Studies of Jet Thermal Stability in a Flowing System

A flowing, single-pass heat exchanger test rig, with a fuel capacity of 189 litres, has been developed to evaluate jet fuel thermal stability. This so called, “Phoenix Rig” is capable of supplying jet fuel to a 2.15 mm I.D. tube at a pressure up to 3.45 MPa, fuel temperature up to 900K, and a fuel-tube Reynolds number in the range 300–11,000. Using this test rig, fuel thermal stability (carbon deposition rate), dissolved oxygen consumption, and methane production were measured for three baseline jet fuels and three fuels blended with additives. Such measurement were performed under oxygen-saturation or oxygen-starved conditions. Tests with all of the blended fuel samples showed a noticeable improvement in fuel thermal stability. Both block temperature and test duration increased the total carbon deposits in a nonlinear fashion. Interestingly, those fuels that need a higher threshold temperature to force the consumption of oxygen exhibited greater carbon deposits than those that consume oxygen at a lower temperature. These observations suggested a complicated relationship between the formation of carbon deposits and the temperature-driven consumption of oxygen. A simple analysis, based on a bi-molecular reaction rate, correctly accounted for the shape of the oxygen consumption curve for various fuels. This analysis yielded estimates of global bulk parameters of oxygen consumption. The test rig yielded quantitative results which will be very useful in evaluating fuel additives, understanding the chemistry of deposit formation, and eventually developing a global chemistry model.

Combined Closed Cycle (C3) Systems for Underwater Power Generation

In this paper three Closed Combined Cycle (C3) systems for underwater power generation are analyzed. In the first, the waste heat rejected by a Closed Brayton Cycle (CBC) is utilized to heat the working fluid of a bottoming Rankine Cycle; in the second, the heat of a primary energy loop fluid is used to heat both CBC and Rankine cycle working fluids; the third solution involves a Metal Rankine Cycle (MRC) combined with an Organic Rankine Cycle (ORC). The significant benefits of the Closed Combined Cycle concepts, compared to the simple CBC system, such as efficiency increase and specific mass reduction, are presented and discussed. A comparison between the three C3 power plants is presented taking into account the technological maturity of all the plant components.

Engine Testing of a Prototype Low NOx Gas Turbine Combustor

The design of a lean-premixed, annular, dry low NOx combustor for Solar’s 5500 hp Centaur Type H gas turbine is discussed. Results from early engine tests of prototype combustion hardware are presented. The emissions results with natural gas fueling meet the development goals of less than 25 ppm NOx (at 15% O2) and 50 ppm CO. Several techniques to extend the low emissions operating range of the lean-premixed system are shown to be effective.

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.

What Affects the Cost of Hot Gas Filter Stations?

This technical paper examines the various aspects of hot gas filter station design which ultimately affect both initial and operational costs. Process conditions such as temperature and pressure, and design constraints such as face velocity are discussed with respect to their bearing on filter station costs. More subtle parameters such as pulse gas cleaning requirements and filter element geometry also directly impact filter design and hence, cost. As all of the information presented is based upon actual filter applications, it will provide useful insight for those involved in filter designing and recommendations.

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.

Low NOx Combustor for Automotive Ceramic Gas Turbine: II — Reliability Assurance

Two aspects of reliability assurance are discussed. First, This paper deals with the reliability design of the emissions under transient conditions. The optimization was made from the simulation results of the relationship between the response of the variable combustor geometry to follow load changes and the resulting exhaust emission levels. The load variation pattern used in this investigation was that of the Japanese 10-mode regulation. Second, this paper describes the validity of the reliability design prepared for the ceramic liner of the combustor. A service life prediction was made for the liner on the basis of stress analysis results and fatigue parameters.

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.