Flow-Field Analysis of Isobaric Combustion Using Multiple Injectors in an Optical Accessible Diesel Engine



15th International Conference on Engines & Vehicles
Authors Abstract
Isobaric combustion has shown the potential of improving engine efficiency by lowering the heat transfer losses. Previous studies have achieved isobaric combustion through multiple injections from a single central injector, controlling injection timing and duration of the injection. In this study, we employed three injectors, i.e. one centrally mounted (C) on the cylinder head and two side-injectors (S), slant-mounted on cylinder head protruding their nozzle tip near piston-bowl to achieve the isobaric combustion. This study visualized the flame development of isobaric combustion, linking flow-field details to the observed trends in engine efficiency and soot emissions. The experiments were conducted in an optically accessible single-cylinder heavy-duty diesel engine using n-heptane as fuel. Isobaric combustion, with a 50 bar peak pressure, was achieved with three different injection strategies, i.e. (C+S), (S+C), and (S+S). Bottom-view high-speed soot luminosity images were recorded at a frame rate of 20 kHz for all cases, together with pressure traces. Flame image velocimetry (FIV) analysis was performed on the high-speed soot luminosity images to obtain a qualitative description of the flow-field obtained for the three injection strategies. Distinctive vortex structures were evident from the FIV analysis and that can be attributed to strong flame-wall and flame-flame interactions. For the C+S and S+S injection strategies, the distinct large vortex structures were found near the bowl-wall while for the S+C case, vortex structures are less prominent. The large vortex structures close to the cylinder walls contribute to lower gross indicated efficiency and higher soot level intensity of the C+S and S+S cases, compared to the S+C configuration.
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Panthi, N., Goyal, H., Ben Houidi, M., AlRamadan, A. et al., "Flow-Field Analysis of Isobaric Combustion Using Multiple Injectors in an Optical Accessible Diesel Engine," SAE Technical Paper 2021-24-0042, 2021, https://doi.org/10.4271/2021-24-0042.
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Sep 5, 2021
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Technical Paper