Experimental and Numerical Investigation of Ultra-Wet Methane Combustion Technique for Power Generation

2020 ◽  
Author(s):  
Kai Zhang ◽  
Simeon Dybe ◽  
Yazhou Shen ◽  
Sebastian Schimek ◽  
Christian Oliver Paschereit ◽  
...  
Keyword(s):  
Flame Temperature ◽  
Ccd Camera ◽  
Methane Combustion ◽  
High Heat ◽  
Flame Stabilization ◽  
Electricity Production ◽  
Reacting Flow ◽  
Single Digit ◽  
Steam Content ◽  
Precessing Vortex Core

Abstract Using steam as heat carrier and working media has merits to increase electric efficiency up to 60% and decrease NOx emission to single-digit compared to dry gas turbine cycles. These attribute to the physical properties of steam as having high heat capacity to reduce local flame temperature, and hence reduce emissions by inhibiting thermal NOx forward reaction rate. In this work, ultra-high steam content with steam-to-air mass ratio up to 40% is premixed with methane air mixture before entering a swirl-stabilized HP-burner for combustion. Significant change of flame from V-shape (attached) to M shape (detached) is observed through a transparent combustion chamber. The measurement of chemiluminescence OH* is conducted with an intensified CCD-camera band-pass filtered at 320nm. Large eddy simulation is used to capture reacting flow features. Reasonably well agreements between experimental data and numerical results are obtained for both attached and detached flames in terms of OH* distribution. Distributed flame front is clearly identified with LES for wet methane combustion associated with 35% steam-to-air ratio corresponding to a high Karlovitz number flame. Slightly unstable combustion is observed when steam-to-air ratio exceeds 40% featuring an onset of flame blow-off. Interaction between precessing vortex core and the flame is presented at different level of steam dilution, and conclusions are drawn regarding flame stabilization. The in-depth understanding of ultra-wet combustion is an important step towards the use of sustainable, steam-diluted bio-syngas for electricity production.

Experimental and Numerical Investigation of Ultra-Wet Methane Combustion Technique for Power Generation

2020 ◽  
Author(s):  
Kai Zhang ◽  
Simeon Dybe ◽  
Yazhou Shen ◽  
Sebastian Schimek ◽  
Christian Oliver Paschereit ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Flame Temperature ◽  
Ccd Camera ◽  
Methane Combustion ◽  
High Heat ◽  
Flame Stabilization ◽  
Electricity Production ◽  
Reacting Flow ◽  
Single Digit ◽  
Steam Content

Abstract Using steam as a heat carrier and working media has merits to increase electric efficiency up to 60% and decrease NOx emission to single-digit compared to dry gas turbine cycles. These attribute primarily to the physical properties of steam as having high heat capacity to reduce local flame temperature, and hence reduce emissions by inhibiting the thermal NOx forward reaction rate. In this work, ultra-high steam content with a steam-to-air mass ratio of up to 40% is premixed with methane-air mixture before entering into a swirl-stabilized HP-burner for combustion. A significant change of flame from V-shape (attached) to M shape (detached) is observed through a transparent combustion chamber whilst changing steam content. The measurement of chemiluminescence OH* is conducted with an intensified CCD-camera band-pass filtered at 320nm. Following these measurements, large eddy simulation is used to capture reacting flow features. Reasonably well agreements between experimental data and numerical results are obtained for both attached and detached flames in terms of the OH* distribution. Slight inconsistency of OH* intensity is mainly due to uncollected wall temperature which leads to either over- or under-prediction of chemical reaction rate depending on the experimental flame positions. Distributed flame front is clearly identified with LES for wet methane combustion associated with 35% steam-to-air ratio corresponding to a high Karlovitz number flame. Slightly unstable combustion is observed when the steam-to-air ratio exceeds 40% featuring an onset of flame blow-off. In addition, interaction between precessing vortex core and the flame is presented for different level of steam dilution, and conclusions are drawn regarding the flame stabilization. The in-depth understanding of the ultra-wet combustion is an important step towards the use of sustainable, steam-diluted biosyngas for electricity production.

Numerical Investigations of a Swirl-Stabilized Premixed Flame at Ultra-Wet Conditions

2011 ◽  
Author(s):  
Oliver Kru¨ger ◽  
Katharina Go¨ckeler ◽  
Sebastian Go¨ke ◽  
Christian Oliver Paschereit ◽  
Christophe Duwig ◽  
...  
Keyword(s):  
Flow Field ◽  
Turbulent Energy ◽  
Dominant Frequency ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Reacting Flow ◽  
Steam Content ◽  
Precessing Vortex Core ◽  
Reduced Mechanism ◽  
Flow Features

The present study focuses on the numerical investigation of a generic swirl-stabilized burner operated with methane at ultra-wet conditions. The burner is fed with a preheated homogeneous mixture formed by steam and air. As a set of operating conditions atmospheric pressure, inlet temperature of 673K, equivalence ratio of 0.85 and a steam content of 30% is applied. Large eddy simulations have been performed to investigate the flow features. In a first step the non-reacting flow field was investigated with water as working medium. Comparison with Particle Image Velocimetry (PIV) and Laser-Doppler Velocimetry (LDV) measurements conducted in a water tunnel facility showed that an excellent agreement within the experimental uncertainty is obtained for the flow field. A dominant frequency in the turbulent energy spectrum was identified, which corresponds to the motion associated with a precessing vortex core (PVC). In order to investigate the reactive flow in a second step, a customized solver for handling low Mach number reacting flows based on an implicit LES approach was developed. As reaction mechanism a reduced 4 steps / 7 species global scheme was used. To compare the simulations qualitatively with a wet flame, OH chemiluminescence pictures serve as a reference. The simulations showed a more compact flame compared to the OH pictures. Nevertheless, the prolongation and position of the flame were found to be reasonable. The reduced mechanism captures the main effects, such as the reduction of the peak and mean temperatures. Furthermore, the presence of a PVC in the reacting flow could be determined and was not suppressed by heat-release.

scholarly journals The Security of Energy Supply from Internal Combustion Engines Using Coal Mine Methane—Forecasting of the Electrical Energy Generation

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3049
Author(s):  
Marek Borowski ◽  
Piotr Życzkowski ◽  
Klaudia Zwolińska ◽  
Rafał Łuczak ◽  
Zbigniew Kuczera
Keyword(s):  
Coal Mine ◽  
Predictive Models ◽  
Coalbed Methane ◽  
Internal Combustion Engines ◽  
Drainage System ◽  
Production Capacity ◽  
Methane Combustion ◽  
Economic Benefits ◽  
Electricity Production ◽  
Coal Mine Methane

Increasing emissions from mining areas and a high global warming potential of methane have caused gas management to become a vital challenge. At the same time, it provides the opportunity to obtain economic benefits. In addition, the use of combined heat and power (CHP) in the case of coalbed methane combustion enables much more efficient use of this fuel. The article analyses the possibility of electricity production using gas engines fueled with methane captured from the Budryk coal mine in Poland. The basic issue concerning the energy production from coalbed methane is the continuity of supply, which is to ensure the required amount and concentration of the gas mixture for combustion. Hence, the reliability of supply for electricity production is of key importance. The analysis included the basic characterization of both the daily and annual methane capture by the mine’s methane drainage system, as well as the development of predictive models to determine electricity production based on hourly capture and time parameters. To forecast electricity production, predictive models that are based on five parameters have been adopted. Models were prepared based on three time variables, i.e., month, day, hour, and two values from the gas drainage system-capture and concentration of the methane. For this purpose, artificial neural networks with different properties were tested. The developed models have a high value of correlation coefficient. but showed deviations concerning the very low values persisting for a short time. The study shows that electricity production forecasting is possible, but it requires data on many variables that directly affect the production capacity of the system.

Why Non-Uniform Density Suppresses the Precessing Vortex Core

2013 ◽  
Author(s):  
Kilian Oberleithner ◽  
Steffen Terhaar ◽  
Lothar Rukes ◽  
Christian Oliver Paschereit
Keyword(s):  
Natural Gas ◽  
Vortex Core ◽  
Hydrodynamic Instability ◽  
Density Field ◽  
Density Stratification ◽  
Reacting Flow ◽  
Global Instability ◽  
Global Mode ◽  
Precessing Vortex Core ◽  
Flow Oscillations

Isothermal swirling jets undergoing vortex breakdown are known to be susceptible to self-excited flow oscillations. They manifest in a precessing vortex core and synchronized growth of large-scale vortical structures. Recent theoretical studies associate these dynamics with the onset of a global hydrodynamic instability mode. These global modes also emerge in reacting flows, thereby crucially affecting the mixing characteristics and the flame dynamics. It is, however, observed that these self-excited flow oscillations are often suppressed in the reacting flow, while they are clearly present at isothermal conditions. This study provides strong evidence that the suppression of the precessing vortex core is caused by density stratification created by the flame. This mechanism is revealed by considering two reacting flow configurations: The first configuration represents a detached steam-diluted natural gas swirl-stabilized flame featuring a strong precessing vortex core. The second represents a natural gas swirl-stabilized flame anchoring near the combustor inlet, which does not exhibit self-excited oscillations. Experiments are conducted in a generic combustor test rig and the flow dynamics are captured using PIV and LDA. The corresponding density fields are approximated from the seeding density using a quantitative light sheet technique. The experimental results are compared to the global instability properties derived from hydrodynamic linear stability theory. Excellent agreement between the theoretically derived global mode frequency and measured precession frequency provide sufficient evidence to conclude that the self-excited oscillations are, indeed, driven by a global hydrodynamic instability. The effect of the density field on the global instability is studied explicitly by performing the analysis with and without density stratification. It turns out that the significant change on instability is caused by the radial density gradients in the inner recirculation zone and not by the change of the mean velocity field. The present work provides a theoretical framework to analyze the global hydrodynamic instability of realistic combustion configurations. It allows relating the flame position and the resulting density field to the emergence of a precessing vortex core.

Combustion Optimization for the ALSTOM GT13E2 Gas Turbine

2006 ◽  
Author(s):  
Ch. Steinbach ◽  
N. Ulibarri ◽  
M. Garay ◽  
H. Lu¨bcke ◽  
Th. Meeuwissen ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Flame Temperature ◽  
Air Entrainment ◽  
Flame Stabilization ◽  
Flame Stability ◽  
Nox Emissions ◽  
Combustion Control ◽  
Control Logic ◽  
The Individual ◽  
Combustion Optimization

The NOx emissions of low NOx premix combustors are not only determined by the burner design, but also by the multi burner interaction and the related distribution of air and fuel flows to the individual burners. Often the factors that have a positive impact on NOx emission have a negative impact on the flame stability, so the main challenge is to find an optimum point with the lowest achievable NOx while maintaining good flame stability. The hottest flame zones are where most of the NOx is formed. Avoiding such zones in the combustor (by homogenization of the flame temperature) reduces NOx emissions significantly. Improving the flame stability and the combustion control allows the combustor to operate at a lower average flame temperature and NOx emissions. ALSTOM developed a combustion optimization package for the GT13E2. The optimization package development focused on three major issues: • Flame stability; • Homogenization of flame temperature distribution in the combustor; • Combustion control logic. The solution introduced consists of: • The reduction of cooling air entrainment in the primary flame zone for improved flame stability; • The optical measurement of the individual burner flame temperatures and their homogenization by burner tuning valves; • Closed loop control logic to control the combustion dependent on the pulsation signal. This paper shows how fundamental combustion research methods were applied to derive effective optimization measures. The flame temperature measurement technique will be presented along with results of the measurement and their application in homogenization of the combustor temperature distribution in an engine equipped with measures to improve flame stabilization. The main results achieved are: • Widening of the main burner group operation range; • Improved use of the low NOx operation range; • NOx reduction at the combustor pulsation limit and hence, large margins to the European emission limit (50 mg/m3 @ 15%O2).

Time-Resolved PIV Measurements of Non-Reacting Flow Field in a Swirl-Stabilized Combustor Without and With Porous Inserts for Acoustic Control

2014 ◽  
Author(s):  
Joseph Meadows ◽  
Ajay K. Agrawal
Keyword(s):  
Flow Field ◽  
Direct Injection ◽  
Combustion Noise ◽  
Reacting Flow ◽  
Turbulent Structures ◽  
Time Resolved ◽  
Turbulence Structures ◽  
Precessing Vortex Core ◽  
Acoustic Control ◽  
Acoustic Instabilities

Combustion noise and thermo-acoustic instabilities are of primary importance in highly critical applications such as rocket propulsion systems, power generation, and jet propulsion engines. Mechanisms for combustion instabilities are extremely complex because they often involve interactions among several different physical phenomena such as unsteady flame propagation leading to unsteady flow field, acoustic wave propagation, natural and forced hydrodynamic instabilities, etc. In the past, we have utilized porous inert media (PIM) to mitigate combustion noise and thermo-acoustic instabilities in both lean premixed (LPM) and lean direct injection (LDI) combustion systems. While these studies demonstrated the efficacy of the PIM concept to mitigate noise and thermo-acoustic instabilities, the actual mechanisms involved have not been understood. The present study utilizes time-resolved particle image velocimetry to measure the turbulent flow field in a non-reacting swirl-stabilized combustor without and with PIM. Although the flow field inside the annulus of the PIM cannot be observed, measurements immediately downstream of the PIM provide insight into the turbulent structures. Results are analyzed using the Proper Orthogonal Decomposition (POD) method and show that the PIM alters the flow field in an advantageous manner by modifying the turbulence structures and eliminating the corner recirculation zones and precessing vortex core, which would ultimately affect the acoustic behavior in a favorable manner.

scholarly journals Influence of Eddy-Generation Mechanism on the Characteristic of On-Source Fire Whirl

2019 ◽  
Vol 9 (19) ◽  
pp. 3989 ◽  
Author(s):  
Cheng Wang ◽  
Anthony Chun Yin Yuen ◽  
Qing Nian Chan ◽  
Timothy Bo Yuan Chen ◽  
Qian Chen ◽  
...  
Keyword(s):  
Flame Structure ◽  
Flame Temperature ◽  
Combustion Process ◽  
Flame Height ◽  
Reacting Flow ◽  
Detailed Chemistry ◽  
Eddy Generation ◽  
Fire Whirl ◽  
Generation Mechanisms ◽  
The Impact

This paper numerically examines the characterisation of fire whirl formulated under various entrainment conditions in an enclosed configuration. The numerical framework, integrating large eddy simulation and detailed chemistry, is constructed to assess the whirling flame behaviours. The proposed model constraints the convoluted coupling effects, e.g., the interrelation between combustion, flow dynamics and radiative feedback, thus focuses on assessing the impact on flame structure and flow behaviour solely attribute to the eddy-generation mechanisms. The baseline model is validated well against the experimental data. The data of the comparison case, with the introduction of additional flow channelling slit, is subsequently generated for comparison. The result suggests that, with the intensified circulation, the generated fire whirl increased by 9.42 % in peak flame temperature, 84.38 % in visible flame height, 6.81 % in axial velocity, and 46.14 % in velocity dominant region. The fire whirl core radius of the comparison case was well constrained within all monitored heights, whereas that of the baseline tended to disperse at 0.5   m height-above-burner. This study demonstrates that amplified eddy generation via the additional flow channelling slit enhances the mixing of all reactant species and intensifies the combustion process, resulting in an elongated and converging whirling core of the reacting flow.

Investigation of Precessing-Vortex-Core–Flame Interaction Based on Tomographic Reconstruction Techniques

2012 ◽  
Author(s):  
Jonas P. Moeck ◽  
Jean-Francois Bourgouin ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Sébastien Candel
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Vortex Core ◽  
Tomographic Reconstruction ◽  
Measurement Techniques ◽  
Flame Stabilization ◽  
Oscillation Pattern ◽  
Precessing Vortex Core ◽  
Helical Mode

Unsteady helical flow structures, such as the precessing vortex core (PVC), are often observed in swirling flows with vortex breakdown. Although this type of flow is of high relevance for industrial combustors, the role of these flow instabilities in reacting systems, in particular their effect on flame stabilization and combustion instabilities, remains poorly understood. The three-dimensional structure of the interaction between the helical mode and the flame is difficult to assess with common measurement techniques, such as chemiluminescence imaging, due to the non-axisymmetry of the oscillation pattern. In the present work, a novel method is proposed to determine the full field of the heat release rate perturbation associated with the helical mode. This method requires only line-of-sight integrated information from a single camera. Tomographic reconstruction techniques are used, exploiting the fact that the helical mode is a rotating structure. Reconstruction algorithms are presented that are tailored to the specific spatio-temporal structure of the oscillation pattern, and it is shown that these techniques outperform standard methods. The proposed methodology is applied in a turbulent swirl-stabilized model combustor with significant PVC oscillations. Images from an intensified high-speed camera are used for the reconstruction. The analysis shows that the helical mode perturbs the flame in the inner and the outer shear layers of the annular jet and thereby creates helical traveling waves. The perturbation in the outer shear layer grows significantly in downstream direction and causes strong heat release rate fluctuations when impinging on the combustor wall.

Experimental study on the effect of air throttling on supersonic combustion

2016 ◽  
Vol 232 (3) ◽  
pp. 472-480 ◽  
Author(s):  
Ye Tian ◽  
Shunhua Yang ◽  
Baoguo Xiao ◽  
Jialing Le
Keyword(s):  
Experimental Study ◽  
Mass Flux ◽  
Equivalence Ratio ◽  
Flame Stabilization ◽  
Wall Pressure ◽  
Supersonic Combustion ◽  
Reacting Flow ◽  
Flux Rate ◽  
Shock Train ◽  
Scramjet Combustor

The effect of air throttling on supersonic combustion was investigated by experiments in the present paper. Our results indicated that, in the non-reacting flow, a shock train could be generated in the scramjet combustor due to the increased backpressure caused by air throttling, and the wall pressure increased obviously. But when the mass flux rate of air throttling was not large enough, the shock train would oscillate with the flow. In the reacting flow, the flame stabilization was achieved in the combustor without air throttling when the equivalence ratio of kerosene was 0.2 and 0.31, but the flame was blown off when the equivalence ratio of kerosene was 0.45. On the contrary, the kerosene (equivalence ratio: 0.45) was ignited successfully in the combustor with air throttling, and it kept burning all the time in the cases with air throttling −5% (the flux of air throttling was 5% of the inflow flux) and with air throttling −14% (the flux of air throttling was 14% of the inflow flux), but the flame was blown off in the case with air throttling −1.1% after kerosene had burnt 70 ms. The flux of air throttling should be large enough to achieve flame stabilization, and the hydrogen and air throttling should both exist all the time in order to keep the flame burning steadily.

Soot temperature and concentration measurements from colour charge coupled device camera images using a three-colour method

2001 ◽  
Vol 215 (9) ◽  
pp. 1041-1052 ◽  
Author(s):  
S Simonini ◽  
S. J. Elston ◽  
C. R. Stone
Keyword(s):  
Response Curve ◽  
Flame Temperature ◽  
Ccd Camera ◽  
Soot Concentration ◽  
Charge Coupled Device ◽  
Soot Loading ◽  
Concentration Measurements ◽  
Operating Points ◽  
Late Stages ◽  
Colour Charge

The three-colour method has been developed in order to turn chromatic information in charge coupled device (CCD) camera images of combustion into flame temperature and soot concentration measurements. The method showed the following advantages over the two-colour method from which it is derived: only one camera is needed; no further calibration is required once the response curve of the camera is known; it does not rely on light intensity but on ratios between colour components, making it easy to adapt to different operating points with different name brightness. The results on temperature evaluation were compared with a thermodynamic model, and better agreement was found in the late stages of the cycle, when the radiation from chemical reactions becomes negligible. The error analysis showed that the calculations for soot concentration are ill-conditioned, but when the results are integrated to give a soot loading the accuracy is improved and there is clear evidence of soot evolution and destruction during combustion.

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