Application of Vortex Control to an Automotive Transcritical R744 Ejector Cycle

Expansion work recovery by two-phase ejector is known to be beneficial to vapor compression cycle performance. However, one of the biggest challenges with ejector vapor compression cycles is that the ejector cycle performance is sensitive to working condition changes which are common in automotive applications. Different working conditions require different ejector geometries to achieve maximum performance. Slightly different geometries may result in substantially different COPs under the same conditions. The ejector motive nozzle throat diameter (motive nozzle restrictiveness) is one of the key parameters that can significantly affect ejector cycle COP. This paper presents the experimental results of the application of a new two-phase nozzle restrictiveness control mechanism to an automotive transcritical R744 ejector cycle. This new control mechanism, vortex control, utilizes an adjustable vortex at the nozzle inlet to control the nozzle restrictiveness on the two-phase flow without changing the physical dimensions of the nozzle geometry. The test results show that nozzle restrictiveness can be adjusted with this new mechanism. Under common working conditions, with vortex control the ejector motive inlet pressure can be varied from 8609 kPa to 9637 kPa for constant motive inlet temperature and total motive mass flow rate.