Residual Cooking Oil Biodiesel and Hexanol as Alternatives to Petroleum-Based Fuel in Low Temperature Combustion: Parametric Study

Environmental pollution as a result of improper disposal of agricultural and food industry waste has been a concern lately. In the present study, an attempt has been made to produce energy from these wastes. Biodiesel produced from residual cooking oil (RCOB) and hexanol produced from agricultural waste have been investigated as alternatives to petroleum-based fossil fuels in a dual-fuel low-temperature combustion engine. Hexanol was injected in the inlet port at 3 bar injection pressure whereas RCOB was injected directly inside the combustion chamber using a common rail direct injection system. The proportion of Hexanol to RCOB was varied from 40% to 60% at rated load. The operating parameters such as intake air temperature, exhaust gas recirculation (EGR) quantity along with multiple injection timing, duration, quantity, and pressure were optimized for lower oxides of nitrogen (NOx) and smoke emissions. Intake air temperature of 40 °C, EGR rate of 30 %, and direct injection timings at 47 °bTDC and 7 °bTDC exhibited the lowest nitric oxide (NO) and smoke emissions. Similarly, the injection quantity share of 50:50 for the two direct injections at an injection pressure of 400 bar was observed to be optimum for the lowest NO and smoke emissions. Accordingly, the test engine was operated at optimized conditions, and the combustion, performance, and emission data were collected and compared with that of Diesel operation. A reduction in NO emission by 97%, smoke emission by 70%, and carbon dioxide (CO2) emissions by 19% were observed. A marginal increase in the thermal efficiency of about 2% was also observed with 40% hexanol replacement. From the investigation, it is inferred that with proper optimization, renewable fuels such as RCOB and hexanol can give a diesel-like performance with reduced emissions by low-temperature combustion.