Development of a conjugate heat transfer solver

The current research study presents a numerical approach in modelling the conjugate heat transfer system of the gas-turbine rotating discs-cavities. The work was undertaken to understand such phenomena and, more specifically, to numerically investigate the thermal interactions in rotating discs-cavities. The developed solver is capable of dealing with complex heat transfer problems, such as unsteady three-dimensional compressible rotating-flows. The development was based on integrating an inhouse computational fluid dynamics code (SURF) with a heat conduction solver internally. Method of interpolation using mapped area was also introduced for treating non-matching meshes at interface, which plays an effective role in exchanging boundary data. This thesis also documents the development of a numerical finite volume cell-vertex hybrid edgebased heat conduction code by the author using FORTRAN. The heat conduction solver was developed and validated to deal with three dimensional solid-domains using unstructured elements. The validation process was carried out on several test cases for investigating the temperature distribution. The test results were presented to show good agreement with the analytical, experimental and other commercial numerical solutions where they exist

Modelling of droplet heating and evaporation: an application to biodiesel, gasoline and Diesel fuels

This paper presents our recent progress in the modelling of automotive fuel droplet heating and evaporation processes in conditions close to those in internal-combustion engines. Three types of automotive-fuels are considered: biodiesel, gasoline and Diesel fuels. Modelling of biodiesel fuel droplets is based on the application of the Discrete Component (DC) model. A distinctive feature of this model is that it is based on the analytical solutions to the transient heat conduction and species diffusion equations in the liquid phase, taking into account the effects of recirculation. The application of the DC model to fossil fuels (containing potentially hundreds of components), however, is computationally expensive. The modelling of these fuels is based on the recently introduced Multi-Dimensional Quasi-Discrete (MDQD) model. This model replaces large number of components in Diesel and gasoline fuels with a much smaller number of components/quasi-components without losing the main features of the original DC model. The MDQD model is shown to accurately predict the droplet temperatures and evaporation times and to be much more computationally efficient than the DC model. The main features of these models and their applications to automotive fuel droplets are summarised and discussed

A Hydro-Powered Climate-Neutral Pump:Full Cycle Simulation and Performance Evaluation

This paper presents a parametric study of the multistorey hydro-powered pump, known as ‘Bunyip’, which has demonstrated significant potential in contributing to rural regions. The study is aimed at understanding the underlying physics of the system and ways to enhance its hydraulic performance. A transient three-dimensional model using the commercial Computational Fluid Dynamics (CFD) tool Ansys-Fluent is utilized to gain insights into its fundamental flow mechanics, operational efficiency, standard capacity, and relative delivery. The investigation involves an initial assessment of performance for three Bunyip devices based on manufacturing data. A parametric analysis is conducted for the dataset generated through meticulous application and numerical modelling. The CFD results are validated against experimental data. Three main design configurations are considered, and 58 sets of varied input parameters are examined. The best design configuration is evaluated against five cases of conventional hydro-power pump systems. The results indicate that a smaller diameter of the pressure chamber and a higher supply head lead to higher pressure, achieving a target head of 3 m with 15% efficiency and a flowrate of 11.82 L/min

Blended E85-diesel fuel droplet heating and evaporation

The multidimensional quasi-discrete (MDQD) model is applied to the analysis of heating and evaporation of mixtures of E85 (85 vol % ethanol and 15 vol % gasoline) with diesel fuel, commonly known as “E85–diesel” blends, using the universal quasi-chemical functional group activity coefficients model for the calculation of vapor pressure. The contribution of 119 components of E85–diesel fuel blends is taken into account, but replaced with smaller number of components/quasi-components, under conditions representative of diesel engines. Our results show that high fractions of E85–diesel fuel blends have a significant impact on the evolutions of droplet radii and surface temperatures. For instance, droplet lifetime and surface temperature for a blend of 50 vol % E85 and 50 vol % diesel are 23.2% and up to 3.4% less than those of pure diesel fuel, respectively. The application of the MDQD model has improved the computational efficiency significantly with minimal sacrifice to accuracy. This approach leads to a saving of up to 86.4% of CPU time when reducing the 119 components to 16 components/quasi-components without a sacrifice to the main features of the model

Auto-selection of quasi-components/components in the multi-dimensional quasi-discrete model

A new algorithm for the auto-selection of quasi-components and components (QC/Cs) in the ‘multi-dimensional quasi-discrete’ model is suggested. This algorithm is applied to the analysis of heating and evaporation of multi-component fuel droplets. It allows one to automatically select QC/Cs and update the initial selection during droplet evaporation. The new algorithm is expected to be applicable to the analysis of a wide range of fuels and fuel blends. It can be directly implemented into CFD codes with minimal intervention by end-user. Using this algorithm, the effects of transient diffusion of species on droplet lifetimes are investigated for mixtures of Diesel and E85 (85% vol. ethanol and 15% vol. gasoline) fuels. It is shown that the new algorithm can reduce the analysis of the E85-Diesel fuel droplets, taking into account the contributions of up to 119 components at the initial stage of heating and evaporation, to that based on 5 QC/Cs, near the end of droplet evaporation, with up to 1.9% errors in predicted droplet temperatures and radii. The CPU time needed to perform calculations using the new algorithm is shown to be 80% less than that when considering the full composition of fuel.<br/