An Experimental and Computational Investigation of a Pulsed Air-Jet Excitation System on a Rotating Bladed Disk

The paper presents an original multiple excitation system based on electromagnets with force control. The system is specifically designed in order to investigate the dynamics of bladed disks, since it mimics the excitation existing in a real engine. Moreover, the system is suitable for forced response tests of bladed disks with nonlinear dynamic response, like in the case of presence of friction contacts, since the amplitude of the exciting force is known with good precision. For this purpose, a device called force-measuring electromagnet (FMEM) was designed and employed during the system calibration. The excitation system is applied to the test rig Octopus, which includes underplatform dampers (UPDs). Tests were carried out under different excitation force amplitude values. The tests put in evidence the presence of mistuning and the UPDs' capability of attenuating the mistuning phenomena.

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Nonlinear Modal Testing Performed by Pulsed-Air Jet Excitation System

Nonlinear Dynamics, Volume 1 - Conference Proceedings of the Society for Experimental Mechanics Series ◽

10.1007/978-3-319-29739-2_15 ◽

2016 ◽

pp. 155-170

Author(s):

M. Piraccini ◽

D. Di Maio ◽

R. Di Sante

Keyword(s):

Modal Testing ◽

Excitation System ◽

Air Jet

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An Experimental and Computational Investigation of a Pulsed Air-Jet Excitation System on a Rotating Bladed Disk

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4049014 ◽

2021 ◽

Vol 143 (1) ◽

Author(s):

Eric Kurstak ◽

Kiran D'Souza

Keyword(s):

Rotational Speed ◽

Computational Models ◽

Difficult Problem ◽

System Response ◽

Complex Nature ◽

Bladed Disk ◽

Air Jets ◽

Air Jet ◽

Blade Tip ◽

Nonsynchronous Vibrations

Abstract Nonsynchronous vibrations are a difficult problem to address for turbomachines due to the complex nature of the forcing. Such vibrations can be caused by vortex shedding, flow instabilities, stall cells, or flutter. Testing a design with such excitations can be difficult in practice due to the required forcing. This work demonstrates an experimental excitation method using pulsed air jet excitation to create nonsynchronous vibrations in engine hardware rotating at nominal design speeds. Experimental runs were conducted to excite a number of engine orders (EOs). Blade tip timing was used to measure the blade response without interfering with the blade dynamics. The bladed disk was held at a constant rotational speed while the air jets were pulsed at a sweeping frequency to simulate rotating forcing. Computational models of the physical system were constructed using parametric reduced order models that incorporate the effects of rotational speed and small mistuning. The computational model was used in simulations that mimic the experiment; the forcing was swept across the blades while being pulsed. This results in a system response that cannot be captured using traditional harmonic analyses. The computational and experimental datasets were compared through mistuning values, amplitudes, and the nodal diameter (ND) content in the system response.

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An Experimental and Computational Investigation of a Pulsed Air-Jet Excitation System on a Rotating Bladed Disk

Volume 11: Structures and Dynamics: Structural Mechanics, Vibration, and Damping; Supercritical CO2 ◽

10.1115/gt2020-16301 ◽

2020 ◽

Author(s):

Eric Kurstak ◽

Kiran D’Souza

Keyword(s):

Rotational Speed ◽

Computational Models ◽

Difficult Problem ◽

System Response ◽

Complex Nature ◽

Bladed Disk ◽

Air Jets ◽

Air Jet ◽

Blade Tip ◽

Harmonic Analyses

Abstract Non-synchronous vibrations are a difficult problem to address for turbomachines due to the complex nature of the forcing. Such vibrations can be caused by vortex shedding, flow instabilities, stall cells, or flutter. Testing a design with such excitations can be difficult in practice due to the required forcing. This work demonstrates an experimental excitation method using pulsed air jet excitation to create non-synchronous vibrations in engine hardware rotating at nominal design speeds. Experimental runs were conducted to excite a number of engine orders. Blade tip timing was used to measure the blade response without interfering with the blade dynamics. The bladed disk was held at a constant rotational speed while the air jets were pulsed at a sweeping frequency to simulate rotating forcing. Computational models of the physical system were constructed using parametric reduced order models that incorporate the effects of rotational speed and small mistuning. The computational model was used in simulations that mimic the experiment; the forcing was swept across the blades while being pulsed. This results in a system response that cannot be captured using traditional harmonic analyses. The computational and experimental datasets were compared through mistuning values, amplitudes, and the nodal diameter content in the system response.

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