Assessment of CI Engine Performance and Exhaust Air Quality Outﬁtted with Real-Time Emulsion Fuel Injection System

: The main target of the current research work is effectively eliminating fossil fuel dependency and improving the exhaust air quality of conventional Compression Ignition (CI) engines. This research paper demonstrates for the ﬁrst time that a nanoﬂuid (water without surfactant) stored in separate tanks can be quantiﬁed, collected, and immediately emulsiﬁed by a high shear mixer before transfer into the combustion chamber of a diesel engine. The experiment was carried out under different load states (25%, 50%, 75% and 100%) with a constant speed of 1500 rpm. Biofuel was extracted from citronella leaves using an energy-intensive process. The 5% water share was used for preparing the biofuel emulsion and nano-biofuel emulsion. A cobalt chromate nanoadditive was used to make the nanoﬂuid. An experimental investigation was performed with prepared test fuels, namely, ultra-low sulphur diesel (ULSD), 100% Citronella (B100), surfactant-free Diesel emulsion (SDE), surfactant-free bioemulsion (SBE), and Surfactant free nano-bioemulsion (SNBE), in a test engine. The properties of the sample test fuels was ensured according to EN and ASTM standards. The observation performance results show that the SNBE blend exhibited lower BTE (by 0.5%) and higher SFC (by 3.4%) than ULSD at peak load. The emission results show that the SNBE blend exhibited lower HC, CO, NO x , and smoke emissions by 23.86%, 31.81%, 2.94%, and 24.63%, respectively, compared to USD at peak load. The CP and HRR results for SNBE were closer to ULSD fuel. Overall, the novel concept of an RTEFI (Real-time emulsion fuel injection) system was proved to be workable and to maintain its beneﬁts of better fuel economy and greener emissions.


Introduction
Over the past twenty years, the rate of air pollution has grown rapidly and fossil fuels are becoming depleted due to the growth of industrialization and the drastic increase in the number of transport vehicles. The drain on global fossil energy sources is assessed as being likely to increase over the next ten years, and thought should be given to long-term utilization as well [1,2]. Among the many types of conversion equipment, the basic fuel engine has particular benefits, such as durability, reliability, power output, energy consumption, etc., Nevertheless, diesel fuel engines create high amounts of smoke emissions and nitrogen oxide [3,4]. At present, government emission regulations are very stringent in order to preserve human and environmental health. For these reasons, the scientific community seeks to discover renewable and emission-free alternate fuels for basic engines [5].

Preparation and Characterization of Citronella Oil
Citronella (Cymbopogon nardus) oil was extracted through an energy-intensive process. The layout out of the energy-intensive setup is shown in Figure 2. Figures 3 and 4 inform the chemical bonds, structure, and functional group present in Cymbopogon nardus oil. A complete study was previously made in our earlier publication (Krishnamoorthy et al. [30]) of oil extraction, FTIR, and GCMS. and rotator. The prepared emulsion fuel is then supplied to an ultrasonic transducer for introducing vigorous ultrasonic waves before the emulsifier-free emulsion fuel flows through into the diesel engine via the emulsion fuel supply line. The more prominent shear blenders and ultrasonic transducers are set by the regulator. The solenoid valve is used to control the supply of the water and oil fraction, which is shown in Figure 1 as well. The RTEFI system was placed closer to the fuel feed arrangement of the engine in order to eliminate separation of the prepared fuel phase.

Synthesis of Cobalt Chromite (COCr 2 O 4 ) Nanoadditive
A redox solution at 250 • C, the commencement of solution combustion, and the end product are the three steps in this process. In a 1000 mL borosilicate container, cobalt (II) nitrate hexahydrate (Co(NO 3 ) 2 ·6H 2 O, Sigma-Aldrich 99% Purity) and chromium (III) nitrate nonahydrate (Cr(NO 3 ) 3 ·9H 2 O, Sigma-Aldrich 99% purity) were taken as the respective starting materials according to stoichiometric requirements, and were dissolved in the minimum amount of deionized water with continuous stirring. Then, a reducing agent of glycine fuel was added to the aforementioned solution and the solution was stirred at 200 rpm for 15 to 30 min. After that, the solution was heated with a hotplate and the temperature was elevated to 90 • C to allow for the gradual evaporation of water until a gel was produced. Furthermore, the gel was steadily heated to 200 • C until a flame and gas

Preparation and Characterization of Citronella Oil
Citronella (Cymbopogon nardus) oil was extracted through an energy-intensive process. The layout out of the energy-intensive setup is shown in Figure 2. Figures 3 and 4 inform the chemical bonds, structure, and functional group present in Cymbopogon nardus oil. A complete study was previously made in our earlier publication (Krishnamoorthy et al. [30]) of oil extraction, FTIR, and GCMS.         An X-ray diffraction (XRD) test was conducted for phase identification of the prepared nano-cobalt chromite. The test results in a picture output to conform and verify the crystal structure of the material. Thus, for the prepared nano-cobalt chromite compound the XRD pattern was recorded by X-ray diffractometer, with copper employed as the target material (with Cu Kα as a diffraction source) to explore the sample. It can be seen that the output of the prepared cobalt chromite compound matches the simulated output well. However, an impurity phase screening at near~33o belongs to a Cr 2 O 3 (@), which means that the single-step synthesis of the Solution Combustion technique does not offer a greater pure phase of CoCr 2 O 4 when major amounts of Cr ion are quickly oxidized to form Cr 2 O 3 precipitate. The crystallite size of the prepared cobalt chromite was found to be~22 nm as calculated by the Scherrer formula where D p is the size of crystallite in nm, θ is the degree theta, and β is the radian.

SEM Analysis
SEM microscopy was used for elemental analysis of the prepared cobalt chromite compound. Figure 5a is a pictorial representation of the SEM image of the prepared cobalt chromite compound from an SEM analyzer obtained using an X-ray spectrometer at magnification 20,000× to 167,000×. The experimental analysis was carried out at 8.00 kV and the acquired outcomes were a notable collection of particles with an important poriferous nature.

EDX Analysis
From the point of view of energy content, the content mass is quite natural, which allows the growth of crystallites. Figure 5b exemplifies the Energy Dispersive X-ray (EDX) spectrum of prepared the cobalt chromite compound, which shows that the cobalt, chromium, and

Test Fuel Preparation
In the current work, test fuel was prepared using two techniques. In the first technique, a nanoemulsion, fuel was prepared using water, an emulsifier, and nanopowder. In the second technique, the novel concept of RTEFI was introduced to prepare and supply the test fuel. The thermal property of test fuel is shown in Table 2.

Test Fuel Preparation
In the current work, test fuel was prepared using two techniques. In nique, a nanoemulsion, fuel was prepared using water, an emulsifier, and In the second technique, the novel concept of RTEFI was introduced to supply the test fuel. The thermal property of test fuel is shown in Table 2. Table 2. Thermal, physical, and chemical properties of test fuel.

Test Fuel Preparation
In the current work, test fuel was prepared using two techniques. In the first technique, a nanoemulsion, fuel was prepared using water, an emulsifier, and nanopowder. In the second technique, the novel concept of RTEFI was introduced to prepare and supply the test fuel. The thermal property of test fuel is shown in Table 2.

Configuration of the Test Ring
For further investigation, a one-cylinder conventional Kirloskar-made naturally aspirated steady speed direct injection diesel engine with a power output of 5.2 kW was used. The fuel tank was 6.5 L, with the air drawn inside the cylinder through the inlet manifold during the suction stroke. The detailed specifications of the engine are provided in Table 3. An inline mixing system, the RTEFI system, was attached close to the mechanical fuel injection structure. Pressure sensors were placed on the cylinder head to measure the combustion parameters.
A smoke analyzer and AVL DI gas analyzer were employed to quantify the tailpipe emissions. The emission analyzer specifications are sown in Table 4; Table 5 shows the Test Matrix.

Ambiguity Examination
Commonly, error arises in an instrument due to factors such as instrument condition, environmental conditions, the type of observations being made, and the test procedure. Dissimilarity among instrument makers, calibration techniques, and data collection procedures can lead to experimental uncertainty. Uncertainty analysis is used to avoid variations in the experimental results. The ambiguity among diverse measuring instruments and parameters is shown in Table 6.  under diverse load states. From the graph, it can be seen that all the test fuels display increased BTE with increased engine loads. Both the SDE and SBE emulsions and the B fuel have lower BTE correlated with D. Nevertheless, SNBE fuel exhibits slightly higher BTE than SBE, which is due to the positive impact of the cobalt chromite additive [43,44]. There is significant improvement of BTE at high load conditions when fuelled with D, SDE, SBE, and SNBE, 2.22%, 1.26%, 1.64%, and 2.04%, respectively, compared to B100. Additionally, both emulsion fuels are combustible effectively because of micro-explosions and the secondary atomization of fuel. The BTE for D, SDE, SBNE, SBE, and B100 is 31.14%, 30.18%, 30.96%, 30.56%, and 28.92%, respectively, at peak load condition. This outcome might be a reason for the fast evaporation interaction of H 2 O, which is at first introduced in oil drops as exceptionally fine beads, which positively influences the air/fuel fixing and thus enhances brake thermal efficiency. Another important result is that the emulsion fuels had a higher ignition lag, which allows sufficient duration to physically prepare the test fuel. In addition, this result may be a positive influence on catalytic cracking of the hydrocarbon chain and the O 2 buffer property of cobalt chromite nanoparticles.

Emission Output Response
The nitrogen oxide emission evaluation of the adopted test fuel and contrast with diesel under diverse load states are shown in Figure 9. Generally, a CI engine emits The BSFC is a significant parameter; it is an indicator that measures engine effectiveness and the amount of fuel utilization inside the engine to develop a certain power output. Figure 8 shows that the BSFC output for D, SDE, SBNE, SBE, and B100 is 292 kJ/kW-h, 326 kJ/kW-h, 302 kJ/kW-h, 312 kJ/kW-h, and 345 kJ/kW-h, respectively, at top load state. The D fuel had better fuel consumption than other test fuels due to the high heat content present in D fuel. There is a significant improvement in BSFC when fuelled with D, SDE, SBE, and SNBE, respectively, 15.36%, 5.51%, 9.57%, and 12.46% compared to B100 under high load conditions. These explanations are consistent with Krishnamoorthy et al. [9], where BFO and BFO emulsion fuel had poor BSFC when correlated with diesel. On the whole, the SNBE fuel exhibits considerable improvement in performance output response as a result of greater dispersion of cobalt chromite nanopowder at the combustion phase.

Emission Output Response
The nitrogen oxide emission evaluation of the adopted test fuel and contrast with diesel under diverse load states are shown in Figure 9. Generally, a CI engine emits more NO x emission than the SI engine owing to the higher combustion temperature caused by the high oxygen presence inside the CC. The NO x output for D, SDE, SBNE, SB, E and B is 849 ppm, 847 ppm, 824 ppm, 839 ppm, and 852 ppm, respectively, at the top load state. From the graph it can be seen that the B fuel delivers more NO x emissions due to an enriched O 2 proportion. It can be seen that B fuel exhibits 50% greater nitrogen oxide formation relative to diesel at peak load state. At 10%, the water concentration in SBE lowers NO x formation by 25% compared to pure B fuel at full load owing to LHV and higher ID of SBE. Furthermore, the addition of the nanoadditive in SBE promotes lower NO x formation by about 10%. The SBNE blend exhibits the maximum NO x reduction due to its positive property of a high surface area to volume ratio [45][46][47][48].

Emission Output Response
The nitrogen oxide emission evaluation of the adopted test fuel and contrast with diesel under diverse load states are shown in Figure 9. Generally, a CI engine emits more NOx emission than the SI engine owing to the higher combustion temperature caused by the high oxygen presence inside the CC. The NOx output for D, SDE, SBNE, SB, E and B is 849 ppm, 847 ppm, 824 ppm, 839 ppm, and 852 ppm, respectively, at the top load state. From the graph it can be seen that the B fuel delivers more NOx emissions due to an enriched O2 proportion. It can be seen that B fuel exhibits 50% greater nitrogen oxide formation relative to diesel at peak load state. At 10%, the water concentration in SBE lowers NOx formation by 25% compared to pure B fuel at full load owing to LHV and higher ID of SBE. Furthermore, the addition of the nanoadditive in SBE promotes lower NOx formation by about 10%. The SBNE blend exhibits the maximum NOx reduction due to its positive property of a high surface area to volume ratio [45][46][47][48].  (SDE), surfactant-free bioemulsion (SBE), and surfactant-free nano-bioemulsion (SNBE) under varied load states. The HC output for D, SDE, SBNE, SBE, and B is 76 ppm, 67 ppm, 58 ppm, 61 ppm, and 72 ppm, respectively, at the top load state. At low load, it can be seen that the B blend exhibits lower HC formation compared with other test fuels, as the B blend has higher O2 and lower carbon content, which can enhance the proper process of combustion. On the other hand, the SBE blend had greater HC formation than the B blend due to the LHV of water present in the SBE blend, resulting in incomplete combustion. At high load states the SBE blend emits lower HC emission from the CI engine tailpipe than the B blend, owing to the positive impact of micro-explosions and secondary atomization [49][50][51][52]. The cobalt chromite nanoadditive added to the SBE blend considerably reduce HC formation and positively enhance the ignition lag, heat transfer rate, and explosion rate, resulting in fully complete combustion. On the whole, at the maximum load condition the SBNE blend exhib-  can be seen that the B blend exhibits lower HC formation compared with other test fuels, as the B blend has higher O 2 and lower carbon content, which can enhance the proper process of combustion. On the other hand, the SBE blend had greater HC formation than the B blend due to the LHV of water present in the SBE blend, resulting in incomplete combustion. At high load states the SBE blend emits lower HC emission from the CI engine tailpipe than the B blend, owing to the positive impact of micro-explosions and secondary atomization [49][50][51][52]. The cobalt chromite nanoadditive added to the SBE blend considerably reduce HC formation and positively enhance the ignition lag, heat transfer rate, and explosion rate, resulting in fully complete combustion. On the whole, at the maximum load condition the SBNE blend exhibits greater HC emission reduction than all other test fuels due to its positive property of a high surface area to volume ratio. Generally, the magnitude of CO formation was minimal in the CI engine compared with the SI engine. Usually, the formation of CO emissions depends on the air/fuel ratio in the IC engine. Figure 11 shows CO formation for Diesel (D), Biofuel (B), surfactant-free diesel emulsion (SDE), surfactant-free bioemulsion (SBE) and surfactant-free nano-bioemulsion (SNBE) at varied load ranges. CO decreased with increased engine loads from 0% to 100% for all the test fuels, owing to peak in-cylinder temperature being associated with higher load conditions. At high load state, the SBE blend emits lower CO emission from the CI engine tailpipe than the B blend, owing to the positive impact of micro-explosions and secondary atomization. The cobalt chromite nanoadditive added to the SBE blend considerably reduce CO formation and positively enhance the ignition lag, heat transfer rate, and explosion rate, ad resulting in fully complete combustion [53][54][55][56]. On the whole, at the maximum load condition the SBNE blend exhibits greater CO emissions reduction than all other test fuels due to its positive property of a high surface area to volume ratio. Generally, the magnitude of CO formation was minimal in the CI engine compared with the SI engine. Usually, the formation of CO emissions depends on the air/fuel ratio in the IC engine. Figure 11 shows CO formation for Diesel (D), Biofuel (B), surfactantfree diesel emulsion (SDE), surfactant-free bioemulsion (SBE) and surfactant-free nanobioemulsion (SNBE) at varied load ranges. CO decreased with increased engine loads from 0% to 100% for all the test fuels, owing to peak in-cylinder temperature being associated with higher load conditions. At high load state, the SBE blend emits lower CO emission from the CI engine tailpipe than the B blend, owing to the positive impact of microexplosions and secondary atomization. The cobalt chromite nanoadditive added to the SBE blend considerably reduce CO formation and positively enhance the ignition lag, heat transfer rate, and explosion rate, ad resulting in fully complete combustion [53][54][55][56]. On the whole, at the maximum load condition the SBNE blend exhibits greater CO emissions reduction than all other test fuels due to its positive property of a high surface area to volume ratio. Figure 12 shows the smoke formation for Diesel (D), Biofuel (B), surfactant-free diesel emulsion (SDE), surfactant-free bioemulsion (SBE), and surfactant-free nano-bioemulsion (SNBE) under varied load range. In order to uphold the constant speed of the engine under the all load states the engine allows the incremental fuel to burn, which influences smoke formation. The graph shows that the biofuels had lower smoke formation than diesel at all load states, which is due to the availability of the oxygen proportion in B fuel. Furthermore, the additional of water content in biofuel diminishes the smoke output compared to diesel thanks to improved atomization [57,58]. At a high load state, the SBE blend emits less smoke from the CI engine tailpipe than the B blend, owing to the positive impact of microexplosions and secondary atomization. The cobalt chromite nanoadditive added to the SBE blend considerably reduces smoke formation and positively enhances the ignition lag, heat transfer rate, and explosion rate, resulting in fully complete combustion [59][60][61]. On the whole, at the maximum load condition the SBNE blend exhibits greater smoke emission reduction than all other test fuels thanks to its positive property of a high surface area to volume ratio [62][63][64].
Sustainability 2022, 14, x FOR PEER REVIEW 14 of 21 Figure 11. Carbon monoxide emissions vs. brake power. Figure 12 shows the smoke formation for Diesel (D), Biofuel (B), surfactant-free diesel emulsion (SDE), surfactant-free bioemulsion (SBE), and surfactant-free nano-bioemulsion (SNBE) under varied load range. In order to uphold the constant speed of the engine under the all load states the engine allows the incremental fuel to burn, which influences smoke formation. The graph shows that the biofuels had lower smoke formation than diesel at all load states, which is due to the availability of the oxygen proportion in B fuel. Furthermore, the additional of water content in biofuel diminishes the smoke output compared to diesel thanks to improved atomization [57,58]. At a high load state, the SBE blend emits less smoke from the CI engine tailpipe than the B blend, owing to the positive impact of micro-explosions and secondary atomization. The cobalt chromite nanoadditive added to the SBE blend considerably reduces smoke formation and positively enhances the ignition lag, heat transfer rate, and explosion rate, resulting in fully complete combustion [59][60][61]. On the whole, at the maximum load condition the SBNE blend exhibits greater smoke emission reduction than all other test fuels thanks to its positive property of a high surface area to volume ratio [62][63][64].

Combustion Output Response
In a diesel engine the cylinder pressure commonly depends on various factors, namely, the equivalence rate, A/F rate, evaporation rate, ignition delay and CD period, and fuel burned separately during the premixed burning stage. Figure 13 shows the

Combustion Output Response
In a diesel engine the cylinder pressure commonly depends on various factors, namely, the equivalence rate, A/F rate, evaporation rate, ignition delay and CD period, and fuel burned separately during the premixed burning stage. Figure 13 shows the variation in Cylinder Pressure (CP) with respect to the crank angle for Diesel (D), Biofuel (B), surfactantfree diesel emulsion (SDE), surfactant-free bioemulsion (SBE), and surfactant-free nanobioemulsion (SNBE) under varied load ranges. The maximum CP output for D, SDE, SBNE, SBE, and B100 is 65 bar, 67 bar, 61 bar, 64 bar, and 63 bar, respectively, at the top load state. Both SDE and SBE emulsion and B fuel show lower CP correlated to D due to the CV of D fuel. Nevertheless, SNBE fuel exhibits slightly higher CP than SBE due to the positive impact of cobalt chromite additive. Additionally, emulsion fuel combusts effectively thanks to secondary atomization and micro-explosions. This result may be a reason for the fast process of H 2 O evaporation that is organically introduced in oil drop attacks as exceptionally fine drops, which influences air/fuel fixing and enhances brake thermal efficiency. Another important element of this result is that emulsion fuel has a higher ignition lag, which allows time to physically prepare the test fuel. This result may show a positive influence on catalytic cracking of the hydrocarbon chain and the O 2 buffer property of cobalt chromite nanoparticles [62][63][64]. HRR is the measure of heat radiated by most of the burn throughout the combustion stage inside the base engine cylinder. In the present work, the HRR was calculated from the CP with respect to the Crank angle (CA) using following the expression equation where: = Net heat release rate in (kJ/m 3 CA); V = Instantaneous volume in (m 3 ); P = Instantaneous pressure in (bar); = ratio of specific heat. Figure 14 shows the variation in HRR with respect to the crank angle for Diesel (D), Biofuel (B), surfactant-free diesel emulsion (SDE), surfactant-free bioemulsion (SBE), and surfactant-free nano-bioemulsion (SNBE) under varied load ranges. Both SDE and SBE emulsion and B fuel show lower CP correlated to D due to the CV of D fuel. Nevertheless, SNBE fuel exhibits a slightly higher HRR than SBE due to the positive impact of the HRR is the measure of heat radiated by most of the burn throughout the combustion stage inside the base engine cylinder. In the present work, the HRR was calculated from the CP with respect to the Crank angle (CA) using following the expression equation where: dQnet dθ = Net heat release rate in (kJ/m 3 CA); V = Instantaneous volume in (m 3 ); P = Instantaneous pressure in (bar); γ = ratio of specific heat. Figure 14 shows the variation in HRR with respect to the crank angle for Diesel (D), Biofuel (B), surfactant-free diesel emulsion (SDE), surfactant-free bioemulsion (SBE), and surfactant-free nano-bioemulsion (SNBE) under varied load ranges. Both SDE and SBE emulsion and B fuel show lower CP correlated to D due to the CV of D fuel. Nevertheless, SNBE fuel exhibits a slightly higher HRR than SBE due to the positive impact of the cobalt chromite additive.

Conclusions
The performance, emissions, and combustion of citronella biodiesel blended with water and a nanoadditive were investigated in a single-cylinder diesel engine with attached RTEFI. The obtained conclusions are listed below.
• The BTE of the engine was enhanced with SBE fuel by 1.64% and with SNBE fuel by 2.04% compared to unadulterated Citronella fuel at the most extreme load range. In all cases, conventional fuel activity displayed the greatest BTE compared to all other test fuels • At the maximum load range, the BSFC of the engine was enhanced with SBE and SNBE fuel by 9.57% and 12.46%, respectively, compared to pure Citronella fuel. and was. The respective BSFC for the D, SDE, SBE, and SNBE fuels was 292 kJ/kW-h, 326 kJ/kW-h, 312 kJ/kW-h, and 302 kJ/kW-h. • The SDE, B100, SBE, and SNBE fuels had a significantly reduced HC in the tailpipe, by 13.16%, 5.27%, 19.75%, and 23.68%, respectively, and CO in the tailpipe. by 13.65%), (4.54%), (22.73%), and (31.82%), respectively, compared with conventional diesel fuel at the peak load condition. However, the SDE blend exhibited higher HC and CO emissions than Diesel fuel. • At all load ranges, the NOx emission trend was lower for SBE than for diesel and the SDE blend (by 1.18% and 2.95%, respectively) as well as for SNBE (by 0.94% and 2.72%, respectively). However, pure citronella fuel showed greater NOx formation than SBE fuel. • A significant improvement in the opacity of smoke was noted for both emulsion bio-fuels relative to B100 fuel, with a respective decrease of 10.77% and 20%, while Diesel fuel had increased smoke formation compared to both the nanoemulsion and emulsion fuels. • CP and HRR increased for both nanoemulsion and emulsion SBE and SBNE fuels compared to convention diesel fuel; however, B100 fuel had minimal CP and HRR compared to Diesel fuel.

Conclusions
The performance, emissions, and combustion of citronella biodiesel blended with water and a nanoadditive were investigated in a single-cylinder diesel engine with attached RTEFI. The obtained conclusions are listed below.

•
The BTE of the engine was enhanced with SBE fuel by 1.64% and with SNBE fuel by 2.04% compared to unadulterated Citronella fuel at the most extreme load range. In all cases, conventional fuel activity displayed the greatest BTE compared to all other test fuels • At the maximum load range, the BSFC of the engine was enhanced with SBE and SNBE fuel by 9.57% and 12.46%, respectively, compared to pure Citronella fuel. and was. The respective BSFC for the D, SDE, SBE, and SNBE fuels was 292 kJ/kW-h, 326 kJ/kW-h, 312 kJ/kW-h, and 302 kJ/kW-h.

•
The SDE, B100, SBE, and SNBE fuels had a significantly reduced HC in the tailpipe, by 13.16%, 5.27%, 19.75%, and 23.68%, respectively, and CO in the tailpipe. by 13.65%), (4.54%), (22.73%), and (31.82%), respectively, compared with conventional diesel fuel at the peak load condition. However, the SDE blend exhibited higher HC and CO emissions than Diesel fuel. • At all load ranges, the NO x emission trend was lower for SBE than for diesel and the SDE blend (by 1.18% and 2.95%, respectively) as well as for SNBE (by 0.94% and 2.72%, respectively). However, pure citronella fuel showed greater NO x formation than SBE fuel. • A significant improvement in the opacity of smoke was noted for both emulsion bio-fuels relative to B100 fuel, with a respective decrease of 10.77% and 20%, while Diesel fuel had increased smoke formation compared to both the nanoemulsion and emulsion fuels. • CP and HRR increased for both nanoemulsion and emulsion SBE and SBNE fuels compared to convention diesel fuel; however, B100 fuel had minimal CP and HRR compared to Diesel fuel.