Evaporation of Volatile Liquid Pools Under Forced Convection: Part 2—Integration of a Vaporization Model in a CFD Software

2012 ◽  
Author(s):  
Nicolas Doué ◽  
Karim Loueslati ◽  
Dominique Alonso ◽  
Ghislain Genin ◽  
Michel Molière
Keyword(s):  
Liquid Pool ◽  
Liquid Fuels ◽  
Accurate Assessment ◽  
Volatile Species ◽  
Reliable Prediction ◽  
Ansys Fluent ◽  
Volatile Liquid ◽  
Liquid Pools ◽  
Mass Transfers ◽  
Ventilation Conditions

The transfer under dynamic conditions of volatile species from a liquid pool to the surrounding air is gaining interest in the engineering community. In particular, increasingly stringent regulations and standards apply to all types of flammable substances. This is especially the case in stationary gas turbine applications, where the vaporization of accidentally occurring pools of liquid fuels attracts increasing attention. Since the flame-to-explosion transition cases are insufficiently controlled, the current, only practicable approach to assess the explosion risks arising from a fuel pool in an enclosure consists in quantifying the amount of vapor that leaves the pool and minimizing, by means of a proper dilution strategy, the potential damages entailed by the ignition of the resulting cloud. This approach requires two steps: (1) The accurate assessment of vaporization rates under given ventilation conditions, a task that calls for skills in thermal and mass transfers. (2) The reliable prediction of the transport of the vapors in the ventilation stream, a task specifically focused on fluid dynamics. The three teams involved in this paper have joined their efforts to achieve this multidisciplinary objective. As a first task, the LRGP team (Laboratoire des Reactions et Génie des Procédés) and GE Energy have experimentally validated a vaporization model initially devised for water pools. This work has been reported in a recent paper. Concurrently, EURO/CFD and GE Energy have developed a CFD approach devoted to the mixing/dilution processes in defined enclosure geometries and under specified ventilation conditions. Finally both approaches havebeen coupled by EURO/CFD to produce predictive isopleth pictures of the vapor clouds generated under given temperature and velocity conditions. The present paper covers the integration of the liquid pool vaporization model in thecommercial CFD software ANSYS Fluent and sets out the results obtained. This dual, concerted approach is a first of the kind to the authors’ knowledge and proves fruitful for the prediction of the spatial distributions of the volatile species developed when a volatile pool vaporizes in a ventilated enclosure. It fills a gap in the analysis of safety scenarios arising from spillages of liquid fuels and provides a rational tool in zone classification studies.

An Experimental Study of the Interaction of Multiple Liquid Pool Fires

1995 ◽  
Vol 117 (1) ◽  
pp. 37-42 ◽  
Author(s):  
J. R. Vincent ◽  
S. R. Gollahalli
Keyword(s):  
Carbon Dioxide ◽  
Large Fraction ◽  
Liquid Pool ◽  
Flame Height ◽  
Design Parameters ◽  
Pool Fires ◽  
Pool Surface ◽  
Flammable Liquids ◽  
Liquid Pools ◽  
Ignition And Combustion

The risk of accidental spills and possible fires is high in the storage and handling of large quantities of flammable liquids. Such liquid pool fires are generally buoyancy-driven and emit a large fraction of their heat release in the form of radiation. Ignition and combustion characteristics of liquid pools depend on the design parameters such as diameter, spacing, and shape of the pools. This laboratory scale study was conducted to determine the effects of these parameters on the characteristics of multiple liquid pool fires. The measurements reported include pool surface regression rate, flame height, temperature, and concentrations of carbon dioxide, soot, and oxygen.

scholarly journals Bubble Bursting and Drainage Characteristics at the Free Surface of a Liquid Pool with an Aerosol

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Xiang Yu ◽  
Haifeng Gu ◽  
Weikai Yin ◽  
Qingyang Sun
Keyword(s):  
Nuclear Reactor ◽  
Liquid Pool ◽  
Radioactive Source ◽  
Lifetime Distribution ◽  
Liquid Temperature ◽  
Radioactive Aerosols ◽  
Bubble Bursting ◽  
Liquid Pools ◽  
Reactor Accidents ◽  
Physical Quantities

When nuclear reactor accidents such as steam generator pipe ruptures or core melting occur, radioactive aerosols will remain in the liquid pools. Bubbles may be generated by boiling or gas injection. Film droplets produced by bubble bursts may entrain radioactive aerosols from the liquid to the air. This long-lasting behavior can produce a considerable amount of aerosols. To evaluate radioactive source terms, many physical quantities related to bubble bursting need to be determined, such as bubble burst position, bubble lifetime, cap film roll-up velocity, and cap film thickness, which are very important parameters that influence the releasing of radioactive aerosols. In this research, the phenomenon of bubble bursting was investigated by visualization. The above parameters were measured. We obtained the lifetime distribution of bubbles under different conditions, and we found that the addition of an aerosol increased the lifetime of the bubbles. By comparing the bubble lifetime to the roll-up velocity and cap thickness, we showed that the increase of the liquid temperature thickened the cap at rupture and the increase of the air temperature thinned the cap. The addition of an aerosol increased the film roll-up velocity.

Experimental and Computational Analysis of an Additive Manufactured Vaporization Injector for a Micro-Gas Turbine

2019 ◽  
Author(s):  
Adamos Adamou ◽  
Ian Kennedy ◽  
Ben Farmer ◽  
Ahmed Hussein ◽  
Colin Copeland
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Front Surface ◽  
Liquid Fuels ◽  
Balance Model ◽  
Fuel Temperature ◽  
Ansys Fluent ◽  
Complete Combustion ◽  
Flamelet Model ◽  
Micro Gas Turbine

Abstract Vaporization injectors have been in existence for decades and are a well-proven method of preparing liquid fuels for combustion by heating them above the boiling point of their heaviest hydrocarbon ingredient. By doing so, it converts the fuels into a vapour prior to combustion. When attempting to apply this method of fuel vaporization to micro gas turbines, manufacturing difficulties arise, due to the small complex passages that are required to direct the fuel closer to the high-temperature zone in the combustion chamber and then back to a favourable injection location. This is where the use of additive manufacturing (AM) can prove advantageous due to the complex designs that can be achieved at much smaller scales and potentially at cheaper costs when compared to traditional subtractive manufacturing. The motivation behind the research is to improve the overall efficiency of micro-gas turbines, so they can be applied as range extenders in electric vehicles. Due to the increasing adoption of vehicle electrification. This paper covers the comparison of experimental results for two traditionally manufactured injectors and a third selective laser melted injector (SLM), which were tested in a swirl stabilised micro gas turbine can type combustor on the University of Baths gas stand. The operating range of the tests was 1–4 Bar and 30 to 630 °C inlet air. To the authors knowledge, this is the first such comparison to be made for a gas turbine in open literature, despite wide reports of AM being used in large gas turbines. From the tests, it was found that the 3 and 8 hole machined injectors could not produce stable combustion at the desired operating condition of 4 Bar and 630 °C. The SLM 8 hole injector, however, was able to sustain a stable and constant burn at this design point with low NOx, CO and THC emissions. It was also noticed that the flame colour changed from a yellow flame when testing the first two injectors, to a blue flame when testing the SLM injector suggesting more complete combustion was being achieved due to the lack of soot in burned products, this was assumed to be due to the fuel reaching its saturation conditions within the injector. A number of measurements were taken at various points around the combustor, which included temperatures, pressures and emissions readings. These results were then used to create and validate a non-premixed steady diffusion flamelet model in ANSYS Fluent for the AM injector case. The CFD results were found to overpredict the temperature by approximately 10% when compared to the thermocouple values. This was found to be similar to other studies with similar experimental and computational setups, so it was deemed acceptable. From the validated CFD model, the heat flux at the front surface of the injector was extracted, to be used in a simple heat balance model. Based on a conservative estimate of fuel temperature, the model found that the SLM injectors should have created very near saturation conditions in the nozzle. As this was a conservative analysis, it confirms the experimental findings that partially vaporized fuel was exciting the injector. The model also showed that the fuel in the traditionally machined, 8 hole injector would most likely exit as a liquid.

Assessment of Film Drop Release From Liquid Pools by an Empirical Correlation Approach

2008 ◽  
Author(s):  
Maik Dapper ◽  
Hermann-Josef Wagner ◽  
Marco K. Koch
Keyword(s):  
Source Term ◽  
Late Phase ◽  
Liquid Pool ◽  
Empirical Correlation ◽  
Severe Accident ◽  
Pool Surface ◽  
Process Factors ◽  
Liquid Pools ◽  
Bubble Sizes ◽  
Log Normal

The present work deals with the topic of wet resuspension, particularly with regard to the basics of film drop release from bubbles and its impact on the aerosol source term as well as with the development of an empirical correlation approach adapted to the containment code system COCOSYS at low atmosphere motion. Film drops are discharged from the lamella of a bubble during the disruption process, while the bubble is resting at the fluid surface. Besides the description of the bubble disruption process, factors which have an influence on the mass and size distribution of the drops released from the bubble lamella are discussed. To analyse the distribution of the film drops of different bubble sizes, measured film drop distributions of several bubble diameters were collected from the literature. The analysis shows that with the presence of surfactants (surface-active agents) a log-normal count distribution can be used for the approximation of the drop distribution. By the evaporation of the liquid of the released film drops the solved and/or suspended materials remain as particles. In dependence of their size the drops or particles are airborne or fall back onto the liquid pool surface. The remaining airborne drops/particles are able to contribute in the late phase of a severe accident to the source term, if they are radioactive.

Influence of Lateral Boundaries on Evaporative-Driven Convection Patterns

2008 ◽  
Author(s):  
C. S. Iorio ◽  
O. A. Kabov
Keyword(s):  
Gas Phase ◽  
Selection Process ◽  
Liquid Pool ◽  
Point Of View ◽  
Inert Gas ◽  
Geometrical Parameters ◽  
Layer Depth ◽  
Volatile Liquid ◽  
Convection Patterns ◽  
Heat Of Evaporation

The evolution of convective patterns arising in evaporating liquid layers subject to a flow of inert gas depends on dynamical, thermo-physical and geometrical parameters. To the first group it is possible to associate the average velocity of the inert gas current and the total pressure of the gas phase — inert gas and vapor — insisting on the evaporating layer. The volatile liquid is also of importance in the convective patterns selection especially for what concerns the values of the latent heat of evaporation and of the cinematic viscosity. In this paper, we will focus on the influence that the lateral boundaries of the liquid pool have in the pattern selection process from the numerical point of view. A particular emphasis will be given to the heat transfer characteristics and to their dependence from both the liquid layer depth and the size of the evaporating surface.

Convective instability in liquid pools heated from below

1971 ◽  
Vol 47 (4) ◽  
pp. 779-787 ◽  
Author(s):  
Harvey J. Palmer ◽  
John C. Berg
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Stability Analysis ◽  
Convective Instability ◽  
Temperature Drop ◽  
Stability Limit ◽  
Liquid Pool ◽  
Silicone Oils ◽  
Liquid Pools ◽  
The Stability

The linear hydrodynamic stability analysis of liquid pools heated from below combining surface tension and buoyancy effects as presented by Nield (1964) is confirmed by experiment for a series of silicone oils. The experimental method used is an adaptation of the Schmidt–Milverton technique, in which the stability limit is located by the change of slope in the plot of heat flux versus temperature drop across the liquid pool.

Microscopic Approaches to Decomposition and Burning Processes of a Micro Plastic Resin Particle

2007 ◽  
Author(s):  
Atsunori Yamamoto ◽  
Ryuji Yamakita ◽  
Yojiro Ishino ◽  
Norio Ohiwa
Keyword(s):  
High Speed ◽  
Diffusion Flames ◽  
Temporal Variations ◽  
Heating Time ◽  
Liquid Fuels ◽  
Combustion Gas ◽  
Resin Particle ◽  
Schlieren System ◽  
Volatile Liquid ◽  
Plastic Resin

From a fundamental and microscopic viewpoint to elucidate the possibility and availability of thermal recycling of wasted plastic resin, a series of heating processes of melting, thermal decomposition and burning of a spherical micro plastic resin particle having a diameter of about 200 μm are observed, when it is suddenly exposed to hot oxidizing combustion gas. Three ingenious devices are introduced; the first is a high-speed microscopic direct and schlieren system, the second is a pre-mixed mini-burner for abrupt heating, which is equipped with a pair of spark gaps at its exit and is discharged synchronously with the starting signal of high-speed camera, and the third is a single mini-puff generator, which enables to extinguish instantly all flames around the micro particle at an arbitrary assigned time after the spark ignition. Polyethylene terephthalate and polyethylene are used as two typical plastic resins. In this paper the dependency of internal and external appearances of residual plastic embers on the heating time and the initial plastic composition is optically analyzed, along with appearances of internal micro bubbling, micro jets and micro diffusion flames during abrupt heating. Based on temporal variations of the surface area of a micro plastic particle, the burning rate constant is also evaluated and compared with well-known volatile liquid fuels.

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