Swirl Effects on Combustion Characteristics of Premixed Flames

2000 ◽  
Vol 123 (3) ◽  
pp. 619-626 ◽  
Author(s):  
A. K. Gupta ◽  
M. J. Lewis ◽  
M. Daurer
Keyword(s):  
Thermal Behavior ◽  
Radial Distribution ◽  
Thermal Characteristic ◽  
Premixed Flames ◽  
Great Influence ◽  
Probability Density Distribution ◽  
Swirl Burner ◽  
Global Features ◽  
Outer Annulus ◽  
Annular Jets

The effect of radial distribution of swirl has been examined on the thermal behavior of two different premixed flames using a double concentric premixed swirl burner. The double concentric swirl burner allowed systematic variation in the radial distribution of swirl (both co- and counter-) between the inner and outer annulus of the burner. The burner had two annular jets and a central nozzle. Information on the thermal field in two flames formed by co- or counter-swirl in the outer annulus and co-swirl in the inner annulus has been examined. Specifically mean and fluctuating temperatures, integral and micro thermal time scales, and probability density distribution of temperatures have been determined at various spatial positions in the flames. The micro-thermocouple output was compensated to provide high-frequency (about 1 kHz) response of the thermocouple. Direct flame photographs were taken to provide information about the global features of flames and flame stability. The global and thermal characteristic data presented here provided a complete insight on the thermal behavior of co- and counter-swirl flames. The results show that the direction of swirl (co- or counter-) used to stabilize a flame from annular jets provides a great influence on flame symmetry. The simultaneous combination of co- and counter-swirl in the burner showed a very nonsymmetrical behavior of the flame. The global and thermal data presented here confirmed these findings. The results suggest significant effect of co- and counter-swirl distribution in flames on the NOx emission levels.

Numerical Simulations of Isothermal Flow in a Swirl Burner

2006 ◽  
Author(s):  
Manuel Garci´a-Villalba ◽  
Jochen Fro¨hlich ◽  
Wolfgang Rodi
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Reacting Flow ◽  
Swirl Burner ◽  
Eddy Simulation ◽  
Pressure Time ◽  
Time Signals ◽  
Flow Oscillations ◽  
Conditional Averaging ◽  
Annular Jets

In this paper; the non-reacting flow in a swirl burner is studied using Large Eddy Simulation. The configuration consists of two unconfined co-annular jets at a Reynolds number of 81500. The flow is characterized by a Swirl number of 0.93. Two cases are studied in the paper differing with respect to the axial location of the inner pilot jet. It was observed in a companion experiment (Bender and Bu¨chner, 2005) that when the inner jet is retracted the flow oscillations are considerably amplified. This is also found in the present simulations. Large-scale coherent structures rotating at a constant rate are observed when the inner jet is retracted. The rotation of the structures leads to vigorous oscillations in the velocity and pressure time signals recorded at selected points in the flow. In addition, the mean velocities, the turbulent fluctuations and the frequency of the oscillations are in good agreement with the experiments. A conditional averaging procedure is used to perform a detailed analysis of the physics leading to the low-frequency oscillations.

scholarly journals A Reliability-Based Network Equilibrium Model with Adaptive Risk-Averse Travelers

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Lei Zhao ◽  
Hongzhi Guan ◽  
Junze Zhu ◽  
Yunfeng Wei
Keyword(s):  
Travel Time ◽  
Time Distribution ◽  
Choice Behavior ◽  
Route Choice ◽  
Great Influence ◽  
User Equilibrium ◽  
Probability Density Distribution ◽  
Risk Averse ◽  
Route Choice Behavior ◽  
Travel Time Distribution

In this paper, route free-flow travel time is taken as the lower bound of route travel time to examine its impacts on budget time and reliability for degradable transportation networks. A truncated probability density distribution with respect to route travel time is proposed and the corresponding travel time budget (TTB) model is derived. The budget time and reliability are compared between TTB models with and without truncated travel time distribution. Under truncated travel time distribution, the risk-averse levels of travelers are adaptive, which are affected by the characteristics of the used routes besides the confidence level of travelers. Then, a TTB-based stochastic user equilibrium (SUE) is developed to model travelers’ route choice behavior. Moreover, its equivalent variational inequality (VI) problem is formulated and a route-based algorithm is used to solve the proposed model. Numerical results indicate that route travel time boundary produces a great influence on decision cost and route choice behavior of travelers.

Effect of Swirl on Combustion Characteristics in Premixed Flames

1998 ◽  
Vol 120 (3) ◽  
pp. 488-494 ◽  
Author(s):  
A. K. Gupta ◽  
M. J. Lewis ◽  
S. Qi
Keyword(s):  
High Frequency ◽  
Flame Structure ◽  
Premixed Flames ◽  
Temperature Data ◽  
Local Temperature ◽  
Local Distribution ◽  
Swirl Burner ◽  
Swirl Number ◽  
High Frequency Response ◽  
Global And Local

A double concentric premixed swirl burner is used to examine the structure of two different methane-air premixed flames. Direct flame photography together with local temperature data provides an opportunity to investigate the effects of swirl number distribution in each annulus on the global and local flame structure, flame stability and local distribution of thermal signatures. An R-type thermocouple compensated for high-frequency response is used to measure the local distribution of thermal signatures in two different flames, each of which represents a different of thermal signatures in two different flames, each of which represents a different of thermal signatures in two combination of swirl number in the swirl burner. In order to improve the accuracy of the temperature data at high-frequency conditions, information on the thermocouple time constant are also obtained under prevailing conditions of local temperature and velocity by compensating the heat loss from the thermocouple sensor bead. These results assist in quantifying the degree of thermal nonuniformities in the flame signatures as affected by the distribution of swirl and to develop strategies for achievinguniform distribution of temperatures in flames.

Measurements of the turbulent burning velocity and the structure of premixed flames on a low-swirl burner

2000 ◽  
Vol 28 (1) ◽  
pp. 359-366 ◽  
Author(s):  
T. Plessing ◽  
C. Kortschik ◽  
N. Peters ◽  
M.S. Mansour ◽  
R.K. Cheng
Keyword(s):  
Burning Velocity ◽  
Premixed Flames ◽  
Swirl Burner ◽  
Turbulent Burning Velocity

scholarly journals Effect of Swirl on Combustion Characteristics in Premixed Flames

1997 ◽  
Author(s):  
S. Qi ◽  
A. K. Gupta ◽  
M. J. Lewis
Keyword(s):  
High Frequency ◽  
Flame Structure ◽  
Premixed Flames ◽  
Temperature Data ◽  
Local Temperature ◽  
Local Distribution ◽  
Swirl Burner ◽  
Swirl Number ◽  
High Frequency Response ◽  
Global And Local

A double concentric premixed swirl burner is used to examine the structure of two different methane-air premixed flames. Direct flame photography together with local temperature data provides an opportunity to investigate the effects of swirl number distribution in each annulus on the global and local flame structure, flame stability and local distribution of thermal signatures. An R-type thermocouple compensated for high-frequency response is used to measure the local distribution of thermal signatures in two different flames, each of which represents a different combination of swirl number in the swirl burner. In order to improve the accuracy of the temperature data at high-frequency conditions, information on the thermocouple time constant are also obtained under prevailing conditions of local temperature and velocity by compensating the heat loss from the thermocouple sensor bead. These results assist in quantifying the degree of thermal nonuniformities in the flame signatures as affected by the distribution of swirl and to develop strategies for achieving uniform distribution of temperatures in flames.

The Effect of Swirl Burner Design Configuration on Combustion and Emission Characteristics of Lean Pre-vaporized Premixed Flames

Energy ◽  
2021 ◽  
pp. 120622
Author(s):  
Belal Y. Belal ◽  
Gesheng Li ◽  
Zunhua Zhang ◽  
H.M. El-Batsh ◽  
Hany A. Moneib ◽  
...  
Keyword(s):  
Premixed Flames ◽  
Emission Characteristics ◽  
Swirl Burner ◽  
Burner Design

Swirl Distribution Effects on the Thermal Characteristics of Premixed Flames

2001 ◽  
Author(s):  
Sean Archer ◽  
Ashwani K. Gupta
Keyword(s):  
Time Scales ◽  
Premixed Flames ◽  
Power Spectra ◽  
Thermal Characteristics ◽  
Recirculation Region ◽  
Emission Characteristics ◽  
Operational Conditions ◽  
Mean Temperature ◽  
Integral Time ◽  
Outer Annulus

Abstract An experimental investigation has been carried out on four premixed flames using a double concentric swirl burner. The influence of radial distribution of swirl on the global flame behavior, thermal and emission characteristics have been determined. Temperature data was compensated with time constant data to generate mean and fluctuating temperature maps, probability density distributions of temperature, power spectra and thermal integral- and micro-time scales in the flames. Direct flame photographs were taken to archive flame shape and light intensity. These data provided valuable information for practical combustors on better swirl configurations. These configurations will depend heavily on the designed power settings. Contributed results directly from this investigation are for a lean premixed flame to achieve low emission and higher efficiency. The results reveal that in a counter-swirl configuration, the swirl strength in inner annulus should be greater than the outer annulus. However, for the co-swirl configuration it is more beneficial to have smaller swirl strength in the inner annulus than the outer annulus. It is found that premixed flames can possess significant circumferential non-uniformities at all flow and operational conditions. Detailed data shows that the flame thermal field and temperature distribution is strongly related to its emissions. High NOx emission is found in flames where the integral time scales and the mean temperature are high in the presumed lower recirculation region. High CO formation is found in flames that have high integral time scales in the lower recirculation region but have a low mean temperature in this same region. Thermal time scales provide important information on the thermal and emission characteristics of premixed flames.

Sign in / Sign up

Export Citation Format

Share Document