This last decade experienced a sudden increase of interest in the control of thermo-acoustic instabilities, in particular through the use of fuel modulation techniques. The primary goal of this research was to design, construct and characterize a high bandwidth proportional fuel injection system, which could be used to study the effect of specific levels of fuel modulation on the combustion process and the reduction of thermo-acoustic instabilities. A fuel injection system, incorporating the use of a closed loop piston and check valve, was designed to modulate the primary fuel supply of an atmospheric liquid-fueled swirl stabilized combustor operating at a mean volumetric fuel flow rate of 0.4 GPH. The ability of the fuel injection system to modulate the fuel was examined by measuring the fuel line pressure and the flow rate produced during operation. The authority of this modulation over the combustion process was investigated by examining the effect of fuel modulation on the combustor pressure and the heat release of the flame. Sinusoidal operation of the fuel injection system demonstrated: a bandwidth greater that 800 Hz, significant open loop authority (averaging 12 dB) with regards to the combustor pressure, significant open loop authority (averaging 33 dB) with regards to the unsteady heat release rate and an approximate 8 dB reduction of the combustor pressure oscillation present at 100 Hz, using a phase shift controller. It is possible to scale the closed loop piston and check valve configuration used to create the fuel injection system discussed in this work to realistic combustor operating conditions for further active combustion control studies. / Master of Science

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: There is a need for a coarse-to-fine positioning system as per a case study presented by the project collaboration partner, the Technical University of Chemnitz. The case study involves the picking and placing of piezo-ceramic micro parts into milled micro cavities. The focus of the project is the creation and development of a systematic approach for the design and the implementation of a coarse-to-fine positioning system for micro material handling. A second focus is to determine the applicability of the system for highly accurate and repeatable micro drilling and micro-milling. A systematic approach entails combining innovation management (assists in overall project structure), systems engineering (assists in specific design steps and tools) and research questions. Micro-milling was achieved, however the system proved unsuitable for highly accurate and repeatable micro drilling. The coarse-to-fine positioning system was successfully designed, built, and tested for accurate micro material handling. / AFRIKAANSE OPSOMMING: Daar bestaan ’n behoefte aan ’n grof-tot-fyn-posisioneringstelsel - soos blyk uit die gevallestudie uiteengesit deur die samewerkende projekvennoot, die Tegniese Universiteit van Chemnitz. Die gevallestudie behels die uitsoek en plasing van piezo-keramiek partikels in gefreesde mikroholtes. Hierdie projek het gefokus op die skepping en ontwikkeling van ’n stelselmatige benadering tot die ontwerp en implementering van ’n grof-tot-fyn-posisioneringstelsel vir mikromateriaalhantering en mikromasjienering. ’n Stelselmatige benadering behels dat innovasiebestuur (hulp met die algehele projekstruktuur), stelselingenieurswese (hulp met spesifieke ontwerpstappe en -hulpmiddels) en navorsingsdoelwitte gekombineer word. Die geïmplementeerde stelsel is eksperimenteel getoets en daar is bevind dat dit aan die spesifikasies en vereistes voldoen.