Propane-air Mixtures Research Articles

Effects of Hydrogen and Nitrogen Concentration on Laminar Burning Velocities and NO, CO Formation of Propane-Air Mixtures

With the development of the uses of hydrocarbon compounds in many industrial fields, especially in the field of energy liberation through oxidation of gases, as previous research specialized in improving the combustion processes of gases by adding particles of other gases that contribute to improving the combustion of these compounds in terms of temperatures and speed of flame combustion. The previous study aimed to improve the flame speed by adding different gases to several compounds. In this research paper, propane gas C3H8 is used as the main gas to improve its combustion properties. N2 and H2 gas were added in different proportions, through which a clear effect on the combustion properties can be seen in terms of combustion speed. Flames and exhaust as CO and NOx. As the auxiliary gases were added in this improvement at rates of 20%, 30% and 40%, and then these tests were analyzed, where it was concluded that H2 gas clearly contributed to improving the combustion speed of the flame, as the flame combustion velocity reached 58.3 cm/s by 40%.

Properties of coatings obtained by electric arc spraing for renovation of parts of machines and vehicle mechanisms

The robots present the results of investigating the power of coatings, excluding electric arc (EAS) filings, and their comparison with the powers of coatings, excluding gas-flame filings. The porosity of the coating, taken from electric arc filings, was in the range of 8-10%. the adhesion strength was 80…100 MPa. The results of the investigations show the advantages and purpose of using electric arc sawing to improve and move the capacity of machine parts and transport mechanisms. In the work, the following factors are added to the process of electric arc sawing: storage of fuel sum, distance of sawing, dispersion of sawing and other. on authority cover. In the course of the investigation, the increase in resistance, adhesive strength, coating thickness, the term for the coating thickness, was determined by the parameters of the electric arc filing. The robots have considered the possibility of securing the necessary authorities influencing the surface with the method of advancing the resource of machine parts by way of regulation by the factors of EAS. Regulating the smoothness and temperature of the stream of transporting gas and particles, you can change the diameter of the droplet, increase the width and reduce the oxidation of the coating. The results of comparative analysis of the properties of coatings applied by electric arc spraying (EAS) using the products of combustion of propane-air mixture and gas-flame spraying (FSP) using gas-air mixture are presented. Under optimal conditions of the spraying process, the porosity of the coatings obtained by electric arc spraying is much lower compared to gas-flame spraying: 8-10% and 20-30%, respectively. Adhesion strength of coatings obtained by electric arc spraying increased by 1.8-2.2 times (from 30-40 MPa in gas-flame spraying to 100 MPa in electric arc), wear resistance increased by 2-2yu5 times.

Study of Critical Conditions of Spark Ignition and Burning Rate of a Boron Powder Suspension in a Propane–Air Mixture

Study of Critical Conditions of Spark Ignition and Burning Rate of a Boron Powder Suspension in a Propane–Air Mixture

Flame kernel development with radiofrequency oscillating plasma ignition

In this paper a radiofrequency oscillating plasma discharge is investigated under various initial pressures up to 5 atm in a constant-volume combustion chamber. The oscillating plasma is suppressed by elevated pressure, both in length and branch number. The ignition performance under elevated background pressure is investigated, and the results are compared with spark events with a similar ignition energy. Under ambient conditions, the oscillating plasma discharge generates multiple streamers that are much longer than a spark gap, resulting in a much bigger initial flame kernel. Under elevated background pressures, fewer streamers with much smaller sizes are observed, thus the advantage of an oscillating plasma discharge over a spark discharge is compromised. Prolonged duration of an oscillating plasma discharge consistently demonstrates a positive impact on flame propagation speed, but neither prolonged duration nor enhanced discharge current has a noticeable impact on flame kernel growth for the spark ignition cases. Both oscillating plasma and spark are used to treat non-combustible propane–air mixtures under background pressures from 1 to 5 atm.

Gas explosion venting of 20-litre vessel with and without various length of vent ducts

When gas explosion occurs in closed vessel, venting devices can reduce the pressure inside the protected equipment, and vent ducts can be used to direct burnt and unburnt mixtures. In this paper, some ductless and duct vented explosion measurements were performed in a standard 20-liter explosion chamber with 2.8 to 6.3 vol.% propane-air mixture at atmospheric pressure (1 barg) and ambient temperature (298 K). Experimental investigations were performed with different lengths of vent duct (0 meter, 0.15 meter, 1 meter). During the measurements, effects of vent ducts to the venting process had been studied. Aluminium foils were used as rupture disks with 30 mm diameter circular venting area. During each measurement, static activation overpressure of aluminium foil, maximum explosion overpressure of propane-air mixture, the gas deflagration index in case of the vented vessel, and the pressure drop along the 1 meter length duct were determined.

Study of Critical Conditions of Spark Ignition and Burning Rate of Boron Powder Particles in a Propane-Air Mixture

Study of Critical Conditions of Spark Ignition and Burning Rate of Boron Powder Particles in a Propane-Air Mixture

The gaseous hydrocarbon fuel combustion process diagnostics using laser-spark emission spectrometry

To solve the gaseous hydrocarbon fuel combustion process control and diagnostics problem, it is proposed to apply the laser-spark emission spectrometry methods. In propane-air mixture combustion, three modes are investigated: stoichiometric combustion, an enriched mixture, and a lean mixture. A laboratory stand has been developed to study combustion processes by laser-spark emission spectrometry. The plasma radiation spectral characteristics an experimental study results formed in a flame when exposed to laser radiation are presented.

Explosion-Suppression Characteristics of Nonmetallic Spherical Spacers on Propane-Air Mixtures in Confined Space

The explosion-suppression effects of NSSs on overpressures, flame propagation and flame tip velocities were explored under the initial pressures of 0.2 MPa, 0.3 MPa and 0.4 MPa. All experiments tested in a constant volume combustion bomb (CVCB). Explosion reaction of premixed propane–air gas in a new designed CVCB filled with nonmetallic spherical spacers (NSSs) was analyzed. The results showed that overpressures decreased under the different initial pressures. With the increase of filling density, the overpressure decreased, the time to reach explosion overpressure decreased, and the decay rate of explosion overpressure increased. It was also found that the explosion-suppression effects of NSSs on pressures. Flame front could be captured by high-speed schlieren photography. Combustion phenomena were captured including flame propagation, corrugated laminar flame, jet flame, corrugated turbulent flame as well as tulip flame under different initial pressures. Flame tip velocities also were captured. The results demonstrate that flame tip velocities decreased with the increase of filling densities. However, compared with unfilled CVCB, flame tip velocities increased after filling NSSs in CVCB under different initial pressures. NSSs suppressed the explosion overpressure in the cylinder, and promoted the flame propagation. In both cases, NSSs played a dual role. The suppression effect of NSSs was affected by both its suppression and promotion effect on the explosion. This work provides a scientific basis for the effective prevention of explosion accidents with propane–air premixtures and the development of explosion-suppression products.

Numerical determination of the combustion rate of a gas suspension of coal dust in a propane-air mixture

The results of the numerical solution of the problem of the combustion rate of a coal-propane-air mixture are presented. The physical and mathematical formulation of the problem is based on the approaches of the dynamics of multiphase reacting media. The method for solving the problem is based on the algorithm for the decay of an arbitrary discontinuity. The dependences of the visible and normal combustion rate of the coal-propane-air mixture on the radius and the volumetric content of propane in the gas are obtained.

Long gap spark discharge ignition using a boron-doped diamond electrode

A long gap discharge offers an efficient method for achieving stable ignition in lean fuel/air mixtures, because it can reduce the heat loss to the electrodes, achieve efficient electrical energy transfer from the ignition coil to the discharge plasma, and reduce the initial flame curvature by converting the geometry of the ignition from a point to a line. However, the formation of such discharge requires increased discharge voltage to compensate for the reduction in the electric field between the electrodes, and this is not easily achieved in practice. Since the Townsend discharge criteria depend not only on the electron multiplication coefficient (α coefficient) but on the secondary electron emission (γ-process), we focused on the latter to reduce the discharge threshold voltage. In the present study, for the first time, B-doped diamond (BDD), which has a larger secondary electron emission coefficient than the metals used in conventional spark discharge ignition, was utilized as the cathode material, and its discharge and ignition characteristics were investigated. Under the same conditions, use of a BDD cathode resulted in a lower discharge threshold, greater discharge energy, less discharge energy variation, and more rapid flame development, than in the case of a metal cathode. The influence of the cathode material on discharge threshold suggests that the breakdown mechanism of ignition-coil spark discharge is based on Townsend discharge. To elucidate the effect of gap length, the temporal development of flame growth, using the same discharge energy in methane and propane mixtures, was compared between ignition with a short gap discharge with a metal cathode and long gap discharge with a BDD cathode. With a long gap discharge, only the flame growth of lean propane-air mixtures was accelerated, while no difference was observed in the case of lean methane or relatively rich propane mixtures, suggesting the effectiveness of long gap discharge ignition for mixtures with a large Lewis number, due to the small curvature of the initial flame kernel.

A CFD study of ignition of lean propane-air mixtures in a heat recirculating U-bend catalytic microreactor

Heat recirculating (HR) geometries have been studied in the literature for their use in energy generation applications. This work investigates the ignition and cold-start behavior of lean propane-air combustion in a U-bend catalytic microreactor through computational fluid dynamics (CFD) study. Although several studies have focused on stability and combustion behavior, the role of heat recirculation on catalytic and homogeneous ignition from the cold-start conditions has not been analyzed so far. The U-bend microreactor is a typical example of HR geometry, where the hot exhaust gases in the recirculation channel transfer heat to the cold incoming fluid. Significance of heat recirculation across the dividing wall on the ignition temperature, as well as transient evolution of temperature, propane conversion and reaction are presented. Ignition temperature is found to be 20K lower in the U-bend microreactor than straight channel microreactor. However, transient ignition study revealed that at nominal conditions, U-bend microreactor takes about 35s longer than straight channel for ignition and to reach steady state, owing to heat distribution internally within the U-bend microreactor. The effect of flowrate is analyzed, which shows that at higher flowrates, the ignition and steady-state times are also lower for the U-bend microreactor. Finally, the effect of solid wall material is investigated, which shows that lower conductivity material (such as ceramic) showed faster ignition with low thermal inputs.

A hybrid BML-fractal approach for the mean reaction rate modelling of accidental gas explosions in partially confined obstructed geometries

We propose a new approach to model the mean reaction rate of premixed turbulent flames when simulating accidental gas explosions with computational fluid dynamics (CFD). The combination between Bray–Moss–Libby (BML) approach and the fractal concept was evaluated. The fractal concept is used for closing the integral length scale of wrinkling in the BML formulation replacing the utilisation of empirical functions. The proposed expression accounts for the effect of local length scales of turbulence on the flame front via the fractal outer and inner cut-offs, which were taken respectively as the integral length scale of turbulence and the Gibson length scale. The initial laminar phase of flame propagation is described by a laminar combustion model and the onset of the transition from the laminar to turbulent combustion is assumed to take place at a threshold value of the turbulent Reynolds number. The approach is implemented and evaluated within an in-house developed code called STOKES (Shock Towards Kinetic Explosion Simulator) that solves the full set of Navier–Stokes equations. The equations are parameterised according to the porosity distributed resistance (PDR) method in which the porous mesh accounts for the presence of small obstacles that are responsible for turbulence generation during an explosion. Simulations are carried out for vented explosions of both methane–air and propane–air mixtures in partially obstructed chambers. Results are compared with experimental data, FLACS simulations and a typical model for the length of wrinkling which uses an empirical function instead of the fractal approach. Comparisons lead to overall good agreement, indicating that the proposed model can be used in numerical simulations of accidental explosions to support consequence modelling in the framework of risk analysis.

Propagation Velocity of Flames in Inert-Diluted Stoichiometric Propane-Air Mixtures: Pressure and Temperature Dependence

The flammable propane–air mixtures raise specific safety and environmental issues in the industry, storage, handling and transportation; therefore dilution of such mixtures has gained significant importance from the viewpoint of fire safety, but also due to nitrogen oxide’s emission control through flameless/mild combustion. In this paper, the propagation of the flame in C3H8-air-diluent stoichiometric gaseous mixtures using Ar, N2 and CO2 as diluents was investigated. Data were collected from dynamic pressure-time records in spherical propagating explosions, centrally ignited. The experiments were done on stoichiometric C3H8-air + 10% diluent mixtures, at initial pressures within 0.5–2.0 bar and initial temperatures within 300–423 K. The flame velocity was determined from laminar burning velocities obtained using the pressure increase in the incipient stage of flame propagation (when the pressure increase is lower than the initial pressure). The experimental propagation velocities were compared with computed ones obtained from laminar burning velocities delivered by kinetic modeling made using the GRI mechanism (version 3.0) with 1D COSILAB package. The thermal and baric coefficients of propagation velocity variation against the initial temperature and pressure are reported and discussed.

Propane-air mixture deflagration hazard with different ignition positions and restraints in large-scale venting chamber

In order to better assess the hazards of explosion accidents, propane-air mixture deflagrations were conducted in a large-scale straight rectangular chamber (with a cross-section of 1.5 m × 1.5 m, length of 10 m, and total volume of 22.5 m3). The effect of initial volume, ignition position, and initial restraints on the explosion characteristics of the propane-air mixtures was investigated. The explosion overpressure, flame propagation, and flame speed were obtained and the computational fluid dynamics (CFD) software was used to simulate the flame-propagation process and field flow for auxiliary analysis. The hazards of large-scale propagation explosion under weak and strong constraints were evaluated and the different phases of flame propagation under weak and strong constraints were discriminated. Results indicate that the hazards caused by propane deflagration under weak constraint are mainly caused by flame spread. And the maximum overpressure under strong constraint appeared at the front part of the chamber under the large-scale condition, which is consistent with the previous small-scale test. Moreover, the simulations of flame structures under weak and strong constraint are in good agreement with experimental results, which furthers the understanding of large-scale propane deflagration under different initial conditions in large-scale spaces and provides basic data for three-dimensional CFD model improvement.

Liftoff height of turbulent diffusion flame in water-mist-laden coflowing air stream

In the present study, the enhancement of the liftoff and blowout of a propane/air coflowing diffusion flame by water mist was experimentally investigated in the subsonic range. When the fuel injection velocity Uf is low, an attached laminar diffusion flame is stabilized at the burner rim with a premixed flame base. An increase of Uf leads to the liftoff of the attached flame, and eventually to the blowout of the lifted flame. The upstream laminar flame disappears at the liftoff and a turbulent lifted flame is stabilized in the downstream region. The stability of the lifted flame deteriorates with the increase of the coflowing air velocity Ua and the water mist flow rate Qm. The stable lifted flame can be achieved by the dynamic balance of the local mean gas velocity Ug¯ and the mean turbulent flame propagation speed Up¯ of the premixed flame formed at base of the lifted flame, and Up¯ was estimated by the measurements of Ug¯ by a laser Doppler velocimeter. Up¯ decreases with Qm and is of the order of 1 m/s at the blowout independently of Ua and the mass fraction of water mist Y0. This value is nearly equal to 2.5SL0, where SL0 is the adiabatic laminar flame speed of a stoichiometric propane-air mixture. The liftoff height L increases both with Uf and Qm. For the case without water mist, a unique correlation has been proposed in the previous studies between L and Uf in a non-dimensional form using SL0. By extending this correlation to the diffusion flame in the water-mist-laden air stream, the laminar flame speed influenced by water mist was appraised and compared with the simulation previously reported. Resulting flame speed reduction is 65% of that predicted by numerical simulation, presumably due to the partial evaporation of water mist.

The phenomenon of negative temperature coefficient in palladium-initiated combustion of hydrogen–propane–air mixtures

During the combustion of hydrogen (70–40%) + propane (30–60%) + air mixtures over palladium at a total pressure of 1–2 atm, Pd is consumed in the chemical etching reaction with active combustion intermediates. This behaviour of palladium limits its applicability in ignition devices.

Ignition of a Propane-Air Mixture for a Reflected Shock Wave at High Pressures

Ignition of a Propane-Air Mixture for a Reflected Shock Wave at High Pressures

Experimental investigation of flame stability in the premixed propane-air combustion in two-section porous media burner

The characteristics of combustion and the flame stabilization within a two-layer porous media burner were investigated experimentally in the present study. Lean propane-air mixtures were used with the equivalence ratio values ϕ in the range between 0.1 and 0.5 and the flow rate Q of the mixture in the range between 10 and 45 l/min. It was experimented with three porous ceramics: reticulated foam alumina, honeycomb foam alumina and SiC foam. The axial temperature distribution, reaction zone, maximum temperature, CO and NOx emissions, and combustion wave propagation rate were analyzed. The experimental results showed that, in the three ceramics studied, the combustion wave propagation rate increases with increased inlet velocity and decreased equivalence ratio of premixed gases. Result of the analysis of the information obtained, a porous burner with flame stabilized between two porous ceramics was built that works permanently with the equivalence ratio ϕ = 0.5 and the flow rate of the mixture in the range between 20 and 35 l/min. The honeycomb foam was placed on top of the burner and the reticulated foam on the bottom. The combustion temperatures were in the range between 1160 and 1380 K, where a higher flow rate resulted in higher temperatures. The CO and NOX emissions did not exceed a few ppm showing that combustion was almost complete.

ОСОБЕННОСТИ РАСПРОСТРАНЕНИЯ ПЛАМЕНИ В УГЛЕ-ПРОПАНО-ВОЗДУШНОЙ ГАЗОВЗВЕСИ

The mathematical model of combustion for a reactive gas suspension of coal dust in a propane-air mixture is developed. The parametric study of the problem is carried out. The observed burning velocity of the propane-air mixture with an admixture of coal particles is determined. Dependences of the observed burning velocity of the propane-air gas suspension on the equivalence ratio and on the radius of the particles are obtained. It is shown that, the observed burning velocity decreases with an increase in the radius of the particles. On the contrary, with an increase in the radius of the particle, the observed burning velocity increases for high-propane mixtures. Moreover, in the case of high-propane mixtures, the observed burning velocity of the gas suspension can be increased by reducing the mass of the particles. The observed burning velocity for a propane-air mixture with particles is significantly less than that for a mixture without particles.

Ignition of Propane-Air Mixtures in Shock Tube at Pressure of 30 atm

Ignition of Propane-Air Mixtures in Shock Tube at Pressure of 30 atm