The work performed during EJEMOD has covered the analysis of the ejectors first under static operation, and in a second stage focusing on the operating transitions (characteristic time 1 sec, aligned with system valves). On both stages, a combination of CFD and experimental studies have constituted the methodology to get a consolidated insight on the ejectors behavior.
During the static analysis, a new operational map (Figure 1) has been generated, which enabled to categorize different situations of interest (modes and transitions), while covering the physics involved (choked, un-choked and reverse flows). A very intensive static CFD simulation campaign (Figures 2 and 3) has been carried out, which has revealed interesting physics and supported the development and calibration of the 0D static model (Figure 4).
In parallel to the numerical activities, an experimental set-up has been built (Figure 5), capable of providing air at the expected conditions. The ejector prototypes (Figure 6) have also been manufactured and instrumented to gather temperature, pressure and mass flow at each port, together with a very detailed pressure profile in the mixing chamber. An extensive static test campaign has been performed, collecting data for the referred Cases for the three ejectors of the project. Using this data, a validation activity has been done comparing successfully the 0D model predictions with the experimental results.
For the second stage of the project, the focus was reoriented towards dynamic analysis of the ejectors. After a CFD transient campaign the understanding of the physics have identified the ejectors quasi-steady nature for the situations of interest at system level (1sec opening/closing valves). Different scenarios have been studied, like step or ramp-like evolution of values at the ports at different pressure levels. This fact was also verified by a specific experimental study which compared a transition scenario vs. a succession of steady tests following the same profile.
After this conclusion, the work has shifted to describe experimentally the transitions of interest; adaptation of the test bench has been done accordingly by adding fast valves and hot-wire velocity measurements (Figure 7).
From all this knowledge and data, a 0D tool has been developed, validated (Figure 8) and integrated in Dymola (Figure 9) for static and transition scenarios. A parallel action has generated a surrogate model trained with the 0D model which can be implemented as a black box with an extended robustness perimeter.
As a summary of the results, the project has generated a huge amount of scientific data and knowledge on the behavior of air-air ejectors under a wide range of situations, both from static and dynamic perspective. The final 0D model has been progressing to finally reach a transversal capacity to cover the whole operational envelope with a reasonable accuracy. As commented, the generation of the surrogate model is acting as a robustness-oriented twin.
Regarding Exploitation expectations, they are twofold. On one side, the project model and know-how is expected to consolidate the innovative implementation of the ejectors in the bleed system, opening a clear exploitation route for the Topic Manager. On the Consortium side, the three research institutions are expecting to exploit the generated tools and knowledge to other research activities related to ejectors. Some related applications have already been identified, like implementation to enhance vapor compression systems or use in heat recovery systems.
The project has been disseminating the results after finishing the first reporting period. Five contributions to International Conferences have already been carried out, and two more are expected till end of summer 2023. Two journal papers are also under progress at this final stage.
