Application of Dynamical Systems Theory and Complex Systems Theory to Combustion Instability in Liquid Rocket Engines
Abstract
The occurrence of thermoacoustic instabilities can potentially lead to partial or total mission failure of rockets, rising costs, increased delays, and developmental setbacks. There is a definite need to improve the definition of the onset and amplitude profile of rocket thermoacoustic instability. Analysis was done to evaluate the effect of flow, pressure, heat release rate, and the process behind self-organization which leads to the synchronization that is a major factor in thermoacoustic instability. The analysis was based on a model multi-element rocket combustor that was operated under a preheated high pressure turbulent flow rig in a fuel rich condition, to better simulate the operational conditions in a real rocket engine (or motor). The transition from small amplitude stable operation to large amplitude thermoacoustic instability occurs was highly nonlinear, consisting of typically steepened pressure wavefronts leading to the formation of shock waves. Furthermore, there was random, dynamical switching between period-3 and period-4 oscillations. To demonstrate the efficacy of measures based on dynamical systems and complex system theory, a recurrence based measure (RATIO) and two fractal based measures (multifractal spectrum width and the Hurst exponent) were established to distinguish different states of combustor operation. These measures are more robust than the existing measures such as root mean square of the oscillations, amplitude, maximum of cross correlation etc. in distinguishing the dynamical state of a rocket engine. This work successfully translated modern tools from nonlinear time series analysis to understand the complex oscillations arising in liquid rocket engines. The measures illustrated in this study can be used to validate the CFD multi-fidelity simulations used for optimizing the stability and performance metrics of the rocket comb.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 05, 2020
- Accession Number
- AD1106320
Entities
People
- Abin Krishnan
- Induja Oavithran
- Praveen Kasthuri
- R I Sujith
- Samadhan A Pawar
Organizations
- Indian Institute of Technology Madras