Quasi-1D Analysis of n-Dodecane Split Injection Process 2022-01-0506

Split injection processes have been analyzed by means of a Quasi-1D spray model that has been recently coupled to a laminar tabulated unsteady-flamelet progress-variable (UFPV) combustion model. The modelling approach can predict ignition delay and lift-off for long injection profiles, and it is now extended to a two-pulse injection scheme. In spite of the simplicity of the approach, relevant phenomena are adequately reproduced. In particular, the faster penetration of the second injection pulse compared to the first one is captured by the model both under inert and reacting conditions. The second pulse ignites much faster than the first one due to the injection into the remnants of the first one, where high temperature oxygen-depleted regions can be found. Ignition of the second pulse happens as soon as the first pulse reaches this region, with a faster low- to high-temperature transition.

Parametric variations show a different influence of pulse dwell compared to first pulse duration. For the investigated conditions, shorter dwell results in more interaction between the second pulse and the remnants of the first one, and hence faster penetration, ignition and combustion development. On the other hand, the relatively long first injection pulse creates a quasi-steady region extending from the nozzle until almost the tip that is the same irrespective of first injection duration. Flow and mixing in this region also develop in an identical way during the dwell period. Therefore, the second pulse penetration, mixing and combustion develops independently of first pulse duration.