Proc. of the 3 rd International Conference on Advances in Mechanical Engineering, January 4-6;2010 S.V. National Institute of Technology, Surat – 395 007, Gujarat, India Numerical simulation of internal flowfield and performance evaluation of a 3D mixed inline intake with fence Jaware VB 1* , Amarjit Singh 2 , Roschelle R Martis 2 Joshi SV 3 1 D.Y. Patil College of Engineering, Pune – 411 044, Maharashtra, India 2 Defence Institute of Advanced Technology (DU), Pune – 411 025, Maharashtra, India 3 Vishwkarma Institute of Technology, Pune - 411 037, Maharashtra, India * Corresponding author (e-mail: jaware_vasant@rediffmail.com) Intake is an important component of a high speed air breathing engine. To study the influence of viscous effects on the performance and especially the internal flowfield of a scramjet intake, an inviscid flow and a viscous turbulent flow computational study has been carried out on a fixed geometry hypersonic mixed inline intake with fence. The computations have been performed using a commercially available CFD package. To help the analysis of complex 3D flow, computations have been done for 2D scramjet intake also. The study has been carried out for a freestream Mach number of 6.5, a unit Reynolds number 1.6x 10 6 per meter and at 0 0 and 6 0 angle of attack with an inlet contraction ratio of 2.88. The nature of the flow field existing inside the intake has been investigated in terms of pressure, density, velocity and Mach number contours at different axial and lateral locations. The performance analysis of the mixed inline intake with fence configuration is evaluated in terms of air capture ratio, mass flow rate and total pressure recovery. It was found that mass flow rate and total pressure recovery increases and air capture ratio decreases with increase in angle of attack for 3-D computations. The computational results of hypersonic intake with and without fence are compared with results obtained from oblique shock wave theory. 1. Introduction The performance of a scramjet powered hypersonic air breathing vehicle is evaluated by the efficiency of its intake. The aerodynamic design of hypersonic intake is a critical issue for the overall performance of an air breathing propulsion system and subject of recent investigations [1-4]. The primary purpose of inlet is to provide homogeneous high pressure flow to the engine with a minimum of aerodynamic losses. Compression is performed through a series of oblique shocks inside the inlet. Based on the plane in which compression takes place, two types of inlet designs are possible - one where the inlet compression occurs in the same plane as the forebody compression, and the other where inlet compression takes place in a plane perpendicular to the forebody compression. The former type of inlet is called inline compression intake and the later is termed as sidewall compression intake. The external compression of the flow before entering an intake essentially takes place in vertical plane through the forebody bow shock and one or two ramp shocks. In an inline compression intake, further compression is affected by horizontal compression surfaces, namely the intake lower and upper surfaces. The compression will therefore be again in the vertical plane. The boundary layer on the intake upper wall at the intake-entrance can be quite thick with respect to the intake height. Any further turning of the flow in the vertical direction will therefore greatly increase the probability of large-scale separation regions at the entrance of the intake due to shock-boundary layer interactions. On the other hand, a sidewall compression intake consists of vertical wedge-shaped surfaces, and compression occurs in horizontal planes, reducing the total in-plane turning the flow must encounter to obtain the desired compression. The thick boundary layer entering the ‘sidewall compression intake’ is therefore, less likely to separate because of shock–boundary layer interaction. However the thick boundary layer on the intake upper surface will be more likely to separate due to glancing shock interaction in case of sidewall compression. Most of the open literature available is about the sidewall compression inlet [5-7]. Considering the above pros and cons and lack of published work, a study of inline intake with a fence having 28° swept back leading edges has been taken and reported here.