Numerical study on the impact of needle and dryness fraction on two-phase ejector performance under fixed/varied operating pressure

This study investigates the effects of varying needle block degree (blockage area ratio of the primary nozzle throat) and dryness fraction (the ratio of gas mass to mass of two-phase mixture) within the primary and secondary flow on the performance of a two-phase ejector, employing CFD numerical simulations under both fixed and varied conditions. The findings reveal the following: (1) Dryness fraction has a significant impact on the performance of the ejector. ER decreases with the decrease of X 1 and increases with the decrease of X 2 , when X 1 = 1 and X 2 = 0.4, the ejector performance can be improved by 253.3 % under the optimal area ratio; (2) A higher primary flow dryness fraction and a lower secondary flow dryness fraction are more favorable for enhancing the ejector's performance; (3) When P 1 changes, the ejector is most sensitive to changes in P 1 , slightly less sensitive to changes in A n , and least sensitive to changes in dryness fraction; When P 2 changes, the ejector is most sensitive to changes in dryness fraction, slightly less sensitive to changes in P 2 , and least sensitive to changes in A n ; (4) When varying P 1 and P 2 , the ejector performance is optimal at X 1 = 1 and X 2 = 0.8 (A n ); (5) Regardless of changes in AR or operating conditions, the adjustable ejector with the needle can effectively enhance the ejector's performance under certain conditions.