scholarly journals Forced flow response analysis of a turbulent swirling annular jet flame

2021 ◽  
Vol 33 (8) ◽  
pp. 085124
Author(s):  
Christopher M. Douglas ◽  
Benjamin L. Emerson ◽  
Santosh Hemchandra ◽  
Timothy C. Lieuwen
Keyword(s):  
Forced Flow ◽  
Response Analysis ◽  
Jet Flame ◽  
Flow Response ◽  
Annular Jet

Velocity Field Response of a Forced Swirl Stabilized Premixed Flame

2017 ◽  
Author(s):  
Kiran Manoharan ◽  
Travis Smith ◽  
Benjamin Emerson ◽  
Christopher M. Douglas ◽  
Tim Lieuwen ◽  
...  
Keyword(s):  
Heat Release ◽  
Shear Layer ◽  
Recirculation Zone ◽  
Stokes Equations ◽  
Quantitative Agreement ◽  
Forced Response ◽  
Response Analysis ◽  
Annular Jet ◽  
Experimental Response ◽  
Prediction Approach

This study is motivated by the necessity to develop a low order prediction approach for unsteady heat release response characteristics in lean premixed gas turbine combustors. This in turn requires an accurate description of the coherent hydrodynamic oscillations induced in the combustor flow by acoustic forcing. Time resolved velocity and flame position fields are obtained using sPIV and OH-PLIF measurements on a single nozzle, swirl-stabilized, premixed, methane-air flame in a model “unwrapped” annular combustor rig. A natural acoustic oscillation in the rig at 115 Hz results in a coherent flow oscillation that is concentrated primarily within the shear layer between the annular jet flow and the central recirculation zone. A linear stability analysis performed about time averaged base flow fields shows that the flow does not have any self-excited hydrodynamic modes. We then compare predictions from a forced response analysis at a forcing frequency of 115 Hz, based on the linearized Navier-Stokes equations for this coherent response. Good qualitative agreement between linear forced response analysis predictions and experimental response results, is seen for the spatial variation of velocity oscillation amplitude fields, away from the burner centerline. Further, good quantitative agreement between predictions and the experimental response is seen for the phase speed of velocity oscillations along the shear layer between the annular jet and the central recirculation zone. This phase velocity is an important flow field characteristic that has a significant impact on the heat release response that results from these coherent velocity oscillations. Present methods for forced response analysis assume uniform forcing amplitude along the radial direction at the forcing location, as well as, open flows along the streamwise direction. Both these assumptions are not strictly true for the present burner which has a center body on its axis. This maybe the reason for somewhat poor qualitative and quantitative agreement between experiments and predictions at the centerline.

Structure Vibration Shape Optimization Based on Power Flow Response Analysis

2014 ◽  
Vol 490-491 ◽  
pp. 712-718
Author(s):  
Xue Bao Xia ◽  
Yang Xiang ◽  
Shao Wei Wu
Keyword(s):  
Shape Optimization ◽  
Mode Shape ◽  
Power Flow ◽  
Flow Analysis ◽  
Optimization Method ◽  
Weight Coefficient ◽  
Surface Shape ◽  
Response Analysis ◽  
Flow Response ◽  
Vibration Power Flow

Power flow analysis is a method to describe the dynamic behavior of structures by taking not only the amplitude of exciting force and velocity response into account, but also the phase between the two qualities. Shape optimization is an effective method to reduce vibration level. By choosing the vibration power flow as design objective, a shape optimization method of structure is presented. The structure surface is restructured with a series of mode shape superposition. By using genetic algorithm, the weight coefficient of each mode shape is optimized to get the best surface shape with minimum power flow response. Some examples are demonstrated to verify the efficiency and accuracy of the method.

scholarly journals The preferred mode of incompressible jets: linear frequency response analysis

2013 ◽  
Vol 716 ◽  
pp. 189-202 ◽  
Author(s):  
X. Garnaud ◽  
L. Lesshafft ◽  
P. J. Schmid ◽  
P. Huerre
Keyword(s):  
Excitation Frequency ◽  
Operating Conditions ◽  
Jet Flows ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Potential Core ◽  
External Perturbations ◽  
Flow Response ◽  
Numerical Studies ◽  
Local Shear

AbstractThe linear amplification of axisymmetric external forcing in incompressible jet flows is investigated within a fully non-parallel framework. Experimental and numerical studies have shown that isothermal jets preferably amplify external perturbations for Strouhal numbers in the range $0. 25\leq {\mathit{St}}_{D} \leq 0. 5$, depending on the operating conditions. In the present study, the optimal forcing of an incompressible jet is computed as a function of the excitation frequency. This analysis characterizes the preferred amplification as a pseudo-resonance with a dominant Strouhal number of around $0. 45$. The flow response at this frequency takes the form of a vortical wavepacket that peaks inside the potential core. Its global structure is characterized by the cooperation of local shear-layer and jet-column modes.

scholarly journals Local entrainment velocity in a premixed turbulent annular jet flame

2019 ◽  
Vol 37 (2) ◽  
pp. 2493-2501
Author(s):  
Luis Cifuentes ◽  
Andreas Kempf ◽  
Cesar Dopazo
Keyword(s):  
Jet Flame ◽  
Entrainment Velocity ◽  
Annular Jet

A New Visually Evoked Cerebral Blood Flow Response Analysis Using a Low-Frequency Estimation

2010 ◽  
Vol 36 (3) ◽  
pp. 383-391 ◽  
Author(s):  
Beatriz Rey ◽  
Valery Naranjo ◽  
Vera Parkhutik ◽  
José Tembl ◽  
Mariano Alcañiz
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Frequency Estimation ◽  
Low Frequency ◽  
Response Analysis ◽  
Blood Flow Response ◽  
Flow Response

Characteristics of Flow and Flame Behavior Behind Rifled/Unrifled Nozzles

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Kuo C. San ◽  
Hung J. Hsu
Keyword(s):  
Turbulent Flame ◽  
Flow Characteristics ◽  
Combustion Efficiency ◽  
Flame Height ◽  
Mixing Efficiency ◽  
Jet Flame ◽  
Annular Jet ◽  
Image Velocimetry ◽  
Flame Behavior ◽  
The Relationship

A novel rifled nozzle was installed behind a conventional combustion exhauster to improve combustion efficiency. The rifled nozzles improve the momentum transmission, turbulent strength, and mixing efficiency between the central jet and annular jet. The flow characteristics behind the nozzles (rifled and unrifled) were visualized and detected using the smoke-wire flow visualization, particle image velocimetry, and hot-wire anemometry. The cold flow structures were categorized into four modes—jet flow, single bubble, dual bubble, and turbulent flow. The topological scheme was adopted to analyze and verify these flow modes. The flame structures behind the nozzles (rifled and unrifled) are classified into three modes—jet flame, flickering flame, and turbulent flame—using the direct-photo visualization. The flame height of a 12-rifled nozzle is decreased by about 50% under that of an unrifled nozzle. The flame shedding frequency declines rapidly in the flickering flame mode and the relationship between the Strouhal number (Sr) and annular velocity (ua) is Sr=0.0238+0.13/ua.

A Dose-Response Analysis of Nicotine Sensitization in Adolescent Rats D2-Primed as Neonates

2010 ◽  
Author(s):  
Elizabeth A. Hanchak ◽  
Meredith L. Smith ◽  
Jessie J. Smith ◽  
Marla K. Perna ◽  
Russell W. Brown
Keyword(s):  
Dose Response ◽  
Response Analysis ◽  
Adolescent Rats
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