Abstract This paper studies the heat-release oscillation response of premixed flames to oscillations in reactant stream fuel/air ratio. Prior analyses have studied this problem linear regime and shown that heat release dynamics are controlled by superposition three processes: flame speed, reaction, surface area oscillations. Each contribution has somewhat different dynamics, leading complex frequency mean ratio dependencies. The present work extends these include stretch non quasi-steady...

Global instabilities in swirling flows can significantly alter the flame and flow dynamics of swirl-stabilized flames, such as those modern gas turbine engines. In this study, we characterize interaction between precessing vortex core (PVC), which is consequence a global hydrodynamic instability, thermoacoustic instabilities, are result coupling combustor acoustics unsteady heat release rate. This study performed using experimental data obtained from model employing two concentric nozzles...

The precessing vortex core (PVC) oscillation is a commonly observed self-excited flow instability associated with the precession of breakdown bubble around axis in swirl flows. region where internal feedback forcing sustains PVC called wavemaker. Linear stability analysis (LSA) methods, conjunction large-eddy simulation (LES), can be used to identify Here, we assess data-driven approach using complex network (CNA) wavemaker nominally axisymmetric turbulent nozzle unsteady data from prior LES...

Combustion instability, the coupling between flame heat release rate oscillations and combustor acoustics, is a significant issue in operation of gas turbine combustors. This often driven by flow field. Shear layer roll-up, particular, has been shown to drive longitudinal combustion instability number systems, including both laboratory industrial One method for suppressing would be suppress receptivity shear acoustic oscillations, severing mechanism acoustics flame. Previous work suggested...

Nonlinear analysis of thermoacoustic instability is essential for the prediction frequencies, amplitudes, and stability limit cycles. Limit cycles in systems are reached when energy input from driving processes losses damping balance each other over a cycle oscillation. In this paper, an integral relation rate change system derived. This analogous to well-known Rayleigh criterion thermoacoustics, however, it can be used calculate amplitudes their stability. The applied ducted slot-stabilized...

Hydrodynamic instabilities of the flow field in lean premixed gas turbine combustors can generate velocity perturbations that wrinkle and distort flame sheet over length scales are smaller than length. The resultant heat release oscillations then potentially result combustion instability. Thus, it is essential to understand hydrodynamic instability characteristics combustor order its overall influence on characteristics. To this end, paper elucidates role fluctuating vorticity production...

With numerical methods and analysis of existing experimental results we show that combustion instability in a backward-facing step combustor can be maintained either with weak coupling between acoustic hydrodynamic modes (semi-open loop) or strong (fully closed loop).

Abstract We study the impact of H2 enrichment on unsteady flow dynamics and thermoacoustic instability in prediction control instabilities industrial turbines (PRECCINSTA) swirl combustor. The experiments were performed at atmospheric conditions with H2/CH4 fuel mixtures a global equivalence ratio 0.65 constant thermal power 20 kW. analyze data three compositions: 0%, 20%, 50% two operating modes, premixed (PM) technically (TPM). A new multiresolution modal decomposition method, using...

Combustion instability is a serious problem limiting the operating envelope of present day gas turbine systems using lean premixed combustion strategy. Gas combustors employ swirl as means for achieving fuel-air mixing well flame stabilization. However flows are complex comprised multiple shear layers recirculation zones which makes them particularly susceptible to hydrodynamic instability. We perform local stability analysis on family base flow model profiles characteristic swirling that...

Abstract The precessing vortex core (PVC) phenomenon in swirling jets is a helical instability the flow driven by coherent precession of breakdown bubble (VBB) around axis, resulting rollup shear layer. This processes region upstream VBB. Centerbodies, commonly employed combustor nozzles, create centerbody wake recirculation zone (CWRZ) that can interfere with VBB and hence suppress PVC. We study this swirl nozzle whose end face flush exit plane, using large eddy simulations (LES) linear...

The coupling between heat release oscillations produced by equivalence ratio fluctuations with combustor acoustic modes in lean premixed combustion systems, is a serious problem that limits the operation envelope of these devices. Such are an oscillating pressure drop across air inlets and/or fuel injectors due to presence oscillations. This results mass flow rates entering combustor, thereby, changing local mixture at injector/inlet locations. These perturbations advected into flame,...

The present work focuses on the formulation of transient incompressible resin flow during vacuum-assisted transfer moulding using level set front tracking method in a multi-block structured grid within finite difference framework. Initially, relation between compaction pressure and fibre volume fraction ([Formula: see text]) has been established by conducting compression tests universal tensile machine under dry wet conditions. In-plane permeability characterised as function [Formula: text]...