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

摘要

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 degrees 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 (CAO-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) (COVIMEP), and knock intensity (KI), along with increases in the total hydrocarbon (THC) and nitrogen oxide (NOx) 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 CAO-10 and increased the CA10-90. Moreover, increases in the BTE, COVIMEP, and KI; decreases in the THC and CO emissions; and increases in the NOx and soot emissions were achieved using the retarded MIT.