Hi,
I am currently tasked with comparing different alternative fuels with gasoline and diesel, for their performance to reduce CO2 emissions.
Alternative fuels i am considering for this comparison are -
Methanol, Ethanol, LPG, CNG, and Bio-diesel.
The parameters I considered are Self-ignition temperature, Octane Rating, Stoichiometric Air-fuel ratio, and Calorific Value.
Are these parameters correct and can lead to some conclusion in terms of CO2 reduction?
What are other parameters I can consider in order to get an analysis towards CO2 emissions?
If you can provide some citations/references, in this aspect it will be of great help.
combustion efficiency and in-cylinder temperature (peak temp and pressure, temperature during and after combustion ) also plays imp role in CO2 emission.
U can refer these papers.
1) M.Al-Hasan. Effect of ethanol–unleaded gasoline blends on engine performance and exhaust emission. Energy Conversion and Management 2003; 44: 1547–1561
2) Mustafa Kemal Balki, Cenk Sayin, Mustafa Canakci. The effect of different alcohol fuels on the performance, emission and combustion characteristics of a gasoline engine. Fuel 2014; 115: 901–906.
3) Pourkhesalian AM, Shamekhi AH, Salimi F. Alternative fuel and gasoline in a Spark ignition engine: a comparative study of performance and emissions characteristics. Fuel 2010; 89:1056-1063.
4) H.S. Farkade, A.P. Pathre. Experimental investigation of methanol, ethanol and butanol blends with gasoline on SI engine. International Journal of Emerging Technology and Advanced Engineering 2012; 2: 205–215.
Thanks a lot Daizy for the help. That was very quick :)
Could you please help me understand Combustion Efficiency? How is it defined and expressed?
Also, as i understand, the peak cylinder temeperature and pressure are functions of injection/ignition timing. Should i consider this as well? I mean, if i need to use methanol or ethanol, what should i be doing on injection/ignition timing? Advance it or retard?
Yes, Start of injection and ignition both are really very important for CO2 emission study.
Kindly do take it in to account. As per my experience of Ethanol and Butanol, on which I have worked, for both I have retarded the ignition timing, but then again advance/retard depends on your engine, spark plug and fuel injector configurations.
Combustion efficiency, easily u can calculate. U know the energy (MJ/Kg) Calorific value of fuel as input, and u know the power produced as output, with the help of these u can calculate combustion efficiency. Kindly refer the papers, these will help u much.
Thanks,
Daizy Rajput
NML
To compare fuels toward CO2 emissions you only need the C contend of the fuel, the lower heating value (LHV) and the efficiency reported to LHV, especially the variation of efficiency when changing of fuel and/or engine.
The comparison is done to the same energy delivered.
When you replace diesel fuel by biodiesel you can consider the efficiency is the same. The origin of carbon is different, a part of nature for biodiesel, fossil carbon for diesel fuel.
When you compare gasoline, LPG, and CNG you can consider the efficiency is the same (with a good approx) for the same engine and the same power.
For methanol and ethanol it is different due to their latent heat of evaporation especially for pure methanol.
But with CNG, methanol and ethanol you can use more adaptated engine to these fuels. So efficency may be better.
Octane number or cetane number are only interesting to know if you have to change of engine.
For example, CNG has a higher octane number than gasoline so you can use an engine with a higher compression ratio.
The effect of combustion velocity is small because major part of combustion is at constant volume : small displacement of the piston near top dead center when the fuel is burning.
In order to fairly compare the environmental impact of various fuels you really need t do a cradle to grave analysis. Ethanol made from sugar cane will be significantly better than ethanol made form corn if you do that analysis. Methanol is produced by reforming natural gas to produce syngas (H2 + CO) that is converted to methanol at about 75% efficiency (for a well designed plant).Bio-diesel is made by esterification of vegetable oils with methanol forming glycerine as a byproduct. The baseline to compare against should be conventional gasoline and diesel refined from petroleum including energy used for refining (about 6%). It is a pretty complex problem.
Where the fuel came from (carbon embedded in the production of the fuel, well-to-tank analysis) and how efficiently it is used (fuel consumed to achieve the desired output)
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