Diesel’s poor emissions have led many people and governments to opt for petrol-powered personal vehicles in recent years, despite their relative inefficiency and reduced range. Modern diesel cars emit far less toxic pollution thanks to improved filtration methods, but nanoparticle-based additives could be the technology that keeps diesel on the road.
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Silicon Dioxide Nanoparticle Additives for Performance and Emissions Improvement in Diesel Engines
An example of nanoparticles tackling diesel fuel emissions was described in a recent study by engineers at the National Institute of Technology Andhra Pradesh in Tadepalligudem, India. The article was published in the magazine Silicon for 2021.
The researchers added silicon dioxide (SiO2) nanoparticles into a ternary fuel, a biofuel combination of 70% diesel, 20% mahua methyl ester and 10% pentanol. They measured the emission, combustion and performance characteristics of the fuel when used in a common rail direct injection diesel engine.
the SiO2 nanoparticles were mixed with the diesel-based fuel in ratios of 40 parts per million (ppm), 80 ppm and 120 ppm.
At 80 ppm, the doped diesel was found to produce 5.4% less smoke, 6.4% less hydrocarbon and 10.2% less carbon monoxide.
Nitrogen oxides (NOX) are a major driver of the declining popularity of diesel vehicles in recent years due to a growing awareness of the public health risks they pose. Researchers noticed a significant reduction in NO. onX emissions.
The team also highlighted performance improvements such as 8.8% improved thermal efficiency of the brakes (BTE). In combination with the biomass content in the fuel, this can also reduce the demand for diesel and ultimately oil.
Nanoparticles are at the forefront of research into diesel fuel emissions
There are many more examples in the literature of nanoparticles improving the emissions and overall performance of diesel-based fuels.
In a recent issue of Energy Reportsan international team of engineers and environmental scientists reviewed what is a fairly extensive field on the influence of nanoparticles on diesel fuel emissions.
The scientists from Mekelle University in Mekelle, Ethiopia, the Norwegian University of Life Sciences in Ås, Norway, and Sultan Qaboos University in Al-khod, Oman, found that most fuel properties can be improved by the addition of nanoparticles.
In biofuels, nanoparticle additives create steady chemical reactions that can help reduce the cost of biofuel production. They generally increase BTE in most applications, and also decrease Brake Specific Fuel Economy (BSFC).
Importantly, nanoparticles consistently reduce tailpipe emissions in terms of pollution from both toxic emissions and greenhouse gases.
Methods to tackle the emission of diesel fuel with nanoparticles
Carbon dioxide (CO2) emissions from diesel engines are typically lower than gasoline engines due to the engineers’ leaner mechanical principles: using a stoichiometric mixture of air and fuel to capture more of the available energy from hydrocarbon atoms (HC) in the fuel.
But making the fuel source oxygen rich leads to potentially toxic and generally harmful emissions such as HC, CO2and noX† Particulate matter is also often found in greater amounts in diesel emissions than in gasoline, leading to respiratory problems in humans and other exposed animals.
In addition to applying the best available filtration technology, adding nanoparticle additives can change fuel properties, reducing these harmful emissions.
Biofuels such as ternary diesel and biodiesel help with some of these challenges. For example, in most of these alternatives, particulate matter decreases both in mass and in number of particles.
However, some challenges remain. NOX the emissions from untreated biodiesel increase precisely because of the increased oxygen content in the fuel.
Adding carbon nanotubes (CNTs) to biodiesel reduces NOX emissions by 9.2%, HC by 6.7%, CO2 by 5.9% and smoke by 7.8%. These findings were observed when used in a four-stroke, single-cylinder, naturally aspirated diesel engine operating at 1500 revolutions per minute (rpm) with varying engine loads.
Another experiment showed that adding titanium dioxide (TiO2) nanoparticles to Pongamia-based biodiesel fuel at 100 ppm led to reductions in NOXHC, CO2and smoke emissions at 3.8%, 2.1%, 1.9% and 2.7%, respectively.
Aluminum Oxide (Al2O3) nanoparticles mixed with B20 biodiesel led to a reduction in all tailpipe emissions, including approximately 55% less HC and 75% less CO2† These significant results are due to improvements in mass transfer and radiant heat transfer caused by nanoparticle treatment.
Another study found that copper oxide (CuO), rhodium oxide (Rh2O3), carbon nanotubes, aluminum carbide (Al4C3), titanium dioxide (TiO2), graphene and ferrous fluids to regular diesel led to reduction of all exhaust gases.
These results are, of course, influenced by several factors other than different nanoparticles. The make and model of the test engine, the fuel type and concentration ratios, the engine operating conditions and duty cycles, and the methods and instruments used for testing.
References and further reading
Bidir, MG, et al. (2021). The role of nanoparticles in biofuel production and as an additive in ternary-mix diesel engines: an overview. Energy Reports† doi.org/10.1016/j.egyr.2021.05.084†
Ramachander, R., S.K. Gugulothu and G.R.K. Sastry (2021). Performance and Emission Reduction Characteristics of Metal-Based Sio2 Nanoparticle additives mixed with ternary fuel (diesel-MME-pentanol) on CRDI diesel engine. Silicon† doi.org/10.1007/s12633-021-01024-4†
Selvanayagam, BF, et al† (2022). An overview of nanoparticles mixed with diesel to improve combustion properties and reduce emissions from diesel engines. Materials today: procedures† doi.org/10.1016/j.matpr.2022.04.828†
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