Filtration Efficiency and Regeneration Behavior in a Catalytic Diesel Particulate Filter with the Use of Diesel/Polyoxymethylene Dimethyl Ether Mixture

Polyoxymethylene dimethyl ether (PODEn) is a promising diesel additive, especially in particulate matter reduction. However, how PODEn addition affects the filtration efficiency and regeneration process of a catalytic diesel particulate filter is still unknown. Therefore, this experimental work investigated the size-dependent particulate number removal efficiency under various engine loads and exhaust gas recirculation ratios when fueling with diesel and diesel/PODEn mixture. In addition, the regeneration behavior of the cDPF was studied by determining the break-even temperatures for both tested fuels. The results showed that the cDPF had lower removal efficiencies in nucleation mode particles but higher filtration efficiencies in accumulation mode particles. In addition, the overall filtration efficiency for P10 particles was higher than that for D100 particles. Positioning the upstream cDPF, increasing the EGR ratio slightly decreased the number concentration of nucleation mode particles but greatly increased that of accumulation mode particles. However, increasing the EGR ratio decreased the removal efficiency of nanoparticles, and this effect was more apparent for the P10 case. Under the same period of soot loading, the pressure drop of P10 fuel was significantly lower than that of diesel fuel. In addition, a significantly lower BET was observed for the P10 fuel, in comparison with D100 fuel. In conclusion, adopting cDPF is beneficial for fueling with P10 in terms of the overall filtration efficiency in the particulate number and the lower input energy requirement for active regeneration. However, with the addition of EGR, the lower filtration efficiencies of nanoparticles should be concerned, especially fueling with diesel/PODEn mixture.

Investigating the impact of gasoline composition on PN in GDI engines using an improved measurement method

An experimental investigation was carried out to investigate Particulate Number (PN) emissions from a modern, small-capacity Gasoline Direct Injection (GDI) engine. The first part of the study focused on improving measurement repeatability using the Cambustion DMS-500 device. Results showed that sampling near the exhaust valve – while dampening the pressure oscillations in the sampling line – can significantly improve the repeatability. It was also found that uncontrolled phenomena such as deposition in the exhaust system from earlier engine operation can undermine the accuracy of measurements taken at tailpipe level. The second part of the work investigated PN emissions from three types of gasoline fuel, Pump-grade, Performance and Reference. Fuel chemical composition was found to have an appreciable impact on PN, but the magnitude of this effect differs in various operating points, being more pronounced at higher engine load. The Reference fuel was found to have the lowest PN emission tendency, conceivably because of its lower aromatics, olefins and heavy hydrocarbons content. A sweep of operating parameters showed that higher injection pressure reduces PN, but the extent of the reduction depends on fuel physical properties such as volatility.

Regulated, Unregulated, and Particulate Emissions from Biodiesel Blend Fueled Transportation Engine

Engine experiments were performed for measurement of regulated, unregulated, and particulate emissions using a 2.2L transportation compression ignition engine fueled with blends of diesel and biodiesels derived from Jatropha and waste cooking oils. JB20 (20% v/v Jatropha biodiesel blended with 80% v/v diesel), WCOB20 (20% v/v waste cooking oil biodiesel blended with 80% v/v diesel) and baseline mineral diesel were used as test fuels in this study. Experiments were performed at an engine speed of 2000 rpm at five engine loads (0, 25, 50, 75, and 100% rated load). Regulated emission results exhibited that JB20 and WCOB20 emitted higher HC, and CO at low engine loads compared to baseline diesel, whereas WCOB20 exhibited relatively higher NOX emissions compared to baseline diesel. Unregulated emissions were higher at low engine loads and decreased with increasing engine load. Biodiesel blends showed relatively higher methane and ethylene trace emissions compared to baseline diesel, whereas WCOB20 showed higher formaldehyde, formic acid, iso-pentane, sulfur dioxide, n-octane emissions compared to diesel at no load. Particulate number concentrations were relatively higher from biodiesel blends compared to baseline diesel in most engine operating conditions.

Experimental investigations of mineral diesel/methanol-fueled reactivity controlled compression ignition engine operated at variable engine loads and premixed ratios

Global warming and stringent emission norms have become the major concerns for the road transport sector globally, which has motivated researchers to explore advanced combustion technologies. Reactivity controlled compression ignition combustion technology has shown great potential to resolve these issues and deliver high brake thermal efficiency and emit ultra-low emissions of oxides of nitrogen and particulate simultaneously. In this experimental study, baseline compression ignition combustion mode and reactivity controlled compression ignition combustion mode experiments were performed in a single-cylinder research engine using mineral diesel as high-reactivity fuel and methanol as low-reactivity fuel. All experiments were carried out at constant engine speed at four engine loads (brake mean effective pressure: 1–4 bar). For efficient combustion and lower emissions, four premixed ratios ( rp = 0, 0.25, 0.50, and 0.75) were tested to assess optimized premixed ratio at different engine loads. In these experiments, primary and secondary fuel injection parameters were maintained identical. Combustion results showed that reactivity controlled compression ignition combustion was more stable compared to compression ignition combustion and resulted in lesser knocking. Reactivity controlled compression ignition combustion delivered higher brake thermal efficiency and lower exhaust gas temperature and oxides of nitrogen emissions, especially at maximum engine loads. Addition of methanol as secondary fuel reduced particulate emissions. Particulate analyses depicted that reactivity controlled compression ignition combustion mode emitted significantly lower accumulation mode particles; however, emission of nucleation mode particles was slightly higher. A significant reduction in particulate mass emitted from reactivity controlled compression ignition combustion was another important finding of this study. Particulate number–mass distributions showed that increasing the premixed ratio of methanol led to a dominant reduction in particulate number concentration compared to particulate mass. Analysis for critical performance and emission characteristics suggested that optimization of the premixed ratio of methanol at each engine load should be done in order to achieve the best results in reactivity controlled compression ignition combustion mode.

Mechanisms of fuel injector tip wetting and tip drying based on experimental measurements of engine-out particulate emissions from gasoline direct-injection engines

Gasoline fuel deposited on the fuel injector tip has been identified as a significant source of particulate emissions at some operating conditions of gasoline direct-injection engines. This work proposes simplified conceptual understanding for mechanisms controlling injector tip wetting and tip drying in gasoline direct-injection engines. The objective of the work was to identify which physical mechanisms of tip wetting and drying were most important for the operating conditions and hardware considered and to relate the mechanisms to measurements of particulate number emissions. Trends for each of the physical processes were evaluated as a function of engine operating conditions such as engine speed, start of injection timing, engine load, fuel rail pressure, and coolant temperature. The effects of fuel injector geometries on the tip wetting and drying mechanisms were also considered. Several mechanisms of injector tip wetting were represented with the conceptual understanding including wide plume wetting, vortex droplet wetting, fuel dribble wetting, and fuel condensation wetting. The main tip drying mechanism considered was single-phase evaporation. Using the conceptual understanding for tip wetting and drying mechanisms that were created in this work, the effects of engine operating conditions and fuel injector geometries on the mechanisms were compared with experimental results for particulate number. The results indicate that measured particulate number was increased by increasing injected fuel mass. Increasing injected fuel mass was suspected to increase tip wetting via wide plume wetting and vortex droplet wetting mechanisms. Particulate number was also observed to increase with hole length. Longer hole length was suspected to result in higher tip wetting via vortex droplet and fuel dribble wetting mechanisms. Longer timescale was found to decrease particulate number emissions. Lower speeds and early injection timings increased the timescale. Similarly, higher coolant temperature decreased particulate number. The coolant temperature influenced tip temperature resulting in higher tip drying.