scholarly journals Numerical investigation on combustion instabilities and its passive control

2012 ◽  
Author(s):  
Zhiyuan Zhong
Keyword(s):  
Numerical Investigation ◽  
Passive Control ◽  
Combustion Instabilities

scholarly journals Passive control of instabilities in combustion systems with heat exchanger

2017 ◽  
Vol 10 (4) ◽  
pp. 362-379 ◽  
Author(s):  
Aswathy Surendran ◽  
Maria A Heckl ◽  
Naseh Hosseini ◽  
Omke Jan Teerling
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Transfer Function ◽  
Heat Source ◽  
Passive Control ◽  
Time Lag ◽  
Acoustic Scattering ◽  
Resonant Mode ◽  
Combustion Instabilities ◽  
Wide Range

One of the major concerns in the operability of power generation systems is their susceptibility to combustion instabilities. In this work, we explore whether a heat exchanger, an integral component of a domestic boiler, can be made to act as a passive controller that suppresses combustion instabilities. The combustor is modelled as a quarter-wave resonator (1-D, open at one end, closed at the other) with a compact heat source inside, which is modelled by a time-lag law. The heat exchanger is modelled as an array of tubes with bias flow and is placed near the closed end of the resonator, causing it to behave like a cavity-backed slit plate: an effective acoustic absorber. For simplicity and ease of analysis, we treat the physical processes of heat transfer and acoustic scattering occurring at the heat exchanger as two individual processes separated by an infinitesimal distance. The aeroacoustic response of the tube array is modelled using a quasi-steady approach and the heat transfer across the heat exchanger is modelled by assuming it to be a heat sink. Unsteady numerical simulations were carried out to obtain the heat exchanger transfer function, which is the response of the heat transfer at heat exchanger to upstream velocity perturbations. Combining the aeroacoustic response and the heat exchanger transfer function, in the limit of the distance between these processes tending to zero, gives the net influence of the heat exchanger. Other parameters of interest are the heat source location and the cavity length (the distance between the tube array and the closed end). We then construct stability maps for the first resonant mode of the aforementioned combustor configuration, for various parameter combinations. Our model predicts that stability can be achieved for a wide range of parameters.

A Novel Strategy for Passive Control of Combustion Instabilities Through Modification of Flame Dynamics

2008 ◽  
Author(s):  
Nicolas Noiray ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Se´bastien Candel
Keyword(s):  
Passive Control ◽  
Full Range ◽  
Premixed Flames ◽  
Perforated Plate ◽  
Operating Conditions ◽  
System Stability ◽  
Injection System ◽  
Coherent Motion ◽  
Dynamical Response ◽  
Combustion Instabilities

Passive control of combustion instabilities is explored in the case of systems featuring a collection of premixed flames. The method devised in this research differs from the general strategies employed to passively hinder the growth of acoustic-combustion oscillations by augmenting acoustic damping. Dissipation of acoustic energy is usually obtained by connecting Helmholtz resonators or quarter wave type cavities or by placing perforated plate linings around the system. While these systems effectively reduce pressure oscillations, optimum performance is not always obtained over the full range of operating conditions and their implementation requires substantial space which is not often available in practice. Conceptually, these standard techniques deal with the consequences of combustion instabilities but not with the driving sources. It is shown here that an alternative solution may be to directly act on the causes of the onset of thermo-acoustic coupling. The basic idea is to modify the flames dynamics using the dynamical response of the injection system. The principle of the passive control strategy proposed on this basis is to counteract the onset of oscillations by tackling the underlying causes. The injection system is modified to avoid a coherent motion of the flames when they are submitted to an acoustic modulation and reduce the coupling between acoustic perturbations and heat release fluctuations. Numerical simulations and experimental data are presented and one may infer that the method could bring a substantial improvement to the system stability. The efficiency of this technique is demonstrated in the case of small premixed flames anchored on a multipoint injection system (the configuration is that of a premixed gaseous-fueled multipoint dump combustor), but the principle is more general and can be extended to larger scale turbulent combustors featuring a collection of flames.

Dynamic phase converter for passive control of combustion instabilities

2009 ◽  
Vol 32 (2) ◽  
pp. 3163-3170 ◽  
Author(s):  
N. Noiray ◽  
D. Durox ◽  
T. Schuller ◽  
S. Candel
Keyword(s):  
Passive Control ◽  
Combustion Instabilities ◽  
Dynamic Phase ◽  
Phase Converter

scholarly journals Influence of Heat Transfer and Material Temperature on Combustion Instabilities in a Swirl Burner

2016 ◽  
Vol 139 (5) ◽  
Author(s):  
Christian Kraus ◽  
Laurent Selle ◽  
Thierry Poinsot ◽  
Christoph M. Arndt ◽  
Henning Bockhorn
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Passive Control ◽  
Unstable Mode ◽  
Combustion Instabilities ◽  
Ambient Conditions ◽  
Swirl Burner ◽  
Helmholtz Resonators ◽  
Eddy Simulation ◽  
Limited Frequency

The current work focuses on the large eddy simulation (LES) of combustion instability in a laboratory-scale swirl burner. Air and fuel are injected at ambient conditions. Heat conduction from the combustion chamber to the plenums results in a preheating of the air and fuel flows above ambient conditions. The paper compares two computations: In the first computation, the temperature of the injected reactants is 300 K (equivalent to the experiment) and the combustor walls are treated as adiabatic. The frequency of the unstable mode (≈ 635 Hz) deviates significantly from the measured frequency (≈ 750 Hz). In the second computation, the preheating effect observed in the experiment and the heat losses at the combustion chamber walls are taken into account. The frequency (≈ 725 Hz) of the unstable mode agrees well with the experiment. These results illustrate the importance of accounting for heat transfer/losses when applying LES for the prediction of combustion instabilities. Uncertainties caused by unsuitable modeling strategies when using computational fluid dynamics for the prediction of combustion instabilities can lead to an improper design of passive control methods (such as Helmholtz resonators) as these are often only effective in a limited frequency range.

Breakup of Liquid Jets Emerging From Elliptic Orifices

2011 ◽  
Author(s):  
Ghobad Amini ◽  
Ali Dolatabadi
Keyword(s):  
Passive Control ◽  
Fuel Efficiency ◽  
Ambient Air ◽  
Spreading Rate ◽  
Liquid Jets ◽  
Combustion Instabilities ◽  
Mass Entrainment ◽  
Circular Jets ◽  
Primary Breakup ◽  
Nozzle Geometries

Passive control can result in increasing fuel efficiency and reducing combustion instabilities of gas turbine spray combustors. Through the use of geometric modifications of the conventional circular nozzles, this method potentially enhances mixing which is responsible for entraining the bulk air necessary for combustion. Several studies show that elliptic jets have higher mass entrainment and spreading rate compared to the equivalent circular jets [1]. The majority of these works have been limited to gaseous jets. The present study focuses on a liquid spray discharging into still ambient air from a single-hole injector with elliptic cross-section. The primary breakup is investigated using a theoretical approach. Characteristics of elliptic orifice jet are compared with circular orifice jet under different breakup regimes and various nozzle geometries.

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