Experimental Investigation of Shape Transition Effects on Isolator Performance

Isolator is a critical component in supersonic air breathing engine and it is usually situated between the inlet and the combustor of a dual-mode ramjet/scramjet engine. In the present study, shape transition effects on isolator performance have been studied by carrying out experimental investigations on square, square to circular and square to elliptical transition ducts. The length of the isolator chosen in this study is 180 mm and the cross-sectional area of 900 mm(2) is maintained constant along the length for all the ducts. Experiments were carried out for isolator inlet Mach 2, using a contoured nozzle. Varying the pressure of the settling chamber varied the expansion level at the nozzle exit, which run the nozzle. The wall static pressure along the length of the isolator and the Pitot pressure at the exit plane of the isolator were measured for all the configurations. Shadowgraph technique was employed for visualizing the shock-train in the isolator. The square to circular transition isolator is found to be more efficient in achieving the static pressure rise across the isolator than the square and square to elliptical transition ducts.