Theoretical investigation of variable area ejectors

A theoretical analysis of a variable area ejector is presented. The flow-field is solved using a steady quasi-one-dimensional, inviscid control volume formulation for cases of both complete and incomplete mixing while combustion effects are included with an equilibrium calculation. An assumed three parameter analytical wall pressure distribution is used in all cases. Under fully mixed-conditions, the model estimated compression ratios that were 40% higher than the computational values due to neglecting turbulence and viscosity. This cause was later confirmed with a partially mixed calculation which also predicted a mixing length of 9 diameters. Under SMIC conditions, improved compression was achieved at an equivalence ratio of 2.5, while a decrease in performance occurred at Stoichiometric conditions. The oxidation of carbon monoxide occurred for the entire equivalence ratio range and was responsible for the majority of the heat release in the ejector. Thrust augmentation was found to increase with area constriction up to a limit, with the Stoichiometric case yielding values as high as 12%.