Authors:

Smit Kapadia

Date Created:

Not specified

Course Title:

Professor:

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About Paper:

Vibrations in an engine can cause structural damage if the operating frequency coincides with the natural frequency of individual components, or the frequency amplitude is too high for the engine to handle. Researchers have analyzed critical frequencies and modes of industrial turbomachinery, but little literature exists for microscale engines. This study aims to characterize resonance in a Micro Gas Turbine engine, which has an expected rotational speed of 98,000 RPM, turbine inlet temperature of 1520 °F, and 24 lbs of thrust. Hydrogen is used with compressed heated air to perform the combustion cycle. We investigate the effect of varying the equivalence ratio, by controlling heated air mass flow rate, on engine frequencies during startup, shutdown, and steady-state sequences. Piezoelectric accelerometers are attached to the engine casing, clocked around the turbomachinery. Data from the accelerometers is converted from the time domain to the frequency domain using a Fast Fourier Transform (FFT) to obtain the engine's frequency spectrum. Principal modes of resonance are identified by amplitude peaks in the frequency data and are compared to natural frequency predictions from Finite Element Models (FEMs). A relationship between equivalence ratio and resonant frequencies is derived, which can be leveraged to select an optimal equivalence ratio for avoiding structural damage.

Source:

Purdue University / 2023

Topics:

No topics listed

Co-authors:

Smit Kapadia