Transient analysis of the trans-critical CO2 adjustable ejector

In the adjustable CO2 ejector refrigeration system, the needle of the ejector as the component for regulation has a great impact on the performance of the refrigeration system. This paper investigates the changes in the entrainment ratio resulting from the adjustment of the needle position when two different needles are used. The results show that the Transient and steady state changes in the entrainment ratio are the same when a round needle is used, while the tip needle has a large change. At the same time, the round needle has a larger entrainment ratio relative to the tip needle when the throat area is reduced by the same percentage. The use of a round needle improves performance and stability during transient changes. For the round needle, with the increase of throat area reduction, the pressure change in the mixing section is reduced, and the surge in the mixing section is also reduced to a certain extent.