Experimental Investigation of an Aggressive S-Shaped Intermediate Compressor Duct

Abstract

Abstract Reducing the fuel consumption of airplanes is one of the main research topics of the aero industry. Due to this, the bypass ratio in modern aero engines is increasing and the radial offset between the low pressure compressor (LPC) and the high pressure compressor (HPC) is getting larger. Motivated by shortening the length of the duct between the LPC and HPC, called the intermediate compressor duct (ICD), a workgroup from DLR Institute of Propulsion Technology, MTU Aero Engines AG and GKN Aerospace set up a measurement series in the new DLR ring cascade wind tunnel, that simulates a shorter and therefore aero-dynamically more aggressive s-shaped ICD. The setup consists of a full annulus channel. It provides 60 swirler blades which simulate the last rotor of the LPC, 120 LPC outlet guide vanes (OGV), 10 struts and 30 HPC inlet guide vanes (IGV). The airfoil counts are generic counts proposed for validation. Behind the OGV, there is a bleed air outlet which can be varied between 3% and 35% of the mass flow. This paper describes the highly instrumented test rig and its measurement techniques. We are able to analyze the specific flow behavior as well as determine the main ICD-performance parameter. Seven different measurement planes are located between the mentioned blade rows. The total state and the velocity (absolute value and directions) are among others measured in the plane. For each task and measurement location the best suited measurement method is selected. These are mainly multi hole probes in the main measurements planes, L2F in narrow places. The tests are conducted at eight different operating points, varying in Mach number, Reynolds number, bleed rate, stagger angle of swirler and HPC IGV. The high number of measurements leads to a profound understanding of the behavior of the ICD. The resulting conclusion is that in spite of the reduced axial length the flow through the aggressive s-shape of the ICD no separation occurs and therefore the desired performance is achieved.