Characterizing energy growth during combustion instabilities: Singularvalues or eigenvalues?

2009 ◽  
Vol 32 (2) ◽  
pp. 2933-2940 ◽  
Author(s):  
Sharath Nagaraja ◽  
Kushal Kedia ◽  
R.I. Sujith
Keyword(s):  
Combustion Instabilities ◽  
Energy Growth

scholarly journals SCALING INVARIANCE IN A TIME-DEPENDENT ELLIPTICAL BILLIARD

2012 ◽  
Vol 22 (09) ◽  
pp. 1250207 ◽  
Author(s):  
DIEGO F. M. OLIVEIRA ◽  
MARKO ROBNIK
Keyword(s):  
Integrable System ◽  
Average Velocity ◽  
Moving Boundary ◽  
Time Dependent ◽  
Scaling Invariance ◽  
Energy Growth ◽  
Dynamical Properties ◽  
Scaling Arguments

We study some dynamical properties of a classical time-dependent elliptical billiard. We consider periodically moving boundary and collisions between the particle and the boundary are assumed to be elastic. Our results confirm that although the static elliptical billiard is an integrable system, after introducing time-dependent perturbation on the boundary the unlimited energy growth is observed. The behavior of the average velocity is described using scaling arguments.

Towards Low-NOx Operation in a Complex Burner: Optimization of an Annular Trapped Vortex Combustor

2013 ◽  
Author(s):  
Pradip Xavier ◽  
Bruno Renou ◽  
Gilles Cabot ◽  
Mourad A. Boukhalfa ◽  
Michel Cazalens
Keyword(s):  
Acoustic Energy ◽  
Combustion Instabilities ◽  
Chemical Parameters ◽  
Hot Gas ◽  
Highly Sensitive ◽  
Stable Flame ◽  
Mass Transfers ◽  
Gas Expansion ◽  
Trapped Vortex ◽  
Original Configuration

This paper focuses on optimizing an innovative annular Lean Premixed staged burner, following the Trapped Vortex Combustor concept. The latter consists of a lean main flame stabilized by passing past a rich cavity pilot flame. Unfortunately, this configuration is highly sensitive to combustion instabilities and the flame is not well stabilized. This work consists of adjusting aerodynamic variables, chemical parameters and burner geometry to reach a “low-NOx” operation while reducing other pollutants and getting a stable flame. Results show that stability is reached when mass transfers between main and cavity zones are reduced. Then, the main bulk velocity is increased to reduce the cavity thermal expansion, due to the hot gas expansion. In addition, the cavity flow rate is reduced to prevent from penetrating and disturbing the main flow. Re-arranging injections in the cavity also avoid local unsteady equivalence ratios, which creates an unsteady heat release and combustion with pulses. Regarding NOx, a leaner main flame combined with a sufficiently rich cavity mixture creates local stoichiometric zones at the interface between the cavity and the main zone. The latter point is found to be a good anchoring mechanism. Compared with the original configuration, a stable point of operation is found: acoustic energy is reduced by an order of 100, NOx level is less than 0.4 g/kgfuel, CO is cut by 93% with no more Unburned Hydro-Carbons.

Exponential energy growth in a Fermi accelerator

2010 ◽  
Vol 81 (5) ◽  
Author(s):  
Kushal Shah ◽  
Dmitry Turaev ◽  
Vered Rom-Kedar
Keyword(s):  
Energy Growth
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