A Model for Droplet Vaporization for Use in Gasoline and HCCI Engine Applications

2004 ◽  
Vol 126 (2) ◽  
pp. 422-428 ◽  
Author(s):  
Youngchul Ra ◽  
Rolf D. Feitz
Keyword(s):  
Heat Flux ◽  
Internal Heat ◽  
Droplet Surface ◽  
Fuel Vapor ◽  
Gas Mixture ◽  
Ambient Temperatures ◽  
Droplet Vaporization ◽  
Flux Model ◽  
Heat Flux Model

A model for unsteady droplet vaporization is presented that considers the droplet temperature range from flash-boiling conditions to normal evaporation. The theory of continuous thermodynamics was used to model the properties and compositions of multicomponent fuels such as gasoline. In order to model the change of evaporation rate from normal to boiling conditions more realistically, an unsteady internal heat flux model and a new model for the determination of the droplet surface temperature is proposed. An explicit form of the equation to determine the heat flux from the surrounding gas mixture to the droplet-gas interface was obtained from an approximate solution of the quasi-steady energy equation for the surrounding gas mixture, with the inter-diffusion of fuel vapor and the surrounding gas taken into account. The model was applied to calculate evaporation processes of droplets for various ambient temperatures and droplet temperatures.

A Model for Droplet Vaporization for Use in Gasoline and HCCI Engine Applications

2002 ◽  
Author(s):  
Youngchul Ra ◽  
Rolf D. Reitz
Keyword(s):  
Heat Flux ◽  
Internal Heat ◽  
Droplet Surface ◽  
Fuel Vapor ◽  
Gas Mixture ◽  
Ambient Temperatures ◽  
Droplet Vaporization ◽  
Flux Model ◽  
Heat Flux Model

A model for unsteady droplet vaporization is presented that considers the droplet temperature range from flash-boiling conditions to normal evaporation. The theory of continuous thermodynamics was used to model the properties and compositions of multi-component fuels such as gasoline. In order to model the change of evaporation rate from normal to boiling conditions more realistically, an unsteady internal heat flux model and a new model for the determination of the droplet surface temperature is proposed. An explicit form of the equation to determine the heat flux from the surrounding gas mixture to the droplet-gas interface was obtained from an approximate solution of the quasi-steady energy equation for the surrounding gas mixture, with the inter-diffusion of fuel vapor and the surrounding gas taken into account. The model was applied to calculate evaporation processes of droplets for various ambient temperatures and droplet temperatures.

The application of a multicomponent droplet vaporization model to gasoline direct injection engines

2003 ◽  
Vol 4 (3) ◽  
pp. 193-218 ◽  
Author(s):  
Y Ra ◽  
R. D. Reitz
Keyword(s):  
Heat Flux ◽  
Present Model ◽  
Direct Injection ◽  
Internal Heat ◽  
Droplet Surface ◽  
Gasoline Direct Injection ◽  
Gas Mixture ◽  
Ambient Temperatures ◽  
Droplet Vaporization ◽  
Flash Boiling

A model for unsteady droplet vaporization is presented that considers the droplet temperature range from flash-boiling conditions to normal evaporation. The theory of continuous thermodynamics was used to model the properties and compositions of multicomponent fuels such as gasoline. In order to model the change of evaporation rate from normal to boiling conditions more realistically, an unsteady internal heat flux model and a new model for the determination of the droplet surface temperature are proposed. An explicit form of the equation to determine the heat flux from the surrounding gas mixture to the droplet/gas interface was obtained from an approximate solution of the quasi-steady energy equation for the surrounding gas mixture, with the interdiffusion of fuel vapour and the surrounding gas taken into account. The model was applied to calculate normal and boiling evaporation processes of droplets for various ambient temperatures and droplet temperatures. Single-droplet evaporation calculated using the present model was compared with the results calculated by using the standard evaporation routine of the KIVA-3V code. Also, simulations of the vaporization of a single-component fuel (iso-octane) were compared with multi-component fuel cases. The vaporization of a hollow cone spray of fuel injected into a cylindrical chamber was simulated for both normal and flash-boiling conditions using the KIVA-3V code implemented with the present model. In addition, the model was applied to a realistic gasoline direct injection engine.

Fuel Droplet Evaporation in a Supercritical Environment

2002 ◽  
Vol 124 (4) ◽  
pp. 762-770 ◽  
Author(s):  
G. S. Zhu ◽  
S. K. Aggarwal
Keyword(s):  
Experimental Data ◽  
Phase Equilibrium ◽  
Ambient Pressure ◽  
Droplet Surface ◽  
Fuel Vapor ◽  
Phase Solubility ◽  
Liquid Density ◽  
Ambient Temperatures ◽  
Droplet Vaporization ◽  
Wide Range

This paper reports a numerical investigation of the transcritical droplet vaporization phenomena. The simulation is based on the time-dependent conservation equations for liquid and gas phases, pressure-dependent variable thermophysical properties, and a detailed treatment of liquid-vapor phase equilibrium at the droplet surface. The numerical solution of the two-phase equations employs an arbitrary Eulerian-Lagrangian, explicit-implicit method with a dynamically adaptive mesh. Three different equations of state (EOS), namely the Redlich-Kwong (RK), the Peng-Robinson (PR), and Soave-Redlich-Kwong (SRK) EOS, are employed to represent phase equilibrium at the droplet surface. In addition, two different methods are used to determine the liquid density. Results indicate that the predictions of RK-EOS are significantly different from those obtained by using the RK-EOS and SRK-EOS. For the phase-equilibrium of n-heptane-nitrogen system, the RK-EOS predicts higher liquid-phase solubility of nitrogen, higher fuel vapor concentration, lower critical-mixing-state temperature, and lower enthalpy of vaporization. As a consequence, it significantly overpredicts droplet vaporization rates, and underpredicts droplet lifetimes compared to those predicted by PR and SRK-EOS. In contrast, predictions using the PR-EOS and SRK-EOS show excellent agreement with each other and with experimental data over a wide range of conditions. A detailed investigation of the transcritical droplet vaporization phenomena indicates that at low to moderate ambient temperatures, the droplet lifetime first increases and then decreases as the ambient pressure is increased. At high ambient temperatures, however, the droplet lifetime decreases monotonically with pressure. This behavior is in accord with the reported experimental data.

Fuel Droplet Evaporation in a Supercritical Environment

1999 ◽  
Author(s):  
G. S. Zhu ◽  
S. K. Aggarwal
Keyword(s):  
Experimental Data ◽  
Phase Equilibrium ◽  
Ambient Pressure ◽  
Droplet Surface ◽  
Fuel Vapor ◽  
Phase Solubility ◽  
Liquid Density ◽  
Ambient Temperatures ◽  
Droplet Vaporization ◽  
Wide Range

This paper reports a numerical investigation of the transcritical and supercritical droplet vaporization phenomena. The simulation is based on the time-dependent conservation equations for liquid and gas phases, pressure-dependent variable thermophysical properties, and a detailed treatment of liquid-vapor phase equilibrium at the droplet surface. The numerical solution of the two-phase equations employs an arbitrary Eulerian-Lagrangian, explicit-implicit method with a dynamically adaptive mesh. Three different equations of state (EOS), namely the Redlich-Kwong (RK), the Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) EOS, are employed to represent phase equilibrium at the droplet surface. In addition, two different methods are used to determine the liquid density. Results indicate that the predictions of RK-EOS are significantly different from those obtained by using the RK-EOS and SRK-EOS. For the phase-equilibrium of n-heptane-nitrogen system, the RK-EOS predicts higher liquid-phase solubility of nitrogen, higher fuel vapor concentration, lower critical-mixing-state temperature, and lower enthalpy of vaporization. As a consequence, it significantly overpredicts droplet vaporization rates, and underpredicts droplet lifetimes compared to those predicted by PR- and SRK-EOS. In contrast, predictions using the PR-EOS and SRK-EOS show excellent agreement with each other and with experimental data over a wide range of conditions. A detailed investigation of the transcritical droplet vaporization phenomena indicates that at low to moderate ambient temperatures, the droplet lifetime first increases and then decreases as the ambient pressure is increased. At high ambient temperatures, however, the droplet lifetime decreases monotonically with pressure. This behavior is in accord with the reported experimental data.

Research on Heat Flux Distribution in Deep Grinding

2008 ◽  
Author(s):  
D. H. Zhu ◽  
B. Z. Li ◽  
J. G. Yang
Keyword(s):  
Heat Flux ◽  
Flux Distribution ◽  
Theoretical Expression ◽  
Uniform Heat Flux ◽  
Heat Transfer Mechanism ◽  
Heat Flux Distribution ◽  
Workpiece Surface ◽  
Quadratic Curve ◽  
Flux Model ◽  
Heat Flux Model

This paper studies the heat transfer mechanism in deep grinding process, especially the heat flux to the workpiece. On the basis of triangle moving heat source, a quadratic curve heat flux model in the grinding zone was developed to determine the heat flux distribution and to estimate the surface temperature of workpiece. From the calculated theoretical expression of heat flux to the workpiece, the quadratic curve heat flux can be understood as the superposition of square law heat flux, triangular heat flux and uniform heat flux in the grinding zone. Then four heat flux models using the determined amount of heat flux were applied to estimate the workpiece surface temperatures which were compared with that measured by the embedded thermocouple. It has been found that the quadratic curve heat flux distribution seems to give the best match with measured and theoretical temperature, although square law heat flux model is good enough to predict the temperature.

Numerical study of Carreau nanofluid flow past vertical plate with the Cattaneo–Christov heat flux model

2019 ◽  
Vol 29 (2) ◽  
pp. 702-723 ◽  
Author(s):  
Vasu B. ◽  
Atul Kumar Ray
Keyword(s):  
Heat Flux ◽  
Brownian Motion ◽  
Weissenberg Number ◽  
Motion Parameter ◽  
Conduction Model ◽  
Content Type ◽  
Carreau Nanofluid ◽  
Flux Model ◽  
Heat Flux Model ◽  
Brownian Motion Parameter

PurposeTo achieve material-invariant formulation for heat transfer of Carreau nanofluid, the effect of Cattaneo–Christov heat flux is studied on a natural convective flow of Carreau nanofluid past a vertical plate with the periodic variations of surface temperature and the concentration of species. Buongiorno model is considered for nanofluid transport, which includes the relative slip mechanisms, Brownian motion and thermophoresis.Design/methodology/approachThe governing equations are non-dimensionalized using suitable transformations, further reduced to non-similar form using stream function formulation and solved by local non-similarity method with homotopy analysis method. The numerical computations are validated and verified by comparing with earlier published results and are found to be in good agreement.FindingsThe effects of varying the physical parameters such as Prandtl number, Schmidt number, Weissenberg number, thermophoresis parameter, Brownian motion parameter and buoyancy ratio parameter on velocity, temperature and species concentration are discussed and presented through graphs. The results explored that the velocity of shear thinning fluid is raised by increasing the Weissenberg number, while contrary response is seen for the shear thickening fluid. It is also found that heat transfer in Cattaneo–Christov heat conduction model is less than that in Fourier’s heat conduction model. Furthermore, the temperature and thermal boundary layer thickness expand with the increase in thermophoresis and Brownian motion parameter, whereas nanoparticle volume fraction increases with increase in thermophoresis parameter, but reverse trend is observed with increase in Brownian motion parameter.Originality/valueThe present investigation is relatively original as very little research has been reported on Carreau nanofluids under the effect of Cattaneo–Christov heat flux model.

Sign in / Sign up

Export Citation Format

Share Document