Active Control Application to a Model Gas Turbine Combustor

Closed-loop feedback control, developed in a axisymmetric can combustor, is demonstrated in a model can combustor with discrete wall jets. The study represents the initial steps toward the application of feedback control technology to practical gas turbine combustion systems. For the present application, the radiative flux from soot particulate is used as an indication of combustor performance, and nozzle atomizing air is selected as the input parameter. A measurement of radiative flux at the exit plane of the combustor is conveyed to a control computer which invokes an optimization algorithm to determine changes in the dome region necessary to minimize the radiative flux from soot. The results demonstrate the utility and potential of active control for maintaining optimal performance in real-time.

Potential Applications of Structural Ceramic Composites in Gas Turbines

A Babcock and Wilcox - Solar Turbines Team has completed a program to assess the potential for structural ceramic composites in turbines for direct coal-fired or coal gasification environments. A review is made of the existing processes in direct coal firing, pressurized fluid bed combustors, and coal gasification combined cycle systems. Material requirements in these areas were also discussed. The program examined the state-of-the-art in ceramic composite materials. Utilization of ceramic composites in the turbine rotor blades and nozzle vanes would provide the most benefit. A research program designed to introduce ceramic composite components to these turbines was recommended.

Evaluation of a Catalytic Combustor in a Gas Turbine-Generator Unit

As a final step of the Catalytic Combustor Development Program, a catalytic combustor developed was tested in a 150-kW gas turbine-generator unit. A digital control system was developed to improve its controllability for a transient operation, and a 200-hr continuous operation test was performed to asses the durability of the catalyst. During the test, an excellent performance of the control system was verified, and a very high combustion efficiency of more than 99% and a ultra-low NOx level of less than 5.6 ppm (at 15% O2) were achieved at a 150-kW generator output. In addition, the combustion efficiency has been maintained at over 98% for 200 hours of operation. However, the catalyst exposed to 200 hours of operation showed signs of deactivation.

The Particle-Wall, Normal-Impact Collision Coefficient in the Presence of a Liquid Film

The turbine blades of Gas Turbines operating with “dirty” fuels are sometimes covered by a very thin liquid film, which originates from the condensation of the alkalic sulfates (mainly) in the flue gases. These films may influence drastically the collision coefficient of the impinging (ash) particles. This, in turn, influences the future trajectories of these particles and their adhesive properties, especially in the rotor blades where the Coriolis aceleration becomes a significant factor in the particle kinetic energy absorption process. The study reports on the capture film height and the variation of the collision coefficient with the film height. The experimental conditions correspond to those encountered in rotor blades, where the surface tension, the wave-making process and the boyancy all contribute to this energy absorption. The results indicate that the model based on the interaction of these factors gives a goodexplanation of the energy absorption process, except for the very thin height where particle apparent mass effects dominate the process.

A GCC Power Plant With Methanol Storage for Intermediate-Load Duty

This paper describes the design and performance of a coal gasification combined-cycle power plant with an integrated facility for producing and storing methanol (GCC/methanol power plant). The methanol is produced at a steady rate and is burned in the combined-cycle to generate additional power during periods of peak electrical demand. The GCC/methanol plant provides electricity generation and energy storage in one coal-based facility. It is of potential interest to electric utilities seeking to meet intermediate-load electrical demand on their systems. The plant configuration is determined by means of an economic screening study considering capital and fuel costs over a range of cycling duties (load factors). Estimated levelized electricity production costs indicate that a GCC/methanol plant could be of economic interest as premium fuel prices increase relative to coal. The plant could potentially be of interest for meeting daily peak demands for periods of eight hours or less. The conceptual plant configuration employs a Texaco gasifier and a Lurgi methanol synthesis plant. Plant performance is estimated at peak and baseload output levels. No unusual design or operational problems were identified.

Experimental Evaluation of Sorbents for Sulfur Control in a Coal-Fueled Gas Turbine Slagging Combustor

A slagging combustor has been used to evaluate three calcium-based sorbents for sulfur capture efficiency in order to assess their applicability for use in a coal-fueled gas turbine. Testing is completed in a bench-scale combustor with one-tenth the heat input needed for the full-scale gas turbine. The bench-scale rig is a two-staged combustor featuring a fuel rich primary zone and a fuel lean secondary zone. The combustor is operated at 6.5 bars with inlet air preheated to 600 K. Gas temperatures of 1840 K are generated in the primary zone and 1280 K in the secondary zone. Sorbents are fed in either the secondary zone or mixed with the coal water mixture and fed into the primary zone. Dry powdered sorbents are fed into the secondary zone by an auger into one of six secondary air inlet ports. The three sorbents tested in the secondary zone include dolomite, pressure hydrated dolomitic lime, and hydrated lime. Sorbents have been tested while burning coal water mixtures with coal sulfur loadings of 0.56 to 3.13 weight percent sulfur. Sorbents are injected into the secondary zone at varying flow rates such that the calcium/sulfur ratio varies from 0.5 to 10.0. Hydrated lime exhibits the highest sulfur dioxide reductions in the exhaust of 90%. Pressure hydrated dolomitic lime and dolomite reduce SO2 concentrations by 82% and 55%, respectively. Coal sulfur loading is found to have a small influence on sorbent sulfur capture efficiency. Pressure hydrated dolomitic lime ground with the coal during coal water mixture preparation and injected into the primary zone is found to lower the sulfur dioxide concentration by an insignificant amount.

Coal Mineral Matter Transformation During Combustion and its Implications for Gas Turbine Blade Erosion

The transformation of mineral matter during combustion and the characteristics of the ash formed are important from the standpoint of coal fired gas turbine operation. Using a novel FT-IR technique and EDX analysis, these mineral matter transformations are investigated when the coal is burnt in a one-dimensional pulverized coal-dust-air flame. The role of clays, pyrite, quartz, potassium and other compounds in the ash are discussed with particular reference to deposit buildup and erosion of gas turbine blades.

An Experimental Study of the Effects of Liquid Properties on the Breakup of a Two-Dimensional Liquid Sheet

The breakup of a liquid sheet is of fundamental interest in the atomization of liquid fuels. The present study explores the breakup of a two-dimensional liquid sheet in the presence of co-flow air with emphasis on the extent to which liquid properties affect breakup. Three liquids, selected with varying values of viscosity and surface tension, are introduced through a twin-fluid, two-dimensional nozzle. A pulsed laser imaging system is used to determine the sheet structure at breakup, the distance and time to breakup, and the character of the ligaments and droplets formed. Experiments are conducted at two liquid flow rates with five flow rates of co-flowing air. Liquid properties affect the residence time required to initiate sheet breakup, and alter the time and length scales in the breakup mechanism.

Experimental Study of the Effect of Dense Spray on Drop Size Measurement by Light Scattering Technology

The effect of dense spray on drop size measurement by light scattering technology was studied by using Malvern instrument with five duplicated internal mixing airblast atomizers aligned in line with laser beam. The correction factor data for multiple scattering were obtained. By regression analysis, an empirical equation was obtained which correlated the correction factor as a function of obscuration (OBS), Sauter mean diameter under dilute spray condition SMD0. and drop size distribution parameter for Rosin–Rammler distribution under dilute spray conditions N0. The experimental data showed definitely that the correction factor is not only a function of OBS, SMD0, as proposed by Dodge, but also is a function of N0. The correlation fits the experimental data very well, and can be used for practical purposes to correct the data from Malvern drop sizer at high obscuration conditions.

The Influence of Air/Fuel Ratio and Swirl Number on the Combustion Characteristics of a Model Combustor

Combustion characteristics of a model can-type combustor are reported for air/fuel ratios encompassing take-off and ground-idle conditions and for two swirlers with gaseous fuel and at atmospheric pressure. Temperatures were obtained with fine-wire thermocouples, and concentrations of UHC, H2, CO, CO2, O2 sampled through a water-cooled probe with a flame ionization detector, a gas chromotograph and infrared and paramagnetic analyzers. The results indicate combustion efficiencies greater than 97%. For the air/fuel ratio corresponding to that of take-off, 45% of the mass flow of the primary jets turned upstream after impingement, combustion occurred in the wakes of the swirler and of the primary jets resulting in a pattern factor of 0.46. At ground-idle condition, 58% of the primary jet flow turned upstream reducing the pattern factor to 0.43. An 18% reduction in the swirl number at the ground-idle condition led to a pattern factor to 0.35 and, for takeoff, to a pattern factor of around 0.37 with combustion occurred mainly in the intermediate zone.