Flow visualisation in real-size optical injectors of conventional, additised, and renewable gasoline blends. (15th January 2022)

• Record Type: Journal Article
• Authors: Heidari-Koochi, Milad; Karathanassis, Ioannis K.; Koukouvinis, Phoevos; Hwang, Joonsik; Pickett, Lyle M.; Spivey, David; Gavaises, Manolis
• Is Part Of: Energy conversion and management. Volume 252(2022)
• Publication Date: 2022-01-15
• Subjects: GDI engine -- Diffuse Backlight Illumination -- High-speed imaging -- Viscoelastic flow -- Gasoline/ethanol blend; Direct energy conversion -- Periodicals; Energy storage -- Periodicals; Energy transfer -- Periodicals; Énergie -- Conversion directe -- Périodiques; Direct energy conversion; Periodicals; 621.3105
• DOI: 10.1016/j.enconman.2021.115109
• Languages: English
• ISSNs: 0196-8904

Abstract

Highlights: High-speed visualisation of cavitating and spray flow in optical injectors. Comparative assessment of conventional, renewable and alternative gasoline fuels. Two-phase flow topology dependent on thermodynamic properties and rheology. Viscoelasticity reduces in-nozzle cavitation and enhances spray atomisation. Overall behaviour of additised fuel approaches that of gasoline/ethanol blend. Abstract: Research on renewable and alternative fuels is crucial for improving the energy and environmental efficiency of modern gasoline internal combustion engines. To highlight the influence of fuel rheological and thermodynamic properties on phase change and atomisation processes, three types of gasoline blends were tested. More specifically, the campaign comprised a reference gasoline, an ethanol/gasoline blend (10% v/v) representative of renewable fuels, and an additised gasoline sample treated with viscoelasticity-inducing agents. High-speed imaging of the transient two-phase flow field arising in the internal geometry and the near-nozzle spray region of gasoline injectors was performed employing Diffuse Backlight Illumination. The metallic body of a commercial injector was modified to fit transparent tips realising two nozzle layouts, namely a two-hole real size model resembling the Engine Combustion Network spray G injector and an enraged replica with an offset hole. Experiments were conducted at realistic operating conditions comprising an injection pressure of 100 bar and ambient pressures in the range of 0.1–6.0 bar to cover the entire range of chamber pressures prevailing in Gasoline Direct Injection engines. The action of viscoelastic additives was verified to have a suppressive effect on in-nozzle cavitation (6% reduction in cavitation extent), while also enhancing spray atomisation at flash-boing conditions, in a manner resembling the more volatile gasoline/ethanol blends. Finally, persisting liquid ligaments were found to form after the end of injection for the additised sample, owing to the surfactant nature of the additives.