Optical and probe determination of soot concentrations in a model gas turbine combustor

An experimental program was conducted to track the variation in soot loading in a generic gas turbine combustor. The burner is a 12.7-cm dia cylindrical device consisting of six sheet-metal louvers. Determination of soot loading along the burner length is achieved by measurement at the exit of the combustor and then at upstream stations by sequential removal of liner louvers to shorten burner length. Alteration of the flow field approaching and within the shortened burners is minimized by bypassing flow in order to maintain a constant linear pressure drop. The burner exhaust flow is sampled at the burner centerline to determine soot mass concentration and smoke number. Characteristic particle size and number density, transmissivity of the exhaust flow, and local radiation from luminous soot particles in the exhaust are determined by optical techniques. Four test fuels are burned at three fuel-air ratios to determine fuel chemical property and flow temperature influences. Particulate concentration data indicate a strong oxidation mechanism in the combustor secondary zone, though the oxidation is significantly affected by flow temperature. Soot production is directly related to fuel smoke point

Investigation of soot and carbon formation in small gas turbine combustors

An investigation of hardware configurations which attempt to minimize carbon and soot-production without sacrificing performance in small gas turbine combustors was conducted. Four fuel injectors, employing either airblast atomization, pressure atomization, or fuel vaporization techniques were combined with nozzle air swirlers and injector sheaths. Eight configurations were screened at sea-level takeoff and idle test conditions. Selected configurations were focused upon in an attempt to quantify the influence of combustor pressure, inlet temperature, primary zone operation, and combustor loading on soot and carbon formation. Cycle tests were also performed. It was found that smoke emission levels depended on the combustor fluid mechanics, the atomization quality of the injector and the fuel hydrogen content

Aviation-fuel property effects on combustion

The fuel chemical property influence on a gas turbine combustor was studied using 25 test fuels. Fuel physical properties were de-emphasized by using fuel injectors which produce highly-atomized, and hence rapidly vaporizing sprays. A substantial fuel spray characterization effort was conducted to allow selection of nozzles which assured that such sprays were achieved for all fuels. The fuels were specified to cover the following wide ranges of chemical properties: hydrogen, 9.1 to 15 (wt) pct; total aromatics, 0 to 100 (vol) pct; and naphthalene, 0 to 30 (vol) pct. standard fuels (e.g., Jet A, JP4), speciality products (e.g., decalin, xylene tower bottoms) and special fuel blends were included. The latter group included six, 4-component blends prepared to achieve parametric variations in fuel hydrogen, total aromatics and naphthalene contents. The principle influences of fuel chemical properties on the combustor behavior were reflected by the radiation, liner temperature, and exhaust smoke number (or equivalently, soot number density) data. Test results indicated that naphthalene content strongly influenced the radiative heat load while parametric variations in total aromatics did not

Catalytic combustion with incompletely vaporized residual fuel

Catalytic combustion of fuel lean mixtures of incompletely vaporized residual fuel and air was investigated. The 7.6 cm diameter, graded cell reactor was constructed from zirconia spinel substrate and catalyzed with a noble metal catalyst. Streams of luminous particles exited the rector as a result of fuel deposition and carbonization on the substrate. Similar results were obtained with blends of No. 6 and No. 2 oil. Blends of shale residual oil and No. 2 oil resulted in stable operation. In shale oil blends the combustor performance degraded with a reduced degree of fuel vaporization. In tests performed with No. 2 oil a similar effect was observed

Combustion of coal gas fuels in a staged combustor

Gaseous fuels produced from coal resources generally have heating values much lower than natural gas; the low heating value could result in unstable or inefficient combustion. Coal gas fuels may contain ammonia which if oxidized in an uncontrolled manner could result in unacceptable nitrogen oxide exhaust emission levels. Previous investigations indicate that staged, rich-lean combustion represents a desirable approach to achieve stable, efficient, low nitrogen oxide emission operation for coal-derived liquid fuels contaning up to 0.8-wt pct nitrogen. An experimental program was conducted to determine whether this fuel tolerance can be extended to include coal-derived gaseous fuels. The results of tests with three nitrogen-free fuels having heating values of 100, 250, and 350 Btu/scf and a 250 Btu/scf heating value doped to contain 0.7 pct ammonia are presented

Rich burn combustor technology at Pratt and Whitney

The topics covered include the following: near term objectives; rich burn quick quench combustor (RBQC); RBQC critical technology areas; cylindrical RBQQ combustor rig; modular RBQQ combustor; cylindrical rig objectives; quench zone mixing; noneffusive cooled liner; variable geometry requirements; and sector combustor rig

Advanced Microturbine Systems

In July 2000, the United Technologies Research Center (UTRC) was one of five recipients of a US Department of Energy contract under the Advanced Microturbine System (AMS) program managed by the Office of Distributed Energy (DE). The AMS program resulted from several government-industry workshops that recognized that microturbine systems could play an important role in improving customer choice and value for electrical power. That is, the group believed that electrical power could be delivered to customers more efficiently and reliably than the grid if an effective distributed energy strategy was followed. Further, the production of this distributed power would be accomplished with less undesirable pollutants of nitric oxides (NOx) unburned hydrocarbons (UHC), and carbon monoxide (CO). In 2000, the electrical grid delivered energy to US customers at a national average of approximately 32% efficiency. This value reflects a wide range of powerplants, but is dominated by older, coal burning stations that provide approximately 50% of US electrical power. The grid efficiency is also affected by transmission and distribution (T&D) line losses that can be significant during peak power usage. In some locations this loss is estimated to be 15%. Load pockets can also be so constrained that sufficient power cannot be transmitted without requiring the installation of new wires. New T&D can be very expensive and challenging as it is often required in populated regions that do not want above ground wires. While historically grid reliability has satisfied most customers, increasing electronic transactions and the computer-controlled processes of the 'digital economy' demand higher reliability. For them, power outages can be very costly because of transaction, work-in-progress, or perishable commodity losses. Powerplants that produce the grid electrical power emit significant levels of undesirable NOx, UHC, and CO pollutants. The level of emission is quoted as either a technology metric or a system-output metric. A common form for the technology metric is in the units of PPM {at} 15% O2. In this case the metric reflects the molar fraction of the pollutant in the powerplant exhaust when corrected to a standard exhaust condition as containing 15% (molar) oxygen, assuring that the PPM concentrations are not altered by subsequent air addition or dilution. Since fuel combustion consumes oxygen, the output oxygen reference is equivalent to a fuel input reference. Hence, this technology metric reflects the moles of pollutant per mole of fuel input, but not the useful output of the powerplant-i.e. the power. The system-output metric does embrace the useful output and is often termed an output-based metric. A common form for the output-based metric is in the units of lb/MWh. This is a system metric relating the pounds of pollutant to output energy (e.g., MWh) of the powerplant

Summary of combustion instability research at Princeton University, 1969

Control and causes of combustion instability in rocket engine

Improvement of infrared single-photon detectors absorptance by integrated plasmonic structures

Plasmonic structures open novel avenues in photodetector development. Optimized illumination configurations are reported to improve p-polarized light absorptance in superconducting-nanowire single-photon detectors (SNSPDs) comprising short- and long-periodic niobium-nitride (NbN) stripe-patterns. In OC-SNSPDs consisting of ~quarter-wavelength dielectric layer closed by a gold reflector the highest absorptance is attainable at perpendicular incidence onto NbN patterns in P-orientation due to E-field concentration at the bottom of nano-cavities. In NCAI-SNSPDs integrated with nano-cavity-arrays consisting of vertical and horizontal gold segments off-axis illumination in S-orientation results in polar-angle-independent perfect absorptance via collective resonances in short-periodic design, while in long-periodic NCAI-SNSPDs grating-coupled surface waves promote EM-field transportation to the NbN stripes and result in local absorptance maxima. In NCDAI-SNSPDs integrated with nano-cavity-deflector-array consisting of longer vertical gold segments large absorptance maxima appear in 3p-periodic designs due to E-field enhancement via grating-coupled surface waves synchronized with the NbN stripes in S-orientation, which enable to compensate fill-factor-related retrogression.United States. Dept. of Energy (Frontier Research Centers