Parametric study on effects of methanol injection timing and methanol substitution percentage on combustion and emissions of methanol/diesel dual-fuel direct injection engine at full load

The effects of methanol injection timing (MIT) and methanol substitution percentage (MSP) on the combustion and emissions of a methanol/diesel dual-fuel direct injection engine were investigated, followed by a comparative analysis with the conventional methanol/diesel dual-fuel mode. A single-cylinder, air-cooled, naturally aspirated common rail diesel engine was modified into a dual-fuel direct injection engine with a methanol direct injection system. The engine was operated at a maximum torque speed of 2500 rpm and a mean effective pressure of 0.75 MPa. The engine performance was analyzed for different methanol/diesel fuel mixtures using four MSPs: 10%, 20%, 30%, and 40%. Meanwhile, the MIT was adjusted from −60 to −300 °CA after top dead center (ATDC). The results indicated that methanol addition and retarded MIT allowed the diesel injection timing to be properly advanced. A higher MSP increased the ignition delay (CA0-10) and decreased the combustion duration (CA10-90), leading to increases in the brake thermal efficiency (BTE), coefficient of variation of the indicated mean effective pressure (IMEP) (COV_IMEP), and knock intensity (KI), along with increases in the total hydrocarbon (THC) and nitrogen oxide (NO_X) emissions and decreases in the carbon monoxide (CO) and soot emissions. Additionally, for a specific MSP, the retarded MIT increased the peak cylinder pressure and decreased the maximum heat release rate. Concurrently, it decreased the CA0-10 and increased the CA10-90. Moreover, increases in the BTE, COV_IMEP, and KI; decreases in the THC and CO emissions; and increases in the NO_X and soot emissions were achieved using the retarded MIT.