In the rally car racing there is a need for maximum power throughout the race. While this is not possible through the entire engine speed range, it is possible to manipulate the engine speed at which maximum power is obtained by changing the engine configuration. One of the most effective ways to do this is to modify the intake system to allow for more air into the engine, thus allowing for more fuel to be burnt and more power to be obtained. This dissertation focused on improving the inlet system of a high-performance rally car race engine by using computational fluid dynamics (CFD) and mathematical optimisation techniques, the combination of which is called a computational flow optimisation (CFO) system. Historically, designers have been aware of the importance of proper intake design and with improving technology and a better understating of wave theory, as applied to manifold flow, development moved at fast pace. The application of wave theory to intakes led to a more academic approach to engine tuning, where mathematical relationships were developed to describe the influence of certain engine parameters on air intake. Numerical methods used to solve for flow in intake systems have also developed due to the advances in computer capabilities and are used in the study in the form of CFD and 1-D gas dynamics (as implemented in the engine simulation code used in the study, namely EngMod4T). These are combined with optimisation to arrive at an improved design. The CFD simulations are transient in nature in order to capture the pulse interactions and their influence on the mass of air inducted by the intakes. The first case considered is that of a single intake exposed to atmosphere. To relate the results of the single intake simulation to a full-intake simulation, the mass of inducted air is assumed to be equal for all four intakes. This assumption was found to be flawed as shown by the simulation that followed that took into consideration all four intakes also open to atmosphere. The simulation showed that the intakes actually induct differing amounts of air and the total amount is less than for four single trumpets. A more comprehensive simulation was conducted where the airbox was included and the resulting total mass inducted showed that even less air is inducted by this setup. The results of the latter were used as the basis of the optimisation study that followed. Various airbox designs, obtained from the optimisation software LS-OPT, were simulated and resulted in an improved airbox design that inducts 6.2% more air than the original airbox. And since there is direct relationship between mass of air inducted and engine power produced, it is expected that the engine power would also increase by 6.2%. The study demonstrates the successful implementation of a CFO system to solve a complex industrial flow problem. With the increase of computing power and increasing affordability of such systems coupled with the ease-of-use of commercial CFD software, CFO should become more common in industrial application. / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2007. / Mechanical and Aeronautical Engineering / unrestricted

The demand for higher quality steel and higher production rates in the production of steel slabs is ever increasing. These slabs are produced using a continuous casting process. The molten steel flow patterns inside the components of the caster play an important role in the quality of these products. A simple yet effective design method that yields optimum designs is required to design the systems influencing the flow patterns in the caster. The tundish is one of these systems. Traditionally, experimental methods were used in the design of these tundishes, making use of plant trials or water modelling. These methods are both costly and time consuming. More recently, Computational Fluid Dynamics (CFD) has established itself as a viable alternative to reduce the number of experimentation required, resulting in a reduction in the time scales and cost of the design process. Furthermore, CFD provides more insight into the flow process that is not available through experimentation only. The CFD process is usually based on a trial-and-error basis and relies heavily on the insight and experience of the designer to improve designs. Even an experienced designer will only be able to improve the design and does not necessarily guarantee optimum results. In this thesis, a more efficient design methodology is proposed. This methodology involves the combination of a mathematical optimiser with CFD to automate the design process. The methodology is tested on a four different industrial test cases. The first case involves the optimisation of a simple dam-weir configuration of a single strand caster. The position of the dam and weir relative to inlet region is optimised to reduce the dead volume and increase the inclusion removal. The second case involves the optimisation of a pouring box and baffle of a two-strand caster. In this case, the pouring box and baffle geometry is optimised to maximise the minimum residence time at operating level and a typical transition level. The third case deals with the geometry optimisation of an impact pad to reduce the surface turbulence that should result in a reduction in the particle entrainment from the slag layer. The last case continues from the third case where a dam position and height is optimised in conjunction with the optimised impact pad to maximise the inclusion removal on the slag layer. The cases studies show that a mathematical optimiser combined with CFD is a superior alternative compared to traditional design methods, in that it yields optimum designs for a tundish in a continuous casting system. / Thesis (PhD (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted