Assessment of Stabilization Mechanisms of Confined, Turbulent, Lifted Jet Flames: Effects of Ambient Coflow

The aim of this investigation is to determine the effects of confinement on the stabilization of turbulent, lifted methane (CH4) jet flames. A confinement cylinder (stainless steel) separates the coflow from the ambient air and restricts excess room air from being entrained into the combustion chamber, and thus produces varying stabilization patterns. The experiments were executed using fully confined, semi-confined, and unconfined conditions, as well as by varying fuel flow rate and coflow velocity (ambient air flowing in the same direction as the fuel jet). Methane flames experience liftoff and blowout at well-known conditions for unconfined jets, however, it was determined that with semi-confined conditions the flame does not experience blowout. Instead of the conventional unconfined stabilization patterns, an intense, intermittent behavior of the flame was observed. This sporadic behavior of the flame, while under semi-confinement, was determined to be a result from the restricted oxidizer access as well as the asymmetrical boundary layer that forms due to the viewing window. While under full confinement the flame behaved in a similar method as while under no confinement (full ambient air access). The stable nature of the flame while fully confined lacked the expected change in leading edge fluctuations that normally occur in turbulent jet flames. These behaviors address the combustion chemistry (lack of oxygen), turbulent mixing, and heat release that combine to produce the observed phenomena.

Download Full-text

Effect of CO2 Dilution on Flame Structure and Soot and NO Formations in CH4-Air Nonpremixed Flames

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4001809 ◽

2010 ◽

Vol 132 (12) ◽

Cited By ~ 9

Author(s):

Arindam Samanta ◽

Ranjan Ganguly ◽

Amitava Datta

Keyword(s):

Flame Structure ◽

Flame Length ◽

Nonpremixed Flames ◽

Fuel Flow Rate ◽

Heating Value ◽

Flame Radiation ◽

Fuel Flow ◽

Fuel Jet ◽

Jet Velocity ◽

Fuel Stream

In the present work, a numerical analysis has been presented to show the variations in flame structure, flame radiation, and formations of soot and NO in methane-air laminar nonpremixed flames with different CO2 dilutions of fuel. It is observed that the flame length reduces as the dilution of the fuel stream by CO2 increases while maintaining constant fuel jet velocity at the burner tip. However, the flame length remains almost unchanged with different blends of CH4 and CO2 if the burner loading (i.e., fuel flow rate×heating value of fuel) is kept constant. Both soot and NO formations decrease monotonically when the CO2 fraction in the fuel is increased. The radiation from the flame also decreases when CO2 dilution of the fuel is increased, particularly, when the fuel jet velocity is maintained constant.

Download Full-text

Robust outflow boundary conditions for strongly buoyant turbulent jet flames

Proceedings of the Sixth International Symposium On Turbulence, Heat and Mass Transfer ◽

10.1615/ichmt.2009.turbulheatmasstransf.1270 ◽

2009 ◽

Author(s):

C. Walchshofer ◽

Helfried Steiner ◽

Gunter Brenn

Keyword(s):

Boundary Conditions ◽

Turbulent Jet ◽

Jet Flames ◽

Outflow Boundary Conditions ◽

Outflow Boundary ◽

Turbulent Jet Flames

Download Full-text

Dynamic Simulation of a HRSG System for a Given Start-Up/Shut Down Curve

Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts A and B ◽

10.1115/imece2011-62468 ◽

2011 ◽

Author(s):

Hun Cha ◽

Yoo Seok Song ◽

Kyu Jong Kim ◽

Jung Rae Kim ◽

Sung Min KIM

Keyword(s):

Dynamic Analysis ◽

Gas Turbine ◽

Flow Rate ◽

Exhaust Gas ◽

Fuel Flow Rate ◽

Fuel Flow ◽

Start Up ◽

Gas Turbine Exhaust ◽

Main Steam ◽

Duct Burner

An inappropriate design of HRSG (Heat Recovery Steam Generator) may lead to mechanical problems including the fatigue failure caused by rapid load change such as operating trip, start-up or shut down. The performance of HRSG with dynamic analysis should be investigated in case of start-up or shutdown. In this study, dynamic analysis for the HRSG system was carried out by commercial software. The HRSG system was modeled with HP, IP, LP evaporator, duct burner, superheater, reheater and economizer. The main variables for the analysis were the temperature and mass flow rate from gas turbine and fuel flow rate of duct burner for given start-up (cold/warm/hot) and shutdown curve. The results showed that the exhaust gas condition of gas turbine and fuel flow rate of duct burner were main factors controlling the performance of HRSG such as flow rate and temperature of main steam from final superheater and pressure of HP drum. The time delay at the change of steam temperature between gas turbine exhaust gas and HP steam was within 2 minutes at any analysis cases.

Download Full-text

Topological imaging of turbulent premixed, prevaporized liquid fuel jet flames using CH (C-X) band PLIF

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2020.08.021 ◽

2020 ◽

Author(s):

Thomas A. McManus ◽

Amirreza Gandomkar ◽

Campbell Carter ◽

Patton M. Allison

Keyword(s):

Liquid Fuel ◽

Jet Flames ◽

Fuel Jet ◽

X Band ◽

Turbulent Premixed

Download Full-text

Model Analysis of Syngas Combustion and Emissions for a Micro Gas Turbine

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4029102 ◽

2015 ◽

Vol 137 (6) ◽

Cited By ~ 6

Author(s):

Chi-Rong Liu ◽

Hsin-Yi Shih

Keyword(s):

Gas Turbine ◽

Flow Rate ◽

Heat Input ◽

Emission Characteristics ◽

Nox Emissions ◽

Fuel Flow Rate ◽

Micro Gas Turbine ◽

Fuel Flow ◽

Temperature Distributions ◽

Flame Structures

The purpose of this study is to investigate the combustion and emission characteristics of syngas fuels applied in a micro gas turbine, which is originally designed for a natural gas fired engine. The computation results were conducted by a numerical model, which consists of the three-dimension compressible k–ε model for turbulent flow and PPDF (presumed probability density function) model for combustion process. As the syngas is substituted for methane, the fuel flow rate and the total heat input to the combustor from the methane/syngas blended fuels are varied with syngas compositions and syngas substitution percentages. The computed results presented the syngas substitution effects on the combustion and emission characteristics at different syngas percentages (up to 90%) for three typical syngas compositions and the conditions where syngas applied at fixed fuel flow rate and at fixed heat input were examined. Results showed the flame structures varied with different syngas substitution percentages. The high temperature regions were dense and concentrated on the core of the primary zone for H2-rich syngas, and then shifted to the sides of the combustor when syngas percentages were high. The NOx emissions decreased with increasing syngas percentages, but NOx emissions are higher at higher hydrogen content at the same syngas percentage. The CO2 emissions decreased for 10% syngas substitution, but then increased as syngas percentage increased. Only using H2-rich syngas could produce less carbon dioxide. The detailed flame structures, temperature distributions, and gas emissions of the combustor were presented and compared. The exit temperature distributions and pattern factor (PF) were also discussed. Before syngas fuels are utilized as an alternative fuel for the micro gas turbine, further experimental testing is needed as the modeling results provide a guidance for the improved designs of the combustor.

Download Full-text

A Numerical Investigation Into the Interaction Between Current Flow and Fuel Consumption in a Segmented-in-Series Tubular SOFC

Journal of Fuel Cell Science and Technology ◽

10.1115/1.3005386 ◽

2009 ◽

Vol 6 (3) ◽

Cited By ~ 1

Author(s):

B. A. Haberman ◽

A. J. Marquis

Keyword(s):

Density Distribution ◽

Fuel Consumption ◽

Current Density ◽

Current Flow ◽

Flow Direction ◽

Ionic Current ◽

Leading Edge ◽

Current Density Distribution ◽

Fuel Flow ◽

In Series

A typical segmented-in-series tubular solid oxide fuel cell (SOFC) consists of flattened ceramic support tubes with rows of electrochemical cells fabricated on their outer surfaces connected in series. It is desirable to design this type of SOFC to operate with a uniform electrolyte current density distribution to make the most efficient use of the available space and possibly to help minimize the onset of cell component degradation. Predicting the electrolyte current density distribution requires an understanding of the many physical and electrochemical processes occurring, and these are simulated using the newly developed SOHAB multiphysics computer code. Of particular interest is the interaction between the current flow within the cells and the consumption of fuel from an adjacent internal gas supply channel. Initial simulations showed that in the absence of fuel consumption, ionic current tends to concentrate near the leading edge of each electrolyte. Further simulations that included fuel consumption showed that the choice of fuel flow direction can have a strong effect on the current flow distribution. The electrolyte current density distribution is biased toward the upstream fuel flow direction because ionic current preferentially flows in regions rich in fuel. Thus the correct choice of fuel flow direction can lead to more uniform electrolyte current density distributions, and hence it is an important design consideration for tubular segmented-in-series SOFCs. Overall, it was found that the choice of fuel flow direction has a negligible effect on the output voltage of the fuel cells.

Download Full-text

A Method to Measure the Fuel Distribution and the Fuel Captured by V–Gutter Flameholder in High Speed Airstream

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/85-gt-42 ◽

1985 ◽

Author(s):

Gu Shan-Jian ◽

Yang Mao-Lin ◽

Li Xiang-Yi

Keyword(s):

Flow Rate ◽

Experimental Error ◽

High Speed ◽

Fuel Flow Rate ◽

Fuel Distribution ◽

Fuel Flow ◽

Sampling Condition ◽

Detailed Determination

A method to measure the fuel distribution and the percentage of fuel flow rate captured by a V-gutter flameholder in a high speed airstream has been developed. The effects of configuration and size of the probe and temprature of the sample mixture in the probe on measurement have been investigated. The detailed determination of isokinetic sampling condition is described. The effects of V-gutter geometry on flowfield have been considered. The total experimental error is of the order ±5%.

Download Full-text

System Level Analysis of Acoustically Forced Nonpremixed Swirling Flames

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4027297 ◽

2014 ◽

Vol 6 (3) ◽

Cited By ~ 3

Author(s):

Uyi Idahosa ◽

Saptarshi Basu ◽

Ankur Miglani

Keyword(s):

Heat Release ◽

Flow Rate ◽

Ccd Camera ◽

Time Dependent ◽

Fuel Flow Rate ◽

Fuel Flow ◽

Flame Response ◽

Rate Oscillations ◽

Swirling Flames ◽

Flame Sheet

This paper reports an experimental investigation of dynamic response of nonpremixed atmospheric swirling flames subjected to external, longitudinal acoustic excitation. Acoustic perturbations of varying frequencies (fp = 0–315 Hz) and velocity amplitudes (0.03 ≤ u′/Uavg ≤ 0.30) are imposed on the flames with various swirl intensities (S = 0.09 and 0.34). Flame dynamics at these swirl levels are studied for both constant and time-dependent fuel flow rate configurations. Heat release rates are quantified using a photomultiplier (PMT) and simultaneously imaged with a phase-locked CCD camera. The PMT and CCD camera are fitted with 430 nm ±10 nm band pass filters for CH* chemiluminescence intensity measurements. Flame transfer functions and continuous wavelet transforms (CWT) of heat release rate oscillations are used in order to understand the flame response at various burner swirl intensity and fuel flow rate settings. In addition, the natural modes of mixing and reaction processes are examined using the magnitude squared coherence analysis between major flame dynamics parameters. A low-pass filter characteristic is obtained with highly responsive flames below forcing frequencies of 200 Hz while the most significant flame response is observed at 105 Hz forcing mode. High strain rates induced in the flame sheet are observed to cause periodic extinction at localized regions of the flame sheet. Low swirl flames at lean fuel flow rates exhibit significant localized extinction and re-ignition of the flame sheet in the absence of acoustic forcing. However, pulsed flames exhibit increased resistance to straining due to the constrained inner recirculation zones (IRZ) resulting from acoustic perturbations that are transmitted by the co-flowing air. Wavelet spectra also show prominence of low frequency heat release rate oscillations for leaner (C2) flame configurations. For the time-dependent fuel flow rate flames, higher un-mixedness levels at lower swirl intensity is observed to induce periodic re-ignition as the flame approaches extinction. Increased swirl is observed to extend the time-to-extinction for both pulsed and unpulsed flame configurations under time-dependent fuel flow rate conditions.

Download Full-text