ACERC
Abstracts - 1997 |
ACERC
Abstracts - 1997 |
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Thrust Area 4: Turbulent Reacting Fluid Mechanics and Heat Transfer |
Cremer, M.A. and McMurtry,
P.A.
Propulsion and Power, (in press), 1997. Funded by ACERC and National
Science Foundation.
A one-dimensional stochastic turbulent mixing model is formulated for application to a constant diameter, cylindrical combustion geometry. Simulations are performed to study effects of turbulence and non-equilibrium chemistry on NO formation in a cylindrically confined H2-air jet. Effects of secondary air injectors, combustion tube diameter, flow rate, and equivalence ratio on NO formation are presented over a range of these parameters. It is illustrated that variations of these parameters can lead to reduced NO production by increasing the turbulence levels and through minimization of residence times in stoichiometric regions where NO production is greatest. Application of these results to the development of new burner concepts is addressed.
Guilkey, J.E.; Kerstein,
A.R.; McMurtry, P.A. and Klewicki, J.C.
Phys. Fluids, 9(3):717-23(1997). Funded by ACERC and National Science
Foundation.
An experimental investigation of passive scalar mixing in turbulent pipe flow is carried out using a new non-intrusive scalar initialization technique. The measurements support a recently predicted similarity scaling of concentration spectra in flows that are unbounded in one direction. Reflecting this scaling, the scalar variance exhibits a power-law rather than exponential decay, indicating that the traditional plug-flow reactor picture of turbulent pipe-flow mixing omits key physical mechanisms.
Guilkey, J.E.; Kerstein,
A.R.; McMurtry, P.A. and Klewicki, J.C.
Physical Review E, 56(2):1753-758(1997). Funded by ACERC and National
Science Foundation.
Exponential-tailed scalar probability density functions (PDF's) are obtained by high-pass filtering scalar concentration time series measured in turbulent pipe flow. This behavior reflects the scale separation of scalar and velocity fluctuations that develops in this flow, such that the low-wave-number scalar fluctuations act as and imposed scalar gradient stirred by finer-scale wall-generated shear. This observation broadens the class of flows in which long-tailed scalar PDF's are anticipated to occur.
Tree, D.R. and Webb, B.W.
Fuel, 76:1057-1066(1997). Funded by New York State Electric & Gas
Corp. and ACERC.
Gas temperature and effluent NOx measurements were obtained in a full-scale (160 MWe) pulverized coal corner-fired utility boiler with separate overfire air. The measurements are the first of this kind in a full-scale boiler operated with overfire air and low-NOx burners. A test matrix of seven operating conditions was used to compare temperature and NOx with changes in overfire air, coal type, load and burner tilt. Peak temperatures were 1500-1600°C and occurred just above the top burner. The measurements detailed the profile of temperature through a traverse of a coal burner, close-coupled overfire air port and separate overfire port. The data in the near-burner and overfire air regions showed evidence of reduced swirl as overfire air was increased. Little difference was seen in the temperatures for two coals with volatile fractions of 28 and 36 wt%. Temperature changes were quantified in the overfire air region for changes in burner tilt and load. Temperature was approximately the same in the overfire air region as load was decreased, but increased in this region as the burners were tilted from +5° to -5°.
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