SOME INVESTIGATIONS ON USE OF RENEWABLE FUEL IN COMPRESSION IGNITION ENGINE

Abstract

Compression ignition engines are a primary source of power in the transportation sector, which, unfortunately, generate greenhouse gases, posing a significant threat to both the environment and human health. As a response to this concern, the exploration of alternatives to diesel has gained prominence due to their potential to mitigate greenhouse gas emissions and enhance energy security. Vegetable oils are abundantly available in India and has garnered the attention of the Indian government for conversion into biofuels. Biofuels are generally produced by the transesterification process. By using this process, the raw vegetable oil is converted to its methyl/ethyl ester and its viscosity is significantly reduced. However, the process posses some challenges like increasing the cost of biofuel production, and low utilization of the by-products. Low viscosity vegetable oils that do not need to be trans-esterified have been previously used for operating the diesel engine. Pine oil and eucalyptus oil are two such fuels that have the potential to replace diesel. This research evaluates the viability of using the two oils as alternatives for diesel engine by examining their impact on combustion, performance, and emission in comparison to traditional diesel. The aim of the study is to optimize the ratio of these oils so as to create an ideal blend with enhanced fuel qualities. Hence, P5E5D90 (5% pine oil, 5% eucalyptus oil and 90% diesel), P10E10D80 (10% pine oil, 10% eucalyptus oil and 80%diesel), P15E15D70 (15% pine oil, 15% eucalyptus oil and 70%diesel), P50E50 (50% pine oil, 50% eucalyptus oil), E20D80 (20% eucalyptus oil and 80% diesel), P20D80 (20% pine oil and 80% diesel), ED20D80 (20% distilled eucalyptus oil and 80% diesel), P20D80 (20% distilled pine oil and 80% diesel) and PD10ED10D80 (10% distilled pine oil, 10% distilled eucalyptus oil and 80%diesel) fuel samples were selected. In the first phase, the research delves into the physicochemical characteristics of the fuel samples such as calorific value, density, flash point, surface tension and kinematic viscosity. Some investigations on use of renewable fuel in compression ignition engine |P a g e vii The properties of the fuel meet the relevant ASTM standards. To analyse the composition of the fuel samples and their relationship with engine performance, GC-MS analysis was carried out. The major constituents of pine oil were carene (46.53%), alpha-Terpineol (14.79%), and limonene (9.6%). While, eucalyptus oil consists of carene (15.69%), cyclopentene (25.28%), Limonene (6.68%), Bicyclo (3.68%), and Citronellene (2.24%). Then the shelf life of the fuel samples was tested. The fuel samples underwent a one-year stability assessment, during which the changes in calorific value, viscosity, and density were monitored. These parameters showed minimal alterations over time, and the rate of change was low. The second phase involved efforts to fine-tune the combination ratios of plant-based oils, aiming for an optimal diesel blend with enhanced fuel properties. The brake thermal efficiency with blend of only pine oil was lowest. With equal blending of pine and eucalyptus oil, the thermal efficiency was lower than diesel fuel engine operation. The lowest efficiency was observed with P20D80. With equal blend of only pine and eucalyptus oil the efficiency was lower than diesel at all loads. When the equal blends of pine and eucalyptus oil were mixed with diesel, the thermal efficiency increases with an increasing proportion of the biofuels in the blend. The thermal efficiency was highest with P10E10D80 blend at all the load conditions. These fuel blends exhibited an earlier onset of heat release compared to baseline diesel oil due to their lower kinematic viscosity and flash point. Furthermore, the blends showed a higher peak heat release than diesel. Test blends demonstrated reduced HC, CO, and smoke emissions, ranging from 23% to 48% less than the baseline, with higher blend proportions resulting in lower emissions. In all test samples, NOx emissions surpassed diesel, with the P10E10D80 blend showing an 8.60% increase above the baseline. With the blend of distilled biofuels and diesel, the thermal efficiency was found to increase with increase in load. Also, the efficiency was higher than the non-distilled blends. PD10ED10D80 demonstrated the highest engine efficiency due to the presence of all seven Some investigations on use of renewable fuel in compression ignition engine |P a g e viii major constituents, with Carene being the most abundant at 30.52%. The inclusion of Citronellene and bicyclo [2.2.1] heptane in the PD10ED10D80 blend resulted in increased brake thermal efficiency. PD10E10D80 biofuel blend stands out as a superior fuel offering advantages in terms of combustion characteristics (max. HRR: 71.94 J/°CA, max. in-cylinder pressure: 79.63 bar), emissions reduction (HC emission decreased by 14.70%, CO emission decreased by 13%, smoke opacity reduced by 20.14%, and NOx emission increased by 8.79%). It is thus seen that the refined biofuels represent a promising solution for cleaner and more efficient energy in the transportation sector, surpassing the non-distilled alternative in multiple critical aspects.From the previous experiments, it was observed that the distilled biofuel blend PD10ED10D80 performed better than P10E10D80 blend in terms of combustion, performance and emission. However, the oxides of nitrogen emission were higher with the distilled biofuels blend. Also, the cost of distillation would further increase the cost of the blend. Hence, P10E10D80 blend was used for further exploration. In the last phase of the experimentation, for further substitution of diesel with bio-oils, methanol was fumigated in the intake manifold of the engine. The flow rate of methanol was varied from 10% to a maximum of 56%. The results reveal that higher percentages of methanol substitution at full load resulted in improved thermal efficiency and combustion characteristics. The energy consumption of the experimental engine reduced by 17% when 39% methanol substitution was carried out at full load condition. Simultaneously a reduction in emissions except NOx emission was also observed. NOx emission was found to increase by approximately 16% at 40% substitution levels. The smoke opacity was also found to decrease by approximately 10% at maximum methanol substitution as compared to engine operation with the blend in single fuel mode. In conclusion, this study shows that up to 50% substitution of diesel at full load condition with pine oil, eucalyptus oil and methanol is possible without much affecting the engine performance.