Experimental Investigation of Twin Elliptic Orifice at Different NPR Levels

Abstract

Jet study lays the proper foundation for future aircraft ad rocket system design and development, for example, reduce jet noise in rocket, minimized nature of infrared signature in fighter airplanes, etc. Keeping these concerns, the present study is focused on the experimental investigation of twin elliptic orifice of aspect ratio two. The aluminum material is used for the twin orifice by rapid prototyping method. The total exit area of the orifice was maintained as equivalent diameter (Deq) of 7 mm. The test has been carried out at nozzle pressure ratios (NPRs) of two, three, and four by using high-speed jet facility. The proximity between the twin orifices was kept 1, 2, and 3 mm. Centerline pressure decay of jets was measured up to 20 Deq, and these results indicate that the mixing rate of jets was effective at lower nozzle pressure ratio compared to higher nozzle pressure ratio of two and three. In addition, the closest proximity of 1 mm of twin orifice enhances the faster mixing along its length of the jet field of the measured NPRs. The amplitude of pressure oscillations was high at 4 Deq than other locations. The jet mixing was started at 2 Deq and ends at 7, 8, and 9 Deq for 1, 2, and 3 mm proximity, respectively, of measured nozzle pressure ratio range. The reason of the above results depends on orifice geometry, aspect ratio, and nozzle pressure ratio of elliptic jet.