Assessing the impact of injector included angle and piston geometry on thermally stratified compression ignition with wet ethanol

• Published in: Applied energy Vol. 262; p. 114528
• Main Authors: Gainey, Brian, Gohn, James, Hariharan, Deivanayagam, Rahimi-Boldaji, Mozhgan, Lawler, Benjamin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.03.2020
• Subjects: Injector spray angle; Low temperature combustion; Piston geometry; TSCI; Wet ethanol; Wet ethanol; CFD; HCCI; TSCI; PPC; CDC; IVO; O2; DI; NVO; CO2; MPRR; WE; IMEPg; deg aTDC; PFI; NOx; SI; CAx; PFS; Low temperature combustion; Injector spray angle; EI; CAD; Piston geometry; CO; GCI; ηig,th; SOI; EGR; RCCI; uHC; EVC; IVC; LTC; PM; EVO; ηcomb
• DOI: 10.1016/j.apenergy.2020.114528
• ISSN: 0306-2619

•The efficacy of TSCI is very sensitive to injector spray angle and piston geometry.•A large injector included angle increases TSCI’s efficacy.•A small injector included angle does not increase thermal stratification.•A re-entrant bowl piston creates more thermal stratification than a wide bowl.•Ideal hardware for TSCI is wide injector included angle with re-entrant bowl piston. Recent results have concluded that the efficacy of compression stroke injections in enhancing natural thermal stratification are dependent on the injector’s included angle. Therefore, there is a need to further understand how different hardware affects the efficacy of thermally stratified compression ignition. In this study, three injector included angles are considered: 150°, 118°, and 60°. Compression stroke injection timing sweeps are performed with these three injectors using two distinct piston geometries: a re-entrant bowl piston geometry found in a production, light-duty diesel engine, and a custom-made open, shallow bowl piston geometry, designed to reduce surface-to-volume ratio. Using an equivalence ratio of 0.5 and a split fraction of 80%, it was found that, with the re-entrant bowl piston geometry, the 150° injector displayed high controllability over the burn duration and was able to elongate the burn duration by a factor of 1.8×. The 118° injector displayed slight controllability over the burn duration, while the 60° injector displayed no controllability. With the open bowl piston geometry, the 150° maintained high controllability over the burn duration, albeit with less efficacy. The 60° injector still had no controllability and now the 118° injector had no controllability. The low surface-to-volume ratio of the shallow bowl piston led to less natural thermal stratification than the re-entrant bowl piston geometry, which impacted the compression stroke injection’s ability to control the burn rate. Therefore, the hardware setup that achieves the highest efficacy is a re-entrant bowl-like piston geometry with a wide spray angle injector.