The present computational study for underexpanded 2D and axisymmetric nozzle configuration is carried out for both gas-only and aerated liquid jet. The study is motivated by the application of fuel injection in air-breathing propulsion systems, e.g. scramjet engines, ramjet engines and afterburners. The simulation of gas-only jet carried out using Ansys-Fluent student version. The results show that air reaches sonic condition at the injector exit due to the Fanno flow effect in the injector passage. The aerated liquid jet flow from the injector is alternately expanded by Prandtl-Meyer expansion fan and compressed by oblique shock waves due to the difference between the back (chamber) pressure and the flow pressure. The process then repeats itself and shock (Mach) diamonds are formed downstream of the injector exit similar to those typical of exhaust plumes of propulsion system. The numerical results of gas-only jet for 2D and axisymmetric configuration are validated with theory of gas dynamics and experimental results. The numerical results of gas-only jet are in good agreement with theory and experiment. Similar to gas-only jet, simulation of aerated liquid jet is carried out for both 2D and axisymmetric nozzle configuration. The simulation of aerated liquid jet is conducted using VOF model and SST k-? turbulence model. The test conditions included: jet exit diameter of 1 mm and Gas to Liquid Ratio as 4%. The simulated result of 2D aerated liquid jet is compared with 2D gas-only jet using the contours of Mach number and static pressure. The flow field of axisymmetric aerated liquid jet differs from the 2D aerated liquid jet field; this can be explained based on the nozzle configuration. The present results also compare the cone angle expansion of aerated liquid jet. The cone angle expansion of aerated liquid jet is agreed with Prandtl-Meyer expansion analysis for 2D configuration and method of characteristics for axisymmetric configuration. The computed cone angle is always smaller than the theory, and this is probably due to inertia of the liquid jet. Present investigation shows that, the experimental results for aerated liquid jet expansion angle can be explained with the method of characteristics rather than the 2D Prandtl-Meyer expansion analysis.Mechanical & Aerospace Engineerin
