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Top2. Bio-Diesel Vs. Straight Vegetable Oil
Biodiesel is produced from vegetable oils. The main components of vegetable oil are triglycerides. Triglycerides are esters of glycerol with long chain acids, commonly called fatty acids. Bio-diesel is defined as mono alkyl esters of long chain fatty acids derived from renewable feed stock-such as vegetable oil or animal fats, for use in compression ignition (CI) engines (Yosimoto, Onodera, & Tamaki, 2001). This name is given to the esters when they are for use as fuel.
Problems associated with using straight vegetable oil (SVO) in diesel engine, can be classified in two groups, viz, operational and durability problems. Operation problems are related to starting ability, ignition, combustion and performance. Durability problems are related to deposit formation, carbonization of injection tip, ring sticking and lubrication oil dilution. The problems associated with using straight vegetable oil (SVO) can be listed as below:
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It has been observed that SVO when used for long hours, tend to choke the fuel filter because of high viscosity and insoluble present in the SVO;
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High viscosity of SVO causes poor fuel atomization, large droplet size, and thus high spray jet penetration. The jet also tends to be a solid stream instead of a spray of small droplets. As a result, the fuel is not distributed or mixed with the air required for burning in the combustion chamber. This result in poor combustion accompanied by loss of power and economy;
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SVO has lower energy density than fossil diesel. So this leads to higher BSFC of the engine;
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To use SVO efficiently in diesel engine, modification of fuel supply system and engine redesign is required; which is much costly.