## 3 Results and Discussions
### Exergy Analysis  
An energy analysis of the engine does not provide enough data to enable the determination of the overall losses and efficiency regarding the engine operation when it is fueled with different fuels. Hence, the exergy analysis complements the thermodynamic analysis of the diesel engine. The exergy analysis was calculated through the experimental data of the diesel engine based on the used fuel and blends. The inlet fuel exergy rate and the outlet exergy (work outlet exergy, exhaust exergy, exergy loss, and exergy destruction) values were determined by dividing each exergy component by the exergy of the fuel, as given in Table 5.  
Figure 5: Energy balance of the engine for each tested fuel. The results for the fuel energy and for the fuel exergy rates shown a similar trend for diesel fuel, E15B35D50, and E15B35 FTD50, as both are functions of the fuel mass flow rate and their LHV. There was an increase in the fuel exergy when the diesel engine was fueled with the E15B35 FTD50 blend in comparison with diesel. Moreover, the inlet exergy rates of the evaluated fuels were increased with respect to the inlet energy rates. The results have shown that the inlet exergy of the tested fuels ranged from 6.7-7.4% higher in comparison with its respective inlet energy. At the respective engine operational condition, the fuel exergy rates for diesel, E15B35D50, and E15B35 FTD50 were found to be in the range of 5.01-5.10 kW, respectively. The higher value for the E15B35 FTD50 blend is attributed to the increased fuel consumption compared to the engine fueled with diesel fuel, which was required to maintain the same indicated power. These findings are in agreement with previous works in the literature using blends of biofuels [29]. [PERSON] et al. [30] reported this behavior is attributed to the increase in fuel consumption, as a result of the decrease in the LHV and an opposite relation between the fuel inlet exergy and the exergy efficiency. The exergy outlet rate within the exhaust gases has slightly decreased when the engine was fueled with the biofuels in the blends. This is because the higher the exhaust gas temperature, the higher is the exhaust gas exergy rate [47]. In the present work, the exhaust gas temperature decreased for the combustion of the E15B35D50 and E15B35 FTD50 blends compared to diesel. A similar result was reported by [PERSON] and [PERSON] [26]. Their research reported that the exhaust exergy was affected by the exhaust gas temperature and that the latter was slightly higher for diesel fuel than for the tested blends of diesel/biodiesel/ethanol. The lost exergy rate through the exhaust gases has decreased by 3.8% for E15B35D50 and 1.9% E15B35 FTD50 blends, respectively. Moreover, the exergy loss rates of the tested fuels were determined as 0.29-0.32 kW. The other exergy losses have shown a similar trend with the energy losses, whereas the E15B35 FTD50 blend presented a higher value than diesel fuel. The exergy destruction rate or irreversibility rate indicates the rate of the available work, which is destroyed due to irreversible processes that occur in the control volume [22]. It is observed that the exergy destruction of the E15B35 FTD50 and E15B35D50 blends were found to be respectively 2.4% and 1.8% higher than for the diesel fuel. Previous investigations have reported that the addition of biodiesel to diesel increases the exergy destruction rate of the blends in comparison with pure diesel [25]. [PERSON] et al. [27] obtained lower values of exergy destruction rate with diesel/biodiesel/butanol blends rather than with diesel fuel. The researchers have attributed this result to the decrease in the combustion temperature promoted by the alcohol addition, although the pure biodiesel fuel and the diesel/biodiesel blend had lower values than the ternary blends. The entropy generation assists in comprehending the system irreversibilities, by supporting the evaluation of the thermal performance of combustion engines [66].