Experimental Studies for Visualization of Flow with Boundary Layers in an Axial Compressor Fan Inlet using Pressure Probes

Abstract

Flow at inlet of fan in an axial compressor must be one dimensional as developed flow so that angular momentum fed by the fan to incoming air is maximum. It is possible with good inlet design and optimum inlet length where we obtain stream line flow into fan with nominal boundary layer thickness. Distortion to the flow at fan inlet in an axial compressor is unavoidable problem. For example in aircraft gas turbine engine; flow at inlet of fan is distorted due to maneuvering of air craft, strong cross winds and atmospherics turbulence at inlet of compressor. Flow at inlet of fan affects boundary layer and hence the performance of compressor. Therefore, visualization of flow with boundary layers in an axial ducted fan setup is carried out for well-defined inlet conditions using pressure probes. To visualize the flow with boundary layer development at the fan inlet, static and stagnation pressure are measured throughout the inlet passage of duct using static and pitot probe and velocity is calculated across the given reference planes of duct using Bernoulli’s equation. Using these data, profile plots are drawn and mathematical models are developed and flow with boundary layer is analyzed. Under normal inlet flow condition flow in the duct inlet is axisymmetric, steady, turbulent and incompressible. Boundary layer develops consistently towards the fan inlet and it is nominal.