Browsing by Author "Floweday, Gareth"

Now showing 1 - 10 of 10
  • Thumbnail Image
    Item
    Open Access
    25cc HCCI engine fueled with Diethyl Ether
    (2009) Lemberger, Ian; Floweday, Gareth; Yates, Andrew
    This research forms part of an ongoing HCCI study at the SASOL Advanced Fuels Laboratory to investigate and understand engine configuration and fuel chemistry effects on combustion in HCCI engines. This project continues from a previous project where a small Progress Aero Works (PAW) 6.5cc high speed model "diesel" aeroplane engine was found to operate in HCCI mode with surprising ease and flexibility. A 25cc, four-stroke, single cylinder Honda GX25 engine, possessing 2-valves with an overhead cam and separate oil sump lubrication system was used. This research aimed to provide insight with respect to which engine characteristics such as size, heat transfer, speed and fuel blending effects, play the primary role in operational differences between the Honda GX25, conventional HCCI engines and the remarkable operational flexibility of the PAW engine.
  • Thumbnail Image
    Item
    Open Access
    A CFD study of fuel evaporation and related thermofluid dynamics in the inlet manifold, port and cylinder of the CFR octane engine
    (2012) Thiart, Anja; Floweday, Gareth; Meyer, CM
    Spark Ignition (SI) engine fuels' anti-knock properties are measured in the Co-operative Fuel Research (CFR) engine under two different test conditions as prescribed by the American Society for Testing and Materials (ASTM) for Research Octane Number (RON) and Motor Octane Number (MON) ratings. Recent research has been focused on determining whether the numerical difference between RON and MON, known as Octane Sensitivity (OS), is a result of the chemical or physical properties of the fuel. The present research examined the effect that the operating environment has on fuel evaportion, and thus OS, in the CRF engine.
  • Thumbnail Image
    Item
    Open Access
    Combustion characteristics of synthetic gasoline in modern charge boosted GDI Engines
    (2015) Rockstroh, Manuel Tobias; Yates, Andrew; Floweday, Gareth
    Sasols synthetically derived gasoline blending components have traditionally been combined predominantly according to process economics to formulate commercial fuel blends that meet in-house fit-for-purpose requirements and the legislated fuel specifications in South Africa. In this study the potential for optimisation of a fuel blend using full boiling range synthetic blending components to enhance its performance in a modern charge boosted gasoline direct injection engine was investigated. An evaluation of detailed analytical fuel chemistry data was conducted followed by laminar ame speed experiments in a constant-volume combustion bomb apparatus in order to characterise the combustion behaviour of the blending components according to their characteristic chemical properties. A matrix of test fuels was established by splash blending the synthetic components with a commercial synthetic reference fuel. The performance of the fuels was subsequently evaluated using a modern, charge boosted, single cylinder GDI research engine. While the engine operation was verified to be in the negative-K region using model fuel components, anomalies in de fining the K-value using the synthetic blends were discovered. A fuel blending model was composed to allow prediction of linear and non-linear fuel properties of user de fined synthetic blend ratios. By integrating an engine performance test fuel scoring system, the model could be used to de fine optimal fuel blends through selection of a desired performance criterion while constraining the optimisation process to adhere to the national legislated gasoline specifications. Four final fuel blends were optimised according to best power output, gravimetric specific fuel consumption, volumetric specific fuel consumption and specific legislated emissions. A fifth blend was optimised for highest power output with no regard for fuel property specifications other than Reid vapour pressure. The performance of the optimised blends was evaluated on the test engine and the results indicated the potential to positively affect the performance characteristics of a synthetic fuel blend for use in a modern spark ignition engine. This study demonstrates a methodology for optimisation of a synthetic fuel to user-selected performance criteria and it is believed that this work represents a novel and valuable contribution to this field.
  • Thumbnail Image
    Item
    Open Access
    Design, set up and commissioning of a test facility for smokeless rich diesel combustion research
    (2015) King, Timothy Cole; Floweday, Gareth
    Low Temperature Combustion (LTC) is a strategy that harnesses the properties of exhaust gas, through the use of large quantities of exhaust gas recirculation (EGR), to reduce the peak combustion temperatures below that favoured by the formation processes of oxides of nitrogen (Ox) and those of soot. There is interest within the fuels research community in investigating the effects of diesel fuel formulations on LTC, using a suitable engine test platform. The objective of this study was to design and set up a test apparatus capable of achieving LTC in a diesel research engine, that could subsequently be used to study LTC behaviour with different fuels. In addition, it was necessary to present test data demonstrating the engine's performance, in terms of engine-out emissions and indicated specific fuel consumption (ISFC), transitioning between conventional diesel combustion (CDC) and LTC. The mechanical, electrical and control requirements for attaining CDC and LTC conditions were investigated in the literature and through consultations with experts in the fuels research field. These requirements were distilled into a definitive System Requirement Specification.
  • Thumbnail Image
    Item
    Open Access
    Implementation of a fully variable valve actuation valvetrain
    (2011) Jaffa, Steven; Floweday, Gareth
    In January 2008 the Sasol (Pty) Ltd Advisory Board identified that the Sasol Advanced Fuels Laboratory's (SAFL) single cylinder research engine was not in line with the current engine technologies, in particular Fully Variable Valve Actuation (FVVA). This project represented the first stage of the engine upgrade, which was to modify the current single cylinder engine to interface with pneumatic valve actuators and a fully configurable Engine Control Unit (ECU).
  • Thumbnail Image
    Item
    Open Access
    Modification of an ignition quality tester and its use in characterizing middle distillate fuels
    (2015) Ehrenreich, Aidan Lloyd; Floweday, Gareth; Schaberg, Paul
    The Ignition Quality Tester ( IQTTM ) is a constant volume combustion chamber based device which is used to determine the derived cetane number of diesel fuel oils when used in conjunction with ASTM D6890. During a test, the fuel sample is injected into heated, pressurised gas where it combusts. Suitable measurements are made during the combustion event to determine the ignition delay of the fuel and the latter is used with a correlation to determine the derived cetane number of the sample. The IQT offers improved repeatability and reproducibility when compared with the conventional method of determining cetane number, namely ASTM D613. Despite these advantages, the device features a fuel injection system not indicative of the state of the art, in terms of direct injection diesel components and associated fuel spray behavior. Therefore this project sought to make suitable mechanical, electrical and control modifications to incorporate a more technologically appropriate injector. It is believed that by improving the spray characteristics of the IQT along with the incorporation of a flexible control system, that it can be leveraged to a greater extent in a fuels research context. The modifications made to the system included the incorporation of a single hole common rail diesel injector along with a custom control system. The control system allowed flexible control of all variables considered to be significant to the study of auto-ignition delays. Additionally, an optical sensor was added to detect luminous emissions from the reacting fuels. The modified system was used to rate diesel fuels with varied composition including solvents, diesel primary reference fuels, crude derived as well as Low Temperature Fischer Tropsch (LTFT) products. These tests were performed at two temperatures and oxygen concentrations and the resulting data was used to redevelop correlations between the cetane number of the respective samples and their ignition delays in order to surmise the optimal operating conditions of the modified IQT.
  • Thumbnail Image
    Item
    Open Access
    A multi-zone model of the CFR engine : investigating cascading autoignition and octane rating
    (2011) Perumal, Marlan; Floweday, Gareth
    The CFR engine is the standardised research engine used for the measurement of knock resistance of fuels through the Research Octane Number (RON) and Motor Octane Number(MON) tests. In standard production engines, knock manifests as an almost instantaneous pressure rise followed by knock ringing" pressure oscillations of similar magnitude. However, knock in the CFR engine is characterised, and measured by, a steep, but more gradual pressure rise, followed by ringing of much lesser magnitude. It has been previously proposed that a cascading autoignition", resulting from an in-cylinder temperature gradient, is responsible for this unique pressure development.
  • Thumbnail Image
    Item
    Open Access
    A thermo-mechanical finite element simulation of hot rolling for the prediction of roll forces
    (2001) Floweday, Gareth; Knutsen, Robert D
    The main objective of this project was to provide Cooumbus Stainless (Mpumalanga, RSA) with a numerical stimulation model that would be able to accurately predict roll forces in the roughing mill. The materials used in the model is AISI 304 stainless steel. In order to model the material flow stress accurately, uniaxial compression testing was conducted in the temperature range of 800-1250° at intervals of 50°C. The strain rates tested were 35, 10, 3.5, 1.0, 0.35, 0.1, 0.01s-1 and each temperature was tested within each strain rate. Stress curves were fitted to an equation to give stress as a function of strain, strain rate temperature. The model was constructed as a 2D, seven pass thermo-mechanical model using Abaqus Explicit version 6.2.1. The billet was modelled using 6250, 4 noded plane strain elements. The model used a basic Coulomb Friction model with a specified maximum value of friction before shearing of the billet material took place. The roller was modelled as a rigid body.
  • Thumbnail Image
    Item
    Open Access
    Two contrasting approaches to auto-ignition modelling for HCCI engines
    (2010) Floweday, Gareth; Yates, Andrew
    This body of work entailed the broad contrasting of two hydrocarbon fuel auto-ignition models formulated for the emulation of combustion dynamics in Homogeneous Charge Compression Ignition (HCCI) engines. The first (empirical) auto-ignition model was adapted from its previously published form, for HCCI engine model implementation. This model was then combined with an explicit, single zone, thermodynamic engine model in order to investigate combustion phasing control strategies over a wide range of engine design parameters, experimental conditions and hydrocarbon fuels. This investigation yielded new techniques for HCCI combustion phasing control using convergent control parameter values and operation along curves of constant combustion phasing. These techniques were validated experimentally using two HCCI engines of novel design. The second (functional global) auto-ignition model was formulated in this study, drawing on an analysis of chemical kinetic schematics, a detailed auto-ignition behavioural study and a critical evaluation of existing global auto-ignition models. The performance of this new functional global model was evaluated using detailed chemical kinetic simulation data for a variety of hydrocarbon fuels, across a wide range of experimental conditions. The two studies, although different in approach and scope, enabled a broad and detailed comparison of the two auto-ignition models, thereby highlighting their respective values and limitations. The two models were shown to each possess particular advantages in the context of HCCI auto-ignition modelling, which were unmatched by existing models of similar classification. The models were also shown to exhibit individual drawbacks which played to each other's strengths. Both models were shown to be configurable to real world, full boiling range fuels and were designed to accurately emulate the dynamics of two-stage auto-ignition with excellent computational efficiency. These two hydrocarbon fuel auto-ignition models, together with the engine modelling techniques developed in this study, represent a novel and valuable contribution to the field of HCCI engine combustion control and effectively move this technology one incremental step closer to its anticipated commercial realisation.
  • Thumbnail Image
    Item
    Open Access
    Understanding HCCI characteristics in mini-HCCI engines
    (2008) Collair, Kyle; Floweday, Gareth; Yates, Andy
    This study examines the successful use of Homogeneous-Charge, Compression-Ignition (HCCI) combustion in a standard issue model-aero “diesel” engine. This two-stroke engine, unlike the more common glow-plug versions, operates without any form of combustion initiator. The fuel and air are premixed using a simple carburettor and ignited by piston compression only. The engine therefore operates in HCCI-mode even though it is referred to as a “model diesel engine”. Of particular interest is the fact that the engine is easily started from cold, warm and hot conditions. It runs stably from idle to over 11000rpm and is shown to run at high load points across the speed range with extremely conservative pressure rise rates. Furthermore, this engine is shown not to exhibit any knocking (high pressure oscillations) within its normal range of operation. The speed-load operational envelope of the engine is mapped out using a range of propellers and a propeller speed-load calibration rig. Air/fuel ratio, inlet air and exhaust gas temperatures are examined within this operational envelope. Areas of unstable operation and extremities in stable operation are also mapped out and discussed. The engine’s use of inlet throttling, crankcase pumping and residual exhaust gas metering is modelled and discussed. In addition, the engine’s inherent ability to maintain constant combustion phasing over varying operating conditions is also investigated.