Experimental Investigation of Injection Strategies to Improve Intelligent Charge Compression Ignition (ICCI) Combustion with Methanol and Biodiesel Direct Injection

Applications of methanol and biodiesel in internal combustion engines have raised widespread concerns, but there is still huge scope for improvement in efficiency and emissions. The brand-new combustion mode, named as Intelligent Charge Compression Ignition (ICCI) combustion, was proposed with methanol-biodiesel dual fuel direct injection. In this paper, effects of injection parameters such as two-stage split-injections, injection timings, injection pressure and intake pressure on engine combustion and emissions were investigated at IMEP = 8, 10, and 12 bar. Results show that the indicated thermal efficiency up to 53.5% and the NOx emissions approaching to EURO VI standard can be obtained in ICCI combustion mode. Compared with the single direct injection for methanol, two-stage split-injection for methanol can form more precise and adaptive stratifications of concentration and reactivity which significantly increases the Ppeak and HRRmax in the cylinder and further reduces HC and CO emissions. The advanced combustion phase and increased combustion rate were mainly attributed to the slight postponement of biodiesel injection timing. The injection of methanol at the beginning of the intake stroke is beneficial for fuel-air mixing, thereby obtaining a higher indicated thermal efficiency. What?s more, increasing intake pressure from 1.5 bar to 1.75 bar can increase the indicated thermal efficiency and reduce incomplete combustion products. It was also observed that the increase of methanol injection pressure slightly reduces CO emissions and increases the indicated thermal efficiency.