• Energy Research

Abstract The present study focuses on the synthesis of novel catalytic nanoparticles and their effect on combustion, performance, and emission characteristics of a diesel engine. For this purpose, Mg cations were doped into a Fe3O4 lattice to form MgxFe(3-x)O4 (x = 0.25, 0.5, 0.75, and 1) using a solution combustion method. Comprehensive characterization studies were carried out to assess the oxygen storage capacity (OSC) and the properties of final powders. These synthesized samples were dispersed in a diesel-biodiesel blend fuel with a concentration of 90 ppm. Assessment of the structure of the samples proved the formation of MgFe2O4 structures, suggesting that Mg cations were embedded into the Fe3O4 and formed appropriate structures. The OSC was reduced from 8661 μmol/g (Mg0·25Fe2·75O4) to 7069 μmol/g (MgFe2O4) by introducing additional Mg cations. When run on a six-cylinder diesel engine, the fuel mixed from the synthesized samples did not significantly influence the indicated power (IP), brake specific fuel consumption (BSFC) or the brake thermal efficiency (BTE). In addition to the obtained result for the OSC of the sample, which declined by increasing the Mg concentration in the Fe3O4 lattice, using the sample with the highest concentration of Mg cations, a considerable reduction was detected in the major exhaust emissions such as HC (56.5%), PM1 (35%), and PN (37%) and a slight decrease occurred in CO (7%) compared to the engine fueled by pure fuel. Based on the experimental engine results, the MgFe2O4 sample can be considered as a useful nanocatalyst for mixing in the fuels for emissions reduction.

Abstract The present study focuses on the synthesis of novel catalytic nanoparticles and their effect on combustion, performance, and emission characteristics of a diesel engine. For this purpose, Mg cations were doped into a Fe3O4 lattice to form MgxFe(3-x)O4 (x = 0.25, 0.5, 0.75, and 1) using a solution combustion method. Comprehensive characterization studies were carried out to assess the oxygen storage capacity (OSC) and the properties of final powders. These synthesized samples were dispersed in a diesel-biodiesel blend fuel with a concentration of 90 ppm. Assessment of the structure of the samples proved the formation of MgFe2O4 structures, suggesting that Mg cations were embedded into the Fe3O4 and formed appropriate structures. The OSC was reduced from 8661 μmol/g (Mg0·25Fe2·75O4) to 7069 μmol/g (MgFe2O4) by introducing additional Mg cations. When run on a six-cylinder diesel engine, the fuel mixed from the synthesized samples did not significantly influence the indicated power (IP), brake specific fuel consumption (BSFC) or the brake thermal efficiency (BTE). In addition to the obtained result for the OSC of the sample, which declined by increasing the Mg concentration in the Fe3O4 lattice, using the sample with the highest concentration of Mg cations, a considerable reduction was detected in the major exhaust emissions such as HC (56.5%), PM1 (35%), and PN (37%) and a slight decrease occurred in CO (7%) compared to the engine fueled by pure fuel. Based on the experimental engine results, the MgFe2O4 sample can be considered as a useful nanocatalyst for mixing in the fuels for emissions reduction.

Biodiesels produced from different feedstocks usually have wide variations in their fatty acid methyl ester (FAME) so that their physical properties and chemical composition are also different. The aim of this study is to investigate the effect of the physical properties and chemical composition of biodiesels on engine exhaust particle emissions. Alongside with neat diesel, four biodiesels with variations in carbon chain length and degree of unsaturation have been used at three blending ratios (B100, B50, B20) in a common rail engine. It is found that particle emission increased with the increase of carbon chain length. However, for similar carbon chain length, particle emissions from biodiesel having relatively high average unsaturation are found to be slightly less than that of low average unsaturation. Particle size is also found to be dependent on fuel type. The fuel or fuel mix responsible for higher particle mass (PM) and particle number (PN) emissions is also found responsible for larger particle median size. Particle emissions reduced consistently with fuel oxygen content regardless of the proportion of biodiesel in the blends, whereas it increased with fuel viscosity and surface tension only for higher diesel–biodiesel blend percentages (B100, B50). However, since fuel oxygen content increases with the decreasing carbon chain length, it is not clear which of these factors drives the lower particle emission. Overall, it is evident from the results presented here that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions.

Biodiesels produced from different feedstocks usually have wide variations in their fatty acid methyl ester (FAME) so that their physical properties and chemical composition are also different. The aim of this study is to investigate the effect of the physical properties and chemical composition of biodiesels on engine exhaust particle emissions. Alongside with neat diesel, four biodiesels with variations in carbon chain length and degree of unsaturation have been used at three blending ratios (B100, B50, B20) in a common rail engine. It is found that particle emission increased with the increase of carbon chain length. However, for similar carbon chain length, particle emissions from biodiesel having relatively high average unsaturation are found to be slightly less than that of low average unsaturation. Particle size is also found to be dependent on fuel type. The fuel or fuel mix responsible for higher particle mass (PM) and particle number (PN) emissions is also found responsible for larger particle median size. Particle emissions reduced consistently with fuel oxygen content regardless of the proportion of biodiesel in the blends, whereas it increased with fuel viscosity and surface tension only for higher diesel–biodiesel blend percentages (B100, B50). However, since fuel oxygen content increases with the decreasing carbon chain length, it is not clear which of these factors drives the lower particle emission. Overall, it is evident from the results presented here that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions.

Improving oxygen storage capacity (OSC) of metal oxides by doping with metal cations can produce a catalyst with superior properties to improve engine performance and reduce emissions. In this study, Mg cations were incorporated into a ferric oxide lattice to form Mg0.25Fe2.75O4 via the solution combustion method. The structure, texture, morphology, and oxygen storage capacity of the samples were deeply investigated. The catalytic activity of Mg0.25Fe2.75O4 was finally compared with Fe3O4 as a reference nanocatalyst in terms of its combustion emissions using a six-cylinder Cummins diesel engine. It was found that the doped catalyst presented high crystallinity containing a mixture of the spinel-type crystal lattice and α-Fe2O3 structure, which confirms the ability of the solution combustion method for the fabrication of well-crystalline catalysts. The crystalline structure, surface area, and porosities and vacancy of spinel structure of Mg doped catalyst compared to the inverse spinel structure of Fe3O4 affect OSC of the samples, such that a significant increase in OSC of Fe3O4 (7941 µmol/g) occurred by loading of Mg cations (8661 µmol/g). Based on the engine emissions results, synthesized nanocatalysts are beneficial for decreasing the hydrocarbon (HC), carbon monoxide (CO), and particle mass (PM1.0) emissions. More specifically, the effect of nanocatalysts OSC would be dominated by the impact of increased soot oxidation, leading to PM1.0 reduction.

Improving oxygen storage capacity (OSC) of metal oxides by doping with metal cations can produce a catalyst with superior properties to improve engine performance and reduce emissions. In this study, Mg cations were incorporated into a ferric oxide lattice to form Mg0.25Fe2.75O4 via the solution combustion method. The structure, texture, morphology, and oxygen storage capacity of the samples were deeply investigated. The catalytic activity of Mg0.25Fe2.75O4 was finally compared with Fe3O4 as a reference nanocatalyst in terms of its combustion emissions using a six-cylinder Cummins diesel engine. It was found that the doped catalyst presented high crystallinity containing a mixture of the spinel-type crystal lattice and α-Fe2O3 structure, which confirms the ability of the solution combustion method for the fabrication of well-crystalline catalysts. The crystalline structure, surface area, and porosities and vacancy of spinel structure of Mg doped catalyst compared to the inverse spinel structure of Fe3O4 affect OSC of the samples, such that a significant increase in OSC of Fe3O4 (7941 µmol/g) occurred by loading of Mg cations (8661 µmol/g). Based on the engine emissions results, synthesized nanocatalysts are beneficial for decreasing the hydrocarbon (HC), carbon monoxide (CO), and particle mass (PM1.0) emissions. More specifically, the effect of nanocatalysts OSC would be dominated by the impact of increased soot oxidation, leading to PM1.0 reduction.

The increasing share of using biofuels in vehicles (mandated by current regulations) leads to a reduction in particle size, resulting in increased particle toxicity. However, existing regulations disregarded small particles (sub-23 nm) that are more toxic. This impact is more significant during vehicle cold-start operation, which is an inevitable frequent daily driving norm where after-treatment systems prove ineffective. This study investigates the impact of biofuel and lubricating oil (as a source of nanoparticles) on the concentration, size distribution, median diameter of PN and PM, and their proportion at size ranges within accumulation and nucleation modes during four phases of cold-start and warm-up engine operation (diesel-trucks/busses application). The fuels used were 10% and 15% biofuel and with the addition of 5% lubricating oil to the fuel. Results show that as the engine warms up, PN for all the fuels increases and the size of particles decreases. PN concentration with a fully warmed-up engine was up to 132% higher than the cold-start. Sub-23 nm particles accounted for a significant proportion of PN (9%) but a smaller proportion of PM (0.1%). The fuel blend with 5% lubricating oil showed a significant increase in PN concentration and a decrease in particle size during cold-start.

The increasing share of using biofuels in vehicles (mandated by current regulations) leads to a reduction in particle size, resulting in increased particle toxicity. However, existing regulations disregarded small particles (sub-23 nm) that are more toxic. This impact is more significant during vehicle cold-start operation, which is an inevitable frequent daily driving norm where after-treatment systems prove ineffective. This study investigates the impact of biofuel and lubricating oil (as a source of nanoparticles) on the concentration, size distribution, median diameter of PN and PM, and their proportion at size ranges within accumulation and nucleation modes during four phases of cold-start and warm-up engine operation (diesel-trucks/busses application). The fuels used were 10% and 15% biofuel and with the addition of 5% lubricating oil to the fuel. Results show that as the engine warms up, PN for all the fuels increases and the size of particles decreases. PN concentration with a fully warmed-up engine was up to 132% higher than the cold-start. Sub-23 nm particles accounted for a significant proportion of PN (9%) but a smaller proportion of PM (0.1%). The fuel blend with 5% lubricating oil showed a significant increase in PN concentration and a decrease in particle size during cold-start.