do not depend on the type of fuel, despite the fact that the total exhaust pollutant emissions and the engine efficiency produced vary with the fuel nature. It has been observed that emissions are strongly dependent on the relationship LHV ∼ A / F , as well as on the Cetane Number. The standardised pollutant exhaust emission limits for Euro V-VI and Euro 7 (vehicles of categories M2, M3, N2 and N3) are presented, expressed per kg of fuel and per kg of CO 2 .