In the current exploration, B20 served as the main fuel while hydrogen was used for dual fuel mode operation. The performance and emissions characteristics of B20 with hydrogen enrichment and 10% and 20% EGR technology are also evaluated and contrasted to conventional fuel.
Performance parameter
Brake thermal efficiency (BTE)
Figure 4 shows the effect of load on BTE. The graph clearly demonstrates that BTE rose by 31.4% in comparison to diesel fuel, which rose by 25.3%, while BTE of B20 and B20 + H2 (6L/m) + 10% EGR was 25% and 24.12%, respectively, at 75% load. BTE was 24.7% for B20, 23.8% for B20 + H2 (6L/m) + 20% EGR, and 24.2% for DF at maximum load. For B20 + H2(6L/m), BTE was 31.4%. The operation's hydrogen enrichment, which enhances fuel combustion, resulted in a rise in BTE [15]. Reduced load range biodiesel presence was accompanied by low hydrogen combustion efficiency. Hydrogen burned with great combustion efficiency when biodiesel was present and the range load was high. EGR was added to all engine loads, which decreased the BTE. This could be explained by the presence of EGR, which lowers the oxygen concentration in intake air and significantly harms combustion [16].
Brake specific energy consumption (BSEC)
Figure.5 shows how BSEC varies as a function of load variation and shows how BSEC declines as load increases. While tidy diesel fuel had a BSEC of 26.02 MJ/kW-hr, which was 11.6% higher than baseline diesel fuel at 25% load, B20 had a BSEC of 27.84 MJ/kW-hr. This was caused by B20's higher viscosity and lower LCV when compared to diesel fuel. As a result, at the same load situation, the BSEC of B20 + H2 (6L/m) (18.79 MJ/ kW-hr) was determined to be 21.6% lower than that of diesel fuel. Under full load conditions, the BSEC of diesel fuel, B20, B20 + H2 (6L/m), B20 + H2 (6L/m) + 10% EGR, and B20 + H2 (6L/m) + 20% EGR were measured as 14.34, 15.05, 16.4, 12.3 and 11.4 MJ/kW-hr, respectively. Due to greater air and hydrogen mixing, B20 + H2 burns more efficiently (6L/m), which results in reduced BSEC [17]. Again increasing and having a negative impact on engine combustion when EGR was operating, BSEC (21.04 MJ/kW-hr) was measured. By reducing engine speed as a result of incomplete combustion as opposed to when there is no EGR, it results in greater energy consumption.
Exhaust gas temperature (EGT)
Figure 6 depicts the impact of engine load on EGT for several diesel fuels, including B20, B20 + H2 (6L/m), B20 + H2 (6L/m) + 10% EGR, and B20 + H (6L/m) + 20% EGR.. As loads grew, EGT climbed as well, reaching its maximum value under conditions of full load. At a 100% load condition, the EGT of diesel fuel, B20, B20 + H2 (6L/m), B20 + H2 (6L/m) + 10% EGR, and B20 + H2 (6L/m) + 20% EGR were found to be 185° C, 195° C, 240° C, 230 ° C, and 220° C, respectively. The faster and better fuel combustion that led to the temperature reaching its peak can be blamed for the enhanced EGT [18]. The reduced EGT after EGR operation compared to B20 + H2 (6L/m) was attributed to inefficient fuel combustion caused by the greater specific heat and a lack of enough oxygen in the intake charge.
Emission parameters
Carbon monoxide (CO)
Figure 7 depicts the variation in CO emission with load and steady engine speed. Engine load increased while CO decreased. The lack of oxygen and low temperature during combustion are the main causes of CO release. Air intake is considerably lower at lower load conditions compared to higher load conditions, which led to higher CO emission. The introduction of the high EGR percentage resulted in an increase in CO emission [19]. The reaction speed, O2 concentration, and in-cylinder temperature were all found to be reduced as the EGR rate was raised. As a result, more CO was released since the oxidation reaction was weaker. When the EGR was 40% compared to B20 + H2 (6L/m) fuel mode at full load, the percentage of CO increased by up to 30%, as can be shown.
HC emission
Unburned hydrocarbon (UHC) emission from all evaluated fuels is shown in Fig. 8 as a result of load fluctuation. The image made it very evident that load increased resulted in a decrease in UHC emission. When the engine is not running, the UHC emissions of diesel fuel, B20, B20 + H2 (6L/m), B20 + H2 (6L/m) + 10% EGR, and B20 + H2 (6L/m) + 20% EGR are measured as 65 ppm, 72 ppm, 53 ppm, 84 ppm, and 124 ppm, respectively, whereas when the engine is running at full capacity, they are measured as 113 ppm. There is also the additional finding that using B20 + H2 (6L/m) fuel, the HC emission rose as the EGR percentage increased. Due to the low amount of overly accessible oxygen, rich air fuel mixtures burn more slowly and produce more UHC, which causes a rise in HC. When the EGR was 10% or 20%, the UHC climbed to 15% [20].
Nitrogen oxide (NO X )
The effect of NOX emission with variable engine load and constant engine speed is depicted in Fig. 9. NOX emission was seen to be at its greatest during hydrogen enhancement for B20 without an EGR system (i.e., B20 + H2 (6L/m). The increased NOX emission at full load varied from 950 to 1450 ppm. This result can be attributed to the increased combustion temperature that enhanced combustion introduced into the combustion chamber [21]. The NOX emission for B20 + H2 (6L/m) + 10% EGR was found to be 1003 ppm, which is lower than the 1450 ppm at 100% load for B20 + H2 (6L/m) without EGR. By reducing the flame temperature during combustion, EGR lowered NOX generation by 20%. This result is due to the intake charge's oxygen concentration being reduced by the recirculating gas. With B20 + H2 (6L/m) gasoline, EGR rates ranging from 10–20% were used. EGR rate increases reduce NOx emissions. While the addition of EGR lowers the combustion temperature and subsequently the combustion efficiency, resulting in decreased NOx, the reaction becomes the opposite when the hydrogen is supplemented with the fuel.
Combustion analysis
Cylinder pressure
In all of the fuels that were evaluated, the cylinder pressure in relation to crank angle diagrams are shown in Fig. 10 under conditions of maximum load. With regard to diesel engines, the amount of fuel burned during the premixed combustion phase has a significant impact on the peak pressure at the start of the combustion rate. At the time of the delay period, the premixed or uncontrolled combustion phase is handled by both the ignition delay period and the preparation of the mixture. For B20, B20 + H2 (6L/m), 10% EGR, and 20% EGR at full load, the peak pressure readings were 74.32, 68.54, 67.35, and 67.14 bars, respectively. As can be seen, compared to other modes, H2 enrichment allows for a larger peak pressure. This is as a result of H2's improved combustion and shorter ignition delay time. A key influence is played by the installation of EGR and its emphasis on the peak pressure and ignition delay time [22].
Heat Release Rate
Figure 11 depicts the curve for the Heat Release Rate (HRR) with Crank Angle for Different Percentages of EGR Addition with B20H2 (6L/m) Dual Fuel Mode. It is clear to observe that 65.4 J/deg was the HRR with the highest value. As opposed to 47.64 J/deg CA for the dual fuel mode using B20H2 (6L/m). When using 20% EGR. It has been determined that the amount of heat released when the fuel was enriched with hydrogen was not increased by the addition of EGR. The HRR is held responsible for the high peak pressure that results from premixed combustion. Two primary parameters that affect the combustion processes in EGR operation are the calibre of the pilot biodiesel fuel spray and the mixing of the hydrogen and EGR in the cylinder charge. Due to the dilution effect during the premixed combustion phase, EGR decreased the HRR. This restricts the turbulent flame propagation from the pilot ignite zones to the cylinder charge. It also affects the amount of heat released during combustion [23].