Ethanol-Gas Blend Impact on Emissions & Efficiency

Background research

Ethanol

Ethanol is a chemical compound and a simple alcohol with a chemical formula . It is volatile, flammable, colorless and transparent liquid. It is main type of alcohol in alcoholic drinks. It is produced by the fermentation of sugars by yeasts or petrochemical processes. Ethanol is also used a clean burning fuel (Wikipedia, 2019). It can be burned together with oxygen and results in a complete combustion, which can be seen in the following equation:

Gasoline

Gasoline derived from crude oil/petroleum. It is fractionally distilled to a clear liquid form. Different additives are used to make fuel for motor vehicles. The terminology ‘gasoline’ is used mainly in the USA but in Europe and Asian countries it is called petrol. (The Economic Times, 2019)

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Octane rating

Octane rating is a measure of a fuel's ability to resist 'knock’. The octane rating indicates the degree of the air-fuel mixture that can be compressed before it will spontaneously ignite. Engines are different in their compression ratio, their mechanical design and environmental conditions in which they operate. The higher the octane rating, the more the fuel will prevent knocking or pinging during combustion. (Exxon, 2019) In Australia, the following are the gasoline octane ratings: unleaded - 91, unleaded – 95 and premium – 98. (Allianz, 2019) Pure ethanol has a higher octane rating than gasoline and can be added to gasoline to improve knock and ping resistance as well as improving engine performance (De Simio, Gambino & Iannaccone, 2012)

Volatile Organic Compounds (VOC)

Volatile organic compounds (VOCs) are organic chemicals with a high vapor pressure at ambient room temperature. VOCs have been known to be dangerous to human health or the environment. (Wikipedia, 2019)

Greenhouse gases

Greenhouse gases are gaseous compounds that make up the Earth’s atmosphere. They prevent Earth’s thermal radiation from escaping the atmosphere. The greenhouse gases form a layer which is strongly affects the climate on Earth which results in a rise of temperature. (Anastasia Anushevskaya, 2019) The main greenhouse gases which naturally occurring and from human activities are water vapor, carbon dioxide , methane , ozone and nitrous oxide . (ACS, 2019)

• Carbon Dioxide – 76%: The main source of comes from burning fossil fuels and industrial processes. (EPA, 2019)
• Methane – 16%: the main source of comes form agricultural processes, waste and burning of biomass. (EPA, 2019)
• Nitrous oxide – 6%: the main source of comes from fertilizers which are used in agriculture. The burning fossil fuels also contribute to release . (EPA, 2019)

Methodology

The 1.6 litre spark ignition engine equipped with three way catalyst (TWC) at the exhaust and is mounted on a test bed. A pressure transducer is installed in the combustion chamber of cylinder 3 and thermocouples are used to monitor the head temperature. Gaseous emissions are measured with a hot Beckman 404 flame ionization detector (FID) for THC, a hot ABB UV Limas 11 for nitrogen oxides and a cold ABB URAS 14 for , and oxygen. A Coriolis mass flow meter was used to measure the fuel consumption. The tests were performed with pure gasoline and blended with ethanol added in volumes of 10%, 20%, 30% and 85%. (De Simio, Gambino & Iannaccone, 2012)

Carbon dioxide

At High and low temperatures, the formation of carbon dioxide when carbon monoxide reacts with radicals hydroxyl and hydroperoxyl: (Antonio Carlos Santos, 2012)

However, CO2 emission is increase, but this is better option in terms of environmental concerns because is more reactive and can be removed from the atmosphere, which is shown in previous equations. This option reduces the amount of OH, which is used to remove methane. The effect of this is the rise of carbon dioxide in the atmosphere. The decomposition of carbonyl radicals to form cetyl radicals, after the formation of intermediate compounds at temperatures around 600 k and 700 k. The carbon dioxide also be formed from reaction between radicals and ketones: (Antonio Carlos Santos, 2012)

Methane

Methane is being formed mainly by decomposition of cetyl radicals, with the addition of the oxygen atom to ethylene and decomposition of n-propyl radical which would form an intermediate, the methyl radical. The following reactions shows the formation of methane using formaldehyde, ethylene and hydrogen atoms: (Antonio Carlos Santos, 2012)

NItrogen compounds

The formation of nitric oxide occurs from nitrogen in combustion. The main sources of nitrogen to form nitrous oxides comes from atmospheric nitrogen and from the fuel.

The increase in temperature from combustion results in the formation of which is an and precursor. (Antonio Carlos Santos, 2012) The formation of can be by four possible mechanisms:

• a) Zeldovich or thermal
• b) Fenimore or “prompt”
• c) From the formation of
• d) The decomposition of organic compounds of nitrogen

Internal combustion engines which use gasoline create temperatures around 2000 k, creating approximately 95% . (Antonio Carlos Santos, 2012)

Nitrogen’s bond with air needs a high level of activation energy to break the triple bond, abound 220 Kcal/mol. Zeldovich suggested the following mechanism: (Antonio Carlos Santos, 2012)

Analysis of results

No difference was found among all the tested blends at each speed and load condition. No difference was found on the manifold absolute pressure (MAP) because the heat content of the stoichiometric air/fuel mixture was not influenced by the content of ethanol in each blend. Therefore, the engine must take in the same total mass (air +fuel). The increase of the ethanal content leads to longer injection times to maintain the stoichiometric mixture at a given load. The optimal spark advance with each blend resulted to be more or less the same as the pure gasoline (see table 4). Injection time, fuel mass and volume flow rate increase with the ethanol content in the blends. The fuel mass increased with the ethanol content but is considerably lower than that predicted on the basis of tested fuel characteristics. The theoretical data is to be higher than experimental data. The reliability of the data was test by repeating the experiment and allowing for a longer period of time and the results remained the same. We can see the decrease in CO2 emission as ethanol content in gasoline increases. The increase in efficiency with greater than 3% with increase of ethanol content. The higher oxygen content results in a better combustion of fuels, which increases the efficiency. The rate of combustion reaction was slightly improved when ethanol was added. (De Simio, Gambino & Iannaccone, 2012) Another advantage of ethanol is that it has a higher octane number which provides an opportunity to design more powerful engines. The existence of and radicals in blend of gasoline and ethanol affects the emission of , and hydrocarbons. Blend of ethanol and gasoline can reduce the emission by 22% on average compared to pure gasoline. (Antonio Carlos Santos, 2012)

Conclusion

Increasingly, attention is being given to the use of biomass to produce fuels for transport as an alternative to petrol. The use of bio-ethanol can help considerably to reduce greenhouse gas emissions in vehicles. Ethanol has a higher octane number than gasoline and excellent in improving performance in engines to reduce the risk of engine knock. Ethanol can be used pure or mixed with gasoline. Pure ethanol is problematic in a cold environment because its vaporization is lower than gasoline, resulting in the need for preheating of the engine block. Vehicles must have anti-corrosive parts in the engine to prevent rusting due to the ethanol fuel. Blending ethanol with gasoline creates a higher compression ratio in the engine without engine knock. Gasoline with E10, E20, E30, E85 were tested on a commercial light duty engine to evaluate the effect of ethanol content on thermal efficiency compared to a gasoline engine. This investigation shown that ethanol as addictive in gasoline can reduce the emission by 22% on average and increase thermal efficiency by 3%.

The results support my hypothesis, “Blend of gasoline and ethanol would reduce the greenhouse gas emissions”. The future research has to conducted at different conditions (eg. temperature, humidity) and using different engine.

Bibliography

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