Browsing by Author "Kozak, Jeffrey D."
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- 3-D flow calculations of a bifurcated 2D supersonic engine inlet at takeoffKozak, Jeffrey D. (Virginia Tech, 1995-08-05)An internal, 3-D, viscous numerical flow simulation was performed on the rectangular-to-circular transition, bifurcated, 2D high speed civil transport engine inlet at takeoff. The objective of the study was to obtain the causes of flow distortion at the inlet fan face. The inlet was modeled with the centerbody in the fully collapsed takeoff position. A single block, 14Ox40x40 Polar grid topology of a 1/4 symmetry volume of the inlet was used in the simulation. The calculation employed the well established, robust PARC3D CFD code, which uses the full three-dimensional, Reynolds averaged, Navier-Stokes equations in strong conservation form. The flow was considered to be turbulent over the entire flow region. The turbulence model incorporated into PARC3D is the algebraic Baldwin Lomax model. Limitations existed in the local region where the flow interacts with the nose cone due to the inherent limitations of the turbulence model. The results showed that the flow throughout the inlet was well behaved. The turbulent boundary layers were thin and stayed attached to the surfaces of the inlet throughout the entire flowfield. A high pressure recovery was observed at the fan face. Radial distortion at the fan face was caused by thin boundary layers on the nose cone and cowl surfaces. Circumferential distortion was caused by pressure gradients produced by the wake of the splitter plate, located just upstream of the fan.
- Investigation of Inlet Guide Vane Wakes in a F109 Turbofan Engine with and without Flow ControlKozak, Jeffrey D. (Virginia Tech, 2000-08-17)A series of experiments were conducted in a F109 turbofan engine to investigate the unsteady wake profiles of an Inlet Guide Vane (IGV) at a typical spacing to the downstream fan at subsonic and transonic relative blade velocities. The sharp trailing-edge vanes were designed to produce a wake profile consistent with modern IGV. Time averaged baseline measurements were first performed with the IGV located upstream of the aerodynamic influence of the fan. Unsteady experiments were performed with an IGV-fan spacing of 0.43 fan chords. High-frequency on-vane pressure measurements showed strong peak-to-peak amplitudes at the blade passing frequency (BPF) of 4.7 psi at the transonic fan speeds. High-frequency total pressure measurements of the IGV wake were taken between the IGV and fan. Results showed that the total pressure loss coefficient of the time averaged IGV wake is reduced by 30% for the subsonic fan, and increased by a factor of 2 for the transonic fan compared to the baseline. Time resolved wake profiles for subsonic fan speeds show constructive and destructive interactions over each blade pass generated by the fan potential flow field. Time resolved wake profiles for the transonic fan speeds show that shock interactions with the IGV surface result in the wake shedding off of the vane at the BPF. Furthermore, the effectiveness of trailing edge blowing (TEB) flow control was investigated. TEB is the method of injecting air aft of the IGV to reduce the low pressure regions (deficits) in the viscous wakes shed by the vanes. Minimizing the IGV wakes reduces the forcing function on the downstream fan blades, thereby reducing high cycle fatigue. The TE span of the vane contains discrete holes at the axial centerline for TEB. Baseline results showed that TEB eliminates the IGV wake, while using only 0.03% of the total engine mass flow per IGV. TEB for the subsonic fan at the close spacing shows complete wake filling using the same mass flow as the baseline. TEB for the transonic fan shows a reduction of 68% in the total pressure loss coefficient, while requiring 2.5 times the mass flow as the baseline.