Experimental investigation of an efficient and lightweight designed counter-rotating shrouded fan stage

Authors

Timea Lengyel-Kampmann - German Aerospace Center, Institute of Propulsion Technology, Cologne
Jirair Karboujian - German Aerospace Center, Institute of Propulsion Technology, Cologne
Peter Winkelmann - German Aerospace Center, Institute of Structures and Design, Stuttgart
Guillaume Charroin - German Aerospace Center, Institute of Propulsion Technology, Cologne

Abstract

One of the main targets of the engine research is the reduction of the fuel assumption to make the air traffic more environmentally friendly. Therefore, the counter-rotating fan and propeller concepts awakaned the interest of the aircraft engine industry due to the opportunity to achieve higher efficiency. Several international projects were dealing with these concepts, in which the DLR was participating as well. Based on this know-how the German Aerospace Center has decided to design an own counter-rotating shrouded fan stage (CRISP), which was designed and aero-mechanically optimized in the frame of the project CRISP2. The main design goal was to maximize the aerodynamic efficiency under restricted static and dynamic mechanical properties of the blade applying lightweight CFRP material and new innovative manufacturing technology. Otherwise the acoustic properties should be improved simultaneously. The idea was to reuse the original CRISP-1m test rig designed by the MTU Aero Engines in the 80th and tested at the DLR in 1995 on the M2VP test bed. The blade geometry, the blade material and manufacturing technology should be redesigned and improved. During the design phase an automated multi-objective, multidisciplinary optimization method was applied which allows using simultaneously both a CFD process chain to determine the aerodynamical properties of the fan geometry and also a FE process chain to analyze the structural behavior of the blades and the disc. This FE calculation method of the composite blades is a significant result of the project, which should be validated by the test results. So the measurement of the mechanical properties of the blades plays a very important role during the rig tests. In general, the targets of the experimental investigation are to validate the optimization results, the FE calculational method and the acoustic properties predicted by the DLR in-house code PropNoise. In the first phase of the experimental work the rig instrumentation was planned. Several review processes were carried out to check if all targets and requirements are fulfilled. The instrumentation enables the measurement of the fan aerodynamic by different rakes, acoustic measurement by microphones, hot wire measurement, optical measurement (PIV and Image Pattern Correlation Technic (IPCT)) and Kulite measurement. Different measurement methods are applied to allow vibration analysis for the condition monitoring of the rig. Several strain gages are implemented on the rotor blade surfaces to monitor the dynamic strain amplitudes and blade frequencies during the test. One of them is suitable for the measurement of the static strain values as well to provide measurement data for the validation. Two telemetry systems were planned to transfer the rotating signals from both rotors into the stationary system. The whole instrumentation will be discussed in the paper in detail. Additionally, inlet distortion measurements were carried out on the CRISPmulti fan rig simulated the total pressure drop due to boundary layer ingestion (BLI). The design of the inlet distortion device was presented in the ISABE conference in 2022. The test program was started in October 2021 with the commissioning phase and the measurement was finished in June 2022.