Experimental studies on supersonic mixer-ejector using radially lobed nozzles

Abstract

IntroductionDue to a variety of advantages like thrust augmentation, reduction of jet noise and plume radiation, ejectors are used in numerous aerospace applications. Considerable research effort has been made, of late, towards attaining the best possible ejector configuration. A mixer ejector which replaces the conventional circular ejectors and the associated long mixing ducts is considered a viable solution to a good ejector even in supersonic speeds. Details of work based on a mixer ejector are available in recent literature. [Tillman et al. (1991, 199z), Presz et al. (1986)]. Primary nozzles in these studies were two dimensional lobed (symmetric/unsymmetric) ones. Basically the mixer ejector concept centres around the generation of an array of large scale low intensity streamwise vortices into the mixing duct. These vortices enhance the mixing process by an inviscid stirring process [Werle et al. (1987)] and give rise to better ejector performance and shorter mixer lengths. What has been conclusively proved in previous works [Presz et al. 0986)] is that in mixer-ejector configuration, effectiveness of mixing depends strongly on lobe shape of the primary nozzle. In the recent past, Narayanan (2993) developed a radially lobed supersonic nozzle (petal nozzle) for the primary flow and tested it in the ejector mode. It has been found that petal nozzle gives very good pumping characteristics over conical nozzles and also over 2-D lobed nozzles. The present work aims at further investigations on the aspect of ejector performance of four different petal nozzles of different configurations. 2 Details of experimentsThe schematic of experimental setup used for this study is given in Fig. la. The primary line consists of settling chamber, contraction and the petal nozzle. To the settling chamber of secondary flow, which is annular and coaxial with the primary