A review published in the journal Energy & Fuels examines factors of alcohols and their impact on the properties of compression ignition (CI) engines, as well as how nanoadditives affect diesel engine behavior.
Study: Critical Review on Effects of Alcohols and Nanoadditives on Performance and Emission in Low-Temperature Combustion Engines: Advances and Perspectives. Image Credit: Standret/Shutterstock.com
Alcohols and Ethers – Alternatives to Fossil Fuels
Ethers and alcohols are oxygenized fuels or combustion engine additives that present an alternative option to conventional fossil fuels. Ethanol, methanol, butanol, propanol, and pentanol, all derived from fossil fuels or sustainable resources, are routinely blended with diesel fuel, keeping the peak alcohol content at 20%.
The Pressing Needs of the Automotive Industry
The automotive industry is facing considerable challenges, such as the requirement for more robust combustion engines, electric powertrains, and replacing traditional fuels with substitutes to minimize the release of greenhouse gases.
The challenge faced by combustion engines and fuel systems is therefore twofold: reducing fuel usage and minimizing the discharge of greenhouse gases. In this context, innovative ideas and optimal combustion methods, like increased spray atomization, higher burning rates, smaller local equivalence ratios, better air/fuel mixing, and lower peak temperatures within the combustion chamber are becoming more pertinent.
When advanced combustion methods are used, alcohol-based fuels have been shown to offer a potential substitute for traditional fossil fuels, with the promise of lower emissions. Owing to their straightforward manufacturing and significant storage capacity, alcohols have shown their potential to boost combustion engine performance and minimize exhaust discharge.
The Effects of Alcohol Additives
The impacts of oxygenized compounds on combustion engine performance were investigated in this review.
It was found that ethanol's cold startup capabilities and lower inflammability considerably influence its utilization with diesel. The considerable cooling impact of ethanol in the mixtures raises hydrocarbon emissions.
Aldehyde generation has been decreased in diesel mixes containing pentanol. Moreover, the thermodynamic process of pentanol addition is similar to the constant volume cycle, resulting in quicker combustion, enhanced thermal performance, and better hydrogen reduction reactions.
Butanol, on the other hand, has better miscibility as compared to other alcohols and has a larger cetane number, making it the favored additive for diesel production. Because of butanol's increased hydrophobic nature, transportation and distribution seem fairly simple in the present infrastructure.
The Effects of Nano-additives
This review provides a full summary of the major scientific efforts and recent breakthroughs in nanofluid fuels.
Numerous studies revealed that microscale or nanoscale metallic particles continue to enhance ignition and burning performance when coupled with diesel/biodiesel fuels. Large surface area to volume ratios, as well as more reactive areas of nanofluid fuels, allow for faster oxidation of fuel, leading to higher burning enthalpy and energy density.
Nanoparticles showed improved combustion when combined with diesel/biodiesel fuels because of the outstanding thermophysical features of nanofluid fuels.
Rapid vaporization, better atomization, appropriate air-fuel mixtures, and more sustainable flames shorten the pre-mixing and diffusion phases, reducing delays in nanofluid fuel ignition.
Ignition, burning, and oxidizing behavior of nanofluid fuels is strongly related to nanoadditive dimensions, morphological aspects, the thickness of the oxide layer, and ambient temperature and pressure.
Since the cumulative action of diesel/biodiesel fuels on nanoadditives might cause anomalous combustion, choosing the right variables is crucial for regulated combustion.
Nanoadditives in biodiesel fuel mixes were reported to increase diesel engine characteristics up to a specified nanoadditive dosage, with improved brake thermal efficiency, slightly higher boiling points, and reduced brake-specific fuel consumption.
Most of the outcomes were achieved by incorporating nanoadditives into diesel/biodiesel blends, which may boost combustion engine performance while cutting down emissions. The major difference was due to the various biodiesel, nanoadditives, volume fractions, and sizes.
The nanoadditive particle size has the biggest impact on combustion properties, while the total energy in the fuel mix has the greatest effect on fuel efficiency. More work is required to establish the numerous inconsistencies induced by variances in the sizes of nanoparticles and nanoadditive dosage.
Munuswamy, D. B., Devarajan, Y., Ramalingam, S., Subramani, S., & Munuswamy, N. B. (2022). Critical Review on Effects of Alcohols and Nanoadditives on Performance and Emission in Low-Temperature Combustion Engines: Advances and Perspectives. Energy & Fuels. Available at: https://doi.org/10.1021/acs.energyfuels.2c00930