Showing papers by "Thomas H. Fletcher published in 2011"

Coal Swelling Model for High Heating Rate Pyrolysis Applications

Abstract: Thermal swelling of coal during pyrolysis strongly influences combustion and gasification rates. Coal swelling is known to vary strongly with coal rank, heating rate, and total pressure. New experiments confirm and clarify previous observations that maximum swelling occurs for high-rank bituminous coals at heating rates slightly below 104 K/s. Advanced swelling models based on bubble physics yield good qualitative trends at low heating rates, but they fail to predict observed decreases in coal swelling as particle heating rates increase beyond 104 K/s. An empirical swelling correlation for computational fluid dynamics (CFD) applications that correctly describes experimentally observed trends with the heating rate is proposed. Model parameters were fit to data from the literature using a coal rank index based on the chemical structure of the coal. The correlation has a form that allows for calculation of shrinkage for lignites, increasing swelling ratios as rank increases from sub-bituminous to bituminous ...

The making of English cricket cultures: empire, globalization and (post) colonialism

Abstract: The aim of this article is to understand how English cricket cultures have been made, negotiated and, ultimately, resisted in the context of (post) colonialism. I draw upon research undertaken with...

Effect of Particle Size and Trench Configuration on Deposition From Fine Coal Flyash near Film Cooling Holes

Abstract: Particulate deposition experiments were performed in a turbine accelerated deposition facility to examine the effects of flyash particle size and trench configuration on deposits near film cooling holes. Deposition on two bare metal Inconel coupons was studied, with hole spacings (s/d) of 3.4 and 4.5. Two sizes of sub-bituminous coal ash particles were used, with mass mean diameter of 4 and 13 μm, respectively. The effect of a cooling trench at the exit of the cooling holes was also examined in this deposition facility. Experiments were performed at different angles of impaction. Particles were accelerated to a combustor exit flow Mach number of 0.25 and heated to 1183 °C before impinging on a target coupon. The particle loading in the 1-h tests was 160 ppmw. Blowing ratios were varied in these experiments from 0 to 4.0. Particle surface temperature maps were measured using two-color pyrometry based on RGB signals from a camera. Deposits generated from finer particles were observed to stick to the surface more tenaciously than larger particles. The capture efficiency measured for the small particles was lower than for the larger particles, especially at low blowing ratios. However, the finer particles exhibited a greater variation in deposition pattern as a function of hole spacing than seen with larger particles. The effect of trench configuration on deposition was examined by performing deposition tests with and without the trench for the same hole spacing and blowing ratio. The effects of trench configuration on capture efficiency, deposition pattern, and surface topography are reported. Deposition experiments at impingement angles from 45° to 15° showed changes in both deposit thickness and temperature. The trench increased cooling effectiveness, but did not change the particulate collection efficiency because the trench acted as a particulate collector.

The effects of wind on the flame characteristics of individual leaves

Abstract: Individual cuttings from five shrub species were burned over a flat-flame burner under wind conditions of 0.75–2.80 m s–1. Both live and dead cuttings were used. These included single leaves from broadleaf species as well as 3 to 5 cm-long branches from coniferous and small broadleaf species. Flame angles and flame lengths were determined by semi-automated measurements of video images. Additional data, such as times and temperatures corresponding to ignition, maximum flame height and burnout were determined using video and infrared images. Flame angles correlated linearly with wind velocity. They also correlated with the Froude number when either the flame length or flame height was used. Flame angles in individual leaf experiments were generally 50 to 70% less than flame angles derived from Froude number correlations reported in the literature for fuel-bed experiments. Although flame angles increased with fuel mass and moisture content, they were unaffected by fuel species. Flame lengths and flame heights decreased with moisture contents and wind speed but increased with mass. In most cases, samples burned with wind conditions ignited less quickly and at lower temperatures than samples burned without wind. Most samples contained moisture at the time of ignition. Results of this small-scale approach (e.g. using individual cuttings) apply to ignition of shrubs and to flame propagation in shrubs of low bulk density. This research is one of the few attempts to characterise single-leaf and small-branch combustion behaviour in wind and is crucial to the continued development of a semi-empirical shrub combustion model.

"Aye, but it were wasted on thee": Cricket, British Asians, ethnic identities, and the 'magical recovery of community'

Abstract: People in sport tend to possess rather jaded perceptions of its colour-blindness and thus, they are reluctant to confront the fact that, quite often racism is endemic. Yorkshire cricket in particular, has faced frequent accusations from minority ethnic communities of inveterate and institutionalised racism and territorial defensiveness. Drawing upon semi-structured interviews conducted with amateur white and British Asian cricketers, this paper examines the construction of regional identities in Yorkshire at a time when traditional myths and invented traditions of Yorkshire and 'Yorkshireness' are being deconstructed. This is conceptualised through a reading of John Clarke's 'magical recovery of community'. Although cricket has been multiracial for decades, I argue that some people's position as insiders is more straightforward than others. I present evidence to suggest that, regardless of being committed to Yorkshire and their 'Yorkshireness', white Yorkshire people may never fully accept British Asians as 'one of us'. Ideologically and practically, white Yorkshire people are engaged in constructing British Asians as anathema to Yorkshire culture. The paper concludes by advocating that, for sports cultures to be truly egalitarian, the ideology of sport itself has to change. True equality will only ever be achieved within a deracialised discourse that not only accepts difference, but embraces it.

Time-Dependent Deposition Characteristics of Fine Coal Fly Ash in a Laboratory Gas Turbine Environment

Abstract: Time-dependent deposition characteristics of fine coal flyash were measured in the Turbine Accelerated Deposition Facility (TADF) at Brigham Young University. Two samples of subbituminous coal fly ash, with mass mean diameters of 3 and 13 μm, were entrained in a hot gas flow with a gas temperature of 1250°C and Mach number of 0.25. A nickel base super alloy metal coupon approximately 0.3 cm thick was held in a hot particle-laden gas stream to simulate deposition in a gas turbine. Tests were conducted with deposition times of 20, 40, and 60 minutes. Capture efficiencies and surface roughness characteristics (e.g., Ra) were obtained at different times. Capture efficiency increased exponentially with time while Ra increased linearly with time. The increased deposition with time caused the surface temperature of the deposit to increase. The increased surface temperature caused more softening, increasing the propensity for impacting particles to stick to the surface. These data are important for improving models of deposition in turbines from syngas flows.Copyright © 2011 by ASME

Gasification Studies Task 4 Topical Report, Utah Clean Coal Program

Abstract: A key objective of the Task 4 activities has been to develop simulation tools to support development, troubleshooting and optimization of pressurized entrained-flow coal gasifiers. The overall gasifier models (Subtask 4.1) combine submodels for fluid flow (Subtask 4.2) and heat transfer (Subtask 4.3) with fundamental understanding of the chemical (Subtask 4.4) and physical (Subtask 4.5) processes that take place as coal particles are converted to synthesis gas and slag. However, it is important to be able to compare predictions from the models against data obtained from actual operating coal gasifiers, and Subtask 4.6 aims to provide an accessible, non-proprietary system, which can be operated over a wide range of conditions to provide well-characterized data for model validation.