| Popis: |
This research aims to develop a numerical model capable of predicting the dynamic behaviour of liquid fuels in dense sprays. In the developed method, the flow’s polydisperse nature is handled using the method of classes in the Euler-Euler framework, using the Eulerian multi-fluid model. Therefore, every droplet class is represented with a dedicated phase momentum and phase continuity equation. However, all phases, i.e. all droplet classes and the continuous phase, share the same mixture pressure. This work represents an update of the previously published model [1, 2, 3], where the developed solver is further updated with evaporation functionality. To implement a functioning evaporation model, the solver required implementation of energy equations for the continuous and the droplet phases to broaden the developed solver’s functionality. The continuous and droplet phases are thermally coupled either by the evaporation model or using the Ranz-Marshall correlation (for non-evaporating functionality). To capture more details concerning droplets’ internal thermal behaviour, e.g. finite thermal conductivity and internal recirculation within the droplets, the solver utilizes a parabolic temperature profile model [4], which is coupled with the effective thermal conductivity model [5]. Furthermore, the evaporation model required a species transfer equation which was the last prerequisite for adding single component evaporation capability. For describing evaporation of moving droplets, we have selected the Abrazon and Sirignano model [6]. Figure 1 presents the temperatures extracted along a sampling line which goes through a non- evaporating spray (evaporation model is turned off), i.e. cold droplets are injected into a stationary hot gas. As the results suggest, the passing droplets are cooling down the hot gas, and the surface temperature is slightly higher than the volume- averaged droplet temperature. Furthermore, to perform preliminary tests of the implemented evaporation model, Figure 2 gives the penetration curves (both for the liquid fuel, and the fuel vapour) for a similar test case where large droplets (i.e. blobs) are injected into a stationary hot gas, and the evaporation model is turned on. |
