NOx Emissions below the Prospective EURO VII Limit on a Retrofitted Heavy-Duty Vehicle

Abstract

In this study, a EURO VI heavy-duty vehicle (HDV) has been retrofitted with an exhaust gas heater (EGH) with the objective to reduce its NOx emissions below the current EURO VI and EURO VII limits. Results show that an EGH of 5 kW is enough to produce a significant NOx emissions abatement below the EURO VI and EURO VII limits. A conventional after-treatment system heated using a 5 kW EGH could work at its maximum catalytic conversion efficiency of 95% regardless of the engine operating speed. Consequently, exhaust gas heaters are a potential solution to high NOx emission at low engine regimes. With the use of an EGH, urea can be injected sooner, and catalytic reactions could cut much more NOx emissions. However, its incorporation would increase the vehicle’s fuel consumption by 1.47% if it is connected directly to the vehicle’s electrical system. Finally, it is also demonstrated that an automotive thermoelectric generator (ATEG) can supply the energy required by the EGH through the conversion of the waste heat from exhaust gases into electricity. This system could work electrically autonomous so there is no extra consumption of fuel.