Strategies for active diesel particulate filter regeneration based on late injection and exhaust recirculation with different fuels

Abstract

Wall flow–type particulate filters are used in diesel vehicle engines to reduce particulate emissions below the limits established in regulations Euro 5 and Euro 6. The soot accumulated in the trap is eliminated during regeneration processes, often combining passive strategies with active ones. Active regeneration is conducted by modifications of the engine control parameters with respect to those set for normal vehicle operation. In this work, three of these parameters were modified to look for an optimized regeneration strategy, considering fuel consumption, gaseous emissions and rate of regeneration. The selected parameters were injection timing (affecting all injection events), exhaust gas recirculation and amount of postinjected fuel. The fuel tested was considered as an additional variable, and therefore, tests were performed with three different fuels: an ultra-low sulfur diesel fuel, a biodiesel fuel produced from animal fat and a gas-to-liquid fuel from low-temperature Fischer–Tropsch process. It was proved that eliminating the gas recirculation is the optimal option for a fast regeneration and reduced fuel consumption and that the late postinjection is essential to keep the temperature conditions needed for an efficient regeneration. Some limits were also proposed for these parameters to prevent from excessively fast or uncontrolled regeneration, to avoid excessive increase in fuel consumption and to reduce the probability of fuel dilution. Finally, the fuel properties were proved to be very relevant to the regeneration process, and therefore, both biodiesel and gas-to-liquid fuels (especially the former) showed un-optimized regeneration processes under the conditions set for regeneration process optimized with diesel fuel.

Late post-injection of biofuel blends in an optical diesel engine: Experimental and theoretical discussion on the inevitable wall-wetting effects on oil dilution

“…Also use of biodiesel may increase oil dilution. Lapuerta et al 8 studied the optimization of DPF regeneration strategies with different types of fuels. They concluded that the fuel properties are an important input, due to effects of the fuel on the combustion, on the thermal conditions and on the soot oxidation kinetics.…”

Late Fuel Post-Injection Influence on the Dynamics and Efficiency of Wall-Flow Particulate Filters Regeneration

“…The reason behind this limitation for post-injected fuel mass rate is the reduction in O 2 concentration at the DPF inlet as the fuel mass increases, as observed in Figure 9. Very low O 2 concentration causes limitations to the chemical kinetics of the soot oxidation process [22]. These effects are more critical once the highest reactivity stage has finished, as observed in Figure 12.…”

“…Both parameters play a significant role in the properties of the exhaust gas arriving to the catalyst, mainly in terms of its temperature and the HC concentration [21]. In order to maximise the regeneration efficiency it is typical to combine the post-injection strategies with other engine control actuations, such as to act on the exhaust gas recirculation (EGR) valve, aimed at increasing the exhaust temperature [22] or the closure of the intake throttle valve, limiting the air flow coming into the cylinders in order to achieve richer equivalence ratio mixtures and higher HC concentration during the main combustion event [23]. Parks et al [24] studied the relationship between the exhaust gas temperature and the optimal post-injection timing for the regeneration.…”

Comparison of in-plane and out-of-plane piezoelectric microresonators for real-time monitoring of engine oil contamination with diesel

“…Contamination by diesel soot has a significant impact on engine wear, with most engine manufacturers opting for Exhaust Gas Recirculation (EGR) technology to decrease NOx emissions. Returning exhaust product to the diesel engine combustion chamber may accelerate the degradation of the lubricant oil, affecting its rheological properties (George et al 2007;Aldajah et al 2007;Lapuerta et al 2014).…”