The early and late portions of transient fuel injection have proven to be a rich area of research, especially since the end of injection can create a disproportionate amount of emissions in direct injection internal combustion engines. A perennial challenge in simulating the internal flow of fuel injectors is the valve opening and closure event. In a typical adaptive-mesh CFD simulation, the small gap between the needle valve and the seat must be resolved with very small cells, resulting in extremely expensive computations. Capturing complete closure usually involves a topological change in the computational domain. In this work we present a more gradual and easily-implemented model of closure that avoids spurious water-hammer effects. The algorithm is demonstrated with a simulation of a gasoline direct injector operating under cavitating conditions. The results include the the first simulation of a multiple injection event known to the authors. The results show cavitation at low valve lift. Further, they reveal post-closure dynamics that result in dribble, which is expected to contribute to unburned hydrocarbon emissions.
- Fluids Engineering Division
Modeling Sealing in Transient Injector Simulations
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Mohapatra, C, Jacobsohn, G, Baldwin, E, & Schmidt, D. "Modeling Sealing in Transient Injector Simulations." Proceedings of the ASME 2017 Fluids Engineering Division Summer Meeting. Volume 1A, Symposia: Keynotes; Advances in Numerical Modeling for Turbomachinery Flow Optimization; Fluid Machinery; Industrial and Environmental Applications of Fluid Mechanics; Pumping Machinery. Waikoloa, Hawaii, USA. July 30–August 3, 2017. V01AT04A009. ASME. https://doi.org/10.1115/FEDSM2017-69309
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