Pool Diameter Research Articles

An experimental and non-dimensional study on the vertical temperature distribution of a sealed ship engine room fire

Fire in a sealed ship engine room is different from open fires, while its suppression is critically important to the emergency rescue and structure safety for a ship. This study focused on the vertical distribution of temperature rise during a sealed engine room fire. A series of experiments were carried out to investigate fire behaviors in a reduced-scale sealed ship engine room with a dimension of 3 m (length) × 3 m (width) × 3.5 m (height). The results suggested that there are vertical temperature gradients of smoke layer, showing a little lower than those of open fires. The experimental results demonstrated that the time to reach the maximum temperature is different for smoke layers at various heights, while a lower height showed a relatively long delay time. The vertical gradient of temperature rise was found increasing with pool diameter where the gradient of temperature rise of a 30 cm pool fire is about 9 times of that of a 10 cm pool fire. Furthermore, an empirical model was developed to predict the vertical temperature rise distribution along the height at the time of the maximum temperature for sealed engine room fires.

Experimental Procedure for Laboratory Studies of In Situ Burning : Flammability and Burning Efficiency of Crude Oil.

A new method for the simultaneous study of the flammability and burning efficiency of fresh and weathered crude oil through two experimental laboratory setups is presented. The experiments are easily repeatable compared to operational scale experiments (pool diameter ≥2 m), while still featuring quite realistic in situ burning conditions of crude oil on water. Experimental conditions include a flowing water sub-layer that cools the oil slick and an external heat flux (up to 50 kW/m2) that simulates the higher heat feedback to the fuel surface in operational scale crude oil pool fires. These conditions enable a controlled laboratory study of the burning efficiency of crude oil pool fires that are equivalent to operational scale experiments. The method also provides quantitative data on the requirements for igniting crude oils in terms of the critical heat flux, ignition delay time as a function of the incident heat flux, the surface temperature upon ignition, and the thermal inertia. This type of data can be used to determine the required strength and duration of an ignition source to ignite a certain type of fresh or weathered crude oil. The main limitation of the method is that the cooling effect of the flowing water sub-layer on the burning crude oil as a function of the external heat flux has not been fully quantified. Experimental results clearly showed that the flowing water sub-layer does improve how representative this setup is of in situ burning conditions, but to what extent this representation is accurate is currently uncertain. The method nevertheless features the most realistic in situ burning laboratory conditions currently available for simultaneously studying the flammability and burning efficiency of crude oil on water.

Experimental Procedure for Laboratory Studies of <em>In Situ</em> Burning : Flammability and Burning Efficiency of Crude Oil

A new method for the simultaneous study of the flammability and burning efficiency of fresh and weathered crude oil through two experimental laboratory setups is presented. The experiments are easily repeatable compared to operational scale experiments (pool diameter ≥2 m), while still featuring quite realistic in situ burning conditions of crude oil on water. Experimental conditions include a flowing water sub-layer that cools the oil slick and an external heat flux (up to 50 kW/m2) that simulates the higher heat feedback to the fuel surface in operational scale crude oil pool fires. These conditions enable a controlled laboratory study of the burning efficiency of crude oil pool fires that are equivalent to operational scale experiments. The method also provides quantitative data on the requirements for igniting crude oils in terms of the critical heat flux, ignition delay time as a function of the incident heat flux, the surface temperature upon ignition, and the thermal inertia. This type of data can be used to determine the required strength and duration of an ignition source to ignite a certain type of fresh or weathered crude oil. The main limitation of the method is that the cooling effect of the flowing water sub-layer on the burning crude oil as a function of the external heat flux has not been fully quantified. Experimental results clearly showed that the flowing water sub-layer does improve how representative this setup is of in situ burning conditions, but to what extent this representation is accurate is currently uncertain. The method nevertheless features the most realistic in situ burning laboratory conditions currently available for simultaneously studying the flammability and burning efficiency of crude oil on water.

On the critical conditions for pool-fire puffing

Pool fires are known to undergo a bifurcation to a globally unstable puffing state driven by baroclinic and buoyant vorticity production. Although the supercritical puffing regime away from the bifurcation has been studied extensively in the literature, no detailed account has been given of the critical conditions for its onset, that being the purpose of the present paper. For the relevant canonical case of round liquid pools without swirl, aside from the inherent thermochemical and transport parameters associated with the fuel, pool-fire puffing is governed by a single dimensionless number, the Rayleigh number, which scales with the cube of the pool diameter. Consequently, for a fixed fuel and under fixed ambient conditions, there is a critical fuel pool diameter, associated with a critical value of the Rayleigh number, above which the flame starts puffing. A global linear stability analysis that accounts for the axisymmetry of the prevailing instability mode is developed here to describe the bifurcation. The mathematical formulation employs the limit of infinitely fast reaction, with account taken of the nonunity Lewis number and vaporization characteristics of typical liquid fuels. Predictions of critical puffing conditions, including critical diameters and puffing frequencies, are provided for methanol and for heptane pool fires, and the results are compared with results of new small-scale experiments under controlled laboratory conditions, reported here, yielding reasonably good agreement.

The oscillation of stationary weld pool surface in the GTA welding

A three-dimensional transient numerical model of a pulsed GTA welding is established based on the volume of fluid (VOF) method to study the oscillation of stationary weld pool surface. The detecting and sensing method based laser vision is used to measure the oscillation frequency in the weld pool. In conjunction with the theory, the oscillation frequency during welding process is analyzed. The free surface oscillation was investigated when the current changes from peak to base and when the weld pool was fully penetrated. Before full penetration, the weld pool oscillation frequency decreases as the welding time increases. The penetration depth increases with the welding time. When the molten pool reaches full penetration, the oscillation frequency stays the same. With the state of weld pool changes from partial penetration to full penetration, the oscillation frequency decreases rapidly. When the current changes from peak to base or from base to peak, the damping vibration takes place in a higher frequency. When the pool diameter is greater than 8.4 mm, the base metal fully penetrated.

An experimental investigation of the flame height and air entrainment of ring pool fire

A serial of experiments have been conducted to investigate the flame height and air entrainment rate of the ring pool fire. The outside diameters of ring pool fires are 15 cm, 20 cm, 25 cm, 35 cm, 45 cm and 55 cm, respectively. The difference between the inner diameter and the outer diameter is 10 cm for each pool. It was found that the flame height of ethanol changes slightly with the increasing equivalent pool diameter, while the ones of n-heptane increases obviously. A unified correlation considering the air entrainment has been developed for both two fuels, and the measurement collapsed well with the physical model.

On the Analysis of Flame Pulsation and Fire Induced Vent Flow Oscillatory Behaviors in Confined Enclosures with Horizontal Openings

Abstract This paper undertakes a comprehensive analysis of flame pulsation behavior and vent flow oscillatory behavior in a confined enclosure. Experiments are carried out in a small scale confined compartment with a horizontal opening, and several configurations characterized by different pool diameters and ceiling vent sizes are considered. Flame pulsation and horizontal vent flow oscillatory behaviors are investigated during the experiments, and visualization recordings were collected. Results indicate that the flame pulsation frequency ( f fire ) can be obtained by way of the Fast Fourier Transform (FFT) method (with recorded RGB images being transformed into pseudo-gray images based on Ostu’s method) and the vent flow oscillatory frequency ( f vent ) can also be obtained using a similar processing method. The frequencies are found to vary in accordance with variation of the horizontal opening size. Through theoretical analysis, the relationship between the flame pulsation frequency and vent flow oscillatory frequency is investigated. Moreover, it is expected that the comprehensive frequency term would alter in alignment with the parameters of the horizontal opening, and this sufficiently fitted with the experimental data.

Measurement of geometric and radiative properties of heptane pool fires

The objective of the present work is to characterize heptane pool fires for pool diameters ranging from 0.1 m to 1.0 m, in a quiescent environment. Characterization of pool fires is done by determining various parameters such as the mass burning rate, puffing frequency, flame height, optical thickness, spatial distribution of emissivity and temperature, irradiance and fire safety distance. Measurement of the instantaneous mass burning rate indicates the presence of two steady states: an initial steady state and a bulk boiling steady state. The mass burning rate is found to decrease with increase in the free board height. Flame height is determined based on the definition of intermittency. Puffing frequency is obtained from the visible images by tracking the vortical structures in flames. The obtained results for the flame height and puffing frequency match well with the correlations presented in the literature.Flame emissivity is determined from the mass burning rate as well as a refined technique that determines the transmissivity of the electrically heated strips placed behind the flame. Radiative properties such as temperature distribution and irradiance at a distance are calculated from the thermal images. The irradiance at a distance obtained using the infrared camera is compared with Schimdt-Boelter gauge. The effect of fire size on the optical thickness, radiative fraction and fire safety distance has been examined.

Experimental study of the flame geometrical characteristics of the crude oil boilover fire under cross air flow

This paper presents an experimental investigation of the flame geometrical characteristics of the crude oil boilover fire under cross air flows. Circular crude oil boilover fire are burned under the horizontal cross air flows ranged in 0–1.5 m/s. The flame geometrical characteristics are recorded by a CCD (Charge-Coupled Device) digital camera. Results indicate that the crude oil boilover fire under cross air flow can be divided as initial growth stage, steady stage, boilover stage and decay stage. The average flame length in the both steady stage and boilover stage decreases with the increasing cross air flow speed when the speed (u) is less than 1.0 m/s and then increases. Furthermore, the initial fuel layer thickness (h0) has a stronger influence on the average flame length in the boilover stage. The flame tilt angle increases fast when u rose from 0 to 1.0 m/s and then increases slowly. The tilt angle decreases with the pool diameter but weakly influenced by h0. A new correlation equation based on the Richardson number is introduced to predict the flame tilt angle, which collapses the tangent value of the flame tilt angle well.

Use of immersed conductive objects to enhance the burning rate of hydrocarbon pool fires

This study investigates the ability of thermally conductive nonflammable objects to enhance the steady state burning rate of hydrocarbon pool fires with the ultimate goal of designing a burner for faster clean-up of hazardous spills in offshore and other remote environments. In the initial set of small-scale experiments, a vertical 1cm diameter solid aluminum cylinder with varying lengths is placed centrally in a 10cm diameter pan fed with a continuous supply of hexane burning in quasi-steady state. The upper part of the cylinder, engulfed in the flame, heats up, and conducts heat to the lower submersed part, that transmits heat to the liquid below the pool surface. Tests reveal that the submersed lower part of the cylinder heats up sufficiently to sustain nucleate boiling, significantly increasing the burning rate, when compared to the baseline pool fire, where vaporization is achieved solely by radiative and convective heat transfer at the pool surface. The effects of cylinder length and multiple cylinders on burning rate are also characterized. To determine if the concept can also be applied to oil spill clean-up, a set of large scale tests is performed by burning crude oil/water mixtures in a 1-meter diameter pool. These tests show that burners with thermally conductive cylinders can be designed to effectively dispose of crude oil and oil/water mixtures.

Experimental Study of Combustion Characteristics of Circular Ring Thin-Layer Pool Fire

For clarifying the combustion behavior of circular ring thin-layer pool fire, a series of experiments with varying pool diameters were carried out. The equivalent pool area of 0.071 m^2 and an initial n-heptane thickness of 10 mm were fixed. Electronic balance, digital camera and K-type thermocouples were used respectively to measure burning rate, flame height as well as centerline temperature. The results show that more burning stages can appear with the increase of the inner and outer diameters of circular ring pool. Fire merging can occur at any one of initial growth, quasi-steady burning with surface boiling, transition to bulk boiling and bulk boiling burning stages, and moreover the maximum burning rate of fire merging is about 3.5 times the one of the ordinary pool fire with same area. The core hollow region plays an important effect in decreasing the burning rate, flame height and fire merging time etc. The evolutions of the characteristic parameters e.g. burning rate, flame height and centerline ...

Design of 120t converter furnace body

At present, the oxygen converter steelmaking equipment of large-scale, production of continuous and high-speed, which has achieved a high productivity, and this requires matching equipment to complete together. The process about the layout of these equipment and the workshop of various materials must be reasonable in order to enable the production to proceed smoothly. The furnace body for 120t converter is designed in the paper. The results are as follows. The converter raw data has been used, the experimental step of the design has been listed to determine the data required for the furnace size design, including the steel yield, scrap ratio, furnace type, etc. The size of the data has been obtained by the calculation, and, check the results to determine the design of the furnace for the specific data according to the empirical formula of the size of the calibration, the data can be used for practical production. Through the rigorous calculation of the design, the converter furnace capacity ratio, aspect ratio, pool diameter and depth of experimental data have been determine. The results show that the design is reasonable. The design data of the converter and the corresponding furnace can meet the equipment of the effective volume of 120t converter design. That can ensure the smooth production process of the converter, while achieve the requirements of lining longevity.

A short-cut analytical model of hydrocarbon pool fire of different geometries, with enhanced view factor evaluation

Abstract In analyzing pool fires and the potential for domino effects, the most important aspects to be addressed on the basis of a proper consequence analysis are the evaluation of thermal radiation, the issues of interplant spacing, the employees’ safety zones and fire wall specifications. Even if scientific literature on pool-fire is sparse and modeling is well developed, the usual approach considers circular geometry, pseudo steady-state conditions, uniform flame temperature, cylindrical/conical flame shape with height depending on pool diameter. The specific analysis of rather complicated situations (partial confinement, irregular shapes, complex kinetics, heavy hydrocarbon fire, unsteady-state) usually requires the use of sophisticated integral models and/or time consuming CFD calculations, but when conservative results are enough, analytical models can be more useful especially in hazard assessment. We propose a modelling of a pool fire of a multi-component hydrocarbon mixture, under semi-confined geometry. The physical model of the pool is solved to provide a description of a variable heat emitting flame area, as a function of the vertical flame axis, thus representing a peculiar novelty of the approach. Starting from a real accident in a downstream oil industry involving pool fire of a heavy liquid HC mixture and domino effect, the application to an industrial case study is presented, in order to evidence the effective potentialities of the method.

Small scale experiment study on the characteristics of boilover

Crude oil boilover fire was experimentally studied in an open fire test space. Three circular steel trays, with diameters of 0.1 m, 0.15 m and 0.2 m, filled with crude oil were used in the experiment. Three important measurements, namely, mass burning rate, flame height and fuel temperature distributions, were collected and recorded during the entire combustion process. The results show that the combustion process can be divided into four typical stages: the growth stage, quasi-steady stage, boilover stage and decay stage. It is observed that the mass burning rate and the flame height in the boilover stage are considerably higher than that in the quasi-steady stage. In the quasi-steady stage, the initial fuel layer thickness has a limited influence on the mass burning rate and the flame height, whereas in the boilover stage, the influence is substantial because of the boilover effect. In both stages, the mass burning rate and the flame height increase with increasing pool diameters. The two boilover characteristic parameters, boilover onset time and boilover intensity, both increase with the initial fuel layer thickness and decrease with the pool diameter. Based on the ratio of initial fuel layer thickness to the pool diameter, prediction models for boilover onset time and boilover intensity are developed.

A refined methodology to determine the spatial and temporal variation in the emissivity of diffusion flames

Flame emissivity is an important parameter in the study of pool fires. A refined methodology is developed to determine the spatial and temporal variation in the flame emissivity of pool fires. Limitations of earlier methodologies include an assumption of axisymmetrical flame and the obtained data being spatially and temporally averaged. Experiments are performed with diesel and gasoline as the fuel for pool diameters of 0.3 m–1.0 m. Flame emissivity is obtained based on the calculation of flame transmissivity using an infrared camera with reference to electrically heated thin metal strips. Average emissivity is determined for the multi-averaged image of 80 instantaneous images. Complete spatial emissivity and temperature distribution are obtained. Vertical centerline emissivity matches reasonably well with the average emissivity reported in the literature.

An experimental study on thermal radiation of fire whirl

Fire whirl is frequently observed in wildland fires, and may cause serious difficulty in firefighting owing to its significant turbulent flow. In this paper, the radiation of fire whirl is investigated through experiments using a fire whirl facility made up of an air curtain apparatus, with five different sizes of n-heptane pools (25, 30, 35, 40 and 45 cm). The flame contour was extracted by image processing. By using infrared methods, the flame emissivity of fire whirl at different heights for different pool diameters was measured, and thereby a correlation was developed between the flame emissivity and the flame diameter. The soot volume fraction in the luminous flame is estimated to range within 2.5 × 10−6 to 4.0 × 10−6, much higher than that of general heptane pool fires, which provides an explanation of the higher flame emissivity of fire whirl. The emissive power profile v. normalised height is deduced from flame emissivity and flame temperature data. A multizone flame model (in which each zone is assumed as a grey body) is used, based on the measured data of flame emissivity, to predict the radiation of fire whirl. Comparison between the predicted and measured data of radiative flux shows good agreement.

Investigation on the Mechanism and Failure Mode of Laser Transmission Spot Welding Using PMMA Material for the Automotive Industry.

To satisfy the need of polymer connection in lightweight automobiles, a study on laser transmission spot welding using polymethyl methacrylate (PMMA) is conducted by using an Nd:YAG pulse laser. The influence of three variables, namely peak voltages, defocusing distances and the welding type (type I (pulse frequency and the duration is 25 Hz, 0.6 s) and type II (pulse frequency and the duration is 5 Hz, 3 s)) to the welding quality was investigated. The result showed that, in the case of the same peak voltages and defocusing distances, the number of bubbles for type I was obviously more than type II. The failure mode of type I was the base plate fracture along the solder joint, and the connection strength of type I was greater than type II. The weld pool diameter:depth ratio for type I was significantly greater than type II. It could be seen that there was a certain relationship between the weld pool diameter:depth ratio and the welding strength. By the finite element simulation, the weld pool for type I was more slender than type II, which was approximately the same as the experimental results.

Controlling surface topography using pulsed laser micro structuring

There is significant interest in controlling surface topography on metal parts including smoothing rough or wavy surfaces, adding aesthetic features, and creating functional structures. Pulsed laser micro structuring (PLμS) dynamically manipulates each pulse fluence during laser remelting to create a net, mass-neutral, lateral displacement of material several times greater than the melt pool diameter. This paper presents experimental investigations into specific process capabilities, example applications, and a novel phenomenological theory. The paper demonstrates how the resultant process can attenuate high-spatial-frequency roughness, correct mid-spatial-frequency error (i.e., waviness), and create desirable surface topography with a single laser system.

Nanoconfinement's Dramatic Impact on Proton Exchange between Glucose and Water.

Glucose nanoconfined by solubilization in water-containing AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reverse micelles has been investigated using 1H NMR. NMR spectra reveal well-defined signals for the glucose hydroxyl groups that suggest slow chemical exchange between them and the water hydroxyl groups. Using the EXSY (ZZ-exchange) method, the chemical exchange rate from water to glucose hydroxyl groups was measured for glucose in reverse micelles as a function of size (water pool diameter of ∼1-5 nm) at 25 °C. The chemical exchange rates observed in the nanoconfined interior are dramatically slower (5-20 times) than those observed for glucose in bulk aqueous solution at the same concentration as the micelle interior. Exchange rate constants are calculated via a mechanism that accounts for these observations, and implications of these results are presented and discussed.

Heat transfer to bodies engulfed in di-tert-butyl peroxide pool fires - Numerical simulations

The thermal response of bodies engulfed in di-tert-butyl peroxide (DTBP) pool fires is studied numerically. High heat release rates, high velocities and high emissive powers portray the combustion of DTBP. This makes exceptionally hazard for bodies engulfed in DTBP fire accidents. The concept of adiabatic surface temperature (AST) is applied for DTBP pool fires to circumvent the difficulty of defining the fire exposure boundary condition at the solid surface. Adiabatic surface temperatures (AST) are computed for pool diameters 1.13 m and 3.4 m using the fire dynamics simulator. The thermal response of cask in a 1.13 m DTBP pool fire is studied to verify the concept of AST. It is found that a cask encounters twofold the heat fluxes in DTBP fires than in diesel pool fires. More than 30% of the net heat flux to the cask is a direct result of the convective heat exchange between the fire and the cask. This implies that the regular safety guidelines formulated for hydrocarbon pool fires are not adequate for the safety of the bodies engulfed in DTBP pool fires.