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Two nominally 15, and 30 kW Helmholtz-type pulsed combustors were designed and constructed. These were bench mounted with the heat exchangers (i.e. combustion chamber and tailpipe) immersed in the water bath. Their design was based upon the design of a nominally 7.5 kW pulsed unit previously developed at Middlesex University. The design enabled the lengths of the combustion chambers to be varied so that various combustion chamber volumes could be achieved. This provided a new dimension to the study of pulsed combustors which is lacking in many reported works. It was found that the required input rates could be achieved by scaling up or down each combustion chamber dimensions linearly by a factor of 1.5, while maintaining the geometry identical. Tests showed that the present design of pulsed combustors can operate successfully at various input rates of mains natural gas (93 % methane) with a maximum turn-down ratio of 1.8:1. Results indicated that the three developed combustors would generally operate in the fuel-lean condition. Interestingly, these tests revealed that the amount of excess air reduced as the combustion chamber volume (CCV) was increased. Systematic investigation on the three developed combustors showed that the temperature within the combustor was principally controlled by the air-to-fuel ratio (A/F). Analysis of the average measured NOx concentrations at various operating conditions indicated that NOx emission in this type of pulsed combustor is principally controlled by combustion temperature with no significant influence of combustion chamber volume, tailpipe length or scale of the combustors except in so far as these influenced the A/F and hence the temperature within the combustor. The dominant role of temperature on NOx production from these combustors become more evident when nitrogen or argon was injected into the system resulting in reduced NOx emissions at a given A/F. Systematic analysis of data indicated that as the amount of diluent increased, the temperature within the combustor decreased. Almost all the NOx values recorded were in the form of NO which is believed to be as a result of the high flame temperature (typically above 1850K). The minimum recorded NOx value was 5 ppm at the upper limiting value of excess air ratio, λ ; importantly it was round that at these high A/F values there was no significant reduction in overall efficiency of the pulsed units, showing calculated values above 90%. Analysis of data indicated that combustion temperature is also a primary factor controlling CO emissions from the present design of pulsed combustors. CO concentrations exhibited U-shaped characteristics when plotted vs λ, showing maximum values at the lowest and highest λ values. By changing water bath temperature (WBT) and hence modifying heat losses to the combustion chamber wall, it was shown that the quenching of the combustion reactions and incomplete mixing of air and gas prior to combustion are contributing factors to CO formation in this type of pulsed combustor. The developed pulsed combustors were operated successfully with standard test gases. The composition and flame stability of these test gases were similar to the standard test gases G21 (incomplete combustion gas), G222 (light back gas) and G23 (flame lift gas). Analysis of the exhaust gas composition showed similar trends to those obtained when burning mains natural gas; as the heat input was increased, O2 levels decreased while CO2 and NOx emission levels increased. Similarly, CO concentrations showed U-shaped characteristics when plotted against firing rate. Measurements of peak pulsing pressure and frequency were used as a guide to operation and stability performance of the pulsed units. It was found that the operating frequency was a function of configuration of the combustors and temperature of the internal gases. Frequency of operation showed a reciprocal correlation with volume of combustion chamber and tailpipe length and increased as the heat input was increased. Pulsing pressure amplitude also was influenced by change of configuration of the combustors, increasing as the CCV and tailpipe length were decreased. Analysis of experimental data obtained at fixed configuration of the combustors showed that the peak pulsing pressure was a strong function of the heat release per cycle in the present design of pulsed combustors. A major drawback of the use of pulsating combustors is the high noise level which is associated with their operation. It was found that it is possible to reduce overall noise levels of the pulsed burners to acceptable values by configuring the system appropriately. This included the use of expansion chambers at the inlet and the exhaust outlet which reduced the overall noise levels to a minimum value of 65 dBA.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 246-257).

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Ronald D. Matthews. Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--University of Wisconsin--Madison, 1915. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 69-71).

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xiii, 160 p.; also includes graphics (some col.). Includes bibliographical references (p. 156-160). Available online via OhioLINK's ETD Center

Alcohol fuels are expected to become an economic/strategic alternative to oil over the next decade as oil reserves are depleted and countries seek to become more energy self-sufficient. Methanol, produced from natural gas deposits, and ethanol, produced locally by distillation of biomass, offer easily transportable alternatives. The use of a wider range of fuels in spark-ignition engines and the quest for fuel economy whilst meeting exhaust emissions legislation are important issues in engine design. The performance of current and proposed combustion chamber designs needs to be assessed with lean mixtures of both conventional and alternative fuels. The parameters defining combustion chamber performance, initial flame development and cycle-to-cycle variations in combustion may be readily determined using computer in-cylinder combustion models in a diagnostic manner to reduce experimentally acquired cylinder pressure data. This thesis develops and applies two analysis techniques to the study of the combustion of methanol in the lean burning regime with experimental results from three engines. The pressure increment technique, in which the pressure rise owing to combustion at constant volume is computed, is suitable for use directly on microcomputer systems. The two-zone equilibrium theory model, in which the mass burnt to give the measured pressure rise is evaluated, provides a more comprehensive analysis but is demanding in computer power. Higher burning rates were achieved using highly turbulent combustion chambers with methanol and equivalence ratios could be leaned to about 0.8 before cycle-to-cycle variations in combustion limited stable operation. The results obtained indicated the significant phases of initial flame development, the influence of early flame development on subsequent burning rates, and the influence of differing chamber geometries on performance. The combustion process was modelled for use in parametric studies of engine performance based on empirical data.

A brief introduction to the field of pyrotechnic time delays is given, followed by a survey of the published work in the field up to the present time. A description is provided of the experimental techniques, equipment and materials used. The energetics and mechanism of reaction in the boron/lead monoxide and boron/stannic oxide systems have been investigated by comparison with the more familiar, analogous silicon fuelled systems; the emphasis being placed on the boron/lead monoxide system. The heats of reaction of the four fuel/oxidant systems have been measured by the use of bomb calorimetry, the results being discussed in relation to the probable reactions taking place in each system. Conclusions have been drawn as to the nature of the reactions which provide heat outputs in excess of the theoretical values in the boron fuelled systems. The propagation rates of the four fuel/oxidant systems have been measured and the relationship between heat output and propagation rate in each system is discussed. An explanation is proposed for the apparently anomalous behaviour of the boron fuelled systems. The response of the propagation rates in each system to varying consolidation pressure has been investigated. An explanation is proposed for the difference in behaviour displayed by the boron and silicon fuelled systems. A method of non-contact temperature measurement using a recording infra-red brightness pyrometer has been investigated. The reaction temperatures of the four fuel/oxidant systems have been measured and their relationships to the response of the propagation rates of each system to consolidation pressure variations are discussed. The boron/lead monoxide reaction in loose powder mixes has been investigated using differential scanning calorimetry. Hot stage microscopy has been used to investigate boron/lead monoxide reactions in loose powder mixes and between consolidated pellets of the individual reactants. The thermal analysis results obtained demonstrate the effect of the boron oxidation product, B 2 0 3 , on the reaction rate and the role which it plays in the reaction mechanism in the boron/lead monoxide system. A reaction mechanism is proposed for the non-propagative reaction between boron and lead monoxide. The extraction and kinetic analysis of data from the differential scanning calorimetry investigation of the boron/lead monoxide system is discussed. It is demonstrated that the analysis of the dynamic data is virtually impossible due to the complexity of the peak patterns obtained.

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No description available.