Withdrawal: Comparative Analysis of a Diverterless Supersonic Inlet and its Proposed Modified Geometry using Computational Fluid Dynamics

Aircraft air intake plays a vital role in overall performance of the aircraft. Purpose of intake is to provide less turbulent, smooth and subsonic flow to the engine. A good intake is characterized by maximum pressure recovery for a wide range of operating conditions. A slight improvement in pressure recovery may result in a significant gain in terms of engine thrust. Additionally, an efficient intake is also expected to supply a uniform and distortion free flow to the compressor. The amount of distortion present in the flow is characterized by the distortion index which gives a view of how much uniform is the distribution of flow at engine face plane in terms of total pressure. Low value of distortion index is an indicative of a smooth flow. Another important aspect associated with the air inlets of supersonic aircraft is the diversion of the low energy boundary layer away from the intake mouth. One special kind of such air intakes is the Diverterless Supersonic Inlet (DSI). It employs a generic bump with a forward swept cowl to divert the boundary layer away from the intake. This combination of the bump and cowl also decelerates the flow from supersonic to subsonic regime. In order to enhance the performance of a DSI installed on an in-service aircraft, it was proposed to extend the geometry of DSI in lateral direction. The present research aims to evaluate the performance of proposed modified design of DSI in comparison with existing geometry. For this purpose, numerical analysis of existing DSI is performed using commercial software. The validation of numerical model is done with its available experimental data. Having ascertained the accuracy of numerical model, the dimension of DSI is extended in lateral direction as per proposed design. Performance of existing and modified DSI is evaluated in terms of pressure recovery, distortion index and drag coefficient. Analysis is performed at four different Mach numbers and altitude of 8 Km. Comparative analysis revealed that the mass flow rate through the modified intake design is increased due to increase in the capture area of intake. Pressure recovery is also found slightly increased. On the other hand, drag coefficient as well as the distortion index at engine face plane are also found increased. The percent increase in the pressure recovery is very small in comparison to increase in drag coefficient yet this small increment in pressure recovery appears as a significant change in thrust of the engine which can be explained by the general thrust equation for gas turbine engines. The enhanced pressure recovery is achieved at the cost of increase in drag and the distortion index as revealed through the numerical analysis. In addition to the performance evaluation, the phenomenon of boundary layer diversion through existing and modified DSI is also captured effectively. This is a key feature of a DSI over other intake designs and gives a good insight about the flow field around the DSI and proximate areas. Modified intake is found effective at diverting the low energy boundary layer away from the intake mouth through its generic bump.