Verification of the analytical design model of a subcritical air ejector and assessment of the behavior of the manufactured machine under different operating conditions

Abstract

Ejectors are dynamic energy machines that can be designed using analytical methodologies that have been in use for decades. These calculation methods consist of coefficients and equations, which are now untraceable and have not been updated since they were first proposed. Modern literature is devoid of ejector design; therefore, to conduct research on ejectors, it is first necessary to verify the validity of existing computational methods. In this study, we conducted computational fluid dynamics (CFD)-assisted experiments to simulate a subcritical air-to-air ejector with the possibility of controlling the distance of the nozzle mouth from the mixing chamber inlet. It was found that the optimum distance of the nozzle mouth from the mixing chamber inlet (i.e. 7.9 mm) corresponds to the design condition when the ejection coefficient is 1.673 and the secondary medium quantities reach the maximum value of 31.19 kg/h. A change in the position of the nozzle outside the optimum point leads to a deviation in the ejection coefficient and flow rate. The experimental results were compared with those from CFD analysis and the deviation between them did not exceed 2%. Two turbulent flow models, namely k-omega BSL and k-epsilon standard, were used for the comparison.