Chapter 9 - Real-time mode decomposition and proper orthogonal/dynamic mode decomposition analyses of aeroacoustics and ramjet thermoacoustic instability

Abstract

A stable combustion system is preferred in practical operations for power generation and propulsion purposes. For this, a real-time mode decomposition algorithm (RDA) is developed. Emphasis is being placed on its ability to online track the dominant and secondary modes as well as other modes excited in a given combustion system. It can also be applied to decompose plane waves at multiple mode frequencies. The RDA performance is evaluated first on a numerically modeled combustor with two unstable modes present with comparable amplitude. It is then experimentally implemented on an acoustically driven non-reacting duct system with a lined section attached. Further demonstration is conducted on a modeled premixed combustor by online tracking and actively tuning a Helmholtz resonator via RDA. To gain insight on the dynamic flame-flow-acoustics interaction in a practical combustor, proper orthogonal (POD) and dynamic mode decomposition (DMD) algorithms could be applied simultaneously to obtain compensated characteristics but more complete physics of thermoacoustic instability modes. For demonstration, we apply POD and DMD on a Rijke-type and a modeled Ramjet combustor, respectively, to shed lights on the decomposed modes behaviors.