An innovative method to reduce nox emissions from a biodiesel blend operated compression ignition engine without affecting engine thermal performance.

摘要

"This invention relates to a method of reducing the NOx emissions of the biodiesel operated compression ignition engine by using the base vegetable oil from which the biodiesel is made as an additive. Optimal percentage of this straight vegetable oil has been identified which would reduce the NOx emissions without affecting the engine thermal performance". It is wonderful invention which has far reaching consequences as far as industrial and regular day today usage of biodiesel in the Compression ignition engine, literature in the form of published work all around the world show that the wide spread usage of biodiesels is still limited by many factors including their availability, cost and more importantly NOx emissions. The high level of NOx emissions is the major obstacle standing in the way of broad support for biodiesel, and much research has been devoted to its reduction, particularly in light of stringent exhaust emission regulations being imposed on diesel engines over the next few years. Many researchers have reported that CI engines fuelled with pure biodiesel and blends with petrodiesel have higher NOx emissions. This invention solves the problem of higher NOx emissions without affecting the engine brake thermal efficiency. Abstract Biodiesel usage either in pure or blended with petrodiesel has generated considerable interest as an alternate fuel source for CI engine. 20% biodiesel blend is considered by many researchers as a feasible alternative to the petrodiesel in compression ignition engine. Biodiesel blends are characterized by lower viscosity, better combustion properties, and higher Cetane number than blends of their straight vegetable oils. The biodiesel blends normally have lower HC and CO emissions but have higher NOx emissions when used in a Compression ignition engine. In the present experiment, higher NOx emission from a 20% palm biodiesel fuelled compression ignition engine is addressed using palm oil as additive. Palm oil in 2.5%, 5% and 10% are added to 20% palm biodiesel blend and the resultant fuel blends are used in compression ignition engine to evaluate the thermal performance and emissions of the engine. The 20% palm biodiesel blend with 5% palm oil emerged out to be the most suitable blend. It is observed that at 85% load brake thermal efficiency of this blend is 2% higher than 20% palm biodiesel blend and 3% higher than that of diesel. An 8% reduction in NOx emissions is achieved compared to 20% palm biodiesel blend. Background The ever increasing fossil fuel prices and environmental concerns have driven mankind to look for alternatives to these fuels. Vegetable oils have shown a lot of promise in this regard. The use of straight vegetable oils (SVOs) as a fuel for compression ignition engines is restricted by certain unfavorable properties of these oils, particularly their viscosity. This high viscosity results from the high molar masses of the oils and the presence of unsaturated fatty acids. At high temperatures there can be certain problems due to polymerization of unsaturated fatty acids. This occurs when cross-linking starts to occur between molecules, causing the formation of very large agglomerations and consequent gumming. The higher viscosities of SVOs cause poor fuei atomization, which leads to incomplete fuel combustion and carbon deposition on the injector and valve seat, resulting in serious engine fouling [1-5]. There are a number of ways to reduce the viscosity of the vegetable oil. Dilution, micro-emulsification. pyrolysis and transesterification are the four techniques applied to solve the problems encountered with the high fuel viscosity. One of the most common methods used to reduce oil viscosity in the biodiesei industry is called transesterification. Chemical conversion of the SVO to its corresponding fatty ester, namely biodiesei, is called transesterification [6, 7]. The viscosity values of vegetable oils are between 27.2 and 53.6 mm /s, whereas those of biodiesels are between 3.6 and 4.6 mm /s [8]. Biodiesels address many problems faced by SVOs like viscosity, improper spray pattern, improper combustion etc. to a large extent as their viscosities are about 10-14 times less than SVOs. Biodiesei can be used directly or as blends with petrodiesel fuel in a diesel engine. Blends of up to 20% biodiesei mixed with petrodiesel fuel can be used in nearly in all diesel equipment and are compatible with most storage and distribution equipment [8, 9]. However, the wide spread usage of biodiesels is still limited by many factors including their availability, cost and more importantly NOx emissions. The high level of NOx emissions is the major obstacle standing in the way of broad support for biodiesei, and much research has been devoted to its reduction, particularly in light of stringent exhaust emission regulations being imposed on diesel engines over the next few years. Many researchers have reported that CI engines fuelled with pure biodiesei and blends with petrodiesel have higher NOx emissions [10-13].