Fuel Consumption and Emission Reduction for Non-Road Diesel Engines with Electrically Heated Catalysts

Abstract

In this study, an exhaust system compliant with future regulations was developed for a non-road 110PS engine with a Tier-4f aftertreatment system, and the emission characteristics of the engine were investigated in the non-road transient mode (NRTC). For the system to comply with future exhaust regulations, a DPF was installed, and an electrical heated catalyst (EHC) device was installed to manage exhaust gas temperature. The emission characteristics of exhaust gas were examined according to the power and applied duration of EHC, and the effects of catalyst coating and the urea water solution (UWS) injection map on NOx reduction, NH3 slip, and N2O emissions in NRTC mode were investigated. The application of a 4 kW class EHC system enables the lowering of the injection starting temperature of the UWS, as reliable gas heating (heating duration control) is guaranteed. When the injection starting temperature (based on the SCR inlet temperature) was set to 150 °C, NSR map, (III) in conjunction with the operation of the EHC, effectively achieved significant NOx reduction in NRTC mode without deposit and wetting occurring in the mixer and exhaust pipe. Regarding changes in EHC power from 3 kW to 4 kW, it was observed that a NOx reduction of 0.05 g/kWh occurs in the cold NRTC mode, but in the hot NRTC mode, it was found that the relative decrease in the UWS is due to the increased NO2 conversion efficiency as a result of the oxidation catalyst, making 3 kW more advantageous. Furthermore, due to the increase in NO2 concentration caused by the oxidation catalyst and the increase in the low-temperature injected UWS, NH4NO3 was formed, which resulted in an increase in PM emissions and a significant increase in N2O emissions around an exhaust temperature of 250 °C. When the EHC power was set to 3 kW and the volume of oxidation catalyst and the amount of UWS injection were adjusted, applying EHC in the NRTC mode resulted in an additional NOx reduction of 58.6% and 88.4% in cold and hot modes, respectively, compared with not using EHC, with a fuel penalty of approximately 1.67%, while limiting the peak concentrations of N2O and NH3.

Variable Valve Actuation for Efficient Exhaust Thermal Management in an Off-Road Diesel Engine

“…Regulation can influence the configuration of integrated EATS. For example, EPA Tier 4 final regulations in North America do not restrict the number of particulate matters (PN-particle number), so DPFs are less common [14]. Instead, the EPA regulation focus on enhancing the effectiveness of DOCs to address emissions concerns [14].…”

“…For example, EPA Tier 4 final regulations in North America do not restrict the number of particulate matters (PN-particle number), so DPFs are less common [14]. Instead, the EPA regulation focus on enhancing the effectiveness of DOCs to address emissions concerns [14]. Conversely, DPFs are becoming widespread in Europe to comply with new restriction of particle number (PN) in EU Stage-V regulations.…”

“…Specifically, PM conversion efficiency decreased by 31 % compared to the hot cycle, exceeding China-IV PM standards. Notably, it took approximately 400 ~ 500 s for the SCR catalyst temperature to attain 200 • C in the NRTC cold mode [14]. This time constitutes one-third of the entire mode duration, so it exerted a substantial influence on NO x emissions.…”