UROP Proceedings 2020-21

School of Engineering Department of Mechanical and Aerospace Engineering 177 Early Detection of Thermoacoustic Instability in Solid Rocket Motors Supervisor: LI Larry / MAE Student: CHAN Yan Yan / PHYS-IRE Course: UROP1100, Spring In this project, the nonlinear transition from low-amplitude aperiodic pressure fluctuations (i.e. combustion noise) to high-amplitude limit cycle oscillations inside a full-scale solid rocket motor (SRM) is studied using multifractal detrended fluctuation analysis (MFDFA) and spectral entropy ES of time series data. It is shown that the noise-like pressure fluctuations observed before combustion instability is scale-invariant and features a multifractal structure that then disappears at the onset of thermoacoustic oscillations. The fractal structures of the combustion noise and the thermoacoustic oscillations are quantified by the generalised Hurst exponent Hq and the multifractal spectrum. Additionally, the variation of the Hurst exponent H and Es as a function of time is examined, and the feasibility of using H and Es as early warning signals of an impending thermoacoustic instability in a full-scale SRM is demonstrated. Early Detection of Thermoacoustic Instability in Solid Rocket Motors Supervisor: LI Larry / MAE Student: GANI Bryan Suryaraso / MAE Course: UROP1100, Summer Thermoacoustic instability may result in excessive vibration and heat transfer in a combustion system. However, the nonlinear interactions occurring between the flow, acoustic and chemical processes make it difficult to control the system using a linear approach. Nowadays, researchers are trying to implement machine learning as a tool to eliminate or suppress this instability. This project reviews some of the latest progress made by researchers in the field. According to the literature, there are two primary research approaches. The first uses data from pressure and heat-release rate measurements. The second uses imaging and deep learning. It is acknowledged that some of the topics might need further study if they are to be deployed for the suppression of thermoacoustic instability. Nonlinear Dynamics and Closed-Loop Control of Droplet Formation in a Capillary Jet Supervisor: LI Larry / MAE Student: OLSSON Christopher Sven / AE Course: UROP3100, Fall A brief review of the currently available literature on propeller tip design for micro air vehicles is presented. There is currently no universal stand-alone metric for quantifying the efficiency of a propeller tip (energy and thrust lost). At low Reynolds numbers (Re < 50,000), propeller tip effects become increasingly important, and this effect is explored in detail with reference to potential applications in micro air vehicles.

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