Design and Experimental Verification of Mistuning of a Supersonic Turbine Blisk

Abstract

A rotor blisk of a supersonic space turbine has previously been designed to allow for free flutter to occur in an air test rig (Groth Mårtensson, and Edin, 2010, “Experimental and Computational Fluid Dynamics Based Determination of Flutter Limits in Supersonic Space Turbines,” 132(1), p. 011010). Flutter occurred at several operating conditions, and the flutter boundary for the test turbine was established. In this paper the rotor blisk is redesigned in order to inhibit flutter. The design strategy chosen is to introduce a mistuning concept. Based on aeroelastic analyses using a reduced order model a criterion for the required level of mistuning is established in order to stabilize the lower system modes. Proposals in literature suggest and analyze mistuning by varying blade mode frequencies in random patterns or by modifying blades in an odd-even pattern. Here a modification of sectors of the blisk is introduced in order to bring a sufficient split of the system mode frequencies. To verify that the redesigned blisk efficiently could inhibit flutter, an experiment similar to that in the work of Groth et al. is performed with the mistuned rotor blisk. By running the redesigned blisk at operating conditions deep into the unstable region of the tuned blisk, it is demonstrated that a relative low level of mistuning is sufficient to eliminate rotor flutter.

Mach number influence on low-pressure turbine flutter

“…Though many compressor and turbine forced response tests in a controlled environment can be found in the literature, dedicated flutter experiments are scarce because of the difficulty in predicting the final vibration amplitude of the test or its control. Groth et al (2009) triggered flutter intentionally in a 1.5-stage supersonic turbine blisk and successfully matched the results with CFD predictions. Miura and Sakai (2019) could measure flutter in a rotating labyrinth seal in a dedicated test.…”

Aeroelastic Analysis of a Transonic Fan Blade with Low Hub-to-Tip Ratio including Mistuning Effects

“…Aeroelastic problems in turbomachinery continue to attract the attention of industrial and academic researchers [1]- [5]. Classic aeroelastic phenomena include forced response and flutter.…”

“…A topic of particular interest to this investigation is the effect of random mistuning. The introduction of intentional mistuning has been proven to be an effective and practical way to alleviate flutter [18]- [20]. This paper has described the outcomes of the performed mistuned aeroelastic stability with a Monte Carlo simulation of random mistuning presented at the last.…”

Aeroelastic Stability Assessment of an Industrial Compressor Blade Including Mistuning Effects

“…A topic of particular interest to this investigation is the effects of intentional mistuning, which is typically a deliberate detuning of certain blades in an assembly. The introduction of intentional mistuning has been shown through numerical investigations [13][14][15] and even in engineering practice [16,17] to be a practical and effective measure to alleviate flutter. The mistuning section included here describes the outcomes of the performed statistical analyses of mistuned aeroelastic stability with respect to random mistuning with and without intentional mistuning.…”