Interactions between aftertreatment systems architecture and combustion of oxygenated fuels for improved low temperature catalysts activity

Abstract

Diesel engine vehicles, despite their good fuel economy and reduced CO2, are receiving significant attention and negative publicity in recent years due to their difficulties in achieving the emissions regulations. This has widely been linked to undesirable environmental impact and health effects.The lower exhaust gas temperatures associated with modern and more efficient hybrid powertrain and diesel engines makes current technology catalytic aftertreatment systems less efficient under range of vehicle operating conditions. This study, demonstrates how changes in the commonly used aftertreatment system architecture and changes in fuel composition in this case through the addition of oxygenated fuels (i.e. butanol) in diesel fuel can provide meaningful low temperature catalyst activity improvements.The catalyst oxidation kinetics of CO and HC species were improved (reduced the light-off temperature by around 20 °C) when a diesel particulate filter (DPF) was placed upstream of the DOC, while the combination of DPF and combustion of oxygenated fuel in diesel led to up to 80 °C improvement in catalyst activity. The prevention of soot reaching the DOC active sites increases the rate of reactions and the species accessibility to the active sites of the catalyst, and thereby the oxidation of emissions (CO, HC, and NO) can occur at lower catalyst temperatures. The combustion of diesel-butanol blend further improved the DOC low temperature activity. The major contributors to the improved catalyst light-off, are the reduced level of soot and hydrocarbon emissions as well as the higher reactivity of the hydrocarbons species emitted under butanol blend combustion.

Investigation of the impact of injection timing and pressure on emissions characteristics and smoke/soot emissions in diesel engine fuelling with soybean fuel

“…The increment in EGT was observed with late injection timing (45 aTDC) as shown in Figure 2. It is reported in previous works (Wu, 2018;Fayad, 2018) that late-cycle postinjection is one of the ways to increase the exhaust gas temperature (EGT). Limited changes in exhaust temperature were noticed for both fuels without PI.…”

“…Multiple injection can reduce the combustion noise, smoke, and particulate matter (PM) (Fayad 2017) by controlling the injection strategies (main, pre-, and postinjection), which leads to the improvement of the characteristics of engine combustion (Nehmer, 1994, Hardy, 2006. Low-combustion temperature (LCT) is considered the main issue in most of the diesel engines (Fayad, 2018), which in turn increases the potential of PM formation and reduces the nitrogen oxides (NO X ) emissions (Bobba, 2010). It is reported that the fuel postinjection increases the exhaust gas temperature (EGT) (Desantes, 2007) because of burning some of fuel in the cylinder late in the cycle, therefore, reducing the particulate emissions formation (Fayad, 2017), increasing unburned hydrocarbons (UHC), and slightly increasing fuel consumption (Yamamoto, 2006, Mohan, 2013.…”

“…The characteristics effect of fuel postinjection (injection quantity and duration) was studied by Payri et al (Payri, 2006) in a heavy duty diesel engine. Late fuel PI leads to increases in the exhaust gas temperature and, thus, double beneficial effect in more efficient regeneration of the diesel catalyst to oxidize and trap the PM and engine gaseous emissions (Yamamoto, 2006, Fayad, 2018. Many experimental works (Chen, 2000, Yamamoto, 2006, Mohan, 2013 have been documented in the literature on how the fuel postinjection reduces particulate emissions and improves engine performance for heavy and light engines.…”

Effect of fuel injection strategy on combustion performance and NOx/smoke trade-off under a range of operating conditions for a heavy-duty DI diesel engine

“…6. This is due to the large amount of evaporated fuel that accumulates for advanced injection timing, which results in a longer ignition delay and thus a rapid burning rate [30,31]. Note that retarding the fuel injection timing leads to a slight reduction in the average in-cylinder combustion pressure.…”

Effects of Exhaust Gas Hydrogen Addition and Oxygenated Fuel Blends on the Light-Off Performance of a Three-Way Catalyst

“…Ethanol blends up to 30 vol%, performing a hot ECE cycle, showed decreasing tailpipe emission trends downstream of a TWC for CO, HC and NOx levels with increasing oxygen levels in the fuel blends, in comparison to oxygen free baseline gasoline. Butanol-diesel blends (20 vol%) significantly decreased light-off temperatures for CO and total hydrocarbon oxidation over a Pt/Pd-doped diesel oxidation catalyst (DOC) [32], [33], tentatively suggested to be due to the presence of butanol and its derivatives in the exhaust stream leading to a rise in reactivity and diffusivity resulting in earlier light-off.…”