Mass transfer from liquid fuel droplets in turbulent flow

Gökalp, İskender; Chauveau, Christian; Simon, Olivier; Chesneau, Xavier

doi:10.1016/0010-2180(92)90016-i

Cited by 63 publications

(73 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As they have mentioned, most of studies attempted to extend the application of Frössling correlations [9] for Nusselt (Nu av ) and Sherwood (Sh av ) numbers in which the effects of airstream turbulence are accounted for in a correction factor C T as below Nu av = A + B Re 0.5 Sc 0.333 (C T ) Sh av = A + B Re 0.5 Pr 0.333 (C T ) . (1) Here, A , B and C T are constants that depend on turbulent intensity and airstream Reynolds number (Re). As it is implied by considering the form of modified Frössling correlations in (1) and dependency of constants A , B and C T to the turbulence properties of the airstream, the approach of above mentioned studies are to examine experimentally or numerically the rate of heat and mass transfer from an evaporating/combusting droplet in various turbulent flow, namely various turbulent intensity, in order to measure the values of A , B and C T .…”

Section: Introductionmentioning

confidence: 99%

“…(1) Here, A , B and C T are constants that depend on turbulent intensity and airstream Reynolds number (Re). As it is implied by considering the form of modified Frössling correlations in (1) and dependency of constants A , B and C T to the turbulence properties of the airstream, the approach of above mentioned studies are to examine experimentally or numerically the rate of heat and mass transfer from an evaporating/combusting droplet in various turbulent flow, namely various turbulent intensity, in order to measure the values of A , B and C T . Rather than the above approach that is based on the effects of bulk turbulent properties on the combustion or evaporation of fuel droplets, another approach that was initiated more recently by Masoudi and Sirignano [10] is aimed to get insight into the phenomena that occur in much smaller time and length scales.…”

Section: Introductionmentioning

confidence: 99%

“…The knowledge acquired then is essential to the prediction and improvement of the performance of liquid spray combustors. Since the flow in practical combustors is highly turbulent the investigation of the effects of airstream turbulence on the phenomena during the combustion of fuel droplets received great attention in the past decades [1][2][3][4][5][6][7]. A review by Birouk and Gökalp [8] has provided extensive references and conclusions for the sate-of-the-art until 2006.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Thermal-drag and Transition from Quasi-steady to Highly-unsteady Combustion of a Fuel Droplet in the Presence of Upstream Velocity Oscillations

Jangi

Shaw

Kobayashi

2009

Flow Turbulence Combust

View full text Add to dashboard Cite

Numerical studies on the behaviors of combustion of 1-butanol fuel droplet at presence of upstream velocity oscillation are performed. Fuel droplet has an initial diameter of 1.25 mm and ambiance pressure and temperature are 0.4 MPa and 300 K, respectively. These conditions are those in which the microgravity experiments in literature conducted. In the excellent agreement with the experimental data, numerical results show a significant enhancement of the burning rate of droplet compared to what is predicted by quasi-steady film theory models. The mechanism of the enhancement of burning rate is clarified then by observation of a new mechanism that is named thermal-drag, TD. It is shown, depending on the amplitude and frequency of the upstream velocity oscillation, the flame in wake region of droplet can move toward the droplet surface by the force of vortex flow motions produced by the TD mechanism. It is verified that such movement of the flame is responsible for the enhancement of the burning rate and deviation of the response of the evaporation process form the predictions of the quasi-steady model. Frequency analysis of the burning rate reveals that at low frequency and amplitude the FFT diagram of the burning rate contains of only one main peak synchronies with the frequency of upstream velocity oscillation, which implies a quasi-steady response. However; at high frequency and amplitude the diagram includes of wide range of 98 Flow Turbulence Combust (2010) 84:97-123 frequencies beside of the main peak that readily shows deviation from the quasisteady conditions. In the latter, the study on the response of the combustion to the upstream velocity fluctuations in which the fluctuations contains of three wave numbers shows the amplification of the effects of low frequency fluctuations rather than that of damping of the effects of high frequency fluctuations on the evaporation processes.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermal-drag and Transition from Quasi-steady to Highly-unsteady Combustion of a Fuel Droplet in the Presence of Upstream Velocity Oscillations

Jangi

Shaw

Kobayashi

2009

Flow Turbulence Combust

View full text Add to dashboard Cite

show abstract

“…The interactions between gas and spray droplets depend on many factors (e.g., gas and droplet physical properties, phase velocities, concentrations, temperatures and turbulent fluctuations, etc.). They could be classified in three main categories including the turbulent dispersion of droplets, the so-called turbulence modulation, i.e., the modification of the continuous phase turbulence characteristics by droplets or by interface transport and, the modification of interface transport by turbulence [8,7,11,44].…”

Section: Introductionmentioning

confidence: 99%

Modeling and Simulation of Effects of Turbulence on Vaporization, Mixing and Combustion of Liquid-Fuel Sprays

Sadiki

Chrigui

Janicka

et al. 2005

Flow Turbulence Combust

View full text Add to dashboard Cite

The objective of this work is twofold. Firstly, the effects of turbulence intensity variations on the turbulent droplet dispersion, vaporization and mixing for non-reacting sprays (with and without swirl) are pointed out. Secondly, the effects of the coupling of the turbulence modulation with external parameters, such as swirl intensity, on turbulent spray combustion are analyzed in configurations of engineering importance. This is achieved by using advanced models for turbulence, evaporation and turbulence modulation implemented into FASTEST-LAG3D-codes: (1) To highlight the influence of turbulence modulation on some spray properties, a thermodynamically consistent modulation model has been considered besides the standard assumption and the well known Crowe's model. For turbulent droplet dispersion, we rely on the Markov-sequence formulation.(2) In order to characterize phase transition processes ongoing on droplets surfaces, a non-equilibrium evaporation model shows better agreement with experiments in comparison with the quasi-equilibrium-based evaporation models often used. (3) The results of turbulence intensity variations reveal the existence of a limited range out of which the increase or decrease of the turbulence intensity affects no more the efficiency of the heat and mass transfer. A derived characteristic number, a vaporization Damkhöler number, possesses a critical value which separates two different behavior regimes with respect to the turbulence/droplet vaporization interactions. (4) Under reacting conditions, it is shown how the evaporation characteristics, mixing rate and combustion process are strongly influenced by swirl intensity and turbulence modulation. In particular, the turbulence modulation modifies the evaporation rate, which in turn influences the mixing and the species concentration distribution. In the case under investigation, it is demonstrated that this effect cannot be neglected for low swirl intensities (Sw.Nu. ≤ 1) in the region far from the nozzle, and close to the nozzle for high swirl number intensities. In providing these particular characteristics, a reliable control of the mixing of gaseous fuel and air in evaporating and reacting sprays, and a possible optimization of the mixing process can tentatively be achieved.

show abstract

“…Although in the past considerable research work has been reported concerning the effect of turbulence on evaporation rate of suspended droplets (for example, see Gökalp et al 1992;Birouk et al 1996;Birouk & Toth 2015), there is no general consensus yet on the role of air turbulence in a spray. According to Gökalp et al (1992), a way to evaluate the role of turbulence in droplet evaporation is by considering the vaporization Damköhler number (Da v ), which is the ratio of the time scale of turbulent eddies (τ g ) and droplet evaporation time (τ v ). For two droplets of different volatility but the same size subjected to the same turbulent flow field, smaller Da v implies a stronger influence of turbulence on droplet evaporation.…”

Section: Correlation Between Droplet Velocity and Vapour Mass Fractionmentioning

confidence: 99%

Interaction of droplet dispersion and evaporation in a polydispersed spray

2018

View full text Add to dashboard Cite

The interaction between droplet dispersion and evaporation in an acetone spray evaporating under ambient conditions is experimentally studied with an aim to understand the physics behind the spatial correlation between the local vapour mass fraction and droplets. The influence of gas-phase turbulence and droplet-gas slip velocity of such correlations is examined, while the focus is on the consequence of droplet clustering on collective evaporation of droplet clouds. Simultaneous and planar measurements of droplet size, velocity and number density, and vapour mass fraction around the droplets, were obtained by combining the interferometric laser imaging for droplet sizing and planar laser induced fluorescence techniques (Sahu et al., Exp. Fluids, vol. 55, 1673, 2014b. Comparison with droplet measurements in a non-evaporating water spray under the same flow conditions showed that droplet evaporation leads to higher fluctuations of droplet number density and velocity relative to the respective mean values. While the mean droplet-gas slip velocity was found to be negligibly small, the vaporization Damköhler number (Da v ) was approximately 'one', which means the droplet evaporation time and the characteristic time scale of large eddies are of the same order. Thus, the influence of the convective effect on droplet evaporation is not expected to be significant in comparison to the instantaneous fluctuations of slip velocity, which refers to the direct effect of turbulence. An overall linearly increasing trend was observed in the scatter plot of the instantaneous values of droplet number density (N) and vapour mass fraction (Y F ). Accordingly, the correlation coefficient of fluctuations of vapour mass fraction and droplet number density (R n * y ) was relatively high (≈0.5) implying moderately high correlation. However, considerable spread of the N versus Y F scatter plot along both coordinates demonstrated the influence on droplet evaporation due to turbulent droplet dispersion, which leads to droplet clustering. The presence of droplet clustering was confirmed by the measurement of spatial correlation coefficient of the fluctuations of droplet number density for different size classes (R n * n ) and the radial distribution function (RDF) of the droplets. Also, the tendency of the droplets to form clusters was higher for the acetone spray than the water spray, indicating that droplet evaporation promoted droplet grouping in the spray. The instantaneous group evaporation number (G) was evaluated from the measured length scale of droplet clusters (by the RDF) and the average droplet size and spacing in instantaneous clusters. The mean value of † Email address for correspondence: ssahu@iitm.ac.in G suggests an internal group evaporation mode of the droplet clouds near the spray centre, while single droplet evaporation prevails near the spray boundary. However, the large fluctuations in the magnitude of instantaneous values of G at all measurement locations implied temporal variations in the mode of droplet cloud evapor...

show abstract

Mass transfer from liquid fuel droplets in turbulent flow

Cited by 63 publications

References 19 publications

Thermal-drag and Transition from Quasi-steady to Highly-unsteady Combustion of a Fuel Droplet in the Presence of Upstream Velocity Oscillations

Thermal-drag and Transition from Quasi-steady to Highly-unsteady Combustion of a Fuel Droplet in the Presence of Upstream Velocity Oscillations

Modeling and Simulation of Effects of Turbulence on Vaporization, Mixing and Combustion of Liquid-Fuel Sprays

Interaction of droplet dispersion and evaporation in a polydispersed spray

Contact Info

Product

Resources

About