Could nanoparticles fight diesel fuel emissions?

Diesel’s low emissions record has led many people and governments to choose gasoline for personal vehicles in recent years, despite their relative inefficiency and poor 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 Diesel Engine Performance and Emissions Improvements

An example of nanoparticles tackling diesel fuel emissions was described in a recent study conducted by engineers at the Andhra Pradesh National Institute of Technology in Tadepalligudem, India. The article was published in the journal Silicon in 2021.

The researchers added silicon dioxide (SiO₂) nanoparticles to a ternary fuel, which was 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.

SiO₂ nanoparticles were mixed into the diesel-based fuel in proportions of 40 parts per million (ppm), 80 ppm and 120 ppm.

At 80 ppm, boosted diesel produces 5.4% less smoke, 6.4% less hydrocarbons and 10.2% less carbon monoxide.

Nitrous oxides (NO_X) are one of the main causes of the decline in popularity of diesel vehicles in recent years due to the growing awareness of the risks they pose to public health. The researchers noted a significant reduction in NO_X emissions.

The team also highlighted performance improvements such as improving brake thermal efficiency (BTE) by 8.8%. Combined with the biomass content of the fuel, this could also reduce the demand for diesel and, eventually, oil.

Nanoparticles are at the forefront of diesel fuel emissions research

There are many other examples of nanoparticles improving the emissions and overall performance of diesel-based fuels in the literature.

In a recent issue of Energy reportsan international team of engineers and environmental scientists has examined quite a large area of ​​the influence of nanoparticles on diesel fuel emissions.

Scientists from Mekelle University in Mekelle, Ethiopia, Norwegian University of Life Sciences in Ås, Norway, and Sultan Qaboos University in Al-khod, Oman, found that most fuel properties could be improved by adding nanoparticles.

In biofuels, nanoparticle-based additives create stable chemical reactions that can help reduce the cost of producing biofuels. They typically increase BTE in most applications, as well as reducing brake specific fuel consumption (BSFC).

Importantly, nanoparticles have been shown to consistently reduce exhaust emissions in terms of pollution from both toxic emissions and greenhouse gases.

Methods of combating diesel fuel emissions with nanoparticles

Carbon dioxide (CO₂) diesel engine emissions tend to be lower than gasoline engine emissions due to engineers’ lighter mechanical principles: using a stoichiometric mixture of air and fuel to capture more of the available energy from atoms of hydrocarbons (HC) in the fuel.

But oxygenation of the fuel source results in potentially toxic and generally harmful emissions such as HC, CO₂and no_X. Particulate matter also tends to be found in greater amounts in diesel emissions than in gasoline, leading to respiratory problems in exposed humans and other animals.

In addition to adopting the best filtration technology available, the addition of nanoparticle-based additives can alter fuel properties to reduce these harmful emissions.

Biofuels like ternary diesel and biodiesel help address some of these challenges. Particulate matter decreases in both mass and particle number in most of these alternatives, for example.

However, some challenges remain. NOPE_X emissions actually increase in untreated biodiesel due to the increased oxygen content of the fuel.

Adding carbon nanotubes (CNTs) to biodiesel reduces NO_X 9.2% emissions, 6.7% HC, CO₂ 5.9% and smoke 7.8%. These results have been observed in application in a naturally aspirated single cylinder four-stroke diesel engine operating at 1500 revolutions per minute (rpm) with varying engine loads.

Another experiment showed that adding titanium dioxide (TiO₂) Pongamia-based biodiesel fuel nanoparticles at 100 ppm led to reductions in NO_XHC, CO₂and smoke emissions of 3.8%, 2.1%, 1.9% and 2.7%, respectively.

Aluminum oxide (Al₂O₃) nanoparticles blended with B20 biodiesel resulted in reductions in all exhaust emissions, including approximately 55% less HC and 75% less CO₂. These significant results are attributable to the improvements in mass transfer and radiant heat transfer brought about by the nanoparticle processing.

Another study found that copper oxide (CuO), rhodium oxide (Rh₂O₃), carbon nanotubes, aluminum carbide (Al₄VS₃), titanium dioxide (TiO₂), graphene, and regular diesel ferrous liquids resulted in reductions in all exhaust gases.

These results are affected by several factors other than various nanoparticles, of course. Make and model of test engine, fuel type and concentrations, engine operating conditions and duty cycles, and test methods and instruments used.

Continue Reading: Can Nanoparticle Fuel Additives Give Fossil Fuel Engines Hope?

References and further reading

Bidir, MG, et al. (2021). The role of nanoparticles in the production of biofuels and as an additive in a ternary mixture diesel engine: a review. Energy reports. doi.org/10.1016/j.egyr.2021.05.084.

Ramachander, R., SK Gugulothu and GRK Sastry (2021). Performance and emission reduction characteristics of metal-based Sio₂ Nanoparticle additives mixed with ternary fuel (Diesel-MME-Pentanol) on a CRDI diesel engine. Silicon. doi.org/10.1007/s12633-021-01024-4.

Selvanayagam, BF, et al. (2022). A review of nanoparticles blended into diesel to improve combustion characteristics and reduce diesel engine emissions. Materials Today: Reviews. doi.org/10.1016/j.matpr.2022.04.828.

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