Observations on the low temperature vaporization and envelope or wake flame burning of n-heptane droplets at reduced gravity during parabolic flights

Gökalp, İskender; Chauveau, Christian; Richard, Jean-Robert; Kramer, Matthew R.; Leuckel, Wolfgang

doi:10.1016/s0082-0784(89)80218-8

Cited by 19 publications

(6 citation statements)

References 10 publications

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“…Figure 4 shows a typical variation of the time-history of the squared normalized 1.18 mm diameter of n-heptane droplet in a forced convective laminar flow having a streamwise mean velocity of U 1¼ 6 m/s. This figure shows that the present predictions agree reasonably well with the published numerical data (Zhang, 2003) and almost perfectly with experimental data (Gökalp et al, 1988).…”

Section: Resultssupporting

confidence: 90%

A numerical model for calculating the vaporization rate of a fuel droplet exposed to a convective turbulent airflow

Al-Sood

Birouk

2008

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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Purpose -The purpose of this paper is to develop a three-dimensional (3D) numerical model capable of predicting the vaporization rate of a liquid fuel droplet exposed to a convective turbulent airflow at ambient room temperature and atmospheric pressure conditions. Design/methodology/approach -The 3D Reynolds-Averaged Navier-Stokes equations, together with the mass, species, and energy conservation equations were solved in Cartesian coordinates. Closure for the turbulence stress terms for turbulent flow was accomplished by testing two different turbulence closure models; the low-Reynolds number (LRN) k-1 and shear-stress transport (SST). Numerical solution of the resulted set of equations was achieved by using blocked-off technique with finite volume method. Findings -The present predictions showed good agreement with published turbulent experimental data when using the SST turbulence closure model. However, the LRN k-1 model produced poor predictions. In addition, the simple numerical approach employed in the present code demonstrated its worth.Research limitations/implications -The present study is limited to ambient room temperature and atmospheric pressure conditions. However, in most practical spray flow applications droplets evaporate under ambient high-pressure and a hot turbulent environment. Therefore, an extension of this study to evaluate the effects of pressure and temperature will make it more practical. Originality/value -It is believed that the numerical code developed is of great importance to scientists and engineers working in the field of spray combustion. This paper also demonstrated for the first time that the simple blocked-off technique can be successfully used for treating a droplet in the flow calculation domain.

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Section: Resultssupporting

confidence: 90%

A numerical model for calculating the vaporization rate of a fuel droplet exposed to a convective turbulent airflow

Al-Sood

Birouk

2008

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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“…Additional validation of the model is presented in the present paper by comparing with the experimental results of Gokalp et al [31]. Table 1 shows the droplet lifetimes for 2 cases of initial droplet diameters and freestream velocities obtained from the numerical model and experimental results of Gokalp et al [31].…”

Section: Resultsmentioning

confidence: 60%

“…The comparison between the numerical result and the experimental data is very good. The ambient gas employed in the numerical model is N 2 and that used in the experiment [31] is air. An n-heptane droplet with an initial diameter of 100 μm, initially at a temperature of 300 K, moving with an initial freestream velocity of 1.5 m/s, within a zero-gravity nitrogen environment at 1000 K, has been studied here.…”

Section: Resultsmentioning

confidence: 99%

Subcritical and supercritical droplet evaporation within a zero-gravity environment: Low Weber number relative motion

Zhang

Raghavan

Gogos

2008

International Communications in Heat and Mass Transfer

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A validated comprehensive axisymmetric numerical model, which includes the high pressure transient effects, variable thermo-physical properties and inert species solubility in the liquid phase, has been employed to study the evaporation of moving n-heptane droplets within a zero-gravity nitrogen environment, for a wide range of ambient pressures and initial freestream velocities. At the high ambient temperature considered (1000 K), the evaporation constant increases with the ambient pressure. At low ambient pressure, the evaporation constant becomes almost a constant during the end of the lifetime. At high ambient pressures, the transient behavior is present throughout the droplet lifetime. The final penetration distance of a moving droplet decreases exponentially with increasing ambient pressure. The average evaporation constant increases with ambient pressure. The variation is almost linear for reduced ambient pressures smaller than approximately 2. For higher values, depending on the initial freestream velocity, the average evaporation constant either becomes a constant (at low initial freestream velocities) or it non-linearly increases (at high initial freestream velocities) with the ambient pressure. Droplet lifetime decreases with increasing ambient pressure and/or increasing initial freestream velocity.

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“…The d-squared law in its form (1) has been experimentally validated over a substantial range of thermodynamic states as well as for a variety of nonsooting monocomponent droplets through a wider spectrum of chemical complexity [7,8,9,10,11,12,13,14,15,16]. Multicomponent droplets, however, 10 2 oer a conspicuously dierent behavior owed to the continuous variation in molar composition of both liquid x(t) and coexisting vapor y(t). Species with genuinely dissimilar properties lead to evaporation rates that vary substantially over time [17,18,19].…”

Section: Introductionmentioning

confidence: 99%

Diffusion limited evaporation of a binary liquid film

Chatwell

Heinen

Vrabec

2019

International Journal of Heat and Mass Transfer

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An analytical solution of a model uid's time behavior, known as the Stefan problem, is presented. A scenario is investigated in which a planar twocomponent liquid lm is continuously evaporating into a thermodynamically non-ideal vapor phase. Evaporation is initiated and maintained by a spatial chemical potential gradient, while its rate is limited by the components' diusion uxes across the vapor-liquid interface. Local thermodynamic equilibrium is found to be present throughout the process. In contrast to the classical approach relying on equations of state, all required non-idealities are formulated in relation to the Gibbs energy and are determined by molecular simulations. Initially, the liquid is an equimolar mixture of two components of dierent volatility, whereas the adjacent vapor phase is dominated by a dense inert gas. To validate the analytical model and verify all exploited assumptions, the results are contrasted to large scale molecular dynamics simulations.

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Observations on the low temperature vaporization and envelope or wake flame burning of n-heptane droplets at reduced gravity during parabolic flights

Cited by 19 publications

References 10 publications

A numerical model for calculating the vaporization rate of a fuel droplet exposed to a convective turbulent airflow

A numerical model for calculating the vaporization rate of a fuel droplet exposed to a convective turbulent airflow

Subcritical and supercritical droplet evaporation within a zero-gravity environment: Low Weber number relative motion

Diffusion limited evaporation of a binary liquid film

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