The main focus of this investigation was to get a greater understanding of the effect of combustion frequency, positive pressure amplitude, relative air:fuel ratio (A), water jacket temperature and input firing rates on the emissions of NO from pulse combustors. This study was carried out by a programme of experimental work combined with the development of a one-dimensional model. Results obtained in this study from experimental measurement, revealed evidence that a Schmidt tube has the ability to operate over a wide range of parameters (such as operating frequency, positive pressure amplitude, relative air:fuel ratio, water jacket temperature and input firing rates) with variable NO emissions. It was found that the level of NO emissions became lower with increasing operating frequency and positive pressure amplitude. As an example, when the rig was operated at input firing rate 25 kW and a positive pressure amplitude of 0.12 bar, increasing the frequency from 35 Hz to 73 Hz produced a monotonic reduction in NO emissions from 61 ppm to 29 ppm (dry, 3% O2). An'increase in positive pressure amplitude from 0.05 to 0.12 bar produced a change in NO emissions from 46 ppm to 34 ppm. It was also found that the values of NO emissions fell. with increasing excess air for A> 1.1. However, NO emissions increased with increasing water jacket temperature (Tw) along the length of tail pipe and with increasing input firing rates. Experimental results showed that the positive pressure amplitude was not dependent on the wall jacket temperature. However, the operating range of stable pressure oscillation could be extended from [...continued].

Thermoacoustic engines convert thermal energy into acoustic energy with few or no moving parts, thus they require little maintenance, are highly reliable, and are inexpensive to produce. These traits make them attractive for applications in remote or portable power generation, where a linear alternator converts the acoustic power into electric power. Their primary application, however, is in driving thermoacoustic refrigerators, which use acoustic power to provide cooling at potentially cryogenic temperatures, also without moving parts. This dissertation examines the feasibility of a new type of thermoacoustic engine, where mean flow and an internal pulse combustion process replace the hot heat exchanger in a traditional closed cycle thermoacoustic engine, thereby eliminating the heat exchangers cost, inefficiency, and thermal expansion stresses. The theory developed in this work reveals that a large temperature difference must exist between the hot face of the regenerator and the hot combustion products flowing into it, and that much of the convective thermal energy input from the combustion process is converted into conductive and thermoacoustic losses in the regenerator. The development of the Thermoacoustic Pulse Combustion Engine, as described in this study, is designed to recover most of this lost thermal energy by routing the inlet pipes through the regenerator to preheat the combustion reactants. Further, the developed theory shows that the pulse combustion process has the potential to add up to 7% to the engines acoustic power output for an acoustic pressure ratio of 10%, with linearly increasing contributions for increasing acoustic pressure ratios. Computational modeling and optimization of the Thermoacoustic Pulse Combustion Engine yield thermal efficiencies of about 20% for atmospheric mean operating pressures, though higher mean engine pressures increase this efficiency considerably by increasing the acoustic power density relative to the thermal losses. However, permissible mean engine pressures are limited by the need to avoid fouling the regenerator with condensation of water vapor out of the cold combustion products. Despite lower acoustic power densities, the Thermoacoustic Pulse Combustion Engine is shown to be well suited to portable refrigeration and power generation applications, due to its reasonable efficiency and inherent simplicity and compactness.

Current research shows that pulse combustion impingement drying is an improvement over the steady impingement drying currently in commercial use. Pulse combustion impingement has higher heat transfer rates and a lower impact on the environment. Commercialization of pulse impingement drying is the goal of the Pulsed Air Drying group at IPST. To that end the objective of this project is to develop a system that will allow researchers to measure heat transfer rates at the impingement surface from the impinging air. A water cooled impingement plate with temperature and heat flux measuring capabilities was developed which accurately measures and records the desired information. The impingement plate was tested and its results were verified by comparison with previous literature. Finally a preliminary comparison between steady and pulse combustion impingement was carried out. The study shows pulsed combustion impingement to be superior to steady impingement.

The gas turbine engine is an integral component of the global energy infrastructure and, through widespread use, contributes significantly to the emission of harmful pollutants and greenhouse gases. As such, the research and industrial community have a significant interest in improving the thermal efficiency of these devices. However, after nearly a century of development, modern gas turbine technology is nearing its realizable efficiency limit. Thus, using conventional approaches, including increased compression ratios and turbine inlet temperatures, only small future efficiency gains are available at a high cost. If a significant increase in gas turbine engine efficiency is to be realized, a deviation from this convention is necessary. Pressure gain combustion is a new combustion technology capable of delivering a step increase in gas turbine efficiency by replacing the isobaric combustor found in conventional engines with an isochoric combustor. This modification to the engine's thermodynamic cycle enables the loss in stagnation pressure typical of an isobaric combustor to be replaced with an overall net gain in stagnation pressure across the heat addition process. In this work, a pressure gain combustion technology known as the resonant pulse combustor is studied experimentally and numerically to bridge the gap between lab-scale experiments and practical implementations. First, a functional novel active valve resonant pulse combustor was designed and prototyped, thereby demonstrating naturally aspirated resonant operation with an air inlet valve-driven at a fixed frequency. Then, a series of experimental and numerical studies were carried out to increase the pressure gain performance of the combustor, and the performance and applicability of the active valve resonant pulse combustor concept were then experimental demonstrated in atmospheric conditions with both gaseous and liquid hydrocarbon fuels. Finally, the improved active valve resonant pulse combustor's pressure gain and NOX emissions performance was characterized within a high-pressure shroud in a configuration applicable to gas turbine applications and with varied inlet pressures extending up to 3 bar. This study demonstrates the low NOX capability of the pulse combustor concept and provides insight into how the device's performance may scale with increasing inlet pressure, as would exist in a practical application.