The effects of swirl number on the combustion characteristics in an internally-staged combustor

2021 ◽  
pp. 095440622110373
Author(s):  
Tiezheng Zhao ◽  
Xiao Liu ◽  
Zhihao Zhang ◽  
Jialong Yang ◽  
Hongtao Zheng
Keyword(s):  
Flow Field ◽  
Recirculation Zone ◽  
Three Dimensional ◽  
Combustion Characteristics ◽  
Maximum Temperature ◽  
High Concentration ◽  
Swirl Number ◽  
The Third ◽  
Flamelet Generated Manifold ◽  
Swirling Flame

The three-dimensional turbulent swirling flame in an internally-staged combustor is numerically investigated. Four cases over a range of swirl intensities are explored by the Flamelet Generated Manifold model in this paper. Special attention is paid to analyzing the variation of the flow field, temperature, major species concentrations and emissions. The results clearly show the effects of swirl number on the size of the center recirculation zone, fuel distribution and combustion characteristics. When the third premixed stage swirl number increases from 0.6 to 1.2, the axial length of the center recirculation zone decreases by 3.7%, while the radial length increases by 6.9%. The characteristics of the flow field play an important role in the spatial distribution of the fuel, which further affects the temperature distribution in the combustor. The backflow effect is enhanced, resulting in a greater concentration of fuel at the outlet of the swirler. After the maximum temperature is reached at the exit position of the pilot stage, the temperature decreases compared to the peak temperature downstream as the proportion of premixed combustion mode increases. This creates a high concentration region of OH at the outlet of the pilot stage injector and the heat release region is squeezed upstream. At the same time, the volume of the high-temperature region downstream of the pilot stage is reduced. In addition, as the swirl number of the third premixed stage increases from 0.6 to 1.2, the emissions of NO and CO decrease by 28.7% and 75%, respectively.

An Experimental Verification of a New Design for Cantilevered Stators With Large Hub Clearances

2012 ◽  
Author(s):  
Martin Lange ◽  
Konrad Vogeler ◽  
Ronald Mailach ◽  
Sergio Elorza-Gomez
Keyword(s):  
Flow Field ◽  
Experimental Verification ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Performance Data ◽  
Axial Compressors ◽  
The Third ◽  
Overall Performance ◽  
Overall Efficiency ◽  
Aero Engines

Proportionally large relative radial clearances can be found within the rear stages of multistage axial compressors of gas turbines and aero engines, with significant impact on their efficiency. A new three-dimensional design for cantilevered stators in axial compressors is presented, with the aim of improving the overall efficiency and losses of rear stage vanes with large relative hub clearances. The new vane design comprises an unconventional dihedral, with special consideration to reduce the losses caused by the hub clearance vortex. The design was tested in a 4-stage low speed axial research compressor under rear stage conditions. The results are compared to the nominal design to validate the reduction of hub clearance losses and blockage. For both designs, the hub clearances over the third and fourth stator were varied from 1.5% up to 6.0% of span. Overall performance data and flow field traverses upstream and downstream of stator 3 and rotor 4 will be presented in this article in comparison with 3D CFD results.

Confinement Effects on Flow Dynamics in Swirling Flames

2005 ◽  
Author(s):  
S. Archer ◽  
A. K. Gupta
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Direct Injection ◽  
Model Development ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Dynamics ◽  
Swirl Number ◽  
Outer Flow ◽  
Lean Direct Injection

Three-dimensional (3-D) flowfield data has been obtained using Particle Image Velocimetry (PIV) for varying swirl distributions in the burner. The 3-D data also allows one determine the local swirl number of the resulting flow. Flow characteristics of the resulting flowfield, both without and with combustion, have been examined for the effect of co- and counter-swirl under lean direct injection conditions using unconfined and confined combustor geometry. Experimental results of the effect of swirl and combustion are presented to simulate the flow dynamics of Lean Direct Injection (LDI) configuration gas turbine combustion. The selected configuration is typical because it does not make use a premixing zone and relies totally on the swirl and the injector to accomplish rapid mixing. Specifically, the effect of radial distribution of combustion air and swirl in a burner are examined under non-burning and burning conditions using propane as the fuel. The present study explores single swirler interaction with the use of an experimental double concentric swirl burner that simulates one swirler of a practical gas turbine combustor. Results showed that both swirl and combustion has significant effect on the characteristics of the internal and external recirculation zones. The calculated local swirl number differs significantly form that estimated using geometrical relationship derived from the vane angle only. The effect of combustion for the confined and unconfined geometries was also been found to be different. In the confined geometry combustion decreases the size of the recirculation zone. This is in contrast to that found for the unconfined conditions. Combustion enhances the recirculation zone in the unconfined geometry. Combustion provides greater velocity magnitudes than their counter non-combustion conditions. The counter-swirl combination resulted in smaller and more well defined internal recirculation regions. The results provide the role of swirl and combustion on the mean and turbulence characteristics of flows over a range of swirl and shear conditions between the inner and outer flow of the burner. This data provides important insights on the flow dynamics in addition to providing data for model validation and model development.

scholarly journals Enhancing the Specific Power of a PEM Fuel Cell Powered UAV with a Novel Bean-Shaped Flow Field

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2494
Author(s):  
Somayeh Toghyani ◽  
Seyed Ali Atyabi ◽  
Xin Gao
Keyword(s):  
Flow Field ◽  
Proton Exchange Membrane ◽  
Three Dimensional ◽  
Channel Length ◽  
Proton Exchange ◽  
Maximum Temperature ◽  
Specific Power ◽  
Isothermal Model ◽  
Cell Modeling ◽  
Exchange Membrane

One of the marketing challenges of unmanned aerial vehicles (UAVs) for various applications is enhancing flight durability. Due to the superior characteristics of proton exchange membrane fuel cells (PEMFCs), they have the potential to reach a longer flight time and higher payload. In this regard, a numerical assessment of a UAV air-cooled PEMFC is carried out using a three-dimensional (3-D), multiphase, and non-isothermal model on three flow fields, i.e., unblocked bean-shaped, blocked bean-shaped, and parallel. Then, the results of single-cell modeling are generalized to the PEMFC stack to provide the power of 2.5 kW for a UAV. The obtained results indicate that the strategy of rising air stoichiometry for cooling performs well in the unblocked bean-shaped design, and the maximum temperature along the channel length reaches 331.5 K at the air stoichiometric of 30. Further, it is found that the best performance of a 2.5 kW PEMFC stack is attained by the bean-shaped design without blockage, of which its volume and mass power density are 1.1 kW L−1 and 0.2 kW kg−1, respectively. It is 9.4% lighter and 6.9% more compact than the parallel flow field. Therefore, the unblocked bean-shaped design can be a good option for aerial applications.

Experimental Study on Flow Structure of Non-Premixed Swirl Burner Flows Using PIV

2011 ◽  
Vol 347-353 ◽  
pp. 2587-2592 ◽  
Author(s):  
Bing Ge ◽  
Shu Sheng Zang ◽  
Pei Qing Guo
Keyword(s):  
Flow Field ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Spatial Separation ◽  
Complex Flow ◽  
Image Velocimetry ◽  
Characteristic Modes ◽  
Swirling Flame ◽  
Development And Validation ◽  
Annular Jets

This paper focuses on investigating the characteristic modes and structures in non-premixed swirling methane/air flames. Using the Particle Image Velocimetry (PIV) technique, the experiment measured the velocity distributions of the swirling flame. Cold flow conditions have been included to provide a picture of the flow field and to demonstrate the modifications induced by combustion. The characteristic lengths, velocity vectors, streamlines, and velocity distributions are presented and discussed. The experiment shows that a large spatial separation at the exit between the central and swirling annular jets can expedite the formation of a recirculation zone. Complex flow structures are found in the recirculation zone. Moreover, the differences between cold swirling flow field and combustion swirling flow are analyzed at length. The data from this experiment is helpful for optimization of the non-premixed burner design, and can be established as benchmarks for the development and validation of combustion numerical simulations.

Effect of Swirl Number on Combustion Characteristics in a Natural Gas Diffusion Flame

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
İlker Yılmaz
Keyword(s):  
Fluid Dynamics ◽  
Natural Gas ◽  
Diffusion Flame ◽  
Recirculation Zone ◽  
Reaction Scheme ◽  
Gas Diffusion ◽  
Combustion Characteristics ◽  
Model Parameters ◽  
Swirl Number ◽  
Simulation Results

This paper presents the effect of swirl number on combustion characteristics such as temperature, velocity, gas concentrations in a natural gas diffusion flame. Numerial simulations carried out using the commercial computational fluid dynamics (CFD) code, Fluent by choosing appropriate model parameters. The combustion reaction scheme in the flame region was modeled using eddy dissipation model with one step global reaction scheme. A standard k-ε turbulence model for turbulent closure and P-I radiation model for flame radiation inside the combustor is used in the numerical simulations. In order to investigate the swirling effect on the combustion characteristics, seven different swirl numbers including 0; 0.1; 0.2; 0.3; 0.4; 0.5; and 0.6 are used in the study. Numerical results are validated and compared with the published experimental and simulation results. A good consistency is found between the present results and those published measurement and simulation results in the available literature. The results shown that the combustion characteristics such as the flame temperature, the gas concentrations including CO2, H2O, O2, and CH4 are strongly affected by the swirl number. Depending on the degree of swirl, the fluid dynamics behavior of natural gas diffusion flame including axial velocity distribution, central recirculation zone (CTRZ) and external recirculation zone (ETRZ) were also strongly affected.

Flow Dynamics of Unconfined and Confined Swirl Stabilized Gaseous Flames

2004 ◽  
Author(s):  
S. Archer ◽  
A. K. Gupta
Keyword(s):  
Gas Turbine ◽  
Recirculation Zone ◽  
Direct Injection ◽  
Model Development ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Dynamics ◽  
Swirl Number ◽  
Outer Flow ◽  
Lean Direct Injection

Three-dimensional (3-D) flowfield data has been obtained using Particle Image Velocimetry (PIV) for varying swirl distributions in the burner. The 3-D data also allows one determine the local swirl number of the resulting flow. Flow characteristics of the resulting flowfield, both without and with combustion, have been examined for the effect of co- and counter-swirl under lean direct injection conditions using unconfined and confined combustor geometry. Experimental results of the effect of swirl and combustion are presented to simulate the flow dynamics of Lean Direct Injection (LDI) configuration gas turbine combustion. The selected configuration is typical because it does not make use a premixing zone and relies totally on the swirl and the injector to accomplish rapid mixing. Specifically, the effect of radial distribution of combustion air and swirl in a burner are examined under non-burning and burning conditions using propane as the fuel. The present study explores single swirler interaction with the use of an experimental double concentric swirl burner that simulates one swirler of a practical gas turbine combustor. Results showed that both swirl and combustion has significant effect on the characteristics of the internal and external recirculation zones. The calculated local swirl number differs significantly form that estimated using geometrical relationship derived from the vane angle only. The effect of combustion for the confined and unconfined geometries was also been found to be different. In the confined geometry combustion decreases the size of the recirculation zone. This is in contrast to that found for the unconfined conditions. Combustion enhances the recirculation zone in the unconfined geometry. Combustion provides greater velocity magnitudes than their counter non-combustion conditions. The counter-swirl combination resulted in smaller and more well defined internal recirculation regions. The results provide the role of swirl and combustion on the mean and turbulence characteristics of flows over a range of swirl and shear conditions between the inner and outer flow of the burner. This data provides important insights on the flow dynamics in addition to providing data for model validation and model development.

An Experimental Verification of a New Design for Cantilevered Stators With Large Hub Clearances

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Martin Lange ◽  
Konrad Vogeler ◽  
Ronald Mailach ◽  
Sergio Elorza Gomez
Keyword(s):  
Flow Field ◽  
Experimental Verification ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Performance Data ◽  
Axial Compressors ◽  
The Third ◽  
Overall Performance ◽  
Overall Efficiency ◽  
Aero Engines

Proportionally large relative radial clearances can be found within the rear stages of multistage axial compressors of gas turbines and aero engines, with significant impact on their efficiency. A new three-dimensional design for cantilevered stators in axial compressors is presented, with the aim of improving the overall efficiency and losses of rear stage vanes with large relative hub clearances. The new vane design comprises an unconventional dihedral, with special consideration to reduce the losses caused by the hub clearance vortex. The design was tested in a 4-stage low speed axial research compressor under rear stage conditions. The results are compared to the nominal design to validate the reduction of hub clearance losses and blockage. For both designs, the hub clearances over the third and fourth stator were varied from 1.5% up to 6.0% of span. Overall performance data and flow field traverses upstream and downstream of stator 3 and rotor 4 will be presented in this article in comparison with 3D CFD results.

Flashback Propensity in Swirl Stabilized Burner With Syngas Fuels

2010 ◽  
Author(s):  
Bidhan Dam ◽  
Gilberto Corona ◽  
Ahsan Choudhuri
Keyword(s):  
Flow Field ◽  
Recirculation Zone ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Fuel Mixture ◽  
Stoichiometric Ratio ◽  
Swirl Number ◽  
Significant Phenomenon ◽  
Transient Velocity ◽  
Fuel Mixtures

In swirl stabilized burner, combustion induced vortex breakdown (CIVB) flashback is a significant phenomenon. This paper presents experimental measurements of CIVB flashback propensity for hydrogen (H2)-carbon monoxide (CO) flames. The effects of H2 concentration, and swirl number on the flashback propensity of H2-CO flames are discussed. For a given air mass flow rate, the stoichiometric ratio (%F) at which the CIVB flashback occurs decreases with the increase in H2 concentration in fuel mixtures. However it appears that near the CIVB flashback limit, the swirl strength plays a more dominating role over the H2 concentration in the fuel mixture. The flashback propensity decreases with the increase in swirl number. An analysis of the nonreacting flow field (Air 6 g/s) as well as reacting (CH4-Air and H2-CO-Air) flame near the CIVB transient velocity field was conducted. The analysis revealed that a complex vortex-chemistry interaction leading to vortex breakdown and flashback occurred. The vector flow field showed that the high swirling flow generates a more stabilized and wider recirculation zone. It also showed that the presence of H2 dictates the intensity of the flashback process.

Sign in / Sign up

Export Citation Format

Share Document