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A lean-premixed advanced vortex combustor (AVC) has been developed and tested. The natural gas fueled AVC was tested at the U.S. Department of Energy's National Energy Technology Laboratory in Morgantown, WV All testing was performed at elevated pressures and inlet temperatures and at lean fuel-air ratios representative of industrial gas turbines. The improved AVC design exhibited simultaneous N[O.sub.x]/CO/unburned hydrocarbon (UHC) emissions of 4/4/0 ppmv (all emissions corrected to 15% [O.sub.2] dry). The design also achieved less than 3 ppmv N[O.sub.x] with combustion efficiencies in excess of 99.5%. The design demonstrated marked acoustic dynamic stability over a wide range of operating conditions, which potentially makes this approach significantly more attractive than other lean-premixed combustion approaches. In addition, the measured 1.75% pressure drop is significantly lower than conventional gas turbine combustors, which could translate into an overall gas turbine cycle efficiency improvement. The relatively high velocities and low pressure drop achievable with this technology make the AVC approach an attractive alternative for syngas fuel applications.

This paper describes the evaluation of an alternative combustion approach to achieve low emissions for a wide range of fuel types. This approach combines the potential advantages of a staged rich-burn, quick-mix, lean-burn (RQL) combustor with the revolutionary trapped vortex combustor (TVC) concept. Although RQL combustors have been proposed for low-Btu fuels, this paper considers the application of an RQL combustor for high-Btu natural gas applications. This paper will describe the RQL/TVC concept and experimental results conducted at 10 atm (1013 kPa or 147 psia) and an inlet-air temperature of 644 K (700[degrees]F). The results from a simple network reactor model using detailed kinetics are compared to the experimental observations. Neglecting mixing limitations, the simplified model suggests that N[O.sub.x] and CO performance below 10 parts per million could be achieved in an RQL approach. The CO levels predicted by the model are reasonably close to the experimental results over a wide range of operating conditions. The predicted N[O.sub.x] levels are reasonably close for some operating conditions; however, as the rich-stage equivalence ratio increases, the discrepancy between the experiment and the model increases. Mixing limitations are critical in any RQL combustor, and the mixing limitations for this RQL/TVC design are discussed. [DOI: 10.1115/1.1789152]

Recent advances in lean premix gas turbine combustion have focused primarily on increasing thermodynamic efficiency, reducing emissions, and minimizing combustion dynamics. The practical limitation on increasing efficiency at lower emissions is the onset of combustion instability, which is known to occur near the lean flammability limit. In a laboratory, environment there are many sensors available that provide the combustion engineer with adequate information about flame stability, but those sensors are generally too expensive or unreliable for widespread application in the field. As a consequence, engines must be commissioned in the field with adequate stability margin such that normally expected component wear, fuel quality, and environmental conditions will not cause the turbine to experience unstable combustion. Woodward Industrial Controls, in cooperation with the National Energy Technology Laboratory, is developing a novel combustion sensor that is integrated into the fuel nozzle such that low cost and long life are achieved. The sensor monitors flame ionization, which is indicative of air-fuel ratio and most importantly flame stability. [DOI: 10.1115/1.1788686]

In this paper, we present and discuss some circuit experiments that verify our previous claims, which were based on numerical simulations of mathematical models, that chaos can be used to broaden the capture range of the common phase-locked loop circuit.