A. La Rocca

A double boundary collocation Hermitian approach for the solution of steady state convection-diffusion problems

In this article a double boundary collocation approach based on the meshless radial basis function Hermitian method (symmetric method) is proposed and compared with the conventional single collocation. In the double boundary collocation approach, at the boundary collocation points the boundary condition and the governing partial differential equation are required to be satisfied simultaneously instead of only the boundary condition as required in the single collocation. We are able to carry out this type of algorithm due to the robustness of the proposed Hermite interpolation scheme, in which the resulting matrix will be non-singular as long as the partial differential operators applied to each point are linearly independent, even if in a single node we impose two different differential conditions. The results obtained with this new method are characterized by a higher precision especially for the prediction of the fluxes at the boundaries. This is due to the higher order of continuity of the approximation at the boundary points imposed by the double collocation.

The effectiveness of stop-start and thermal management measures to improve fuel economy

Measures to reduce fuel consumption penalties associated with idling and cold engine operation have been have been investigated through experimental and computational simulation studies. The experimental work was carried out on a 1.6l, 4 cylinder SI engine. In cold-started New European Drive Cycle (NEDC) simulations of the engine in a B Class vehicle, stop-start strategies to eliminate idle fuel consumption was most effective, improving fuel economy by a predicted 7.7%. Minimising the time a switchable coolant pump was on saves up to 1% through reduced parasitic work. In warm up tests at constant speed and load, using a hot coolant store to reintroduce hot coolant on or before start-up reduced fuel consumption by 2.3% over 500s. Encapsulating the engine and power take off with thermal insulation slows cool-down from previous engine running and gives a higher restart temperature. Depending on the restart temperature, the fuel saving over the NEDC can be several per cent.

Soot-in-Oil 3D Volume Reconstruction Through the Use of Electron Tomography: An Introductory Study

Understanding soot nanoparticle interaction with oil additives and the causes of soot-induced thickening would assist in lubricant formulation, prolonging engine life and improving engine efficiency. Three-dimensional measurement of soot structures is currently not undertaken as established techniques are limited to two dimensions. While they give valuable information on the structure and reactivity of soot nanoparticles, it is not easy to correlate this to geometry of primary particles and agglomerates. In this work, we investigate the development and application of 3D-TEM for characterisation of soot agglomerates as a new capability to yield information on the volumetric character of fractal nanoparticles. This investigation looks at the feasibility for volume reconstruction of nanometric soot particles in used engine oil from multiple imaging at different tilt angles. Bright-field TEM was used to capture two-dimensional images of soot. Heptane and diethyl ether washes were used to remove volatile contaminants and allowed for images from −60° to +60° tilt with no sign of carbon build-up to be acquired. Tomographic reconstruction from the aligned tilt-series images based on weighted back-projection algorithm has yielded useful information about complex soot nanoparticle size. Estimation of soot mass in oil by nanoparticle tracking analysis (NTA) can be considerably improved by taking into account the three-dimensional shape of the soot agglomerate including the shape factor in the calculations. 3D-TEM measurements were compared with values calculated by using a single-sphere approach when tracking nanoparticles moving under Brownian motion. A shape factor was calculated, dividing the surface area and volume calculated using spherical geometrical estimates, by the respective values calculated using the 3D models. The spherical model of the particle is found on average to overestimate the surface area by sevenfold, and the volume to the actual soot agglomerate by 23 times. Applying the calculated shape factor as a correction reduces the NTA overestimation by one order of magnitude.

Mechanical and thermal design of an aeroengine starter/generator

The paper describes the mechanical and thermal design of a high speed, high power density synchronous permanent magnet machine for an aero engine starter generator system with a power rating of 150 kW and maximum speed of 32,000 rpm. The electrical machine is designed to minimise the weight and maximise the efficiency so both mechanical and thermal aspects are considered. The cooling strategy adopts an inner stator sleeve for enhanced cooling of the stationary components whilst minimising the windage loss. Finite Element Analysis (FEA) is used for the static structural analyses of critical components of the machine and the dynamic performance of the rotating shaft. Heat transfer phenomena are also investigated by the means of Computational Fluid Dynamics (CFD) and Lumped Parameter Thermal Network (LPTN) for the optimisation of the proposed cooling arrangement and prediction of the machine temperature distribution.

Symmetric radial basis function meshless approach for time dependent PDEs

This work present a meshless numerical approach for the solution of initial value problems of time dependent Partial Differential Equations in terms of a symmetric radial basis function interpolation scheme. Numerical examples showing the performance of the scheme for two different problems are given.

The initiation and development of combustion under cold idling conditions using a glow plug in diesel engines

Factors determining the success or failure of combustion initiation using a glow plug have been investigated through experimental work on a single cylinder, common rail diesel engine with a geometric compression ratio of 15.5, and a quiescent combustion bomb with optical access. A glow plug was required to avoid engine misfires when bulk gas temperature at the start of injection was less than 413 °C. The distance between the glow plug and the spray edge, the glow plug temperature, and the bulk gas temperature were important factors in meeting two requirements for successful ignition: a minimum local temperature of 413 °C and a minimum air/fuel vapour equivalence ratio of 0.15–0.35.

TEM and HRTEM of Soot-in-oil particles and agglomerates from internal combustion engines

Over time, the performance of lubricating oil in a diesel engine is affected by the build-up of carbon soot produced by the combustion process. TEM and HRTEM are commonly used to investigate the characteristics of individual and agglomerated particles from diesel exhaust, to understand the structure and distribution of the carbon sheets in the primary particles and the nanostructure morphology. However, high resolution imaging of soot-in-oil is more challenging, as mineral oil is a contaminant for the electron microscope and leads to instability under the electron beam. In this work we compare solvent extraction and centrifugation techniques for removing the mineral oil contaminant, and the effect on particle size distribution.

Progress towards a methodology for high throughput 3D reconstruction of soot nanoparticles via electron tomography: PROGRESS TOWARDS HIGH THROUGHPUT 3D RECONSTRUCTION OF SOOT NANOPARTICLES

The aim of this work is to make progress towards the development of 3D reconstruction as a legitimate alternative to traditional 2D characterization of soot. Time constraints are the greatest opposition to its implementation, as currently reconstruction of a single soot particle takes around 5–6 h to complete. As such, the accuracy and detail gains are currently insufficient to challenge 2D characterization of a representative sample (e.g. 200 particles). This work is a consideration of the optimization of the steps included within the computational reconstruction and manual segmentation of soot particles. Our optimal process reduced the time required by over 70% in comparison to a typical procedure, whilst producing models with no appreciable decrease in quality.

Thermal management of a high speed permanent magnet machine for an aeroengine

The paper describes the mechanical and thermal design of a high speed, high power density synchronous permanent magnet machine for an aero engine starter generator system with a power rating of 150 kW and maximum speed of 32,000 rpm. As both mechanical and thermal aspects have a direct impact on machine overall performance and weight reduction, a critical design optimisation was carried out. Intensive cooling is guaranteed by direct liquid oil-cooling of stationary components; a stator sleeve is also introduced into the airgap to prevent excessive windage. Thermal investigations were carried out by the means of Computational Fluid Dynamics (CFD) and Lumped Parameter Thermal Network (LPTN) analyses. Experimental validation also allowed the identification of most critical machine temperatures and the validation of the models developed. Finite Element Analysis (FEA) is used for the static structural analyses of the stator sleeve.

Modelling heat transfer-controlled cooling and freezing times: a comparison between computational values and experimental results

Modelling of heat transfer-controlled cooling and freezing time predictions are very important for a good preservation of foodstuffs. In that regard, we used a computer code based on the finite-element method that allowed us to analyse the phase-change of various foodstuffs during their freezing. The model was exercised to predict process times. The results can be used to design high efficiency plants. In this work, the results predicted by the FEM program are compared with the experimental values given in technical literature.