Multi-Jet Annulus/Core-Flow Mixing—Experiments and Calculations

LDV measurements are reported of the flow-field associated with a single row of radially injected jets penetrating a core-tube flow. Emphasis is placed on the influence of small feed-annulus height on jet entry conditions and resulting trajectories and mixing patterns. Conditions of unstable jet behaviour, with strong vortex patterns in the jet holes, were observed for small annulus heights and high annulus velocities. Most measurements were however taken under stable conditions to allow the data to be used in a CFD validation exercise. Significant differences in the strength of backflow generated at jet impingement and in the turbulence field in the immediate hole vicinity were observed for different annulus height/core diameter ratios. These were accompanied by jet trajectory and annulus flow structure changes. Measurements of all 3 mean velocity components and associated normal stresses enabled the data to be utilised to assess a 3D CFD calculation incorporating a k-ε turbulence closure. The strength of forward and back flow generated at impingement was accurately predicted when the QUICK discretisation scheme was used. However, the size of upstream vortex was overpredicted. As expected using an eddy viscosity model the turbulence field at jet impingement and in the hole vicinity was not correctly reproduced. The turbulence generation in the flow approaching the hole was greatly overestimated by the turbulence model used.

Low CO2 Power Generation Options and Their Environmental Impact

The Global Warming R&D Programme at the Coal Research Establishment is evaluating options for removing CO2 from coal-fired power plant. The aim is to identify coal-based technologies with minimal emissions of CO2 as contingency planning in case the most pessimistic fears of warming are realised. Two promising options based on Integrated Gasification Combined Cycle have been identified, so far. One incorporates a conventional CO shift conversion step and a physical solvent scrubbing process to remove 90% of the CO2 and 99% of the H2S. The second approach is conceptual, using CO shift but also a membrane gas separator. The gas turbine would be fired with hydrogen in both cases. A discussion of the environmental impact of these schemes suggests that they would be very much cleaner than current technology using Pulverised Fuel combustion with Flue Gas Desulphurisation. CO2 disposal options and needs for future work are also discussed.

Circulator Design/Technology Evolution for Gas-Cooled Nuclear Reactors

The circulator is a key component in a gas-cooled nuclear power plant since it facilitates transfer of the reactor thermal energy (via the steam generator) to the electrical power conversion system. Circulator technology is well established and about 200 machines, which, in their simplest form, consist of an electrical motor driven compressor, have operated for many millions of hours worldwide in gas-cooled reactors. This paper covers the evolution of circulator design, technology and operating experience, with particular emphasis on how lessons learned over the last four decades (dominantly from the carbon dioxide cooled plants in the U.K.) are applicable to the helium cooled Modular High Temperature Gas-Cooled Reactor (MHTCR) which should see service in the U.S. at the turn of the next century. State-of-the-art technologies are covered in the areas of impeller selection, bearings, drive system, machine operation, and future trends are Identified.

Coal-Water Slurry Testing of an Industrial Gas Turbine

This paper describes the first test of an industrial gas turbine and low emissions combustion system on coal-water-slurry fuel. The engine and combustion system have been developed over the past five years as part of the Heat Engines program sponsored by the Morgantown Energy Technology Center of the U.S. Department of Energy (DOE). The engine is a modified Allison 501-K industrial gas turbine designed to produce 3.5 MW of electrical power when burning natural gas or distillate fuel. Full load power output increases to approximately 4.9 MW when burning coal-water slurry as a result of additional turbine mass flow rate. The engine has been modified to accept an external staged combustion system developed specifically for burning coal and low quality ash-bearing fuels. Combustion staging permits the control of NOx from fuel-bound nitrogen while simultaneously controlling CO emissions. Water injection freezes molten ash in the quench zone located between the rich and lean zones. The dry ash is removed from the hot gas stream by two parallel cyclone separators. This paper describes the engine and combustor system modifications required for running on coal and presents the emissions and turbine performance data from the coal-water slurry testing. Included is a discussion of hot gas path ash deposition and planned future work that will support the commercialization of coal-fired gas turbines.

The Influence of Coal Slurry Fuel Properties on the Performance of a Bench Scale Two-Stage Slagging Combustor

Fuel specifications for a coal-fueled industrial gas turbine are being determined through bench scale testing of a two-stage slagging combustor with coal water mixtures (CWM) possessing different properties. Twelve CWMs have been formulated with variations in coal loading, ash concentration, fuel additives, coal particle size, and coal type. The test combustor is operated at 7 bars with a 600 K air inlet temperature in a high pressure test facility. The two-stage slagging combustor (TSSC) features a rich burning, slagging primary zone and a lean secondary zone. Combustor performance is characterized by measurements of pollutant emissions, slag capture, particulate emissions, and coal utilization. The combustor has demonstrated a high degree of fuel property flexibility with performance remaining above goals in most tests. The properties of the CWMs and the test results are discussed.

Development of High Temperature High Pressure Filtration Technology

Advanced Ceramic Tube Filters (ACTF) have been developed by Asahi Glass Co., Ltd (AGC) using innovative concepts aimed at hot gas clean-up system feasible for large scale industrial processes. More than 25 ACTF units of pilot and demonstration scale have been installed to demonstrate its readiness for various industrial applications. Among these applications, pressurized fluidized bed combustion (PFBC) combined cycle power generation system is the one in which the largest market size is foreseen until the 21st century. In this paper, the latest status of the development and commercialization of ACTF as well as the principle, basic configuration and operation of the system are described.

Emissions Reduction by Varying the Swirler Airflow Split in Advanced Gas Turbine Combustors

A rich burn/quick mix/lean burn (RQL) combustor concept for reducing pollutant emissions is currently under investigation at the NASA Lewis Research Center (LeRC). A numerical study was performed to investigate the chemically reactive flow with liquid spray injection for the RQL combustor. The RQL combustor consists of an airblast atomizer fuel injector, a rich burn section, a converging connecting pipe, a quick mix zone, a diverging connecting pipe and a lean combustion zone. For computational efficiency, the combustor was split into two sub systems, i.e. the fuel nozzle/rich burn section and the quick mix/lean burn section. The current study investigates the effect of varying the mass flow rate split between the swirler passages for an equivalence ratio of 2.0 on fuel distribution, temperature distribution, and emissions for the fuel nozzle/rich burn section of an RQL combustor. The input conditions used in the study were chosen based on tests completed at LeRC. It is seen that optimizing these parameters can substantially improve combustor performance and reduce combustor emissions. The optimal mass flow rate split for reducing NOx emissions based on the numerical study was the same as found by experiment at LeRC.

Smart Monitoring for Compressor Stations

A major remaining way to improve operational effectiveness for compressor stations is by the combination of on-line monitoring and enhanced diagnostics which can be described by the general term ‘smart monitoring’. The introduction of smart monitoring techniques will allow unattended operation of equipment to a greater extent than has been possible so far with remote access to the monitoring and diagnostic information from remote field, maintenance, and gas control locations. On-site attendance by operating and maintenance personnel can then be limited to responding to unscheduled events and for doing routine and scheduled maintenance. The role of enhanced diagnostics in this context is to anticipate undesirable operating conditions (and possibly mitigate or avoid them by certain control actions), to obtain earlier prediction of equipment deterioration or potential failures, to carry out a detailed analysis of unscheduled events and shutdowns, and to enable a high level of on-condition maintenance. The function of the intelligent diagnostics is to convert monitoring data, which can be voluminous with online monitoring, into a reduced subset of relevant information which is needed to make decisions. In this paper, a conceptual approach to smart monitoring is described and initial results of an on-site prototype are presented. Future implementation issues are also discussed.

Turbocompressor Antisurge Control, New Solution for an Old Problem

The performance of many antisurge control systems is degraded because they do not adequately compensate for variable gas properties (primarily molecular weight). The consequences can range from inefficient operation to serious compressor damage due to surges. To eliminate deficiencies previously experienced, a new, relatively simple (requires measuring only three process variables) system was developed for a machine which normally compresses a 24.2 molecular weight gas, but is also required to operate on other gas mixtures of approximately 40% lower molecular weight. The new method is explained and the results compared with two other widely used concepts.

Modification of Combustor Stoichiometry Distribution for Reduced NOx Emission From Aircraft Engines

Measurements of the emissions from an experimental engine were analyzed to construct a design chart for the reduction of oxides of nitrogen (NOx) in conventional combustors. The design chart was used to reconfigure the stoichiometry distribution of the combustor of a production engine so as to reduce NOx while holding the emissions of carbon monoxide, unburned hydrocarbons and smoke well below existing regulations. Combustion section pressure loss and combustor outlet temperature distributions were substantially unchanged. The modified design was refined with the aid of computational fluid dynamics calculations to optimize the emissions reduction. Worthwhile reductions in NOx were obtained with combustor modifications that are transparent to the engine user.