Advanced models of fuel droplet heating and evaporation

Hong

2016

Energy

Ethanol direct injection plus gasoline port injection (EDI+GPI) is a new technology to utilise ethanol fuel more effectively and efficiently in spark-ignition engines by taking the advantages of ethanol fuel and direct injection, such as the cooling effect and anti-knock ability. A full cycle numerical modelling including both port and direct injection sprays was performed to understand the mechanisms behind the experimental results of the EDI+GPI engine. The turbulence-chemistry interaction of the two-fraction-mixture partially premixed combustion was solved by a five-dimensional presumed Probability Density Function table.Effects of direct injection timing on fuel evaporation, mixing, wall-wetting, combustion and emission processes were investigated. The results showed that when the direct injection timing was retarded, the mixture around the spark plug became leaner and the distribution of equivalence ratio became more uneven.Moreover, late direct injection resulted in severe fuel impingement and caused local over-cooling effect and over-rich mixture. Consequently, the combustion speed and temperature were decreased by retarded direct injection timing, leading to reduced NO emission and increased HC and CO emissions. Finally, numerical modelling was performed to investigate the strategy of injecting small amount of ethanol fuel on reducing the fuel impingement and incomplete combustion caused by late direct injection.

Section: Resultsmentioning

confidence: 99%

Section: D Engine Modelmentioning

confidence: 99%

Effect of injection timing on mixture formation and combustion in an ethanol direct injection plus gasoline port injection (EDI+GPI) engine

Hong

2016

Energy

“…Our analysis is based on the analytical solutions to the one-dimensional heat conduction and species diffusion equations inside spherically-symmetric droplets implemented in the numerical code [25,28,12].…”

Section: Liquid Heat and Mass Transfermentioning

confidence: 99%

“…In [3,25], it was pointed out that the effects of finite thermal conductivity and recirculation inside the droplets need to be taken into account in modelling droplet heating and evaporation. The simplest approach to doing this can be based on the application of the Effective Thermal Conductivity (ETC) model [28,29].…”

mentioning

confidence: 99%

Modelling of heating and evaporation of gasoline fuel droplets: A comparative analysis of approximations

Elwardany¹,

Sazhin²,

Farooq³

2013

Fuel

Modelling of gasoline fuel droplet heating and evaporation processes is investigated using several approximations of this fuel. These are quasi-components used in the quasi-discrete model and the approximations of these quasi-components (Surrogate I (molar fractions: 83.0% n-C 6 H 14 + 15.6% n-C 10 H 22 + 1.4% n-C 14 H 30 ) and Surrogate II (molar fractions: 83.0% n-C 7 H 16 + 15.6% n-C 11 H 24 + 1.4% n-C 15 H 32 )). Also, we have used Surrogate A (molar fractions: 56% n-C 7 H 16 + 28% iso-C 8 H 18 + 17% C 7 H 8 ) and Surrogate B (molar fractions: 63% n-C 7 H 16 + 20% iso-C 8 H 18 + 17% C 7 H 8 ), originally introduced based on the closeness of the ignition delay of surrogates to that of gasoline fuel. The predictions of droplet radii and temperatures based on three quasi-components and their approximations (Surrogates I and II) are shown to be much more accurate than the predictions using Surrogates A and B.

Engineering Applications of Computational Fluid Mechanics

“…Dobry et al (2009) emphasized the importance of mass and heat transfer in studying the drying of active soluble ingredients, and Mezhericher, Levy, and Borde (2009) used a CFD model to show droplet drying using an Eulerian-Lagrangian method. Other studies include those of Gjesing, Hattel, and Fritsching (2009), Ruiz-López, Ruiz-Espinosa, Luna-Guevara, and García-Alvarado (2011), and Sazhin (2006).…”

Section: Introductionmentioning

confidence: 99%

CFD simulations of polymer devolatilization in steam contactors

Gabor

Shindle

Chandy

2017

Removal of volatiles and other unwanted products in a polymer mix is a critical step in polymer manufacturing. This process serves many purposes, such as improvement in the physical and chemical properties of the polymer, elimination of odours, recovery of monomers and solvents, and fulfilment of environmental regulations. In this study, the mixture of polymer and solvent, or cement, is mixed with superheated steam which causes the unwanted solvent to evaporate. As the cement droplets lose solvent and dry out, they are ejected as cement 'crumb' from the mixing device. This process is modelled using computational fluid dynamics (CFD) to gain insight into the complex phenomena. The model simulates the heat transfer and phase changes associated with cement and steam, via 3D axisymmetric calculations. Using an Eulerian-Lagrangian approach, the superheated steam is modelled as the continuous phase and tracked in an Eulerian frame, while the cement droplets are treated using a Lagrangian tracking method, thus as a whole allowing us to track the particle sizes, temperatures, and solvent content. Furthermore, a parametric study is carried out to analyse the effect of initial polymer temperature on final polymer product. The simulation is carried out with three different initial polymer temperatures and the resulting solvent concentration, and the size of the cement particles between the three cases are compared. By increasing the cement operating temperature, the solvent concentration in the cement crumb is significantly lower, and the final cement crumb sizes shows a slight decrease, which indicates better production performance. Indeed, full 3D CFD calculations, presented to verify the axisymmetric assumption, show differences in the particle statistics, which could have implications for design considerations. Such studies can provide further insights into control parameters that can potentially enhance the efficiency of such a manufacturing process. ARTICLE HISTORY