Combined Effect Of Incidence - Forebody Angles on the Flow Structure Inside Spiked Supersonic Intakes

A high static pressure at the inlet face and minimal total pressure loss at the intake entry are required for an efficient operation of the spiked supersonic jet engines. The turning (Forebody) angles are optimized for a maximum total pressure recovery at the intake entry for the design Mach number condition, so that the compression shocks fall on the cowl lip. Non zero incidence angle changes the effective deflection angle up and down the spike, so the combining effect of incidence and forebody angles is essential for the intake performance. The present analysis investigates the pressure distribution at the compressor face at different forebody-Incident combinations at different supersonic fly speeds ranging from 1.8 to 2.2 Mach. The numerical analysis is carried out under 2-D, steady and viscous flow assumptions. The external flow, which consists of the set of waves, is solved analytically. CFD analysis using Control Volume Formulation technique is applied to analyze the internal flow. In house program is built to solve the governing sets of equations by using SIMPLE algorithm. The analyses are carried out at incidence angles ranging from 0o to 10o and forebody angles ranging from 6o to 25o. The procedure has been verified by comparing with previous experimental results. The results obtained have generally shown, that the pressure recovery increases by the increasing of the wedge angle and decreases by increasing of incidence angle. In some operating conditions, the combination of the three factors, Mach no., the incidence, and the forebody angle results in a complicated mechanism due to the presence of compression and expansion waves in the external part of the intake simultaneously.

KEYWORDS: Supersonic flow, Inlets, CFD, Spike intakes, Pressure recovery.