The alkyl monoesters of fatty acids derived from vegetable oils or animal fats, known as biodiesel, is attracting considerable interest as an alternative fuel for diesel engines. Biodiesel-fueled engines produce less carbon monoxide, unburned hydrocarbons, and particulate emissions than diesel-fueled engines. However, biodiesel has different chemical and physical properties than diesel fuel, including a larger bulk modulus and a higher cetane number. Some of these properties can be affected by oxidation of the fuel during storage. These changes can affect the timing of the combustion process and potentially cause increase in emissions of oxides of nitrogen. The objective of the study is to evaluate the effect of injection and combustion time on biodiesel combustion and exhaust emissions. Experimental investigations have been carried out using biodiesel as an alternative fuel in single cylinder, compression-ignition engine under various operating conditions and injection timings with respect to TDC. Various parameters such as brake power, peak pressure rise, and emissions during combustion process under various operating conditions with diesel, biodiesel and biodiesel blends were measured and the results analyzed. In conclusion, the conditions under which improvement in emissions can be achieved have been reported.
Biodiesel
is a domestically produced renewable fuel that can be manufactured
from vegetable oils or recycled oils. It is safe, biodegradable
and reduces serious air pollution by reducing particulate,
carbon monoxide (CO), hydrocarbons (HC), and air toxicity.
Experimental investigations have shown that the blends of
20% biodiesel with 80% petroleum diesel (B20) can be used
in unmodified diesel engines, or biodiesel can be used in
pure form (B100), but may require certain engine modifications
to avoid maintenance and performance problems. Conversion
of rice bran oil into methyl ester for use as a biodiesel
fuel involves transestirification of the oil triglycerides.
To accomplish this conversion, raw rice bran oil is treated
at room temperature with absolute methyl alcohol in the presence
of potassium hydroxide as a catalyst. During the process,
the glycerol which is produced is insoluble in the ester,
and being heavier, settles down carrying most of the dissolved
potassium hydroxide catalyst with it. After initial setting,
some of the undesirable, emulsion forming byproducts may remain
in the ester layer, causing problems in the washing stage.
Re-stirring the glycerol into the ester separates it. Water
may be added and the mixture allowed to settle down again. |
