## 3 Result and Discussion
### Exergy Analysis  
Exergy analysis may help design more effective energy systems by reducing the system's irreversibilities. For use with diesel fuel, the exergies related to input energy, generated power, heat loss from exhaust gases, other heat loss and system irreversibilities or destruction of input energy were assessed during the exergy study [24; 27; 50]. The differences in thermal and exergy efficiency for test fuels with 1500 RPM speed, 17.5 CR and full load are shown in Figure 12  
Figure 11: Energy distribution of \(\mathrm{SBF}_{100}\) fuel under different loading conditions.  
The experimental engine's exergy efficiency and thermal efficiency both followed the same pattern for all test fuel blends. Exergy efficiency has a lower value under identical circumstances than thermal efficiency. Between these two there was a 3-6% difference. Low energy effectiveness was brought on by the conversion of just a small quantity of work exergy and the destruction of most of the provided fuel exergy, which is also called inlet exergy rate [30,58], by the fuel. Diesel fuel has a higher value of both efficiencies as compared to other test fuels because of the higher calorific content of diesel [59]. When the amount of biodiesel in the mixture is raised, the exergy flow is (slightly) decreased as a result of increased fuel consumption. Due to the fuel's chemical makeup and lower calorific content, this has occurred.  
The exergy analysis depicted in Figure 13 shows that for pure diesel, brake power exergy was 31.06%, exergy exhaust rate was 18.35%, exergy destruction was 46.14% and exergy rate by heat transfer was 4.43%. For other fuels, the brake power was found to have a declining trend and decreased by 30.79%, 30.57%, 30.35%, 30.09%, and 29.75% for \(\text{SBF}_{20}\), \(\text{SBF}_{40}\), \(\text{SBF}_{60}\), \(\text{SBF}_{80}\), and \(\text{SBF}_{100}\) respectively. This result shows that biodiesel blends lead to a reduction in power output due to their lower calorific value [60]. Exhaust exergy and exergy transfer by heat were following an increasing trend. Exhaust gas exergy flow rate increased as a result of the fuel mixture, presumably as a result of incomplete combustion brought on by the addition of more long-chain hydrocarbons to the fuel, and was observed to increase by 18.35%, 18.4%, 18.46%, 18.54%, 18.7%, and 18.86% for exergy exhaust rate and by 4.43%, 4.5%, 4.56%,4.62%, 4.69% and 4.77% for the exergy rate transfer, for \(\text{SBF}20\), \(\text{SBF}40\), \(\text{SBF}60\), \(\text{SBF}80\), and \(\text{SBF}100\), respectively. Most input energy is lost during combustion, and only a tiny portion of it can be transformed into exergetic work during an engine cycle. The major portion of input exergy lost is in the form of exergy destruction [23,59], which was observed as an increasing trend with the increase of blend ratio, was found to be 46.14%, 46.29%, 46.39%, 46.47%, 46.51%, and 46.61% for \(\text{SBF}_{20}\), \(\text{SBF}_{40}\), \(\text{SBF}_{60}\), \(\text{SBF}_{80}\), and \(\text{SBF}_{100}\) respectively. The exergy analysis shows that engine operation was more sustainable for diesel fuel than other biodiesel blends [24,61]. \(\text{SBF}_{20}\) shows the closest result to diesel fuel. \(\text{SBF}_{20}\) biodiesel blends have good potential for working in a diesel engine.  
Figure 12: Thermal and Energetic Efficiency of different biodiesel blends.