Digital Image Processing based Fire Flame Color and Oscillation Frequency Analysis

The flickering characteristics of a non-premixed flame interacting with von Kármán vortex street on a bluff-body burner were investigated experimentally with varied velocities of the central fuel jet and annular air stream. Flow visualization in terms of a shadowgraph, planar laser-induced fluorescence of hydroxyl, and Mie scattering, which was obtained via PIV used to analyze the flow field, indicated that the flame flickering was caused by periodically growing, toroidal vortices outside the flame surface that were much larger than those observed in buoyant jet flames. In contrast to a weak dependence of the latter on the co-flowing air velocity and the central fuel velocity, the present case was strongly correlated with the von Kármán vortex street shed from the rim of the air stream that produced vortex pairing downstream, and was coupled with buoyancy effects rendered by the pilot flame in the recirculation zone as well as the central jet flame. The flame surface was consequently wrinkled substantially by the strong flame-vortex interaction, leading to frequent local extinction. Furthermore, due to a significant extension of the residence period, the frequency of oscillation was greatly decreased when the velocity of air flow was large enough to introduce a recirculating flame behind the bluff body. It was then increased when the air velocity increased. In contrast, a maximal frequency of oscillation was generated when the fuel velocity was increased, which occurred as the flame mode altered from a recirculation zone flame to a jet-dominated flame, for which the central jet flame was about to penetrate the recirculation zone. This frequency was caused by the intense interactions among the recirculated air, the central jet flame, and small eddies convened around the dome of the recirculation zone. The global behaviors of flame flickers could be further summarized using the Strouhal number and the Reynolds number of fuel jet in a relation of (St)(Re c ) = C, whereas the constant C was modified by the Reynolds number of air flow.

Laminar jet methane/air diffusion flame shapes and radiation of low air velocity coflow in microgravity

Experimental study of diffusion flame oscillations and empirical correlations

The influence of swirl on oscillations in ducted premixed flames

Investigation of visible light emission from hydrogen-air research flames

Fast fire flame detection in surveillance video using logistic regression and temporal smoothing

Candlenut biodiesel meets the characteristics of biodiesel standards that have been determined according to the criteria of Indonesia's national standard parameters (SNI) such as density, viscosity, Cetane number, flash point, and fog point. The premixed combustion test on candlenut biodiesel oil aims to determine the characteristics of biodiesel and the characteristics of the combustion fire. The examination was carried out by comparing the characteristics of pure biodiesel fire (B100), pure candlenut biodiesel (B0), with a mixture of 10% (B10), 20% (B20), 30% (B30) and the equivalent variation of ratio (ϕ) 1.5 , (ϕ) 1 and (ϕ) 0.5. This examination aims to analyze the effect of mixing on the resulting fire characteristics, including the flame color, the height of the flame cone, and the temperature of the flame. The examination and measurements of the flame temperature showed a decrease in flame temperature on each addition of candlenut biodiesel from each variation. In the results of the measurement of flame color with variations ϕ = 1 and ϕ = 0.5, there is a decrease in the percentage of blue flame in each addition of candlenut biodiesel. In the results of fire cone measurements with variations ϕ = 1.5, ϕ = 1 and ϕ = 0.5, there is a decrease in the height of the fire cone in each addition of 30% pecan oil biodiesel. The decrease in each flame characteristic was caused by the effect of adding candlenut biodiesel oil, which resulted in increasing fuel density so that the fuel was difficult to burn and reduced the result characteristics of the flame.

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A flame exhibits a limit-cycle oscillation, which is called "flame flickering" or "puffing," in a certain condition. We investigated the bifurcation structure of the flame oscillation in both simulation and experiment. We performed a two-dimensional hydrodynamic simulation by employing the flame sheet model. We reproduced the flame oscillation and investigated the parameter dependencies of the amplitude and frequency on the fuel-inlet diameter. We also constructed an experimental system, in which we could finely vary the fuel-inlet diameter, and we investigated the diameter-dependencies of the amplitude and frequency. In our simulation, we observed the hysteresis and bistability of the stationary and oscillatory states. In our experiments, we observed the switching between the stationary and oscillatory states. As fluctuations can induce the switching in the bistable system, switching observed in our experiments suggested the bistability of the two states. Therefore, we concluded that the oscillatory state appeared from the stationary state through the subcritical Andronov-Hopf bifurcation in both the simulation and experiment. The amplitude was increased and the frequency was decreased as the fuel-inlet diameter was increased. In addition, we visualized the vortex structure in our simulation and discussed the effect of the vortex on the flame dynamics.

Flame characteristics when a non-premixed n-butane jet is ejected into a coaxial cylindrical tube are investigated experimentally. Flame stability depends mainly on the characteristics of flame propagation as well as air entrainment which depend on the jet momentum and on the distance between the nozzle exit and the base of a confined tube. As flow rate increases, the flame lifts off from a nozzle attached diffusion flame and a stationary lifted flame can be stabilized. The liftoff height increases nearly linearly with the average velocity at the nozzle exit. The lifted flame has a tribrachial flame structure, which consists of a rich premixed flame, a lean premixed flame, and a diffusion flame, all extending from a single location. As flow rate further increases, periodically oscillating flames are observed inside the confined tube. Once flame oscillation occurs, the flame undergoes relatively stable oscillation such that it has nearly constant oscillation amplitude and frequency. The criteria of flame oscillation are mapped as functions of nozzle diameter, the distance between nozzle and tube, and jet velocity. This type of flame oscillation can be characterized by Strouhal number in terms of flame oscillation amplitude, frequency, and jet velocity. Buoyancy driven flame oscillation which is one of the viable mechanism for flame oscillation is modeled and the results agrees qualitatively with experimental results, suggesting that the oscillation is due to periodic blowoff and flashback under the influence of buoyancy.

PURPOSE: A method for sensing a fire frame using a fuzzy logic is provided to shorten time for sensing a fire flame. CONSTITUTION: A control module receives image information and divides the image information into a plurality of blocks(200). The control module detects a moved block by determining whether each block moves(202). The control module detects a block with a fire flame color based on the color information of each moved block if the moved block is detected(204). If the block with a fire flame color is detected, a fire flame is finally determined by verifying a fire flame color using a fuzzy logic.

A computational study of oscillatory extinction of spherical diffusion flames

A lattice Boltzmann algorithm for calculation of the laminar jet diffusion flame

Effects of fuel type and equivalence ratios on the flickering of triple flames

Experiments were performed on the central pilot body (RPL-rich-pilot-lean) of Siemens prototype 4th generation DLE burner to investigate the flame behavior at atmospheric pressure condition when varying equivalence ratio, residence time and co-flow temperature. The flame at the RPL burner exit was investigated applying OH planar laser-induced fluorescence (PLIF) and high-speed chemiluminescence imaging. The results from chemiluminescence imaging and OH PLIF show that the size and shape of the flame are clearly affected by the variation in operating conditions. For both preheated and non-preheated co-flow cases, at lean equivalence ratios combustion starts early inside the burner and primary combustion comes to near completion inside the burner if residence time permits. For rich conditions, the unburnt fuel escapes out through the burner exit along with primary combustion products and combustion subsequently restarts downstream the burner at leaner condition and in a diffuse-like manner. For preheated co-flow, most of the operating conditions yield similar OH PLIF distributions and the flame is stabilizing at approximately the same spatial positions. It reveals the importance of the preheating co-flow for flame stabilization. Flame instabilities were observed and Proper Orthogonal Decomposition (POD) is applied to time resolved chemiluminescence data to demonstrate how the flame is oscillating. Preheating has strong influence on the oscillation frequency. Additionally, combustion emissions were analyzed to observe the effect on NOX level for variation in operating conditions.