Liquid fuel droplet heating with internal circulation

Prakash, Shiva; Sirignano, William A.

doi:10.1016/0017-9310(78)90180-1

Cited by 132 publications

(54 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the regime of PeL>1000, the vortex model proposed by Sirignano and coworkers (Prakash and Sirignano, 1978;Prakash and Sirignano, 1980;Tong and Sirignano, 1982;Sirignano, 1983;Abramzon and Sirignano, 1989;Sirignano, 2010) gives a good approximation. Both the velocity and temperature fields become similar to Hill's vortex since the heat transfer along the streamline direction is faster than the heat conduction normal to the streamlines.…”

Section: Water Evaporation From the Parent Droplet Surfacementioning

confidence: 91%

“…Both the velocity and temperature fields become similar to Hill's vortex since the heat transfer along the streamline direction is faster than the heat conduction normal to the streamlines. The temperature equation can be formulated in the conduction form as (Prakash and Sirignano, 1978;Prakash and Sirignano 1980)…”

Section: Water Evaporation From the Parent Droplet Surfacementioning

confidence: 99%

“…Sirignano and coworkers (Prakash and Sirignano, 1978;Prakash and Sirignano, 1980;Tong and Sirignano, 1982;Abramzon and Sirignano, 1989;Chiang et al, 1992;Sirignano, 2010) have further advanced the discussion on the droplet conditions between the above two extreme limits. For a droplet at a large droplet Reynolds number, the internal circulation is similar to Hill's vortex (ring vortex).…”

mentioning

confidence: 98%

See 2 more Smart Citations

Modeling Temperature Distribution Inside an Emulsion Fuel Droplet Under Convective Heating: A Key to Predicting Microexplosion and Puffing

et al. 2016

View full text Add to dashboard Cite

Microexplosion/puffing is rapid disintegration of a water-in-oil emulsion droplet caused by explosive boiling of embedded superheated water sub-droplets. To predict microexplosion/puffing, modeling the temperature distribution inside an emulsion droplet under convective heating is a prerequisite, since the temperature field determines the location of nucleation (vapor bubble initiation from superheated water). In the first part of the present study, convective heating of water-in-oil emulsion droplets under typical combustor conditions is investigated using high-fidelity simulation in order to accurately model inner-droplet temperature distribution. The shear force due to the ambient air flow induces internal circulation inside a droplet. It has been found that for droplets under investigation in the present study, the liquid Peclet number PeL is in a transitional regime of 100

show abstract

Section: Water Evaporation From the Parent Droplet Surfacementioning

confidence: 91%

Section: Water Evaporation From the Parent Droplet Surfacementioning

confidence: 99%

mentioning

confidence: 98%

See 1 more Smart Citation

Modeling Temperature Distribution Inside an Emulsion Fuel Droplet Under Convective Heating: A Key to Predicting Microexplosion and Puffing

et al. 2016

View full text Add to dashboard Cite

show abstract

“…(16), where the inner phase of water has been modeled as a heat sink Q l . Convection is not taken into account in this equation due to the higher viscosity of heavy fuel-oil [23], especially when emulsified with 5% of water.…”

Section: (14)mentioning

confidence: 99%

A Numerical Comparison of Spray Combustion between Raw and Water-in-Oil Emulsified Fuel

Tarlet¹,

Bellettre

Tazerout

et al. 2010

International Journal of Spray and Combustion Dynamics

View full text Add to dashboard Cite

Heavy fuel-oils, used engine oils and animal fat can be used as dense, viscous combustibles within industrial boilers. Burning these combustibles in the form of an emulsion with water enables to decrease the flame length and the formation of carbonaceous residue, in comparison with raw combustibles. These effects are due to the secondary atomization among the spray, which is a consequence of the micro-explosion phenomenon. This phenomenon acts in a single emulsion droplet by the fast (< 0.1 ms) vaporization of the inside water droplets, leading to complete disintegration of the whole emulsion droplet. First, the present work demonstrates a model of spray combustion of raw fuel. Secondly, the spray combustion of water-in-oil emulsified fuel is exposed to the same burning conditions, taking into account the micro-explosion phenomenon. Finally, the comparison between the results with and without second atomization shows some similar qualitative tendencies with experimental measurements from the literature.drag factor for spherical shape INTRODUCTIONMany cheap, available combustibles like heavy fuel-oil, used engine oil or animal fat can be used as combustibles, in spite of their higher density and viscosity. To burn these combustibles as water-in-oil emulsions has been known to shorten the flame length and to decrease the formation of carbonaceous residues and NOx, in comparison with the raw combustibles [1,2]. These changes are caused by the second atomization of the emulsified combustibles. Indeed, second atomization is the consequence of the phenomenon of micro-explosion upon individual droplets. Micro-explosion means the fast (less than 0.1 ms. [3,4]) vaporization of inside water droplets, enabling to break the initial emulsion droplet up into a group of smaller droplets. Nevertheless, the microexplosion delay, the length and the temperature of the flames of emulsified fuel are required in order to design emulsion-burning boilers and heating devices. Law [5] defines theoretically and physically the limiting temperatures for the onset of micro-explosion in an individual droplet. Nazha et al.[6] make use of a specific droplet model and a probability function to determine to what extent the micro-explosion predicted by the droplet analysis affects the spray development. This work demonstrates a model of spray combustion in order to obtain the fields of local combustion rate and temperature. A steady, 2D numerical simulation of the combustion chamber has been performed. The turbulent flow of gases (standard k-ε model [7]), the combustion within gaseous phase ("eddy-dissipation" model [8]), the transport equations for the 5 different gaseous species (C 19 H 30 , O 2 , CO 2 , H 2 O, N 2 ), and the boundary conditions are defined independently from the raw or emulsified nature of the combustible. In order to model liquid fuel combustion, a Lagrangian model of velocity, heat and mass transfer has been applied to liquid droplets. To model the injection of a spray, droplets are inserted in the computational dom...

show abstract

“…This viscous boundary layer, as well as the aerosol transfer boundary layer, are very thin, however, and the inviscid bubble core can be approximately assumed to extend to the bubble surface (Brignell, 1975). In modeling mass and aerosol transport inside these bubbles, furthermore, steady-state hydrodynamics can be assumed since the characteristic time period associated with the development of steady-state internal circulation is much shorter than the characteristic time for mass or aerosol diffusion in the bubble (Prakash and Sirignano, 1978;Ghiaasiaan and Eghbali, 1994;Ghiaasiaan and Yao, 1995). The bubble internal circulation can then be represented by Hill's vortex flow (Harper and Moore, 1968): where ?Ir, represents the Stokes stream function.…”

Section: Bubble Hydrodynamicsmentioning

confidence: 99%

A Theoretical Model for Deposition of Aerosols in Rising Spherical Bubbles due to Diffusion, Convection, and Inertia

Ghiaasiaan

Yao

1997

Aerosol Science and Technology

View full text Add to dashboard Cite

ABSTRACT. A novel approximate theoretical analysis is proposed whereby the deposition of aerosols in expanding and shrinking spherical bubbles rising in stagnant liquid due to the combined effects of molecular diffusion, convection, and inertia is modeled. The bubble internal circulation is assumed to be similar to Hill's vortex flow.Using the new method, parametric calculations representing conditions where bubbles remain spherical and nonoscillating, and diffusion, convection, and inertia are the dominant aerosol removal mechanisms, are performed, and the contribution of the inertial transport mechanism is discussed. It is also suggested that the common practice of using Fuchs's methodology, where aerosol fluxes resulting from different mechanisms are separately calculated using simple models and added together to find the total aerosol flux, is inadequate.

show abstract

Liquid fuel droplet heating with internal circulation

Cited by 132 publications

References 8 publications

Modeling Temperature Distribution Inside an Emulsion Fuel Droplet Under Convective Heating: A Key to Predicting Microexplosion and Puffing

Modeling Temperature Distribution Inside an Emulsion Fuel Droplet Under Convective Heating: A Key to Predicting Microexplosion and Puffing

A Numerical Comparison of Spray Combustion between Raw and Water-in-Oil Emulsified Fuel

A Theoretical Model for Deposition of Aerosols in Rising Spherical Bubbles due to Diffusion, Convection, and Inertia

Contact Info

Product

Resources

About