Computational Investigation of the Double-Injection Strategy on Ethanol Partially Premixed Compression Ignition

Ethanol partially premixed compression ignition was computationally investigated to understand the effect of the injection strategy on efficiency, emissions, and noise for a heavy-duty engine having displacement of 2123 cm3 and a compression ratio of 17.3 at medium load. Computational fluid dynamics (CFD) modeling with detailed chemistry was performed using the CONVERGE CFD package for a single sector from the intake valve closure to the exhaust valve opening. A double-injection strategy was used, and the start of first injection (SOFI), start of second injection (SOSI) and percentage of mass injected in the first injection (MIFI) were varied while keeping all other parameters constant. Results show that the variation in SOFI has a non-monotonic effect on the combustion phasing and the peak pressure rise rate (PPRR), whereas SOSI can be used to control the combustion phasing. In addition, variation in MIFI is an effective way to control combustion phasing and the peak rate of pressure rise. By an optimum choice of SOFI, SOSI, and MIFI, it is possible to attain high efficiency and low PPRR and emissions. The role of the delayed combustion in the cooler squish zone in moderating the heat release rate is also highlighted.