Discrete multicomponent model for biodiesel spray combustion simulation

An important first step in spray combustion simulation is an accurate determination of the fuel properties which affects the modelling of spray formation and reaction. In a practical combustion simulation, the implementation of a multicomponent model is important in capturing the relative volatility of different fuel components. A Discrete Multicomponent (DM) model is deemed to be an appropriate candidate to model a composite fuel like biodiesel which consists of four components of fatty acid methyl esters (FAME). In this paper, the DM model is compared with the traditional Continuous Thermodynamics (CTM) model for both diesel and biodiesel. The CTM model is formulated based on mixing rules that incorporate the physical and thermophysical properties of pure components into a single continuous surrogate for the composite fuel. The models are implemented within the open-source CFD code OpenFOAM, and a semi-quantitative comparison is made between the predicted spray-combustion characteristics and optical measurements of a swirl-stabilised flame of diesel and biodiesel. The DM model performs better than the CTM model in predicting a higher magnitude of heat release rate in the top flame brush region of the biodiesel flame compared to that of the diesel flame. Using both the DM and CTM models, the simulation successfully reproduces the droplet size, volume flux, and droplet density profiles of diesel and biodiesel. The DM model predicts a longer spray penetration length for biodiesel compared to that of diesel, as seen in the experimental data. Also, the DM model reproduces a segregated biodiesel fuel vapour field and spray in which the most abundant FAME component has the longest vapour penetration. In the biodiesel flame, the relative abundance of each fuel component is found to dominate over the relative volatility in terms of the vapour species distribution and vice versa in the liquid species distribution. © 2014 Elsevier Ltd. All rights reserved.

Effect of chain-length dependence of interaction parameter on spinodals for polydisperse polymer blends

The chain-length dependence of the Flory-Huggins (FH) interaction parameter is introduced into the FH lattice theory for polydisperse polymer-blend systems. The spinodals are calculated for the model polymer blends with different chain lengths and distributions. It is found that all the related variables r(n), r(w), r(z), and chain-length distribution, have effects on the spinodals for polydisperse polymer blends.

Experimental and Modelling Studies of the Thermodynamics and Kinetics of Phase and Structural Transformations in a Gamma TiAl-based Alloy

This work combines microscopy, synchrotron radiation X-ray diffraction, differential scanning calorimetry and thermodynamic calculations in the characterisation of phase transformation behaviour of a Ti–46Al–1.9Cr–3Nb alloy upon continuous heating at constant rates. It has been found that the Ti–46Al–1.9Cr–3Nb alloy after being forged at 1200 °C without further treatment has a duplex microstructure consisting of fine equiaxed and lamellar ? grains with a small amount of a2 plates and particles and about 1 wt.% B2 phase. Differential scanning calorimetry revealed reproducibly several thermal effects upon heating of the as-forged alloy. These thermal effects are related to the equilibration and homogenisation of the sample, change of phase ratios between a2, ? and B2 phases in particular the increase of B2 in respect to a2 and ?, and the following five phase transformations: a2 + ? + B2 a + ? + B2, a + ? + B2 a + ?, ? + a a, a a + ß, a + ß a + ß + L. The observation of these transformations by differential scanning calorimetry is largely in agreement with literature phase diagrams and thermodynamic calculations, though care is needed to consider the different alloy compositions. Kinetics of the ? + a a phase transformation in the Ti–46Al–1.9Cr–3Nb alloy has been quantitatively derived from the calorimetry data, giving phase compositions at any point during the transformation upon continuous heating.

Thermodynamics, structure, and dynamics in room temperature ionic liquids: The case of 1-butyl-3-methyl imidazolium hexafluorophosphate ([bmim][PF6])

A detailed investigation of the phase diagram of 1-butyl-3-methyl imidazolium hexafluorophosphate ([bmim][PF6]) is presented on the basis of a wide set of experimental data accessing thermodynamic, structural, and dynamical properties of this important room temperature ionic liquid (RTIL). The combination of quasi adiabatic, continuous calorimetry, wide angle neutron and X-ray diffraction, and quasi elastic neutron scattering allows the exploration of many novel features of this material. Thermodynamic and microscopic structural information is derived on both glassy and crystalline states and compared with results that recently appeared in the literature allowing direct information to be obtained on the existence of two crystalline phases that were not previously characterized and confirming the view that RTILs show a substantial degree of order (even in their amorphous states), which resembles the crystalline order. We highlight a strong connection between structure and dynamics, showing the existence of three temperature ranges in the glassy state across which both the spatial correlation and the dynamics change. The complex crystalline polymorphism in [bmim][PF6] also is investigated; we compare our findings with the corresponding findings for similar RTILs. These results provide a strong experimental basis for the exploration of the features of the phase diagram of RTILs and for the further study of longer alkyl chain salts.

Note on ""Continuous matter creation and the acceleration of the universe: the growth of density fluctuations""

Recently, de Roany and Pacheco (Gen Relativ Gravit, doi:10.1007/s10714-010-1069-2) performed a Newtonian analysis on the evolution of perturbations for a class of relativistic cosmological models with Creation of Cold Dark Matter (CCDM) proposed by the present authors (Lima et al. in JCAP 1011:027, 2010). In this note we demonstrate that the basic equations adopted in their work do not recover the specific (unperturbed) CCDM model. Unlike to what happens in the original CCDM cosmology, their basic conclusions refer to a decelerating cosmological model in which there is no transition from a decelerating to an accelerating regime as required by SNe type Ia and complementary observations.

Modeling of continuous thermal processing of a non-Newtonian liquid food under diffusive laminar flow in a tubular system

The classic conservative approach for thermal process design can lead to over-processing, especially for laminar flow, when a significant distribution of temperature and of residence time occurs. In order to optimize quality retention, a more comprehensive model is required. A model comprising differential equations for mass and heat transfer is proposed for the simulation of the continuous thermal processing of a non-Newtonian food in a tubular system. The model takes into account the contribution from heating and cooling sections, the heat exchange with the ambient air and effective diffusion associated with non-ideal laminar flow. The study case of soursop juice processing was used to test the model. Various simulations were performed to evaluate the effect of the model assumptions. An expressive difference in the predicted lethality was observed between the classic approach and the proposed model. The main advantage of the model is its flexibility to represent different aspects with a small computational time, making it suitable for process evaluation and design. (C) 2012 Elsevier Ltd. All rights reserved.

Thermodynamics of aqueous biopolymer solutions and fractionation of Dextran

Flory-Huggins interaction parameters and thermal diffusion coefficients were measured for aqueous biopolymer solutions. Dextran (a water soluble polysaccharide) and bovine serum albumin (BSA, a water soluble protein) were used for this study. The former polymer is representative for chain macromolecules and the latter is for globular macromolecules. The interaction parameters for the systems water/dextran and water/BSA were determined as a function of composition by means of vapor pressure measurements, using a combination of headspace sampling and gas chromatography (HS-GC). A new theoretical approach, accounting for chain connectivity and conformational variability, describes the observed dependencies quantitatively for the system water/dextran and qualitatively for the system water/BSA. The phase diagrams of the ternary systems water/methanol/dextran and water/dextran/BSA were determined via cloud point measurements and modeled by means of the direct minimization of the Gibbs energy using the information on the binary subsystems as input parameters. The thermal diffusion of dextran was studied for aqueous solutions in the temperature range 15 < T < 55 oC. The effects of the addition of urea were also studied. In the absence of urea, the Soret coefficient ST changes its sign as T is varied; it is positive for T > 45.0 oC, but negative for T < 45.0 oC. The positive sign of ST means that the dextran molecules migrate towards the cold side of the fluid; this behavior is typical for polymer solutions. While a negative sign indicates the macromolecules move toward the hot side; this behavior has so far not been observed with any other binary aqueous polymer solutions. The addition of urea to the aqueous solution of dextran increases ST and reduces the inversion temperature. For 2 M urea, the change in the sign of ST is observed at T = 29.7 oC. At higher temperature ST is always positive in the studied temperature range. To rationalize these observations it is assumed that the addition of urea opens hydrogen bonds, similar to that induced by an increase in temperature. For a future extension of the thermodynamic studies to the effects of poly-dispersity, dextran was fractionated by means of a recently developed technique called Continuous Spin Fractionation (CSF). The solvent/precipitant/polymer system used for the thermodynamic studies served as the basis for the fractionation of dextran The starting polymer had a weight average molar mass Mw = 11.1 kg/mol and a molecular non-uniformity U= Mw / Mn -1= 1.0. Seventy grams of dextran were fractionated using water as the solvent and methanol as the precipitant. Five fractionation steps yielded four samples with Mw values between 4.36 and 18.2 kg/mol and U values ranging from 0.28 to 0.48.

Transforming the psychological contract through a continuous innovation methodology

This paper introduces the Corporate Culture Change Cycle: a continuous innovation methodology for transforming the psychological contract in an organisational context. The eight step process is based on the action learning model. The purpose of this methodology is to benchmark the psychological contract against eight changing values of the employment relationship as a basis for facilitating a process of aligning the changing needs of employer and employee. Both the Corporate Culture Change Cycle and the New Employment Relationship Model have been validated in several organisational settings and subsequently refined. This continuous innovation methodology addresses gaps in the psychological contract, change management and continuous innovation research literatures. The approach therefore should be of interest to researchers in these fields of study and from a practical perspective for managers wishing to transform their workplace cultures.