Research Article Emissions and Performance of Diesel Engines Correlated with Biodiesel Properties

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Introduction
Te use of fuel oil in India has passed the peak of the balance between production and consumption. Te tendency of this high fuel demand is refected in the increase in the volume of motorised vehicles and the volume of fuel oil imports shown in the volume of motorised vehicles by 62% and an increase in fuel imports by 26% in 2022. Biodiesel is an alternative fuel sourced from vegetable oils or animal fats that are produced through esterifcation/transesterifcation processes [1]. B20 biodiesel is implemented as the main fuel for diesel engines. Te use of biodiesel fuel results in lower engine performance than diesel fuel despite more environmentally friendly engine emissions [2]. Te higher the palm oil content, the lower the engine torque and power. Tis is due to the low calorifc value and high viscosity of palm oil compared to those of diesel fuel [3]. Te decline in performance of biodiesel-fuelled diesel engines can be improved by adding alcohol to the fuel [4]. In addition, the addition of alcohols such as methanol, ethanol, and butanol also has a positive impact on reducing carbon monoxide (CO) and hydrocarbon (HC) emissions and fuel consumption produced by diesel engines [5]. Te low viscosity properties, high oxygen content, and high cetane number in alcohol are the main factors for lower diesel engine exhaust emissions than when using biodiesel fuel. Terefore, in line with the programme to reduce fossil fuel dependence, this study observed diesel fuel blended with palm cooking oil and methanol or ethanol or butanol alcohol additives to improve biodiesel properties [6]. A biodiesel blend consisting of diesel-palm cooking oil-alcohol, methanol, ethanol, and butanol was investigated through its physical and chemical properties. Furthermore, the tendency of biodiesel properties was correlated with diesel engine performance and exhaust emissions.

Research Methods
Palm cooking oil was obtained from a commercial shop in Chennai city. Meanwhile, methanol, ethanol, and butanol alcohols were obtained from a chemical store. In the process of making biodiesel formulation, the diesel fuel-palm cooking oil-alcohol (methanol/ethanol/butanol) were mixed according to the measurements shown in Table 1. Observations were made on the physical and chemical properties of biodiesel such as viscosity, calorifc value, fash point, and density. In the process, the biodiesel testing method was carried out, as shown in Table 2. Te physical and chemical properties of biodiesel B30, B40, B50, B60, B70, B80, and B100 were evaluated for quality properties. To fnd out the tendencies described by the physical and chemical test results, graphs were made.

Viscosity of Biodiesel.
Viscosity is used as a parameter to measure fuel quality. Te higher the viscosity of biodiesel, the more viscous the fuel and the more difcult it is to mix with air, making the fuel injection process difcult [7]. Figure 1 shows the viscosity of biodiesel with varying volumes. In general, biodiesel blended with alcohol produces higher viscosity than 30% biodiesel without alcohol (B30). Te viscosity of biodiesel with ethanol alcohol blends was higher than that of biodiesel methanol and biodiesel butanol blends. Meanwhile, the viscosity of biodiesel with methanol alcohol blends was lower than that of biodiesel ethanol and biodiesel butanol blends. Te highest viscosity was obtained in fuel with 85% palm cooking oil and 15% ethanol or B100A. Te lowest viscosity was obtained in the fuel with 30% palm cooking oil and 15% butanol or B30A. Biodiesel fuel with high viscosity properties is detrimental to the fuel injection process [8]. Te use of ethanol alcohol blends in biodiesel compared to methanol or butanol alcohol blends could produce high emissions and high fuel consumption.

Calorifc Value of Biodiesel.
Te calorifc value of fuel indicates the amount of energy produced during the combustion process [9]. Te amount is infuenced by the composition of the fuel. Figure 2 shows the trend of the decreasing calorifc value of biodiesel with alcohol blends compared to that of biodiesel without alcohol. Te higher the palm cooking oil content, the lower the calorifc value. In this case, the lowest calorifc value belongs to the fuel with 85% palm cooking oil and 15% ethanol alcohol blends (B100A). Te calorifc value of biodiesel with butanol alcohol blends appears to be higher than that of biodiesel with ethanol or methanol alcohol blends. In this case, the highest calorifc value belongs to the fuel with 30% palm cooking oil and 15% butanol alcohol blends [10]. Te lowest calorifc value belongs to the biodiesel with ethanol alcohol blends. Te use of fuel with a high calorifc value will improve engine performance. Tis is due to the large amount of calorifc energy produced so that the quality of the combustion process is better. Terefore, biodiesel with butanol alcohol blends has the potential for better combustion quality and emissions than biodiesel with methanol or ethanol alcohol blends.

Flash Point of Biodiesel.
Te fash point of a fuel is an indicator that the fuel can burn when it comes into contact with heat or fre. Te lower the fash point, the more fammable the fuel [11]. Fuel fammability afects the rate of combustion, thereby accelerating the increase in combustion chamber temperature and maximising the combustion process. Tis benefts the working power of the engine. However, an excessive increase in the combustion chamber temperature triggers the formation of NOx emissions. Figure 3 shows the fash point test results with varying    Journal of Engineering biodiesel volumes. In general, biodiesel with alcohol blends has a higher fash point than 30% biodiesel fuel without alcohol blends. Te fash point of biodiesel with methanol alcohol blends is lower than that of biodiesel with ethanol or butanol alcohol blends. Terefore, biodiesel with methanol alcohol blends has the potential to produce higher engine performance and emissions than biodiesel with ethanol or butanol alcohol blends.

Biodiesel Density.
Te density of biodiesel is very important to determine the quality of the fuel combustion process. Te higher the fuel density, the better the fuel quality, which supports the perfect combustion process [12]. Te higher the fuel density, the higher the fuel consumption. Figure 4 presents the density of the fuel with varying palm cooking oil content. Biodiesel has a higher density when it contains more palm cooking oil. Te density of biodiesel with methanol alcohol blends is lower than that of biodiesel with ethanol or butanol alcohol blends. However, the increase in the biodiesel density value is not signifcant between methanol alcohol-blended biodiesel and ethanol/ butanol alcohol-blended biodiesel density.

Conclusion
Te diesel-palm cooking oil-methanol blend biodiesel fuel has the highest fash point, lowest viscosity, high calorifc value, and low density compared to diesel-palm cooking oilethanol or butanol blends. Te diesel-palm cooking oilmethanol blend biodiesel has the potential to produce better performance and emissions than diesel-palm cooking oil-ethanol or butanol blends.

Data Availability
Te data used to support the fndings of this study are included in the article.