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This study aims to reveal the performance and exhaust emissions of a spark ignition (SI) engine fueled by a gasoline-bioethanol mixture. The main performance characteristics of the SI engine tested are torque, power output; thermal efficiency, brake specific fuel consumption, and brake mean effective pressure. Meanwhile, the exhaust emissions seen are carbon monoxide and hydrocarbons. The test is carried out by comparing the performance of the SI engine under standard conditions without modification with gasoline fuel, with the SI engine with modification with 85% bioethanol fuel. The mass flow of fuel is regulated by modifying the carburetor choke at 3/4 and 7/8. The results show that although slightly lower than gasoline, in general, it can be seen that bioethanol can improve SI engine performance and produce environmentally friendly exhaust emissions.

This study examines the Ignition characteristics of blended fuel droplets with crude coconut oil and rhodium liquid as a liquid metal catalyst. The ignition behavior was observed by igniting the oil droplet on a junction of a thermocouple, and the droplet evolution recorded with the high-speed camera. The results show that the addition of a liquid metal catalyst successfully reduces the molecular mass of the triglyceride and weakens the bonding force between the carbon chain, and therefore the viscosity and flash point decreases. Moreover, the addition of liquid metal catalysts increased the reactivity of fuel molecules such as C-H, C-C, C = C, and C-O. Changes in the physical properties of the fuel, the geometry of the carbon chain, and molecular mass ease the absorption of heat by the fuel droplet, thereby increasing fuel ignition performances.

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For now, energy sources uses are still dominated by fossil fuels, whose availability is limited and continues to decline. Therefore, new alternative energy is needed to reduce dependence on fossil fuels. Crude vegetable oil is one alternative energy source that can be utilized as a substitute for fossil fuels because vegetable oil has a composition almost similar to fossil fuel. Crude coconut oil is an alternative to biodiesel to reduce dependency on fossil fuels. The combustion reaction of crude coconut oil is tricky because it has bonds saturated chain, so a substance is needed to weaken the carbon chain to increase the burning rate. The burning rate of coconut oil droplets has been investigated experimentally by adding clove oil and eucalyptus oil bio-additives. Tests were carried out with single droplets suspended on a thermocouple at atmospheric pressure and room temperature and ignited with a hot wire. The addition of clove oil and eucalyptus oil as bio-additives in crude coconut oil was 100 ppm and 300 ppm, respectively. The suspended droplet combustion method was chosen to increase the contact area between the air and fuel so that the reactivity of the fuel molecules increases. The results showed that the eugenol compounds in clove oil and cineol compounds in eucalyptus oil were both aromatic and had an unsymmetrical carbon chain geometry structure. Therefore, this factor has the potential to accelerate the occurrence of effective collisions between fuel molecules; thus, the fuel is flammable, as evidenced by the increased burning rate. Moreover, from the observations, it was found that the highest burning rate was achieved in both bio-additives with a concentration of 300 ppm

A comparative study on the combustion characteristics of a single droplet fueled by DEX, crude jatropha oil (CJO), and a mixture of CJO with a magnetic liquid catalyst of rhodium trisulfate has been carried out under normal gravity conditions. The high viscosity of crude jatropha oil makes it difficult to burn under normal conditions (room temperature and atmospheric pressure), therefore the addition of a magnetic liquid catalyst rhodium trisulfate is needed to improve the properties of crude jatropha oil. As a catalyst, rhodium trisulfate has the potential to improve combustion performance while improving the physical properties of crude jatropha oil as an alternative fuel for the better. Furthermore, performance tests were also carried out with DEX fuel with a cetane number (CNs) 53. The results showed that compared to DEX, it was seen that the liquid metal catalyst rhodium trisulfate succeeded in making crude jatropha oil more charged so that the combustion process was better. This is evidenced by a significant change in the dimensions of the flame and an increase in the combustion temperature. Moreover, it is also seen that the burning rate increases and the ignition delay become faster.

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