scholarly journals Rayleigh Criterion

2017 ◽  
Vol 16 (5) ◽  
pp. 203-213 ◽  
Author(s):  
Nobuo TAKAHASHI ◽  
Hiroki KIKUCHI
Keyword(s):  
Rayleigh Criterion

scholarly journals Experimental Study on Dynamic Combustion Characteristics in Swirl-Stabilized Combustors

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1609
Author(s):  
Donghyun Hwang ◽  
Kyubok Ahn
Keyword(s):  
Experimental Study ◽  
Heat Release ◽  
Dynamic Pressure ◽  
Combustion Instability ◽  
Flame Structure ◽  
Pressure Sensors ◽  
Necessary Condition ◽  
Rayleigh Criterion ◽  
Pressure Oscillations ◽  
Geometric Conditions

An experimental study was performed to investigate the combustion instability characteristics of swirl-stabilized combustors. A premixed gas composed of ethylene and air was burned under various flow and geometric conditions. Experiments were conducted by changing the inlet mean velocity, equivalence ratio, swirler vane angle, and combustor length. Two dynamic pressure sensors, a hot-wire anemometer, and a photomultiplier tube were installed to detect the pressure oscillations, velocity perturbations, and heat release fluctuations in the inlet and combustion chambers, respectively. An ICCD camera was used to capture the time-averaged flame structure. The objective was to understand the relationship between combustion instability and the Rayleigh criterion/the flame structure. When combustion instability occurred, the pressure oscillations were in-phase with the heat release oscillations. Even if the Rayleigh criterion between the pressure and heat release oscillations was satisfied, stable combustion with low pressure fluctuations was possible. This was explained by analyzing the dynamic flow and combustion data. The root-mean-square value of the heat release fluctuations was observed to predict the combustion instability region better than that of the inlet velocity fluctuations. The bifurcation of the flame structure was a necessary condition for combustion instability in this combustor. The results shed new insight into combustion instability in swirl-stabilized combustors.

A novel objective method for assessing high-contrast spatial resolution in CT based on the Rayleigh criterion

2017 ◽  
Vol 44 (2) ◽  
pp. 460-469
Author(s):  
Pu Zhang ◽  
Guoqing Wan ◽  
Fei Li ◽  
Xingdong Li ◽  
Wenli Liu ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Objective Method ◽  
High Contrast ◽  
Rayleigh Criterion

The Histogram of Pressure Oscillations Amplitudes, in Lean Premixed Combustions, Caused by Thermo-Acoustic Instabilities

2010 ◽  
Author(s):  
Nasser Seraj Mehdizadeh ◽  
Nozar Akbari
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Equivalence Ratio ◽  
Combustion Instability ◽  
Premixed Combustion ◽  
Space Distribution ◽  
Rayleigh Criterion ◽  
Pressure Oscillations ◽  
Lean Premixed

Lean premixed combustion is widely used in recent years as a method to achieve the environmental standards with regard to NOx emission. In spite of the mentioned advantage, premixed combustion systems, with equivalence ratios less than one, are susceptible to the combustion instability. To study the lean combustion instability, by experiments, one premixed combustion setup, equipped with reactant supplying system, is designed and manufactured in Amirkabir University of Technology. In this research, gaseous propane is introduced as fuel and several experiments are performed at nearly atmospheric pressure, with equivalence ratios within the range of 0.7 to 1.5. In this experiments fuel mass flow rate is varied between 2 and 4 gr/s. Unstable operating condition has been observed in combustion chamber when equivalence ratio is less than one. To distinguish the combustion instability for various operating conditions, probability density functions, spectral diagrams, and space distribution of pressure oscillations, along with Rayleigh Criterion, are utilized. Accordingly, effect of equivalence ratio on stabilizing the unstable combustion system is investigated. Moreover, convective delay time is calculated for all experiments and the results are compared with Rayleigh Criterion. This comparison has shown good agreement the experimental results and Rayleigh Criterion. Finally, stability limits are identified based on inlet mass flow rate and equivalence ratio.

Unsteady Flames and the Rayleigh Criterion

1996 ◽  
pp. 1-16 ◽  
Author(s):  
E. C. Fernandes ◽  
M. V. Heitor
Keyword(s):  
Rayleigh Criterion

Back-of-the-envelope image resolution estimation using an aberrated Rayleigh criterion

2020 ◽  
Vol 59 (33) ◽  
pp. 10236
Author(s):  
Jason Mudge
Keyword(s):  
Image Resolution ◽  
Rayleigh Criterion ◽  
Resolution Estimation

“Rayleigh criterion and acoustic energy balance in unconfined self-sustained oscillating flames” [Combust. Flame Vol. 155, Issue 3]

2008 ◽  
Vol 155 (3) ◽  
pp. 416 ◽  
Author(s):  
D. Durox ◽  
T. Schuller ◽  
N. Noiray ◽  
A.L. Birbaud ◽  
S. Candel
Keyword(s):  
Energy Balance ◽  
Acoustic Energy ◽  
Rayleigh Criterion

scholarly journals Sensitivity of the Rayleigh criterion in thermoacoustics

2019 ◽  
Vol 882 ◽  
Author(s):  
Luca Magri ◽  
Matthew P. Juniper ◽  
Jonas P. Moeck
Keyword(s):  
Rayleigh Criterion ◽  
Image Position

“Resolution” in atomic-resolution Electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 498-499
Author(s):  
Michael A. O'Keefe ◽  
John C.H. Spence
Keyword(s):  
Electron Microscopy ◽  
Signal To Noise Ratio ◽  
Dark Field ◽  
Lattice Imaging ◽  
Rayleigh Criterion ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Incoherent Imaging ◽  
General Relations ◽  
Imaging Conditions

The Rayleigh resolution criterion was developed for incoherent imaging conditions and cannot, in general, be applied to coherent high-resolution transmission electron microscopy (HRTEM). In fact, the Rayleigh criterion may lead to paradoxical results since it considers only two scatterers and does not account for the signal-to-noise ratio. It may, however, be used for dark-field HAAD STEM imaging. For the case of strong multiple scattering in HRTEM lattice imaging, the only general relations that can be assumed between the image of a specimen and its projected crystal potential are those imposed by symmetry, and the “local” HRTEM column approximation. The effects of limited resolution may produce an image of lower symmetry than that of the object. Also, misalignment along symmetry axes may preserve some symmetry elements. Under coherent conditions the ability to distinguish atoms in an image depends on their scattering phases, which are a property of the sample.

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