Droplet vaporization model for spray combustion calculations

Abramzon, B.; Sirignano, William A.

doi:10.2514/6.1988-636

Cited by 197 publications

(422 citation statements)

References 21 publications

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“…We assume that the ambient gas heat and mass transfer may be viewed as quasi-steady. This assumption was supported by Hubbard et al's study that analyzed the effects of transients and variable properties on the droplet vaporization [16,17]. Also Matalon and Law [18] derived the results that there is only a change of relative order o(ρ g /ρ p ) 1/2 in the droplet vaporization rate if gas phase unsteadiness model was used.…”

Section: Description Of the Problem And Modelmentioning

confidence: 89%

Dynamic response of vaporizing droplet to pressure oscillation

2016

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inertia of the droplet also plays a considerable role in determining the phase lag. List of symbols A PSurface area of the droplet (m 2 ) B M Spalding mass transfer number B T Spalding heat transfer number C D Drag coefficient C P,F Specific heat of droplet vapor evaluated at the reference conditions in the gas film (J/kg K) C P,g Gas specific heat evaluated at the reference conditions (J/kg K) C P,l Droplet specific heat (J/kg K) D i,m Binary diffusion coefficient evaluated at the reference conditions (m 2 /s)Frequency of fluctuation (Hz) F M Diffusion film thickness correction factor F T Thermal film thickness correction factorGas conductivity valuated at the reference conditions in the gas film (W/m K) k l Droplet conductivity (W/m K) LeLewis numbeṙ mMass vaporization rate (kg/s) m P Droplet mass (kg) M w,i Molecular weight of droplet vapor (kg/kmol) M w,j Molecular weight of ambient gas (kg/kmol) Nu Actual Nusselt number Nu * Modified Nusselt number Nu 0 Nusselt number for the non-vaporizing droplet Abstract Combustion instability is a major challenge in the development of the liquid propellant engines, and droplet vaporization is viewed as a potential mechanism for driving instabilities. Based on the previous work, an unsteady droplet heating and vaporization model was developed. The model and numerical method are validated by experimental data available in literature, and then the oscillatory vaporization of n-Heptane droplet exposed to unsteady harmonic nitrogen atmosphere was numerically investigated over a wide range of amplitudes and frequencies. Also, temperature variations inside the droplet were demonstrated under oscillation environments. It was found that the thermal wave is attenuated with significantly reduced wave intensities as it penetrates deep into droplet from the ambient gas. Droplet surface temperature exhibits smaller fluctuation than that of the ambient gas, and it exhibits a time lag with regard to the pressure variation. Furthermore, the mechanism leading to phase lag of vaporization rate with respect to pressure oscillation was unraveled. Results show that this phase lag varies during the droplet lifetime and it is strongly influenced by oscillation frequency, indicating droplet vaporization is only capable of driving combustion instability in some certain frequency domains. Instead, the amplitude of the oscillation does not have very significant effects. It is noteworthy that thermal

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Section: Description Of the Problem And Modelmentioning

confidence: 89%

Dynamic response of vaporizing droplet to pressure oscillation

2016

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“…Subject of the modelling is in particular a correct description of the Sherwood number, also at high transfer rates, where the deformation of the boundary layer profiles caused by the mass transfer cannot be neglected. For the present work the model by Abramzon and Sirignano is used [5].…”

Section: Theoretical Modelingmentioning

confidence: 99%

“…In this definition, the subscript G denotes gas properties, Sh Ã is a modified Sherwood number, and B m the Spalding mass transfer number [5]. In the nondimensional diffusion equation (8), the characteristic parameter G is defined by…”

Section: Theoretical Modelingmentioning

confidence: 99%

“…The development of an electrochemical process for removing chlorine from hydrochloric acid has its origin mainly in publications on the electrochemical removal of gas from water or electrolytes [3,4,5]. Since graphite is suitable as an electrode material for hydrochloric acid electrolysis, the cathode was manufactured in graphite in this instance as well, owing to chlorine's low deposition potential on graphite [6].…”

Section: Problemmentioning

confidence: 99%

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Modeling and Experimental Investigation of the Morphology of Spray Dryed Particles

Brenn¹,

Wiedemann²,

Rensink

et al. 2001

Chem. Eng. Technol.

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“…This is applicable for the case where no gas is dissolved into the liquid and the vaporization rate is large relative to the rate of diffusion. [20]. The modification is based on the experimental correlation of Renksizbulut and Yuen [21].…”

Section: Model Formulationmentioning

confidence: 99%

A New High Pressure Droplet Vaporization Model for Diesel Engine Modeling

Curtis

Uludogan

Reitz

1995

SAE Technical Paper Series

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A droplet vaporization model has been developed for use in high pressure spray modeling. The model is a modification of the common Spalding vaporization model that accounts for the effects of high pressure on phase equilibrium, transport properties, and surface tension. The new model allows for a nonuniform temperature within the liquid by using a simple 2-zone model for the droplet. The effects of the different modifications are tested both for the case of a single vaporizing droplet in a quiescent environment as well as for a high pressure spray using the KIVA II code. Comparisons with vaporizing spray experiments show somewhat improved spray penetration predictions. Also, the effect of the vaporization model on diesel combustion predictions was studied by applying the models to simulate the combustion process in a heavy duty diesel engine. In this case the standard and High Pressure vaporization models were found to give similar heat release and emissions results. However, the results show that a more realistic representation of the vaporization process is achieved with the new model. In particular, less unburned fuel is predicted to remain in the combustion chamber late in the power stroke.

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Droplet vaporization model for spray combustion calculations

Cited by 197 publications

References 21 publications

Dynamic response of vaporizing droplet to pressure oscillation

Dynamic response of vaporizing droplet to pressure oscillation

Modeling and Experimental Investigation of the Morphology of Spray Dryed Particles

A New High Pressure Droplet Vaporization Model for Diesel Engine Modeling

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