scholarly journals Fire Safety Evaluation of High-Pressure Ammonia Storage Systems

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 520
Author(s):  
Yong Ho Chung ◽  
Won-Ju Lee ◽  
Jun Kang ◽  
Sung Hwan Yoon
Keyword(s):  
High Pressure ◽  
Strain Rate ◽  
Oxygen Concentration ◽  
Flame Structure ◽  
Flame Temperature ◽  
Safety Evaluation ◽  
Fire Spread ◽  
Flammability Limit ◽  
Radiation Heat Loss ◽  
Auto Ignition

Ammonia combustion is a promising energy source as a carbon free fuel without greenhouse gas emissions. However, since the auto-ignition temperature is 651 degrees Celsius and the range of flammability limit is not wide compared to other fuels, fundamental studies on ammonia fires have rarely been conducted so far. Therefore, this study aims to numerically estimate fire spread characteristics when ammonia fuel in a high-pressure state leaks to the outside, especially focusing on the flammability limit according to oxygen concentration. Three kinds of reaction mechanism for numerical analysis were adopted to compare the flame structure, flammability limit, and combustion characteristics. Plank-mean absorption coefficients of nitrogen species were taken for the radiation model, in addition to the optically thin model. The effect of radiation heat loss could be identified from the maximum flame temperature trend at a low strain rate. It was confirmed that the pyrolysis of ammonia in the preheated zone results in hydrogen production, and the generated hydrogen contributes to heat release rate in the flame zone. It is found that the contribution of hydrogen would be an important role in the flammability limit of ammonia combustion. Finally, Karlovitz and Peclet numbers showed well the extinction behaviors of ammonia combustion as a result of LOC (Limit Oxygen Concentration) analysis as a function of global strain rate.

Effect of Strain Rate and Pressure on the Flame Structure and Emission Characteristics of Syngas Flames

2007 ◽  
Author(s):  
Sibendu Som ◽  
Anita I. Rami´rez ◽  
Jonathan Hagerdorn ◽  
Alexei Saveliev ◽  
Suresh K. Aggarwal
Keyword(s):  
Strain Rate ◽  
Reaction Zone ◽  
Laminar Flame ◽  
Flame Structure ◽  
Flame Temperature ◽  
Chemical Kinetic ◽  
No Production ◽  
Emission Characteristics ◽  
Strain Rates ◽  
Fundamental Understanding

Synthesis gas or “Syngas” is being recognized as a viable energy source worldwide, particularly for stationary power generation due to its wide flexibility in fuel sources. There are gaps in the fundamental understanding of syngas combustion and emissions characteristics, especially at elevated pressures, high strain rates and in more practical conditions. This paper presents a numerical and experimental investigation to gain fundamental understanding of combustion and emission characteristics of syngas with varying composition, pressure and strain rate. Two representative syngas fuel mixtures, 50% H2 / 50% CO and 5% H2 / 95% CO (% vol.), are chosen, three detailed chemical kinetic models are used namely, GRI 3.0, Davis et al. and Li et al. mechanisms. Davis et al. mechanism agrees best with the experimental data hence is used to simulate the partially premixed flame structures at all pressures. Results indicate that for the pressure range investigated, a typical double flame structure was observed characterized by a rich premixed reaction zone (RPZ) on the fuel side and a nonpremixed reaction zone (NPZ) at the oxidizer side nozzle with the stabilizing due to the H2 chemistry rather than the CO chemistry. Sensitivity analysis to mass burning rates for unstretched laminar flame shows that flames are more sensitive to H2 chemistry. For both representative mixtures an increase in pressure leads to a significant increase in NO due to increase in flame temperature. The emission index for these flames is also found to follow a similar behavior with pressure. Although flame temperatures were higher for flame A, total NO is lower for these flames due to increases in reburn characteristics. Thermal route dominates NO production while, prompt route is negligible. Experimental analysis on the stability of nonpremixed syngas/air flames showed that the flames were very stable for the range of strain rates investigated. At low strain rates it required 0.5% H2 to establish a stable flame.

LES of Hydrogen Enriched Methane/Air Combustion in the SGT-800 Burner at Real Engine Conditions

2018 ◽  
Author(s):  
Daniel Moëll ◽  
Daniel Lörstad ◽  
Xue-Song Bai
Keyword(s):  
High Pressure ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Flame Temperature ◽  
Flow Simulation ◽  
Sudden Expansion ◽  
Inlet Temperature ◽  
Complex Flow ◽  
Control Variables ◽  
Hydrogen Enrichment

DLE (Dry Low Emission) techniques are widely used today to reduce the harmful NOx emissions associated with high combustion temperatures. In many DLE systems the fuel and air are pre-mixed which effectively keep the flame temperature as low as possible, ideally equal to the turbine inlet temperature. By using pre-mixing stability issues such as flash back and combustion driven dynamics may occur. Operating the engine with hydrogen diluted natural gas will decrease the flash back limits of the system due to the high diffusivity and highly reactive nature of hydrogen. In this study the stability effects of hydrogen diluted into methane in the Siemens SGT-800 combustor is studied. The SGT-800 combustor is an annular combustor where the flame is stabilized using a swirl burner combined with a sudden expansion combustor. The expansion gives rise to a vortex break down where the flame stabilizes in the local low speed zones. Here a single burner sector is studied using the flow solver Siemens PLM software STAR-CCM+. The turbulence is simulated through the use of LES (Large Eddy Simulation) where the largest energy carrying flow scales are resolved and only the smaller scales are modelled. The chemistry is coupled to the turbulent flow simulation by the use of FGM (Flamelet Generated Manifolds) which are integrated using presumed probability density functions. The FGM approach assumes that the local flame structure is laminar and that all species across a flame can be related to a set of control variables. The control variables in this case are the heat loss, the mixture fraction and its variance and a reaction progress variable. In this paper two effects are studied, first the transition from an atmospheric flame to a pressurized flame and second the effect of hydrogen enrichment. The flame shape and position are mainly affected by the transition from atmospheric to high pressure, where the power density increases by almost a factor of 20. The flame is moving further upstream closer to the burner in all pressurized cases. The hydrogen enrichment plays a strong role in how the combustion driven dynamics is coupling with the acoustics of the rig. The high pressure pure methane case show a strong pressure peak whereas the hydrogen enriched case dampens that peak and distributes the energy to other frequencies. This work shows that high fidelity CFD is capable of capturing complex flow and flame interactions such as thermoacoustic instabilities in industrial scale systems.

Auto-Ignition and Numerical Analysis on High-Pressure Combustion of Premixed Methane-Air mixtures in Highly Preheated and Diluted Environment

2021 ◽  
pp. 1-23
Author(s):  
Subrat Garnayak ◽  
Ayman M Elbaz ◽  
Olawole Kuti ◽  
Sukanta Kumar Dash ◽  
William L Roberts ◽  
...  
Keyword(s):  
High Pressure ◽  
Numerical Analysis ◽  
Auto Ignition

Viscous Rayleigh-Taylor Instability Experiments at High Pressure and Strain Rate

2010 ◽  
Vol 104 (13) ◽  
Author(s):  
Hye-Sook Park ◽  
K. T. Lorenz ◽  
R. M. Cavallo ◽  
S. M. Pollaine ◽  
S. T. Prisbrey ◽  
...  
Keyword(s):  
High Pressure ◽  
Strain Rate ◽  
Taylor Instability ◽  
Rayleigh Taylor Instability

Towards a High-Pressure Microchannel Reactor for Fuel Characterization

2021 ◽  
Author(s):  
David Akinpelu ◽  
Ingmar Schoegl
Keyword(s):  
High Pressure ◽  
Oxygen Concentration ◽  
Combustion Characteristics ◽  
Test Time ◽  
Potential Candidate ◽  
Microchannel Reactor ◽  
Transportation Fuels ◽  
Intermediate Pressure ◽  
Fuel Blends ◽  
The Impact

Abstract Within the area of combustion, externally heated microtubes have been introduced to study the combustion characteristics of fuels and fuel blends. Microreactors have advantages over other conventional fuel testing methods because of their potential to test small volumes (< 20 μl) at high throughput. In this work, a high-pressure microreactor is designed and implemented to test fuels up to a pressure of 20 bar where automated testing reduces test time substantially. The novelty of this device is its capability to operate at pressure exceeding the current state of the art of 12 bar. The combustion behavior of fuels is tested in an externally heated quartz tube, with a diameter less than the conventional quenching diameter of the fuel. The ultimate objective of the experiment is to investigate the impact of fuel on flame characteristics. The ability to reach engine relevant pressure conditions and its inherent small volume requirements make this device a potential candidate for measurements of laboratory transportation fuels and fuel blends. For initial validation, tests from an earlier intermediate pressure experiment with ethane/air and nitrogen mixtures are repeated. Chemiluminescence images are taken to evaluate the combustion characteristics in terms of the three classical flame regimes: weak flames, Flames with Repetitive Extinction, and Ignition (FREI) and normal flames. Previous results at intermediate pressure showed that as the pressure increases, the weak flame and FREI regimes shift towards lower velocities. Also, as dilution level increase (i.e. reducing oxygen concentration), the transition from the weak flame to FREI becomes less abrupt and is completely lost for marginal oxygen concentration. The objective of this study is to document flame dynamics at higher pressures.

Hydrogen Blending Into Ansaldo Energia AE94.3A Gas Turbine: High Pressure Tests, Field Experience and Modelling Considerations

2021 ◽  
Author(s):  
A. Ciani ◽  
L. Tay-Wo-Chong ◽  
A. Amato ◽  
E. Bertolotto ◽  
G. Spataro
Keyword(s):  
High Pressure ◽  
Gas Turbine ◽  
Power Plants ◽  
Flame Structure ◽  
Flux Ratio ◽  
Fuel Blends ◽  
Pressure Tests ◽  
Fuel Staging ◽  
Combustion Tests ◽  
The Impact

Abstract Fuel flexibility in gas turbine development has become increasingly important and modern engines need to cope with a broad variety of fuels. The target to operate power plants with hydrogen-based fuels and low emissions will be of paramount importance in a future focusing on electric power decarbonization. Ansaldo Energia AE94.3A engine acquired broad experience with operation of various natural gas and hydrogen fuel blends, starting in 2006 in the Brindisi (Italy) power plant. Based on the exhaustive experience acquired in the field, this paper describes the latest advancements characterizing the operation of the AE94.3A burner with high pressure combustion tests adding hydrogen blends ranging from 0 to 40% in volume. The interpretation of the test results is supported by reactive and non-reactive simulations describing the effects of varying fuel reactivity on the flame structure as well as the impact of fuel / air momentum flux ratio on the fuel / air interaction and fuel distribution in the combustion chamber. As expected, increasing amounts of hydrogen in the fuel are also associated with higher amounts of NOx production, however this effect could be countered by optimization of the fuel staging strategy, based on the mentioned CFD considerations and feedback from high pressure tests.

scholarly journals Effect of the Strain Rate on the Fracture Behaviour of High Pressure Pre-Charged Samples

Proceedings ◽  
2018 ◽  
Vol 2 (23) ◽  
pp. 1417
Author(s):  
Guillermo Álvarez Díaz ◽  
Tomás Eduardo García Suárez ◽  
Cristina. Rodríguez González ◽  
Francisco Javier Belzunce Varela
Keyword(s):  
Fracture Toughness ◽  
High Pressure ◽  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
Fracture Behaviour ◽  
Structural Steels ◽  
Gaseous Hydrogen ◽  
Displacement Rate ◽  
Steel Strength ◽  
Fracture Tests

The aim of this work is to study the effect of the displacement rate on the hydrogen embrittlement of two different structural steels grades used in energetic applications. With this purpose, samples were pre-charged with gaseous hydrogen at 19.5 MPa and 450 °C for 21 h. Then, fracture tests of the pre-charged specimens were performed, using different displacement rates. It is showed that the lower is the displacement rate and the largest is the steel strength, the strongest is the reduction of the fracture toughness due to the presence of internal hydrogen.

scholarly journals Effects of strain rate and CO2 on no formation in CH4/N2/O2 counter-flow diffusion flames

2018 ◽  
Vol 22 (Suppl. 2) ◽  
pp. 769-776
Author(s):  
Fei Ren ◽  
Longkai Xiang ◽  
Huaqiang Chu ◽  
Weiwei Han
Keyword(s):  
Strain Rate ◽  
Diffusion Flames ◽  
Numerical Study ◽  
Flame Temperature ◽  
Co2 Concentration ◽  
No Production ◽  
Counter Flow ◽  
Detailed Chemistry ◽  
No Formation ◽  
Key Factor

The reduction of nitrogen oxides in the high temperature flame is the key factor affecting the oxygen-enriched combustion performance. A numerical study using an OPPDIF code with detailed chemistry mechanism GRI 3.0 was carried out to focus on the effect of strain rate (25-130 s?1) and CO2 addition (0-0.59) on the oxidizer side on NO emission in CH4 / N2 / O2 counter-flow diffusion flame. The mole fraction profiles of flame structures, NO, NO2 and some selected radicals (H, O, OH) and the sensitivity of the dominant reactions contributing to NO formation in the counter-flow diffusion flames of CH4\/ N2 /O2 and CH4 / N2 / O2 / CO2 were obtained. The results indicated that the flame temperature and the amount of NO were reduced while the sensitivity of reactions to the prompt NO formation was gradually increased with the increasing strain rate. Furthermore, it is shown that with the increasing CO2 concentration in oxidizer, CO2 was directly involved in the reaction of NO consumption. The flame temperature and NO production were decreased dramatically and the mechanism of NO production was transformed from the thermal to prompt route.

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