Inert Gas Influence on Propagation Velocity of Methane-air Laminar Flames

2018 ◽  
Vol 69 (1) ◽  
pp. 196-200 ◽  
Author(s):  
Maria Mitu ◽  
Venera Giurcan ◽  
Domnina Razus ◽  
Dumitru Oancea
Keyword(s):  
Experimental Data ◽  
Kinetic Modeling ◽  
Early Stage ◽  
Pressure Rise ◽  
Laminar Flames ◽  
Inert Gas ◽  
Spherical Vessel ◽  
Pressure Time ◽  
Expansion Coefficients ◽  
Propagation Velocities

The flame propagation in methane-air mixtures diluted by inert additives (He, Ar, N2, CO2) was studied by means of pressure-time records of laminar deflagrations occurring in a spherical vessel with central ignition. Experiments were made using mixtures with various equivalence ratios between 0.610 and 1.310 and various inert concentrations between 5 and 25 vol%, at various initial pressures between 50 and 200 kPa. Examination of pressure-time records in the early stage of explosions delivered the normal burning velocities Su via the coefficients of the cubic law of pressure rise, using a previously described procedure. The propagation velocities (or the flame speed) were calculated from the normal burning velocities using the expansion coefficients of the unburnt gas during the isobaric combustion. The propagation velocities of examined systems obtained from experimental data were examined against the propagation velocities obtained from kinetic modeling of methane-air-inert combustion by means of 1D COSILAB package using the GRI 3.0 mechanism.

scholarly journals Laminar Burning Velocities of Hydrogen-Blended Methane–Air and Natural Gas–Air Mixtures, Calculated from the Early Stage of p(t) Records in a Spherical Vessel

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7556
Author(s):  
Maria Mitu ◽  
Domnina Razus ◽  
Volkmar Schroeder
Keyword(s):  
Natural Gas ◽  
Initial Conditions ◽  
Numerical Study ◽  
Early Stage ◽  
Linear Trend ◽  
Burning Velocity ◽  
Pressure Rise ◽  
Spherical Vessel ◽  
Practical Applications ◽  
Hydrogen Addition

The flammable hydrogen-blended methane–air and natural gas–air mixtures raise specific safety and environmental issues in the industry and transportation; therefore, their explosion characteristics such as the explosion limits, explosion pressures, and rates of pressure rise have significant importance from a safety point of view. At the same time, the laminar burning velocities are the most useful parameters for practical applications and in basic studies for the validation of reaction mechanisms and modeling turbulent combustion. In the present study, an experimental and numerical study of the effect of hydrogen addition on the laminar burning velocity (LBV) of methane–air and natural gas–air mixtures was conducted, using mixtures with equivalence ratios within 0.90 and 1.30 and various hydrogen fractions rH within 0.0 and 0.5. The experiments were performed in a 14 L spherical vessel with central ignition at ambient initial conditions. The LBVs were calculated from p(t) data, determined in accordance with EN 15967, by using only the early stage of flame propagation. The results show that hydrogen addition determines an increase in LBV for all examined binary flammable mixtures. The LBV variation versus the fraction of added hydrogen, rH, follows a linear trend only at moderate hydrogen fractions. The further increase in rH results in a stronger variation in LBV, as shown by both experimental and computed LBVs. Hydrogen addition significantly changes the thermal diffusivity of flammable CH4–air or NG–air mixtures, the rate of heat release, and the concentration of active radical species in the flame front and contribute, thus, to LBV variation.

Pressure rise generated by the expansion of a local gas volume in a closed vessel

2009 ◽  
Vol 465 (2112) ◽  
pp. 3627-3646 ◽  
Author(s):  
Douglas Stamps ◽  
Edward Cooper ◽  
Ryan Egbert ◽  
Steve Heerdink ◽  
Valerie Stringer
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Volume Fraction ◽  
Pressure Rise ◽  
Initial Pressure ◽  
Inert Gas ◽  
Closed Vessel ◽  
Gas Combustion ◽  
Gas Volume ◽  
Theoretical Results

Experiments were conducted to determine the pressure rise that results from either the combustion of a localized gas volume or the expansion of a pressurized gas volume adjacent to an inert gas in a closed vessel. The experiments consisted of either pressurized air or the combustion of stoichiometric and fuel-lean hydrogen–air mixtures compressing an inert gas. The pressure rise in the inert gas was measured as a function of either the volume fraction or the initial pressure of the expanding gas. Helium, nitrogen, air and carbon dioxide were tested to explore the effect of inert gas heat capacity on the pressure rise. The final pressure of the inert gas increased with the volume fraction and initial pressure of the expanding gas, and was influenced to a lesser extent by the heat capacity of the inert gas. A model was assessed using the experimental data, and the theoretical results were consistent with the observed trends. This model and other published models were assessed and compared using prior data for localized gas combustion surrounded by an inert gas and the partial combustion of homogeneous methane–air mixtures.

scholarly journals Experimental Study and Kinetic Modeling of Laminar Flame Propagation in Premixed Stoichiometric n-butane-air Mixture

2019 ◽  
Vol 70 (4) ◽  
pp. 1125-1131 ◽  
Author(s):  
Venera Giurcan ◽  
Maria Mitu ◽  
Domnina Razus ◽  
Dumitru Oancea
Keyword(s):  
Initial Temperature ◽  
Laminar Flame ◽  
Early Stage ◽  
Kinetic Modelling ◽  
Pressure Rise ◽  
Activation Parameters ◽  
Similar Data ◽  
Spherical Vessel ◽  
Spherical Flames ◽  
Temperature And Pressure

The laminar burning velocities and propagation speeds of stoichiometric n-butane-air mixture were obtained for outwardly propagating spherical flames by measurements of pressure rise during the early stage of propagation in a spherical vessel. The experiments were carried out at various initial pressures within 0.3 and 1.2 bar, and various initial temperatures within 298 and 423 K. The experimental laminar burning velocities were compared with those provided by the detailed kinetic modelling based on Warnatz mechanism for combustion of C1-C4 hydrocarbons, using INSFLA package. The baric and thermal coefficients of laminar burning velocities, calculated from their dependence on initial temperature and pressure, were compared with coefficients characteristic for other fuel-air mixtures. The overall activation parameters (reaction order and activation energy) are reported and discussed in comparison with similar data characteristic for alkane-air flames.

scholarly journals Propagation of CH4-N2O-N2 Flames in a Closed Spherical Vessel

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 851
Author(s):  
Maria Mitu ◽  
Venera Giurcan ◽  
Codina Movileanu ◽  
Domnina Razus ◽  
Dumitru Oancea
Keyword(s):  
Flame Propagation ◽  
Internal Combustion Engines ◽  
Early Stage ◽  
Initial Pressure ◽  
Spherical Vessel ◽  
Industry Research ◽  
Closed Cell ◽  
Safety Parameters ◽  
Protection Devices ◽  
Expansion Coefficients

Flammable fuel-N2O mixtures raise safety and environmental protection issues in areas where these mixtures are used (such as: industry, research, internal combustion engines). Therefore, it is important to know their laminar combustion velocities and propagation speeds—important safety parameters for design of active protection devices against gas explosions and corresponding safety recommendations. In this paper, the laminar combustion velocities of N2-diluted CH4-N2O flames, obtained in experiments on outwardly propagating flames, at various initial pressures (within 0.5–2.0 bar) and room temperature, are reported. The experiments were made in a 0.5 L spherical cell with central ignition. The laminar combustion velocities were calculated from the constants of cubic law of flame propagation during the early stage of closed cell explosions and the expansion coefficients of unburned flammable mixtures, using the adiabatic model of the flame propagation. The expansion coefficients were determined from equilibrium calculations on flames propagating under isobaric conditions. The laminar combustion velocities were compared with data reported in the literature. Using the laminar combustion velocities and the expansion coefficients, the propagation speeds of N2-diluted CH4-N2O flames were calculated. Both laminar combustion velocities and propagation speeds decrease with the initial pressure increase.

scholarly journals Explosion Characteristics of Propanol Isomer–Air Mixtures

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1574 ◽  
Author(s):  
Jan Skřínský ◽  
Tadeáš Ochodek
Keyword(s):  
Maximum Rate ◽  
Pressure Rise ◽  
Spherical Vessel ◽  
Explosion Pressure ◽  
Pressure Time ◽  
Vessel Volume ◽  
Deflagration Index ◽  
Pressure Maximum ◽  
Series Of Experiments ◽  
Effects Of Temperature

This paper describes a series of experiments performed to study the explosion characteristics of propanol isomer (1-propanol and 2-propanol)–air binary mixtures. The experiments were conducted in two different experimental arrangements—a 0.02 m3 oil-heated spherical vessel and a 1.00 m3 electro-heated spherical vessel—for different equivalence ratios between 0.3 and 1.7, and initial temperatures of 50, 100, and 150 °C. More than 150 pressure–time curves were recorded. The effects of temperature and test vessel volume on various explosion characteristics, such as the maximum explosion pressure, maximum rate of pressure rise, deflagration index, and the lower and upper explosion limits were investigated and the results were further compared with the results available in literature for other alcohols, namely methanol, ethanol, 1-butanol, and 1-pentanol. The most important results from evaluated experiments are the values of deflagration index 89–98 bar·m/s for 2-propanol and 105–108 bar·m/s for 1-propanol/2-propanol–air mixtures. These values are used to describe the effect of isomer blends on a deflagration process and to rate the effects of an explosion.

Diagnostics of metal samples using the results of experimental and theoretical study of positively charged microparticles formed upon sample destruction

2018 ◽  
Vol 84 (10) ◽  
pp. 23-28
Author(s):  
D. A. Golentsov ◽  
A. G. Gulin ◽  
Vladimir A. Likhter ◽  
K. E. Ulybyshev
Keyword(s):  
Experimental Data ◽  
Early Stage ◽  
Experimental Studies ◽  
Material Model ◽  
Total Charge ◽  
Cross Sectional ◽  
Practical Applications ◽  
Mechanical And Electrical Properties ◽  
Order Of Magnitude ◽  
Using Data

Destruction of bodies is accompanied by formation of both large and microscopic fragments. Numerous experiments on the rupture of different samples show that those fragments carry a positive electric charge. his phenomenon is of interest from the viewpoint of its potential application to contactless diagnostics of the early stage of destruction of the elements in various technical devices. However, the lack of understanding the nature of this phenomenon restricts the possibility of its practical applications. Experimental studies were carried out using an apparatus that allowed direct measurements of the total charge of the microparticles formed upon sample rupture and determination of their size and quantity. The results of rupture tests of duralumin and electrical steel showed that the size of microparticles is several tens of microns, the particle charge per particle is on the order of 10–14 C, and their amount can be estimated as the ratio of the cross-sectional area of the sample at the point of discontinuity to the square of the microparticle size. A model of charge formation on the microparticles is developed proceeding from the experimental data and current concept of the electron gas in metals. The model makes it possible to determine the charge of the microparticle using data on the particle size and mechanical and electrical properties of the material. Model estimates of the total charge of particles show order-of-magnitude agreement with the experimental data.

scholarly journals Kinetic Modeling and Degradation Study of Liquid Polysulfide Resin-Clay Nanocomposite

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 635
Author(s):  
Mohamadreza Shakiba ◽  
Arash Kakoei ◽  
Iman Jafari ◽  
Erfan Rezvani Ghomi ◽  
Mohammadreza Kalaee ◽  
...  
Keyword(s):  
Experimental Data ◽  
Kinetic Modeling ◽  
Degradation Kinetics ◽  
Nitrogen Atmosphere ◽  
Gravimetric Analysis ◽  
Degradation Kinetic ◽  
Kinetic Evaluation ◽  
Degradation Study ◽  
Clay Nanoparticles ◽  
Conversion Rates

Kinetic modeling and degradation study of liquid polysulfide (LPS)/clay nanocomposite is possible through Ozawa–Flynn–Wall (OFW) and Kissinger methods. Comparing the results of these models with experimental data leads to provide an accurate degradation kinetic evaluation of these materials. To this aim, the morphology and distribution of clay nanoparticles (CNPs) within the LPS matrix were investigated using Field Emission Scanning Electron Microscopy (FESEM) and X-ray diffraction (XRD). To evaluate the interaction between the LPS and the CNPs, the Fourier transform infrared (FTIR) identification was utilized. Furthermore, to investigate the kinetics of degradation, the thermal gravimetric analysis (TGA) and derivative thermogravimetry (DTG) of the samples were used in the nitrogen atmosphere with the help of Kissinger and Ozawa–Flynn–Wall (OFW) models. The characterization results confirmed the homogenous dispersion of the CNPs into the LPS matrix. In addition, the presence of CNPs increased the thermal stability and activation energy (Ea) of the samples at different conversion rates. Moreover, the OFW method was highly consistent with the experimental data and provided an appropriate fit for the degradation kinetics.

Nonlinear Wave Crest Distribution on a Vertical Breakwater

2018 ◽  
Author(s):  
Valentina Laface ◽  
Giovanni Malara ◽  
Felice Arena ◽  
Ioannis A. Kougioumtzoglou ◽  
Alessandra Romolo
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Vertical Wall ◽  
Surface Elevation ◽  
Wave Crest ◽  
Height Distribution ◽  
Free Surface Elevation ◽  
Pressure Transducers ◽  
Pressure Time ◽  
Time Histories

The paper addresses the problem of deriving the nonlinear, up to the second order, crest wave height probability distribution in front of a vertical wall under the assumption of finite spectral bandwidth, finite water depth and long-crested waves. The distribution is derived by relying on the Quasi-Deterministic representation of the free surface elevation in front of the vertical wall. The theoretical results are compared against experimental data obtained by utilizing a compressive sensing algorithm for reconstructing the free surface elevation in front of the wall. The reconstruction is pursued by starting from recorded wave pressure time histories obtained by utilizing a row of pressure transducers located at various levels. The comparison shows that there is an excellent agreement between the proposed distribution and the experimental data and confirm the deviation of the crest height distribution from the Rayleigh one.

scholarly journals Using Kinetic Modeling and Experimental Data to Evaluate Mechanisms in PET‐RAFT

2020 ◽  
Vol 58 (1) ◽  
pp. 139-144 ◽  
Author(s):  
Leah R. Kuhn ◽  
Michael L. Allegrezza ◽  
Nicholas J. Dougher ◽  
Dominik Konkolewicz
Keyword(s):  
Experimental Data ◽  
Kinetic Modeling

Dynamics of Evaporation and Cooling of a Water Droplet During the Early Stage of Depressurization

2009 ◽  
Author(s):  
L. Liu ◽  
Q. C. Bi ◽  
G. X. Wang
Keyword(s):  
Experimental Data ◽  
Water Droplet ◽  
Effective Conductivity ◽  
Numerical Study ◽  
Early Stage ◽  
Droplet Surface ◽  
Large Temperature ◽  
Measured Temperature ◽  
Equilibrium Evaporation ◽  
Electro Magnetic

This paper reports an experimental and numerical study of evaporation and cooling of a water droplet during the early stage of depressurization in a test vessel. During the experiment, a distilled water droplet was suspended on a thermocouple, which was also used to measure the droplet center temperature, and the droplet surface temperature was captured by an infrared thermograph. Experimental data indicated a large temperature difference within the droplet during the early stage of depressurization. A thermodynamic analysis of the experimental data found that the pressure reduction was not fast enough to induce liquid superheating and thus equilibrium evaporation was expected. A mathematical model was then constructed to simulate the droplet evaporation process. The model solves one-dimensional heat conduction equation for the temperature distribution inside the water droplet, with the convective heat transfer inside the droplet simplified through an effective conductivity factor. A simplified treatment was introduced to quantify the convective evaporation due to air movement and droplet swing induced by sudden opening of the electro-magnetic valve and the following air exiting. The model-predictions agree well with the measured temperature data, demonstrating the soundness of the present model.

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