Potential of Early Direct Injection (EDI) for simultaneous NOx and soot emission reduction in a heavy duty turbocharged diesel engine

• Published in: Applied thermal engineering 2019-07, Vol.158, p.113762, Article 113762
• Main Authors: Pandey, Sunil Kumar, Vandana, Suryanarayana, Sarma Akella, S.R., Ravikrishna, R.V.
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics; Computer simulation; Diesel engines; Emissions; Emissions control; Exhaust gases; Experimentation; Fluid dynamics; Homogeneity; Ignition; Nitric oxide; Nitrogen oxides; Soot; Strategy; Superchargers
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2019.113762

•Assessment of mixture homogeneity for early direct injection in CI engine using CFD.•Evaluated strategies of timing, multiple injections, etc using uniformity index.•Simultaneous soot & NOx reduction of 20% achieved with optimized early direct injection. Early Direct Injection (EDI) in diesel engines with multiple injections has the potential to simultaneously reduce Nitrogen Oxide (NOx) and soot. The current work involved carrying out three-dimensional Computational Fluid Dynamic (CFD) simulations and engine experiments in order to evaluate EDI strategies on a heavy-duty diesel-fuelled engine operating at 25% load with the motivation to operate in Homogeneous Charge Compression Ignition (HCCI) mode. A uniformity Index (UI) parameter was defined to assess charge homogeneity. Results showed significant in-homogeneity and presence of wall-film for EDI. Simulations were conducted to assess improvement of charge homogeneity by several strategies; narrow spray included angle, injection timing, multiple injections and intake air heating. The maximum UI achieved by EDI was 0.78. Further work involved engine experimentation to assess the EDI strategy with dual injection. The first injection timing was varied from 90° to 20° Before Top Dead Center (BTDC) with cooled Exhaust Gas Recirculation (EGR) rate of 20%. The effect of EGR rate (0 to 35%) on the combustion behaviour was studied. An Optimized EDI (OptimEDI) strategy was developed which consisted of triple injections with fuel mass split ratio of 41%-45%-14% and an early first injection. This strategy gave 20% NOx and soot reduction simultaneously over the conventional Compression Ignition (CI) mode.